Enantioselective Synthesis of Neocarzinostatin Chromophore Aglycone Citation Hammond, Marlys (1997) Enantioselective Synthesis of Neocarzinostatin Chromophore Aglycone. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/k6mz-nt82. https://resolver.caltech.edu/CaltechTHESIS:11012025-083054910 Abstract An enantioselective synthesis of neocarzinostatin chromophore aglycone (6) is described. The key features of the synthesis include 1) Sharpless asymmetric epoxidation of the allylic alcohol 136 to produce epoxy alcohol 137, 2) an intramolecular acetylide addition within the epoxy aldehyde 138 to furnish alcohol 139, 3) esterification of the diol 171 with the acid 22 and in situ cleavage of the chloroacetate ester to provide ester 172, 4) elimination of the C-1 alcohol of 175 to afford the olefin 176, and 5) reductive opening of epoxy alcohol 120 with the combination of iodine, triphenylphosphine, and imidazole to afford neocarzinostatin chromophore aglycone (6). The synthetic pathway described is highly convergent, and should the supply quantities of 6 necessary for ongoing studies directed toward the completion of the total synthesis of neocarzinostatin chromophore (1), as well as the preparation of analogs bearing modified sugar residues. Item Type: Thesis (Dissertation (Ph.D.)) Subject Keywords: (Chemistry) Degree Grantor: California Institute of Technology Division: Chemistry and Chemical Engineering Major Option: Chemistry Thesis Availability: Public (worldwide access) Research Advisor(s): Myers, Andrew G. Thesis Committee: Unknown, Unknown Defense Date: 23 October 1996 Record Number: CaltechTHESIS:11012025-083054910 Persistent URL: https://resolver.caltech.edu/CaltechTHESIS:11012025-083054910 DOI: 10.7907/k6mz-nt82 Default Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided. ID Code: 17745 Collection: CaltechTHESIS Deposited By: Benjamin Perez Deposited On: 06 Nov 2025 19:07 Last Modified: 06 Nov 2025 19:08 Thesis Files PDF - Final Version See Usage Policy. 123MB Repository Staff Only: item control page

Enantioselective Synthesis of Neocarzinostatin Chromophore Aglycone Thesis by Marlys Hammond In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy California Institute of Technology Pasadena, California 1997 (Submitted October 23, 1996) ii © 1997 Marlys Hammond All Rights Reserved Ill Acknowledgments The completion of this dissertation would not have been possible without the support and encouragement of many people. First and foremost, I would like to thank my advisor, Professor Andrew G. Myers, for allowing me the privilege of working within his research group on a truly exceptional project. He provided me with the material and intellectual resources necessary for the completion of the chemistry described herein. I have also acquired from him many significant, y~t less tangible, qualities. These attributes, critical for success in endeavors of this nature, include tenacity, patience, and, when appropriate, impatience. Words cannot express my gratitude. I would also like to thank the many individuals who have contributed to the chemistry contained within this dissertation. Among them are Dr. Philip M. Harrington, Dr. Jia-Ning Xiang, Dr. Yusheng Wu, Dr. Elaine Y. Kuo, Vijaya Subramanian, Dr. Bradley P. Morgan, and Steven D. Goldberg. Dr. Kristine Swiderek of the City of Hope, Duarte, CA, obtained the mass spectrum of neocarzinostatin chromophore aglycone complexed to apo-NCS. I would like to offer special thanks to Dr. Michael E. Kort, who carried out the DNA cleavage studies with neocarzinostatin chromophore aglycone, no easy feat. There are several people who have encouraged me in my pursuit, and they deserve my gratitude as well. Professor William B. Martin and Ms. Laura Kately first kindled my interest in organic synthesis. Professor Jeffrey Aube and Dr. Stephen W. Kaldor each have provided invaluable assistance and encouragement throughout this undertaking. I would like to thank all of the members of the Myers research group. Most notably Pete Dragovich (Petehead), Dave Gin (Davey-Dave), and, especially, Mark Fraley (Fraley) IV provided me with a tremendous amount of instruction, inspiration, encouragement, support, and laughter. Many thanks to Lydia McKinstry for her friendship and support. I would also like to thank, from the bottom of my heart, my classmates Cindy Parrish (Lou Who) and Norma Tom (Normanator) for their dear friendship and camaraderie. Many thanks are owed to Mary Shepard for reading through this thesis so thoroughly. Finally, I would like to thank Glaxo for a summer research fellowship (1993). V Abstract An enantioselective synthesis of neocarzinostatin chromophore aglycone (6) is described. The key features of the synthesis include 1) Sharpless asymmetric epoxidation of the allylic alcohol 136 to produce epoxy alcohol 137, 2) an intramolecular acetylide addition within the epoxy aldehyde 138 to furnish alcohol 139, 3) esterification of the diol 171 with the acid 22 and in situ cleavage of the chloroacetate ester to provide ester 172, 4) elimination of the C-1 alcohol of 175 to afford Jhe olefin 176, and 5) reductive opening of epoxy alcohol 120 with the combination of iodine, triphenylphosphine, and imidazole to afford neocarzinostatin chromophore aglycone (6). The synthetic pathway described is highly convergent, and should the supply quantities of 6 necessary for ongoing studies directed toward the completion of the total synthesis of neocarzinostatin chromophore (1), as well as the preparation of analogs bearing modified sugar residues. II i TMSQ., TMSO., /, H CH,0-t 0 CH 2a-t ~ TBS0 137 136 fi,C,x li,C o• II II H TMSQ,. H H CH,OH ~ TBS0 " < 171 139 138 ~ HO TBSO H,~ . . . . , O O H ""CH, o=(:~ .1/\H HO., H H H ; ••oH o ··oTES w 0 H,CO-..~X~OTES CH:, .; .; < 175 0 H3~ 0 T E S yU CH, 176 0 0 H,~ O H yU CH, 120 I .& 172 Vil Table of Contents Volume I Acknowledgments ............................................................................ iii Abstract ........................................................................................ v Table of Contents ............................................................................. vii List of Schemes ............................................................................... X List of Figures and Tables ........................ ·..· ......................................... xii List of Abbreviations ......................................................................... xiii Chapter 1. Introduction and Background ................................................. 1 Introduction........................................................................... 2 Background ........................................................................... 5 Chapter 2, Initial Synthetic Plan ............................................................ 8 Synthetic Plan ........................................................................ 9 Experimental Section ................................................................ 32 Volume II Title Page ...................................................................................... 412 Table of Contents (Yolume rn .............................................................. 413 List of Schemes, Figures, and Tables ...................................................... 414 Chapter 5. Thiol Addition Chemist,:y and DNA Cleavage Behavior of Neocarzinostatin Chromophore Aglycone ........................................ 415 Thiol Addition Chemistry ................. :......... ................................. 416 DNA Cleavage by Neocarzinostatin Chromophore Aglycone .. .... . ........... 421 Experimental Section ................................................................ 429 References and Notes .................................................. .. ........... .. ....... 434 Appendix. Catalog of Spectra .............................................................. 451 X List of Schemes ~~~ ~ Scheme I. Mechanism of Neocarzinostatin Chromophore Activation ........ 4 Scheme 11 .................................................................. .. ......... 7 Schemeill ............................... .... ......................................... 10 Scheme IV ..................................................... ....................... 11 Scheme V .................................................................... ... ...... 13 Scheme VI ................ ...................................... .. .................... 15 Scheme VII ........................................................................... 17 Scheme Vill .......................................................................... 18 Scheme IX .............. ................................................ .... .......... 21 SchemeX ........................ ... .................................................. 25 Scheme XI ............................................................................ 29 Scheme XII ........................................................................... 134 Scheme Xill .................................. ........................................ 136 Scheme XIV .......................................................................... 137 Scheme XV ........................................................................... 141 Scheme XVI. . . ....................................................... . ............... 144 Scheme XVII ......................................................................... 147 Scheme XVill ...................................................... .. ................ 248 Scheme XIX ..................... .... ................................................. 249 Scheme XX ........................................................................... 250 Scheme XXI. ................................ .. ....................................... 255 xi Schemes <continued) ~ Scheme XXII ......................................................................... 258 Scheme XXIII. ....................................................................... 263 Scheme XXIV ........................................................................ 268 Xll List of Figures and Tables ~ Fi~ures Figure 1. Ball and Stick Depictions of Ring-Closure Substrates 13 and 96 ...................................................... 140 Figure 2. Ball and Stick Depictions of Ring-Closure Substrates 13 and 124 ...... ............................................... 244 Figure 3. Complexation of 6 with apo-~CS .................................... 266 Tables Table 1. Attempted Inversion of Mesylate 62. .................................. 24 Table 2. Conditions Examined for the Conversion of 63 to an Epoxydienediyne.................................... . ........... .. ..... .. ... 26 xiii List of Abbreviations [a]: optical rotation (589 nm, 20 °C) A adenine A angstrom Ac acetyl AIBN 2,2' -azobis(isobutyronitrile) bp b~e pair(s) Bu butyl C grams per 100 mL of solution C cytosine <c:: degrees Celsius CAM eerie ammonium molybdate CD circular dichroism C6D6 hexadeuteriobenzene CDI 1,1 '-carbonyldiimidazole CI chemical ionization cm- 1 reciprocal centimeters Cp cyclopentadienyl CSA camphorsulfonic acid 8 chemical shift (parts per million) DBU 1,8-diazabycyclo[5.4.0]undecene DCC 1,3-dicyclohexylcarbodiimide de diastereomeric excess XIV DEf diethyl tartrate DIBAL diisobutylaluminum hydride DMAP 4(N,N-dimethylamino )pyridine DMF N ,N-dimethylformamide DMSO dimethylsulfoxide DNA deoxyribonucleic acid E entgegen EOC 1-(3-dimethylaminopropyl)-3ethylcarbodiimide hydrochloride ee enantiomeric excess EI ele,ctron impact equiv equivalent Et ethyl EtOAc ethyl acetate FAB fast atom bombardment FPLC fast protein liquid chromatography Ff Fourier transform g gram(s) G guanine gc gas chromatography h hour hv light HPLC high performance liquid chromatography HRMS high resolution mass spectroscopy Hz hertz l iso IR infrared xv J coupling constant L liter(s) m meta M molar [Mt molecular ion m-CPBA meta-chloroperoxybenzoic acid MEM methoxyethoxymethyl mesylate methanesulfonate mg milligram(s) MHz megahertz min minute(s) mL milliliter(s) mM millimolar mmol millimole(s) mol mole(s) mp melting point MS molecular sieves MS mass spectroscopy MW molecular weight µL microliter(s) n normal N normal (concentration) NCS neocarzinostatin nm nanometer(s) NMR nuclear magnetic resonance p para Ph phenyl xvi pH hydrogen ion concentration (log scale) Piv pivaloyl ppm parts per million Pr propyl Py pyridine R,Re rectus Rf retention factor rp reverse-phase S,Si sinister t tertiary T thymine TBAF tetrabutylammonium fluoride TBS tert-butyldimethylsilyl TBHP tert-butyI hydroperoxide IDS tert-butyldiphenylsilyl TES triethylsilyl Tf trifluoromethanesulfony I 1FA trifluoroacetic acid 1FE 2,2,2-trifluoroethanol THF tetrahydrofuran TIPS triisopropy lsil yl 1LC thin-layer chromatography TMGA tetramethylguanidium azide TMS trimethylsilyl TPS triphenylsilyl triflate trill uoromethanesulfonate p-Ts para-toluenesulfonyl xvii UV ultraviolet w watt w/v weight/volume ratio (g/100 mL) z zusammen 1 Chapter 1 Introduction and Background 2 Introduction The chromoprotein neocarzinostatin, isolated from the soil bacterium Streptomyces carzinostaticus, 1 was the first of the enediyne family of antibiotics2 to be isolated and is composed of a non-protein chromophore (1) bound to a 113-amino acid apoprotein (apoNCS). 3 The antitumor activity of neocarzinostatin is believed to arise from the ability of the chromophore component 1 to damage double-stranded DNA in the presence of a thiol cofactor and oxygen. 4 This DNA-cleaving activity has been demonstrated to reside solely within the chromophore 1, while the apoprotein is believed to function by imparting stability to the highly labile 1. 5 The binding of 1 to apo-NCS has been elucidated by X-ray crystallographic analysis of the holo-NCS complex. 6 The epoxy nonadiyne ring was found to contact opposing phenylalanine benzene rings. oriented perpendicular to the plane of the chromophore, as well as a disulfide bridge within the protein. It has also been suggested that apo-NCS may play a role in the transport of 1 across cell membranes. 6 o~o a,, CH 3 Q H-o OCH3 .,,--,; o,,, ... ---= ~ ·•P -.::---...,::::; • H ::::--- 1 DNA cleavage by 1 shows little sequence selectivity, but exhibits the base selectivity T > A >>G > C. 7 The cleavage reaction has been extensively studied, and a substantial body of evidence has been compiled in support of the mechanism given in Scheme I. 3c ,s ,9 In the presence of the cofactor methyl thioglycolate at - 70 °C, 1 is transformed into an intermediate whose 1H NMR signals correspond to the cumulene-ene- 3 yne 2 (R = CH 2CO 2CH 3). 8b Warming of the reaction mixture to -38 °C results in the further reaction of 2 to afford the rearranged indacene 4 (R = CH2CO2CH 3) through the proposed biradical species 3. The cycloaromatized product 4 has been isolated and characterized for the reaction of 1 with methyl thioglycolate,3c as well as for the reactions of 1 with the biologically relevant thiols glutathione and cysteine. 9c The biradical 3 is believed to abstract hydrogen atoms from the deoxyribose backbone of DNA, initiating a reaction cascade that, in the presence of oxygen, leads to single- and double-stranded DNA damage. Based on the mechanism presented in Scheme I, it may be suggested that the epoxy [7.3.0]dodecadienediyne core of 1 functions as the pharmacophore of the drug. The 2hydroxy-7-methoxy-5-methyl-l-naphthoate ester moiety is believed to serve as an intercalating agent10 while the remainder of the __drug is proposed to lie within the minor groove of double-stranded DNA. 11 The N-methylfucosamine substituent, largely protonated at physiological pH, is believed to provide a favorable electrostatic interaction with the negatively charged phosphate backbone of DNA. 12 It has further been proposed that the carbohydrate amino group functions as an internal base, catalyzing the addition of thiols to C-12 of the chromophore 1. 13 The X-ray crystal structure of holo-NCS (the chromoprotein complex) reveals that, within the complex, the distance between the nitrogen of the aminosugar and the C-12 carbon is approximately 5 A, or the van der Waals diameter of a sulfur atom. 6 Additional evidence to support this postulate has also been accrued, namely that the N-nitroso derivative of 1 and the simplified analog 5 both fail to add methyl thioglycolate in the absence of an external base. 13 5 4 Scheme I Mechanism of Neocarzinostatin Chromophore Activation 1 2 ! 4 3 5 The structural features of 1 alone define an intriguing synthetic target, with the high degree of unsaturation present within the bicyclic epoxydienediyne core and the strain of the 9-membered ring being exceptionally noteworthy. The degree of strain within the core is evidenced by the marked non-linearity of the acetylenic bonds in the crystal structure of holo-NCS, as the mean C-C=C bond angle was determined to be 161.5 ± 1.2°. 6 The combination of these elements contributes to the instability of 1, both neat and in solution, 6- in the absence of the apoprotein. The proposal that the aminoglycoside functions as a component of the activation mechanism of 1 has provided additional impetus for the development of a synthesis of the aglycone portion of 1 (neocarzinostatin chromophore aglycone, 6). 13 Such a synthesis would not only allow for the examination of the thiol addition chemistry and DNA-cleaving activity of 6 compared to 1, but also the introduction of sugars lacking nitrogen substituents and other modified carbohydrate residues. Herein is described the first enantioselective synthesis of neocarzinostatin chromophore aglycone (6).14 Background A variety of "model" studies, providing structures that little resemble 1 or the epoxydienediyne core, have been reported. 15 These systems generally were accessed by 6 construction of acyclic systems or analogs containing a less strained ten-membered ring in place of the nine-membered ring. 16 To date, the number of nine-membered ring-containing ~BuC02 11 £Ji 7 OH 8R=H 9 R = CH3 0 10 models reported is small. 17'18 Such systems, including representative structures 7-10, lack critical structural elements found in the natural product 1 and were obtained through synthetic sequences that would prove difficult to extend to the synthesis of the fully elaborated epoxydienediyne core of 1. A single highly functionalized model epoxydienediyne (5) has been prepared by Dr. P. M. Harrington of this research group.13,19 The synthesis of the epoxydienediyne pharmacophore of 1 involved three key transformations. First, an intrarnolecular acetylide addition within the a,B-unsaturated aldehyde 13 produced a separable mixture of diastereomeric nine-membered ring alcohols 14a and 14b (Scheme Ila). 13.1 9 Following this, silylation of the secondary alcohol of 14 b and exposure of the product to trifluoroacetic acid afforded the transposed trifluoroacetate 15 (Scheme Ilb). After conventional functional group manipulation to produce 16, extended elimination of the secondary alcohol of 16 produced the epoxydienediyne 5. 13 It was this synthetic sequence that served as the platform for the studies that have resulted in the enantioselective synthesis of 6. 14 7 Scheme II a) i. LiN(TMSh, three steps PhCH3 , -78 °C TMS R 11 12 t-BuC02 LiN(TMSh, CeCl 3 , II t-BuCO2 t-BuCO2 THF,-78 °C II 11 H II II + H CHO OH 13 14a 14b b) 1. Et3 N, CH3OH, O °C t-BuCO2 1. TMSCI, Et3N, 14b 2. TBSOTf, 2,6-luticine, II II CH 2Cl 2 , O °C CH 2Cl2 , -78 °C .,,H OTMS 2. TFA, CH 2C'2, O °C 3. Et:JN-3HF, CH3CN, 23 °C O2 CCF3 49% 43% 15 t-BuCO2 t-BuC02 (CH 3SO2hO, Py, II II ..,H OH CH 2Cl 2 , 0 °C II II >50% OTBS 16 OTBS 5 8 Chapter 2 Initial Synthetic Plan 9 Initial Synthetic Plan The strategy adopted at the outset of these studies was to apply the chemistry developed for the construction of the epoxydienediyne 5 to the synthesis of the more highly oxygenated core of 6. It was expected that the final steps of the synthesis would include extended elimination of an allylic alcohol such as 17 and, if necessary, deprotection of the C-10 alcohol (Scheme nn. Using the allylic transposition protocol given in Scheme 11b (Ch. 1), the alcohol 17 would be derived from the alcohol 18, which would be the product of an intramolecular acetylide addition within the cx.,j3-unsaturated aldehyde 19. It was anticipated that the ring-closure substrate 19 could be constructed by the sequential coupling and elaboration of the epoxydiyne 20, enone dimethyl acetal 21, and the naphthoic acid 22. Accordingly, efficient syntheses of each of the component pieces 20-22 were developed. The synthesis of epoxydiyne 20 was initially optimized by E. Y. Kuo in this group, and is briefly summarized below. 14•20 Beginning with D-glyceraldehyde acetonide (Scheme IVa), 21 addition of lithium trimethylsilylacetylide in THF at -78 °C produced a 1.3: 1 mixture of diastereomeric alcohols 23 in 81 % yield. 22 The alcohols 23 were then oxidized to the propargylic ketone 24 with PDC and acetic acid in the presence of 3A molecular sieves in dichloromethane at 23 °C. 23 The ketone 24 was found to be unstable to concentration; consequently, the crude product was used directly in the next reaction without concentration or further purification. The tert-butyldimethylsilyl-protected propargyl alcohol 25 24 was converted to the corresponding bromide, 25 which, after purification by reduced pressure distillation, was transformed to the Wittig salt 26 (Scheme IVb) by treatment with triphenylphosphine in benzene at 23 °C. 26 A solution of the ketone 24 in THF was added to the ylide derived from deprotonation of 26 with potassium hexamethyldisilazide (KN(TMS) 2 ) to produce the enediyne 28 as an approximately 3:1 mixture of olefin isomers in which the desired E isomer predominated. The isomers were 10 Scheme III 0 o=< O''' 11 11 11 11 H O.: H3CO .: W OH OR ~J ~ OH 0 H,co_ I :0H CH 3 CH 3 17 6 o::=< 11 11 11 TMSO,,,. H CHO d 0 H3CO W OH I CH 3 19 18 0 OH H3C O ~ O H yv CH 3 21 22 11 Scheme IV a) Li-C:CTMS, PDC, AcOH, THF,-78°C 3A MS, CH 2Cl 2 81% 23 24 b) e 1. Br2, PPh3, TBS--==-~, '+' Br Im, CH 2Cl 2 OH 2. PPh 3, C6H6 25 TBS--~,,;;:;/ ~ 27 78% (two steps) i. KN(TMS)2, THF, -78 °C; 1. K2C03 , CH 3OH, 0 °C ii. 24, -784 -15 °C 2. 1 NHCI, THF, 23 °c 79% (two steps) 64% 28 1. TDSCI, Et3N, DMAP, HO HO CH2Cl 2, 0 °C H01x H 3A MS, CH2Cl 2, -20 °C 2-methoxypropene, Ir TsOH, DMF, 23 °C H01' H TBS 29 82% 2. (-)-DET, Ti(Oi-Pr) 4 , TBHP, 86% (three steps) TBS 32 12 not separated at this stage, but instead the acetylenic trimethylsilyl group was removed by treatment with potassium carbonate in methanol at O °C,27 and the acetonide was cleaved by reaction with a mixture of lN hydrochloric acid and THF (1:1) at 23 °C. 28 The olefin isomers proved to be separable at this stage, and flash column chromatography29 provided the pure (E) isomer 29 as a pale yellow solid (mp 54 °C) in 64% yield from 28. The primary alcohol of 29 was selectively protected as a IDS ether (30), 30 and the epoxide was introduced under the Sharpless asymmetric epoxidation conditions employing (-)-D-DET. 31 Cleavage of the TDS ether was carried out with triethylarnine trihydrofluoride to provide epoxydiol 32 as a pale yellow solid (mp 78 °C). 32 The enantiomeric purity of intermediate 32 was established to be ~95% ee by 1H NMR analysis of both the mono- and the bisMosher ester derivatives of 32. 33 The acetonide was re-introduced by the acid-catalyzed reaction of the epoxydiol 32 with 2-methoxypropene to provide epoxydiyne 20 as a pale yellow solid (mp 43-44 °C). 34 The synthesis of the enone dimethyl acetal component (+)-21 commenced with the well-known prostaglandin precursor (+ )-33. 35 Application of chemistry developed by Noyori et al., involving the Michael addition of trimethylsilyl phenyl selenide into the enone followed by trapping of the intermediate enol with trimethyl orthofonnate and in situ oxidation and elimination of the selenide, allowed for the introduction of the dimethyl acetal substituent in a single step. 36 The yield for the conversion of (+ )-33 to (+ )-21 was found to be highly dependent upon the exact conditions under which the reaction was carried out. 6 i. PhSeTMS, TMSOTf, CH 2Cl 2 , -78 °C ii. HC(OCH3)3 , -25 ➔ -20 °C TBSO.; (+)-33 &CH(OCH,l, TBSO~ 80% (+)-21 13 Formation of the initial Michael adduct between enone (+ )-33 and trimethylsilyl phenyl selenide with catalytic TMSOTf proceeded smoothly at -78 °C. The critical phase of the reaction was found to occur during the addition of trimethyl orthoformate and the subsequent warming. The highest yields of 21 were obtained when freshly distilled trimethyl orthoformate was added at -78 °C, and the reaction mixture was allowed to warm to -25 °C, and then to -20 °Cover 45 minutes. Pyridine and hydrogen peroxide were added immediately after the reaction mixture turned from turbid to clear. When the reaction was carried out with careful monitoring of each stage, the enone dimethyl acetal 21 could be isolated in 80% yield as pale yellow needles (mp 29.5-30.5 °C). At the outset of these studies the substrate for the above reaction, enone (+)-33, was prepared using the sequence shown in S_cheme V. This route, the subject of an Organic Syntheses preparation, 37 was found to be both lengthy and inconvenient for large- scale material throughput. In particular the wheat germ lipase-catalyred hydrolysis of an intermediate acetate ester required a total of ten days for completion: seven days for the hydrolysis and an additional three days for continuous extraction of the highly watersoluble product. Most importantly, it was determined that the enantiomeric excess (ee) Scheme V OH 0 ~ Ad:) PCC, NaOAc, 4A ms, CH2Cl2 6 ,• AcO 34 6 HO~ TBSCI, Et3 N, DMAP, CH2Cl2 6 rsso'· (+)-33 wheat germ lipase phosphate buffer 14 of the enone (+)-33 was quite variable, and often unacceptably low. A method for the determination of the enantiomeric purity of (+ )-33 was developed, which involved the 1,2reduction of (+ )-33 with DIBAL in toluene at - 7 8 °C.35 Separation of the diastereomers and preparation of the Mosher ester derivative 33 of the major diastereomer 35a was followed by gas chromatographic analysis to determine the diastereomeric purity of the product ester. 38 The racemization was determined to be occurring during either the enzymatic hydrolysis or the subsequent silylation through analysis of the enantiomeric purity of (+)-33 and each of the intermediates in the synthesis. Additionally, an improved synthesis of enone (+ )-33 was developed. 35 0 0 TBSO.{ (+)-33 OH DIBAL, toluene, -78 ~C 0 . , TBSO 35a OH + 0 ~- TBSO 35b The modified synthesis of enone (+)-33 is given in Scheme VI. The synthesis was initiated with the same starting material utilized in the aforementioned preparation of (+ )33. The highly enantiomerically enriched monoacetate 34, prepared by the enzymatic hydrolysis of the corresponding meso diacetate, 40 was converted to the pivaloate ester 3 6 in 99% yield by treatment with pivaloyl chloride, triethylamine, and DMAP in dichloromethane at O °C. Selective hydrolysis of the acetate ester within 36 was accomplished using potassium carbonate in methanol to afford the hydroxy ester 37 in 88% yield and 2::99% ee, as determined by gas chromatographic (gc) analysis of the corresponding Mosher ester. Addition of TBSCl, triethylamine and DMAP to 37 produced the corresponding silyl ether 38 as a white solid (mp 64-66 °C) in 88% yield. 41 The pivaloate group of 38 was cleaved with DIBAL in toluene at -78 °C, affording the alcohol 39 in quantitative yield and 2::99% ee as determined by gc analysis38 of the corresponding Mosher ester derivative. 33 The latter observation established that intramolecular migration 15 of the tert-butyldimethylsilyl group of 39 was not detectable under these conditions. Oxidation of 39 with pyridinium chlorochromate in dichloromethane42 provided (+ )-33 in 88% yield after flash column chromatography. Reduction of (+ )-33 prepared this way with DIBAL and Mosher esterification 33 of the resulting major alcohol diastereomer 35a afforded a Mosher ester of ~99% diastereomeric excess (de), as determined by gc analysis. 38 To confirm the result, the minor diastereomer in the reduction, the trans alcohol 35b was also transformed into its Mosher ester derivative. 33 The resulting Mosher ester was shown to be ~9% de by gc analysis. 38 These results established that the synthetic (+)-33 produced by the new route was of 2::99% ee and that the analytical method used proceeded without enantiomerization of 33 or any derivative in the sequence. Scheme VI OH 0 .::· kO 34 OPiv OPiv PivCI, Et 3N, DMAP, CH2Cl2, 0 °C 0 K2CO3, CH3OH 36 88% 23 °C .:: kO 99% ~Piv 0 .:: TBSO 38 0 TBSCI, Et3N, DMAP, .::· HO 37 99% 0 .::· TBSO 39 88% 0 9H DIBAL, PhCH 3, -78 °C CH2Cl2, 0 ➔ 23 °C PCC, CH2Cl2, 23 °C 88% 6 ,•· TBSO (+)-33 The enantiomeric purity of the enone dimethyl acetal 21, prepared from the highly enantiomerically enriched ( + )-33, was also determined by the 1,2-reduction - Mosher esterification sequence in analogy to (+ )-33. 33 The diastereomeric Mosher esters, however, could not be effectively separated by gc, hence the de of these esters was 16 determined by the less accurate method of 1H NMR analysis. By this technique the enantiomeric enrichment of 21 was found to be ~90% ee. The synthesis of the 2-hydroxy-7-methoxy-5-methyl-1-naphthoic acid moiety 22 is given in Scheme VII. This sequence is the most efficient of several reported syntheses, and was developed within this research group by V. Subramanian. 44 Briefly, 4-bromo-3methylanisole (40)45 underwent Heck coupling46 with tert-butyl acrylate, and the resultant ester (41) was hydrolyzed by treatment with trifluoroacetic acid (1FA) to provide the carboxylic acid 42 in 89% overall yield. Following a known acylation protocol,47 the latter product was treated with carbonyldiimidazole in THF and the resulting acylimidazolide was trapped in situ with magnesium methyl malonate to provide a ~-keto ester (43) which, when exposed to sulfuryl chloride in benzene at 66 °C, 48 produced the photocyclization precursor 44 in 72% yield for the two steps. Irradiation of a deoxygenated methanolic solution of 44 with a 450-watt Hanovia medium pressure mercury arc lamp (quartz immersion well) for 1 h at 23 °C produced methyl ester 45 in 53-63% yield after column chromatography. Saponification of ester 45 with sodium hydroxide in aqueous methanol afforded the naphthoic acid 22 in 91 % yield. The acid 22 provided 1H NMR, 13C NMR, FTIR and mass spectroscopic data that was identical to the reported value, 49 and the combined yield of 22 from 4-bromo-3-methylanisole was 31-37%. Having the components 20-22 in hand, the studies directed toward the synthesis of the nine-membered ring core of the aglycone 6 were initiated. First carried out by Dr. J. N. Xiang in this group, the construction of the core followed closely the chemistry developed for the synthesis of model epoxydienediyne 5. 13' 19 Deprotonation of epoxydiyne 20 with lithium hexamethyldisilazide (LiN(TMS) 2) in toluene at -78 'C followed by addition of (+)-21 afforded alcohol 46 in 75% yield and with ~20:1 selectivity for the diastereomer shown (Scheme VIII). 50 The alcohol 46 was then treated with tetrabutylammonium fluoride (TBAF) to remove both silyl groups and provide diol 4 7 in 17 Scheme VII 1. i. COi, THF, 23 °c 1. t-Butyl acrylate, E!:3N, ii. magiesium monomethyl P(<>-tolh, Pd(OAc)i, 108 °c malonate, THF, 23 °C 40 42 89% hv, Et3N, H 3 "C O Cl ~ ~ IO CH 3 .o OH OCH3 0 CH 3OH, 23 °C 53-63% 72% CL CO2CH3 H3CO~OH Y0 CH 3 44 0 0 OCH3 w. 45 w H3C O ~ O H H3CO~ . OH CH 3 OH 91% CH 3 22 18 Scheme VIII i. LiN(TMS) 2, PhCH 3 , -78 °C 11 ii. (+)-21 HO,,,. 75% 46 22, DCC, 4-pyrrolidinopyridine, II i Bu4 NF, THF, O ° C CH 2 a 2 , o ➔ 23 °c H 99'% 7<Y'lo HO.: 47 0 o=<o•·· 11 HO,,,. 1. HCI, CH 30H, 11 23°c, 79% H HO,,.. CHO 2. COi, THF; (±)-CSA, CH 3 CN!Hp (1 :1), 23 °c, 80% """x 1yU 0 H,co, , OH CH3 1. TMSOTf, 2,6-lulidine, 11 H TMSO,,.. CH2Ci.!, -78 °C, 91% CHO 2. MEMCI, i-Pr2NEt, CH2a2, 0 °C, 94% """X 1yU 0 H,co, , OMEM CH3 52 50 19 quantitative yield. 51 Esterification of the naphthoic acid 22 was then carried out using dicyclohexylcarbodiimide (DCC) and catalytic 4-pyrrolidinopyridine or DMAP in dichloromethane at O°C. 52 Under these conditions, ester 48 was obtained in 70% isolated yield. The acetonide protective group of 48 was removed by reaction with concentrated hydrochloric acid in methanol at 23 °C, and the ethylene carbonate group was introduced by treatment of the triol product with CDI. 53 Exposure of the crude reaction mixture to (±)camphorsulfonic acid in a 1:1 mixture of acetonitrile and water at 23 °C afforded the a.,~unsaturated aldehyde 50 in 63% yield from the intermediate 48. The tertiary alcohol of 5 0 was protected as a silyl ether by reaction with TMSOTf and 2,6-lutidine in dichloromethane at -78 °C, 54 and treatment of the intermediate with l\1EM chloride and diisopropylethylamine in dichloromethane at 0_0 c55 produced the protected ring-closure substrate 52 in 86% overall yield from intermediate 50. The conditions developed for the closure of the nine-membered ring in the synthesis of 5 found successful application for the acetylide addition into the aldehyde within substrate 52. 13 ' 19 Treatment of a premixed suspension of the intermediate 52 and cerium(IIl) chloride (3 equiv) in THF at -78 °C with LiN(TMS) 2 provided secondary 0 0 o=<o•·· o=<o•·· 11 TMSO,,,. H CHO LiN(TMSh, CeCl3, THF, -78 °C II 11 73% alcohol 53 as a pale yellow oil in 73% yield. 19 The reaction was found to be sensitive to the amount of base used; addition of excess base resulted in the cleavage of the ethylene 20 carbonate of both 52 and 53. Previous studies carried out by Dr. J.-N. Xiang in this group indicated that the protocol employed for the transposition of the allylic alcohol, in analogy to the conversion of 14b to 15 (Ch 1, Scheme 11), 13 proved to be ineffective in this more highly oxygenated core system. Specifically, the exposure of silyl ethers such as 54 and 55 to trifluoroacetic acid in dichloromethane at O °C resulted in either recovery of unreacted starting material or simple cleavage of the silyl ethers. 50 As a result, it became necessary to explore alternative methodology for the transposition of the C-9 - C-10 olefin into the nine-membered ring and the introduction of the C-10 alcohol. H3CXO 11 11 H3C o••· II 11 H ~ TBSO 55 The studies carried out by Dr. J.-N. Xiang also revealed that, when the naphthoate ester was present within nine-membered ring intermediates such as 56, reaction with trifluoromethanesulfonic anhydride (triflic anhydride) and 2,6-lutidine in dichloromethane at -78 °C followed by an aqueous work-up afforded the rearranged allylic alcohol 57 having cis stereochemistry relative to the naphthoate substituent (Scheme IXa). 50 The stereochemistry was assigned based on the coupling constant between the C-10 and C-11 protons, 56 found to be ca. 5.5 Hz, significantly larger than the O Hz coupling constant 21 Scheme IX a) 0 0 o=<o•·· o=( o•·· 11 11 Tf2O, 2,6-lutidine, CH2Cl 2, -78 ➔ 0 °C 11 TMSO,,.. 0 11 0 H3C O ~ O y) CH 3 5Gb b) 0 o=< 0 o=( 11 11 o·· Tip, 2,6-lutidine, 11 11 CH 2Cl 2, -78 ➔ 0 °C H ·•,oTBS ·' 6 ••,OH o H3C O ~ O T D S yv CH3 59 22 observed between the two corresponding protons in 1. 3 • The mechanism proposed for this rearrangement involves activation of the secondary alcohol and neighboring group participation of the ester carbonyl in the allylic transposition via the dioxolenium ion intermediate 56a. 57 Subsequent trapping of this intermediate with water at the carbonyl carbon, rather than at the C-10 position, would result in the formation of the cis alcohol 57. Further evidence for the intermediacy of ion 56a was found in the observation that a small amount of the rearranged product in which the naphthoate ester had migrated to the C-10 position was also formed. Additionally, substrates in which the hydroxyl group of the naphthoate ester had been protected with the labile IDS group afforded, in some cases, a rearranged product in which this protective group had been lost. The observation of this deprotected product suggested the further intermediacy of the neutral species 56b. An analogous transposition was observed when the tertiary alcohol 58 (Scheme Xllb) was treated with triflic anhydride and 2,6-lutidine in dichloromethane at -78 °C, the transposition now occurring in the direction of the tertiary alcohol to provide the tetrasubstituted allylic alcohol 59. While the nine-membered ring products corresponding to 53, 56, and 58 were found to be somewhat unstable, slowly decomposing over several hours when neat, the rearranged alcohols corresponding to 57 and 59 were significantly less stable, decomposing within minutes in neat form as well as when stored overnight at -20 °C in a frozen benzene matrix. The replacement of the IDS protective group with the less labile MEM protective group in 53 was intended to suppress the loss of the naphthol protective group during the rearrangement reaction. Having substrate 53 in hand, the decision was made to protect the C-8 secondary alcohol and free the C-1 tertiary alcohol for rearrangement, as transposition in this direction would produce the relatively more stable tetrasubstituted olefin intermediate. With this in mind, treatment of alcohol 53 with TBSOTf and 2,6-lutidine in dichloromethane at -78 °C58 followed by selective removal of the TMS group with triethylamine trihydrofluoride in THF at O °C 32 produced the tertiary alcohol 61 in 81 % 23 overall yield. It was this alcohol that was employed as a substrate for the examination of many different conditions to effect allylic transposition and provide a rearrangement product having the requisite trans stereochemistry between the C-10 and C-11 substituents. 0 0 o=< o==< 0''' 11 1. TBSOTf, 2,6-lutidine, CH2Cl2, -78 °C, 93% 11 11 11 2. Et3N•3HF, THF, 0 °C, 87% Reaction of the tertiary alcohol 61 with excess methanesulfonyl chloride and triethylamine in dichloromethane at O °C provided rearranged mesylate 62 directly. 59 The mesylate 62 appeared to be an ideal substrate for nucleophilic inversion, which would afford a product with trans relative stereochemistry between the C-10 and C-11 substituents. Table 1 summarires many of the conditions examined to effect this inversion. Some conditions led to the formation of a new product (entries 6 and 7) that was 0 0 o=<o·· o=( o•·· 11 11 11 ·,, H OTBS H 0 ,-·· H0CO, ,r'--XO/OMEM ylJ CH3 61 11 CH3S02CI, Et3N, CH2Cl2, 0 °C ~,,,OS02CH3 H3C O ~ O M E M ~ CH3 62 24 0 e=< II 11 11 11 H H3CO .:· W CH3 ·----------~ ·~OS02CH3 o'· OMEM H3C O ~ O M E M .0 62 0 X yv CH 3 Table 1. Attempted Inversion of Mesylate 62. Entry Conditionsa Result 1 NaOAc, TFE, 3A MS, 0 °C no reaction 2 NaOCCCl 3, TFE, 3A MS, 0 °C no reaction 3 KN0 2, DMF, 23 °C decomposition of 62 4 NaN3, EtOH, -10 ➔ 23 °C decomposition of 62 5 TMGA, 60 CH 2Cl2, 23 °C decomposition of 62 6 H 20, C 6H 6 , 23 °C "new" product 7 5% ethylene glycol, HMPA, 0 ➔ 23 °C "new" product • TFE = 2,2,2-trifluoroethanol; DMF = N,N-dimethylformamide; 1MGA = tetramethylguanidinium azide; HMPA = hexamethylphosphoramide 25 determined not to be the inverted alcohol. The structure of this product was not determined; however, the 1H NMR and FTIR spectral data for this new product were consistent with the opening of the C-4 - C-5 epoxide. Because of the propensity of mesylate 62 to either decompose or undergo an unwanted side reaction, this approach was abandoned in favor of a new, but related, strategy. With the idea of taking advantage of the ability of the tertiary alcohol to undergo facile allylic transposition, it was envisioned that cyclic, activated intermediate B, derived from diol A could be formed between the C-1 and the C-8 alcohols (Scheme X). The intennediate B could then rearrange to intennediate C, which then could eliminate, either spontaneously or in the presence of a base, to produce the epoxydienediyne D directly. In situ treatment with a nucleophile such as water _would then yield the product E. With this in mind, nine-membered ring alcohol 53 was converted to diol 63 in 89% yield by reaction Scheme X o=<o 0 o=<o o•·· 0'' 11 ~ 11 o=< O'' 11 ...I l,YI .~.,0 .,,,0 ·---·--~ II ·-·---·~ H ··,o H RO-:· B 0 ... C 0 a=<O'' II II -:· RO ___ nuc ___ ,..,.. II ':, y o' 'oH D :., ,,Y 0 RO a=< _______ I _, RO-: A 11 E 11 26 o=< 0 0 o=( o•·· (Y'' 11 11 11 11 89% Table 2. Conditions Examined for Conversion of 63 to an Epoxydienediyne. Entry Conditions 1 Martin sulfurane,61 CH2Cl2 , 0 ➔ 23 °C 2 Martin sulfurane,61 CH 2Cl2 , -78 °C 3 SO 2Cl 2 , Et3N, CH2Cl2 , 0 ➔ 23 °C 4 SO2CI2, pyridine, CH2Cl2, 0 °C 5 SO2Cl2 , i-Pr2NEt, CH2CI2 , 0 ➔ 23 °C 6 SO 2Cl2, CH2C12 , -78 ➔ 0 °C 7 PhCI2P, pyridine, CH2Cl2 , 0 ➔ 23 °C 8 PhCI 2P, i-Pr2NEt, CH2Cl2 , 0 ➔ 23 °C 9 PhCl2P, CH2Cl2 , 0 ➔ 23 °C 10 (i-Pr) 2Si(OTf)i, 2,6-lutidine, CH2Cl2 , -78 °C 27 with triethylamine trihydrofluoride in THF at O 0 C. Table 2 provides a summary of conditions examined to carry out the conversion corresponding to A ➔ E, all of which caused the decomposition of the diol 63 or resulted in the formation of complex reaction mixtures. Because of the lack of encouraging results, this approach was discontinued. Hoping to make use of the triflic anhydride-mediated rearrangement of substrates such as 53 and 56, which provided products having the requisite regiochemistry but incorrect stereochemistry, a study of the inversion of the resultant C-10 alcohol under Mitsunobu conditions was initiated.62 Secondary alcohol 53, upon treatment with excess triflic anhydride and pyridine, was converted to the highly unstable rearranged alcohol 64, with the alcohol having the expected cis stereochemistry relative to the naphthoate ester. 0 0 o=<0''' o=< 11 11 Tf 2 O, pyridine, CH2Cl2, -78 ➔ 0 °C 11 11 TMSO,,. The alcohol 64 was then treated with either chloroacetic acid or p-nitrobenzoic acid under Mitsunobu conditions. Both chloroacetic acid63 and p-nitrobenzoic acid 64 have been reported to be excellent nucleophiles under Mitsunobu conditions; however, none of the expected inverted ester product was isolated from any of the reaction mixtures. Mitsunobu inversions have also been found to be highly solvent dependent; accordingly, these reactions were examined in a variety of solvents, including benzene, THF, dichloromethane, and toluene. None of these solvents was found to be superior to any of the others and in all cases rapid decomposition of the substrate 64 was observed. The 28 conclusions reached from this series of experiments were two-fold: 1) the MEM group protecting the hydroxyl of the naphthoate ester may have been hydrogen bonding with the C-10 alcohol in the rearranged product and blocking it from further reactivation, and 2) the rearranged alcohol 64 was simply too unstable to be used as a synthetic intermediate. Consequently, this phase of synthetic studies was concluded. The participation of the naphthoate ester in the triflic anhydride-induced rearrangement of alcohols 53, 56, and 58 prompted the consideration of setting the C-10 C-11 trans stereochemistry prior to the introduction of the ester. To test the rearrangement behavior of nine-membered ring substrates lacking the naphthoate ester, the simplified intermediate 7 0 was constructed. Beginning with the known intermediate 4 7 , the C-10 alcohol was protected as a TBS ether by reaction with TBSCI, triethylamine, and catalytic DMAP in dichloromethane at O °C to afford the silyl ether (65) in 92% yield (Scheme Xl). 41 The dimethyl acetal was then hydrolyzed with p-toluenesulfonic acid in acetone at 23 °C to provide a,~-unsaturated alcohol 66 as a white solid (mp 90-92 °C) in 90% yield. 64 Silylation of the tertiary alcohol 66 with 1MSOTf and 2,6-lutidine in dichloromethane at -78 °C produced the silyl ether (67) in 88% yield, 54 which was subsequently treated with LiN(TMS) 2 in the presence of three equivalents of cerium(III) chloride to afford the ring-closed alcohol 68 in 82% yield.13 ' 19 The trimethylsilyl ether was selectively removed in 75% yield by treatment with potassium fluoride in methanol, and a triphenylsilyl (TPS) group was introduced by treatment with triphenylsilyl chloride, triethylamine, and DMAP in dichloromethane at O °C to provide TPS ether 70 in 66% yield. 66 The yield of this reaction was moderated by the formation of the product in which both the secondary and tertiary alcohols had been silylated. The tertiary alcohol 70 was examined as a substrate for allylic transposition reactions. 29 Scheme XI 1. TBSCI, DMAP, E'3N, CH 2Cl 2, O °C II i HO,,. 2. p-TsOH, acetone, 23 °c H CHO rsso--' HO., 84% 47 66 H3CXO 1. TMSOTf, 2,6-lutidine, H3C O'' 1. KF, CHpH, 23 °C CH2Cl2, -78 °C 11 11 H 2. LiN(TMS)2, Cea3, 2. Ph3SiCI, E'3N, DMAP, CH2Cl2 THF, -78 °C 72% TBSO.: 70 TBSO 50% 68 30 The absence of the C-11 ester functionality markedly changed the behavior of substrate 70 towards triflic anhydride. Treatment of 70 with triflic anhydride and pyridine in dichloromethane at -78 °C followed by warming to 0 °C resulted in nonspecific decomposition of the starting material. The reactivity of alcohol 7 0 toward methanesulfonyl chloride and triethylamine in dichloromethane at 0 °C,59 on the other hand, 11 II H CH3SO2CI, Et3N, CH2Cl2, 0 °C II II ··,oTPs TBSO.: 70 paralleled that of alcohol 61, affording the unstable rearranged mesylate 71. Attempted inversion of mesylate 71 with water and 2,6-di-tert-butylpyridine in 2,2,2-trifluoroethanol resulted in decomposition of the substrate. Introduction of the protected N- methylfucosamine sugar derivative 72 by displacement of the mesylate with the anomeric oxygen of the glycoside was also examined. 67 Neither treatment of the mesylate 71 with the glycoside 72 in trifluoroethanol in the presence of 2,6-lutidine and 3A molecular sieves at 23 °C nor treatment of 71 with the potassium salt of 72 in a 4: 1 mixture of THF and HMPA at -40 °C produced the desired inverted product; in fact, these reactions only resulted in decomposition of the mesylate substrate. 31 The lack of success in obtaining products with the requisite trans relative stereochemistry between the C-10 and C-11 substituents using the strategies discussed above prompted the following conclusions: 1) the presence of oxygenation at the C-11 position greatly altered the rearrangement behavior of intermediates such as 53, as the trifluoroacetic acid-mediated rearrangement of the corresponding trimethylsilyl ethers failed completely within this class of substrates, and 2) it was determined that rearranged intermediates 57, 59, 62, 64, and 71 were significantly less stable than even the nonrearranged nine-membered ring substrates. It was this instability that complicated all attempts to invert the C-10 center. In light of the findings discussed here, the decision was made to pursue strategies involving structurally and mechanistically different approaches to the stereoselective construction of the functionalized epoxydienediyne core of 6. 32 Experimental Section General procedures. All reactions were performed in flame-dried round bottom or modified Schlenk (Kjeldahl shape) flasks. Tlle flasks were fitted with rubber septa and contained a positive pressure of argon unless otherwise stated. Stainless steel syringes or cannula were used to transfer air- and moisture-sensitive materials. Concentration in vacuo was accomplished by rotary evaporation at water aspirator pressure (approximately 25 torr). Flash chromatography was carried out as described by Still et al., employing 230400 mesh silica gel. 29 Analytical thin-layer chromatography was performed using glass plates pre-coated with 0.25 mm 230-400 mesh silica gel impregnated with fluorescent indicator (254 nm). Thin-layer chromatography plates were visualized by exposure to ultraviolet light (noted as UV') and/or by exposure to an acidic solution of p-anisaldehyde (noted as 'anisaldehyde') or ethanolic phosphomolybdic acid (noted as 'PMA') followed by heating on a hot plate. Materials. exceptions. Commercial reagents were used as received, with the following Tetrahydrofuran (TI-IF) was distilled from sodium benzophenone ketyl. Dichloromethane, benzene, toluene, acetonitrile, N,N-diisopropylethylamine, hexamethyldisilazane, 2,6-lutidine, pyridine, and triethylamine were distilled from calcium hydride at 760 torr. Acetic acid was distilled from chromium trioxide at 760 torr and was stored over 4 A. molecular sieves. Anhydrous ceriurn(III) chloride was prepared from the 33 heptahydrate by heating at 100 ·c and 1 torr for 12 h. Methanesulfonyl chloride was distilled from phosphorous pentoxide at 760 torr. Trifluoromethanesulfonic anhydride and trimethylsilyl trifluoromethanesulfonate were stored in a glove box in round bottom flasks fitted with polycarbonate or glass stoppers. The molarity of n-butyllithium solutions was determined by titration with 2,6-di-tert-butyl-4-methylphenol using fluorene as an indicator (average of three determinations). Where indicated, fresh solutions of lithium hexamethyldisilazide were prepared by the addition of a solution of n-butyllithium (1.0 eq) in hexanes to a solution of hexamethyldisilazane (1.0 eq) in hexanes at -20 ·c, followed by warming to room temperature. Instrumentation. Infrared (IR) spectra were obtained using a Perkin-Elmer 1600 FT-IR spectrophotometer referenced to a pol)'.styrene standard. Data are presented as follows: frequency of absorption (cm· 1) intensity of absorption (v = very, s = strong, m = medium, w = weak) and assignment where appropriate. Proton nuclear magnetic resonance (1H NMR) spectra and carbon nuclear magnetic resonance (1 3C NMR) spectra were recorded on either a General Electric QE-300 (300 MHz) or a JEOL GX-400 (400 MHz) NMR spectrometer; chemical shifts for protons are reported in parts per million downfield from tetramethylsilane and are referenced to residual protium in the NMR solvent (CHC1 3: o7.26, C D H: o7.20, CDHCl o5.29, SO(CD )(CD H): o2.49). Data 6 5 2: 3 2 are represented as follows: chemical shift, multiplicity (br =broad, s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, complex = multiple resonances, app. = apparent), integration, coupling constant in Hertz (Hz), and assignment. Optical rotations were determined on a Jasco DIP-181 digital polarimeter equipped with a sodium lamp source. Melting points were determined on a Btichi SPM-20 melting point apparatus and are uncorrected. High resolution mass spectra were obtained either at the University of California, Riverside Mass Spectrometry Facility; the Midwest Center for Mass Spectroscopy, Lincoln, Nebraska; the University of California, Los Angeles Mass 34 Spectrometry Facility; or the California Institute of Technology Mass Spectrometry Facility. 35 Li-C=CTMS, THF,-78 °C 81% 23 Propargylic alcohol 2 3 Lithium hexamethyldisilazide (164 mL of a 1.0 M solution in THF, 0.164 mol, 1.20 equiv) was added in a dropwise manner over 30 min to a solution of trimethylsilylacetylene (25 mL, 17 .6 g, 0.179 mol, 1. 10 equiv) in tetrahydrofuran (720 mL) at-78 °C. The resultant solution was maintained at-78 °C for 30 min, and a solution of D-glyceraldehyde acetonide (19.4 g, 0.149 mol, 1.0 equiv) in tetrahydrofuran (225 mL) was added over a period of 30 min. The reaction mixture was maintained at -78 °C for 30 min, and excess base was quenched by the addition of saturated aqueous ammonium chloride (100 mL). The reaction mixture was concentrated in vacuo to a volume of approximately 300 mL, and then diluted with ethyl acetate (250 mL). The mixture was washed with water (200 mL) and saturated aqueous sodium chloride (200 mL). The combined aqueous layers were further extracted with ethyl acetate (100 mL), and the combined organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (20% ethyl acetate in hexanes grading to 40% ethyl acetate in hexanes) afforded alcohols 23 (inseparable 1.3: 1 mixture of diastereomers, 27 .6 g, 81 %) as a pale yellow oil. 36 Major diastereomer: 4.35-3.80 (complex, 3H, OCH 2CHO), 2.22 (d, lH, J = 5.48 Hz, CHOH), 1.36 (s, 3H, C(CH) 2), 1.24 (s, 3H, C(CH 3 ) 2), 0.17 (s, 9H, Si(CH 3) 3). Minor diastereomer: 4.35-3.80 (complex, 3H, OCH 2CHO), 2.09 (d, lH, J = 5.84 Hz, CHOH), 1.42 (s, 3H, C(CH 3)i), 1.26 (s, 3H, C(CH 3)i), 0.17 (s, 9H, Si(CH 3)3). Major diastereomer: 110.4, 104.5, 90.40, 79.0, 66.4, 64.7, 26.9, 25.6, -0.1. Minor diastereomer: 110.2, 104.7, 90.3, 78.7, 65.9, 63.4, 26.6, 25.6, -0.1. FI1R (thin film), cm· 1: 3439 (s, OH), 2960 (s), 2898 (s), 2174 (m, C=C), 1374 (m), 1251 (s), 1215 (m), 1156 (m), 1068 (s), 884 (s), 761 (m). Calc'd for C 11 H21 0 3Si [MH] +: 229.1259982 Found: 229.1257000 TLC (20% EtOAc in Hexanes), Rf: . glyceraldehyde acetonide: 0.24 (anisaldehyde) 23: 0.59 (anisaldehyde) 37 Br2 , PPh3 , Im, TBS--==--.., OH TBS-==--.., Br CH2Cl2, 0 °C 25 26 81% 3-tert-Butyldimethylsilylpropargyl bromide (2 6) A solution of triphenylphosphine (56.8 g, 0.217 mol, 1.3 equiv), and imidazole (14.7 g, 0.217 mol, 1.3 equiv) in dichloromethane (350 mL) was cooled to 0 °C. Bromine (11.2 mL, 34.6 g, 0.217 mol, 1.3 equiv) was ad~ed in a dropwise manner over a period of 15 min. The resultant suspension was maintained at 0 °C for an additional 15 min, and then 3-tert-butyldimethylsilylpropargyl alcohol (25, 28.4 g, 0.167 mol, 1.0 equiv) in dichloromethane (150 mL) was added over a period of 30 min. The resultant suspension was maintained at 0 °C for an additional 15 min, and then pentane (500 mL) was added. The white suspension was filtered through a pad of Celite, and the filtrate was concentrated in vacuo. The residue was diluted with pentane (500 mL) and the filtration repeated. The filtrate was filtered through a plug of silica gel, and the silica was washed with 2: 1 pentane/diethyl ether (2 400-mL portions). The combined filtrates were concentrated in vacuo to provide a pink oil. Distillation under reduced pressure provided 3-tert- butyldimethylsilylpropargyl bromide (26) (31.6 g, 81 %, bp 102-103 °020 mm Hg) as a colorless oil. 38 3.92 (s, 2H, BrCH 2), SiC(CH 3)/CH 3) 2), 0.11 0.94 (s, (s, 9H, 6H, SiC(CH 3)/CH 3) 2). 13 C NMR (75 MHz, CDC13), 8: 100.5, 90.8, 26.0, 16.6, 14.8, -4.9. FTIR (thin film), cm· 1: 2953 (s), 2929 (s), 2857 (m), 2177 (w, C=C), 1471 (m), 1363 (m), 1251 (m), 1204 (m), 1037 (m), 839 (s), 824 (s), 776 (s), 681 (m). TLC (20% EtOAc in Hexanes), Rf 25: 0.30 (PMA) 26: 0.34 (PMA) 39 e '+' Br TBS -==--..,v TBS---=--, Br 26 PA'l3 27 96% {3-tert-Butyldimethylsilyl)propargyltriphenylphosphonium bromide {2 7) Triphenylphosphine (35.8 g, 0.137 mol, 1.3 equiv) was added in one portion to a solution of 3-tert-butyldimethylsilylpropargyl bromide (26, 24.5 g, 0.105 mol, 1.0 equiv) in benzene (180 mL). The resultant solution was stirred at 23 °C in the dark for 24 h, during which time a white precipitate formed. The precipitate was collected by filtration, washed with benzene (100 mL), and dried over phosphorous pentoxide to provide (3-tertbutyldimethylsilyl)propargyltriphenylphosphonium bromide (27) (49.8 g, 96%) as a white solid, mp 210 °C (dee). 1 H NMR (400 MHz, DMSO-d6 ) o: 7.94 (m, 3H, P(C 6 H 5 ) 3), 7.81 (m, 12H, P(C 6 H 5 ) 3 ), 5.13 (d, 2H, J = 16.48 Hz, PCH ) , 0.66 (s, 9H, SiC(CH )iCH 2 3 -0.05 (s, 6H, SiC(CH )iCH 3 ) 3 ) . 2 ) 3 ) , 2 40 C NMR (100 MHz, DMSO-d6), o: 13 135.2 (s), 133.6 (d, J = 10.2 Hz), 130.0 (d, J = 12.2 Hz), 117.5 (d, J = 87.2 Hz), 95.3 (d, J = 13.0 Hz), 90.7 (d, J = 8.4 Hz), 25.4 (s), 16.4 (d, J = 53.3 Hz), 15.8 (s), -5.28 (s). FI1R (thin film), cm- 1: 2982 (m), 2816 (m), 1439 (m), 1250 (m), 1113 (m), 919 (m). HRMS (FAB): Calc'd for C27 H 32PSi [M-Brt: 415.2010931 Found: 415.2021000 TLC (20% EtOAc in Hexanes), Rf: 26: 0.34 (PMA) 27: 0.00 (UV, PMA) 41 PDC,AcOH, 3A MS, CH2Cl2 23 24 i. KN(TMS)2 , THF, -,-78 °c; 0 '+' Br ii. 24, -78➔ -40 ➔ -15 °C TBS--==-~,,;:;; PPh3 79% (two steps) 27 TBS H3 c >o••· ( O ~ aH H3C - 4 1fi1/ ~~s TMS TBS + TMS 28 (ca. 3:1) Bis-silyl enediynes 2 8 Pyridinium dichromate (43.0 g, 0.115 mol, 1.5 equiv) was added in one portion to a rapidly stirring suspension of propargylic alcohols 23 (17.46 g, 76.47 mmol, 1.0 equiv) in dichloromethane (380 mL) and crushed, activated 3A MS (52 g). Glacial acetic acid (7.4 mL, 7.8 g, 130 mmol, 1.7 equiv) was added via syringe, and the resultant brown suspension was stirred vigorously at 23 °C for 1.5 h. Celite (35g) was added, and the reaction mixture stirred for an additional 25 min. The reaction mixture was filtered through a plug of Celite and the filter cake washed with dichloromethane (400 mL). The filtrate 42 was diluted with heptane (1200 mL) and concentrated to a volume of ca. 300 mL. The concentrate was diluted with 2:1 pentane/diethyl ether (1200 mL) and filtered through a plug of anhydrous magnesium sulfate. The filtrate was washed with water (2 300-mL portions) and saturated aqueous sodium bicarbonate (2 300-mL portions). The organics were then dried over magnesium sulfate and concentrated to a volume of ca. 250 mL. Anhydrous tetrahydrofuran (400 mL) was added and the solution was again concentrated to ca. 250 mL. This procedure was repeated twice more, and the final concentrate was diluted to a volume of ca. 400 mL with anhydrous tetrahydrofuran. The crude propargylic ketone was stored at -20 °C under an argon atmosphere for later use. A solution of potassium hexamethyldisilazide (17.7 g of 95% solid, 84.1 mmol, 1.1 equiv) in toluene (140 mL) was added over a period of 50 min to a suspension of 3(tert-butyldimethylsilyl)propargyltriphenylphosphonium bromide (27, 43.6 g, 87 .9 mmol, 1.15 equiv) in tetrahydrofuran (785 mL) at-78 °C. The resultant bright yellow suspension was held at-78 °C for an additional 15 min, and warmed to -40 °C. The suspension was kept at -40 °C for 2 h, and warmed to -15 °C. After five minutes at -15 °C, the crude propargylic ketone solution was added over a 45 min period, and the resultant orange solution was maintained at -15 °C for an additional 2 h. Excess base was quenched by addition of saturated aqueous ammonium chloride (200 mL), and the layers separated. The aqueous layer was extracted with pentane (2 250-mL portions), and the combined organics were washed with water (2 300-mL portions) and saturated aqueous sodium chloride (300 mL). The organics were dried over sodium sulfate and were concentrated. Purification of the residue by flash column chromatography (hexanes grading to 3% ethyl acetate in hexanes) afforded a ca. 3: 1 mixture of enediynes 28 (22.38 g, 79%) as an orange oil. 43 Major diastereomer: 6.16 (s, lH, C4 H), 4.34 (t, lH, J = 6.96 Hz, C7 H), 3.90 (m, 2H, C8 CH 2), 1.39 (s, 3H, C(CH 3}i), 1.29 (s, 3H, C(CH 0.25 ) 3 1.11 (s, 9H, SiC(CH )iCH ) , 2 3 9H, (s, Si(CH 3) 3), 0.19 ) 3 (s, ) , 2 6H, SiC(CH 3 )iCH 3) 2). Minor diastereomer: 6.06 (s, lH, C4 H), 5.55 (t, lH, J = 6.60 Hz, C7 H), 4.13 (dd, lH, J = 7.68, 6.96 Hz, C8 H), 4.02 (t, lH, J = 7.72 Hz, C_8 H), 1.62 (s, 3H, C(CH 3)2), 1.44 (s, 3H, C(CH 3) 2), 0.98 (s, 9H, SiC(CH 3)/CH 3) 2 ), 0.24 (s, 9H, Si(CH 3) 3), 0.09 (s, 6H, SiC(CH3) 3(CH 3) 2). Major diastereomer: 134.9, 116.3, 116.2, 110.4, 104.0, 103.4, 101.5, 101.1, 77.6, 77.5, 68.2, 26.5, 26.3, 16.8, -0.0, -0.1. Minor diastereomer: 130.1, 118.8, 118.7, 100.3, 105.5, 102.9, -101.7, 101.4, 75.1, 75.0, 68.4, -4.4, -4.7. 68.3, 26.1, -4.3, 44 FTIR (thin film), cm· 1: 2955 (s), 2931 (s), 2886 (m), 2858 (m), 2144 (m, C=C), 1469 (m), 1372 (m), 1251 (s), 1154 (m), 1068 (s), 841 (s), 776 (m). HRMS (Cl, NH 3): Calc'd for C 20H35O2Si2 [MHr: 363.2175625 Found: 363.2177000 'JLC (20% EtOAc in Hexanes), Rf. 27: 0.20 (UV, anisaldehyde) 28: E: 0.40 (UV, anisaldehyde) Z: 0.48 (UV, anisaldehyde) 45 ?i TBS O H3cx H3C o••· 1. K:PO3, CH 3OH, o °C 2. 1NHCI, THF,23°C H /!/ \\\ TMS + 64% TBS TMS 28 (ca. 3:1) TBS + H TBS H 29 (64%) z and E Enediyne diols 2 9 Potassium carbonate (8.30 g, 59.8 mmol, 1.0 equiv) was added to a solution of bis silyl enediynes 28 (22.3 g, 59.8 mmol, 1.0 equiv) in methanol (300 mL) at 0 °C. The resultant yellow suspension was stirred vigorously at 0 °C for 45 min, and partitioned between pentane (500 mL) and water (200 mL). The layers were separated, and the aqueous layer was further extracted with pentane (3 200-mL portions). The combined organics were dried over sodium sulfate, and were concentrated. The residue was taken up in tetrahydrofuran (1500 mL) and IN aqueous HCl (1200 mL) was added. Tetrahydrofuran (ca. 500 mL) was added until the mixture was homogeneous, and the solution was then stirred at 23 °C for 18 h. The reaction mixture was concentrated in vacuo 46 to remove most of the tetrahydrofuran, and the concentrate was extracted with ethyl acetate (3 300-mL portions). The combined organics were washed with saturated aqueous sodium bicarbonate (200 mL) and saturated aqueous sodium chloride (200 mL). The organics were dried over sodium sulfate and were concentrated. The residue was purified by careful flash column chromatography (25% ethyl acetate in hexanes grading to ethyl acetate) to afford a mixture of olefin isomers (5.78 g, 36%) as a yellow oil along with pure E isomer 29 (9.51 g, 64%) as an off-white solid, mp 54 °C. For the Z isomer of 29: 5.93 (s, IH, C4 H), 4.95 (br s, lH, C7 H), 3.64 (m, 2H, C8 CH 2), 2.72 (s, IH, Cl H), 2.04 (br s, lH, OH), 1.52 (br s, lH, OH), LOO (s, 9H, OSiC(CH 3)/CH 3) 2), 0.12 (s, 6H, OSiC(CH 3MCH 3) 2). 136.5, 118.1, 106.0, 101.1, 85.6, 81.4, 72.0, 65.3, 26.3, 16.8, -4.6, -4.6. [a]~: FI1R (thin film), cm· 1: 3389 (s, OH), 3295 (s, C=C-H), 2952 (s), 2930 (s), 2857 (s), 2123 (m, C=C), 2092 (m, C=C), 1467 (m), 1251 (s), 1676 (s), 892 (m), 825 (s), 777 (s), 685 (s). 47 1LC (30% EtOAc in Hexanes), Rf. S. M.(after I<iCOJ 0.62 (UV, anisaldehyde) 29: 0.14 (UV, anisaldehyde) For the E isomer of 29: 6.17 (m, lH, C4 H), 3.91 (m, lH, C7 H), 3.53 (ddd, lH, J = 10.96, 7.32, 3.64 Hz, C8 H), 3.31 (ddd, lH, J = 11.72, 6.60, 5.12 Hz, C8 H), 2.98 (s, lH, Cl H), 1.15 (dd, lH, J = 7.72, 4.76 Hz, OH), 0.52 (br s, lH, OH), 1.10 (s, 9H, SiC(CH 3)iCH 3) 2), 0.22 (s, 6H, SiC(CH 3)/CH 3) 2). 134.9, 117.8, 103.4, 101.4, 87.2, 80.4, 74.4, 65.5, 26.4, 16.8, -4.4, -4.5. 3599 (m, OH), 3401 (m, OH), 3301 (m, C=C-H), 2954 (s), 2885 (m), 2857 (m), 2133 (m, C=C), 1468 (m), 1252 (s), 1080 (s), 1039 (s), 839 (vs), 826 (vs), 650 (m). HRMS (CI, NH 3): Calc'd for C 14H23 0 2 Si [MH] +: 251.1467336 Found: 251.1466000 48 TLC (30% EtOAc in Hexanes), Rf. S. M.(after ~CO 3): 0.62 (UV, anisaldehyde) 29: 0.10 (UV, anisaldehyde) 49 HO TDSCI, Et 3N, DMAP, HO=x CH2Cl2, 0 °C H 100% TDSO?i HO''' 1 /// TBS 29 H - 4 ~~ H TBS 30 IDS ether 30 tert-Butyldiphenylsilyl chloride (28.5 mL, 30.2 g, 0.122 mol, 2.4 equiv) was added via syringe to a solution of diol 29 (12.7 g, 50.8 mmol, 1.0 equiv), triethylamine (53.0 mL, 38.6 g, 0.381 mol, 7.5 equiv), and 4-dimethylaminopyridine (6.21 g, 50.8 mmol, 1.0 equiv) in dichloromethane (510 mL) at 0 °C. The resultant pale yellow solution was maintained at 0 °C for 1 h and excess silyl chloride was quenched by the addition of methanol (100 mL). The reaction mixture was poured into water (500 mL) and the layers were separated. The aqueous layer was further extracted with dichloromethane (200 mL) and the combined organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (25% ethyl acetate in hexanes) provided the IDS ether 30 (24.8 g, 100%) as a pale yellow oil. 50 7.73 (m, 4H, OSiC(CH 3)iC6H 5) 2), 7.25 (m, 6H, OSiC(CH 3MC 6H 5) 2 ), 6.33 (s, lH, C4 H), 4.18 (m, lH, C7 H), 3.88 (dd, lH, J = 10.24, 4.04 Hz, C8 H), 3.72 (dd, lH, J = 6.20, 4.04 Hz, C8 H), 2.90 (s, lH, Cl H), 2.30 (d, lH, J = 5.12 Hz, OH), 1.13 (s, 9H, OSiC(CH 3)iC 6H5) 2), 1.10 (s, 9H, OSiC(CH 3)/CH 3) 2), 0.21 (s, 6H, OSiC(CH 3)/CH 3) 2). 136.0, 135.9, 135.9, 135.2, 135.1, 133.9, 133.4, 130.1, 129.9, 128.1, 128.0, 117.3, 103.5, 101.1, 86.7, 80.4, 74.2, 66.9, 52.0, 27.0, 26.4, 19.4, 16.8, -4.4. FTIR (thin film), cm· 1: 3552 (w, OH), 3447 (w, OH), 3296 (m, C=C-H), 2951 (s), 2851 (s), 2135 (w, C=C), 1470 (m), 1250 (m), 1111 (s), 824 (s), 702 (s). HRMS (FAB): Calc'd for C 30H41 0 2Si2 [MHr: 489.2645127 Found: 489.2653000 1LC (30% EtOAc in Hexanes), Rf 29: 0.18 (UV, anisaldehyde) 30: 0.78 (UV, anisaldehyde) 51 TDSO e TDSO (-)-DET, Ti(Q,:.Pr)4, TBHP, HO=x H TBS 30 3A MS, CH2Cl2, -20 °C 94% H0,1\• H TBS 31 Epoxide 31 Titanium(IV) isopropoxide (21.0 mL, 20.0 g, 70.5 mmol, 1.40 equiv) was added dropwise to a solution of D-(-)-diethyl tartrate (12.6 mL, 15.2 g, 73.5 mmol, 1.46 equiv) and powdered, activated 4A molecular sieves (6g) in dichloromethane (150 mL) at -20 °C. The resultant mixture was allowed to age at -20 °C for 50 min, and IDS ether 30 (24.6 g, 50.3 mmol, 1.0 equiv) in dichloromethane (60 mL) was added over a period of 15 min. The reaction mixture was allowed to stir at -20 °C for another 30 min, and tert-butyl hydroperoxide (31 mL of a 4.7 M solution in dichloromethane, 0.146 mol, 2.9 equiv) was added via gastight syringe/feflon needle. The reaction mixture was held at -20 °C for an additional 20 h, and 10% aqueous D-tartaric acid (100 mL) was added. The resultant mixture was stirred vigorously at 23 °C for 30 min and filtered through a plug of celite. The filtrate layers were separated and the aqueous layer was further extracted with dichloromethane (3 50-mL portions). The combined organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (8% ethyl acetate in hexanes) afforded the epoxide 31 (24.0 g, 94%) as a pale yellow oil. 52 7.85 (m, 4H, OSiC(CH 3)iC 6H 5) 2), 7.28 (m, 6H, OSiC(CH 3)iC 6H 5) 2), 3.94 (dd, lH, J = 11.00, 2.92 Hz, C8 H), 3.90 (s, lH, C4 H), 3.84 (dd, lH, J = 10.96, 2.56 Hz, C8 H), 3.60 (m, lH, C7 H), 2.00 (s, lH, Cl H), 1.79 OH), 1.21 (s, 9H, OSiC(CH 3MC 6H5) 2), 1.05 (s, 9H, OSiC(CH 3MCH 3) 2 ), 0.17 (s, 6H, (m, lH, OSiC(CH 3MCH 3) 2 ). 136.1, 135.8, 135.2, 133.4, 133.3, 130.0, 129.8, 128.5, 128.1, 101.0, 90.5, 78.9, 75.7, 71.3, 64.3, 58.2, 48.7, 27.1, 26.3, 19.4, 16.6, -4.6. FTIR (thin film), cm· 1: 3480 (m, OH), 3306 (m, C=C-H), 2954 (s), 2930 (s), 2886 (m), 2857 (s), 2185 (w, C=C), 2125 (w, C=C), 1470 (m), 1427 (m), 1251 (m), 1113 (s), 12079 (s), 985 (m). HRMS (FAB): Calc'd for C30H41 0 3Si2 [MH] +: 505.2594274 Found: 505.2581000 1LC (20% EtOAc in Hexanes), Rf 30: 0.49 (UV, anisaldehyde) 31: 0.40 (anisaldehyde) 53 TOSO H01' H TBS 92% 31 32 Diol epoxide 3 2 Triethylamine trihydrofluoride (14.5 mL, 14.4 g, 89.0 mmol, 3 equiv) was added via syringe to a solution of epoxide 31 (15.0 g, 29.7 mmol, 1.0 equiv) in tetrahydrofuran (370 mL) at 23 °C. The solution was maintained at 23 CC for 20 h, and saturated aqueous sodium bicarbonate (300 mL) was added to quench excess acid. The layers were separated and the aqueous layer was further extracted with ethyl acetate (2 100-mL portions). The combined organics were washed with saturated aqueous sodium chloride (100 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (10% ethyl acetate in hexanes grading to ethyl acetate) provided diol epoxide 32 (7.27 g, 92%) as a pale yellow solid, mp 78 °C. 3.66 (m, lH, C8 H), 3.58 (s, lH, C4 H), 3.51 (m, 2H, C7, C8 H), 1.97 (s, lH, Cl H), 1.78 (br s, lH, OH), 1.44 (br s, lH, OH), 1.03 (s, 9H, SiC(CH 3)/CH 3) 2), SiC(CH 3 )/CH 3) 2). 0.15 (s, 6H, 54 100.8, 90.7, 78.4, 76.2, 72.0, 63.4, 58.0, 48.8, 26.2, 16.6, -4.4. FTIR (thin film), cm· 1: 3591 (m, OH), 3304 (s, C=C-H), 3018 (m), 2931 (s), 2858 (m), 2190 (w, C=C), 2131 (w, C=C), 1468 (m), 1363 (m), 1252 (s), 1103 (s), 1079 (s), 1055 (s), 1038 (s), 828 (vs), 654 (m). HRMS (Cl, NH 3): Calc'd for C 14H 23 O3Si [MH] +: 267.1416482 Found: 267.1427000 1LC (50% EtOAc in Hexanes), Rf. 31: 0.56 (anisaldehyde) 32: 0.19 (anisaldehyde) 55 HO 2-methoxypropene, p-TsOH, DMF, 23 °C HO'li 82% H TBS 32 20 Acetonide 2 Q 2-Methoxypropene (2.15 mL, 1.62 g, 22.5 mmol, 1.2 equiv) and p-toluenesulfonic acid (500 mg) were added sequentially to a solution of diol epoxide 32 (5.00 g, 18.8 mmol, 1 equiv) in DMF (38 mL). The resultant pale yellow solution was maintained at 23 °C for 6 hand partitioned between hexanes (200 mL) and water (100 mL). The aqueous layer was extracted with hexanes (100 mL) and the combined organics were washed with water (3 100-mL portions) and saturated aqueous sodium chloride (100 mL). The organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (10% ethyl acetate in hexanes) provided the acetonide 20 (4.69 g, 82%) as a white solid, mp 43-44 °C. 56 3.99 (dd, lH, J = 8.80, 6.24 Hz, C7 H), 3.79 (dd, lH, J = 8.76, 6.60 Hz, C8 H), 3.64 (t, lH, J = 6.60 Hz, C8 H), 3.47 (s, lH, C4 H), 1.98 (s, lH, Cl H), 1.37 (s, 3H, C(CH 3)2), 1.19 (s, 3H, C(CH 3 ) 2 ), 1.03 (s, 9H, SiC(CH 3)iCH 3) 2 ), 0.15 (s, 3H, SiC(CH 3)iCH 3) 2), 0.14 (s, 3H, SiC(CH 3)iCH 3) 2). 110.7, 100.5, 90.6, 78.1, 76.7, 75.4, 66.8, 58.1, 50.1, 50.0, 26.2, 25.4, 16.7, -4.8. FfIR (thin film), cm· 1: 3281 (m, C::=C-H), 2953 (s), 2931 (s), 2184 (w, C=C), 2125 (w, C=C), 1464 (m), 1374 (m), 1254 (s), 1215 (m), 1154 (m), 1076 (s), 828 (s). HRMS (Cl, NH 3): Calc'd for C17H27 0 3Si [MH] +: 307 .1729484 Found: 307.1722000 TLC (20% EtOAc in Hexanes), Rf. 32: 0.025 (anisaldehyde) 20: 0.44 (anisaldehyde) 57 6 TBSO~ i. PhSeTMS, TMSOTf, CH 2C'2, -78 °C 0 ii. HC(OCH3h, -25 ➔ -20 °C _A.,;, CH(OCH3h iii. HP2o Py, -20 °C (+)-33 sv TBSO~· 3 (+)-21 80% Enone (+)-21 Trimethylsilyl phenylselenide (0.794 mL, 1.08 g, 4.71 mmol, 2 equiv) and trirnethylsilyl trifluoromethanesulfonate (0.0910 mL, 0.105 g, 0.471 mmol, 0.2 equiv) were added sequentially to a solution of enone (+)-33 (0.500 g, 2.35 mmol, 1 equiv) in dichloromethane (4.7 mL) at-78 °C. The colorless solution was maintained at -78 °C for an additional 20 min, and then freshly distilled trimethyl orthoformate ( 1.03 mL, 1.00 g, 9.42 mmol, 4 equiv) was added via syringe. After five min at -78 °C, the cloudy reaction mixture was warmed to -25 °C and allowed to warm to -20 °C over 45 min. During this time, examination of the reaction by thin-layer chromatography (20% ethyl acetate in hexanes) revealed the gradual disappearance of a spot at higher Rf than (+ )-33 which was visible by both UV irradiation and anisaldehyde staining (a non-staining higher Rf UVactive spot is unaffected). The complete disappearance of the spot and the return to clarity of the reaction mixture coincided (at approximately the 45 min mark), and at this juncture pyridine (0.050 mL) and 30% aqueous hydrogen peroxide (3 mL) were added to the reaction mixture at-20 °C. The reaction mixture darkened slightly over the next 3-5 min, at which time a rapid reaction occurred in which a precipitate formed and the reaction decolorized. The reaction mixture was warmed to 23 °C and diluted with I: I ethyl acetate/hexanes (10 mL). The mixture was washed with water (10 mL) and saturated 58 aqueous sodium chloride (10 mL). The organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (10% ethyl acetate in hexanes grading to 13% ethyl acetate in hexanes) afforded (+)-21 (0.536 g, 80%) as pale yellow needles, mp 29.5-30.5 °C. 7.41 (d, lH, J = 1.44 Hz, C3 H), 5.24 (s, lH, CH(OCH 3) 2 ), 4.38 (m, lH, C4 H), 3.21 (s, 3H, CH(OCH 3)2), 3.14 (s, 3H, CH(OCH 3)2), 2.42 (dd, lH, J = 18_28, 6.20 Hz, C5 ~H), 2.22 (dd, lH, J = 17.92, 2.20 Hz, C12 aH), 0.89 (s, 9H, OSiC(CH 3) 3(CH 3) 2), -0.04 (s, 3H, OSiC(CH 3MCH) 2), -0.06 (s, 3H, OSiC(CH 3)iCH 3) 2). 201.9, 159.2, 143.6, 97.6, 69.1, 53.6, 53.0, 46.0, 25.9, 18.1, -4.7. FI1R (thin film), cm- 1: 2953 (m), 2930 (m), 2856 (m), 1718 (s, C=O), 1472 (w), 1388 (w), 1215 (m), 1059 (m), 835 (m)_ HRMS (CI, NH 3): Calc'd for C 14H27 0 4Si [MH] +: 287.1664000 Found: 287.1678630 59 TLC (20% EtOAc in Hexanes), Rf. (+)-33: 0.31 (anisaldehyde) (+)-21 : 0.42 (anisaldehyde) 60 ~H 6 ~- kO 34 OPiv PivCI, Et3N, DMAP, so CH2Cl2, O °C 99% 3 Ao::/· 36 Pivaloate ester 3 6 Pivaloyl chloride (8.45 mL, 8.27 g, 68.6 mmol, 1.5 equiv) was added dropwise via syringe to a solution of monoacetate 34 (6..50 g, 45.7 mmol, 1 equiv), triethylamine (32.0 mL, 23.0 g, 228 mmol, 5 equiv) and 4-dimethylaminopyridine (2.79 g, 22.8 mmol, 0.5 equiv) in dichloromethane (300 mL) at 0 °C. The resultant solution was stirred at 0 'C for an additional 2 h, and then poured into 1:1 ethyl acetate/hexanes (300 mL). The mixture was washed with water (300 mL) and saturated aqueous sodium chloride (300 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (10% ethyl acetate in hexanes) provided pivaloate ester 36 (10.5 g, quantitative) as a colorless oil. 6.07 (s, 2H, C2, C3 H), 5.53 (m, 2H, Cl, C4 H), 2.88 (dt, lH, J = 15.04, 7.72 Hz, C5 H), 2.06 (s, 3H, 0 2CCH 3 ) , 1.67 (dt, lH, J = 14.68, 4.04 Hz, C5 H), 0 2 CC(CH 3) 3). 1.19 (s, 9H, 61 13 C NMR (100 MHz, CDC1 3), o: 177.6, 170.1, 134.4, 134.1, 76.3, 76.0, 38.2, 37.0, 26.8, 20.7. FTIR (thin film), cnf 1: 2973 (m), 1728 (s, C=O), 1480 (w), 1367 (m), 1281 (m), 1238 (s), 1154 (s), 1026 (m). HRMS (FAB): Calc'd for C1 2H1 9O4 [MHt: 227.128334 Found: 227.127121 TLC (50% EtOAc in Hexanes), Rf: 34: 0.20 (anisaldehyde) 36: 0.60 (anisaldehyde) 62 9Piv 0 ,• Ar:£) 36 OPiv K2 C03 , CH 30H 23°c 88% sO ,•· HO 3 37 Allylic alcohol 3 7 Potassium carbonate (1.94 g, 14.1 mmol, 1 equiv) was added in one portion to a solution of pivaloate ester 36 (3.18 g, 14.1 mmol, 1 equiv) in methanol (28 mL) at 23 °C. The resultant suspension was stirred vigorously for 15 min, and poured into water (50 mL). The mixture was extracted with ethyl acetate (3 50-mL portions). ·Toe combined extracts were washed with saturated aqueous sodium chloride (50 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (30% ethyl acetate in hexanes) afforded allylic alcohol 37 (2.19 g, 85%) as a colorless oil. 5.79 (app. d, lH, J = 5.48 Hz, C2 H), 5.75 (app. d, lH, J = 5.84 Hz, C3 H), 5.47 (m, lH, Cl H), 4.25 (br d, J = 5.12 Hz, C4 H), 2.53 (dt, lH, J = 14.64, 7.32 Hz, C5 H), 1.57 (dt, lH, J = 14.28, 4.76 Hz, CS H), 1.24 (td, lH, J = 6.92, 4.76 Hz, OH), 1.17 (s, 9H, 0 2CC(CH 3\). 63 13 C NMR ( 100 MHz, CDC1 3), 6: 178.3, 138.2, 132.2, 76.8, 74.4, 40.4, 38.4, 26.9. 3408 (m, OH), 2975 (m), 1725 (s, C=O), 1480 (m), 1282 (s), 1157 (s), 1058 (m), 1031 (m). HRMS (El): Calc'd for C 10H 16O 3 [Mt: 184.109945 Found: 184.109889 TLC (50% EtOAc in Hexanes), Rf: 36: 0.58 (anisaldehyde) 37: 0.35 (anisaldehyde) 64 OPiv ~Piv 0 TBSCI, Et3 N, DMAP, 50 HO._,. ..:· TBSO 37 88% 3 38 TBS Ether38 tert-Butyldimethylsilyl chloride (4.20 g, 27.8 mmol, 2.5 equiv) was added in one portion to a solution of allylic alcohol 37 (2.05 g, 11.1 mmol, 1 equiv), triethylamine (7.75 mL, 5.63 g, 55.6 mmol, 5 equiv), and 4-dimethylaminopyridine (0.68 g, 5.56 mmol, 0.5 equiv) in dichloromethane (110 mL) at O 0 C. The resultant solution was allowed to gradually warm to 23 °C over 2 h and was stirred at 23 °C for an additional 12 h. The reaction mixture was diluted with 1:1 ethyl acetate/hexanes (100 mL), and washed with water (100 mL), aqueous lN HCl (2 100-mL portions), saturated aqueous sodium bicarbonate (100 mL), and saturated aqueous sodium chloride (100 mL). The organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (10% ethyl acetate in hexanes) afforded TBS ether 38 (3.07 g, 92%) as a white solid, mp 64-66 °C. 65 5.84 (apparent qt, 2H, J = 8.44, 1.48 Hz, C2, C3 H), 5.57 (apparent t, lH, J = 5.84 Hz, Cl H), 4.44 (apparent t, lH, J = 5.48 Hz, C4 H), 2.66 (dt, lH, J = 13.52, 7.32 Hz, C5 H), 1.77 (dt, lH, J = 13.56, 5.48 Hz, C5 H), 1.19 (s, 0 2CC(CH 3) 3), 0.97 (s, 9H, OSiC(CH 3)iCH 3) 2 ), 0.05 (s, 3H, OSiC(CH 3)iCH 3) 2), 0.04 (s, 3H, 9H, OSiC(CH 3) 3(CH) 2). 13 C NMR (100 MHz, CDC1 3), 8: 178.2, 138.5, 131.4, 76.6, 74.8, 41.2, 38.5, 27.0, 25.8, 18.1, -4.7. 2957 (m), 1728 (s, C=O), 1477 (w), 1371 (m), 1282 (m), 1254 (m), 1157 (s), 1050 (m), 837 (m). HRMS (El): Calc'd for C 16H31 0 3Si [MH] +: 299.204249 Found: 299.203845 1LC (50% EtOAc in Hexanes), Rf 37: 0.40 (anisaldehyde) 38: 0.77 (anisaldehyde) 66 OPiv 0 TBSO' 38 DIBAL, PhCH 3 , -78 °C 99% ?H ·50 TBSO,· 3 39 Allylic alcohol 3 9 Diisobutylaluminum hydride (13.09 mL of a 1.5 M solution in toluene, 19.63 mmol, 2.0 equiv) was added via syringe to a solution of TBS ether 38 (2.93 g, 9.81 mmol, 1 equiv) in toluene (98 mL) at-78 °C. The resultant solution was maintained at -78 °C for an additional 10 min, and methanol (10 mL) was added and the solution warmed to 0 °C. After stirring at 0 °C for 20 min, 10% aqueous potassium sodium tartrate (20 mL) was added, and the reaction mixture was warmed to 23 CC and stirred vigorously for 25 min. The reaction mixture was diluted with water (30 mL) and extracted with ethyl acetate (3 30mL portions). The combined extracts were washed with water (50 mL) and saturated aqueous sodium chloride (50 mL), dried over sodium sulfate, and concentrated. Purification of the residue by flash column chromatography (10% ethyl acetate in hexanes grading to 20% ethyl acetate in hexanes) provided allylic alcohol 39 (2.10 g, 100%) as a colorless oil. 67 5.76 (m, 2H, C2, C3 H), 4.43 (m, 2H, Cl, C4 H), 2.46 (dt, lH, J = 13.41, 7.12 Hz, C5 H), 1.56 (dt, lH, J = 13.41, 5.01 Hz, C5 H), 1.41 (br s, lH, OH), 0.99 (s, 9H, OSiC(CH 3\(CH 3)), 0.08 (s, 3H, OSiC(CH 3)iCH 3) 2), 0.07 (s, 3H, OSiC(CH 3)iCH 3) 2). 13 C NMR (100 MHz, CDC1 3), o: 136.7, 135.7, 75.1, 74.9, 44.5, 25.8, 18.1, -4.7. FTIR (thin film), cm· 1: 3353 (m, OH), 2955 (s), 2931 (s), 2857 (s), 1470 (m), 1365 (m), 1253 (m), 1071 (s), 1021 (m), 904 (m), 836 (m), 777 (s). HRMS (El): Calc'd for CuH 23 0 2Si [MHr: 215.146734 Found: 215.146993 TLC (30% EtOAc in Hexanes), Rf: 38: 0.67 (anisaldehyde) 39: 0.33 (anisaldehyde) 68 ,6 OH 88% 39 ~- TBSO 3 (+)-33 Enone (+)-3 3 A 250 rnL round bottom flask was charged with allylic alcohol 36 (2.00 g, 9.33 mmol, 1.0 equiv) and dichloromethane (62 mL). Pyridinium chlorochromate (3.42 g, 15.9 mmol, 1.7 equiv) was added portionwise over a period of ca. 5 min. The resultant brown suspension was stirred at 23 °C for 1.5 h, and the reaction mixture was filtered through a plug of celite. The filtrate was concentrated, and the residue was purified by flash column chromatography (15% ethyl acetate in hexanes) to afford enone (+)-33 (1.74 g, 88%) as a colorless solid, mp 30-31 °C. All analytical data were in accord with that previously reported, except the optical rotation. +68.00° (c 1.00, CH 3OH) 69 t-Butyl acrylate, Et 3 N, P( o-tofh, Pd(OAch, 108 °C H3CO~ s 3~0t-Bu 89% 40 CH 3 3 0 41 ten-Butyl ester 41 tert-Butyl acrylate (37.0 mL, 32.0 g, 0.252 mol, 1.75 equiv), 4-bromo-3- methylanisole (40, 29 g, 0.144 mol, 1 equiv), triethylamine (35.0 mL, 25.5 g, 0.252 mol, 1.75 equiv), tri-o-tolylphosphine (10.5 g, 0.0340 mol, 0.24 equiv), and palladium diacetate (1.29 g, 5.76 mmol, 0.04 equiv) were combined in a 250 mL thick-walled flask. A stream of argon gas was bubbled through the solution for a period of 20 min, and the flask was sealed, covered with aluminum foil, and heated to 108 °C for 12 h. The reaction was cooled to 23 °C and dissolved in 10% aqueous sodium hydroxide (300 mL). The mixture was extracted with diethyl ether (2 450-mL portions) and the combined extracts were washed with saturated aqueous sodium chloride (300 mL). The organic layer was dried over sodium sulfate and was concentrated. Purification of the residue by flash column chromatography (2% ethyl acetate in hexanes grading to 20% ethyl acetate in hexanes) afforded ester 41 (32.0 g, 89%) as a pale yellow solid, mp 39 °C. 70 7.83 (d, lH, J = 15.72 Hz, C3 H), 7.51 (d, lH, J = 8.40 Hz, C6' H), 6.72 (m, 2H, CS', C3' H), 6.20 (d, lH, J = 16.12 Hz, C2 H), 3.80 (s, 3H, C4' OCH 3), 2.42 (s, 3H, C2' CH 3), 1.53 (s, 9H, OC(CH 3) 3). 13 C NMR (100 MHz, CDC13), o: 166.8, 160.8, 140.7. 139.5, 127.8, 126.2, 118.5, 115.8, 112.0, 80.1, 55.2, 28.2, 20.0. FI1R (thin film), cm- 1: 2975 (m), 1704 (s, C=O), 1627 (m), 1603 (s), 1499 (m), 1366 (m), 1297 (m), 1256 (s), 1147 (s), 1046 (m), 980 (m), 863 (m). HRMS (FAB): Calc'd for C15 H20 0 3 [Mt: 248.141245 Found: 248.140587 TLC (20% EtOAc in Hexanes), Rf 41: 0.27 (UV, anisaldehyde) 71 H3C O ~ H3CO~s .0 # OH ~Ot-Bu CH 3 0 3 quantitative I CH 3 3 0 42 41 Acid 42 Trifluoroacetic acid (35 mL) was added in one portion to a solution of ester 4 1 (16.9 g, 68.0 mmol, 1 equiv) in dichloromethane (145 mL). The resultant pale yellow solution was maintained at 23 °C for 5 h, during which time the solution darkened to red/brown. The solution was concentrated and the residual trifluoroacetic acid was removed by dissolution in toluene (100 mL) and concentration in vacuo. This procedure was repeated twice. The pale yellow solid remaining was examined by 1H NMR and found to be ~95% pure acid 42 (13.47 g, quantitative, mp 180 °C), and was used directly without further purification. 12.24 (s, lH, OH), 7.73 (d, lH, J = 16.08 Hz, C3 H), 7.66 (d, lH, J = 8.44 Hz, C6' H), 6.82 (s, lH, C3' H), 6.79 (d, lH, J = 8.76 Hz, C5' H), 6.29 (d, lH, J = 15.76 Hz, C2 H), 3.76 (s, 3H, C4' OCH 3), 2.36 (s, 3H, C2' CH 3). 72 13 C NMR (100 MHz, CDC1 3), 6: 167.7, 160.5, 140.7, 139.2, 128.1, 125.4, 117.4, 115.7, 112.3, 55.1, 19.4. FTIR (thin film), cm•1: 2931 (w), 2825 (s) , 1686 (m, C=O), 1601 (s), 1334 (m), 1259 (s), 1102 (m), 937 (m), 807 (m). HRMS (FAB): Calc'd for C11 H 12O3 [Mt: 192.078644 Found: 192.078045 TLC (20% EtOAc in Hexanes), Rf: 41: 0.27 (UV, anisaldehyde) 42: 0.00 (UV, anisaldehyde) 73 i. COi, THF, 23 °C ii. magnesium monomethyl H3CO~ s 2 malonate, THF, 23 °c 3 78% 42 ~ 0 C H3 CH3 5 0 0 43 6-Keto ester 4 3 Carbonyldiimidazole (10.1 g, 62.4 mmol, 1.2 equiv) was added in one portion to a solution of acid 42 (10.0 g, 52.0 mmol, I equiv) in tetrahydrofuran (300 mL) at 23 °C. The solution was maintained at 23 °C for 8 h. At the same time, a separate flask was charged with monomethyl malonate (13.5 g, 0.114 mol, 2.2 equiv) and tetrahydrofuran and cooled to 0 0 C. Magnesium ethoxide (13.1 g, 0.114 mmol, 2.2 equiv) was added portionwise over a 5 min period. After completion of the addition, the reaction mixture was warmed to 23 °C and stirred vigorously for 3 h. The reaction mixture was concentrated in vacuo to afford a gray solid, which was powdered in the same flask using a stainless steel spatula. At the appropriate time (after the acylimidazole solution had been allowed to react for 8 h), the magnesium monomethyl malonate was cooled to 0 °C, and the acylimidazole solution was added via cannula over a ten-minute period. Upon completion of the addition, the reaction mixture was warmed to 23 °C and stirred for an additional 15 h. The reaction mixture was partitioned between IN hydrochloric acid (300 mL) and diethyl ether (300 mL). The aqueous layer was acidified to pH I with concentrated hydrochloric acid and the layers were separated. The aqueous layer was extracted with diethyl ether (2 100-mL portions), and the combined organics were washed with saturated aqueous sodium bicarbonate (250 mL), dried over sodium sulfate, and concentrated. 74 Purification of the residue by flash column chromatography (7% ethyl acetate in hexanes) afforded ~-keto ester 43 (10.10 g, 78%) as a colorless oil. 11.96 (s, lH, enol OH), 7.88 (d, 0.25 H, J = 16.12 Hz, C5 keto), 7.65 (d, lH, J = 15.72 Hz, C5 enol), 7.57 (d, 0.25 H, J = 8.40 Hz, C6' keto), 7.50 (d, 1 H, J = 8.44 Hz, C6' enol), 6.80-6.70 (complex, 2.5 H, C3', C5' enol, C3', C5' keto), 6.64 (d, 0.25 H, J = 16.12 Hz, C4 keto), 6.27 (dd, lH, J = 15.76, 1.88 Hz, C4 enol), 5.14 (s, lH, C2 enol), 3.83 (s, 0.75 H, COOCH 3 keto), 3.82 (s, 3H, COOCH3 enol), 3.77 (s, 3H, C4' OCH 3 enol), 3.76 (s, 0.75 H, C4' OCH 3 keto), 3.70 (s, 0.5 H, C2 keto), 2.44 (s, 0.75 Hz, C2' CH 3 keto), 2.42 (s, 3H, C2' CH 3 enol). 13 C NMR (100 MHz, CDC1 3), 8: 191.5, 173.2, 169.9, 167.9, 161.6, 141.8, 140.6, 139.0, 134.0, 128.2, 127.2, 125.5, 123.5, 120.4, 116.0, 115.8, 112.3, 112.0, 90.6, 55.2, 52.3, 51.1, 47.5, 19.9. FTIR (thin film), cm- 1: 2950 (w), 1743 (w), 1632 (m, C=O), 1599 (s), 1498 (m), 1444 (s), 1313 (m), 1255 (s), 1102 (w), 1147 (s), 1102 (w), 1037 (m), 803 (m). 75 HRMS (FAB): Calc'd for C 14H 17O4 [MH] +: 249.112684 Found: 249.112953 TLC (20% EtOAc in Hexanes), Rf 42: 0.00 (UV, anisaldehyde) 43: 0.45 (UV, anisaldehyde) 76 H:{: e "' O ~Cl 3 I .o 92% 43 : CH 3 .o OH OCH3 0 44 Chloro ester 4 4 Sulfuryl chloride (3.47 mL, 5.84 g, 43.3 mmol, 1.1 equiv) was added to a solution of ~-keto ester 43 (9.76 g, 39.3 mmol, 1 equiv) in benzene (240 mL). The yellow solution was heated to 66 °C for 50 min, and volatiles were removed in vacuo. Purification of the residue by flash column chromatography (20% ethyl acetate in hexanes) afforded chloro ester 44 (10.2 g, 92%) as a bright yellow solid, mp 93-96 °C. 12.31 (d, lH, J = 1.80 Hz, OH), 7.76 (d, lH, J = 15.40 Hz, C5 H), 7.61 (d, lH, J = 8.80 Hz, C6' H), 7.03 (dd, lH, J = 15.36, 1.44 Hz, C4 H), 6.76 (m, 2H, C3', C5' H), 3.89 (s, 3H, COOCH 3), 3.83 (s, 3H, C4' OCH 3), 2.44 (s, 3H, C2' CH 3). 13 C NMR (100 MHz, CDC1 3), 8: 170.2, 166.2, 160.9, 139.6, 136.8, 127.9, 126.9, 116.5, 115.9, 112.2, 96.6, 55.2, 52.8, 20.0. 77 2955 (m), 1638 (m), 1600 (s, C=O), 1560 (s), 1442 (s), 1355 (s), 1306 (s), 1208 (m), 1020 (m). HRMS (FAB): Calc'd for C 14H 15ClO4 [Mr: 283.073712 Found: 283.075798 TLC (40% EtOAc in Hexanes), Rf 43: 0.49 (UV, anisaldehyde) 44: 0.58 (UV, anisaldehyde) 78 0 H3CO~ ?I CH30H,23 °C ~OCH3 CH 3 OH OCH 3 hv, El:JN, 0 63% H3C O ~ O H w CH3 4 45 44 Methyl 2-hydroxy-7-methoxy-5-methyl-1-naphthoate (4 5) A large Pyrex photoreaction vessel was charged with chloro ester 44 (1.20 g, 4.24 mmol, 1 equiv), triethylamine (15.0 mL, 10.7 g; 106 mmol, 25 equiv), and methanol (800 mL). The vessel was equipped with a quartz photowell containing a Hanovia 450 watt medium pressure mercury arc lamp. The solution was deoxygenated by passing argon through the solution with a needle for 20 min, and then irradiated at 23 °C for 1 h. Volatiles were removed in vacuo, and the residue was purified by flash column chromatography (50% dichloromethane in hexanes) to afford methyl 2-hydroxy-7methoxy-5-methyl-1-naphthoate (45,551 mg, 53%) as a white solid, mp. 103-104 °C. 12.12 (s, lH, OH), 8.07 (s, lH, C8 H), 8.03 (d, lH, J = 9.16 Hz, C4 H), 7.04 (d, lH, J = 9.16 Hz, C3 H), 6.89 (s, lH, C6 H), 4.10 (s, 3H, CO 2CH 3), 3.92 (s, 3H, C7 OCH 3), 2.63 (s, 3H, C5 CH 3). 79 13 C NMR (100 MHz, CDC1 3), o: 172.7, 164.3, 159.3, 136.8, 134.1, 132.3, 123.0, 116.0, 104.6, 104.2, 55.0, 52.3, 19.9. FTIR (thin film), cm· 1: 2953 (w), 1641 (m, C=O), 1614 (m), 1436 (m), 1412 (m), 1318 (m), 1207 (s), 1171 (m), 1035 (m), 840 (m), 812 (m). HRMS (FAB): Calc'd for C 14H14O4 [Mt: 246.089209 Found: 246.087196 TLC (25% EtOAc in Hexanes), Rf: 44: 0.78 (UV, anisaldehyde) 45: 0.83 (UV, anisaldehyde) 80 0 OCH 3 w 0 H3C O ~ O H OH w H3CO~OH 91% CH3 CH 3 45 4 22 2-Hydroxy-7-methoxy-5-methyl-1-naphthoic acid (2 2) Sodium hydroxide (30.0 g, 0.758 mol, 75 equiv) was added portionwise over a five minute period to a solution of methyl 2-hydroxy-7-methoxy-5-methyl-1-naphthoate (45, 2.49 g, 10.1 mmol, 1 equiv) in methanol (69 mL) and water (23 mL) at 0 °C. The resultant solution was warmed to 80 °C for 10.5 h and cooled to 23 °C. The reaction mixture was poured into 500 mL cold (0 °C) 6N hydrochloric acid, and the precipitate was collected by filtration and dried, leaving 2-hydroxy-7-methoxy-5-methyl-1-naphthoic acid (22) as a pale orange/red solid (2.15 g, 91 %), mp 153-154 °C. The crude product could be recrystallized from toluene to afford yellow/orange needles. 7.97 (d, lH, J = 9.12 Hz, C4 H), 7.68 (s, lH, C8 H), 7.01 (d, lH, J = 9.12 Hz, C3 H), 6.89 (s, lH, C6 H), 3.80 (s, 3H, C7 OCH 3), 2.56 (s, 3H, C5 CH 3). 81 13 C NMR (100 MHz, DMSO-d6), o: 172.8, 160.1, 158.9, 137.1, 134.1, 130.7, 122.8, 116.3, 116.1, 109.4, 103.2, 55.4, 19.9. 2974 (rn), 2618 (rn), 1630 (s, C=O), 1444 (s), 1287 (s), 1247 (s), 1230 (s), 1022 (rn), 850 (m). HRMS (FAB): Calc'd for C 13H 12O4 [Mt: 232.073559 Found: 232.074749 1LC (25% EtOAc in Hexanes), Rf: 45: 0.83 (UV, anisaldehyde) 22: 0.00 (UV, anisaldehyde) 82 i. LiN(TMS)2 , PhCH 3 , -78 °C II HO,,.. 1 ii . (+)-21 75% t TBS 12 46 Alcohol 46 Lithium hexamethyldisilazide (12.4 mL of a 1.0 M solution in hexanes, 12.4 mmol, 1.05 equiv) was added in a dropwise manner to a solution of epoxy diyne 20 (3.79 g, 12.4 mmol, 1.05 equiv) in toluene (82 mL) at-78 °C. The resultant solution was maintained at -78 °C for an additional 25 min, and a solution of enone (+ )-21 (3.37 g, 11.8 mmol, 1.0 equiv) in toluene (20 mL) was added over a 30 min period. The reaction mixture was maintained at -78 °C for an additional 10 min, and excess base was quenched by the addition of saturated aqueous ammonium chloride (40 mL). The reaction mixture was warmed to 23 °C and the layers were separated. The aqueous layer was extracted with 1: 1 ethyl acetate/hexanes (3 50-mL portions), and the combined organics were washed with saturated aqueous sodium chloride (50 mL), dried over sodium sulfate, and concentrated. Purification of the residue by flash column chromatography (10% ethyl acetate in hexanes grading to 20% ethyl acetate in hexanes) afforded the tertiary alcohol 46 (5.20 g, 75%) as a pale yellow oil, along with recovered epoxy diyne (1.16 g, 30%). 83 6.19 (s, lH, ClO H), 5.44 (s, lH, C8 H), 4.89 (m, lH, Cll H), 4.10 (dd, lH, J = 8.40, 5.84 Hz, C13 H), 3.97 (s, lH, OH), 3.85 (dd, lH, J = 8.40, 6.56 Hz, C14 H), 3.63 (t, lH, J = 6.24 Hz, C14 H), 3.50 (s, lH, C5 H), 3.20 (s, 3H, CH(OCH 3) 2), 3.18 (obscured, lH, C12 H), 3.17 (s, 3H, CH(OCH 3 ) 2 ), 2.55 (dd, lH, J = 13.56, 5.12 Hz, C12 H), 1.45 (s, 3H, C(CH 3) 2), 1.19 (s, 3H, C(CH 3 ) 2 ) , 1.06 (s, 9H, SiC(CH 3 )/CH 3 ) 2 ) , 0.97 (s, 9H, SiC(CH 3 )iCH 3 ) 2 ), 0.21 (s, 3H, SiC(CH 3)/CH 3)J, 0.20 (s, 3H, SiC(CH 3 )/CH 3 ) 2 ) , 0.090 (s, 3H, SiC(CH 3 )/CH 3 ) 2 ) , 0.076 (s, 3H, SiC(CH 3)/CH 3) 2). 142.8, 136.0, 110.7, 100.6, 99.8, 90.8, 90.2, 77.6, 77.4, 75.4, 73.4, 66.9, 58.3, 52.7, 50.6, 26.3, 26.2, 25.9, 25.3, 18.2, 16.6, -4.5, -4.7. FTIR (thin film), cm- 1: 3520 (m, OH), 2955 (s), 2858 (s), 2252 (w, C=C), 1463 (m), 1372 (m), 1252 (m), 1076 (s), 839 (s), 777 (m). 84 HRMS (FAB): Calc'd for C 31 H52 O7Si2 [Mr: 591.320700 Found: 591.3173363 1LC (30% EtOAc in Hexanes), Rf. 20: 0.46 (anisaldehyde) (+)-21: 0.27 (anisaldehyde) 46: 0.19 (anisaldehyde) 85 II i TBS Bu4 NF, THF, O° C II i 99% TBSO.: 46 47 Diol 47 Tetrabutylammonium fluoride (29.79 mL of a 1.0 M solution in tetrahydrofuran, 29.79 mmol, 3 equiv) was added over a 4 min period to a solution of alcohol 46 (5.88 g, 9.93 mmol, 1 equiv) in tetrahydrofuran (200 mL) at 0 0 C. The resultant purple solution was stirred at 0 °C for an additional 30 min and poured into water (100 mL). The reaction mixture was extracted with ethyl acetate (3 75-mL portions), and the combined extracts were washed once with saturated aqueous sodium chloride (100 mL). The organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (50% ethyl acetate in hexanes grading to 80% ethyl acetate in hexanes) provided the diol 47 (3.62 g, quantitative) as a pale yellow oil. 86 6.05 (t, lH, J = 1.84 Hz, ClO H), 5.19 (t, lH, J = 1.44 Hz, C8 H), 4.70 (br s, lH, C11 H), 4.17 (dd, lH, J = 7.68, 5.88 Hz, C13 H), 4.02 (m, 2H, C14 CH 2), 3.76 (br s, lH, OH), 3.63 (d, lH, J = 1.48 Hz, C5 H), 3.60 (s, 3H, CH(OCH) 2), 3.42 (s, 3H, CH(OCH 3)2), 2.78 (dd, lH, J = 14.28, 6.96 Hz, C12 ~H), 2.54 (d, lH, J = 1.48 Hz, C7 H), 2.09 (dd, lH, J = 14.28, 3.64 Hz, C12 cx.H), 1.84 (br d, lH, J = 8.44 Hz, OH), 1.43 (s, 3H, C(CH 3}i), 1.32 (s, 3H_, C(CH 3) 2 ). 143.8, 135.4, 111.2, 100.7, 89.3, 78.2, 77.4, 76.3, 75.5, 75.0, 73.2, 67.1, 58.1, 54.4, 53.7 , 51.1, 49.7, 26.2, 25.2. FTIR (thin film), cm- 1: 3418 (m, OH), 3281 (m, C=C-H), 2947 (m), 2939 (m), 1374 (m), 1215 (m), 1106 (s), 1072 (s), 851 (m). HRMS (FAB): Calc'd for C 19 H23 0 7 [M-H] +: 363.1443000 Found: 363.1443784 1LC (50% EtOAc in Hexanes), Rf: 46: 0.72 (anisaldehyde) 47: 0.098 (anisaldehyde) 87 11 HO,,,. HO-i 31, DCC, 4-pyrrolidinopyridine, CH 2Cl2, O➔ 23 °C 10 7CP/o 47 Naphthoate ester 4 8 A solution of dicyclohexylcarbodiimide (200 mg, 0.972 mmol, 1.5 equiv) in dichloromethane (1 mL) was added via cannula to a solution of diol 47 (236 mg, 0.648 mmol, I equiv), naphthoic acid 22 (180 mg, 0.777 mmol, 1.2 equiv), and 4pyrrolidinopyridine (19.0 mg, 0.129 mmol, 0.2 equiv) in dichloromethane (6.5 mL) at 0 °C. The resultant solution was allowed to warm to 23 °C over a 4 h period, and was maintained at 23 °C for an additional 8 h. The precipitated dicyclohexylurea was removed by filtration, and the filtrate was concentrated. The concentrate was purified by flash column chromatography (30% ethyl acetate in haxanes grading to 40% ethyl acetate in hexanes) to afford the ester 48 (262 mg, 70%) as a colorless oil. 88 12.12 (s, lH, ArOH), 8.10 (s, lH, C8" H), 8.02 (d, J = 9.3 Hz, lH, C 4" H), 7.02 (d, lH, J = 9.3 Hz, C3" H), 6.87 (s, lH, C6" H), 6.28 (s, lH, ClO H), 6.01 (td, lH, J = 4.9, 4.0 Hz, Cll H), 5.29 (s, lH, C8 H), 4.234.06 (m, 3H, C13, C14 H), 3.86 (s, 3H, C7'' OCH 3), 3.77 (s, lH, C5 H), 3.67 (s, lH, OH), 3.46 (s, 3H, CH(OCH 3) 2), 3.42 (s, 3H, CH(OCH 3) 2), 3.11 (dd, lH, J = 15.0, 7 .3 Hz, C12 ~H), 2.61 (s, 3H, C5" CH 3), 2.58 (dd, lH, J = 15.0, 2.9 Hz, C12 aH), 2.52 (s, lH, C7 H), 1.49 (s, 3H, C(CH 3) 2 ), 1.37 (s, 3H, C(CH 3) 2). 203.3, 171.9, 164.6, 159.5, 147.0, 136.8, 134.2, 132.6, 130.2, 123.0, 116.8, 115.9, 111.1, 104.4, 100.3, 88.5, 77.7, 76.3, 76.0, 75.1, 74.9, 74.8, 66.9, 57.8, 55.3, 54.3, 53.7, 49.6, 47.4, 26.2, 25.1, 19.9. FTIR (thin film), cm· 1 3500(w, OH), 3281 (w, OH), 2990 (m), 2939 (m), 1644 (m, C=O), 1615 (m), 1207 (m), 1074 (m). HRMS (FAB): Calc'd for C32 H340 10 [Mr: 578.2165 Found: 578.2152 89 1LC (20% EtOAc in Hexanes), Rf 47: 0.08 (anisaldehyde) 48: 0.51 (fluoresces under UV, anisaldehyde) 90 11 HO,,,. 79'"/o Tetraol 49 Concentrated HCl (68 µL) was added dropwise via syringe to a solution of acetonide 48 (488 mg, 0.843 mmol, 1 equiv) in methanol (75 mL) at 0 0 C. The resultant solution was maintained at O °C for 2.5 h, and warmed to 23 °C for 9.5 h. The solution was cooled to 0 °C and quenched with saturated sodium bicarbonate (25 mL). The reaction was concentrated to approximately half volume and partitioned between 1: 1 ethyl acetate/hexanes (50 mL) and water (50 mL). The aqueous layer was extracted with ethyl acetate (2 25-mL portions), and the combined extracts were washed once with saturated aqueous sodium chloride (50 mL). The organics were dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (40% ethyl acetate in hexanes grading to 100% ethyl acetate) to afford the tetraol 49 (360 mg, 79%) as a pale yellow oil. 91 1 H NMR (400 MHz, CDC1 3), 6: 12.10 (s, lH, ArOH), 8.08 (d, lH, J = 2.4 Hz, C8" H), 8.02 (d, lH, J = 9.2 Hz, C4" H), 7.01 (d, lH, J = 9.2 Hz, C3" H), 6.86 (d, lH, J = 2.4 Hz, C6" H), 6.29 (s, lH, ClO H), 6.01 (td, lH, J = 3.9, 2.9 Hz, Cl 1 H), 5.26 (s, lH, C8 H), 3.91 (m, 3H, C13, C14 H), 3.86 (s, 3H, CT' OCH 3), 3.83 (s, lH, OH), 3.76 (d, lH, J = 1.4 Hz, C5 H), 3.46 (s, 3H, CH(OCH 3)i}, 3.42 (s, 3H, CH(OCH 3) 2), 3.10 (dd, lH, J = 14.6, 7.3 Hz, C12 ~H), 2.60 (s, 3H, CS" CH 3), 2.58 (dd, lH, J = 14.6, 3.4 Hz, C12 CXH), 2.53 (d, lH, J = 1.4 Hz, C7 H), 2.20 (br s, lH, OH). 13 C NMR (100 MHz, CDC1 3), 6: 171.9, 164.6, 159.5, 146.8, 136.8, 134.2, 132.6, 130.6, 123.0, 116.7, 115.9, 104.3, 103.6, 100.2, 89.1, 78.1, 77.9, 77.5, 76.2, 75.1, 74.9, 71.4, 63.1, 57.5, 55.2, 54.4, 53.4, 48.5, 47 .5. FfIR (thin film), cm- 1: 3418 (s, OH), 3296 (s, OH), 2901 (m), 1644 (s, C=O), 1614 (s), 1207 (s), 1052 (s). HRMS (FAB): Calc'd for C29 H300 10 [Mr: 538.1856 Found: 538.1839 92 TLC (75% EtOAc in Hexanes), Rf 48: 0.87 (fluoresces under UV, anisaldehyde) 49: 0.28 (fluoresces under UV, anisaldehyde) 93 HO II 0.$ II COi, THF; (±)-CSA, HO,,,_ i1 H CHO CH3CN/H 2 0 (1:1), 23 °C, 80% 0 0 0.$ w H3CO~OH H3CO~OH ~ CH3 CH 3 49 4' 50 Carbonate 5 Q Carbonyldiimidazole (38.0 mg, 0.232 mmol, 0.65 equiv) was added in one portion to a solution of tetraol 49 (192 mg, 0.357 mmol, 1 equiv) in dry TI-IF (7 mL) at 0 0 C. The resultant solution was stirred at 0 °C for 20 min, then another portion of carbonyldiimidazole (38.0 mg, 0.232 mmol, 0.65 equiv) was added. The reaction mixture was maintained at 0 °C for an additional 10 min, then warmed to 23 °C and held at that temperature for 2 h. The reaction mixture was diluted with ethyl acetate (25 mL) and washed with water (2 10-mL portions) and saturated aqueous sodium chloride (10 mL). The organics were dried over sodium sulfate and concentrated. The residue was dissolved in 1:1 acetonitrile/water (26 mL). (±)-Camphorsulfonic acid (325 mg) was added in one portion and the reaction mixture was stirred at 23 °C for 11 h. The reaction mixture was extracted with ethyl acetate (3 50-mL portions). The combined organics were washed with saturated aqueous sodium chloride (50 mL), dried over sodium sulfate and concentrated. 94 Purification of the residue by flash column chromatography (50% ethyl acetate in hexanes) provided the carbonate 50 (153 mg, 80%) as a colorless film. 12.00 (s, lH, ArOH), 9.89 (s, lH, C8 H), 8.05 (d, lH, J = 9.3 Hz, C4" H), 7.98 (s, lH, C8" H), 7.03 (d, lH, J = 9.3 Hz, C3" H), 7.10 (d, lH, J = 2.0 Hz, ClO H), 6.89 (s, lH, C6" H), 6.22 (m, lH, Cl 1 H), 4.62 (m, 2H, C14 H), 4.35 (dd, lH, J = 7.8, 4.9 Hz, C13 H), 3.85 (s, 3H, CT' OCH 3), 3.67 (d, lH, J = 1.5 Hz, C5 H), 3.64 (s, lH, OH), 3.30 (dd, lH, J = 14.2, 7.8 Hz, C12 ~H), 2.62 (d, lH, J = 1.5 Hz, C7 H), 2.62 (s, 3H, CS" CH 3), 2.62 (dd, lH, J = 14.2, 4.8 Hz, C12 aH). FI1R (thin film), cm- 1: 3448 (w, OH), 3271 (w, OH), 2919 (w), 1818 (s, carbonate C=O), 1686 (m, C=O), 1616 (s, C=O), 1204 (s), 1084 (s). HRMS (FAB): Calc'd for C28 H22 NaO 10 [M+Nar: 541.1110 Found: 541.1094 lLC (50% EtOAc in Hexanes), Rf: 49: 0.00 (fluoresces under UV, anisaldehyde) 50: 0.31 (UV, anisaldehyde) 95 o=<..o 0'' 11 H CHO .; 0 II ~ TMSOTf, 2,6-lutidine, HO,,.. CH 2C'2, -78 °C 1 H CHO 12 91% 0 TMSO,,.. 1 .; 0 0 w H3C O ~ O H H3C O ~ O H CH 3 CHa yu 50 4• 51 TMS ether 51 2,6-Lutidine (0.573 mL, 527 mg, 4.92 mmol, 10 equiv) and trimethylsilyl trifluoromethanesulfonate (0.571 mL, 656 mg, 2.95 mmol, 6 equiv) were added sequentially via syringe to a solution of carbonate 50 (236 mg, 0.492 mmol, 1 equiv) in dichloromethane (30 mL) at-78 cc. The resultant solution was maintained at-78 cc for an additional 75 min, and excess trimethylsilyl trifluoromethanesulfonate was neutralized by the addition of triethylamine (0.1 mL) and methanol (0.1 mL). The reaction mixture was warmed to 23 °C and diluted with 1: 1 ethyl acetate/hexanes (50 mL). The mixture was washed with water (50 mL), 5% aqueous citric acid (3 25-mL portions) and saturated aqueous sodium chloride (50 mL). The organics were then dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (25% ethyl acetate in hexanes) afforded silyl ether 51 (264 mg, 91 %) as a light orange oil. 96 11.95 (s, lH, ArOH), 9_84 (s, lH, C8 H), 8.04 (d, lH, J = 9.2 Hz, C4" H), 7.99 (s, lH, C8" H), 7.02 (d, lH, J = 9.3 Hz, C3" H), 6.99 (d, lH, J = 2.0 Hz, ClO H), 6.87 (s, lH, C6" H), 6.15 (m, lH, Cl 1 H), 4.62 (m, 2H, C14 H), 4.37 (dd, lH, J = 7.8, 5.4 Hz, C13 H), 3.83 (s, 3H, CT' OCH 3), 3.68 (d, lH, J = 2.0 Hz, CS H), 3.33 (dd, lH, J = 14.1, 7.3 Hz, C12 ~H), 2.61 (s, 3H, CS" CH 3), 2.61 (d, lH, J = 2.0 Hz, C7 H), 2.51 (dd, lH, J = 14.1 , 4.9 Hz, C12 aH), 0.24 (s, 9H, OSi(CH 3) 3). 13 C NMR (100 MHz, CDCI 3), o: 187.4, 171.8, 165.2, 159.8, 153.8, 149.3, 142.5, 137 .3, 134.3, 133.3, 123.4, 116.8, 116.3, 104.3, 90.3, 77.1, 76.7, 76.3, 76.0, 75.8, 74.2, 66.9, 57.0, 55.2, 51.4, 51.1, 20.3, 1.9. FTIR (thin film), cm- 1: 3289 (m, OH), 2957 (m), 1822 (s, Carbonate C=O), 1644 (m, C=O), 1615 (s, C=O), 1413 (m), 1206 (s). HRMS (FAB): Calc'd for C31 H 30 0 10 Si [Mr: 590.1627 Found: 590.1608 97 1LC (50% EtOAc in Hexanes), Rf 50: 0.34 (UV, anisaldehyde) 51: 0.54 (UV, anisaldehyde) 98 o==<o O'' 11 TMSO,,. H CHO MEMCI, i-Pr2 NEt, CH 2Cl2 , O °C II i TMSO,,. 1 12 1 H CHO 94% Methoxyethoxymethyl ether 5 2 Methoxyethoxymethyl chloride (0.397 mL, 434 mg, 3.48 mmol, 15 equiv) was added to a solution of 1MS ether 51 (137 mg, 0.232 mmol, 1 equiv) and diisopropylethylamine (1.21 mL, 899 mg, 6.96 mmol, 30 equiv) in dichloromethane (30 mL) at 0 0 C. The reaction mixture was maintained at 0 °C for 1.5 h and partitioned between water (50 mL) and 1: 1 ethyl acetate in hexanes (50 mL). The aqueous layer was extracted with 1:1 ethyl acetate in hexanes (50 mL) and the combined organics were washed with saturated aqueous sodium chloride (25 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (50% ethyl acetate in hexanes) afforded the MEM ether 52 (145 mg, 94%) as a light orange oil. 99 9.48 (s, lH, C8 H), 7_67 (d, lH, J = 9.28 Hz, C4" H), 7.29 (d, lH, J = 9.28 Hz, C3" H), 7.28 (s, lH, C8" H), 7.02 (s, lH, C6" H), 6.64 (d, lH, J = 2.19 Hz, ClO H), 6.19 (m, lH, Cll H), 5.17 (s, 2H, ArOCH 2OCH2CH 2OCH 3), 3.97 (dd, lH, J = 9.03, 5.13 Hz, C13 H), 3.76 (m, 2H, ArOCH 2 OCH 2CH 2OCH 3), 3.65 (m, lH, C14 H), 3.55 (s, 3H, C7'' OCH 3), 3.42-3.31 (complex, 4H, ArOCH 2 OCH 2CH2 0CH 3, C14 H, C12 ~H), 3.15 (s, 3H, ArOCH 2OCH 2CH2OCH 3), 2.86 (d, lH, J = 1.47 Hz, C5 H), 2.58 (dd, lH, J = 13.67, 5.37 Hz, C12 aH), 2.28(s, 3H, C5" CH 3), 2.23 (d, lH, J = 1.50 Hz, C7 H), 0.32 (s, 9H, OSi(CH 3)). FTIR (thin film), cm- 1: 2953 (m), 2120 (w, C=C), 1821 (s, carbonate C=O), 1698 (s, C=O), 1254 (s), 1074 (s). HRMS (FAB): Calc'd for C35 H 38 NaO 12 Si [M+Na] +: 701.2030 Found: 701.2007 1LC (50% EtOAc in Hexanes), Rf. 51: 0.48 (UV, anisaldehyde) 52: 0.29 (UV, anisaldehyde) 100 0 o=< 0''' II i H CHO TMSO,,,. 0 .: 11 THF,-78 °C 11 ,~ 0 73% 0 H3C O ~ O M E M yU CH3 11 LiN(TMS)i, CeCl3, 0 H3COW(; "'.:::: OMEM ~ I ~ 4" 52 CH3 53 Cyclic alcohol s3 Lithium hexamethyldisilazide (0.262 mL of a 1.0 M solution in hexanes, 0.262 mmol, 1.02 equiv) was added over a two min period to a suspension of aldehyde 52 (175 mg, 0.258 mmol, 1 equiv) and anhydrous cerium(ill) chloride (194 mg, 0.787 mmol, 3 equiv) in THF (20 mL) at -78 °C. After maintaining the reaction mixture at -78 °C for 10 min, excess base was quenched by addition of saturated aqueous ammonium chloride (10 mL) and the reaction mixture was warmed to 23 °C. The reaction mixture was partitioned between 1: 1 ethyl acetate in hexanes (50 mL) and water (50 mL), and the layers were separated. The aqueous layer was further extracted with 1: 1 ethyl acetate in hexanes (2 50mL portions), and the combined organics were washed with saturated sodium chloride (25 mL), dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (50% ethyl acetate in hexanes) to provide the alcohol 53 (128 mg, 73%) as a light yellow oil. 101 7.66 (d, lH, J = 9.24 Hz, C4" H), 7.33 (d, lH, J = 2.30 Hz, C8" H), 7.20 (d, lH, J = 9.24 Hz, C3" H), 7.00 (d, lH, J = 2.25 Hz, C6" H), 6.42 (t, lH, J = 1.83 Hz, ClO H), 6.07 (m, lH, Cl 1 H), 5.32 (d, lH, J = 3.08 Hz, C8 H), 5.16 (abq, 2H, J = 6.82 Hz, ArOCH 2OCH 2CH2OCH 3), 3.75 (m, 2H, ArOCH2OCH 2CH2OCH 3), 3.63 (m, 4H, C13, C14, and C12 ~H), 3.57 (s, 2H, CT' OCH 3), 3.33 (m, 2H, ArOCH 2OCH2CH 2OCH 3), 3.07 (s, 3H, ArOCH 2OCH2CH 2 OCH 3), 2.93 (s, lH, C5 H), 2.41 (dd, lH, J = 14.14, 4.63 Hz, C12 aH), 2.29 (s, 3H, C5" CH 3), 0.22 (s, 9H, OSi(CH 3) 3). FI1R (thin film), cm- 1: 3474 (m, OH), 2924 (m), 1821 (s, carbonate C=O), 1722 (m, C=O), 1621 (m), 1254 (s), 1095 (s). HRMS (FAB): Calc'd for C35 H38 NaO 12 Si [M+Na] +: 701.2030 Found: 701.2011 1LC (75% EtOAc in Hexanes), Rf: 52: 0.58 (UV, anisaldehyde) 53: 0.73 (fluoresces under UV, anisaldehyde) 102 0 o=< 11 11 TBSOTf, 2,6-lutidine, 11 11 CH2 Cl 2 , -78 °C 93% Bis-silyl ether 6 0 2,6-Lutidine (0.487 mL, 402 mg, 3.75 mmol, 20 equiv) and tert-butyldimethylsilyl trifluoromethanesulfonate (0.431 mL, 496 mg, 1.87 mmol, 10 equiv) were added sequentially to a solution of alcohol 53 (125 mg, 0.187 mmol, 1 equiv) in dichloromethane (23 mL) at -78 °C. The reaction mixture was maintained at -78 °C for 30 min, and triethylamine (0.5 mL) and methanol (0.5 mL) were added and the reaction mixture was warmed to 23 °C. The reaction was partitioned between 1:1 ethyl acetate/hexanes (50 mL) and water (50 mL). The layers were separated, and the organic layer was washed with saturated aqueous sodium chloride (25 mL), dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (25% ethyl acetate in hexanes) to afford silyl ether 60 (138 mg, 93%) as a light yellow oil. 103 7.57 (d, lH, J = 9.29 Hz, C4" H), 7.24 (d, IH, J = 2.29 Hz, C8" H), 7.20 (d, lH, J = 9.29 Hz, C3" H), 6.90 (m, lH, C6" H), 6.42 (t, lH, J = 1.85 Hz, Cl0 H), 6.03 (m, lH, Cl 1 H), 5.52 (t, lH, J = 1.50 Hz, C8 H), 5.09 (s, 2H, ArOCH 2OCH 2CH2OCH3), 3.70 (m, 2H, ArOCH 2OCH2CH2 OCH3), 3.53 (dd, lH, J = 6.30, 3.96 Hz, C13 H), 3.48 (s, 3H, CT' OCH 3), 3.35-3.24 (complex, 4H, ArOCH 2OCH 2CH2OCH 3 , C14 H), 3.16 (dd, lH, J = 13.81, 7.29 Hz, C12 ~H), 3.04 (s, 3H, ArOCH 2OCH 2CH 2 OCH 3), 2.74 (d, lH, J = 1.76 Hz, C5 H), 2.40 (dd, lH, J = 13.86, 5.20 Hz, C12 aH), 2.20 (s, 3H, C5" CH 3), 0.90 (s, 9H, OSiC(CH 3)iCH 3) 2), 0.17 (s, 3H, OSiC(CH 3MCH 3) 2 ), OSi(CH 3) 3), 0.02 0.16 (s, (s, 9H, 3H, OSiC(CH 3)iCH 3) 2). FTIR (thin film), cm· 1: 2942 (m), 2931 (m), 2214 (w, C:a::C), 1823 (s, carbonate C=O), 1725 (m, C=O), 1622 (m), 1255 (s), 1096 (s). 1LC (50% EtOAc in Hexanes), Rf 53: 0.15 (fluoresces under UV, anisaldehyde) 60: 0.43 (fluoresces under UV, anisaldehyde) 104 0 o=<o•·· s 11 11 H ••,OTBS II Et3N•3HF, THF, 11 HO,,.. 0 °C H ··,oTBS /4 10 0 11 . 87'>/o 8 0.: H3COW8' "..::::: OMEM ::::,.., I ll 4' CH 3 61 Alcohol 61 Triethylamine trihydrofluoride (0.083 mL, 82.0 mg, 0.511 mmol, 3 equiv) was added via syringe to a solution of bis-silyl ether 60 (135 mg, 0.170 mmol, 1 equiv) in TIIF (25 mL) at 0 °C. The reaction was maintained at 0 °C for an additional 30 min, and saturated aqueous sodium bicarbonate (10 mL) was added. The reaction mixture was extracted with 1:1 ethyl acetate in hexanes (3 50-mL portions) and the combined extracts were washed with saturated aqueous sodium chloride, dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (50% ethyl acetate in hexanes) to provide the alcohol 61 (107 mg, 87%) as a light yellow oil. 105 7.64 (d, lH, J = 9.28 Hz, C4" H), 7.37 (br s, lH, C8" H), 7.16 (d, lH, J = 9.27 Hz, C3" H), 7.00 (br s, lH, C6" H), 6.44 (t, lH, J = 2.0 Hz, ClO H), 5.90 (m, lH, Cl 1 H), 5.54 (s, lH, C8 H), 5.11 (abq, 2H, J = 6.84 Hz, ArOCH 2OCH 2CH 2OCH 3), 3.72 (t, 2H, J = 4.88 Hz, ArOCH 2OCH 2CH 20CH 3), 3.67 (m, lH, C13 H), 3.52 (s, 3H, CT' OCH 3), 3.303.26 (complex, 4H, ArOCH 2OCH2CH2OCH 3 , C14 H), 3.07 (s, 3H, ArOCH 2OCH 2CH2OCH 3), 3.01 (dd, lH, J = 15.13, 7.08 Hz, C12 PH), 2.80 (s, lH, C5 H), 2.53 (dd, lH, J = 14.89, 2.44 Hz, C12 aH), 2.27 (s, 3H, C5" CH 3), 1.00 (s, 9H, OSiC(CH 3)iCH 3)J, 0.23 (s, 3H, OSiC(CH 3)iCH 3) 2), 0.06 (s, 3H, OSiC(CH 3)iCH 3) 2). FI1R (thin film), cm- 1: 3461 (m, OH), 2928 (m), 2202 (w, C=C), 1813 (s, carbonate C=O), 1725 (m, C=O), 1621 (m), 1257 (s), 1159 (s), 1096 (s). HRMS (FAB): Calc'd for C3gf44NaO12Si [M+Nat: 743.2500 Found: 743.2477 106 TLC (50% EtOAc in Hexanes), Rf: 60: 0.40 (fluoresces under UV, anisaldehyde) 61: 0.21 (fluoresces under UV, anisaldehyde) 107 II II 11 11 H CH 3S02CI, Et3N, CH 2Cl 2, O °C 10 ;~OS02CH3 0 ,.·· ~ H3C O w i r OMEM ~ I "° 4' CH3 62 Mesylate 62 Methanesulfonyl chloride (10.0 µL of a 0.323 M stock solution in dichloromethane, 3.23 x 10·3 mmol, 1.6 equiv) was added via syringe to a solution of alcohol 61 (2.00 mg, 2.77 x 10·3 mmol, 1 equiv) and triethylamine (10 µL, 7.00 mg, 0.0690 mmol, 25 equiv) in dichloromethane (0.5 mL) at 0 °C. The reaction mixture was held at 0 "C for an additional 10 min, and excess methanesulfonyl chloride was quenched by the addition of water (0.5 mL). The layers were separated, and the aqueous layer was further extracted with 1:1 ethyl acetate in hexanes (3 1-mL portions). The combined organic layers were dried over sodium sulfate and concentrated to a volume of ca. 0.1 mL. The concentrate was purified by flash column chromatography (dichloromethane grading to 10% ethyl acetate in dichloromethane). Fractions containing the mesylate were pooled and concentrated to a volume of ca. 0.1 mL. A 0.5 mL portion of deuteriated benzene (99.5 atom % D) was added and the resulting solution was concentrated to a volume of ca. 0.1 mL. This procedure was repeated 4 times. After the last iteration, the concentrated solution was taken up in approximately 0.4 mL deuteriated benzene (99.95 atom % D) for 108 1 H NMR analysis. Typically, the mesylate 62 was not subjected to column chromatography due to its instability, but was instead carried directly to the next reaction as the crude reaction mixture. 7.67 (d, lH, J = 9.28 Hz, C4" H), 7.38 (m, lH, C8" H), 7.30-7.00 (obscured, lH, C3" H), 6.97 (m, lH, C6" H), 6.12 (d, lH, J = 5.86 Hz, ClO H), 5.57 (app. q, lH, J = 5.86 Hz, C11 H), 5.35 (s, lH, C8 H), 5.13 (abq, 2H, J __ = 7.08 Hz, ArOCH 2 OCH 2 CH2 OCH3 ), 3.78-3.64 (complex, 3H, C13 and C14 H), 3.62 (s, 3H, CT' OCH 3 ), 3.32 (m, 4H, ArOCH 2 OCH2 CH 2 OCH 3 ), 3.11 (s, 3H, ArOCH 2 OCH 2 CH 2 OCH 3 ), 2.87 (s, lH, C5 H), 2.78 (dd, lH, J = 15.38, 1.50 Hz, C12 aH), 2.55 (dd, lH, J = 15.38, 6.35 Hz, C12 ~H), 2.31 (s, 3H, C5" CH 3), 2.26 (s, 3H, SO 2 CH 3 ), 1.15 (s, 9H, OSiC(CH 3 )iCH 3 ) 2 ), 0.47 (s, 3H, OSiC(CH 3 )iCH 3 ) 2 ), 0.43 (s, 3H, OSiC(CH 3 )iCH 3 ) 2 ). FTIR (thin film), cm- 1: 2923 (s), 1819 (m, carbonate C=O), 1731 (m, C=O), 1460 (m), 1255 (m). 61: 0.13 (fluoresces under UV, anisaldehyde) 62: 0.39 (fluoresces under UV, anisaldehyde) 109 0 o=( o•·· 11 II 11 11 89% Diol 63 Triethylamine trihydrofluoride (34.0 µL, 34.0 mg, 0.211 mmol, 3 equiv) was added to a solution of alcohol 53 (47.0 mg, 0.0700 mmol, 1 equiv) in THF (0.2 mL) at 0 0 C. The solution was kept at this temperature for 2 h, and saturated sodium bicarbonate (0.5 mL) was added. The reaction mixture was diluted with 1: 1 ethyl acetate in hexanes (25 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (75% ethyl acetate in hexanes) afforded the diol 63 (38.0 mg, 89%) as a pale yellow powder. 110 7.82 (d, lH, J = 9.22 Hz, C8" H), 7.09 (d, lH, J = 9.28 Hz, C6" H), 6.85 (d, lH, J = 2.15 Hz, C3" H), 6.81 (d, lH, J = 1.26 Hz, C4" H), 6.26 (t, lH, J = 1.95 Hz, ClO H), 5.86 (m, lH, Cl 1 H), 5.34 (br s, lH, C8 H), 5.25 (abq, 2H, J = 6.69 Hz, ArOCH 2OCH 2CH20CH 3), 4.51 (t, lH, J = 8.85 Hz, C13 H), 4.42 (dd, lH, J = 8.95, 5.58 Hz, C14 H), 3.77 (s, 3H, CT' OCH 3), 3.71 (m, lH, ArOCH 2OCH2CH2OCH 3), 3.66 (m, lH, ArOCH 2OCH 2CH 20CH 3), 3.53 (s, lH, C5 H), 3.43 (t, 2H, J = 5.09 Hz, ArOCH 2OCH 2CH 2OCH 3),3.35 (dd, lH, J = 8.21, 5.58 Hz, C14 H), 3.25 (s, 3H, ArOCH2OCH2CH2OCH3), 3.00 (dd, lH, J = 15.09, 7.07 Hz, C12 ~H), 2.50 (s, 3H, C5" CH 3), 2.16 (dd, lH, J = 15.00, 2.34 Hz, C12 aH). FI1R (thin film), cm· 1: 3444 (s, OH), 2924 (s), 2214 (w, C=C), 1816 (s, carbonate C=O), 1714 (s, C=O), 1621 (s), 1469 (m), 1257 (s), 1160 (s), 1035 (s) cm· 1 HRMS (FAB): Calc'd for C32H30NaO 12 [M+Nar: 629.1635 Found: 629.1624 111 1LC (10% EtOAc in Hexanes), Rf. 53: 0.58 (fluoresces under UV, anisaldehyde) 63: 0.35 (fluoresces under UV, anisaldehyde) 112 0 o=< 11 11 Tip, pyridine, CH 2ct 2, -78 ~ 0 °C 11 11 TMSO,,.. 12 Alcohol 64 Trifluoromethanesulfonic anhydride (7.60 µL, 12.7 mg, 4.50 x 10·3 mmol, 15 equiv) was added via syringe to a solution of alcohol 53 (2.00 mg, 3.00 x 10·2 mmol, 1 equiv) and pyridine (7.30 µL, 7.00 mg, 9.00 x 10·2 mmol, 30 equiv) in dichloromethane (0.3 mL) at-78 °C. After 30 min at -78 °C, the reaction mixture was wanned to 0 °C for 10 min. Water (0.3 mL) was added, and the reaction mixture was extracted with 1:1 ethyl acetate in hexanes (2 1-mL portions). The combined organics were washed with 10% aqueous hydrochloric acid (1 mL) and saturated aqueous sodium chloride (1 mL), dried over sodium sulfate and concentrated to ca. 0.1 mL. The concentrate was purified by flash column chromatography (25% ethyl acetate in hexanes), and fractions containing the product were pooled and concentrated to a volume of ca. 0.1 mL. A 0.5 mL portion of deuteriated benzene (99.5 atom % D) was added and the resulting solution was concentrated to a volume of ca. 0.1 mL. This procedure was repeated 4 times. After the last iteration, the concentrated solution was taken up in approximately 0.4 mL deuteriated benzene (99.95 atom % D) for 1H NMR analysis. Typically, the alcohol 6 4 was not 113 subjected to column chromatography due to its instability, but was instead carried directly to the next reaction as the crude reaction mixture. 7.77 (s, lH, C8" H), 7.64 (d, lH, J = 9.23 Hz, C4" H), 7.50-6.90 (obscured by solvent, 2H, C6", C3" H), 5.46 (m, lH, Cll H), 5.19 (abq, 2H, J = 6.83 Hz, ArOCH 2OCH 2CH 2OCH 3), 5.17 (d, lH, J = 1.47 Hz, C8 H), 4.66 (dd, IH, J = 10.50, 6.10 Hz, CIO H), 3.86-3.67 (complex, 4H, ArOCH 2 OCH 2CH 2OCH 3 ,Cl3, C14 H), 3.73 (s, 3H, CT' OCH 3), 3.32 (t, 2H, J = 4.89 Hz, ArOCH 2OCH2CH2 OCH 3), 3.25 (t, lH, J = 8.3 Hz, C14 H), 3.18-3.04 (obscured, lH, Cl2 ~H), 3.10 (s, 3H, ArOCH 2OCH 2CH 2OCH 3), 2.76 (d, lH, J = 1.47 Hz, C5 H), 2.36 (dd, lH, J = 13.18, 2.64 Hz, C12 aH), 2.27 (s, 3H, C5" CH 3), 0.14 (s, 9H, OSi(CH 3) 3). 1LC (25% EtOAc in Hexanes), Rf: 53: 0.41 (fluoresces under UV, anisaldehyde) 64: 0.57 (fluoresces under UV, anisaldehyde) 114 TBSCI, DMAP, El3N, CH2Cl 2, 0 °C 11 II HO,,,. HO,,,. 92% i 7 12 HO.:-' 47 65 TBS Ether 65 4-Dimethylaminopyridine (137 mg, 1.08 mmol, 0.5 equiv) was added in one portion to a solution of diol 47 (784 mg, 2.15 mmol, 1 equiv), triethylamine (1.50 mL, 1.09 g, 10.8 mmol, 5 equiv) and tert-butyldimethylsilyl chloride (486 mg, 3.23 mmol, 1.5 equiv) in dichloromethane (30 mL) at 0 0 C. The reaction mixture was maintained at 0 CC for an additional 20 min, then warmed to 23 °C for 20 h. The reaction mixture was then partitioned between ethyl acetate (50 mL) and water (30 mL). The aqueous layer was extracted with ethyl acetate (2 20-mL portions), and the combined organics were washed with saturated aqueous sodium chloride (30 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (30% ethyl acetate in hexanes) afforded TBS ether 65 (953 mg, 92%) as a colorless oil. 115 6.16 (s, lH, ClO H), 5.42 (s, lH, C8 H), 4.83 (m, lH, Cl 1 H), 4.09 (dd, lH, J = 8.80, 5.84 Hz, C13 H), 3.95 (s, lH, OH), 3.83 (dd, lH, J = 8.80, 6.96 Hz, C14 H), 3.60 (t, lH, J = 6.24 Hz, C14 H), 3.37 (d, lH, J = 2.72 Hz, C5 H), 3.17 (s, 3H, CH(OCH 3) 2 ), 3.15 (s, 3H, CH(OCH 3\ ) , 3.14 (dd, lH, J = 13.56, 6.92 Hz, C12 H), 2.52 (dd, lH, J = 13.16, 5.48 Hz, C12 H), 1.99 (d, lH, J = 0.84 Hz, C7 H), 1.45 (s, 3H, C(CH 3)2), 1.20 (s, 3H, C(CH 3) 2 ), 0.95 (s, 9H, OSiC(CH 3)iCH 3) 2)), 0.046 (s, 3H, OSiC(CH 3)iCH 3) 2) ), 0.029 (s, 3H, OSiC(CH 3)iCH 3) 2) ) . 142.8, 136.1, 110.7, 99.8, 90.0, 78.5, 77.3, 77.2, 75.2, 74.9, 73.3, 66.8, 58.0, 52.8, 52.3, 50.0, 49.9, 26.4, 26.0, 25.3, 18.2, -4.6. FTIR (thin film), cm· 1: 3496 (m, OH), 3279 (m, C=C-H), 2933 (s), 2857 (s), 2127 (w, C=C), 1469 (m), 1372 (s), 1256 (s), 1214 (s), 1154 (m), 1108 (s), 1074 (s), 838 (s). HRMS (FAB): Calc'd for C25H37 0 7 Si [M-Ht: 477.2309 Found: 477.2304 116 1LC (70% EtOAc in Hexanes), Rf 47: 0.20 (anisaldehyde) 65: 0.95 (anisaldehyde) 117 p-TsOH, acetone, II ~ 23°c II ~ 7 H H 90% CHO TBSO.: 65 66 Aldehyde 66 p-Toluenesulfonic acid (21 mg) was added in one portion to a solution of the dimethyl acetal 65 (248 mg, 0.518 mmol, 1 equiv) in acetone (7 mL). The resultant yellow solution was stirred at 23 °C for 15 min and then neutralized with saturated aqueous sodium bicarbonate (10 mL). The reaction mixture was extracted with 1:1 ethyl acetate/hexanes (3 10-mL portions), and the combined organics were washed with saturated sodium chloride (15 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (5% ethyl acetate in dichloromethane) provided the aldehyde 66 (202 mg, 90%) as a colorless solid, mp 90-92 oc. 118 9.28 (s, lH, C8 H), 6.03 (d, lH, J = 1.84 Hz, ClO H), 4.76 (td, lH, J = 6.96, 1.84 Hz, Cll H), 4.08 (dd, lH, J = 8.80, 5.88 Hz, C13 H), 3.85 (s, IH, OH), 3.84 (dd, lH, J = 8.76, 6.60 Hz, C14 H), 3.57 (t, lH, J = 6.56 Hz, C14 H), 3.36 (d, lH, J = 1.48 Hz, C5 H), 3.02 (dd, lH, J = 12.80, 6.92 Hz, C12 H), 2.34 (dd, lH, J = 12.44, 6.96 Hz, Cl2 H), 2.07 (d, lH, J = 1.84 Hz, C7 H), 1.44 (s, 3H, C(CH 3) 2) , 1.19 (s, 3H, C(CH 3) 2 ), 0.92 (s, 9H, OSiC(CH 3)iCH 3) 2)), -0.0035 (s, 3H, OS~C(CH 3)iCH 3) 2)), -0.0365 (s, 3H, OSiC(CH 3)/CH 3) 2 )). 189.2, 151.8, 145.6, 110.8, 88.5, 78.3, 77.0, 75.0, 73.5, 73.3, 66.9, 57.9, 52.1, 50.1, 50.0, 26.4, 25.9, 25.4, 18.1 , -4. 7, -4.8. FTIR (thin film), cm- 1: 3431 (m, OH), 3279 (m, C=C-H), 2932 (s), 2857 (s), 2128 (w, C=C), 1686 (s, C=O), 1471 (m), 1357 (m), 1258 (s), 1216 (m), 1119 (m), 1076 (s), 838 (s). HRMS (FAB): Calc'd for C23 H31 0 6 Si (M-Ht: 431.1890 Found: 431.1888 119 TLC (30% EtOAc in Hexanes), Rf. 65: 0.28 (anisaldehyde) 66: 0.31 (UV, anisaldehyde) 120 TMSOTf, 2,6-lutidine, II HO,,,. i CH 2Cl 2, -78 °C H CHO 88% 11 ~ 1 H TMSO,,.. CHO 12 TBSO.: 66 67 TMS Ether67 2,6-Lutidine (4.71 mL, 4.34 g, 40.5 mmol, 10 equiv) and trimethylsilyl trifluoromethanesulfonate (3.91 mL, 4.50 g, 20.2 mmol, 5 equiv) were added sequentially via syringe to a solution of aldehyde 66 (1.75 g, 4.05 mmol, 1 equiv) in dichloromethane (100 mL) at -78 °C. The resultant solution was maintained at -78 °C for an additional 20 min, and excess trimethylsilyl trifluoromethanesulfonate was quenched by the addition of triethylamine (5 mL) and methanol (5 mL). The reaction mixture was warmed to 23 °C and diluted with 1:1 ethyl acetate/hexanes (100 mL). The mixture was washed with water (2 50-mL portions) and saturated aqueous sodium chloride (50 mL). The organics were then dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (20% ethyl acetate in hexanes) afforded the TMS ether 67 (1.79 g, 88%) as a pale yellow oil. 121 9.78 (s, lH, C8 H), 6.37 (d, lH, J = 1.44 Hz, CIO H), 4.74 (td, lH, J =6.96, 1.84 Hz, Cll H), 4.10 (dd, lH, J = 8.76, 5.84 Hz, C13 H), 3.91 (dd, lH, J = 8.76, 6.60 Hz, C14 H), 3.60 (t, lH, J = 6.60 Hz, C14 H), 3.33 (d, lH, J = 1.44 Hz, C5 H), 3.16 (dd, lH, J = 12.84, 7.32 Hz C12 H), 2.40 (dd, lH, J = 12.84, 6.60 Hz, C12 H), 2.07 (d, lH, J = 1.44 Hz, C7 H), 1.43 (s, 3H, C(CH 3) 2), 1.18 (s, 3H, C(CH 3)2), 0.94 (s, 9H, OSiC(CH 3)iCH 3) 2), 0.40 (s, 9H, OSi(CH 3)3), 0.01 (s, 6H, OSiC(CH 3)iCH 3) 2). 187.5, 147.1, 146.6, 110.7, 88.5, 79.8, 78.2, 76.9, 75.3, 74.2, 73.3, 66.9, 57.8, 55.2, 50.0, 26.4, 25.8, 25.2, 18.1, 2.0, -4.8. +91.02 ° (c 2.65, C6HJ FITR (thin film), cm· 1: 3281 (m, C=C-H), 2954 (s), 2889 (s), 2857 (m), 2131 (w, C=C), 1697 (s, C=O), 1470 (m), 1373 (s), 1256 (m), 1077 (s), 884 (m), 839 (s). lLC (30% EtOAc in Hexanes), Rf 66: 0.37 (UV, anisaldehyde) 67: 0.61 (UV, anisaldehyde) 122 11 11 11 11 75% 12 TBSO.:· TBSO.: 68 69 Cyclic alcohol 6 8 Lithium hexamethyldisilazide (0.560 mL of a 1.0 M solution in hexanes, 0.560 mmol, 1.2 equiv) was added over a 2 min period to a suspension of aldehyde 67 (223 mg, 0.467 mmol, 1 equiv) and anhydrous cerium(III) chloride (340 mg, 1.40 mmol, 3 equiv) in THF (25 mL) at -78 °C. After maintaining the reaction mixture at -78 °C for an additional IO min, excess base was quenched by addition of saturated aqueous ammonium chloride (5 mL) and the reaction mixture was warmed to 23 °C. The reaction mixture was partitioned between 1:1 ethyl acetate/hexanes (25 mL) and water (25 mL), and the layers were separated. The aqueous layer was further extracted with 1: 1 ethyl acetate/hexanes (2 25-mL portions), and the combined organics were washed with saturated sodium chloride (25 mL), dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (10% ethyl acetate in hexanes grading to 20% ethyl acetate in hexanes) to provide the alcohol 68 ( 183 mg, 82%) as a pale orange oil. 123 5.87 (t, lH, J = 1.74 Hz, ClO H), 5.16 (m, lH, C8 H), 4.67 (m, lH, Cl 1 H), 3.82 (dd, lH, J = 8.56, 5.85 Hz, C13 H), 3.66 (dd, lH, J = 8.54, 6.54 Hz, C14 H), 3.50 (t, lH, J = 6.01 Hz, C14 H), 3.04 (s, lH, C5 H), 2.95 (dd, lH, J = 12.89, 6.97 Hz, C12 ~H), 2.19 (dd, lH, J = 12.87, 5.87 Hz, C12 aH), 1.40 (s, 3H, C(CH 3) 2), 1.13 (s, 3H, C(CH 3)i), 0.86 (s, 9H, OSiC(CH 3)/CH 3) 2 ), 0.27 (s, 9H, OSi(CH 3) 3), --0.06 (s, 3H, OSiC(CH 3)lCH 3)i), -0_07 (s, 3H, OSiC(Cl:I 3)/CH 3\ ) . FI1R (thin film), cm- 1: 3428 (m, OH), 2953 (s), 2857 (m), 1467 (m), 1372 (m), 1254 (s), 1074 (s). TLC (30% EtOAc in Hexanes), Rf: 67: 0.46 (anisaldehyde) 68: 0.38 (anisaldehyde) 124 11 11 11 11 75% rsso'" TBSO.: 68 69 Diol 69 Potassium fluoride (98.0 mg, 1.67 mmol, 10 equiv) was added in one portion to a solution of alcohol 68 (80.0 mg, 0.167 mmol, 1 equiv) in methanol (8 mL) at 23 °C. The solution was maintained at 23 °C for 2 h, then diluted with water (20 mL). The reaction mixture was extracted with ethyl acetate (3 25-mL portions), and the combined extracts were washed with saturated aqueous sodium chloride (25 mL), dried over sodium sulfate, and concentrated. The residue was purified by flash column chromatography (40% ethyl acetate in hexanes) to afford diol 69 (54 mg, 75%) as a pale orange oil. 125 6.01 (t, lH, J = 1.81 Hz, ClO H), 5.28 (br s, lH, C8 H), 4.61 (m, lH, C11 H), 3.96 (dd, lH, J = 8.74, 5.79 Hz, C13 H), 3.79 (dd, lH , J = 8.70, 6.62 Hz, C14 H), 3.62 (t, lH, J = 6.41 Hz, C14 H), 3.18 (s, lH, C5 H), 2.87 (dd, lH, J = 13.52, 6.96 Hz, C12 (3H), 2.79 (br s, lH, OH), 2.13 (dd, lH, J = 13.56, 4.91 Hz, C12 aH), 2.03 (br s, lH, OH), 1.51 (s, 3H, C(CH 3) 2), 1.24 (s, 3H, C(CH 3) 2 ), 0.93 (s, 9H, OSiC(CH 3MCH 3) 2), 0.01 (s, 3H, OSiC(CH 3MCH 3) 2), 0.00 (s, 3H, OSiC(CH 3)iCH 3) 2). FTIR (thin film), cm- 1: 3422 (m, OH), 2929 (s), 2856 (m), 1458 (m), 1373 (s) 1256 (s), 1216 (m), 1074 (s). 1LC (40% EtOAc in Hexanes), Rf: 68: 0.53 (anisaldehyde) 69: 0.26 (anisaldehyde) 126 H3CXO H3C H3CXO O''' Pf1:iSiCI, Et3N, 11 II H3C 0'' DMAP, CH 2 Cl 2 14 .A H 5 II II H 66% 12 ..:· ..: TBSO TBSO 69 70 Tertiaiy alcohol 7 o Triphenylsilyl chloride (27.0 mg, 0.0902 mmol, 1.5 equiv) was added to a solution of diol 69 (26. mg, 6.0 x 10·2 mmol, 1 equiv), triethylamine (42 µL, 30 mg, 0.30 mmol, 5 equiv), and DMAP (4 mg, 3 x 10·2 mmol, 0.5 equiv) in dichloromethane (1.5 mL) at 23 °C. The reaction mixture was maintained at 23 °C for 2.5 h, and partitioned between water (5 mL) and 1:1 ethyl acetate in hexanes (5 mL). The aqueous layer was further extracted with 1:1 ethyl acetate/hexanes (2 5-mL portions) and the combined organics were washed with saturated aqueous sodium chloride (15 mL), dried over sodium sulfate, and concentrated. Purification of the residue by flash column chromatography (20% ethyl acetate in hexanes) afforded the alcohol 70 (28 mg, 66%) as a pale yellow powder. 127 7.87 (m, 6H, OSi(C 6 H 5 ) 3 ), 7.70 (m, 3H, OSi(C 6 H 5 ) 3 ), 7.25 (m, 6H, OSi(C6 H 5 ) 3 ), 6.33 (t, lH, J = 1.79 Hz, Cl0 H), 5.76 (t, lH, J = 1.41 Hz, C8 H), 4.64 (m, lH, C11 H), 3.92 (dd, lH, J = 8.64, 5.69 Hz, C13 H), 3.74 (dd, lH, J = 8.67, 6.60 Hz, C14 H), 3.54 (t, lH, J = 6.30 Hz, C14 H), 3.05 (s, lH, C5 H), 2.84 (dd, lH, J = 13.45, 6.96 Hz, C12 ~H), 2.08 (dd, lH, J = 13.51, 5.00 Hz, C12 aH), 1.49 (s, 3H, C(CH 3) 2), 1.22 (s, 3H, C(CH 3) 2 ), 0.91 (s, 9H, OSiC(CH 3)iCH 3) 2), 0.27 (s, 9H, OSi(CH 3 ) 3 ), -0.04 (s, 6H, OSiC(CH 3MCH 3) 2). FTIR (thin film), cm· 1: 3437 (m, OH), 2929 (m), 2856 (m), 1589 (m), 1428 (m), 1358 (m), 1255 (m), 1117(s), 1072 (s). TLC (40% EtOAc in Hexanes), Rf: 69: 0.21 (anisaldehyde) 70: 0.55 (UV, anisaldehyde) 128 11 II H CH3SO2CI, EtaN, CH2Cl2, 0 °C II II TBSO.: 70 Mesylate 71 Methanesulfonyl chloride (50 µL of a 1.3 mM stock solution in dichloromethane, 6.5 x 10·2 mmol, 22 equiv) was added via syringe to a solution of alcohol 70 (2.0 mg, 2.9 x 10·3 mmol, 1 equiv) and triethylamine (10 µL, 7.0 mg, 0.073 mmol, 25 equiv) in dichloromethane (0.2 mL) at 0 °C. The reaction mixture was held at 0 °C for an additional 10 min, and excess methanesulfonyl chloride was quenched by the addition of water (0.5 mL). The layers were separated, and the aqueous layer was further extracted with 1:1 ethyl/acetate in hexanes (3 1-mL portions). The combined organic layers were dried over sodium sulfate and concentrated to a volume of ca. 0.1 mL. The concentrate was purified by flash column chromatography (dichloromethane grading to 10% ethyl acetate in dichloromethane). Fractions containing mesylate 71 were pooled and concentrated to a volume of ca. 0.1 mL. A 0.5 mL portion of deuteriated benzene (99.5 atom % D) was added and the resulting solution was concentrated to a volume of ca. 0.1 mL. This procedure was repeated 4 times. After the last iteration, the concentrated solution was taken up in approximately 0.4 mL deuteriated benzene (99.95 atom % D) for 1H NMR analysis. Typically, the mesylate 71 was not subjected to column chromatography due to 129 its instability, but was instead carried directly to the next reaction as the crude reaction mixture. 7.96 (d, 3H, J = 6.59 Hz, OSi(C 6 H 5 ) 3), 7.72 (dd, 2H, J = 7.08, 1.71 Hz, OSi(C 6 H 5 ) 3 ), 7.30-7.22 (complex, lOH, OSi(C 6 H 5 ) 3), 5.81 (d, lH, J =7.08 Hz, ClO H), 5.48 (d, lH, J = 2.69 Hz, C8 H), 3.97 (dd, lH, J = 8.79, 5.86 Hz, C13 H), 3.91 (d, lH, J = 6.84 Hz, C11 H), 3.79 (dd, lH, J = 8.79, 6.59 Hz, C14 H), 3.57 (t, lH, J = 6.10 Hz, C14 H), 3.06 (s, lH, C5 H), 2.51 (ddd, lH, J = 12.94, 7.08, 2.69 Hz, C12 ~H), 2.24 (dd, lH, J = 15.86, 6.83 Hz, C12 aH), 2.20 (s, 3H, OSO2CH 3), 1.54 (s, 3H, C(CH 3 ) 2 ), 1.24 (s, 3H, C(CH 3 \ ) , 0.95 (s, 9H, OSiC(CH 3)(CH3 ) 2 ), 0.14 (s, 3H, OSiC(CH 3 )/CH 3 ) 2), 0.03 (s, 3H, OSiC(CH 3)iCH 3) 2). 70: 0.85 (UV, anisaldehyde) 71: 0.74 (UV, anisaldehyde) 130 Chapter 3 Intermediate Synthetic Strategies 131 An Allylic Mitsunobu Inversion Approach Drawing upon the observations made about the rearrangement behavior of the substrates discussed in Chapter 2, it was envisioned that the stereoselectivity necessary for a successful allylic transposition reaction might be achieved under Mitsunobu conditions.62 Although little precedent exists for the application of the Mitsunobu esterification to either the inversion of tertiary alcohols or allylic transposition reactions, it was anticipated that the desired transformation would be favorable using a substrate having the general structure A. Activation of the tertiary alcohol would be assisted by its being both allylic and propargylic; however, the steric demands of the C-1 oxyphosphonium intermediate should disfavor direct inversion and instead favor attack of the nucleophile at the C-10 position to afford a product having the general structure B. The stereoselectivity of the reaction would also be expected to proceed in the requisite sense, with the naphthoate ester effectively blocking attack from the bottom face of A (as drawn). Finally, it was predicted that the mechanism of the Mitsunobu inversion, known to disfavor the formation of carbocationic intermediates, would preclude the formation of the dioxolenium intermediates that were observed previously (cf. Ch. 2, Scheme IX). 0 o=< O''' 11 11 11 R'CO 2H, PPh 3 , 11 H DEAD, solvent.., ____________ 11. 0 0 H3C O ~ O R y) CH 3 A cf O O2CR' H3C O ~ O R y) CH3 8 Preliminary studies of this reaction sequence were carried out with the tertiary alcohol 70. Reaction of this intermediate with chloroacetic acid (25 equiv), 132 triphenylphosphine (25 equiv), and diethyl azodicarboxylate (DEAD, 25 equiv) in benzene at 23 °C63 afforded a product that was initially assigned as the desired rearranged ester 7 3 (in 16-18% yield as determined by 'H NMR integration against trans-1,2-dichloroethylene added as an internal standard). This structural assignment was based on several considerations, including the observation that the components of both substrate 70 and chloroacetic acid were visible in a 1: 1 ratio in the 1H NMR spectrum of the product. Furthermore, comparison of the changes in the proton chemical shifts and the coupling constants of the alcohol 70 and the product were consistent with the formation of ester 73. 56 Comparison of the 1H NMR spectrum of the reaction product with the spectra of other well-characterized intermediates, both rearranged and non-rearranged, also supported the assignment of the product as ester 73. For further assistance in the determination of the regiochemistry of the product, the C-H coupling constant at C-10 was determined. The magnitude of this coupling constant, generally indicative of the hybridization of the carbon center,68 was found to be borderline between the values expected for sp 2 and sp 3 centers and consequently of little aid in the assignment of the structure. Believing that the desired transformation had taken place, studies to optimize both the degree of functionalization of the reaction substrate and the yield of the product were initiated. 11 11 11 11 H ,..: 10 TBSO 70 TBSO..: O2CCH2CI 73 With the intention of carrying out this reaction on a system bearing more of the functionalization present within the aglycone 6, an ethylene carbonate-containing intermediate was prepared (Scheme XII). In anticipation of the selective removal of the 133 C-13 - C-14 diol protecting groups in the presence of the C-10 TBS ether, the diol 32 was treated with TMSOTf (12 equiv) and 2,6-lutidine (20 equiv) in dichloromethane at -78 CC: to afford the epoxydiyne intermediate 74 in quantitative yield. 54 Deprotonation of 74 (1.02 equiv) with LiN(TMS) 2 (1.05 equiv) in toluene at -78 °C was followed by addition of the enone dimethyl acetal (+)-21 (1.0 equiv) to provide the coupled tertiary alcohol 75 in 60% yield after flash column chromatography. The trimethylsilyl groups were selectively cleaved by treatment of intermediate 7 5 with triethylamine trihydrofluoride (3 equiv) in THF at O 0 C. 32 The carbonate group was then introduced by treatment with carbonyldiimidazole (1.2 equiv) in THF, affording carbonate 77 in 65% overall yield from 75. 53 Selective removal of the acetylenic TBS proved to be nontrivial, as both the C-10 TBS ether and the ethylene carbonate were found to be labile under many of the deprotection conditions examined. After extensive investigation, it was determined that treatment of 77 with TBAF (2 equiv) in THF at -63 °C selectively cleaved the acetylenic TBS group to provide the free acetylene (78) in 90% yield. Subsequent hydrolysis of the dimethyl acetal with p-toluenesulfonic acid in acetone at 23 °C afforded the a.,~-unsaturated aldehyde 79 in 74% yield. 65 The tertiary alcohol of 79 was silylated in 99% yield with TMSOTf (5 equiv) and 2,6-lutidine (10 equiv) in dichloromethane at -78 °C. 54 Closure of the nine-membered ring was effected with LiN(TMS) 2 (1 equiv) and cerium(III) chloride (3 equiv) in THF at -78 °C, producing secondary alcohol 81 in 55% yield. 13•19 Removal of the TMS group with triethylamine trihydrofluoride (3 equiv) in THF at O°C 32 was followed by selective silylation of the secondary alcohol (82) with TPSCl (1.3 equiv), triethylamine (5 equiv), and DMAP (0.5 equiv) in dichloromethane at O °C66 to provide the carbonatecontaining intermediate 83 in 25% overall (unoptimized) yield from 81. Surprisingly, the tertiary alcohol 83 was inert to the Mitsunobu conditions utilized for the transformation of 70, indicating that the ethylene carbonate was deactivating the tertiary alcohol, likely through an inductive effect. 134 Scheme XII HO ~~" TMSO TMSOTf, 2,6-lutidine, TMOO~H CH2Cl 2, -78 °C ii. (+)-21 q.iantitative H i. LiN(TMS)2, PhCH3, -78'C TBS H 32 TBS 74 TMSO 60% 0 o=( O''' 1. El3N•3HF, THF, 0 °C, 82% 11 II 2. CDI, THF, o ➔ 23 °C, 79% HO,,,. HO,,,. ~- ~TBSO TBSO 77 75 0 o=< 0'' 1. Bu4 NF, THF, ~°C,90% II ~ HO,,.. 2. p-TsOH, acetone, H CHO 1. TMSOTf, 2,6-lutidine, CH2C'2, -78 °C, 99% 2. LiN(TMS) 2, CeCl3, THF, -78 °C, 55% 23°c, 74% 79 0 0 o=< O'' II II 1. Et3N•3HF, THF, 0 °C, 57% 2. TPSCI, Et3N, DMAP, CH2C1 2, O ➔ 23 °C, 43% o=( o•·· II II 135 Concurrent with these efforts, additional studies canied out by Dr. Y. Wu in this research group indicated that methyl diphenylphosphine was superior to triphenylphosphine in effecting the esterification of structurally similar substrates. When the reaction was carried out with the alcohol 84 and 4-azidobutyric acid (10 equiv), methyl diphenylphosphine (10 equiv), and DEAD (10 equiv) in benzene at 5 °C, the coupled product was obtained in 67% yield as determined by 1H NMR integration against an internal standard.69 Subsequently, the incrementally more functionalized intermediates 85, having the naphthoate ester in place, and 89, having both the ethylene carbonate and the naphthoate ester present, were found to undergo the esterification reaction with the 2nitrobenzyl protected hydroxy acid 91 under the new conditions. 70 TBSO.: 84 0 o=<o•·· 11 11 O 0.: II HO~ 0 H3C O ~ O T B S Yv CH 3 89 91 O:O ~N O ~ I 136 Scheme XIII 0 o=<-0''" 11 11 11 11 91, CH 3PPh 2, DEAD, C6H6, 5 °C 27'% (±)-CSA, 2:1 CH 3CN/H 20, 23 °C 57% H3CO~O d OTBS H3 C 93a The product derived from the coupling of 89 and 91, assigned as structure 92a (Scheme XIII), was quantitated (27% yield from 89) and purified by reverse-phase HPLC. 72 The diester (92a) was next subjected to deprotection-elimination studies. Treatment of the esterification product 92a with (±)-camphorsulfonic acid (5 equiv) in a 2:1 mixture of acetonitrile and water at 23 °C provided the corresponding alcohol in 57% yield, assigned as structure 93a. A number of elimination conditions were examined for the conversion of 93a to the epoxydienediyne (C, Scheme XIV), most notably triflic anhydride and pyridine in dichloromethane at -78 °C. Under these conditions, conversion 137 Scheme XIV 0 0 o=< o=< o··· o•·· 11 11 (CF3S02)20, base, CH 2a 2, (CF3SO2hO, pyridine-<i 5 CD2Cl 2, -78 °C ➔ --30°C OR 11 II 138 to a new product could be observed by thin-layer chromatography, but could not be isolated after aqueous work-up of the reaction mixture. The lack of success in isolating the supposed dienediyne C prompted a low-temperature study of the elimination reaction. Accordingly, the alcohol assigned as 93a was taken up in deuteriated dichloromethane and placed in an NMR tube, where it was cooled to -78 °C. Deuteriated pyridine (20 equiv) and triflic anhydride (10 equiv) were added to the cold reaction mixture, and the NMR tube was quickly inserted into an NMR spectrometer whose probe had been cooled to -70 °C. Unreacted starting material was observed by 1H NMR at this temperature, so the reaction was gradually warmed in the probe of the instrument and the progress of the reaction was monitored by 1H NMR spectroscopy. When the temperature of the probe reached -30 °C, clean conversion to a new product was observed. The signals for this product did not correspond to the expected dienediyne C, but instead were consistent with either triflate 9 4 or dioxolenium ion 95, neither of which could have been derived from the alcohol 93a . The origin of the product (94 or 95) could best be explained by the triflic anhydrideinduced rearrangement of a substrate having the structure 93b , which would result from the direct inversion of the tertiary alcohol of Mitsunobu substrate 89. It appeared as though the same structural and electronic features that were expected to favor the allylic transposition during the Mitsunobu reaction of this substrate, namely the coupling of the allylic and propargylic natures of the C-1 alcohol, served to activate the alcohol for direct displacement. Once the regiochemistry of the esterification reaction was unequivocally assigned, this strategy was discontinued. 139 Revisitation of an Alternate Ring Closure Strategy Within this research group, early studies directed toward the preparation of the epoxydienediyne core of neocarzinostatin chromophore had shown that the a,~unsaturated aldehyde 96 (Figure 1) failed to cyclize to the desired nine-membered ring alcohol upon treatment with LiN(TMS)i in THF at -78 °C. 67 The a,~-unsaturated aldehyde 13, however, proved to be an excellent substrate for the ring-closure reaction, and eventually served as an intermediate in the synthetic sequence providing the functionalized core structure 5 (cf. Ch. 1, Scheme II). 13•19 A rationale for the differential behavior under the ring-closure was developed upon inspection of molecular models of 9 6 and 13. The C-7 carbon of 96 is thought to be nearly coplanar with the C-8 carbonyl group, rendering the trajectory necessary for nucleophilic addition of the acetylide into the aldehyde carbonyl inaccessible without significant distortion of the molecule. On the other hand, the C-7 carbon of enal 13 can be positioned within a more favorable trajectory for nucleophilic addition into the C-8 carbonyl. The enal 96 bore no substitution at the C-10 and C-11 positions, and the possibility of using substituents at these positions to bend the C-8 carbonyl out of plane to favor the proper trajectory for acetylide addition was considered. Accordingly, a direct synthesis of the a,~-unsaturated aldehyde 103, having bulky triisopropylsilyl and tert- butyldimethylsilyl ethers at C-10 and C-11, respectively, was developed. Reaction of the tertiary alcohol 65 under Mitsunobu conditions (chloroacetic acid (10 equiv), triphenylphosphine (10 equiv), and DEAD (10 equiv) in benzene at 23 °C) afforded a mixture of two products (Scheme XV). 63 In contrast to the chemistry described in Section I of this chapter, the ester product in which the allylic transposition was effected (97), along with the inseparable direct inversion product 98, were obtained in an approximately 2:3 ratio. The mixture of products was then subjected to the saponification conditions of potassium carbonate in methanol at O °C to provide an inseparable mixture of alcohols 9 9 and 100 in 80% yield from the alcohol 6 5. Treatment of the mixture of 140 96 13 t-BuC02 t-BuC02 II i7H i7 11 H TMSO,,. CHO CHO 8 11 10 13 Figure 1. 11 10 96 Ball and Stick Depictions of Ring-Closure Substrates 13 and 96. 141 Scheme XV CIC~C02H, PPha, DEAD, Cs~, 23 •c 11 H HO,... CH(OCl-l:i) 2 .: T8SO 65 H3C,,. 0 H3Cxo,•· 11 i ~CO:i. CH3OH, 0 °C 11 + H CH(OCH 3)2 80% (two steps) TBSO..: O 2CCH 2CI 97 H CIH 2CCO2 CH(OCH:J) 2 98 2:3 ratio Hij{ H C •• o••· TIPSOTf, 2,6-lutidine, 3 11 i H CH 2C'2, -78 °C 11 + H CH(OCH 3l2 CH(OCH:Jh ..: TBSO OH 99 100 2:3 ratio H3CXO H3CXO H3C H3C O''' 11 i H CH(OCHJl2 ., TBSO OTIPS 101 (55% of theory) 11 + H o•• 11 + CH(OCH 3l:! OCH:J TBSO_. H .: OTIPS 102 (37% of theory) TBSO 100 (100% of theory) 142 alcohols with triisopropylsilyl trifluoromethanesulfonate (TIPSOTf, 10 equiv) and 2,6lutidine (20 equiv) in dichloromethane at - 78 °C afforded a now separable mixture of three products. 73 The unreacted tertiary alcohol 100 was recovered quantitatively, and the TIPS ether 101, derived from the rearranged alcohol 99, was isolated in 55% yield. In addition, the methyl dienol ether 102 was obtained in 37% yield. The dimethyl acetal of purified TIPS ether 101 was hydrolyzed by reaction with p-TsOH in acetone at 23 °C to afford the a,~-unsaturated aldehyde 103 in 61 % yield. 65 Intramolecular acetylide addition within 103 was attempted using both LiN(TMS) 2 (16 equiv) and CeC1 3 (3 equiv) in THF at -78 °C 13 ' 19 and KN(TMS) 2 (6 equiv) and LiBr (0.5 equiv) in THF at -78 °C. Neither of these sets of reaction conditions provided any of the desired nine-membered ring product. Accordingly, this approach was abandoned. H3CXO H3CXO H3 C H3 C 0 1•· 11 i H CH(OCH 3h 0''' II i H fr TsOH, acetone, 23 °C CHO 61% .;: .;: TBSO OTIPS OTIPS TBSO 103 101 Studies with Diastereomeric Nine-Membered Ring Intermediates A potentially significant difference between the allylic transposition substrates used for the preparation of model system 5 13 and those employed in the studies described in Chapter 2 is the stereochemistry at C-1 and C-8 relative to the stereochemistry of the C-4 C-5 epoxide (cf. 14b and 54, Ch. 1 and Ch. 2). As the allylic rearrangement in the conversion of 14b to 15 proceeded in a suprafacial manner, it was of interest to determine whether a correspondingly more functionalized intermediate such as 104 would be a substrate for the trifluoroacetic acid-mediated allylic transposition. To examine this 143 possibility, the synthesis of intennediates possessing this stereochemical framework was initiated. 1. TMSCI II 2. TFA 11 14b 15 0 o=< 0'' 11 11 1. TMSCI 11 2. TFA OH cf 0 H3C O ~ O H ,.._,.. ______ ,... ? OH o~· o 02CCF3 yv H3C O ~ O H CH 3 CH 3 104 ~ The strategy employed for the preparation of this series of compounds is given in Scheme XVI. Alcohol 104 was envisioned as being the product of the previously developed intramolecular acetylide addition chemistry within an a,~-unsaturated alcohol such as 105. A key step in the preparation of 105 would be a Mitsunobu inversion62 of the C-11 secondary alcohol derived from 106 using the naphthoic acid 22 as the nucleophile. Intermediate 106 was envisioned as arising from the diastereoselective 144 Scheme XVI 11 11 H CHO 104 105 0 ~ CH(OCH,J, H + CHO TBSO H TBS 20 TBSO 106 (-)-21 145 coupling of the epoxydiyne 20 and the enone dimethyl acetal (-)-21, the enantiomer of the enone (+)-21 employed for the synthesis of the substrates discussed in Chapter 2 and the first two sections of this chapter. To gain entry into this series of compounds, the preparation of the enone dimethyl acetal (-)-21 was prepared from the known enantiomer of (+)-33, 35 enone (-)-33. 39 Treatment of (-)-33 with trimethylsilyl phenyl selenide (1.5 equiv) and catalytic 1MSOTf (0.2 equiv) followed by addition of freshly distilled trimethyl orthoformate (4 equiv) and in situ oxidation and elimination with hydrogen peroxide and pyridine afforded (-)-21 in 73% yield. 36 p 0 0 i. PhSeTMS, TMSOTf, CH 2Cii, -78 °C ii. HC(OCH:i)3 , -25 ➔ -20 °C TBSO ~CH(OCH,J, TBSO (-)-33 (-)-21 73% It was necessary to protect the 2-hydroxy group of the naphthoic acid 22 prior to its employment as a nucleophile in the planned Mitsunobu inversion. Accordingly, the methyl ester 45 was treated with MEM chloride (10 equiv) and diisopropylethylamine (20 equiv) in dichloromethane at O °C to provide the MEM ether in 98% yield. 55 The ester was subsequently saponified with sodium hydroxide (75 equiv) in a (3:1) mixture of methanol and water at 80 °C to afford the acid 108 in 90% yield. 0 0 OCH3 H3CO~OH ~ CH 3 45 1. MEMCI, i-Pr2NEt, CH2Cl2, 0 °C 2. NaOH, CH 30H!Hp (3:1), 80 °c 88% OH H3C O ~ O M E M ~ CH 3 108 146 Treatment of epoxydiyne 20 (1.05 equiv) with LiN(1MS) 2 (1.05 equiv) in toluene at -78 CC followed by addition of enone dimethyl acetal (-)-21 (1 equiv) afforded the tertiary alcohol 109 as a single diastereomer in 54% yield (Scheme XVII). Removal of the TBS groups by treatment with TBAF (3 equiv) in THF at O CC afforded diol 110. 51 Selective inversion of the secondary alcohol under Mitsunobu conditions utilizing acid 108 (1.2 equiv), triphenylphosphine (1.2 equiv), and DEAD (1.2 equiv) in benzene at 23 'C provided ester 111 in 70% yield. 62 As it was not clear at this juncture whether the formation of the nine-membered ring would occur in analogy to the other systems, the introduction of the ethylene carbonate was forgone in favor of arriving more directly at a ring-closure substrate. The dimethyl acetal of 111 underwent hydrolysis with p-TsOH in acetone at 23 CC to afford the a,~-unsaturated aldehyde, and the tertiary alcohol was protected as a trimethylsilyl ether with TMSOTf (5 equiv) and 2,6-lutidine (10 equiv) in dichloromethane at -78 °C to provide the ring-closure substrate 113 in 77% overall yield from 111. 54 Treatment of a suspension of the intermediate 113 and cerium(Iln chloride (3 equiv) in THF at -78 °C with LiN(1MS) 2 afforded the ring-closed secondary alcohol 114 in 59% yield, in complete analogy to prior substrates; 13•19 however, a large excess of the base (9 equiv) was required for the reaction to proceed to completion. The nine-membered ring-containing product 114 as well as subsequent intermediates in this diastereomeric series, were found to be more unstable than the corresponding intermediates having the opposite stereochemistry at C-1 and C-8 (cf. Ch. 2 and Ch. 3, Section I). Even when stored in a solid benzene matrix (-20 °C) and in the presence of the radical inhibitor 5hydroxy-4-tert-butyl-2-methylphenyl occurred in a matter of days. sulfide (BHMS), 74 noticeable decomposition 147 Scheme XVII 0 'l\ H3cx H3~ 0 ,,. _/),__ H ~~ U! H i. LiN(TMSk, PhCH 3, -78 °C II i ii. (-)-21 TBS 54% 20 TBSO 109 H3CXO H3C o••· Bu4NF, THF, O° C 11 99"/o i 108, PPh3, DEAD, Cs~, 23 °C H CH(OCH 3h 70% HO 110 II i 1. p-TsOH, acetone, 23 °c 2. TMSOTf, 2,6-lutidine, CH2CI 2, -78 °C 77% LiN(TMS)2, CeCl3, THF,-78 °C 59% 11 11 II i 148 Conversion of the cyclized product 114 to its bis-1MS derivative 115 was accomplished in quantitative yield by treatment with 1MSOTf (10 equiv) and 2,6-lutidine (20 equiv) in dichloromethane at -78 °C. 54 Reaction of the ether 115 with trifluoroacetic acid in dichloromethane (1:5) at O °C, 13 however, did not product the desired allylic transposition product Simple desilylation of the secondary alcohol was observed instead. 11 11 TMSOTf, 2,6-lulidine, II 11 CH 2 Cl2 , -78 °C 99% The rearrangement chemistry of intermediates in this series was also examined by alternative activation of the C-1 tertiary alcohol. Alcohol 114 was desilylated by treatment with triethylamine trihydrofluoride (3 equiv) in THF at O °C, 32 and the product dial (116) was selectively silylated with TBSOTf (10 equiv) and 2,6-lutidine (20 equiv) in dichloromethane at-78 °C to provide intermediate 117. 58 Treatment of alcohol 117 with triflic anhydride and pyridine in dichloromethane at -78 °C resulted in decomposition of the substrate. Reaction of 117 with methanesulfonic anhydride (10 equiv, 25 equiv Et3N, dichloromethane, 0 °C) and methanesulfonyl chloride (6 equiv, 25 equiv Et 3N, dichloromethane, 0 °C)59 afforded the rearranged mesylate 118 and chloride 119, respectively, each having trans stereochemistry between the C-10 and C-11 centers. Neither of these rearranged products, however, could be converted to a 149 11 11 11 11 2. TBSOTf, 2,6-lutidine, CH 2a 2, -78 °C useful intermediate to complete the synthesis of 6. The tertiary alcohol of intermediate 11 7 could also be functionalized as a trifluoroacetate, trichloroacetate, acetate, or ptoluenesulfinate (1: 1 mixture of diastereomers). Attempted rearrangement of these activated intermediates under thermal conditions resulted in decomposition of the substrate in all cases examined, and attempted Lewis-acid catalyzed rearrangement of the derived acetate resulted in either loss of the silyl protecting group (EtA1Cl2, dichloromethane, -78 °C)75 or recovery of the starting acetate (BF3•OEt2, dichloromethane, -78 ➔ 23 °C; TMSOTf, dichloromethane, -78 ➔ 23 °C).76 11 0 .::· w 11 0 A H3C O ~ O M E M CH3 118 R = OSO2CH3 119 R=CI 150 The inability to effect the requisite stereoselective allylic rearrangement of any of the intermediates prepared in this series prompted the discontinuation of this approach in favor of an alternative approach to the introduction of the C-10 and C-11 substituents with the proper stereochemistry. 151 Experimental Section General procedures. All reactions were performed in flame-dried round bottom or modified Schlenk (Kjeldahl shape) flasks. The flasks were fitted with rubber septa and contained a positive pressure of argon unless otherwise stated. Stainless steel syringes or cannula were used to transfer air- and moisture-sensitive materials. Concentration in vacuo was accomplished by rotary evaporation at water aspirator pressure (approximately 25 torr). Flash chromatography was carried out as described by Still et al., employing 230400 mesh silica gel. 29 Analytical thin-layer chromatography was performed using glass plates pre-coated with 0.25 mm 230-400 mesh silica gel impregnated with fluorescent indicator (254 nm). Thin-layer chromatography plates were visualized by exposure to ultraviolet light (noted as 'UV') and/or by exposure to an acidic solution of p-anisaldehyde (noted as 'anisaldehyde') followed by heating on a hot plate. Materials. exceptions. benzophenone Commercial reagents were used as received, with the following Ethyl ether and tetrahydrofuran (THF) were distilled from sodium ketyl. Dichloromethane, benzene, toluene, acetonitrile, N,N- diisopropylethylarnine, hexarnethyldisilazane, 2,6-lutidine, pyridine, and triethylarnine were distilled from calcium hydride at 760 torr. Anhydrous cerium(III) chloride was prepared from the heptahydrate by heating at 100 ·c and 1 torr for 12 hours. Methanesulfonyl chloride was distilled from phosphorous pentoxide at 760 torr. 152 Trifluoromethanesulfonic anhydride and trimethylsilyl trifluoromethanesulfonate were stored in a glove box in round bottom flasks fitted with polycarbonate or glass stoppers. The molarity of n-butyllithium solutions was determined by titration with 2,6-di-tert-butyl4-methylphenol using fluorene as an indicator (average of three determinations). Where indicated, fresh solutions of lithium hexamethyldisilazide were prepared by the addition of a solution of n-butyllithium (1.0 eq) in hexanes to a solution of hexamethyldisilazane (1.0 eq) in hexanes at-20 ·c, followed by warming to room temperature. Instrumentation. Infrared (IR) spectra were obtained using a Perkin-Elmer 1600 Ff-IR spectrophotometer referenced to a polystyrene standard. Data are presented as follows: frequency of absorption (cm· 1), intensity of absorption (v = very, s = strong, m = medium, w = weak) and assignment where appropriate. Proton nuclear magnetic resonance (1H NMR) spectra and carbon nuclear magnetic resonance {1 3C NMR) spectra were recorded on either a General Electric QE-300 (300 MHz), a JEOL GX-400 (400 MHz) or a Bruker AM-500 (500 MHz) NMR spectrometer; chemical shifts for protons are reported in parts per million downfield from tetramethylsilane and are referenced to residual protium in the NMR solvent (CHC1 3: o7.26, C D H: o7.20, CDHC1 o5.29, CD HOD: 6 5 2: 2 o 3.30). Data are represented as follows: chemical shift, multiplicity (br = broad, s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, obscured = obscured by solvent or other signals, abq = ab quartet), integration, coupling constant in Hertz (Hz), and assignment. Optical rotations were determined on a Jasco DIP-181 digital polarimeter equipped with a sodium lamp source. HPLC purification was carried out on a Waters Delta Prep 3000 HPLC equipped with a Waters 994 programmable photodiode array detector set at 240 nm and either a Beckman ODS C18 column (10 mm x 25 cm, for analytical HPLC) or a Vydac 201HS1022 C18 reverse-phase column (22 mm x 25 cm, for preparative HPLC). Melting points were determined on a Biichi SMP-20 melting point apparatus, and are uncorrected. High resolution mass spectra were obtained either at the University of Califomia, Riverside Mass Spectrometry Facility; the Midwest Center for Mass 153 Spectroscopy, Lincoln, Nebraska; the University of California, Los Angeles Mass Spectrometry Facility; or the California Institute of Technology Mass Spectrometry Facility. 154 HO ~~ TMSOTf, 2,6-lutidine, CH2 Cl2 , -78 °C ::~ ~antitative H TBS H 32 TBS 74 Bis-TMS ether 7 4 - 2,6-Lutidine (8.75 rnL, 8.04 g, 75.1 mmol, 20 equiv) and trirnethylsilyl trifluoromethanesulfonate (8.71 rnL, 10.0 g, 45.0 mmol, 12 equiv) were added sequentially via syringe to a solution of diol 32 (1.00 g, 3.75 rnmol, 1 equiv) in dichloromethane (100 mL) at -78 °C. The reaction was maintained at -78 °C for 1.5 h. Triethylarnine (10 rnL) and methanol (10 rnL) were added, and the reaction mixture was wanned to 23 °C and partitioned between water (50 mL) and hexanes (50 mL). The layers were separated, and the aqueous layer was further extracted with hexanes (2 25-rnL portions). The combined organics were washed with saturated sodium chloride (50 rnL), and were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (10% ethyl acetate in hexanes) afforded the bis-TMS ether 7 4 (1.49 g, quantitative) as a pale yellow solid, mp 59.5-60.5 °C. 155 3.98-3.93 (m, 2H, C9 H), 3.84 (s, IH, C5 H), 3.80 (dd, IH, J = l 1.0, 6.2 Hz, C8 H), 2.03 (s, IH, Cl H), 1.04 (s, 9H, OSiC(CH 3)iCH 3) 2), 0.16-0.12 (complex, 24 H, OSiC(CH 3) 3(CH) 3, 2 x OSi(CH 3) 3). FI1R (thin film), cm-1: 3432 (m, C=C-H), 2956 (m), 2840 (m), 2120 (w, C=C), 1249 (s), 1149 (s). 1LC (20% EtOAc in Hexanes) Rf: 74: 0.61 (anisaldehyde) 156 TMSO ™00~ i. LiN(TMS)2 , PhCH 3 , -78'C ii. (+)-21 H TBS 74 60% 11 HO,,.. TBS 12 CH(OCH~2 TBSO.:-" 10 75 Alcohol 75 Epoxydiyne 74 (2.78 g, 6.76 mmol, 1.05 equiv) in toluene (20 mL) was added over a 25 min period to a solution of lithium hexamethyldisilazide (6.96 mL of a 1.0 M solution in hexanes, 6.96 mmol, 1.05 equiv) in toluene (20 mL) at -78 °C. The resultant solution was maintained at-78 °C for an additional 20 min, and a solution of enone (+)-21 (1.90 g, 6.64 mmol, 1.0 equiv) in toluene ( 20 mL) was added over a 10 min period. The reaction mixture was stirred at -78 °C for 10 min, and saturated aqueous ammonium chloride (50 mL) was added to quench excess base. The reaction mixture was warmed to 23 °C and partitioned between water (50 mL) and 1:1 ethyl acetate/hexanes (50 mL). The layers were separated and the aqueous layer was further extracted with 1: 1 ethyl acetate/hexanes (2 25-mL portions). The combined organics were washed with saturated aqueous sodium chloride (25 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (5% ethyl acetate in hexanes) provided the alcohol 75 (2.76 g, 60%) as a yellow oil, along with recovered epoxydiyne (785 mg, 25% ). 157 6.17 (t, lH, J = 1.71 Hz, C-10 H), 5.42 (t, lH, J = 1.46 Hz, C8 H), 4.88 (m, lH, Cll H), 4.05-4.02 (m, lH, C13 H), 3.92-3.95 (m, lH, C14 H), 3.93 (s, lH, C5 H), 3.85 (dd, lH, J = 10.99, 6.11 Hz, C14 H), 3.22 (s, 3H, CH(OCH 3) 2 ), 3.21 (s, 3H, CH(OCH 3) 2), 3.18 (dd, lH, J = 13.43, 7.08 Hz, C12 J3H), 2.55 (dd, lH, J = 13.43, 5.13 Hz, C12 cxH), 1.06 (s, 9H, SiC(CH 3)lCH 3) 2), 0.97 (s, 9H, SiC(CH 3)iCH 3) 2 ), 0.21 (s, 6H, SiC(CH 3)iCH 3) 2 ), 0.17 (s, 9H, OSi(CH 3) 3), 0.14 (s, 9H, OSi(CH 3) 3), 0.09 (s, 3H, SiC(CH 3\(CH 3) 2), 0.07 (s, 3H, SiC(CH 3\(CH 3) 2). FTIR (thin film), cm· 1: 3521 (w, OH), 2955 (s), 2184 (w, C=C), 1464 (m), 1360 (m), 1252 (s), 1080 (s), 964 (m). 1LC (20% EtOAc in Hexanes) Rf. 74: 0.65 (anisaldehyde) (+)-21: 0.31 (anisaldehyde) 75: 0.50 (anisaldehyde) 158 11 HO,,.. TBS Et3N•3HF, THF, o °C CH(OCH 3h 11 82% 75 CH(OCH3)2 12 .: TBSO ~ TBSO TBS HO,,.. 10 76 Triol 7 6 Triethylamine trihydrofluoride ( 1.91 mL, 1.89 g, 11.8 mmol, 3 equiv) was added via syringe to a solution of alcohol 75 (2.73 g, 3.92 mmol, 1 equiv) in THF (228 mL) at 0 °C. The reaction was kept at O °C for 15 min, and saturated aqueous sodium bicarbonate (50 mL) was added. The reaction mixture was warmed to 23 °C and the layers were separated. The aqueous layer was extracted with ethyl acetate (2 25-mL portions). The combined organics were washed with saturated aqueous sodium chloride (50 mL), dried over sodium sulfate, and concentrated. The residue was purified by flash column chromatography (50% ethyl acetate in hexanes grading to ethyl acetate) to provide the triol 76 (1.79g, 82%) as a pale yellow oil. 159 6.16 (t, lH, J = 1.3 Hz, ClO H), 5.36 (m, lH, C-8 H), 4.85 (m, lH, Cl 1 H), 4.36 (br s, lH, Cl OH), 3.92-3.63 (complex, 3H, C13 and C14 H), 3.65 (s, lH, C5 H), 3.23 (s, 3H, CH(OCH 3) 2 ), 3.21 (s, 3H, CH(OCH 3) 2 ), 3.85 (dd, lH, J = 10.99, 6.11 Hz, C14 H), 3.13 (dd, lH, J = 13.4, 7.2 Hz, C12 ~H), 2.80 (br s, lH, OH), 2.48 (dd, lH, J = 13.5, 5.1 Hz, C12 aH), 2.22 (br s, lH, OH), 1.06 (s, 9H, SiC(CH 3) 3(CH 3) 2), 0.97 (s, 9H, SiC(<:;H 3)iCH 3) 2), 0.22 (s, 3H, SiC(CH 3)iCH 3) 2), 0.21 (s, 3H, SiC(CH 3)iCH 3) 2), 0.09 (s, 3H, SiC(CH 3)iCH 3) 2), 0.08 (s, 3H, SiC(CH 3)iCH 3) 2). FI1R (thin film), cm·': 3337 (m, OH), 2930 (s), 2857 (m), 2178 (w, C=C), 1463 (m), 1360 (m), 1252 (m), 1193 (m), 1109 (s), 1049 (s). 1LC (50% EtOAc in Hexanes) Rf. 75: 0.97 (anisaldehyde) 76: 0.067 (anisaldehyde) 160 11 HO,,,. TBS COi, THF, O ➔ 23 °c CH(OCH3)2 79% .::· 11 HO,,.. .:: TBSO TBSO 76 TBS CH(OCH 3k 12 10 n Carbonate 7 7 Carbonyldiimidazole (313 mg, 1.94 mmol, 0.6 equiv) was added in one portion to a solution of triol 76 (1.78 g, 3.22 mmol, 1 equiv) in dry THF (66 mL) at 0 °C. The resultant solution was stirred at 0 °C for 20 min, and another portion of carbonyldiimidazole (313 mg, 1.94 mmol, 0.6 equiv) was added. The reaction mixture was maintained at 0 °C for an additional 10 min, warmed to 23 °C and held at that temperature for 2.25 h. The reaction mixture was partitioned between water (50 mL) and ethyl acetate (50 mL). The layers were separated, and the aqueous layer was further extracted with ethyl acetate (2 30-mL portions). The combined organics were washed with saturated aqueous sodium chloride (50 mL), dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (50% ethyl acetate in hexanes) to afford carbonate 77 (1.47 g, 79%) as a colorless foam . 161 6.17 (br s, lH, ClO H), 5.38 (br s, lH, C8 H), 4.90 (m, lH, Cl 1 H), 4.08 (br s, lH, Cl OH), 3.94 (dd, lH, J = 8.9, 4.8 Hz, C13 H), 3.37 (t, lH, J = 8.4 Hz, C14 H), 3.24 (s, 3H, CH(OCH 3)2), 3.21 (s, 3H, CH(OCH 3)2), 3.19-3.10 (m, 2H, C14 H and C12 J3H), 3.02 (s, lH, CS H), 2.50 (dd, lH, J = 13.3, 5.5 Hz, C12 aH), 1.05 (s, 9H, SiC(CH 3)/CH 3) 2), 0.96 (s, 9H, SiC(CH 3)/CH 3) 2), 0.21 (s, 3H, SiC(CH 3)iCH 3) 2), 0.20 (s, 3H, SiC(CH 3)/CH 3) 2), 0.10 (s, 3H, SiC(CH 3)/CH 3) 2), 0.089 (s, 3H, SiC(CH 3)/CH 3)i). FTIR (thin film), cm· 1: 3498 (m, OH), 2954 (s), 2857 (m), 2178 (w, C=C), 1823 (s, C=O), 1727 (m), 1468 (m), 1382 (m), 1361 (m), 1253 (m), 1082 (s). TLC (50% EtOAc in Hexanes) Rf. 76: 0.04 (anisaldehyde) 77: 0.48 (anisaldehyde) 162 0 o=( O''' II HO,,.. ~ 11 TBS HO,.. 90% 12 TBSO~ n 78 Free acetylene 7 8 Tetrabutylammonium fluoride ( 2.53 mL of a 1.0 M solution in TI-IF, 2.53 mmol, 2 equiv) was added via syringe to a solution of carbonate 77 (735 mg, 1.26 mmol, 1 equiv) in THF (85 mL) at -63 °C. The pale purple suspension was stirred at -63 °C for 30 min, pH 7.2 phosphate buffer (20 mL) was added, and the reaction mixture was warmed to 23 °C. The reaction mixture was partitioned between water (50 mL) and ethyl acetate (50 mL). The aqueous layer was further extracted with ethyl acetate (2 25-mL portions), and the combined organics were washed with saturated aqueous sodium chloride (50 mL), dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (25% ethyl acetate in hexanes grading to 50% ethyl acetate in hexanes), providing the free acetylene 78 (1.06 g, 90%) as a colorless oil. 163 6_13 (t, lH, J = 1.7 Hz, ClO H), 5.35 (t, lH, J = 1.7 Hz, C8 H), 4.91 (m, lH, Cll H), 4.10 (s, lH, Cl OH), 3.91 (dd, lH, J = 9.0, 4.4 Hz, C13 H), 3.33 (t, lH, J = 8.7 Hz, C14 H), 3.23-3.15 (obscured, lH, C12 J3H), 3.19 (s, 3H, CH(OCH 3)i), 3.17 (s, 3H, CH(OCH 3) 2), 3.09 (dd, lH, J = 8.2, 4.5 Hz, C14 H), 2.86 (d, lH, J = 1.6 Hz, C5 H), 2.50 (dd, lH, J = 13.2, 5.6 Hz, C12 aH), 1.98 (d, lH, J = 1.6 Hz, C7 H), 0.96 (s, 9H, OSiC(CH 3)iCH 3) 2), 0.10 (s, 6H, OSiC(CH 3\(CH 3) 2) FTIR (thin film), cm- 1: 3471 (m, OH), 3277 (w, C=C-H), 2932 (m), 2856 (m), 1820 (s, C=O), 1470 (w), 1360 (m), 1159 (m), 1080 (s). TLC (50% EtOAc in Hexanes) Rf 77: 0.48 (anisaldehyde) 78: 0.40 (anisaldehyde) 164 0 o=( o•· 11 p-TsOH, acetone, 23°c H CHO HO,,.. 74% TBSO.: TBSO.: 78 10 79 Aldehyde 79 p-Toluenesulfonic acid (75 mg) was added in one portion to a solution of dimethyl acetal 78 (900 mg, 1.94 mmol, 1 equiv) in acetone (30 mL). The resultant yellow solution was stirred at 23 °C for 15 min and the p-toluenesulfonic acid was neutraliz.ed with saturated aqueous sodium bicarbonate (30 mL). The reaction mixture was extracted with 1:1 ethyl acetate/hexanes (3 30-mL portions), and the combined organics were washed with saturated sodium chloride (50 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (30% ethyl acetate in hexanes grading to 50% ethyl acetate in hexanes) provided aldehyde 79 (602 mg, 74%) as a colorless solid. 165 9-22 {s, lH, C8 H), 6.08 (t, lH, J = 1.7 Hz, ClO H), 5.02 (t, lH, J = 1.7 Hz, Cl 1 H), 3.91 (s, lH, Cl OH), 3.85 (dd, lH, J = 9.2, 4.0 Hz, C13 H), 3.30 (dd, lH, J = 9.2, 8_ 1 Hz, C14 H), 3.10 (dd, lH, J = 12.7, 6.9 Hz, C12 ~H), 3.02 (dd, lH, J = 8.1, 4.0 Hz, C14), 2_78 (d, lH, J = 1.7 Hz, C5 H), 2.36 (dd, lH, J = 12.7, 7.3 Hz, C12 aH), 2.15 (d, lH, J = 1.7 Hz, C7 H), 0.98 (s, 9H, OSiC(CH 3)/CH 3) 2), 0.19 (s, 3H, OSiC(CH 3MCH 3) 2), 0.17 (s, 3H, OSiC(CH 3MCH 3) 2). FI1R (thin film), cm- 1: 3507 (w, OH), 3285 (m, C=C-H), 2953 (m), 2857 (m), 2130 (w, C=C), 1819 (s, carbonate C=O), 1684 (m, aldehyde C=O), 1472 (w), 1359 (m), 1084 (s). 1LC (50% EtOAc in Hexanes) Rf: 78: 0.34 (anisaldehyde) 79: 0.42 (UV, anisaldehyde) 166 0 o=< o=< TMSOTf, 2,6-lutidine, II HO,,.. CH 2Cl:1, -78 °C H CHO 11 TMSO,,. 99% 12 .H CHO TBSO.: 79 80 TMS ether SQ 2,6-Lutidine (1.38 mL, 1.27 g, 11.8 mmol, 10 equiv) and trimethylsilyl trifluoromethanesulfonate (1.14 mL, 1.31 g, 5.91 mmol, 5 equiv) were added sequentially via syringe to a solution of aldehyde 79 (495 mg, 1.18 mmol, 1 equiv) in dichloromethane (28 mL) at-78 °C. The resultant solution was maintained at -78 °C for an additional 1 h, and then excess trimethylsilyl trifluoromethanesulfonate was quenched by the addition of triethylamine (6 mL) and methanol (6 mL). The reaction mixture was partitioned between water (25 mL) and 1:1 ethyl acetate/hexanes (25 mL). The layers were separated, and the aqueous layer was further extracted with 1:1 ethyl acetate/hexanes (2 25-mL portions). The combined organics were washed with saturated aqueous sodium chloride (50 mL), dried over sodium sulfate and concentrated. ·Purification of the residue by flash column chromatography (25% ethyl acetate in hexanes) provided the TMS ether 80 (575 mg, 99%) as a pale yellow oil. 167 9.61 (s, lH, C8 H), 6.29 (d, lH, J = 1.6 Hz, ClO H), 4.94 (td, lH, J = 8.3, 1.4 Hz, Cl 1 H), 4.00 (dd, lH, J = 9.1, 4.1 Hz, C13 H), 3.38 (t, lH, J = 8.7 Hz, C14 H), 3.23 (dd, lH, J = 12.7, 7.1 Hz, C12 ~H), 3.07 (m, lH, C14), 2.80 (s, lH, C5 H), 2.39 (dd, lH, J = 12.7, 6.6 Hz, C12 a.H), 2.18 (d, lH, J = 1.4 Hz, C7 H), 0.98 (s, 9H, OSiC(CH 3)/CH3) 2), 0.37 (s, 9H, OSi(CH 3)3), 0.19 (s, 3H, OSiC(CH 3)iCH 3) 2), 0.17 (s, 3H, OSiC(CH 3)iCH 3) 2). FTIR (thin film), cm· 1: 3285 (w, C=C-H), 2955 (m), 2857 (m), 2237 (w, C=C), 2131 (w, C=C), 1822 (s, carbonate C=O), 1696 (m, aldehyde C=O), 1254 (s), 1130 (m), 1084 (s). 1LC (50% EtOAc in Hexanes) Rf 79: 0.47 (UV, anisaldehyde) 80: 0.64 (UV, anisaldehyde) 168 o={ O'' LiN(TMS)2 , CeC1 3 , 11 TMSO,,.. H CHO THF,-78 °C 11 11 55% 80 Cyclic alcohol s t A suspension of aldehyde 80 (116 mg, 0.236 mmol, 1 equiv) and anhydrous cerium(III) chloride (175 mg, 0.709 mmol, 3 equiv), in THF (15 mL) was stirred vigorously under argon at 23 ·c for 10 min. The mixture was cooled to -78 °C, and freshly prepared lithium hexamethyldisilazide (0.236 mL of a 1.0 M solution in hexanes, 0.236 mmol, 1.0 equiv) was added dropwise via syringe. The reaction was stirred at -78 °C for 10 min, and excess base was quenched with saturated aqueous ammonium chloride (5 mL). The reaction mixture was warmed to 23 °C and partitioned between water (25 mL) and 1:1 ethyl acetate/hexanes (25 mL). The layers were separated and the aqueous layer was further extracted with 1:1 ethyl acetate/hexanes (2 25-mL portions). The combined organics were dried over sodium sulfate and concentrated The residue was purified by flash column chromatography (25% ethyl acetate in hexanes) to afford cyclic alcohol 81 (64 mg, 55%) as a pale orange oil. 169 5.95 (t, lH, J = 1.66 Hz, ClO H), 5.17 (m, lH, C8 H), 4.67 (m, lH, Cll H), 3.68 (m, lH, C13 H), 3.22 (m, 2H, C14 H), 2.94 (dd, lH, J = 13.08, 7.03 Hz, C12 PH), 2.78 (s, lH, C5 H), 2.18 (dd, lH, J = 13.06, 5.59 aH), 0.93 (s, 9H, OSiC(CH 3)iCH 3) 2), 0.30 (s, 9H, Hz, C12 OSi(CH 3) 3), 0.00 OSiC(CH 3) 3(CH 3) 2), 3H, (s, -0.01 (s. 3H, OSiC(CH 3\(CH 3) 2). Fl1R (thin film), cm· 1: 3446 (w, OH), 2954 (m), 2857 (m). 2202 (w, C=C), 1822 (s, carbonate C=O), 1361 (m), 1253 (m), 1080 (s) cm·1 1LC (50% EtOAc in Hexanes) Rf. 80: 0.62 (UV, anisaldehyde) 81: 0.54 (anisaldehyde) 170 0 o=< 0'' II 11 57% TBSO.: 81 Diol 82 Triethylamine trihydrofluoride (0.058 mL, 57 mg, 0.35 mmol, 3 equiv) was added via syringe to a solution of cyclic alcohol 81 (58 mg, 0.118 mmol, 1 equiv) in THF (5 mL) at 0 °C. The resultant solution was held at 0 °C for an additional 2 h, and saturated aqueous sodium bicarbonate (3 mL) was added. The reaction mixture was warmed to 23 °C and extracted with ethyl acetate (3 25-mL portions). The combined organics were washed with saturated aqueous sodium chloride (25 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (50% ethyl acetate in hexanes grading to ethyl acetate) afforded diol 82 (28 mg, 57%) as a yellow powder. 171 5.86 (t, lH, J = 1.80 Hz, ClO H), 5.83 (t, lH, J = 1.57 Hz, C8 H), 5.23 (m, lH, Cl l H), 4.38 - 4.19 (complex, 2H, C13 H, one C14 H), 3.79 (m, lH, C14 H), 3.64 (s, lH, C5 H), 2.85 (dd, lH, J = 13.27, 7.07 Hz, C12 ~H), 1.87 (dd, lH, J = 13.34, 5.42 Hz, C12 aH), 0.89 (s, 9H, OSiC(CH 3)iCH 3) 2), 0.09 (s, 3H, OSiC(CH 3)iCH 3) 2), 0.08 (s, 3H, OSiC(CH 3) 3(CH 3) 2). FTIR (thin fihn), cm· 1: 3421 (s, OH), 2929 (s), 2860 (m), 1750 (s, carbonate C=0), 1360 (m), 1290 (m), 1080 (s). 1LC (50% EtOAc in Hexanes) Rf. 81: 0.51 (anisaldehyde) 82: 0.30 (anisaldehyde) 172 11 II TPSCI, Et3 N, DMAP, H 11 CH2C1 2 , O➔ 23 °C 43% H 12 .:· TBS<:/ TBSO 82 11 10 83 Tertiazy alcohol 8 3 Triphenylsilyl chloride (23 mg, 0.078 mmol, 1.3 equiv) was added in one portion to a solution of the diol 82 (25 mg, 0.060 mmol, 1 equiv), triethylamine (0.042 mL, 30 mg, 0.30 mmol, 5 equiv) and 4-dimethylaminopyridine (4 mg, 0.030 mmol, 0.5 equiv) in dichloromethane (2 mL) at 0 °C. The reaction mixture was maintained at 0 °C for 10 min and warmed to 23 °C for 2.5 h. The reaction mixture was partitioned between water (5 mL) and ethyl acetate (5 mL). The layers were separated, and the aqueous layer was further extracted with ethyl acetate (2 5-mL portions). The combined organics were washed with saturated aqueous sodium chloride (15 mL), dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (20% ethyl acetate in hexanes grading to 50% ethyl acetate in hexanes) to afford the triphenylsilyl ether 83 (17 mg, 43%) as a pale yellow powder. 173 7.85 (m, 4H, OSi(C6H 5) 3), 7.73 (m, 4H, OSi(C 6H 5) 3),7.23 (m, 7H, OSi(C6H 5 ) 3), 5.86 (t, lH, J = 1.80 Hz, ClO H), 5.83 (t, lH, J = 1.57 Hz, C8 H), 5.23 (m, lH, Cl 1 H), 4.38 4.19 (complex, 2H, C13 H and one C14 H), 3.79 (m, lH, C14 H), 3.64 (s, lH, C5 H), 2.85 (dd, lH, J = 13.27, 7.07 Hz, C12 ~H), 1.87 (dd, lH, J = 13.34, 5.42 Hz, C12 aH), 0.89 (s, 9H, OSiC(CH 3)iCH 3) 2), 0.09 (s, 3H, OSiC(CH 3)iCH 3) 2), 0.08 (s, 3H, OSiC(CH 3)iCH 3) 2). FTIR (thin film), cm· 1: 3421 (s, OH), 2929 (s), 2860 (m), 1750 (s, carbonate C=O), 1360 (m), 1290 (m), 1080 (s). lLC (50% EtOAc in Hexanes) Rf. 82: 0.42 (anisaldehyde) 83: 0.66 (UV, anisaldehyde) 174 0 o=( o•· 11 TMSO,.. H CHO TBSCI, Et3N, DMAP, CH 2Cl2 , O °C II TMSO,,.. 12 H CHO 74% Aldehyde 86 tert-Butyldimethylsilyl chloride (112 mg, 0.742 mmol, 2 equiv) was added in one portion to a solution of aldehyde 51 (220 mg, 0.371 mmol, 1 equiv), triethylamine (1.03 mL, 7.42 mmol, 20 equiv), and 4-dimethylaminopyridine (30 mg) in dichloromethane (25 mL) at 0 0 C. The solution was stirred at 0 °C for 2.5 h and partitioned between 1:1 ethyl acetate/hexanes (50 mL) and water (50 mL). The layers were separated, and the aqueous layer was further extracted with 1:1 ethyl acetate/hexanes (2 25-mL portions). The combined organics were washed with saturated aqueous sodium chloride (50 mL), dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (20% ethyl acetate in hexanes grading to 50% ethyl acetate in hexanes) to afford aldehyde 86 (195 mg, 74%) as a colorless oil. 175 9.59 (s, lH, C8 H), 7.61 (d, lH, J = 9.08 Hz, C4" H), 7.19 (obscured, lH, C8" H), 7.01 (s, lH, C6" H), 6.91 (d, lH, J = 9.13 Hz, C3" H), 6.69 (s, lH, ClO H), 6.15 (m, lH, C11 H), 3.97 (dd, lH, J = 8.86, 4.82 Hz, C13 H), 3.57 (s, 3H, C7'' OCH 3), 3.41 (m, 2H, C14 H and C12 PH), 3.13 (dd, lH, J = 7.96, 4.92 Hz, C14 H), 2.86 (d, lH, J = 1.29 Hz, C5 H), 2.31 (s, 3H, C5" CH 3), 2.25 (d, lH, J = 1.27 Hz, C7 H), 1.13 (s, 9H, OSiC(CH 3) 3(CH3) 2), 0.31 (s, 9H, OSi(CH 3) 3), 0.29 (s, 3H, OSiC(CH 3MCH) 2), 0.27 (s, 3H, OSiC(CH 3MCH 3) 2). FTIR (thin film), cm· 1: 3281(w, C=C-H), 2955 (m), 2857 (m), 2131 (w, C=C), 1823 (s, carbonate C=O), 1728 (m, ester C=O), 1699 (m, aldehyde C=O), 1621 (m), 1410 (m), 1256 (s), 1094 (m). lLC (50% EtOAc in Hexanes), Rf. 51: 0.36 (UV, anisaldehyde) 86: 0.50 (UV, anisaldehyde) 176 0 o=< o•·· II TMSO,,,. i H LiN(TMS) 2 , CeCl 3 , 11 11 THF,-78°C 54% Cyclic alcohol 8 7 A suspension of aldehyde 86 (87 mg, 0.12 mmol, 1 equiv) and cerium(III) chloride (91 mg, 0.37 mmol, 3 equiv) in THF (6 mL) was stirred vigorously at 23 °C for 10 min and cooled to-78 °C. Lithium hexarnethyldisilazide (136 µL of a freshly prepared 1.0 M solution in hexanes, 0.136 mmol, 1.1 equiv) was added dropwise via syringe over 2 min. After maintaining the reaction at -78 °C for an additional 10 min, excess base was quenched by addition of saturated aqueous ammonium chloride (10 mL) and the reaction mixture was warmed to 23 °C. The reaction mixture was partitioned between 1: 1 ethyl acetate/hexanes (15 mL) and water (10 mL). The layers were separated, and the aqueous layer was further extracted with 1:1 ethyl acetate/hexanes (2 15-mL portions). The combined organics were washed with saturated aqueous sodium chloride (15 mL), and were dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (25% ethyl acetate in hexanes) to afford the cyclic alcohol 87 (47 mg, 54%) as a colorless oil. 177 7.57 (d, lH, J = 9.16 Hz, C4" H), 7.17 (s, lH, C8" H), 6.99 (m, lH, C6" H), 6.88 (d, lH, J = 9.16 Hz, C3" H), 6.36 (t, lH, J = 1.80 Hz, ClO H), 6.02 (m, lH, C11 H), 5.14 (br s, lH, C8 H), 3.56 (m, lH, C13 H), 3.55 (s, 3H, CT' OCH 3 ), 3.37 (dd, lH, J = 8.40, 5.84 Hz, C14 H), 3.23 (t, lH, J = 8.76 Hz, C14 H), 3.14 (dd, lH, J = 13.92, 7.32 Hz, C12 PH), 2.85 (s, lH, C5 H), 2.41 (dd, lH, J = 13.92, 4.76 Hz, C12 aH), 2.28 (s, 3H, C5" CH 3 ), 1.09 (s, 9H, OSiC(CH (CH 3 ) 3 3 ) 2 ), 0.26 (s, 3H, OSiC(CH 3)iCH 3) 2), 0.24 (s, 3H, OSiC(CH 3)iCH 3) 2), OSi(CH 3 ) 3 0.20 (s, 9H, ). 168.1, 158.9, 157.1, 153.5, 151.3, 136.5, 133.6, 127.2, 125.9, 123.9, 120.9, 118.1, 117.2, 101.0, 96.8, 87.9, 86.4, 85.0, 76.7, 76.2, 73.7, 65.6, 60.3, 58.6, 54.7, 52.5, 48.2, 25.7, 19.1, 18.3, 1.4, -4.2. FfIR (thin film), cm· 1 : 3459 (w, OH), 2954 (m), 1822 (s, carbonate C=O), 1724 (ester C=O), 1620 (m), 1409 (m), 1256 (s), 1096 (s), 842 (s). 178 1LC (50% EtOAc in Hexanes), Rf 86: 0.57 (UV, anisaldehyde) 87: 0.47 (fluoresces under UV, anisaldehyde) 179 0 o=<o•·· 11 11 H (±)-CSA, 1: 1 CH 3CN/H 2O, 23°c d o 75% H3CO~OTBS yu CH3 87 Diol 88 (±)-Camphorsulfonic acid (163 mg, 0.702 mmol, 5 equiv) was added in one portion to a solution of the cyclic alcohol 87 (99 mg, 0.140 mmol, 1 equiv) in 1:1 acetonitrile/water (26 mL) at 23 °C. The solution was stirred at 23 °C for 1 h, and extracted with 1:1 ethyl acetate/hexanes (3 25-mL portions). The combined organics were washed once with saturated aqueous sodium chloride (25 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (50% ethyl acetate in hexanes) afforded diol 88 (67 mg, 75%) as a yellow oil that rapidly darkened upon standing. 180 7.59 (d, lH, J = 8.60 Hz, C4" H), 7.14 (s, lH, C8" H), 7.01 (s, lH, C6" H), 6.90 (d, lH, J = 8.96 Hz, C3" H), 6.28 (s, lH, ClO H), 5.78 (m, lH, Cl 1 H), 4.99 (br s, lH, C8 H), 3.64 (m, lH, C13 H), 3.54 (s, 3H, C7'' OCH 3), 3.26 (m, 3H, C14 H, C12 aH), 2.94 (dd, lH, J = 15.20, 7.40 Hz, C12 ~H), 2.81 (s, lH, C5 H), 2.30 (s, 3H, C5" CH 3), 1.10 (s, 9H, OSiC(CH 3)iCH 3) 2), 0.26 (s, 6H, OSiC(CH 3)/CH 3) 2). 167.7, 158.5, 156.1, 150.8, 135.9, 135.2, 133.1, 123.5, 119.8, 117.8, 117.7, 116.8, 100.5, 96.3, 89.5, 86.0, 83.3, 75.7, 75.5, 73.6, 65.4, 60.1, 59.5, 58.2, 54.4, 52.5, 46.6, 25.3, 19.9, 18.7, 17.8, 13.5, -4.6, -4.7. TLC (50% EtOAc in Hexanes), Rf 87: 0.43 (fluoresces under UV, anisaldehyde) 88: 0.25 (fluoresces under UV, anisaldehyde) 181 0 o=<0"' 11 11 H 11 EtaSia, imidazole, 11 CH 2 0 2 , O°C o'.: 11 0 82% 0 0.: w H3C O ~ O T B S H3CO~OTBS ~ CH3 CH 3 88 4' 89 Triethylsilyl ether 8 9 Imidazole (57 mg, 0.84 mmol, 5 equiv) was added in one portion to a solution of the diol 88 (106 mg, 0.17 mmol, 1 equiv) in dichloromethane (8 mL) at 0 °C. Triethylsilyl chloride (31 µL, 28 mg, 0.18 mmol, 1.1 equiv) was added dropwise via syringe. The reaction was checked by thin layer chromatography (TLC, 50% ethyl acetate/hexanes), which indicated approximately 50% conversion. An additional portion of triethylsilyl chloride (16 µL, 14 mg, 0.094 mmol, 0.55 equiv) was added via syringe. The reaction was determined to be complete by TLC, and was diluted with 1: 1 ethyl acetate/hexanes (30 mL). The reaction mixture was then washed with water (2 15-mL portions). The combined aqueous layers were further extracted with 1: 1 ethyl acetate/hexanes (2 25-mL portions). The combined organics were washed with saturated aqueous sodium chloride (30 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (40% ethyl acetate in hexanes) afforded triethylsilyl ether 89 (103 mg, 82%) as a pale yellow oil. 182 7.58 (d, lH, J = 9.16 Hz, C4" H), 7.22 (s, lH, C8" H), 6.99 (m, lH, C6" H), 6.88 (d, lH, J = 9.16 Hz, C3" H), 6.51 (t, lH, J = 1.84 Hz, ClO H), 5.93 (m, lH, Cl 1 H), 5.49 (t, lH, J = 1.44 Hz, C8 H), 3.64 (dd, lH, J = 8.80, 5.48 Hz, C13 H), 3.59 (s, 3H, C7'' OCH3), 3.42 (dd, lH, J = 8.44, 5.52 Hz, C14 H), 3.34 (t, lH, J= 8.40 Hz, C14 H), 3.17 (dd, lH, J = 14.64, 7.68 Hz, C12 f3H), 2.82 (s, lH, C5 H), 2.43 (dd, lH, J = 14.64, 3.64 Hz, C12 a.H), 2.31 (s, 3H, C5" CH3), 1.11 (s, 9H, OSiC(CH 3\(CH 3) 2), 1.03 (t, 9H, J = 8.04 Hz, OSi(CH 2CH 3) 3), 0.69 (m, 6H, OSi(CH 2CH 3) 3), OSiC(CH 3)iCH 3) 2), 0.27 0.26 (s, 3H, (s, 3H, OSiC(CH 3)iCH 3) 2). 168.2, 159.1, 157.0, 153.8, 151.6, 136.5, 133.8, 128.5, 127.4, 124.1, 120.3, 118.3, 117.4, 101.1, 97.0, 90.3, 86.2, 84.0, 76.1, 75.6, 74.0, 65.8, 60.6, 59.4, 54.9, 53.0, 47.8, 25.9, 19.3, 18.4, 7.0, 6.9, 4.9, -4.0, -4.1. 183 FI1R (thin film), cm-1: 3448 (m, OH), 2955 (s), 1821 (s, carbonate C=O), 1723 (s, ester C=O), 1620 (s), 1409 (s), 1260 (s), 1081 (s), 865 (s). 1LC (50% EtOAc in Hexanes), Rf. 88: 0.29 (fluoresces under UV, anisaldehyde) 89: 0.69 (fluoresces under UV, anisaldehyde) 184 .-... .-... _OH HO- '-"" '-"" i. NaH, THF, 23 "C ii. 2-nitrobenzyl bromide, THF, O°C 71% 90 1-(2-NitrobenzyD-1,4-butanediol C9 Q) Sodium hydride (222 mg of a 60% dispersion in mineral oil, 5.55 mmol, 1 equiv) was added to a flame dried 25 mL flask under argon atmosphere. The solid was washed with dry hexanes (3 1-mL portions), and THF (11 mL) was introduced into the flask. 1,4Butanediol (490 µL, 5.55 mmol, 1 equiv) was added dropwise via syringe to the suspension, and gas evolution was observed. After 1 h of stirring at 23 °C, the yellow suspension was cooled to O CC and a solution of 2-nitrobenzyl bromide (1.20 g, 5.55 mmol, 1 equiv) in THF (1 mL) was added dropwise via cannula over 2 min. The resultant yellow suspension was maintained at O CC for 7 h, and excess sodium hydride was quenched by the addition of water (10 mL). The reaction mixture was extracted with ethyl acetate (3 25-mL portions). The combined organics were washed with saturated aqueous sodium chloride (25 mL), dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (50% ethyl acetate in hexanes) to provide the alcohol 90 (883 mg, 71 %) as a pale yellow oil. 185 8.03 (d, lH, J = 8.3 Hz, C3' H), 7.75 (d, lH, J =7.8 Hz, C4' H), 7.63 (t, lH, J = 6.1 Hz, C6' H), 7.42 (t, lH, J = 7.33 Hz, C5' H), 4.86 (s, 2H, o-NO 2C 6H4CH 2O), 3.67 (t, 2H, J =6.1 Hz, Cl H), 3.60 (t, 2H, J = 6.1 Hz, C4 H), 2.09 (br s, lH OH), 1.70 (m, 4 H, C2, C3 H) FTIR (thin film), cm· 1: 3386 (m, OH), 2942 (m), 2869 (m), 1523 (s, N-O), 1341 (s, N-O), 1109 (m), 1067 (m), 858 (w). 1LC (50% EtOAc in Hexanes), Rf. 2-nitrobenzyl bromide: 0.65 (UV, anisaldehyde) 90: 0.33 (UV, anisaldehyde) 186 02NY'.) 0 2N ~ PDC, DMF, 23 °c HO~O~ 87% 90 HO~O~s1 91 Acid91 Pyridinium dichromate (3.34 g, 8.92 mmol, 10 equiv) was added in one portion to a solution of alcohol 90 (200 mg, 0.892 mmol, 1 equiv) in N,N-dimethylformamide (5 mL) at 23 °C. The reaction mixture was kept in the dark at 23 °C for 15 h, and diluted with water (50 mL). The reaction mixture was acidified to pH 3 with 10% aqueous hydrochloric acid (10 mL) and extracted with diethyl ether (3 20-mL portions). The combined organics were washed with saturated aqueous sodium chloride (30 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (10% methanol in dichloromethane) afforded acid 91 (186 mg, 87%) as a pale yellow oil that solidified upon standing. 8.05 (d, lH, J = 8.2 Hz, C3' H), 7.75 (d, lH, J =1.6 Hz, C6' H), 7.64 (t, lH, J = 7.3 Hz, C5' H), 7.42 (t, lH, J =1.6 Hz, C4' H), 4.86 (s, 2H, o- NO 2C6H4CH 2O), 3.63 (t, 2H, J = 6.1 Hz, Cl H), 2.50 (t, 2H, J = 7.2 Hz, C3 H), 2.02 (m, 2 H, C2 H). 187 FTIR (thin film), cm-1: 3083 (m, OH), 2939 (m), 2872 (m), 1707 (s, C=O), 1525 (s, N-O), 1342 (s, N-0), 1112 (m), 729 (w). 90: 0.43 (UV, anisaldehyde) 91: 0.32 (UV, anisaldehyde) 188 0 o=( 11 11 91, CH 3 PPh 2, DEAD, CsHs, 5°C 27% Mitsunobu di ester 92 b A flame-dried 10-mL Schlenk flask under an argon atmosphere was charged with 1.5 mL of a 10 mg/mL stock solution in benzene containing the alcohol 89 (15 mg, 2.0 x 10·2 mmol, 1 equiv). The solvent was removed in vacuo, and 1.13 mL freshly distilled benzene was added. Acid 91 (72 mg, 0.30 mmol, 15 equiv) was added in one portion, and the resultant pale yellow solution was cooled to 5 °C in an ice/water bath. Methyl diphenylpholsphine (56 µL, 60 mg, 0.30 mmol, 15 equiv) and a solution of diethyl azodicarboxylate (31 µL, 0.20 mmol, 15 equiv) in anhydrous benzene (375 µL) were added sequentially over 1 min via syringe to the cooled solution. The resultant orange solution was maintained at 5 °C for a period of 15 min. At this point, the reaction was judged to be complete by 1LC analysis. Determination of the HPLC yield of the reaction and preparatory purification of the product was accomplished as follows: A solution of 1,3,5-trimethoxybenzene in acetonitrile (200 µL of a 1.0 M solution, 0.20 mmol) was added to the crude reaction mixture as an internal standard, and the resultant solution was filtered through a small plug 189 of cotton in the tip of a Pasteur pipet. Two 1-mL benzene washings of the pipet were also made, bringing the final volume of the crude reaction solution to approximately 3.3 mL. For analytical HPLC: 10 µL of this solution was removed and placed in a half-dram vial. The solution was briefly concentrated to near dryness on a rotary evaporator, and quickly diluted with 100 µL acetonitrile. Injections of 100 µL were made onto the HPLC (Beckman ODS C18 semi-prep column (10 mm x 25 cm) with a solvent system comprising 65% 10 mM pH 5.5 sodium acetate/ 35% acetonitrile grading to 100% acetonitrile over 20 min at a flow rate of 2.0 mUmin, monitoring at 240 nm. Retention times: 1,3 ,5- trimethoxybenzene: 19 min; Mitsunobu product: 37 min.). The yield was based on the average of two injections, and was found to be 8.75 x 10· 3 mmol (44%). For preparatory HPLC: 600-900 µL of the stock solution was removed and added to a half-dram vial. The solution was concentrated to near dryness on a rotary evaporator and rapidly diluted with 500 µL acetonitrile. The entire sample was injected onto the HPLC (Vydac 201HS1022 C18 column (22 mm x 25 cm) and an isocratic solvent system comprising 14% 10 mM aqueous ammonium acetate (pH 5.5)/86% acetonitrile at a flow rate of 7.0 mUminute, monitoring at 240 nm. The retention time of the Mitsunobu product was approximately 30 minutes.). As the peak was eluting, collections were made in a test tube just outside of the detector on the HPLC. The acetonitrile/buffer solution was concentrated in vacuo to remove acetonitrile, and the concentrate was diluted with benzene and stored in the freezer until all injections were complete. Subsequent collections were handled identically and pooled with previous collections. After the final collection and pooling, the layers were separated, and the aqueous layer further extracted with benzene (2 0.5-mL portions). The combined organics were dried over sodium sulfate and were concentrated to a volume of ca. 0.1 mL. Quantitation of the isolated product was performed as described in the next paragraph. Following this protocol, the reaction product could be cleanly isolated in approximately 13 runs on the HPLC. 190 Quantitation of the isolated product was accomplished as follows: A 0.5 mL portion of deuteriated benzene (99.5 atom % D) was added to the concentrated benzene solution, and the resultant solution was concentrated to a volume of ca. 0.1 mL. This procedure was repeated 4 times. After the last iteration, the concentrated solution was taken up in approximately 0.4 mL deuteriated benzene (99.95 atom % D). tran.s- Dichloroethylene (5 µL of a 0.0648 M solution in deuteriated chloroform (5 µL dichloroethylene diluted to 1.0 mL)) was added as an internal standard. Analysis of 92b by 1H NMR and integration of the internal standard against the C8 proton provided the isolated yield of the product (5.39 x 10- 3 mmol, 27% ). 191 7.73 (d, lH, J = 8.40 Hz, N02C6H 4CH20), 7.60 (d, 2H J = 9.20 Hz, C3" and C4" H), 7.30-7.18 (lH, obscured, C8" H), 7.12 (t, lH J = 8.00 Hz, N0 2C6H 4CH 20), 7.02 (s, lH, C6" H), 6.91 (d, lH, J = 8.80 Hz, N0 2C6 H 4CH2 0), 6.77 (t, lH, J = 8.00 Hz, N0 2C6 H 4CH20), 6.33 (m, lH, Cll H), 6.31 (d, lH, J = 2.20 Hz, ClO H), 5.16 (s, lH, C8 H), 4.70 (s, 2H, 2- N02C6 H 4CH 2 0), 3.63 (s, 3H, C7'' OCH 3), 3.58 (dd, lH, J = 8.40, 6.00 Hz, C13 H), 3.42-3.36 (complex, 2H, C14 H), 3.31-3.22 (complex, 3H, C12 BH and 0 2CCH 2CH 2CH 20), 3.07 (dd, lH, J = 15.30, 4.00 Hz, C12 aH), 2.96 (s, lH, C5 H), 2.38 (td, 2H, J = 7 .20, 2.80 Hz, 0 2CCH 2CH 2CH 20), 2.32 (s, 3H, C5" CH 3), 1.89 (m, 2H, 0 2CCH2CH 2CH 20), 1.13 (s, 9H, OSiC(CH 3)iCH 3) 2), 1.07 (t, 9H, J = 8.00 Hz, OSi(CH 2CH 3) 3 ), 0.93 (m, 6H, OSi(CH 2CH 3) 3), OSiC(CH 3)iCH 3) 2), 0.30 (s, 3H, (s, 3H, 0.27 OSiC(CH 3MCH 3) 2). 89: 0.38 (fluoresces under UV, anisaldehyde) 92b: 0.54 (fluoresces under UV, anisaldeh yde) 192 (±)-CSA, 2:1 ,i 0 0 H3CO~OTBS lyll) CHa 92b 11. 0 H3C O w • __,• OTBS ~ CH3 I b 4• 93b Secondary alcohol 9 3b (±)-Camphorsulfonic acid (2.3 mg, 0.0098 mmol, 5 equiv) was added in one portion to a solution of the Mitsunobu diester 92b (0.0020 mmol, 1 equiv) in 2:1 acetonitrile/water (325 µL). The solution was held at 23 °C for 40 min, then extracted with 1:1 ethyl acetate/hexanes (3 5-mL portions). The combined organics were washed with saturated aqueous sodium chloride (5 mL), and were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (50% ethyl acetate in hexanes) was followed by pooling the fractions containing the alcohol and concentrating to approximately 100 µL. A 0.5 mL portion of deuteriated benzene (99 .5 atom % D) was added to the concentrated solution, and the resultant solution was concentrated to a volume of ca. 0.1 mL. This procedure was repeated 4 times. After the 193 last iteration, the concentrated solution was taken up in approximately 0.4 mL deuteriated benzene (99.95 atom % D). trans-Dichloroethylene (5 µL of a 0.0648 M solution in deuteriated chloroform (5 µL dichloroethylene diluted to 1.0 mL)) was added as an internal standard. Analysis of the sample by 1H NMR and integration of the internal standard against the C-8 proton provided the isolated yield of the 93b (1. 11 x 10·3 mmol, 57%). 194 = 8.40, 1.08 Hz, 2N0 C H CH 0), 7.57 (d, lH, J = 9.16 Hz, C4" H), 7.47 (d, lH, J = 7.72 Hz, N0 C H CH 0), 7.13 (d, lH, J = 2.20 Hz, C8" H), 7.08 (td, lH J = 7.68, 1.12 Hz, 7.65 (dd, lH, J 2 6 4 2 2 6 4 2 N02C6 H 4CH20), 7.00 (br s, lH, C6" H), 6.87 (d, lH, J = 8.80 Hz, C3" H), 6.74 (t, lH, J = 7.32 Hz, N02C 6 H 4CH20), 6.12 (d, lH, J = 1.84 Hz, ClO H), 6.11 (m, lH, Cll H), 4.18 (d, lH, J = 9.52 Hz, C8 H), 4.71 (abq, 2H, J = 14.64 Hz, /!iv = 35.52 Hz, 2N0 2C6 H4CH 20), 3.64 (m, lH, C13 H), 3.62 {s, 3H, C7'' OCH 3), 3.48 (d, lH, J = 9.52 Hz, OH), 3.26 (m, 2H, 0 2CCH 2CH 2CH 20), 3.23 (dd, 2H, J = 2.56, 1.84 Hz, C14 H), 3.00 (d, 2H, J = 5.48 Hz, C12 H), 2.91 (s, lH, C5 H), 2.30 (s, 3H, C5" CH 3), 2.12 {m, 2H, 0 2CCH2CH 2CH 20), 1.73 (m, 2H, 0 2CCH 2CH 2CH 20), 1.10 (s, 9H, OSiC(CH 3)/CH 3) 2), 0.27 (s, 3H, OSiC(CH 3)/CH 3) 2), 0.24 (s, 3H, OSiC(CH 3)/CH 3) 2). 195 TLC (50% EtOAc in Hexanes), Rf. 92b: 0.53 (fluoresces under UV, anisaldehyde) 93b: 0.22 (fluoresces under UV, anisaldehyde) 196 (CF3S0;?)2O, pyridine-d5 CD2Cl2, -78 °C ➔ -30°C Rearranged trifluoromethanesulfonate 9 4 or dioxolenium ion 9 5 A solution the alcohol 93b (1.9 x 10·3 mmol, 1 equiv) in CD 2Cl2 (99.95 atom% D, 400 µL) was placed in an NMR tube, which was sealed with a septum and cooled to -78 °C. Pyridine-d5 (3.0 µL, 3.2 mg, 3.8 x 10·2 mmol, 20 equiv) was added via syringe. The tube was tilted carefully to wash the pyridine into solution, and the reaction mixture was recooled to -78 °C. Trifluoromethanesulfonic anhydride (3.0 µL, 5.4 mg, 1.9 x 10·2 mmol, 10 equiv) was added to the cold reaction mixture via syringe. Keeping the solution as cold 197 as possible, the NMR tube was inserted quickly into the probe of a JEOL GX-400 spectrometer that had been pre-cooled to - 70 °C. After obtaining a spectrum of unreacted diester alcohol at -70 °C, the probe was warmed to -30 °C. After adjusting the shims, a new spectrum was obtained which indicated complete and clean conversion to a product corresponding to either trifluoromethanesulfonate 94 or dioxolenium ion 95. The probe was also warmed to O °C, and the spectrum obtained at this temperature was identical to that obtained at-30 °C. 198 8.40 Hz (d, lH, J = 9.12 Hz, C4" H), 8.00 (d, lH, J = 8.08 Hz, N02C6H 4CH20), 7.79 (s, lH, C8" H), 7.72 (d, lH, J = 7.68 Hz, N0 2C6H 4CH20), 7.67 (t, lH, J = 7.32 Hz, N0 2C6H 4CH20), 7.45 (t, lH, J = 7.32 Hz, N0 2C6H 4CH 20), 7.03 (s, lH, C6" H), 6.92 (d, lH, J = 9.16 Hz, C3" H), 6.85 (d, lH, J = 7.68 Hz, ClO H), 6.40 (app. q, lH, J = 7.68 Hz, Cl 1 H), 6.25 (s, lH, C8 H), 4.81 (s, 3H, N0 2C6 H4CH 20), 4.80 (dd, lH, J = 8.40, 5.48 Hz, C13 H), 4.60 (t, lH, J = 8.80 Hz, C14 H), 4.37 (dd, lH, J =9.16, 5.88 Hz, C14 H), 3.94 (s, 3H, CT' OCH 3), 3.93 (s, lH, C5 H), 3.55 (t, 2H, J =5.84 Hz, 0 2CCH2CH 2CH20), 3.47 (dd, lH, J = 15.00, 7.32 Hz, C12 ~H), 2.64 (s, 3H, C5" CH 3), 2.54 (dd, lH, J = 15.76, 6.24 Hz, C12 aH), 2.48 (t, 2H, J = 7.32 Hz, 0 2CCH2CH 2CH2 0), 1.91 (app. t, 2H, J = 6.20 Hz, 0 2CCH 2CH 2CH20), 1.01 (s, 9H, OSiC(CH 3)iCH 3) 2), 0.41 (s, 6H, OSiC(CH 3)iCH 3) 2). 1LC (50% EtOAc in Hexanes), Rf 93b: 0.21 (fluoresces under UV, anisaldehyde) 94 or 95: 0.37 (fluoresces under UV, anisaldeh yde) 199 CICH2C02H, PPh3, DEAD, C6H6 , 23 °C II i HO,,.. H H3CXO H3C H + O''' 11 CIH2CC02 12 12 lBSO.: lBSO.: 97 2:3 ratio 14 i1 H CH(OCH3), 98 Esters 97 and 98 Diethyl azodicarboxylate (237 mL, 1.50 mmol, 10 equiv) was added dropwise via syringe over 3 min to a solution of alcohol 65 (72 mg, 0.15 mmol, 1 equiv), triphenylphosphine (395 mg, 1.50 mmol, 10 equiv), and chloroacetic acid (142 mg, 1.50 mmol, 10 equiv) in benzene (8 mL) at 23 °C. The orange reaction mixture was stirred at 23 °C for 10 h, then volatiles were removed in vacuo. The residue was purified by flash column chromatography (10% ethyl acetate in hexanes grading to 30% ethyl acetate in hexanes) to provide an inseparable mixture of esters 97 and 98 as well as a small amount of the chloroacetic acid-diethyl azodicarboxylate adduct. The yield was not determined at this point, but the mixture of esters was instead carried directly to the next step. 200 For 97: 1 H NMR (400 MHz, C6DJ, o: 6.18 (s, lH, ClO H), 5.30 (s, lH, C8 H), (Diagnostic peaks only) 4.27 (m, lH, Cl 1 H), 4.08 (dd, lH, J = 8. 79, 5.68 Hz, C13 H), 2.83 (dd, lH, J = 16.36, 6.11 Hz, C12 ~H), 2.44 (dd, lH, J = 16.36, 2.44 Hz, C12 aH), 1.98 (d, lH, J = 1.71 Hz, C7 H), 1.41 (s, 3H, C(CH C(CH 3 ) 2 ), ) 3 1.21 (s, 3H, ), 2 0.94 (s, 9H, OSiC(CH )/CH 3 0.15 (s, 3H, OSiC(CH )/CH 3 3H, OSiC(CH )iCH 3 3 ) 2 ). 65: 0.29 (UV, anisaldehyde) 97: 0.68 (UV, anisaldehyde) 3 ) 2 ), ) 3 ), 2 0.06 (s, 201 For 98: 1 H NMR (400 MHz, C6DJ, 6: 6.53 (s, lH, CIO H), 5.55 (s, lH, C8 H), (Diagnostic peaks only) 4.99 (m, lH, Cl 1 H), 4.17 (dd, lH, J = 9.04, 5.86 Hz, C13 H), 3.93 (dd, lH, J = 8.79, 6.84 Hz, C14 H), 3.09 (dd, lH, J = 14.65, 6.35 Hz, C12 ~H), 2.72 (dd, lH, J = 14.65, 4.39 Hz, C12 aH), 2.13 (d, lH, l= 1.71 Hz, C7 H), 1.44 (s, 3H, C(CH 3) 2 ), 1.18 (s, 3H, C(CH ) 3 ), 2 0.92 (s, 9H, OSiC(CH )iCH 3 0.00 (s, 3H, OSiC(CH )iCH 3 3H, OSiC(CH 3)iCH 3) 2). 65: 0.29 (UV, anisaldehyde) 98: 0.68 (UV, anisaldehyde) ) 3 ), 2 ) 3 ), 2 -0.01 (s, 202 H3C,, 0 H3CXO H3Cxo••· H3C 11 t H + K.!C03, CH30H, O °C H CH(OCH 3)2 CIH 2CC0 2 80% (two steps) -: 0 2CCH 2CI 97 t 11 CH(OCH3)2 TBSO.:' 0''' TBSO 98 2:3 ratio H3CXO HaC H3C,XO 0 5 11 12 t1 H3C .. H CH(OCH 3h + ~7 H CH(OCH 3). TBSO-: OH 99 11 12 -:· TBSO O'' 2:3 ratio 100 Alcohols 99 and 10 0 Potassium carbonate (10 mg) was added in one portion to a 0 °C solution of esters 97 and 98 (19 mg, 0.034 mmol, 1 equiv) in methanol (1 mL). After maintaining the solution at 0 °C for 10 min, the reaction mixture was partitioned between 1: 1 ethyl acetate/hexanes (2 mL) and pH 7.2 phosphate buffer (2 mL). The layers were separated and the aqueous layer was further extracted with 1: 1 ethyl acetate/hexanes (2 2-mL portions). The combined organics were washed with saturated aqueous sodium chloride (5 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash 203 column chromatography (20% ethyl acetate in hexanes) afforded inseparable alcohols 99 and 100 (13 mg combined, 80%) as an approximately 2:3 mixture. For alcohol 99: 1 H NMR (400 MHz, C6DJ, 8: 6.21 (t, lH, J = 1.47 Hz, ClO H), 5.48 (s, (Diagnostic peaks only) lH, C8 H), 5.11 (m, lH, Cll H), 2.96 (dd, lH, J = 13.92, 6.89 Hz, C12 PH), 2.57 (dd, lH, J = 13.56, 5.13 Hz, C12 aH), 1.44 (s, 3H, C(CH 3) 2), 1.19 (s, 3H, C(CH 3 ) 2 ), 0.93 (s, 9H, OSiC(CH 3) 3(CH 3) 2), 0.01 (s, 3H, OSiC(CH 3) 3(CH 3) 2), 0.00 (s, OSiC(CH 3)iCH 3) 2). 97 and 98: 0.80 (UV, anisaldehyde) 99: 0.60 (UV, anisaldehyde) 3H, 204 For alcohol 100: 1 H NMR (400 MHz, C6D6), 3: 5.34 (s, lH, C8 H), 5.07 (s, lH, ClO H), (Diagnostic peaks only) 4.44 (m, lH, Cl 1 H), 2.90 (dd, lH, J = 16.49, 5.50 Hz, C12 ~H), 2.52 (dd, lH, J = 16.48, 4.03 Hz, C12 o:H), 1.40 (s, 3H, C(CH 3)2), 1.21 (s, 3H, C(CH 3)2), 1.00 (s, 9H, OSiC(CH 3)iCH 3) 2), OSiC(CH 3)iCH 3) 2), 0.19 0.13 (s, (s, OSiC(CH 3)iCH 3) 2). TLC (10% EtOAc in C8iC1i), Rf. 97 and 98: 0.80 (UV, anisaldehyde) 100: 0.60 (UV, anisaldehyde) 3H, 3H, 205 H3~ 0 H3CXO H3C H3C 0'.. i 11 o••· TIPSOTf, 2,6-lutidine, 11 i + H CH(OCH3)2 .::· TBSO H CH(OCH 3)2 .::· OH TBSO 99 H3q, CH 2Cl2, -78 °C 100 2:3 ratio 0 H3CXO H3CXO H3C 5 11 i7 H3CXO 0 + H 11 i7 + H CH(OCH3)2 TBSO.:: 0'' H3C 11 OCH 3 TBSO.:: OTIPS H CH(OCH3)2 .:: TBSO OTIPS 101 102 100 (55% of theory) (37% of theory) (100% of theory) Triisopropylsilyl ethers t Qt and t Q2 2,6-Lutidine (24 µL, 0.21 mmol, 20 equiv) and triisopropylsilyl trifluoromethanesulfonate (28 µL, 0.10 mmol, 10 equiv) were added sequentially via syringe to a solution of alcohols 99 and 100 (13 mg of the mixture, assume 5 mg 99, 0.010 mmol, 1 equiv) in dichloromethane (1 mL) at -78 °C. After 15 min at -78 °C, the solution was warmed to 0 °C. After 3.5 h at 0 °C, excess triisopropylsilyl trifluoromethanesulfonate was quenched by addition of triethylamine (0.5 mL) and methanol (0.5 mL). The resultant solution was warmed to 23 °C and partitioned between 206 1:1 ethyl acetate/hexanes (2 mL) and pH 7.2 phosphate buffer (2 mL). The layers were separated and the aqueous layer was further extracted with 1: 1 ethyl acetate/hexanes (2 2mL portions). The combined organics were washed with saturated aqueous sodium chloride (3 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (hexanes grading to 20% ethyl acetate in hexanes) afforded dimethyl acetal 101 (6.6 mg, 55%) as a colorless oil, methyl enol ether 102 (6.2 mg, 37%) as a colorless oil, and recovered alcohol 100 (8.3 mg, 100% recovery) as a colorless oil. For 101: 5.45 (s, lH, C8 H), 5.07 (s, lH, Cl0 H), 4.29 (m, lH, Cl 1 H), 4.15 (dd, lH, J = 8.55, 6.11 Hz, C13 H), 3.93 (dd, lH, J = 8.55, 6.84 Hz, C14 H), 3.77 (t, lH, J = 6.35 Hz, C14 H), 3.54 (d, lH, J = 1.71 Hz, C5 H), 3.34 (s, 3H, CH(OCH 3)2), 3.33 (s, 3H, CH(OCH 3)2), 2.82-2.62 (obscured, lH, C12 ~H), 2.42 (br d, lH, J = 15.87 Hz, C12 aH), 2.00 (d, lH, J = 1.46 Hz, C7 H), 1.48-0.95 (complex, 21H, OSi(CH(CH 3}i\), 0.91 (s, 9H, OSiC(CH 3)iCH 3)2), OSiC(CH 3\(CH 3)2), OSi C( CH 3)iCH3)2) · 0.05 0.12 (s, (s, 3H, 3H, 207 99 and 100: 0.13 (UV, anisaldehyde) 101: 0.56 (UV, anisaldehyde) For 102: 6.66 (d, lH, J = 0.74 Hz, C12 H), 6.14 (d, lH, J =2.19 Hz, ClO H), 5.21 (s, lH, C8 H), 4.90 (d, lH, J = 2.45 Hz, C11 H), 4.05 (dd, lH, J = 8.79, 5.61 Hz, C13 H), 3.79 (dd, lH, J = 8.79, 6.83 Hz, C14 H), 3.62 (t, lH, J = 5.62 Hz, C14 H), 3.44 (d, lH, J = 1.71 Hz, C5 H), 3.13 (s, 3H, CHOCH 3), 1.95 (d, lH, J = 1.70 Hz, C7 H), 1.45-1.16 (complex, 21H, OSi(CH(CH 3) 2) 3), 0.96 (s, 9H, OSiC(CH 3) 3 (CH 3) 2), 0.17 (s, 3H, OSiC(CH 3)iCH 3) 2), 0.08 (s, 3H, OSiC(CH 3)iCH 3) 2). 99 and 100: 0.13 (UV, anisaldehyde) 102: 0.67 (UV, anisaldehyde) 208 i H II i II p-TsOH, acetone,23 °c CHO 61% TBSO~ OTIPS 102 7 H TBSO~ OTIPS 103 Aldehyde 1 Q3 fr Toluenesulfonic acid (1 mg) was added in one portion to a solution of dimethyl acetal 101 (3.0 mg, 4.72 x 10·3 mmol, 1 equiv) in acetone (0.5 mL) at 23 °C. The resultant pale yellow solution was maintained at 23 °C for 45 min, and was partitioned between saturated aqueous sodium bicarbonate (2 mL) and hexanes (2 mL). The layers were separated and the aqueous layer was further extracted with hexanes (2 2-mL portions). The combined organic extracts were dried over sodium sulfate and concentrated. The crude aldehyde 103 (1.7 mg, 61 %) was examined by 1H NMR and judged to be sufficiently pure to proceed without further purification. 209 10.43 (s, lH, C8 H), 5.28 (s, lH, ClO H), 4.31 (d, lH, J = 4.76 Hz, Cll H), 3.89 (dd, lH, J = 8.79, 5.50 Hz, C13 H), 3.69 (dd, lH, J = 8.79, 6.97 Hz, C14 H), 3.52 (t, lH, J = 6.59 Hz, C14 H), 3.33 (d, lH, J = 1.46 Hz, C5 H), 3.07 (dd, lH, J = 17.96, 5.13 Hz, C12 BH), 2.45 (d, lH, J = 18.31 Hz, C12 cxH), 1.88 (d, lH J = 1.83 Hz, C7 H), 1.60-1.11 (complex, 21H, OSi(CH(CH 3) 2) 3), 0.91 (s, 9H, OSiC(CH 3)/CH 3) 2), OSiC(CH 3)/CH 3) 2), 0.09 0.02 OSiC(CH 3)/CH 3) 2). 101: 0.25 (UV, anisaldehyde) 103: 0.37 (UV, anisaldehyde) (s, (s, 3H, 3H, 210 b TBSO 0 i. A'lSeTMS, TMSOTf, CH 20 2 , -78 "C ii. HC(OCHah, -25 ➔ -20 °c iii. H2')2, Py, -20 "C P"CH(OCH,), TBSO (-)-33 (-)-21 73% Enone C-}-21 Trimethylsilyl phenylselenide (4.76 mL, 28.3 mmol, 1.5 equiv) was added dropwise over 4 min to a solution of enone (-F33 (4.0 g, 19 mmol, 1.0 equiv) in dichloromethane (80 mL) at -78 °C. This was followed by dropwise addition of trimethylsilyl trifluoromethanesulfonate (1.11 mL, 5.65 mmol, 0.30 equiv). The resultant yellow solution was stirred at -78 °C for 10 min, and warmed to -20 °C for an additional hour. Freshly distilled trimethyl orthofonnate (8.24 mL, 75.4 mmol, 4.0 equiv) was added dropwise via syringe over a 5 min period. The slightly darker yellow solution was maintained at -20 °C for an additional 20 min, and pyridine (2.4 mL) and 30% hydrogen peroxide (11.4 mL) were added sequentially through the top of the flask. The reaction mixture was kept at -20 °C for 15 min, during which time the yellow color faded to a pale yellow. After warming to 23 °C, the reaction mixture was diluted with 1: 1 ethyl acetate/hexanes (200 mL). The layers were separated, and the organic layer was washed with water (100 mL) and saturated aqueous sodium chloride (100 mL), then was dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (10% ethyl acetate in hexanes grading to 15% ethyl acetate in hexanes) to provide enone (-)-21 (3.9 g, 73%) as a pale yellow oil. 211 7.41 (s, lH, vinylic H), 5.10 (s, lH, CH(OCH 3) 2 , 4.92 (m, lH, CHOTBS), 3.32 (s, 6H, CH(OCH 3) 2 ), 2.78 (dd, lH, J = 18.2, 5.5 Hz, methylene PH), 2.32 (dd, lH, J = 18.2, 1 Hz, methylene aH), 0.90 (s, 9H, OSiC(CH 3)iCH 3) 2 ), 0.12 (s, 3H, OSiC(CH 3)iCH 3) 2), 0.10 (s, 3H, OSiC(CH 3)iCH 3) 2). FfIR (thin film), cm- 1: 2953 (m), 2930 (m), 2856 (m), 1718 (s, C=O), 1059 (m). 1LC (20% EtOAc in Hexanes), Rf: (-)-33: 0.39 (UV, anisaldehyde) (-)-21: 0.30 (UV, anisaldehyde) 212 0 OCH 3 H3C O ~ O H ~ CH 3 96% 45 107 o Naphthoate ester 1 7 Diisopropylethylamine (7 .06 mL, 40.6 mmol, 20 equiv) and MEM chloride (2.32 mL, 20.3 mmol, 10 equiv) were added sequentially via syringe to a solution of naphthoate ester 45 (1.00 g, 4.06 mmol, 1 equiv) in dichloromethane (100 mL) at 0 0 C. The resultant yellow solution was maintained at 0 °C for 2 h, and partitioned between 1: 1 ethyl acetate/hexanes (100 mL) and water (100 mL). The layers were separated and the aqueous layer was further extracted with ethyl acetate (2 30-mL portions). The combined organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (25% ethyl acetate in hexanes grading to 30% ethyl acetate in hexanes) afforded naphthoate ester 107 (1.33 g, 98%) as a colorless oil. 213 7.68 (d, lH, J = 9.26 Hz, C4 H), 7.32 (d, lH, J = 9.26 Hz, C3 H), 7.27 (s, lH, C8 H), 7.00 (s, lH, C6 H), 5.16 (s, 2H, OCH2OCH 2CH20CH3), 3.81 (s, 3H, CO2CH 3), 3.73 (t, 2H, J = 5.89 Hz, OCH 2OCH2CH20CH3), 3.46 (s, 3H, C7 OCH 3), 3.31 (t, 2H, OCH2OCH2CH2OCH 3, J = 5.89 3.07 (s, Hz, 3H, OCH 2OCH2 CH 2OCH 3, 2.28 (s, 3H, C5 CH 3). 168.7, 159.2, 153.4, 136.6, 133.6, 127.5, 124.7, 119.7, 118.6, 113.4, 101.3, 94.4, 71.9, 68.3, 58.5, 54.6, 51.9, 19.2. FTIR (thin film), cm- 1: 2916 (s), 1725 (m, C=O), 1619 (m), 1028 (m). TLC (20% EtOAc in Hexanes), Rf 45: 0.38 (fluoresces under UV, anisaldehyde) 107: 0.09 (fluoresces under UV, anisaldehyde) 214 0 OCH 3 H3C O ~ O M E M ~ CH 3 107 Acid 108 Sodium hydroxide (11.9 g, 298 mmol, 75 equiv) was added in portions over a 5 min period to a solution of the naphthoate ester 107 (1.33 g, 3.98 mmol, 1 equiv) in 1:1 methanol/water (40 mL). The resultant solution was heated to 80 °C for 20 hand cooled to 23 °C. The reaction mixture was acidified to pH 3 with lN hydrochloric acid (400 mL) and extracted with ethyl acetate (3 100-mL portions). The combined organic extracts were washed with saturated aqueous sodium chloride (100 mL), dried over sodium sulfate and concentrated. The crude acid 108 (1.14 g, 90%) solidified from a pink oil to a pink solid, and was used without further purification. 215 9.50 (br s, lH, C02H), 7.62 (d, lH, J = 8.73 Hz, C4 H), 7.62 (s, lH, C8 H), 7.18 (d, lH, J = 9.42 Hz, C3 H), 6.95 (m, lH, C6 H), 5.07 (s, 2H, OCH2OCH2CH2 0CH3), 3.61 (dd, 2H, J = 6.10, 4.50 Hz, OCH 2OCH2CH20CH3), 3.44 (s, 3H, C7 OCH 3), 3.16 (dd, 2H, J = 4.71, 3.18 Hz, OCH 2OCH2CH 2OCH 3), 2.92 (s, 3H, OCH 2OCH 2CH 2OCH 3), 2.25 (s, 3H, C5 OCH 3). 1LC (50% EtOAc in Hexanes), Rf. 107: 0.47 (fluoresces under UV, anisaldehyde) 108: 0.00 (fluoresces under UV, anisaldehyde) 216 II ii. (-)-21 i1 TBS 54% 12 TBSO 109 Alcohol 1Q9 Lithium hexamethyldisilazide (3.25 mL of a 1.0 M solution in hexanes, 3.25 mmol, 1.05 equiv) was added dropwise over 4 min to a -78 °C solution of epoxy diyne 20 (996 mg, 3.25 mmol, 1.05 equiv) in toluene (23 mL). The resultant pale yellow solution was stirred at -78 °C for 30 min, then a solution of enone (-)-21 (887 mg, 3.10 mmol, 1.0 equiv) in toluene (10 mL) was added dropwise via cannula over 10 min. The transfer was quantitated with toluene (2 x 3 mL). The reaction mixture was maintained at -78 °C for an additional 15 min, then excess lithium hexamethyldisilazide was quenched by the addition of saturated aqueous ammonium chloride (30 mL). The mixture was warmed to 23 °C and partitioned between 1:1 ethyl acetate in hexanes (50 mL) and water (50 mL). The layers were separated and the aqueous layer was further extracted with 1: 1 ethyl acetate/hexanes (2 50-mL portions). The combined organic extracts were washed with saturated aqueous sodium chloride (50 mL), dried over sodium sulfate and concentrated. Purification of the residue was accomplished by flash column chromatography (10% ethyl acetate in hexanes) to afford alcohol 109 (1.0 g, 54%) as a pale yellow oil. 217 6.18 (s, lH, ClO H), 5.45 (s, lH, C8 H), 4.88 (m, lH, Cll H), 4.08 (dd, lH, J = 8.79, 5.86 Hz, C13 H), 3.89 (s, lH, OH), 3.84 (dd, lH, J = 8.55, 6.83 Hz, C14 H), 3.58 (t, lH, J = 5.86 Hz, C14 H), 3.46 (s, lH, C5 H), 3.21 (s, 3H, CH(OCH 3 )i), 3.17 (s, 3H, CH(OCH 3 ) 2 ), 3.21-3.14 (obscured, lH, C12 ~H), 2.50 (dd, lH, J = 13.43, 5.37 Hz, C12 aH), 1.43 (s, 3H, C(CH 3 ) 2 ), 1.18 (s, 3H, C(CH 3 ) 2 ), 1.04 (s, 9H, SiC(CH 3 )iCH 3 ) 2 ), 0.95 (s, 9H, SiC(CH 3)iCH 3) 2 ), 0.19 (s, 6H, SiC(CH 3 )iCH 3 ) 2 ), 0.08 (s, 3H, SiC(CH 3 )iCH 3 ) 2 ), 0.06 (s, 3H, SiC(CH 3 )iCH 3 ) 2 ). FTIR (thin film), cm- 1: 3509 (m, OH), 2953 (s), 2931 (s), 2888 (s), 2857 (s), 2182 (w, C=C), 1464 (m), 1361 (m), 1254 (s), 1213 (m), 1109 (s). 1LC (20% EtOAc in Hexanes), Rf. (-)-21: 0.38 (UV, anisaldehyde) 109: 0.19 (anisaldehyde) 218 H3C,, 0 H3CXO H3CXO''' H3C II ~ TBS CH(OCH3)2 s 0 Bu4 NF, THF, o ° C 99% TBSO 11 12 H CH(OCH 3 h HO 109 110 Diol 110 Tetrabutylammonium fluoride (709 µL of a 1.0 M solution in THF, 0.709 mmol, 3 equiv) was added dropwise via syringe to a solution of alcohol 109 (140 mg, 0.236 mmol, 1 equiv) in THF (5 mL) at 0 °C. The resultant deep purple solution was maintained at 0 CC for 20 min, and poured into water (35 mL). The mixture was extracted with ethyl acetate (4 15-mL portions). The combined extracts were washed with saturated aqueous sodium chloride (30 mL), dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (50% ethyl acetate in hexanes grading to 100% ethyl acetate) to afford diol 110 (90 mg, 99%) as a pale yellow oil. . 219 6.06 (hrs, lH, ClO H), 5.38 (t, lH, J = 1.71 Hz, C8 H), 4.49 (hr s, lH, C 11 H), 4.09 (dd, lH, J = 8.78, 5.85 Hz, C13 H), 3.83 (dd, lH, J = 8.55, 6_59 Hz, C14 H), 3.62 (t, lH, J = 6.35 Hz, C14 H), 3.40 (d, lH, J = 1.71 Hz, CS H), 3.18 (s, 3H, CH(OCH 3) 2), 3.17 (s, 3H, CH(OCH 3)2), 2.87 (dd, lH, J = 13.92, 7.08 Hz, C12 aH), 2.31 (dd, lH, J = 13.67, 3.90 Hz, C12 ~H), 1.98 (d, lH, J = 1.71 Hz, C7 H), 1.41 (s, 3H, C(CH 3)2), 1.19 (s, 3H, C(CH 3) 2 ). FTIR (thin film), cm- 1: 3418 (s, OH), 3260 (s, C=C-H), 2931 (s), 2131 (w, C=C), 1108 (m), 1070 (s). 1LC (20% EtOAc in Hexanes), Rf 109: 0.19 (anisaldehyde) 110: 0.00 (anisaldehyde) 1LC (50% EtOAc in Hexanes), Rf: 110: 0.10 (anisaldehyde) 220 H3YO H3C,,,. H3C H3 C 0''' II t H s • II 108, PPh:J, DEAD, C6 f-ls, 23 "C CH(OCH3)2 H CH(OCH 3). 12 70% d HO 110 t1 o ~ H 3 C O w r r OMEM ~ I b CH3 4' 111 Ester 111 Diethyl azodicarboxylate (40 mL, 0.26 mmol, 1.2 equiv) was added dropwise via syringe over 2 min to a solution of diol 110 (65 mg, 0.21 mmol, 1 equiv), triphenylphosphine (67 mg, 0.26 mmol, 1.2 equiv), and acid 108 (82 mg, 0.26 mmol, 1.2 equiv) in benzene (5 mL) at 23 °C. The resultant yellow solution was stirred for 15 min, and volatiles were removed in vacuo. The residue was purified by flash column chromatography (25% ethyl acetate in hexanes grading to 100% ethyl acetate) to provide ester 111 (99 mg, 70%) as a viscous, colorless oil. 221 7.67 (d, lH, J = 9.28 Hz, C4" H), 7.29 (d, lH, J = 9.28 Hz, C3" H), 7 .28 (m, lH, C8" H), 7.00 (m, lH, C6" H), 6.49 (d, lH, J = 1.47 Hz, ClO H), 6.45 (m, lH, Cl 1 H), 5.47 (s, lH, C8 H), 5.21 (s, 2H, OCH 2OCH 2CH2OCH 3), 3.97-3.91 (complex, 2H, C13, C14 H), 3.79 (m, 2H, OCH 2OCH2CH2OCH3), 3.72 (m, lH, C14 H), 3.57 (s, 3H, C7" OCH 3), 3.37 (m, 2H, OCH2OCH2CH 2OCH3), 3.19-3.12 (obscured, lH, C12 PH), 3.14 (s, 3H, CH(OCH 3) 2), 3.13 (s, 3H, OCH2OCH2CH 2OCH3), 3.12 (s, 3H, CH(OCH 3)i), 3.04 (s, lH, C5 H), 2.92 (dd, lH, J = 14.40, 3.90 Hz, C12 aH), 2.29 (s, 3H, C5" CH 3), 1.97 (d, lH, J = 1.71 Hz, C7 H), 1.34 (s, 3H, C(CH 3) 2 ), 1.12 (s, 3H, C(CH 3) 2 ). FTIR (thin film), cm· 1: 3483 (m, OH), 3278 (w, C=C-H), 2936 (s), 1724 (s, C=O), 1622 (s), 1466 (m), 1157 (s), 1099 (s). TLC (50% EtOAc in Hexanes), Rf. 110: 0.10 (anisaldehyde) 111: 0.21 (fluoresces under UV, anisaldeh yde) 222 H3CXO H3C II~ H 0 1'' II ~7 H CHO p-TsOH, acetone, 23 °c 12 0 w ~ 0 0 H3C O ~ O M E M CH3 0 ~ H 3 C O w r r OMEM ::::,.... 111 I ll 4" CH3 112 Aldehyde 11 2 p-Toluenesulfonic acid (140 mg) was added to a solution of dimethyl acetal 111 (522 mg, 0.842 mmol) in acetone (25 mL) at 23 °C. The resultant pale yellow solution was stirred for 40 min and poured into saturated sodium bicarbonate (25 mL). The mixture was extracted with 1:1 ethyl acetate/hexanes (3 25-mL portions). The combined organic extracts were washed with saturated aqueous sodium chloride (50 mL), and were dried over sodium sulfate and concentrated. The crude aldehyde 112 was carried directly to the next reaction without further purification. 223 9.36 (s, IH, C8 H), 7.67 (d, IH, J = 9.27 Hz, C4" H), 7.31 (d, IH, J = 9.28 Hz, C3" H), 7.22 (d, IH, J = 2.20 Hz, C8" H), 7.00 (s, IH, C6" H), 6.50 (d, IH, J = 2.44 Hz, CIO H), 6.16 (m, IH, C11 H), 5.25 (s, 2H, OCH 2OCH2CH2OCH3), 3.95 (dd, IH, J = 8.54, 6.10 Hz, C13 H), 3.80 (t, 2H, J = 4.88 Hz, OCH 2OCH 2CH2OCH 3), 3.76 (dd, IH, J = 8.78, 6.83 Hz, C14 H), 3.60 (t, IH, J = 6.35 Hz, C14 H), 3.57 (s, 3H, C7" OCH 3), 3.37 (m, 3H, C12 H, OCH 2OCH 2CH2OCH 3), 3.13 (s, 3H, OCH2OCH 2CH 2OCH 3), 2.89-2.85 (complex, 2H, C12 H, C5 H), 2.28 (s, 3H, C5" CH 3), 1.95 (d, lH, J = 1.46 Hz, C7 H), 1.33 (s, 3H, C(CH 3)2), 1.12 (s, 3H, C(CH 3) 2 ). 3463 (m, OH), 3282 (m, C=C-H), 2932 (m), 2131 (w, C=C), 1728 (s, ester C=O), 1693 (s, aldehyde C=O), 1622 (s), 1514 (m), 1411 (m), 1334 (m), 1257(s). TLC (30% EtOAc in Hexanes), Rf 111: 0.26 (fluoresces under UV, anisaldehyde) 112: 0.17 (fluoresces under UV, anisaldeh yde) 224 II~ H TMSOTf, 2,6-luticine, H CHO CH2a 2 , -78 °C CHO 12 ,.: no;. (two step) H,CO~OMEM yV CH3 112 0 0 H3COW8' '-:::: OMEM ~ I ~ 4' CH3 113 Trimethylsilyl ether 11 3 A flame-dried 50-mL round bottom flask was charged with aldehyde 112 (crude residue from previous reaction, assume 0.842 mmol, 1 equiv) and dichloromethane (21 mL). The solution was cooled to -78 °C, and 2,6-lutidine (981 µL, 8.42 mmol, 10 equiv) and trimethylsilyl trifluoromethanesulfonate (814 µL, 4.21 mmol, 5 equiv) were added sequentially via syringe. The solution was maintained at -78 °C for 20 min, and excess trimethylsilyl trifluoromethanesulfonate was quenched by the addition of triethylamine (1 mL) and methanol (1 mL). The reaction mixture was warmed to 23 °C and partitioned between 1:1 ethyl acetate/hexanes (50 mL) and water (50 mL). The layers were separated and the aqueous layer was further extracted with 1:1 ethyl acetate/hexanes (2 50-mL portions). The combined extracts were washed with saturated aqueous sodium chloride (50 mL), dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (10% ethyl acetate in dichloromethane) to afford trimethylsilyl ether 113 (318 mg, 77% two-step yield) as a colorless oil. 225 9.38 (s, lH, C8 H), 7.67 (d, lH, J = 9.28 Hz, C4" H), 7.30 (d, lH, J = 9.28 Hz, C3" H), 7.25 (d, lH, J = 2.20 Hz, C8" H), 7.00 (br s, lH, C6" H), 6.60 (d, lH, J = 2.19 Hz, ClO H), 6.35 (m, lH, Cll H), 5.22 (s, 2H, OCH2OCH2CH20CH 3), 4.02 (d , lH, J = 8.79, 6.11 Hz, C13 H), 3.88 (dd, lH, J = 8.79, 6.83 Hz, C14 H), 3.78 (dd, 2H, J = 6.10, 4.64 Hz, OCH2OCH 2CH 2OCH 3), 3. 72 (t, lH, J = 6.35 Hz, C14 H), 3.56 (s, 3H, CT' (m, 3H, C5 H, OCH 2OCH 2CH20CH3), 3.12 (s, 3H, OCH 3), 3.36 OCH 2OCH 2CH2OCH3), 3.01 (dd, lH, J = 14.16, 7.08 Hz, C12 ~H), 2.87 (dd, lH, J = 14.16, 4.88 Hz, C12 aH), 2.27 (s, 3H, C5" CH 3), 2.01 (d, lH, J = 1.71 Hz, C7 H), 1.28 (s, 3H, C(CH 3)2), 1.12 (s, 3H, C(CH 3)2), 0.40 (s, 9H, J = 7.69 Hz, OSi(CH 3) 3). FI1R (thin film), cm· 1: 3279 (m, C=C-H), 2953 (m), 2127 (w, C=C), 1728 (s, ester C=O), 1698 (s, aldehyde C=O), 1622 (s), 1514 (m), 1411 (m), 1254 (s), 1093 (s), 959 (m). 226 TLC (30% EtOAc in Hexanes), Rf. 112: 0.29 (fluoresces under UV, anisaldehyde) 113: 0.64 (fluoresces under UV, anisaldehyde) 227 II~ H CHO 0.$ 0 H3C O ~ O M E M ~ 113 CH3 11 LiN(TMS)2, CeCl3, 11 THF,-78°C 59% ,i 0 0 H3COWIJ' "--:::: OMEM ~ I ~ 4" CH3 114 Cyclic alcohol 114 A suspension of aldehyde 113 (100 mg, 0.144 mmol, 1 equiv) and cerium(III) chloride (107 mg, 0.433 mmol, 3 equiv) in TI-IF (7 mL) was stirred at 23 'C for 10 min and cooled to -78 °C. Lithium hexamethyldisilazide (721 µL of a 1.0 M solution in hexanes, 0.721 mmol, 5 equiv) was added dropwise via syringe over 2 min. The reaction was checked by thin-layer chromatography (TLC) (50% ethyl acetate in hexanes) and found to be incomplete. Additional lithium hexamethyldisilazide (288 µL of a 1.0 M solution in hexanes, 0.288 mmol, 2 equiv) was added from a syringe, and the TLC of the reaction re-examined. One last portion of lithium hexamethyldisilazide (288 µL of a 1.0 M solution in hexanes, 0.288 mmol, 2 equiv) was added via syringe. After maintaining the reaction mixture at -78 'C for an additional 10 min, excess base was quenched by the addition of saturated aqueous ammonium chloride (10 mL). The reaction mixture was warmed to 23 °C and partitioned between 1: 1 ethyl acetate/hexanes (30 mL) and water (30 mL). The aqueous layer was further extracted with 1:1 ethyl acetate/hexanes (2 30-mL portions). The combined organic extracts were washed once with saturated aqueous 228 sodium chloride (50 mL), and were dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (25% ethyl acetate in hexanes grading to 40% ethyl acetate in hexanes) to provide cyclic alcohol 114 (59 mg, 59%) as a yellow oil. 7.63 (d, lH, J =9.28 Hz, C4" H), 7.45 (br s, lH, C8" H), 7.18 (d, lH, J = 9.28 Hz, C3" H), 7.01 (br s, lH, C6" H), 6.50 (t, lH, J = 2.20 Hz, CIO H), 6.27 (m, lH, Cl 1 H), 5.36 (d, lH, J = 8.30 Hz, C8 H), 5.30 (abq, 2H, J = 6.96 Hz, !:w = 9.52 Hz, OCH2OCH 2CH2OCH3), 3.96-3.84 (complex, 3H, Cl3 H and OCH 2OCH2CH2OCH 3), 3.78 (dd, lH, J = 8.54, 6.59 Hz, C14 H), 3.60 (s, 3H, CT' OCH 3), 3.50 (m, 2H, OCH 2OCH 2CH 2OCH 3), 3.42 (dd, lH, J = 6.10, 4.64 Hz, Cl4 H), 3.14 (s, 3H, OCH 2OCH2CH2 OCH 3), 3.11 (s, lH, C5 H), 3.05 (d, lH, J = 8.05 Hz, OH), 2.90 (dd, lH, J = 14.64, 2.93 Hz, Cl2 aH), 2.76 (dd, lH, J = 14.65, 7.32 Hz, C12 ~H), 2.27 (s, 3H, C5" CH3), 1.44 (s, 3H, CH(CH 3 ) 2), 1.22 (s, 3H, CH(CH 3) 2), 0.31 (s, 9H, OSi(CH 3) 3). 229 FI1R (thin film), cm· 1: 3457 (m, OH), 2950 (m), 1722 (m, C=O), 1621 (s), 1411 (m), 1255 (s), 1207 (m), 1158 (m), 1092 (s), 960 (m). TI..C (50% EtOAc in Hexanes), Rf.: 113: 0.43 (fluoresces under UV, anisaldehyde) 114: 0.33 (fluoresces under UV, anisaldehyde) 230 5 11 11 11 TMSOTI, 2,6-lutidine, 11 CH2a2, -78 °C OTMS 99% Bis-TMS ether 11 S 2,6-Lutidine (17 µL, 0.14\ mmol, 20 equiv) and trimethylsilyl trifluoromethanesulfonate (14 µL, 0.072 mmol, 10 equiv) were added sequentially via syringe to a solution of alcohol 114 (5.0 mg, 0.0072 mmol, 1 equiv) in dichloromethane (1 mL) at -78 °C. The resultant pale yellow solution was maintained at -78 °C for 20 min, and excess silylating reagent was quenched by the addition of triethylamine (0.1 mL) and methanol (0.1 mL). The reaction mixture was warmed to 23 °C and partitioned between 1:1 ethyl acetate/hexanes (5 mL) and water (10 mL). The layers were separated and the aqueous layer was further extracted with 1:1 ethyl acetate/hexanes (2 5-mL portions). The combined organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (25% ethyl acetate in hexanes) afforded Bis-TMS ether 115 (5.5 mg, 99%) as a colorless oil. 231 7.65 (d, lH, J = 9.28 Hz, C4" H), 7.40 (s, lH, C8" H), 7.34 (d, lH, J = 9.28 Hz, C3" H), 7.09 (s, lH, C6" H), 6.65 (t, lH, J = 1.95 Hz, ClO H), 6.37 (m, lH, Cl 1 H), 5.63 (s, lH, C8 H), 5.27 (abq, 2H, J = 7.08 Hz, Av =14.64 Hz, OCH2OCH 2CH 20CH 3), 3.88 (dd, 2H, J = 9.52, 4.15 Hz, OCH 2OCH 2CH 20CH3), 3.85 (dd, lH, J = 8.54, 6.83 Hz, C13 H), 3.76 (dd, lH, J = 8.55, 6.59 Hz, C14 H), 3.68 (s, 3H, C7" OCH 3), 3.~8-3.43 (complex, 3H, C14 H and OCH 2OCH 2CH 2OCH3), 3.16 (s, 3H, OCH 2OCH 2CH2OCH3), 3.08 (s, lH, C5 H), 2.93 (dd, lH, J = 14.65, 3.18 Hz, Cl2 aH), 2.81 (dd, lH, J = 14.65, 7.33 Hz, Cl2 ~H), 2.27 (s, 3H, C5" CH 3), 1.44 (s, 3H, CH(CH 3) 2), 1.21 (s, 3H, CH(CH 3) 2), 0.33 (s, 9H, OSi(CH 3\), 0.21 (s, 9H, OSi(CH 3)3). lLC (30% EtOAc in Hexanes), Rf 114: 0.38 (fluoresces under UV, anisaldehyde) 115: 0.55 (fluoresces under UV, anisaldehyde) 232 11 11 II 11 El:)N•3HF, THF, o °C Diol 116 Triethylamine trihydrofluoride (37 µL, 0.30 mmol, 3 equiv) was added via syringe to a solution of alcohol 114 (70 mg, 0.101 mmol, 1 equiv) in THF (7 mL) at O °C. The resultant solution was maintained at O °C for 40 min, and excess acid was quenched by the addition of saturated aqueous sodium bicarbonate (5 mL). The reaction mixture was then partitioned between 1:1 ethyl acetate in hexanes (10 mL) and water (10 mL). The layers were separated, and the aqueous layer was further extracted with 1: 1 ethyl acetatelhexanes (2 10-mL portions). concentrated. purification. The combined organics were dried over sodium sulfate and The diol 116 was carried directly to the next reaction without further 233 7.65 (d, lH, J = 9.28 Hz, C4" H), 7.41 (s, lH, C8" H), 7.21 (d, lH, J = 9.28 Hz, C3" H), 7.01 (s, lH, C6" H), 6.60 (s, lH, ClO H), 6.30 (br s, lH, Cll H), 5.45 (br s, lH, C8 H), 5.32 (m, 2H, OCH 2OCH 2CH2OCH 3), 3.94-3.87 (complex, 3H, C13 H and OCH 2OCH2CH2OCH3), 3.78 (dd, lH, J = 9.03, 6.83 Hz, C14 H), 3.64 (s, 3H, CT' OCH 3), 3.61 (m, lH, C14 H), 3.45 (m, 2H, OCH 2OCH2CH2OCH 3), 3.29 (s, lH, C5 H), 3.16 (s, 3H, OCH2OCH 2CH2OCH 3), 2.90 (dd, lH, J = 14.89, 3.42 Hz, C12 aH), 2.79 (dd, lH, J = 14.86, 7.08 Hz, C12 ~H), 2.29 (s, 3H, C5" CH 3), 1.49 (s, 3H, CH(CH 3) 2), 1.23 (s, 3H, CH(CH 3) 2). 114: 0.68 (fluoresces under UV, anisaldehyde) 116: 0.08 (fluoresces under UV, anisaldehyde) 234 II 0~ 11 CH2a 2, -78 °C 0 11 0 H3 C O w < -.,• OMEM H3C O ~ O M E M lyU CH3 11 TBSOTf, 2,6-lutidine, ::::,... I .& 4• 116 CH3 117 TBS ether 11 7 2,6-Lutidine (235 µL, 2.02 mmol, 20 equiv) and tert-butyldimethylsilyl trifluoromethanesulfonate (232 µL, 1.01 mmol, 10 equiv) were added sequentially via syringe to a solution of diol 116 (crude from previous reaction, assume 0.10 mmol, 1 equiv) in dichloromethane (10 mL) at -78 °C. The resultant pale yellow solution was maintained at -78 °C for 40 min, and excess silylating reagent was quenched by the addition of triethylamine (1 mL) and methanol (1 mL). The reaction mixture was warmed to 23 °C and partitioned between 1:1 ethyl acetate/hexanes (50 mL) and water (50 mL). The layers were separated and the aqueous layer was further extracted with 1: 1 ethyl acetate/hexanes (2 50-mL portions). The combined organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (25% ethyl acetate in hexanes grading to 40% ethyl acetate in hexanes) afforded TBS ether 117 (43 mg, 58% over two steps) as a colorless oil. 235 7.62 (d, lH, J = 9.28 Hz, C4" H), 7.37 (s, lH, C8" H), 7.30 (d, lH, J = 9.28 Hz, C3" H), 7.21-6.98 (obscured, lH, C6" H), 6.65 (t, lH, J = 2.20 Hz, ClO H), 6.27 (m, lH, Cll H), 5.45 (s, lH, C8 H), 5.26 (abq, 2H, J = 7.08 Hz, ~v =14.16 Hz, OCH 2OCH 2CH 20CH3), 3.96-3.88 (complex, 3H, Cl3 Hand OCH20CH2CH 2OCH 3), 3.76 (dd, lH, J = 8.79, 6.59 Hz, Cl4 H), 3.69 (s, 3H, CT' OCH 3 ), 3.55 (t, lH, J = 6.10 Hz, Cl4 H), 3.45 (m, OCH 2OCH 2CH 20CH 3), 3.16 2H, (s, 3H, OCH 2OCH 2CH 2OCH 3), 3.15 (s, lH, C5 H), 2.86 (dd, lH, J = 14.90, 3.18 Hz, C12 aH), 2.64 (dd, lH, J = 14.89, 7.32 Hz, C12 BH), 2.27 (s, 3H, C5" CH 3), 1.47 (s, 3H, CH(CH 3) 2), 1.21 (s, 3H, CH(CH 3) 2), 0.98 (s, 9H, OSiC(CH 3MCH 3) 2), OSiC(CH 3)iCH 3) 2), 0.23 0.12 OSiC(CH 3)/CH 3) 2). TLC (50% EtOAc in Hexanes), Rf: 117: 0.34 (fluoresces under UV, anisaldehyde) (s, (s, 3H, 3H, 236 11 11 II 11 CH3S02CI, Et3N, 0.: 0 H3C O ~ O M E M lyV CH3 117 OTBS 12 CH2Cl 2,0 °C / 0 Cl 0 H3C O ~ O M E M W. CH 3 ,. 119 Chloride 119 Triethylamine (14 µL, 0.10 mmol, 25 equiv) and methanesulfonyl chloride (20 µL of a 1.3 M solution in dichloromethane, 0.026 mmol, 6 equiv) were added sequentially via syringe to a solution of TBS ether 117 (3.0 mg, 4.1 x 10·3 mmol, 1 equiv) in dichloromethane (0.5 mL) at 0 0 C. After 10 min at 0 °C, the reaction mixture was partitioned between hexanes (2 mL) and water (2 mL). The layers were separated and the aqueous layer was further extracted with hexanes (2 2-mL portions). The combined organics were dried over sodium sulfate, and concentrated to a volume of approximately 0.1 mL. Purification of the concentrate by flash column chromatography (40% ethyl acetate in hexanes) was followed by pooling the fractions containing the product. The pooled fractions were concentrated to a volume of ca. 0.1 mL. A 0.5 mL portion of deuteriated benzene (99.5 atom % D) was added to the concentrated solution, and the resultant solution was concentrated to a volume of ca. 0.1 mL. repeated 4 times. This procedure was After the last iteration, the concentrated solution was taken up in 237 approximately 0.4 mL deuteriated benzene (99.95 atom % D). Analysis of the sample by 1 H NMR indicated it to be chloride 119 (yield not determined). 7.64 (d, lH, J = 9.28 Hz, C4" H), 7.41 (s, lH, C8" H), 7.31 (d, lH, J = 9.28 Hz, C3" H), 7.00 (s, lH, C6" H), 5.82 (d, lH, J = 6.11 Hz, ClO H), 5.46 (s, lH, C8 H), 5.32 (rn, lH, C 11 H), 5.25 (s, 2H, OCH 2OCH 2CH2OCH3), 4.00 (dd, lH, J = 8.45, 5.37 Hz, Cl3 H), 3.91 (rn, 2H, OCH2OCH 2CH2 OCH 3), 3.81 (dd, lH, J = 8.79, 6.59 Hz, Cl4 H), 3.60 (s, 3H, C7" OCH 3), 3.56 (t, lH, J = 6.35 Hz, C14 H), 3.51 (rn, 2H, OCH2 OCH 2CH 2 OCH 3), 3.21 (d, IH, J = 1.46 Hz, C5 H), 3.20 (s, 3H, OCH 2OCH2CH2OCH 3), 2.93 (dm, lH, J = 17.09 Hz, C12 ~H), 2.68 (d, lH, J = 17.82 Hz, Cl2 aH), 2.26 (s, 3H, C5" CH 3), 1.51 (s, 3H, CH(CH 3) 2), 1.23 (s, 3H, CH(CH 3) 2), 0.90 (s, 9H, OSiC(CH 3)iCH 3 ) 2 ), 0.23 (s, 3H, OSiC(CH 3)iCH 3) 2), 0.19 (s, OSiC(CH 3)iCH 3)2)- 3H, 238 1LC (50% EtOAc in Hexanes), Rf. 117: 0.30 (fluoresces under UV, anisaldehyde) 119: 0.51 (fluoresces under UV, anisaldehyde) 239 Chapter 4 Enantioselective Synthesis of Neocarzinostatin Chromophore Aglycone 240 Synthetic Plan Having exhausted many potential routes for the preparation of the conjugated dienediyne core of neocarzinostatin chromophore by the transposition of the allylic alcohols discussed in the previous chapters, attention was turned to a new strategy. It was anticipated that epoxidation of the C-9 - C-10 olefin (see 120) would furnish an intermediate that, upon activation of the C-8 alcohol, would be stereoselectively transformed into the C-10 allylic alcohol under radical-mediated or reductive conditions. Such a process conducted within the epoxy alcohol 120 would produce neocarzinostatin chromophore aglycone (6) directly. This chapter describes the diastereoselective introduction of the C-9 - C-10 epoxide, optimization of the synthetic sequence for the preparation of epoxy alcohol 120, and its successful conversion into neocarzinostatin chromophore aglycone (6). ~ 11 11 11 11 -.. ------~ ? The most direct means by which to access C-9 - C-10 epoxide-containing intermediates, the epoxidation of known nine-membered ring-containing substrates, was studied extensively. The nine-membered ring alcohol 68 was silylated by treatment with TESOTf (6 equiv) and 2,6-lutidine (10 equiv) in dichloromethane at -78 °C to provide the tris-silyl ether 121 in quantitative yield. 77 A number of conditions were examined for the 241 TESOTf, 2,6-lutidine, 11 11 TMSO,,.. Ji 9 H ·,,OH 11 99% TBSO. 10 lBSO.: 11 CH2Cl2, -78 cc 68 121 introduction of the epoxide into 121, including m-chloroperoxybenzoic acid (m-CPBA, 94% purity, both with and without dioxirane, 79 methyl(trifluoromethyl) sodium dimethyldioxirane,78 carbonate), acid, 80 4-nitroperoxybenzoic and the peroxycarboximidic acid derived from the combination of 90% hydrogen peroxide and acetonitrile,81 all of which resulted in recovery of 121, decomposition of 121, or the formation of a complex mixture of products. A single set of conditions, trifluoroperoxyacetic acid (6 equiv) buffered with solid dibasic potassium phosphate (20 equiv) in dichloromethane at O °C, afforded the desired epoxidized product 122. The stereochemistry of the product was determined by inspection of the coupling constant between H-10 and H-11, in this case O Hz, which indicated a trans substitution pattern, the result of epoxidation from the least hindered face of 121. Unfortunately, significant decomposition of the substrate and/or product occurred under the reaction conditions, necessitating the development of an alternative method for introduction of the epoxide. CF3C03H, K2HP04, 11 ,: 11 CH 2Cl 2, o cc 11 H TBS0.:11 10 lBSO 121 11 122 242 11 o"' w 11 o H3CO~OMEM CH 3 114 116 R = TMS R=H Use of the C-8 alcohol to direct the epoxidation reaction was next examined. Both the known alcohol 114 and diol 116 were subjected to conditions known to effect directed epoxidations. These conditions included m-CPBA, the combination of Ti(Oi-Pr)4 and tertbutyl hydroperoxide (TBHP), 83 and the combination of VO(acac)2 and TBHP. 84 In each case either unreacted starting material was recovered or the substrate slowly underwent nonspecific decomposition. The ligand-accelerated conditions of the Sharpless asymmetric epoxidation were also examined using both (+)- and (-)-DET and employing both stoichiometric and suprastoichiometric amounts of reagents. 31 II 11 The reaction of 1MS II (+)·DET, Ti(Oi-Pr) 4 , 11 TBHP,4AMS, OH 0-i w d 0 H3C O ~ O M E M CH3 0 114 OH o H3C O ~ O M E M yU CH3 123 243 ether 114 with (+)-DET (12 equiv), Ti(Oi-Pr\ (10 equiv), and TBHP (5 equiv) with 4A MS in dichloromethane at -20 °C afforded a product whose 1H NMR spectrum was consistent with the formation of the epoxy alcohol 123.31 The purification of epoxide 123 was complicated by the laborious separation of the product 123 from the residual (+)-DET. More importantly, the instability of this diastereomeric series (cf. Ch. 2) made manipulation of the starting olefin 114 and the product 123 difficult This instability provided cause for concern when the further transformations required for completion of the synthesis were considered. Consequently, the alternative strategy of introducing the C-9 - C-10 epoxide prior to closure of the nine-membered ring was investigated. Although unclear at the outset, it was not expected that the introduction of the C-9 C-10 epoxide prior to the closure of the nine-membered ring would have a marked effect on the ring-closure reaction. Based on inspection of molecular models, it was concluded that the geometry of an epoxy aldehyde having a structure such as 124 should not differ significantly from the corresponding a,~-unsaturated aldehyde intermediates (e.g., 13) known to favor intramolecular acetylide addition, and should provide the cyclized alcohol upon treatment with base (Figure 2). The first approach to accessing an epoxy aldehyde intermediate such as 12 4 involved the coupling of the epoxydiyne component 20 with an epoxide-containing ketone corresponding to the enone dimethyl acetal (+)-21. Accordingly, the enone dimethyl acetal (+)-21 was epoxidized to afford ketone 125 in 91% yield and ~95% diastereomeric 0 &CH(OCH3h 30% H2O2, safd K2C03, CH3OH,0 °C TBSO.: 91% (+)-21 125 enrichment (1H NMR analysis) by treatment with 30% hydrogen peroxide (2 equiv) in a 15:1 mixture of methanol and saturated aqueous potassium carbonate at O 0 C. 85 Removal 244 13 124 II i1 II TMSO,,. H CHO TMSO,,. i1 8 H .,,CHO 0 Figure 2. 124. 10 10 13 124 Ball and Stick Depictions of Ring-Closure Substrates 13 and 245 of the TBS group of 125 followed preparation of the Mosher ester and 1H NMR analysis indicated that the epoxy ketone was of ~85% ee. The epoxy ketone 125 was then examined as a substrate for addition of the epoxydiyne component 20. Deprotonation of epoxydiyne 20 with a base such as LiN(TMS)2 in THF at -78 ~ followed by addition of the ketone 125 afforded a mixture of diastereomers 126 in low yield (10-15%). Subsequent studies carried out by Dr. Y. Wu in this group to optimize both the yield and the diastereoselectivity of this coupling did afford some improvement in the yield of the reaction. An approximately 70% combined yield was obtained when the reaction was carried out with LiN(TMS) 2 in the presence of the crown ether 12-C-4, but the diastereoselectivity remained unacceptable (ca. 3: 1, absolute stereochemistry of the individual diastereomers not assigned), and so this strategy was discontinued. i. base, additive, THF,-78 °C TBS ii. 125 .... CH(OCH 3)~ 0 TBSO,:: 126 The epoxidation of a,~-unsaturated aldehyde intermediates obtained subsequent to the coupling of the epoxydiyne 20 and the enone dimethyl acetal (+)-21 was next examined. Enal 127, obtained by hydrolysis of known dimethyl acetal 46, was inert to epoxidation under the conditions used to prepare ketone 125. Use of stronger bases, such as DBU, 86 Triton B, 87 or sodium hydroxide, 88 resulted in the formation of complex reaction mixtures. Treatment of either enal 128 or enal 50 with 30% hydrogen peroxide (2 equiv) in a mixture of saturated sodium bicarbonate in THF (1:40) at 0 ~ produced, in all cases, mixtures of epoxy aldehyde diastereomers. 89 These diastereomers could be separated and purified, but this methodology was not considered to be preparatively useful, 246 as both the yields and the diastereoselectivities observed in these reactions were low. Accordingly, alternative means were pursued for the introduction of the C-9 - C-10 epoxide with a higher degree of stereocontrol. 0 o=< O'' II HO,,. i i II TBS HO,,.. CHO o.:: TBSO,:: 127 w 11 H CHO HO,,. H CHO o H3C O ~ O H CH3 128 The final strategy involved the application of the Sharpless asymmetric epoxidation to diastereoselectively incorporate the epoxide. 31 With the goal remaining the preparation of a ring-closure substrate having the general structure A, it was anticipated that the epoxy aldehyde could be prepared from the allylic alcohol B, which was expected to be a suitable substrate for the epoxidation reaction. The intermediate B could be obtained by the 1,2reduction of an a,J3-unsaturated aldehyde having the general structure C, which should be readily accessible through known methodology. 0 o=< O''' II RO,,.. i H => II RO,,.. i H => RO,,.. 0 RO.: A H CHO .,,CHO B C 247 Following this strategy, studies directed toward the preparation of a ring-closure intennediate commenced with the known a,~-unsaturated aldehyde 66. Silylation of the tertiary alcohol with TESOTf (6 equiv) and 2,6-lutidine (10 equiv) in dichloromethane at -78 °C afforded the enal (129) in 85% yield (Scheme XVIII). 77 The aldehyde was then reduced by treatment of the enal with DIBAL (1.1 equiv) in toluene at-78 °C, to afford the allylic alcohol 130 in 81 % yield. Sharpless asymmetric epoxidation employing (+)-diethyl tartrate (6 equiv), Ti(Oi-Pr)4 (5 equiv), and TBHP (5 equiv) with 4A MS in dichloromethane at -20 °C produced the expected epoxy alcohol 131 in 88% yield. 31 The stereoselectivity of the epoxidation proceeded in the requisite sense, as evidenced by the 0 Hz coupling constant between H-10 and H-11 in the product 131. 56 Oxidation of the epoxy alcohol under Swem conditions provided the epoxy aldehyde 132 in 86% yield. 90 Although the aldehyde was observed to streak considerably when examined by thin-layer chromatography on silica gel (presumed hydrate), no hydrate was observed by 1H NMR analysis of 132 in deuteriated benzene. The key step, the closure of the nine-membered ring, was effected by treatment of a suspension of the epoxy aldehyde 132 and cerium(III) chloride in THF at -78 °C with LiN(TMS) 2 (12 equiv), affording an approximately 50% yield of the cyclized epoxy alcohol 133. 13 ' 19 An improvement in the yield of the reaction was realized by the substitution of dry lithium chloride for the cerium(Im chloride. Under these modified conditions (50 equiv LiCl, 10 equiv LiN(TMS) 2 , THF, -78 °C), the cyclized product 133 could be obtained in 67% yield. The ring-closure reaction also proceeded in the absence of any additive (LiN(TMS) 2, THF -78 °C), but the reaction was not as clean, and the conversion was low (TLC analysis). It should be noted that the cyclization product 133 was found to be remarkably stable both in neat form and in solution, especially relative to many of the other nine-membered ring intennediates prepared during the studies discussed in Chapters 2 and 3. 248 Scheme XVIII 1. TESOTf, 2,6-lutidine, H HO,,.. II~ CH2C'2, -78 °C, 85% TESO,,. H CHO 2. DIBAL, PhCH3, -78°C,81% TBSO~ TBSO.: 66 130 (+)-DET, Ti(Oi:-Pr)4 , TBHP, 4A MS, CH2O2, -20 "C II i TESO,,.. (COCl) 2, DMSO, Et3 N, H CH2O 2, -78 ➔ O "C 88% 86% TBso"' 131 H3C, H3C, 0 X H3C 0''' 0 H3Cxo,•· 11 TESO,•.. i H .... CHO 0 ,i TBSO 132 LiN(TMS) 2 , LiCI, 11 THF, -78 °C 11 H 67% ,, TBSO 133 249 The alcohol 133 was next examined as a substrate for conversion of the epoxy alcohol into the desired allylic alcohol. Reaction of alcohol 133 with thiocarbonyldiirnidazole (CS(lm) 2 , 10 equiv) and DMAP (5 equiv) in dichloromethane at 23 °C afforded thiocarbonylimidazolide 134 in 89% yield (Scheme XIX). Treatment of a deoxygenated solution of 134 in benzene with tributyltin hydride (10 equiv) at 23 °cn, afforded a product whose 1H NMR spectrum indicated that the epoxide-containing fivemembered ring substructure remained intact (no added radical initiator was necessary for this reaction to occur). A set of olefinic doublets was also visible by analysis of the 1H NMR spectrum, and suggesting the presence of a double bond within a five- or sixmembered ring. 93 The C-13 - C-14 substructure, complete with the acetonide was also Scheme XIX 1, 1'-thiocarbonyldiimidazole, 11 11 H DMAP, CH 2Cl 2, 23 °C 89% TBSO.:· TBSO.:· 134 133 .: TBSO 135 250 visible within the 1H NMR spectrum. The high-resolution mass spectrum of the product was consistent with the loss of the thiocarbonylimidazolide (including the oxygen) and the addition of two hydrogen atoms. Although the structure was not rigorously proven, the data are all consistent with the formation of a structure such as 13 5, resulting from generation of the carbon-centered radical at C-8 and subsequent opening of the C-4 - C-5 epoxide. In order to obtain a substrate analogous to 133 in which the C-1 alcohol protecting group could be selectively removed in the presence of the C-11 TBS ether, the analogous TMS-containing substrate 139 was prepared (Scheme XX). In this sequence, the oxidation of the Sharpless epoxidation product, epoxy alcohol 13 7, was accomplished with the Dess-Martin periodinane (2 equiv) buffered with pyridine (20 equiv) in Scheme XX 11 TMSO,,. H 1. DIBAL, PhCH 3, -78 °C, 94% II i TMSO,,.. CHO 2. (+)-DET, Ti(Oi-Pr)4 , TBHP, 3A MS, CH 2C'2, -20 °C, 91% rsso' 137 67 1. Dess-Martin periocinane, Py, CH2C'2, 23 °C, 97% 11 2. LiN(TMSh, LiCI, THF, -78 "C, 80% TBSO-- 139 11 H 251 dichloromethane at 23 °C, affording the epoxy aldehyde in 97% yield.94 The closure of the nine-membered ring, effected by the addition of LiN(TMS)2 (5 equiv) to a suspension of LiCl (50 equiv) and the epoxy aldehyde in THF at -78 °C, proceeded quite cleanly, providing the alcohol 139 in 80% yield. The 1MS group of intermediate 139 could be removed by treatment with (±)camphorsulfonic acid (5 equiv) in a 2:1 mixture of acetonitrile and water at 23 °C to afford the diol 140 in 47% yield, along with the triol 141, resulting from cleavage of both silyl groups (24% yield). In an effort to favor the reactivity of the C-9 - C-10 epoxide, attempts were made to prepare a thiocarbonate between the C-1 and C-8 alcohols. Accordingly, diol .• 0 H3Cx H3C,, 0 H3Cxo••· H3C 11 11 o••· (±)·CSA, 2: 1 CH 3CN/H 2O, 23 °C 11 11 11 H + II H 12 TBSO,.: 10 139 TBSO.: 140 (47%) HO.: 141 (24%) 140 was treated with thiocarbonyldiimidazole (10 equiv) and DMAP (5 equiv) in dichloromethane at 23 °C. Under these conditions, the acyclic thiocarbonylimidazolide 142 was isolated in 90% yield. All attempts to effect the intramolecular cyclization of this intermediate, including addition of base (20 equiv DBU in toluene), heating to 50 °C in the polar solvent DMF, or activation of the imidazole ring by the addition of methyl triflate, 95 failed to provide the desired thiocarbonate. 252 II 1, 1'-lhiocarbonyldiimidazole, 11 11 DMAP, CH 2Cl 2, 23 °C 11 H s ·~o)l~ N 90% 0 '=1 TBSO.: 142 140 The reaction of alcohol 139 with the one-electron reductant dicyclopentadienyl titanium(III) chloride was also examined. 96 This reagent, prepared by in situ reduction of dicyclopentadienyl titanium(IV) chloride with granular zinc in THF at 23 °C, is known to convert epoxides to the corresponding alcohols in which the most substituted C-O bond has been cleaved.96 In the case of epoxy alcohol 139, this would correspond to the cleavage of the C-9 - 0 bond, producing a secondary alcohol at C-10. The C-8 mesylate 143 was prepared in 78% yield from intermediate 139 (10 equiv methanesulfonyl chloride, 25 equiv H3C, 0 H3CXO X H3C 0'' H3C Cp2TiCI (ZnCl2), 11 11 H .:· THF, 23 °C 10 TBSO TBSO 143 H TBSO.: 144 139 11 0'' 11 Cp2TiCI (ZnC1 2), THF, 23 °C H rsso" 145 253 Et3N, dichloromethane, 0 °C)59 with the hope of effecting reductive opening of the C-9 C-10 epoxide and elimination of the C-8 mesylate concurrently. Treatment of either the alcohol 139 or the mesylate 143 with dicyclopentadienyl titanium(III) chloride (3 equiv) in THF at 23 °C afforded products in which the C-4 - C-5 epoxides had been selectively opened. The products, diol 144 (from alcohol 139) and mesylate 145 (from mesylate 143) were each isolated as a single diastereomer having undetermined stereochemistry at C-4. In order to favor reactivity at the C-9 - C-10 epoxide, studies were initiated to introduce the C-1 - C-12 olefin. The presence of this double bond would increase the reactivity of the desired epoxide in two ways: 1) the strain within both the five-membered ring and the epoxide would be increased, and the relief of this strain would be a driving force for epoxide opening; and 2) with the olefin in place, cleavage of the C-9 - 0 bond should be favored by the production of either a stabilized allylic radical or an allyl cation, depending upon the reaction conditions. Preliminary studies of the elimination of the C-1 alcohol were conducted with the triethylsilyl ether derived in 79% yield by treatment of the diol 140 with triethylsilyl chloride (5 equiv) and imidazole (5 equiv) in dichloromethane at O 0 C. Elimination occurred upon treatment of the product tertiary alcohol with triflic anhydride (100 equiv) and 2,6-di-tert-butylpyridine (200 equiv) in dichloromethane (-78 °C and warming to 23 °C) to afford the olefin 147 in 45% yield. 1. E~SiCI, imidazole, CH 2C12, O °C, 79% 11 2. Tip, 2,6-di-tert-butylpyridine, CH2Cl2, -78 ➔ 23 °C, 45% TBSO.: 140 TBSO.: 147 11 254 The presence of the C-1 - C-12 olefin markedly changed the reactivity of the substrate under radical conditions. The thiocarbonylimidazolide 149 could be prepared by removal of the TES group of olefin 147 with (±)-camphorsulfonic acid (5 equiv) in 2:1 acetonitrile/water at 23 °C followed by reaction of the resultant secondary alcohol with thiocarbonyldiimidazole (10 equiv) and DMAP (5 equiv) in dichloromethane at 23 °C. In contrast to thiocarbonylimidazolide 134, no reaction was observed upon treatment of a deoxygenated solution of the thiocarbonylimidazolide 14 9 in benzene with tributyltin hydride (20 equiv). 92 Addition of a catalytic amount of triethylborane (E½B) and oxygen resulted in the formation of a complex reaction mixture. 97 The bis-silyl ether 147 was also reacted with tributyltin hydride (20 equiv) and catalytic Et3B and oxygen in benzene at 23 °C and once again multiple products were observed to form. 97 Additionally, reaction of the intermediate 14 7 with the one-electron reductant dicyclopentadienyl titanium(III) chloride afforded a complex mixture of products.96 1. {±)-CSA, 2:1 CH3CN/H2O, 23 °C 11 TBS0.:- 147 11 11 2. CS{lm)i, DMAP, CH 2Cl 2 , 23 °C TBSO..:' 149 With an eye directed toward the preparation of intermediates bearing additional functionalization, and with the prospect of deactivating the C-4 - C-5 epoxide, a synthetic route to an olefin-containing intermediate that also incorporated the ethylene carbonate was developed. The known intermediate diol 47 was silylated with TIPS triflate (5 equiv) and 2,6-lutidine (10 equiv) in dichloromethane at-78 °C to provide the TIPS ether 150 in 89% yield (Scheme XXI). 73 As before, the dimethyl acetal was hydrolyzed with p-TsOH in methanol at 23 °C,65 and the tertiary alcohol was silylated with 1MSOTf (6 equiv) and 255 Scheme XXI TIPSOTf, 2,6-lutidine, 11 CH2Cl 2, -78 -+ o 0 c HO,,,. 89% TlPSO.: 47 150 1. I>"TsOH, acetone, 23 "C 1. DIBAL, PhCH3, -78 "C, 96% 2. TMSOTI, 2,6-lutidine, 2. (+)-DET, Ti(i-Pr)4 , TBHP, CH2a 2, -78 °C II i TMSO,,.. 4A MS, CH2C'2, -78 C, 89% H CHO 93% 3. Dess-Martin periocinane, Py, CH 2C'2, 23 °C, 94% 152 H3CXO H3C H3CXO O''' H3C 11 i .... CHO 0 155 11 THF, -78°C H TMSO,, . TlPSO' o••· LiN(TMS)2 , LiCI, 11 H 62% ,· TlPSO 156 256 2,6-lutidine (10 equiv) in dichloromethane at -78 °C,54 affording TMS ether 152 in 93% overall yield from 150. Introduction of the C-9 - C-10 epoxide was accomplished in analogy to other systems: 1,2-reduction with DIBAL (1.2 equiv) in toluene at -78 CC provided the allylic alcohol (153) in 96% yield, epoxidation under Sharpless conditions produced the epoxy alcohol (154) in 89% yield,31 and oxidation with Dess-Martin periodinane (2 equiv) buffered with pyridine (10 equiv) in dichloromethane at 23 CC afforded the epoxy aldehyde 155 in 94% yield. 94 Closure of the nine-membered ring was effected as before, as addition of LiN(TMS)2 (5 equiv) to a suspension of 155 and LiCl (50 equiv) in TIIF at-78 °C produced the ring-closed alcohol 156 in 62% yield. 91 Protection of the C-11 alcohol of 156 as a TIPS ether was intended to allow for selective removal of the C-13 - C-14 acetonide and subsequent introduction of the ethylene carbonate. Accordingly, treatment of the alcohol 156 with 1% p-TsOH in methanol at 23 °C afforded the tetraol 157 in 62% yield and the incompletely deprotected diol 158 in 10% yield. The reaction was generally not allowed to proceed until complete conversion of 15 6 to 157 had occurred, as by that time a substantial amount of very polar material, possibly from the cleavage of the TIPS ether, would form (TLC analysis). HO H3C,,, 0 H3CXO H3 C H3CXO''' o••· 1% p-TsOH/CH 3OH 11 23°c 11 11 .:· llPSO 156 11 H H TIPSO.: + H TIPSO.: 157 158 (62%) (10%) The stereochemistry of the C-8 alcohol center formed during the closure of the ninemembered ring (155 ➔ 156) was established by the preparation of a cyclic disiloxane derivative of the diol 158. 19 Accordingly, treatment of 158 with 1,3-dichloro-1,1,3,3- 257 tetra-iso-propyldisiloxane (5 equiv) and imidazole (20 equiv) in DMF at 23 °C afforded a single product after silica gel and Sephadex chromatographies. The 1H NMR, FTIR, and high-resolution mass spectrum of the product were in full accord with the formation of the cyclic disiloxane 15 9, thereby verifying that the stereochemical outcome of the acetylide addition into the epoxy aldehyde proceeded in analogy to the ring-closure of the related a,f3-unsaturated aldehydes (cf. 13 ➔ 14 and 52 ➔ 53). TIPSC>,... imidazole, DMF, 23 °C 44% 158 159 The tetraol 157 was next treated with carbonyldiimidazole (1.5 equiv, added in two 0.75 equiv portions at 15 min intervals) in THF starting at 0 °C, then warming to 23 °C. 53 At least three products were obtained from the reaction mixture. Isolation and characterization of these products showed them to include not only the desired carbonate 160, but also the intermediate C-8 carbonylimidazolides of both the starting tetraol 15 7 0 i. COi, THF, O ➔ 23 °C o=<o•·· ii. (±).CSA, 2:1 11 11 11 CH 3CN/ H2O, 23 °C 72% TIPSC>.: 157 TIPSO.:· 160 11 258 and the product 160. Although these intermediates were expected to hydrolyze upon aqueous work-up of the reaction mixture, they were found to be surprisingly stable to even silica gel chromatographic purification. Subsequent to this finding, the crude reaction mixture obtained from the aqueous work-up was treated directly with (±)-camphorsulfonic acid in a 2:1 mixture of acetonitrile and water to provide the carbonate 160 in 72% yield along with unreacted tetraol 157 (23%). In order to selectively activate and eliminate the C-1 alcohol, the C-8 alcohol of diol 160 was selectively protected by reaction with triethylsilyl chloride (7 equiv) and imidazole (20 equiv) in dichloromethane at O °C, affording the TES ether 161 in 97% yield (Scheme :xxm. The first attempts to carry out the elimination of the C-1 alcohol employed triflic anhydride and the bulky base 2,6-di-tert-butylpyridine in dichloromethane (-78 ➔ 0 °C), but the reaction was complicated by the formation of decomposition products, and the Scheme XXII e=< TESCI, imidazole, 11 CH 2C1 2, -78 °C H 97% TlPSO.: 161 160 ~ Martin Sulfurane, II CH 2Cl2 , 23 °C 11 H 93% TIPSO.: 162 II Martin Sulfurane 259 yield of the olefin 162 was low (30-50%). Changing the base from 2,6-di-tert- butylpyridine to 2,6-dichloropyridine caused complete decomposition of the substrate, while substitution of the 2,6-di-tert-butylpyridine with 2-chloropyridine neither improved nor worsened the yield.98 The optimal set of conditions for dehydration of the C-1 alcohol was found to be use of the Martin sulfurane dehydrating reagent (5 equiv) in dichloromethane at 23 °C. 61 Under these conditions, the olefin 16 2 could be isolated in 93% yield. The double bond-containing product 162 was found to be considerably less stable than the corresponding saturated intermediates, darkening within minutes upon concentration. Despite this instability, the product 16 2 could be concentrated to neatness for brief periods, and was stable to storage at -20 °C in a frozen benzene matrix for several days. Continued exploration of conditions by which to effect the selective opening of the C-9 - C-10 epoxide of 162 began with a reexamination of the dicyclopentadienyl titanium(III) chloride reagent. 96 Reaction of the olefin-containing intermediate 162 with this reagent (3 equiv) in THF at 23 °C afforded the product 163, which resulted from opening of the C-4 - C-5 epoxide and concomitant cleavage of the ethylene carbonate. 0 HO o=<o•·· 11 11 H H ·,,OTES TlPSO.: 162 TlPSO.:' 163 It was anticipated that selective opening of the C-9 - C-10 epoxide could be carried out under conditions that favored the formation of the allylic cation spanning the region defined by C-12, C-1, and C-9. Acidic halohydrin-forming conditions were examined to carry out this transformation, with the expectation that the halogen would be reductively 260 removed at a later stage. Toward this end, the olefin 162 was treated with lithium iodide (16 equiv) and acetic acid (30 equiv) in TIIF at 0 °C. 100 Aside from unreacted 162 and material corresponding to the cleavage of the TES ether of 16 2, the signals for an additional product observed in the 1H NMR spectrum of the crude reaction mixture were consistent with an iodohydrin being formed at the C-4 - C-5 epoxide. The more strongly Lewis acidic conditions of magnesium iodide (10 equiv) in toluene starting at -78 °C and warming to 0 °C provided a highly unstable product in which the C-1 - C-12 olefin had reacted, although it appeared by 1H NMR analysis that the C-9 - C-10 epoxide was still intact. The 1H NMR spectrum of this new product was also indicative of C-4 - C-5 iodohydrin formation. A thorough study of the openmg of the C-9 - C-10 epoxide under ionic hydrogenation conditions was also conducted. 102 Exposure of the substrate 162 to triethylsilane (50 equiv) and various concentrations (0.04-1.8 M) of trifluoroacetic acid (1FA) in dichloromethane at either -78 °C or -40 °C followed by gradual warming generally resulted in loss of the C-8 TES group and no further reaction. Reaction of 16 2 with triethylsilane (50 equiv) and boron trifluoride etherate (25 equiv) in dichloromethane at 0 °C 103 produced a complex mixture of products, as did treatment of 162 with sodium cyanoborohydride (50 equiv) and boron trifluoride etherate (100 equiv) in TIIF at 0 °C. 104 . An additional strategy for the transformation of the epoxy alcohol to an allylic alcohol was the conversion of the alcohol to an iodide or a bromide and subsequent treatment with an alkyllithium to effect a reductive opening. Accordingly, the TES ether of intermediate 162 was cleaved with (±)-camphorsulfonic acid (5 equiv) in 2:1 acetonitrile/water at 23 °C to provide the alcohol 164 in 92% yield. Reaction of the alcohol 164 with the combination of triphenylphosphine (10 equiv), iodine (10 equiv), and imidazole (10 equiv) in dichloromethane at 23 °C25 resulted in the fonnation of a mixture of several unstable products, and attempted isolation of the major component by 261 0 0 o=( o=( 0'' O'" (±)-CSA, 2:1 acetonitrile/water, 23 °c H 11 II 92% TlPSO.: 162 chromatography on silica gel was not successful, likely due to its rapid decomposition. When the same reaction was carried out at a temperature of O°C and with a modification of the stoichiometry of the reagents (12 equiv PPh 3, 10 equiv 12 , 20 equiv imidazole), clean conversion to a single, slightly less polar, significantly more UV-active product was observed within 7-10 minutes. Again, difficulties were encountered in the attempted purification of the product, with the continued conversion of the single product to several new products by the time a silica gel column had been prepared. Finally, pre-packing of the column with silica and the eluant (20% ethyl acetate in hexanes) was followed by direct loading of the concentrated reaction mixture directly onto the column as soon as completion of the reaction was indicated by TLC. This practice allowed for isolation of the new, unstable product. Extensive 1H NMR analysis of the product, including a deuteriumexchange experiment (D20), indicated that the product was not the expected iodide, but in 0 0 0 o=< o=< o=< O''' O''' O'' 11 TESOTf, 2,6-lutidine, PPh3 , 12, imidazole, 11 H 11 CH 2Cl 2, o °C .o ~ ,: ,: TlPSO TlPSO 164 11 ,i OH 165 CH 2Cl2 , -78 °C TlPSO OTES 166 fact the epoxydienediyne 165. Further support for the assignment of structure 165 was gained by the reaction of the alcohol 165 with TESOTf (50 equiv based on 164) and 2,6- 262 lutidine (100 equiv based on 164) in dichloromethane at -78 °C77 to produce the silyl ether 166, which was found to be slightly more stable than 165 (stable at -20 °C in solid deuteriated benzene matrix for 12 hours) and also displayed more well resolved signals in the 1H NMR spectrum. The sharpness of these peaks allowed for a complete series of 1H NMR decoupling experiments and a comprehensive assignment of the signals. The preparation of the dienediyne 165 marked the first synthesis of the fully substituted epoxydienediyne core of neocarzinostatin chromophore, including substituents having the proper stereochemistry at the C-10 and C-11 positions. Having the model dienediyne 165 in hand, the goal now became the incorporation of the naphthoate ester at the C-11 position. Based on the instability of the dienediyne 165, the possibility of appending the ester at this stage or beyond was not considered. Instead, a naphthoate-containing epoxy alcohol in analogy to 164 was targeted as a substrate for the PPh/1/imidazole reaction. In order to arrive at this substrate as directly as possible, a four-step preparation from the epoxy alcohol 164 was developed. The C-8 alcohol of intermediate 164 was protected as a chloroacetate ester by reaction with chloroacetic anhydride (10 equiv) and pyridine (20 equiv) in dichloromethane at 0 °C, affording chloroacetate 167 in 81 % yield (Scheme XXIII). 105 The cleavage of the TIPS ether proved to be a difficult task, attributable to the instability of both the starting TIPS ether 167 and the product allylic alcohol 168. Initially, the best conditions were thought to be exposure of the substrate to a 6: 1 mixture of methanol and 1 N aqueous hydrochloric acid. The yield of allylic alcohol 168, however, was found to be highly variable under these conditions, due in part to concurrent cleavage of the chloroacetate ester. Cleaner conversion was observed when a 1:9 mixture the hydrofluoric acid-pyridine complex and acetonitrile at 23 °C was employed for this deprotection. Because of the instability of the alcohol 168, it was generally carried directly to the next reaction without storage. The coupling of the naphthoate ester was accomplished using the naphthoic acid 22 (6 equiv) and the coupling agent 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide 263 Scheme XXIII 0 0 o==< o==< 0''' O''' 11 II H (CICH2CO) 2O, Py, II II CH 2Cl 2, 0 °C ~,:~c, 81% 0 ,.: TIPSO.: o TIPSO 164 167 0 o=< O''' 9% (two steps) 168 0 0 o==< o==< o··· o•·· II 50'% 11 264 hydrochloride (EDC, 9 equiv) in dichloromethane at 23 °C. Due to the instability of the intermediate 168 and the inefficiency of the coupling, the product diester 169 could only be isolated in 9% overall yield from TIPS ether 16 7. It appeared that the allylie alcohol 168 was the most unstable compound in the series, as the esterification product 169 was found to be considerably more stable, and could be stored at -20 °C for several days without significant decomposition. The chloroacetate protecting group was removed by treatment of a solution of the diester 169 in toluene at 0 °C with saturated aqueous sodium bicarbonate in methanol at 0 °C to provide the targeted epoxy alcohol 120 in 50% yield. The epoxy alcohol 120 was also found to be remarkably stable, and could be stored in neat form (pale yellow film) for several weeks at -20 °C. Addition of a solution of the epoxy alcohol 120 in dichloromethane/acetonitrile (10:1) to a premixed suspension of triphenylphosphine (27 equiv), iodine (24 equiv), and imidazole (50 equiv) in dichloromethane at -15 °C produced the highly unstable neocarzinostatin chromophore aglycone (6). 25 This conversion was found to be highly dependent upon the initial mixing of the triphenylphosphine, iodine, and imidazole reagents, as evidenced by the failure of the reaction the first several times it was conducted. It was later determined that the color of the suspension formed upon the mixing of the reagents PPh3, lz, and imidazole was critical: the reaction failed when the initial suspension 0 o=< 0''' 11 11 Pf'ha, 12 , imidazole, CH2Cl 2, -15 °C II II 265 was white and was successful when the suspension was yellow. It is unclear as to what the nature of this difference was, but the reaction has never failed when starting with a yellow or pale orange suspension. It is also not known what the mechanism of the transformation of 120 to 6 is. The formation of an epoxy iodide intermediate followed by in situ reduction by iodide ion cannot be excluded, although no intermediate species were observed by thin-layer chromatographic monitoring of the reaction. Such nucleophilic conversions of epoxy iodides to allylic alcohols are known, but generally require more forcing conditions. 106 It is possible that in this system the strain imposed by the adjacent cyclopentene facilitated the conversion of 120 to 6. Characterization of the aglycone 6 proved to be quite challenging. The aglycone 6 is not a known degradation product of 1, and as a result, no authentic sample was available for comparison. Additionally, the aglycone 6 was found to be highly unstable, further complicating the structural proof. Although an NMR sample could be prepared from the chromatographic eluant without concentration to neatness, and good-quality 1H NMR spectra, complete with decoupling, could be obtained, the sample was found to decompose at a rate such that, after 8 hours at -20 °C, less than half of the aglycone 6 remained (1H NMR analysis). Such instability also precluded the accumulation of aglycone 6 through multiple reactions and rendered the acquisition of a 13C NMR spectrum implausible. A circular dichroism (CD) spectrum of 6 was obtained as a solution in acetonitrile, and displayed the same general characteristics as a CD spectrum of 1 obtained in 0.5 M acetic acid in methanol. The instability of 6 also precluded the procurement of its mass spectrum in isolation using the soft ionization techniques of FAB or electrospray. Anticipating that the structural components present in 6 were sufficient to bind to apo-NCS, the protein that imparts the stability necessary for 1 to exist in nature, efforts were directed toward obtaining a mass spectrum of 6 complexed to the apoprotein. Initial studies revealed that analysis of an aqueous solution of holo-NCS (pH 7) by electrospray MS provided peaks consistent with 266 the free apoprotein in the +6 and +7 charge states and a strong signal corresponding to free protonated 1 (mass 651). An FPLC-purified 107 and dialyzed sample of apo-NCS in aqueous solution (pH 7) also displayed peaks consistent with its +6 and +7 charge states. The molecular weight of apo-NCS was determined from the spectrum to be 11,095, fully consistent with the molecular weight expected as calculated from its amino acid sequence. Addition of a solution of 6 in acetonitrile to an aqueous solution of apo-NCS (pH 7) followed by electrospray mass spectral analysis of the mixture provided peaks consistent with the free apo-NCS in the+7 and +8 charge states, as well as the complex between apoNCS and 6 in the +7 and +8 charge states (Figure 3). 108 It should be noted that the spectra pH 7, 4 °C Holo-NCS Aglycone MW 11,595 Apo-NCS Electrospray MS MW 11,095 MW 500 Figure 3. Complexation of 6 with apo-NCS. for holo-NCS and the apo-NCS complex with 6 were obtained using different instruments. The analysis of 6 complexed with apo-NCS using the same instrument employed to obtain the spectrum of holo-NCS provided only peaks corresponding to apo-NCS. This result would appear to provide further support for the reduced stability of 6 relative to 1, as the conditions of this analysis were sufficient to decomplex both 1 and 6 from the apoprotein, and while 1 was able to survive the analysis, no peaks corresponding to 6 could be observed. The yield for the conversion of the epoxy alcohol 120 to 6 could be determined by UV spectroscopy, assuming an extinction coefficient of 7040 cm· 1 M· 1 at 302 nm, which 267 corresponds to the epoxydienediyne core of 1 as determined in these laboratories. 109 As the carbohydrate group of 1 is expected to contribute little to the UV activity of 1, it was anticipated that the extinction coefficients of 1 and 6 should be very similar. Samples were generally prepared for quantitation by the concentration of column fractions containing 6 to a volume of ca. 0.1 mL followed by dissolution of the concentrate into the appropriate amount of methanol. Precise dilutions were made in order to obtain an absorbance at 302 nm of less than one unit Further testimony to the instability of 6 may be gleaned from the information that the yields determined for the reaction producing 6 covered the full spectrum between 13% and 75%. Having completed the enantioselective synthesis and characterization of the aglycone 6 , the next task became the preparation of sufficient quantities of 6 for the investigation of the thiol addition chemistry and DNA cleavage activity of 6 in comparison to 1. As the synthetic sequence developed for the preparation of the direct precursor of 6, epoxy alcohol 120 , contained several poor-yielding steps, studies of the optimization of the route were initiated. The lowest-yielding series involved conversion of the chloroacetate 167 to the epoxy alcohol 120. These three steps were found to proceed in 4.5% overall yield at best. A significant portion of this low yield could be attributed to the instability of allylic alcohol 168, both in its preparation and in its further reaction with the naphthoic acid 22. It was expected that the introduction of the naphthoate ester prior to dehydration of the C-1 alcohol would circumvent this problem and perhaps provide more stable intermediates in the later stages of the synthesis. Implementation of the new synthetic strategy involved an· older intermediate: ninemembered ring alcohol 139. This alcohol was chosen with the expectation that, upon orthogonal protection of the C-8 alcohol, the C-10 TBS group could be removed under mild conditions to provide the free alcohol required for the incorporation of the naphthoate ester. One of the complications observed in the preparation of 139 from the epoxy aldehyde 138 using the standard conditions of excess LiN(TMS) 2 and LiCl in THF at -78 268 CC was the capricious formation of a cyclized product in which the C-8 alcohol had been converted to a TMS ether. The formation of this by-product was attributed to the requirement for excess LiN(TMS)2 in the ring-closure reaction. Upon aqueous work-up of the reaction mixture, neutralization of excess LiN(TMS)i generated hexamethyldisilazane, which in turn silylated the C-8 alcohol. Quenching of the excess base with pH 7 .2 phosphate buffer was of no assistance in alleviating this problem; however, substitution of LiN(TMS)2 with the bulkier base lithium diphenyltetramethyldisilazide not only suppressed side product formation, but also was more efficient, as only 2 equivalents of base were required for the reaction to proceed to completion, as opposed to 5 equivalents of LiN(TMS)2 (Scheme XXIV). 110 Treatment of alcohol 139 with chloroacetic anhydride (5 equiv) and pyridine (10 equiv) in dichlorornethane at O °C produced the chloroacetate ester Scheme XXIV H3CXO 11 TMSO,,,. .f TBSO 138 H Ai, ,CH 3 ,Si-CH 3 LiN, ,Sj-CH 3 A1 CH 3 ,LiCI, H3C 11 11 H .. , TBSO THF,-78 cc 139 79% 1. (CICH 2CO):p, Py, CH 2Cl 2, o cc, 89% 2. Et3N•3HF, CH 3CN, 23cC,83% 0''' II II H 0 ·,, ~ C I 0 0 -' HO 171 269 in 89% yield, 105 and subsequent exposure of the chloroacetate to triethylamine trihydrofluoride (5 equiv) in acetonitrile at 23 °C afforded chloroacetate diol 171 as a white foam in 83% yield. 32 The esterification of diol 171 with the naphthoate ester 22 (3 equiv) was carried out with DCC (5 equiv) in TI-IF at O °C. In situ cleavage of the chloroacetate was effected by addition of n-propylamine (10 equiv). Considerable effort was required for the optimization of this reaction, as the naphthoate ester 22 displayed a tendency to couple with itself at the naphthol position and even with the tertiary alcohol of 171 to form oligomeric products. A survey of conditions for the introduction of the ester group, including use of the pentafluorophenyl and 4-nitrophenyl activated esters of 22, mixed anhydrides of 22, and the coupling reagents EDC and DCC indicated that DCC was the most effective reagent for this reaction. Selection of TI-IF as the solvent for the DCC-mediated coupling proved to be critical; couplings carried out in either dichloromethane or DMF resulted in markedly diminished yields of ester 172. i. 22, DCC, THF, o c ii. n-PrNH2 0 11 11 H 71% HO.: 171 a" 0 H3CO~OH yv CH3 172 The acetonide of ester 172 was removed by exposure to 1% p-TsOH in methanol at 23 °C to provide the pentaol intermediate in 67% yield. 111 Introduction of the ethylene carbonate was accomplished with carbonyldiimidazole in THF, 53 and the intermediate carbonylimidazolides were hydrolyzed by treatment of the crude reaction mixture with (±)- 270 camphorsulfonic acid in 2: 1 acetonitrile/water at 23 °C to afford diol 17 4 in 67% yield. Unreacted starting pentaol (29%) could also be recovered from this reaction. 11 1. 1%p-TsOH/CH3OH, 11 H 23°C,67% 11 11 ··,oH o o.::· 0 2. i. CDI, THF, 0 ➔ 23 °C; ii. (±)-CSA, 2:1 CH 3 CN/H2O, H3CO~OH 23°C,67% yU 172 CH3 The C-8 alcohol and the hydroxyl group of the naphthoate ester of 17 4 were protected as triethylsilyl ethers by reaction with TESOTf (5 equiv) and 2,6-lutidine (12 equiv) in dichloromethane at -78 °C77 to provide the bis-silyl ether in 90% yield. The tertiary alcohol was cleanly dehydrated using the Martin sulfurane dehydrating agent (5 equiv) in dichloromethane at 23 °C, 61 affording the olefinic product in 79% yield. The triethylsilyl ethers were then cleaved by treatment with triethylamine trihydrofluoride (5 equiv) in THF at O°C32 to produce the epoxy alcohol 120 in quantitative yield. Application of this improved sequence for the preparation of the epoxy alcohol 120 provided a several- 1. TESOTf, 2,6-lutidine, 11 11 CH 2C'2, -78 °C, 90% 2. Martin Sulfurane, CH 2Cl 2 , 23°c, 79% II 11 271 fold increase in the amount of this intermediate that could be amassed relative to the pathway summarized in Scheme XX:ill. The revised synthetic pathway should supply the necessary quantities of intermediates for the ongoing studies directed toward the completion of the total synthesis of neocarzinostatin chromophore (1), as well as the synthesis of analogs bearing modified sugar residues. 112 272 Experimental Section General procedures. All reactions were performed in flame-dried round bottom or modified Schlenk (Kjeldahl shape) flasks. The flasks were fitted with rubber septa and contained a positive pressure of argon unless otherwise stated. Stainless steel syringes or cannula were used to transfer air- and moisture-sensitive materials. Concentration in vacuo was accomplished by rotary evaporation at water aspirator pressure (approximately 25 torr). Flash chromatography was carried out as described by Still et al., employing 230400 mesh silica gel. 29 Analytical thin-layer chromatography was performed using glass plates pre-coated with 0.25 mm 230-400 mesh silica gel impregnated with fluorescent indicator (254 nm). Thin-layer chromatography plates were visualized by exposure to ultraviolet light (noted as 'UV') and/or by exposure to an acidic solution of p-anisaldehyde (noted as 'anisaldehyde') or ethanolic eerie ammonium molybdate (noted as 'CAM'), followed by heating on a hot plate. Materials. exceptions. benzophenone Commercial reagents were used as received, with the following Ethyl ether and tetrahydrofuran (THF) were distilled from sodium ketyl. Dichloromethane, benzene, toluene, acetonitrile, N,N- diisopropylethylamine, hexamethyldisilazane, 2,6-lutidine, pyridine, and triethylamine were distilled from calcium hydride at 760 torr. Diphenyltetramethyldisilazane was distilled from calcium hydride at 0.1 torr, and was stored under an atmosphere of argon. Acetic 273 acid was distilled from chromium trioxide at 760 torr and was stored over 4 A molecular sieves. Methanesulfonyl chloride was distilled from phosphorous pentoxide at 760 torr. Trifluoromethanesulfonic anhydride and trimethylsilyl trifluoromethanesulfonate were stored in a glove box in round bottom flasks fitted with polycarbonate or glass stoppers. The molarity of n-butyllithium solutions was determined by titration with 2,6-di-tert-butyJ:. 4-methylphenol using fluorene as an indicator (average of three determinations). Anhydrous lithium chloride was prepared by heating at 100 °C at 1 torr for 24 h. Fresh solutions of lithium hexamethyldisilazide were prepared by the addition of a solution of nbutyllithium ( 1.0 eq) in hexanes to a solution of hexamethyldisilazane ( 1.0 eq) in hexanes at -20 ·c, followed by warming to room temperature. Fresh solutions of lithium diphenyltetramethyldisilazide were prepared by the addition of a solution of n-butyllithium (1.0 eq) in hexanes to a solution of hexamethyldisilazane (1.0 eq) in tetrahydrofuran at -20 ·c, followed by warming to room temperature. Instrumentation. Infrared (IR) spectra were obtained using a Perkin-Elmer 1600 FT-IR spectrophotometer referenced to a polystyrene standard. Data are presented as follows: frequency of absorption (cm·1), intensity of absorption (v =very, s = strong, m = medium, w = weak) and assignment where appropriate. Proton nuclear magnetic resonance (1H NMR) spectra and carbon nuclear magnetic resonance (13C NMR) spectra were recorded on either a General Electric QE-300 (300 MHz) or a JEOL GX-400 (400 MHz) NMR spectrometer; chemical shifts for protons are reported in parts per million downfield from tetramethylsilane and are referenced to residual protium in the NMR solvent (C 6D 5H: <5 7.20, CDHC12: <5 5.29, CD 2HCN: <5 1.93, SO(CD 3)(CD2H): <5 2.49). Data are represented as follows: chemical shift, multiplicity (br = broad, s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, complex = multiple resonances, app. = apparent, abq =ab quartet), integration, coupling constant in Hertz (Hz), and assignment FPLC was conducted on a Beckman System Gold HPLC equipped with a Pharmacia Mono-Q HR 5/5 anion exchange FPLC column and a Beckman 168 Programmable 274 Photodiode Detector set at 280 run. Optical rotations were detennined on a Jasco DIP-181 digital polarimeter equipped with a sodium lamp source. Circular dichroism spectra were obtained on a Jasco J-600 spectrophotometer using a solution cell with a path length of 1 cm. High resolution mass spectra were obtained either at the University of California, Riverside Mass Spectrometry Facility; the Midwest Center for Mass Spectroscopy, Lincoln, Nebraska; the University of California, Los Angeles Mass Spectrometry Facility; orthe California Institute of Technology Mass Spectrometry Facility. Electrospray mass spectra were obtained at Beckman Research Institute of the City of Hope, Duarte, California, on a Finnigan LCQ ion trap mass spectrometer equipped with a Finnigan-MAT electrospray ion source modified for microspray as previously described.108 275 II II TESOTf, 2,6-lutidine, 11 CH 2Cl2, -78 °C 99% 12 TBSO~- TBSO~ 68 11 ,o 121 Tris-silyl ether 12 1 2,6-Lutidine (205 µL, 189 mg, 1.76 mmol, 10 equiv) and triethylsilyl trifluoromethanesulfonate (239 µL, 280 mg, 1.06 mmol, 6 equiv) were added sequentially to a solution of alcohol 68 (84.0 mg, 0.176 mmol, 1 equiv) in dichloromethane (9 mL) at -78 °C. The resultant yellow solution was maintained at -78 °C for 20 min, then excess triethylsilyl trifluoromethanesulfonate was quenched by the addition of triethylamine and methanol (0.5 mL each). The reaction mixture was partitioned between hexanes (20 mL) and water (20 mL). The layers were separated and the aqueous layer was further extracted with hexanes (2 x 20 mL). The combined organics were washed once with brine (25 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column \ chromatography (20% ethyl acetate in hexanes) provided tris-silyl ether 121 (109 mg, 99%) as a pale yellow oil. 276 6.22 (t, lH, J = 1.84 Hz, ClO H), 5.71 (t, lH, J = 1.44 Hz, C8 H), 4.82 (m, lH, C11 H), 3.91 (dd, lH, J = 8.40, 5.84 Hz, C13 H), 3.75 (dd, lH, J = 8.80, 6.60 Hz, C14 H), 3.59 (t, lH, J = 6.24 Hz, C14 H), 3.11 (s, lH, C5 H), 3.08 (dd, lH, J = 13.20, 6.96 Hz, C12 PH), 2.34 (dd, lH, J = 12.80, 5.88 Hz, C12 aH), 1.51 (s, 3H, C(CH 3 )i), 1.23 (s, 3H, C(CH3 )i), 1.09 (m, 9H, OSi(CH 2CH3) 3), 0.95 (s, 9H, OSiC(CH 3) 3(CH 3) 2), 0.73 (m, 2H, OSi(CH 2CH 3\), 0.61 (m, 4H, OSi(CH 2CH 3\), 0.37 (s, 9H, OSi(CH 3)3), 0.046 (s, 3H, OSiC(CH 3)iCH 3) 2), 0.032 (s, 3H, OSiC(CH 3)iCH 3) 2 ). FTIR (thin film), cm· 1: 2955 (m), 2878 (m), 1461 (w), 1372 (w), 1252 (m), 1075 (m), 1005 (m), 844 (m), 741 (m). 1LC (25% EtOAc in Hexanes), Rf 68: 0.46 (anisaldehyde) 121: 0.71 (anisaldehyde) 277 11 11 CF3CO3H, K.!HPO4 , II CH 2 Cl 2, 0 °C 11 12 TBSO.:" TBSO.: 121 10 122 Bis-epoxide 12 2 .. Peroxytrifluoroacetic acid (3 drops from a Pasteur pipet of a solution prepared in situ by dropwise addition of trifluoroacetic anhydride (2.12 mL, 3.15 g, 15.0 mmol, 1.2 equiv relative to H2O2) to a solution of hydrogen peroxide (340 µL of a 90% solution, 12.5 mmol, 1 equiv) in dichloromethane (2.5 mL)) was added to a solution of tris-silyl ether 121 (5.0 mg, 8.1 x 10·3 mmol, 1 equiv) and anhydrous K 2HPO 4 (28 mg, 0.16 mmol, 20 equiv) in dichloromethane (100 µL) at 0 0 C. The yellow solution was maintained at 0 °C for an additional 5 min, then diluted with 1:1 ethyl acetate/hexanes (2 mL). The solution was washed with water (3 x 1 mL) and brine (1 mL), dried over sodium sulfate and concentrated to approximately 0.1 mL. The concentrated sample was applied to a flash chromatography column loaded with 10% ethyl acetate in hexanes, and the product was eluted with a solvent system of 10% ethyl acetate in hexanes grading to 20% ethyl acetate in hexanes. Fractions containing the product were pooled and concentrated to a volume of ca. 0.1 mL. A 0.5 mL portion of deuteriated benzene (99.5 atom % D) was added and the resulting solution was concentrated to a volume of ca. 0.1 mL. repeated 4 times. This procedure was After the last iteration, the concentrated solution was taken up in 278 approximately 0.4 mL deuteriated benrene (99.95 atom % D). Analysis of the sample by 1 H NMR showed it to contain a small amount (not quantitated) of bis-epoxide 122. 5.17 (s, lH, C8 H), 4.29 (t, lH, J = 7.32 Hz, C11 H), 4.03 (dd, lH, J = 9.16, 5.12 Hz, C13 H), 3.86 (s, lH, ClO H), 3.80 (dd, lH, J = 8.76, 6.60 Hz, Cl4 H), 3.44 (dd, lH, J = 6.60, 5.12 Hz, Cl4 H), 3.15 (s, lH, C5 H), 2.24 (dd, lH, J = 11.36, 6.60 Hz, Cl2 H), 1.94 (dd, lH, J = 12.08, 9.12 Hz, C12 H), 1.58 (s, 3H, C(CH 3 ) 2), 1.27 (s, 3H, C(CH 3)2), 1.08 (t, 9H, J = 8.08 Hz, OSi(CH 2CH 3) 3), (s, 0.91 9H, OSiC(CH 3) 3(CH 3) 2), 0.67 (q, 6H, J = 7.72 Hz, OSi(CH 2CH 3) 3), OSi(CH 3)3), 0.44 -0.014 OSiC(CH 3)/CH 3) 2), -0.026 OSiC(CH 3)/CH 3) 2). 1LC (25% EtOAc in Hexanes), Rf 121: 0.59 (anisaldehyde) 122: 0.41 (anisaldehyde) (s, (s, 9H, 3H, (s, 3H, 279 II 11 11 (+)-DET, Ti(Oi-Pr) 4 , 11 TBHP,4AMS, 0 OH 12 <f° 0 H3COW8" "'-::: OMEM • ~ Ill 4• CH3 123 Epoxy alcohol 1 2 3 A suspension of 4A molecular sieves (approx. 0.lg, powdered, activated) in dichloromethane (0.7 mL) was cooled to -20 °C. (+)-Diethyl-L-tartrate (30 µL, 37 mg, 0.17 mmol, 12 equiv) and titanium isopropoxide (43 µL, 41 mg, 0.14 mmol, 10 equiv) were added sequentially via syringe. The mixture was allowed to stir at -20 °C for an additional 15 min, and alcohol 114 (10 mg, 0.014 mmol, 1 equiv) in dichloromethane (0.3 mL) was added via cannula. The resultant mixture was stirred at -20 °C for another 30 min, then tert-butyl hydroperoxide (15 µL of a 4.7 M solution in dichloromethane, 0.0722 mmol, 5 equiv) was added with a Teflon needle through a slit in the septum at the neck of the flask. The reaction was maintained at -20 °C for 11 h, then the catalyst was quenched with 10% aqueous D-tartaric acid (5 mL) and stirred vigorously for 30 min. The layers were separated, and the aqueous layer was further extracted with dichloromethane (3 2-mL portions). The combined organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (5% ethyl acetate in dichloromethane grading to 10% ethyl acetate in dichloromethane) was followed by pooling 280 fractions containing the product and concentration to ca. 0.1 mL. A 0.5 mL portion of deuteriated benzene (99 .5 atom % D) was added, and the resultant solution was concentrated to a volume of ca. 0.1 mL. This procedure was repeated 4 times. After the final concentration, the concentrate was taken up in ca. 0.4 mL deuteriated benzene (99 .95 atom% D) and analyzed by 1H NMR to confirm the formation of epoxy alcohol 123. 7.63 (d, lH, J = 9.16 Hz, C4" H), 7.36 (d, IH, J = 2.20 Hz, C8" H), 7.20 (d, IH, J = 9.16 Hz, C3" H), 6.96 (br s, lH, C6" H), 5.85 (d, lH, J =5.48 Hz, Cll H), 5.21 (abq, 2H, llv = 53.08 Hz, J = 6.96 Hz, OCH 2 OCH 2CH2 OCH 3), 4.89 (d, IH, J = 6.5 Hz, C8 H), 4.25 (s, lH, CIO H), 3.93-3.24 (complex, 7 H, OCH 2 OCH 2CH2 OCH 3, C13, C14 H), 3.53 (s, 3H, CT' OCH 3), 3.13 (d, lH, J = 16.12 Hz, C12 aH), 3.06 (s, 3H, OCH 2OCH 2CH 2 OCH 3), 2.79 (s, lH, C5 H), 2.48 (dd, lH, J = 16.12, 5.48 Hz, C12 PH), 2.36 (d, IH, J = 6.56 Hz, C8 OH), 2.23 (s, 3H, C5" CH 3), 1.47 (s, 3H, C(CH 3)2), 1.34 (s, 3H, C(CH 3) 2 ), 0.25 (s, 9H, OSi(CH 3) 3). 281 FI1R (thin film), cm- 1: 3401 (m, OH), 3283 (m, OH), 2923 (s), 1828 (m), 1724 (s, ester C=O), 1622 (m), 1466 (m), 1255 (vs), 1159 (m), 1083 (s), 1035 (s), 842 (m) HRMS (FAB): Calc'd for C37H440 12Si [Mr: 708.260216 Found: 708.264496 1LC (30% EtOAc/30% Hexanes/40% CH 2C½), Rf: 114: 0.32 (fluoresces under UV, anisaldehyde) 123: 0.41 (fluoresces under UV, anisaldeh yde) 282 0 &CH(OCH 3)i 30% Hp sat'd K C0 , 2 2 , 3 CH 30H, O °C TBSO,.: 91% (+)-21 125 Epoxy ketone 1 2 5 A solution of enone ( + )-21 (275 mg, 0.960 mmol, 1.0 equiv) in methanol (1.60 mL) was cooled to 0 0 C. Hydrogen peroxide ~205 µL of a 30% solution, 1.92 mmol, 2 equiv) was added via syringe, followed by dropwise addition of saturated aqueous potassium carbonate (110 µL). The reaction mixture was maintained at 0 °C for an additional 30 min, then diluted with H2O (10 mL). The solution was extracted with three 25-mL portions of ethyl acetate and the combined organics were washed once with brine (25 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (50% ethyl acetate in hexanes) afforded epoxy ketone 125 (263 mg, 91 %) as a colorless oil. 283 4.98 (s, lH, CH(OCH3 ) 2), 4.14 (d, lH, J = 5.48 Hz, C4 H), 4.13 (s, lH, C3 H), 3.23 (s, 3H, CH(OCH3)2), 3.20 (s, 3H, CH(OCH3)2), 2.44 (dd, lH, J = 18.30, 5.49 Hz, C5 ~H), 1.98 (d, lH, J = 18.30 Hz, C5 aH), 0.81 (s, 9H, OSiC(CH 3MCH3) 2), -0.11 OSiC(CH 3)/CH 3}i), -0.14 (s, (s, 3H, 3H, OSiC(CH 3)/CH 3\). FTIR (thin film), cm· 1: 2954 (s), 2858 (s), 1753 (s, C=O), 1469 (m), 1369 (m), 1085 (s), 837 (s). TLC (50% EtOAc in Hexanes s), Rf. (+)-21: 0.63 (anisaldehyde) 125: 0.70 (anisaldehyde) 284 i. LiN(TMSh, THF, -78 "C ii. 125 40% H3CXO H3C H3CXO 14 0''' H3C 0"' II i TBS 11 i HO,,.. .,,CH(OCH 3h 0 12 TBSO.: 10 126a 12 ~ TBSO (ca.2:1) TBS 10 126b (arbitrary stereochemistry at C-1) Diepoxydiynes 126a and 126b Lithium hexamethyldisilazide (258 µL of a 1.0 M solution in hexanes, 0.258 mmol, 3.0 equiv) was added dropwise over a two minute period to a solution of epoxydiyne 2 0 (79 mg, 0.26 mmol, 3.0 equiv) in toluene (2.0 mL) at -78 °C. The resultant pale yellow solution was stirred at -78 °C for an additional 20 min, and epoxy ketone 125 (26 mg, 0.086 mmol, 1.0 equiv) in toluene (150 µL) was added dropwise via cannula over a four minute period. The reaction mixture was maintained at -78 °C for another 90 min, then excess base was quenched by the addition of saturated aqueous ammonium chloride. The reaction was allowed to warm to 23 °C and was extracted with 1: 1 ethyl acetate/hexanes (3 15-mL portions). The combined organics were washed with brine (20 mL), dried over 285 sodium sulfate and concentrated. Purification of the residue by flash column chromatography (5% ethyl acetate in dichloromethane) provided diastereomers 126a (14 mg, 27%) and 126b (7 mg, 13%), each as colorless oils. For 126a: 5.27 (s, IH, CH(OCH3)2), 4.21 (m, 2H, Cl I H, C13 H), 3.95 (dd, IH, J = 8.80, 6.60 Hz, C14 H), 3.85 (s, IH, CI0 H), 3.77 (t, IH, J = 6.56 Hz, C14 H), 3.72 (s, IH, OH), 3.62 (s, IH, C5 H), 3.37 (s, 3H, CH(OCH3)2), 3.22 2.39 (dd, IH, J = (s, 3H, CH(OCH 3) 2), 14.28, 5.12 Hz, C12 ~H), 2.19 (d, IH, J = 14.28 Hz, C12 aH), 1.48 (s, 3H, C(CH 3) 2), 1.21 (s, 3H, C(CH 3)2), 1.07 (s, 9H, SiC(CH 3\(CH 3)i), 0.90 (s, 9H, SiC(CH 3)/CH 3) 2), 0.23 (s, 6H, SiC(CH 3)iCH 3)2), ---0.025 (s, 3H, SiC(CH 3)iCH 3)2), ---0.049 (s, 3H, SiC(CH 3)iCH 3)2). 20: 0.64 (anisaldehyde) 125: 0.52 (anisaldehyde) 126a: 0.25 (anisaldehyde) 286 For 126b: 5.78 (s, lH, CH(OCH3)2), 4.21 (d, lH, J = 4.40 Hz, C11 H), 4.13 (dd, lH, J = 8.80, 5.84 Hz, C13 H), 3.95 (dd, lH, J = 8.76, 6.60 Hz, C14 H), 3.80 (t, lH, J = 5.84 Hz, C14 H), 3.56 (s, lH, ClO H), 3.53 (s, lH, C5 H), 3.41 (s, lH, OH), 3.37 (s, 3H, CH(OCH3) 2 ), 3.32 (s, 3H, CH(OCH3)z), 2.37 (m, 2H, C12 H), 1.46 (s, 3H, C(CH 3)2), 1.21 (s, 3H, C(CH 3)2), 1.07 (s, 9H, SiC(CH 3)iCH 3) 2)), 0.97 (s, 9H, OSiC(CH 3)iCH 3) 2), 0.23 (s, 3H, OSiC(CH 3\(CH 3) 2), 0.22 (s, 3H, OSiC(CH 3)iCH 3) 2), 0.058 (s, 3H, OSiC(CH 3) 3(CH 3) 2), 0.011 (s, 3H, OSiC(CH 3)iCH 3) 2). 20: 0.64 (anisaldehyde) 125: 0.52 (anisaldehyde) 126b: 0.18 (anisaldehyde) 287 II HO,,,. i ~TsOH, acetone, 23 TBS °c 11 HO,,,. 75% TBS CHO 12 .:· TBSO 46 i1 10 127 Aldehyde 12 7 p-Toluenesulfonic acid (4.0 mg, 0.021 mmol, 0.2 equiv) was added in one portion to a solution of dimethyl acetal 46 (63 mg, 0.11 mmol, I equiv) in acetone (1.5 mL). The yellow solution was stirred at 23 °C for 10 min, and excess p-toluenesulfonic acid was neutralized by addition of saturated sodium bicarbonate (1 mL). The cloudy mixture was extracted with 1:1 ethyl acetate/hexanes (3 x 5 mL), and the combined organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (5% ethyl acetate in dichloromethane) afforded aldehyde 127 (44 mg, 75%) as a pale yellow oil. 288 9.33 (s, lH, CHO), 6.09 (d, lH, J = l.8 Hz, ClO H), 4.81 (td, lH, J = 6.92, 1.80 Hz, C11 H), 4.10 (dd, lH, J = 8.80, 5.84 Hz, C13 H), 3.87 (m, 2H, C14 H and OH), 3.61 (t, lH, J = 6.20 Hz, C14 H), 3.49 (s, lH, C5 H), 3.10 (dd, lH, J = 12.80, 6.92 Hz, C12 H), 2.40 (dd, lH, J = 12.80, 6.56 Hz, C12 H), 1.42 (s, 3H, C(CH3\), 1.18 (s, 3H, C(CH 3)2), 1.07 (s, 9H, SiC(CH3MCH 3\), 0.95 (s, 9H, SiC(CH 3)iCH 3) 2), 0.23 (s, 3H, SiC(CH 3)iCH 3)i), 0.22 (s, 3H, SiC(CH 3\(CH 3) 2), 0.038 (s, 3H, SiC(CH 3)iCH 3) 2), 0.015 (s, 3H, SiC(CH 3)iCH 3)i). 46: 0.29 (anisaldehyde) 127: 0.51 (UV, anisaldehyde) 289 II HO,,,. i H ,>TsOH, acetone, 23 "C 7'i1'/o Aldehyde 12 8 p-Toluenesulfonic acid (110 mg) was added in one portion to a solution of dimethyl acetal 48 (390 mg, 0.674 mmol, 1 equiv) in acetone (20 mL) at 23 °C. The reaction was maintained at 23 °C for 55 min, then poured into saturated aqueous sodium bicarbonate (40 mL). The mixture was extracted with 1:1 ethyl acetate/hexanes (3 25-mL portions), and the combined organics were washed with saturated aqueous sodium chloride (35 mL), dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (30% ethyl acetate in hexanes) to afford the aldehyde 128 (285 mg, 79%) as a pale yellow oil. 290 12.72 (s, lH, C2" OH), 9.24 (s, lH, C8 H), 8.13 (d, lH, J = 2.0 Hz, C8" H), 7.71 (d, lH, J = 9.18 Hz, C4" H), 7.18 (d, lH, J = 9.46 Hz, C3" H), 6.98 (m, lH, C6" H), 6.07 (t, lH, J = 2.2 Hz, ClO H), 5.71 (m, lH, Cl 1 H), 4.12 (dd, lH, J = 8.15, 5.14 Hz, C13 H), 3.84 (m, lH, C14 H), 3.66 (s, 3H, CT' OCH 3), 3.38 (d, lH, J = 1.03 Hz, C5 H), 2.98 (dd, lH, J = 14.03, 7.42 Hz, C12 ~H), 2.46 (dd, lH, J = 14.09, 5.28 Hz, C12 aH), 2.24 (s, 3H, C5" CH 3), 2.20 (d, lH, J = 1.11 Hz, C7 H), 1.47 (s, 3H, C(CH 3)2), 1.21 (s, 3H, C(CH 3)2). 48: 0.46 (fluoresces under UV, anisaldehyde) 128: 0.37 (fluoresces under UV, anisaldehyde) 291 II HO,,.. ~ TESOT!, 2,6-lutidine, H CH 2Cl2, -78 °C CHO 85% TESO,,.. H 12 CHO TBSO.:" 66 129 TES ether 1 2 9 2,6-Lutidine (0.471 mL, 434 mg, 4.04 mmol, 10 equiv) and triethylsilyl trifluoromethanesulfonate (0.549 mL, 642 mg, 2.43 mmol, 6 equiv) were added sequentially to a solution of enal 66 (175 mg, 0.404 mmol, 1 equiv) in dichloromethane (15 mL) at -78 cc. The reaction mixture was maintained at -78 °C for an additional 50 min, and triethylamine (1 mL) and methanol (1 mL) were added. The mixture was warmed to 23 cc, diluted with 1:1 ethyl acetate in hexanes (30 mL), and washed with water (15 mL) and saturated aqueous sodium chloride (15 mL). The organics were dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (10% ethyl acetate in hexanes) to provide the TES ether 129 (188 mg, 85%) as a pale yellow oil. 292 9.82 (s, lH, CHO), 6.39 (d, lH, J = 1.84 Hz, ClO H), 4.75 (td, lH, J =6.60, 1.84 Hz, Cl 1 H), 4.11 (dd, lH, J = 8.80, 5.88 Hz, C13 H), 3.94 (m, lH, C14 H), 3.63 (t, lH, J = 6.20 Hz, C14 H), 3.34 (d, lH, J = 1.44 Hz, C5 H), 3.18 (dd, lH, J = 12.80, 6.96 Hz, C12 H), 2.38 (dd, lH, J = 12.80, 6.24 Hz, C12 H), 2.11 (s, lH, J = 1.84 Hz, C7 H), 1.43 (s, 3H, C(CH 3)i}, 1.18 (s, 3H, C(CH 3)2), 1.12 (t, 9H, J = 7.68 Hz, OSi(CH2CH 3) 3), 0.98 (m, 2H, OSi(CH 2CH 3) 3), OSiC(CH 3)iCH 3)i}, 0.94 0.86 (s, 9H, (m, 2H, OSi(CH 2CH 3) 3), 0.53 (q, 2H, J = 8.08 Hz, OSi(CH 2CH 3) 3), OSiC(CH 3)iCH 3) 2), 0.016 0.012 (s, 3H, (s, 3H, OSiC(CH 3)iCH 3) 2) . FI1R (thin film), cm· 1: 3277 (w, C=C-H), 2955 (s), 1699 (s, C=O), 1463 (w), 1256 (m), 1079 (s), 838 (s). 1LC (25% EtOAc in Hexanes), Rf 66: 0.26 (UV, anisaldehyde) 129: 0.62 (UV, anisaldehyde) 293 11 TESO,,.. H CHO DIBAL, PhCH3, -78°C 81% TBSO.: 129 II ~ 1 H TESO,,.. 12 ,i TBSO 10 130 Allylic alcohol 13 Q Diisobutylaluminum hydride (170 µL of a 1.5 M solution in toluene, 0.255 mmol, 1.1 equiv) was added dropwise via syringe to a solution of aldehyde 129 (127 mg, 0.232 mmol, 1 equiv) in toluene (5 mL) at-78 °C. The reaction was maintained at -78 °C for an additional 10 min, then excess reducing agent was quenched by the addition of methanol (1 mL). The reaction mixture was then warmed to 0 °C, and a 10% aqueous solution of potassium sodium tartrate (5 mL) was added. The mixture was warmed to 23 °C and stirred vigorously for 20 min. The reaction mixture was poured into water (20 mL) and extracted with ethyl acetate (3 x 15 mL). The combined organics were washed with IN HCl (10 mL), water (10 mL), and saturated aqueous sodium chloride (10 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (20% ethyl acetate in hexanes) provided allylic alcohol 130 (103 mg, 81 %) as a colorless oil. 294 5.84 (d, lH, J = 1.48 Hz, ClO H), 4.90 (m, lH, Cl 1 H), 4.54 (abq, 2H, J = 14.64, f:r.v = 23.04 Hz, C8 CH 2), 4.04 (dd, lH, J = 8.76, 5.84 Hz, C13 H), 3.80 (dd, 1 H, J = 8.40, 6.60 Hz, C14 H), 3.51 (t, lH, J = 5.88 Hz, C14 H), 3.22 (d, lH, J = 1.84 Hz, C5 H), 3.19 (dd, lH, J = 12.44, 6.96 Hz, C12 H), 2.38 (dd, lH, J = 12.44, 6.24 Hz, C12 H), 2.08 (d, lH, J = 1.84 Hz, C7 H), 1.47 (s, 3H, C(CH 3)2), 1.18 (s, 3H, C(CH 3) 2), 1.09 (t, 9H, J = 7.68 Hz, OSi(CH2CH 3) 3), 1.00 (s, 9H, OSiC(CH 3MCH 3) 2 ), OSi(CH 2CH 3 ) 3), OSiC(CH 3)iCH 3)i), 0.84 0.10 0.09 (m, 6H, (s, 3H, (s, 3H, OSiC(CH 3)/CH 3) 2). FTIR (thin film), cm- 1: 3448 (m, OH), 3309 (m, C=C-H), 2955 (s), 2878 (s), 1461 (m), 1075 (vs), 837 (s). TLC (50% EtOAc in Hexanes), Rf. 129: 0.68 (UV, anisaldehyde) 130: 0.59 (anisaldehyde) 295 II TESO,,,. iH CH 2OH II (+)-DET, Ti(Oi-Pr) 4 , TBHP, 4A MS, CH2Cl 2 , -20 °C H 12 .,,CH20H 0 88% 130 i1 TESO,,,. 131 Bisepoxide 131 A suspension of 4A molecular sieves (approx. lg, powdered, activated) in dichloromethane (7.0 mL) was cooled to-20 °C. (+)-Diethyl-L-tartrate (262 µL, 316 mg, 1.53 mmol, 6 equiv) and titanium isopropoxide (380 µL, 363 mg, 1.28 mmol, 5 equiv) were added sequentially via syringe. The mixture was allowed to stir at -20 °C for an additional IS min, then alcohol 130 (140 mg, 0.255 mmol, 1 equiv) in dichloromethane (5 mL) was added via cannula. The resultant mixture was stirred at -20 °C for another 30 min, then tert-butyl hydroperoxide (271 µL of a 4.7 M solution in dichloromethane, 1.28 mmol, 5 equiv) was added through a slit in the septum at the neck of the flask via a gaslight syringe equipped with a Teflon needle. The reaction was maintained at -20 °C for 20 h, and the catalyst was quenched with 10% aqueous D-tartaric acid (5 mL) and stirred vigorously for 30 min. The layers were separated and the aqueous layer was further extracted with dichloromethane (2 10-mL portions). The combined organics were dried over sodium sulfate and were concentrated. Purification of the residue by flash column chromatography (5% ethyl acetate in dichloromethane grading to 10% ethyl acetate in dichloromethane) afforded the bisepoxide 131 (127 mg, 88%) as a colorless oil. 296 4.38 (d, 2H, J = 5.06 Hz, C8 H), 4.30 (d, lH, J = 6.10 Hz, Cll H), 4.10 (dd, lH, J = 8.73, 5.75 Hz, C13 H), 3.87 (dd, 1 H, J = 8.73, 6.93 Hz, C14 H), 3.64 (t, lH, J = 5.88 Hz, C14 H), 3.62 (s, lH, ClO H), 3.33 (d, lH, J = 1.58 Hz, CS H), 2.50 (dd, lH, J = 14.56, 6.04 Hz, C12 ~H), 2.13 (d, lH, J = 14.00 Hz, C12 aH), 2.10 (d, lH, J = 1.60 Hz, C7 H), 1.92 (t, lH, J = 5.23 Hz, OH), 1.49 (s, 3H, C(CH 3) 2), 1.19 (s, 3H, C(CH 3)2), 1.12 (t, 9H, J = 1.59 Hz, OSi(CH2CH 3) 3), 0.94 (s, 9H, OSiC(CH 3MCH 3) 2), OSi(CH 2CH 3) 3), 0.11 0.91 (s, (m, 6H, 6H, OSiC(CH 3)/CH 3) 2). FTIR (thin film), cm· 1: 3448 (m, OH), 3271 (m, C=C-H), 2954 (s), 1454 (m), 1373 (m), 1256 (m), 1134 (s), 1075 (m), 839 (m). 130: 0.54 (anisaldehyde) 131: 0.47 (anisaldehyde) 297 II TESO,,,. i (COCl) 2, DMSO, Et3N, H CH2Cl2, -78 ➔ O °C i1 11 H .,,CHO 0 TESO,,.. 12 86% ,: TBSO TBSO 131 10 132 Epoxy aldehyde 13 2 Dimethylsulfoxide (247 µL, 272 mg, 3.48 mmol, 15 equiv) was added dropwise to a solution of oxalyl chloride (203 µL, 295 mg, 2.32 mol, 10 equiv) in dichloromethane (4.5 mL) at-78 °C. The resultant solution was maintained at-78 °C for 15 min, and epoxy alcohol 131 (127 mg, 0.225 mmol, 1 equiv) in dichloromethane (4.5 mL) was added in a dropwise manner. The solution was then warmed to -40 °C and was held at this temperature for 20 min. The reaction mixture was then cooled to -78 °C, triethylamine (971 µL, 705 mg, 6.96 mmol, 30 eq) was added, and the solution was stirred at 0 °C for 40 min. The reaction mixture was diluted with pH 7.2 phosphate buffer (10 mL) and extracted with dichloromethane (2 x 10 mL). The combined organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (10% ethyl acetate in hexanes) provided epoxy aldehyde 132 (109 mg, 86%) as a pale yellow oil. 298 10.02 (s, lH, CHO), 4.14 (d, lH, J = 6.24 Hz, Cll H), 4.05 (dd, lH, J = 8.44, 5.88 Hz, C13 H), 3.86 (dd, 1 H, J = 8.80, 6.56 Hz, C14 H), 3.68 (s, lH, ClO H), 3.61 (t, lH, J = 6.24 Hz, C14 H), 3.31 (d, lH, J = 1.48 Hz, CS H), 2.37 (dd, lH, J = 14.64, 5.88 Hz, C12 ~H), 2.12 (d, lH, J = 14.64 Hz, C12 cxH), 2.12 (d, lH, J = l.60 Hz, C7 H), 1.46 (s, 3H, C(CH 3)i), 1.18 (s, 3H, C(CH 3) 2), 1.13 (t, 9H, J = 7.72 Hz, OSi(CH 2CH 3) 3), 0.93 (m, 6H, OSi(CH 2CH 3) 3), 0.89 (s, 9H, OSiC(CH 3)/CH 3) 2), -0.046 (s, 3H, OSiC(CH 3)/CH 3) 2), -0.059 (s, 3H, OSiC(CH 3)/CH 3) 2). FTIR (thin film), cm· 1: 3301 (m, C=C-H), 2954 (s), 1730 (m, C=O), 1374 (m), 1256 (m), 1137 (s), 1074 (s), 836 (m). 1LC (40% EtOAc in Hexanes), Rf 131.: 0.50 (anisaldehyde) 132: 0.61 (anisaldehyde) 299 II lESO,,.. LiN(TMSb, LiCI, i 11 THF,-78 °C 11 H 67% 12 ,:· TBSO.: TBSO 132 10 133 Cyclic alcohol 13 3 Lithium hexamethyldisilazide (320 µL of a freshly prepared 1.0 M solution in hexanes, 0.32 mmol, 10 equiv) was added dropwise over a 2 minute period to a vigorously stirring suspension of epoxy aldehyde 132 (18 mg, 3.2 x 10-2 mmol, 1 equiv) and lithium chloride (68 mg, 1.6 mmol, 50 equiv) in tetrahydrofuran (1.6 mL) at -78 °C. The suspension was allowed to stir at -78 °C for an additional 10 min, then excess base was quenched by the addition of saturated aqueous ammonium chloride (2 mL). The mixture was warmed to 23 °C and partitioned between water (10 mL) and 1:1 ethyl acetate/hexanes (10 mL). The layers were separated and the aqueous layer was further extracted with 1:1 ethyl acetate/hexanes (2 10-mL portions). The combined organics were washed once with saturated aqueous sodium chloride (15 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (2% ethyl acetate in dichloromethane grading to 10% ethyl acetate in dichloromethane) afforded cyclic alcohol 133 (12 mg, 67%) as a colorless oil. 300 5.41 (d, lH, J = 9.52 Hz, C8 H), 4.22 (d, lH, J =5.84 Hz, Cl 1 H), 3.90 (dd, lH, J = 8.44, 5.88 Hz, C13 H), 3.74 (dd, 1 H, J = 8.80, 6.56 Hz, C14 H), 3.68 (s, lH, ClO H), 3.63 (t, lH, J = 5.88 Hz, C14 H), 3.17 (s, lH, CS H), 2.34 (dd, lH, J = 14.28 5.88 Hz, C12 ~H), 1.98 (d, lH, J = 14.64 Hz, C12 aH), 1.82 (d, lH, J = 9.52 Hz, OH), 1.48 (s, 3H, C(CH 3) 2), 1.23 (s, 3H, C(CH 3) 2 ), 1.11 (t, 9H, J = 8.08 Hz, OSi(CH2CH 3) 3), 0.92 (m, 6H, OSi(CH 2CH 3) 3), 0.91 (s, 9H, OSiC(CH 3)iCH 3) 2), -0.012 (s, 3H, OSiC(CH 3)iCH 3) 2) , -0.018 (s, 3H, OSiC(CH 3)iCH 3) 2) . FTIR (thin film), cm- 1: 3447 (m, OH), 2954 (s), 2933 (s), 1460 (m), 1257 (m), 1134 (s), 1075 (s), 836 (m). 1LC (40% EtOAc in Hexanes), Rf 132: 0.56 (anisaldehyde) 133: 0.48 (anisaldehyde) 301 1, 1'-thiocarbonyldiimidazole, 11 11 II 11 DMAP, CH 2Cl2, 23 °C s a H II 89% TBSO.: 133 ·•,o,.)l....~N 12 ,• TBSO 10 0 '==-' 134 Thiocarbonylimidazolide 1 3 4 Thiocarbonyldiimidazole (84 mg of 90% pure, 0.43 mmol, 10 equiv) and 4dimethylaminopyridine (26 mg, 0.21 mmol, 5 equiv) were added sequentially to a solution of alcohol 133 (24 mg, 4.3 x 10·2 mmol, 1 equiv) in dichloromethane (2.5 mL). The resultant orange solution was stirred at 23 °C for 25 min and concentrated. Purification of the residue by flash column chromatography (4% ethyl acetate in hexanes grading to 10% ethyl acetate in hexanes) afforded thiocarbonylimidazolide 134 (24 mg, 89%) as a yellow oil. 302 8.25 (s, lH, imidazole), 7.26 (s, lH, imidazole), 7.23 (s, lH, C8 H), 6.86 (s, lH, imidazole), 4.29 (d, lH, J =5.84 Hz, Cll H), 3.91 (dd, lH, J = 8.80, 5.88 Hz, C13 H), 3.76 (dd, 1 H, J = 8.80, 6.60 Hz, C14 H), 3.69 (s, lH, ClO H), 3.63 (t, lH, J = 5.84 Hz, C14 H), 3.13 (s, lH, C5 H), 2.39 (dd, lH, J = 14.64, 5.84 Hz, C12 PH), 2.05 (d, lH, J = 14.64 Hz, C12 aH), 1.52 (s, 3H, C(CH 3) 2), 1.26 (s, 3H, C(CH 3 ) 2), 1.23 (t, 9H, J = 8.04 Hz, OSi(CH 2CH 3 ) 3), 1.02 (m, 6H, OSi(CH 2CH 3) 3), 0.91 (s, 9H, OSiC(CH 3)iCH 3) 2), 0.001 (s, 3H, OSiC(CH 3)iCH 3) 2), --0.024 (s, 3H, OSiC(CH 3)iCH 3) 2). FTIR (thin film), cm· 1: 2953 (s), 1463 (m), 1394 (m), 1286 (m), 1135 (s), 1073 (s), 835 (m), 744 (m). HRMS (FAB): Calc'd for C29 H49 N2O7SSi 2 [MHt: 625.2799 Found: 625.2849 133: 0.34 (anisaldehyde) 134: 0.46 (UV, anisaldehyde) 303 TBSO.: 10 135 Rearran&ement product (suggested structure 13 5) Tributyltin hydride (0.0107 mL, 11.6 mg, 4.00 x 10·2 mmol, IO equiv) was added to a solution of thiocarbonylimidazolide 134 (2.5 mg, 4.0 x 10-3 mmol, 1 equiv) in benzene (0.4 mL) at 23 °C. The solution was deoxygenated by five freeze-pump-thaw cycles and then stirred at 23 °C under an atmosphere of argon for 20 min. The reaction mixture was ·concentrated to a volume of ca. 0.1 mL and applied directly to a silica gel column packed with dichloromethane. Chromatography (dichloromethane grading to 10% ethyl acetate in dichloromethane) was followed by pooling of the fractions containing the product and concentration to ca. 0.1 mL. Deuteriated benzene (99.5 atom % D, 0.4 mL) was added to the concentrate and the solution concentrated to ca. 0.1 mL. This process was repeated four times. The concentrate was taken up in deuteriated benzene (99.95 atom % D, 0.4 mL). Although not unequivocally assigned, all spectral data corresponded to a product having the structure 135. 304 6.71 (d, lH, J = 5.52 Hz, C7 H), 6.54 (d, lH, J = 5.88 Hz, CS H), 5.47 (s, lH, C3 H), 5.33 (s, lH, C5 H), 4.78 (dd, lH J = 5.84, 2.92 Hz, C11 H), 4.73 {t, lH, J = 6.20 Hz, C13 H), 4.01 (dd ,lH, J = 1.84, 1.08 Hz, ClO H), 3.91 (dd, lH, J = 8.40, 6.96 Hz, C14 H), 3.48 (dd, lH, J = 8.76, 6.20 H, C14 H), 3.44 (s, lH, OH), 2.78 (dd, lH, J = 15.72, 2.92 Hz, C12 ~H), 2.43 (ddd, lH, J = 15.84, 2.92, 1.08 Hz, C12 aH), 1.43 (s, 3H, C(CH 3) 2 ), 1.35 (s, 3H, C(CH 3)i), 1.30-0.83 (complex, 15H, OSi(CH 2CH 3) 3), OSiC(CH 3)/CH 3)i), OSiC(CH 3 ) 3 (CH 3) 2), 0.82 (s, 9H, 0.10 (s, 3H, (s, 3H, 0.09 OSiC(CH 3)/CH 3) 2). FI1R (thin film), cm- 1: 3448 (m, OH), 2923 (s) , 1736 (m), 1637 (m), 1366 (m), 1460 (m), 1078 (m). HRMS (FAB): Calc'd for C29H 49 O6 Si 2 [MHt: 549.306772 Found: 549.305561 134: 0.34 (UV, anisaldehyde) 135: 0.46 (UV, anisaldehyde) 305 II~ TMSO,,. II ~ DIBAL, PhCH 3 , -78 °C H CHO lBSO.: 67 TMSO,,.. 94% 1 H 12 rssd 10 136 Allylic alcohol 13 6 Diisobutylaluminum hydride (0.662 mL of a 1.5 M solution in toluene, 0.992 mmol, 1.1 equiv) was added in a dropwise manner to a solution of the enal 67 (1.78 g, 3.53 mmol, 1 equiv) in toluene (18 mL) at -78 °C. The reaction mixture was allowed to stir at -78 °C for an additional IO min, and excess diisobutylaluminum hydride was quenched by the addition of methanol (10 mL), and the reaction warmed to 0 °C. After 20 minutes at 0 °C, 10% aqueous potassium sodium tartrate (20 mL) was added, and the mixture was wanned to 23 °C and stirred vigorously for an additional 30 minutes. The layers were then separated, and the aqueous layer was extracted with ethyl acetate (3 20-mL portions). The combined organics were washed with saturated aqueous sodium chloride (25 mL) and were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (30% ethyl acetate in hexanes) provided the allylic alcohol 136 (405 mg, 94%) as a colorless oil. 306 5.85 (d, lH, J = 1.44 Hz, ClO H), 4.88 (tdd, lH, J = 6.60, 4.88, 1.84 Hz, C11 H), 4.53 (m, 2H, C8 H), 4.04 (dd, lH, J = 8.44, 5.48 Hz, C13 H), 3.78 (dd, lH, J = 8.80, 6.96 Hz, C14 H), 3.48 (dd, lH, J = 6.96, 5.48 Hz, C14 H), 3.22 (d, lH, J = 1.80 Hz, CS H), 3.18 (dd, lH, J = 12.44, 6.96 Hz, C12 H), 2.39 (dd, lH, J = 12.48, 6.24 Hz, C12 H), 2.07 (s, lH, J = 1.48 Hz, C7 H), 1.47 (s, 3H, C(CH 3) 2), 1.18 (s, 3H, C(CH 3) 2 ), 0.99 (s, 9H, (s, OSiC(CH 3MCH 3) 2), OSi(CH 3) 3), 0.09 OSiC(CH 3)iCH 3) 2), 0.33 3H, (s, 0.08 9H, (s, 3H, OSiC(CH 3)iCH 3) 2). 148.6, 131.0, 110.7, 89.3, 78.8, 78.2, 77.4, 76.9, 75.3, 73.9, 66.7, 58.9, 57.8, 54.5, 50.4, 26.4, 26.0, 25.0, 18.2, 1.9, -4.6 (2). FI1R (thin film), cm- 1: 3448 (m, OH), 3309 (m, C=C-H), 2954 (s), 2857 (m), 2128 (w, C=C), 1462 (m), 1372 (m), 1253 (s), 1110 (s), 1075 (s), 839 (s). 67: 0.88 (UV, anisaldehyde) 136: 0.46 (anisaldehyde) 307 II TMSO,,.. iH II (+)-DET, Ti(Oi-Pr) 4 , TBHP, 3A MS, CH2Cl 2, -20 °C i7 H TMSO,,.. 12 TBSO.: 91% 136 TBSO.: 10 137 Epoxy alcohol 13 7 A suspension of 3A molecular sieves (approx. 0.5g, crushed and flame-dried under vacuum in the reaction flask) in dichloromethane (80 mL) was cooled to -20 °C. (+ )Diethyl-L-tartrate (2.84 mL, 3.42 g, 16.6 mmol, 6 equiv) and titanium(IV) isopropoxide (4.11 mL, 3.93 g, 13.8 mmol, 5 eq) were added sequentially via syringe. The mixture was allowed to stir at -20 °C for an additional 15 min, and the allylic alcohol 136 ( I .40 g, 2.76 mmol, 1 eq) in dichloromethane (60 mL) was added via cannula. The resultant mixture was stirred at -20 °C for another 30 min, and tert-butyl hydroperoxide (5.88 of a 4.7 M solution in dichloromethane, 27.6 mmol, 10 eq) was added through a slit in the septum at the neck of the flask via a gastight syringe equipped with a Teflon needle. The reaction was maintained at -20 °C for 15 h, and the catalyst was quenched with 10% aqueous D-tartaric acid (50 mL) and stirred vigorously at 23 °C for 30 min. The reaction mixture was filtered, the layers were separated, and the aqueous layer was further extracted with dichloromethane (2 50-mL portions). The combined organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (15% ethyl acetate in hexanes grading to 20% ethyl acetate in hexanes) afforded epoxy alcohol 137 (1.31 g, 91 %) as a colorless oil. 308 4.31 (m, 2H, C8 H), 4.22 (d, lH, J = 5.84 Hz, Cl 1 H), 4.06 (dd, lH, J = 8.80, 5.48 Hz, C13 H), 3.80 (dd, lH, J = 8.44, 6.60 Hz, C14 H), 3.55 (complex, 2H, ClO and C14 H), 3.28 (d, lH, J = 1.48 Hz, C5 H), 2.38 (dd, lH, J = 14.28, 5.84 Hz, C12 BH), 2.06 (d, lH, J = 14.64 Hz, C12 aH), 2.01 (d, lH, J = 1.80 Hz, C7 H), 1.46 (s, 3H, C(CH 3) 2), 1.14 (s, 3H, C(CH 3) 2), 0.90 (s, 9H, OSiC(CH 3)(CH 3) 2), 0.33 (s, 9H, OSi(CH 3\), -0.045 (s, 6H, OSiC(CH 3)(CH 3) 2). 110.8, 87.7, 79.9, 78.3, 77.1, 75.4, 74.7, 71.8, 71.4, 66.7, 63.6, 58.0, 50.5, 50.0, 26.3, 25.9, 25.1, 18.2, 1.9, -4.8. FTIR (thin film), cm- 1: 3486 (m, OH), 3267 (m, C=C-H), 2955 (s), 2893 (s), 2859 (s), 2131 (w, C=C), 1373 (m), 1253 (s), 1214 (m), 1135 (s), 1075 (s), 945 (m), 843 (s). 309 HRMS (FAB): Calc'd for C 26H4 1O7 Si2 [M-lt: 521.239086 Found: 521.239042 136: 0.41 (anisaldehyde) 137: 0.38 (anisaldehyde) 310 Dess-Martin periodinane, II i TMSO,,. H 11 pyridine, CH 2Cl2, 23 °C H TMSO,,.. 12 97% ... TBSO..- i1 TBSO 137 0 10 138 Epoxy aldehyde 1 3 8 Dess-Martin periodinane (2.03 g, 4.78 mmol, 2 equiv) was added portionwise to a solution of epoxy alcohol 137 (1.25 g, 2.39 mmol, 1 equiv) and pyridine (1.93 mL, 1.89 g, 23.9 mmol, 10 equiv) in dichloromethane (24 mL) at 23 °C. The resultant solution was stirred at 23 °C for 40 minutes, then diluted with diethyl ether (20 mL). Saturated aqueous sodium bicarbonate (10 mL) and saturated aqueous sodium thiosulfate (10 mL) were added, and the reaction mixture was stirred vigorously until the organic layer was clear (approximately 5-10 minutes). The layers were separated and the aqueous later was extracted with diethyl ether (2 20-mL portions). The combined organics were washed with saturated aqueous sodium chloride (20 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (15% ethyl acetate in hexanes) afforded the epoxy aldehyde 138 (1.21 g, 97%) as a pale yellow oil. 311 9.87 (s, lH, C8 H), 4.10 (d, lH, J = 5.84 Hz, Cll H), 4.05 (dd, lH, J = 8.80, 5.84 Hz, C13 H), 3.85 (dd, lH, J = 8.76, 6.56 Hz, C14 H), 3.65 (s, lH, ClO H), 3.60 (t, lH, J = 6.24 Hz, C14 H), 3.32 (d, lH, J = 1.48 Hz, C5 H), 2.28 (dd, lH, J = 14.64, 5.84 Hz, C12 ~H), 2.08 (d, lH, J = 1.80 Hz, C7 H), 2.06 (d, lH, J = 14.64 Hz, C12 aH), 1.45 (s, 3H, C(CH 3) 2), 1.18 (s, 3H, C(CH 3) 2 ), 0.90 (s, 9H, (s, OSiC(CH 3) 3(CH 3)J, OSi(CH 3) 3), 0.42 -0.056 OSiC(CH 3)iCH 3) 2), (s, -0.071 9H, 6H, (s, 6H, OSiC(CH 3\(CH 3) 2). 193.1, 110.8, 86.4, 80.8, 78.0, 76.8, 75.5, 73.0, 71.0, 70.7, 66.8 (2), 57.8, 50.4, 49.9, 26.3, 25.9, 25.2, 18.1, 2.0, -4.9. FTIR (thin film), cm- 1: 3270 (m, C::C-H), 2955 (s), 2851 (s), 2131 (w, C=C), 1730 (s, C=O), 1374 (m), 1253 (s), 1215 (m), 1138 (s), 1074 (s), 945 (m), 845 (s). 312 HRMS (FAB): Calc'd for C26H39 01Si2 [M-lt: 519.223436 Found: 519.223453 137: 0.50 (anisaldehyde) 138: 0.68 (anisaldehyde) 313 II TMSO,,.. ~ H .. ,CHO LiN(TMSb LiCI, THF, -78°C 11 00% II 12 0 TBSO.: -i TBSO 138 10 139 Cyclized bisepoxide 139 (for improved procedure, seep. 387) Lithium hexamethyldisilazide (1.36 mL of a 1.0 M solution in hexanes, 1.36 mmol, 5 equiv) was added dropwise over a 2 minute period to a vigorously stirring suspension of the epoxy aldehyde 138 (142 mg, 0.272 mmol, 1 equiv) and dry lithium chloride (578 mg, 13.6 mmol, 50 equiv) in tetrahydrofuran (14 mL) at-78 °C. The suspension was allowed to stir at - 78 °C for an additional 10 min, and excess base was quenched by the addition of saturated aqueous ammonium chloride (5 mL). The mixture was warmed to 23 °C and partitioned between water (10 mL) and 1:1 ethyl acetate/hexanes (10 mL). The layers were separated and the aqueous layer was further extracted with 1:1 ethyl acetate/hexanes (2 10mL portions). The combined organics were washed once with saturated aqueous sodium chloride (25 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (20% ethyl acetate in hexanes) afforded cyclized bisepoxide 139 ( 113 mg, 80%) as a yellow oil. 314 5.35 (d, lH, J = 10.60 Hz, C8 H), 4.18 (d, lH, J = 5.84 Hz, Cl 1 H), 3.88 (dd, lH, J = 8.40, 6.60 Hz, C13 H), 3.74 (dd, 1 H, J = 8.40, 5.84 Hz, C14 H), 3.66 (s, lH, ClO H), 3.65 (t, lH, J = 6.20 Hz, C14 H), 3.18 (s, lH, C5 H), 2.27 (dd, lH, J = 14.28, 5.84 Hz, C12 PH), 1.93 (d, lH, J = 14.28 Hz, C12 aH), 1.87 (d, lH, J = 11.00 Hz, OH), 1.48 (s, 3H, C(CH 3) 2), 1.23 (s, 3H, C(CH 3) 2 ), 0.91 (s, 9H, OSiC(CH 3)/CH 3) 2), 0.36 (s, 9H, Si(CH 3) 3), -0.023 (s, 3H, OSiC(CH)iCH 3) 2), -0.026 (s, 3H, OSiC(CH 3)iCH 3) 2). 110.7, 92.9, 88.3, 87.6, 86.7, 80.8, 75.1, 70.7, 66.8, 64.0, 61.8, 57.2, 52.5, 48.2, 26.3, 25_9, 25.5, 18.1, 1.8, -4.8 FI1R (thin film), cm-1: 3448 (m, OH), 2954 (s), 2860 (m), 2214 (w, C=C), 1373 (m), 1253 (s), 1135 (s), 1075 (s), 953 (m), 843 (s). HRMS (FAB): Calc'd for C26 H39 0 7Si 2 [M-1]+: 519.223436 Found: 519.222949. 315 138: 0.69 (anisaldehyde) 139: 0.60 (anisaldehyde) 316 (±)-CSA, 2: 1 CH 3CN/H 2O, 23 °C TBSO.: 139 11 11 11 11 + 12 TBSd 10 •• 140 (47%) 141 (24%) Diol 140 and triol 141 (±)-Camphorsulfonic acid (83 mg, 0.36 mmol, 5 equiv) was added in one portion to a solution of alcohol 139 (37 mg, 7.1 x 10-2 mmol, 1 equiv) in 2:1 acetonitrile/water (7.1 mL) at 23 °C. The resultant pale yellow solution was maintained at 23 °C for 40 min, poured into water (20 mL), and extracted with 1: 1 ethyl acetate/hexanes (3 25-mL portions). The combined organic layers were washed once with brine (20 mL), and were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (5% ethyl acetate in hexanes to elute 140, followed by 100% ethyl acetate to elute 141) afforded diol 140 (15 mg, 47%) as a pale yellow oil and trial 141 (5.7 mg, 24% ), also as a pale yellow oil. 317 For 140: 5.40 (br s, lH, C8 H), 3.99 (d, lH, J = 5.12 Hz, Cl 1 H), 3.94 (dd, lH, J =8.76, 5.48 Hz, C13 H), 3.75 (dd, 1 H, J = 8.76, 6.96 Hz, C14 H), 3.62 (t, lH, J = 6.24 Hz, C14 H), 3.57 (s, lH, ClO H), 3.20 (s, lH, C5 H), 2.94 (br s, lH, OH), 2.15 (dd, lH, J = 14.28, 4.76 Hz, C12 ~H), 1.93 (br s, lH, OH), 1.75 (d, lH, J = 14.68 Hz, C12 cxH), 1.52 (s, 3H, C(C~ 3)i), 1.25 (s, 3H, C(CH 3) 2), 0.78 (s, 9H, OSiC(CH 3)iCH 3) 2), -0.15 OSiC(CH 3)/CH 3) 2), -0.16 OSiC(CH 3)/CH 3) 2). 139: 0.49 (anisaldehyde) 140: 0.31 (anisaldehyde) (s, (s, 3H, 3H, 318 For 141: 5.10 (d, lH, J = 11.00 Hz, C8 H), 3.80 (dd, lH, J = 7.96, 5.84 Hz, C13 H), 3.76 (dd, lH, J = 8.44, 4.76 Hz, C11 H), 3.69 (dd, 1 H, J = 8.44, 6.60 Hz, C14 H), 3.57 (t, lH, J = 5.84 Hz, C14 H), 3.38 (s, lH, ClO H), 3.08 (s, lH, C5 H), 1.96 (dd, lH, J = 14.64, 5.12 Hz, C12 ~H), 1.71 (d, lH, J = 10.96 Hz, C8 OH), 1.55 (d, lH, J = 14.64 Hz, C12 cxH), 1.41 ..(s, 3H, C(CH 3)i), C(CH 3)i). 139: 0.49 (anisaldehyde) 141: 0.00 (anisaldehyde) 1.19 (s, 3H, 319 11 11 1, 1'-thiocarl:>onyldiimidazole, II DMAP, CH 2Cl 2, 23 °C II s a H II ••, o.,.w... 90% TBSO.: 140 ~· TBSO 0 10 142 Thiocarbonylimidazolide 14 2 Thiocarbonyldiimi~azole (106 mg of 90% pure, 0.54 mmol, 10 equiv) and 4dimethylaminopyridine (33 mg, 0.27 mmol, 5 equiv) were added sequentially to a solution of diol 140 (24 mg, 0.054 mmol, 1 equiv) in dichloromethane (2.7 mL). Toe resultant orange solution was placed in a 40 °C oil bath and heated to a gentle reflux for 25 min. The reaction mixture was cooled to 23 °C and concentrated. Purification of the residue by flash column chromatography (25% ethyl acetate in hexanes) afforded thiocarbonylimidazolide 142 (26 mg, 90%) as a yellow oil. 320 8.23 (s, lH, imidazole), 7.29 (s, lH, C8 H), 7.23 (s, lH, imidazole), 6.84 (s, lH, imidazole), 3.99 (d, lH, J =5.12 Hz, Cl 1 H), 3.93 (dd, lH, J = 8.76, 5.52 Hz, C13 H), 3.75 (dd, 1 H, J = 8.80, 6.56 Hz, C14 H), 3.60 (t, lH, J = 5.52 Hz, C14 H), 3.39 (s, lH, ClO H), 3.36 (br s, lH, OH), 3.13 (s, lH, C5 H), 2.15 (dd, lH, J = 14.28, 4.76 Hz, C12 PH), 1.77 (d, lH, J = 14.64 Hz, C12 aH), 1.53 (s, 3H, C(CH 3 ) 2 ), 1.25 (s, 3H, C(CH 3 ) 2 ), 0.78 (s, 9H, OSiC(CH 3 ) 3 (CH 3 ) 2 ), --0.17 (s, 3H, OSiC(CH 3 )iCH 3 ) 2 ), --0.18 (s, 3H, OSiC(CH 3 )iCH 3 ) 2 ). TLC (50% EtOAc in Hexanes), Rf: 140: 0.48 (anisaldehyde) 142: 0.40 (UV, anisaldehyde) 321 CH 3SO2 Ct, Et3 N, 11 CH 2 Ct2 , 0 °C 11 12 78% TBSO.: 139 TBSO.:' 10 143 Methanesulfonate ester 1 4 3 Methanesulfonyl chloride (9.0 µL, 13 mg, 0.12 mmol, 10 equiv) was added to a solution of alcohol 139 (6.0 mg, 1.2 x 10·2 mmol, 1 equiv) and triethylamine (40 µL, 29 mg, 0.29 mmol, 25 equiv) in dichloromethane (0.6 mL) at 0 °C. The resultant pale yellow solution was stirred at 0 °C for an additional 5 min, and diluted with hexanes (10 mL) and washed with water (3 5-mL portions) and brine (5 mL). The organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (4% ethyl acetate in dichloromethane) afforded methanesulfonate ester 143 (5.4 mg, 78%) as a colorless oil. 322 6.47 (s, lH, CS H), 4.09 (d, lH, J = 5.52 Hz, Cl 1 H), 3.93 (s, lH, CIO H), 3.81 (dd, lH, J = 8.80, 5.52 Hz, C13 H), 3.68 (dd, 1 H, J = 8.80, 6.60 Hz, C14 H), 3.59 (t, lH, J = 5.84 Hz, C14 H), 3.07 (s, lH, C5 H), 2.28 (s, 3H, OSO CH 2 3 ), 2.19 (dd, lH, J = 14.64, 5.88 Hz, C12 ~H), 1.89 (d, lH, J = 14.64 Hz, C12 a.H), 1.43 (s, 3H, C(CH 3) 2), 1.19 (s, 3H, C(CH 3 ) 2 ), 0.88 (s, 9H, OSiC(CH )iCH 3 3 ) 2 ), 0.30 (s, 9H, OSi(CH 3\), -0.052 (s, 3H, OSiC(CH )iCH 3 OSiC(CH )iCH 3 3 3 FTIR (thin film), crn- 1 : ) ) 2 2 ), -0.093 (s, 3H, ). 2954 (s), 2930 (s), 2884 (rn), 1460 (rn), 1413 (rn), 1371 (s), 1258 (s), 1180 (s), 1135 (s), 1074 (s), 1108 (rn), 963 (rn), 835 (rn). 139: 0.41 (anisaldehyde) 143: 0.66 (anisaldehyde) 323 11 11 H Cp2TiCI (ZnCl2), THF, 23 °C TBSO.: 139 144 Diol 144 Alcohol 139 (2.0 mg, 3.8 x 10·3 mmol, 1 equiv) in tetrahydrofuran (0.1 mL) was added dropwise via cannula to a green solution of dicyclopentadienyl titanium (Ill) chloride (29 µL of a 0.4 M stock solution in tetrahydrofuran prepared by the in situ method of RajanBabu and Nugent,96 0.012 mmol, 3 equiv) in tetrahydrofuran (0.1 mL) at 23 °C. The reaction mixture turned orange upon addition of the alcohol. The solution was maintained at 23 'C for an additional 2 min, and pH 7.2 phosphate buffer (1 mL) was added. The mixture was extracted with ethyl acetate (3 1-mL portions), and the combined organics were washed with saturated aqueous sodium bicarbonate (2 mL) and saturated aqueous sodium chloride (2 mL). The organics were dried over sodium sulfate and were concentrated to ca. 0.1 mL. Purification of the concentrate by flash column chromatography (dichloromethane grading to 20% ethyl acetate in dichloromethane) was followed by pooling the fractions containing the product and concentrating to a volume of ca. 0.1 mL. A 0.5 mL portion of deuteriated benzene (99.5 atom % D) was added and the resulting solution was concentrated to a volume of ca. 0.1 mL. repeated 4 times. This procedure was After the last iteration, the concentrated solution was taken up in 324 approximately 0.4 mL deuteriated benzene (99.95 atom % D). Analysis of the sample by 1 H NMR showed it to contain diol 144. 5.42 (d, lH, J =9.60 Hz, C8 H), 4.39 (t, lH, J = 6.24 Hz, C5 H), 4.21 (m, 2H, Cl 1, C13 H), 4.02 (dd, lH, J = 8.44, 6.24 Hz, C14 H), 3.85 (dd, lH, J = 8.40, 6.20 Hz, C14 H), 3.68 (s, lH, ClO H), 2.99 (dd, lH, J = 8.08, 6.24 Hz, C4 H), 2.31 (dd, lH, J = 12.08, 5.48 Hz, C12 ~H), 1.91 (d, lH, J = 12.08 Hz, C12 aH), 1.84 (d, lH, J = 9.60 Hz, C8 OH), 1.77 (m, lH, C5 OH), 1.33 (s, 3H, C(CH 3) 2), 1.20 (s, 3H, C(CH 3) 2), 0.89 (s, 9H, OSiC(CH 3)iCH 3) 2), OSi(CH 3)3), -0.06 0.31 (s, (s, 9H, 6H, OSiC(CH 3)iCH 3) 2). FTIR (thin film), cm· 1: 3421 (m, OH), 2928 (s), 2860 (m), 1460 (w), 1372 (m), 1252 (s), 1130 (s), 1076 (m), 843 (s). TLC (50% EtOAc in Hexanes), Rf. 139: 0.52 (anisaldehyde) 144: 0.34 (anisaldehyde) 325 11 11 Cp2TiCI (ZnCl 2), THF,23 °C TBSO.: 143 _.: 10 T8SO 145 Alcohol 145 Methanesulfonate ester 143 (2.0 mg, 3.3 x 10-3 mmol, 1 equiv) in tetrahydrofuran (0.1 mL) was added dropwise via cannula to a green solution of dicyclopentadienyl titanium (III) chloride (25 µL of a 0.4 M stock solution in tetrahydrofuran prepared by the in situ method of RajanBabu and Nugent,96 0.010 mmol, 3 equiv) in tetrahydrofuran (0.1 mL) at 23 °C. The reaction mixture turned orange upon addition of the alcohol. The solution was maintained at 23 °C for an additional 10 min and pH 7 .2 phosphate buffer (1 mL) was added. The mixture was extracted with ethyl acetate (3 1-mL portions), and the combined organics were washed with saturated aqueous sodium bicarbonate (2 mL) and saturated aqueous sodium chloride (2 mL). The organics were dried over sodium sulfate and were concentrated to ca. 0.1 mL. Purification of the concentrate by flash column chromatography (4% ethyl acetate in dichloromethane grading to 20% ethyl acetate in dichloromethane) was followed by pooling the fractions containing the product and concentrating to a volume of ca. 0.1 mL. A 0.5 mL portion of deuteriated benzene (99.5 atom% D) was added and the resulting solution was concentrated to a volume of ca. 0.1 mL. This procedure was repeated 4 times. After the last iteration, the concentrated 326 solution was taken up in approximately 0.4 mL deuteriated benzene (99.95 atom % D). Analysis of the sample by 1H NMR showed it to contain alcohol 145. 6.60 (s, lH, C8 H), 4.40 (t, lH, J = 4.40 Hz, CS H), 4.18 (m, 2H, Cll, Cl3 H), 3.98 (s, lH, ClO H), 3.96 (dd, lH, J = 8.76, 6.20 Hz, C14 H), 3.78 (dd, lH, J = 8.44, 5.88 Hz, C14 H), 2.87 (dd, lH, J = 8.40, 5.48 Hz, C4 H), 2.32 (s, 3H, OSO2CH 3), 2.29 (dd, lH, J = 14.64, 5.88 Hz, C12 ~H), 1.98 (d, lH, J = 5.12 Hz, OH), 1.93 (d, lH, J = 14.28 Hz, C12 aH), 1.28 (s, 3H, C(CH 3) 2), 1.18 (s, 3H, C(CH 3) 2) , 0.90 (s, 9H, OSiC(CH 3)iCH 3) 2), 0.30 (s, 9H, OSi(CH 3)3), -0.022 OSiC(CH 3)iCH 3) 2), -0.071 (s, 3H, (s, 3H, OSiC(CH 3) 3(CH 3) 2). FTIR (thin film), cm- 1: 3424 (m, OH), 2928 (s), 2856 (m), 1460 (w), 1367 (s), 1253 (s), 1179 (s), 1132 (s), 962 (m), 843 (s). 1LC (50% EtOAc in Hexanes), Rf. 143: 0.59 (anisaldehyde) 145: 0.41 (anisaldehyde) 327 Et3SiCI, imidazole, 11 II CH 2Cl 2, O °C 7',1¼ TBSO~ 140 11 11 12 TBSO.: 10 146 TES ether 1 4 6 Triethylsilyl chloride (22.6 µL , 19.8 mg, 0.131 mmol, 3.9 equiv) was added via syringe to a solution of diol 140 (15 mg, 3.3 x 10-2 mmol, 1 equiv) and imidazole (11 mg, 0.17 mmol, 5 equiv) in dichloromethane (1.7 mL) at O °C. The resultant solution was maintained at O °C for an additional 10 min, diluted with hexanes (5 mL), and washed with water (3 5-mL portions) and saturated aqueous sodium chloride (5 mL). The organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (5% ethyl acetate in hexanes grading to 15% ethyl acetate in hexanes) provided the triethylsilyl ether 146 (15 mg, 79%) as a colorless oil. 328 5.82 (s, lH, C8 H), 4.02 (d, lH, J = 4.40 Hz, C11 H), 3.91 (dd, lH, J = 8.40, 5.48 Hz, C13 H), 3.78 (s, lH, ClO H), 3.74 (dd, 1 H, J = 8.80, 6.60 Hz, C14 H), 3.64 (t, lH, J =5.88 Hz, C14 H), 3.13 (s, lH, CS H), 3.00 (s, lH, OH), 2.24 (dd, lH, J = 14.28, 4.40 Hz, C12 PH), 1.77 (d, lH, J = 14.28 Hz, C12 aH), 1.52 (s, 3H, C(CH 3) 2), (s, 1.26 3H, C(CH 3) 2), 1.06 (t, 9H, J = 7.68 Hz, OSi(CH 2CH 3) 3), (s, 9H, 0.69 (m, 6H, -0.012 (s, 3H, (s, 3H, OSiC(CH 3)/CH 3) 2), OSi(CH 2CH 3) 3), OSiC(CH 3)/CH 3) 2), 0.81 -0.14 OSiC(CH 3)iCH 3) 2). FflR (thin fihn), cm· 1: 3490 (m, OH), 2954 (s), 1462 (m), 1373 (m), 1256 (m), 1104 (s), 1070 (s), 1004 (m), 908 (m), 837 (m). 1LC (20% EtOAc in Hexanes), Rf: 140: 0.06 (anisaldehyde) 146: 0.38 (anisaldehyde) 329 Tfp, 2,6-<fi-tert-butylpyricfine, 11 11 CH2C'2, -78 ➔ 23 °C 11 11 45% TBSO-: 146 -:· TBSO 10 147 Olefin 147 Trifluoromethanesulfonic anhydride (150 µL, 251 mg, 0.888 mmol, 100 equiv) was added dropwise via syringe to a solution of the alcohol 146 (5.0 mg, 8.9 x 10-3 mmol, 1 equiv) and 2,6-di-tert-butylpyridine (400 µL, 340 mg, 1.78 mmol, 200 equiv) in dichloromethane (440 µL) at -78 °C. The resultant colorless solution with a white precipitate was immediately warmed to 23 °C and maintained at this temperature for 2 hours. During the course of the reaction, the precipitate went into solution and the color of the reaction changed from colorless to pale yellow, light brown, and finally to brown. The reaction mixture was diluted with hexanes (3 mL) and washed with water (3 1-mL portions) and saturated aqueous sodium chloride (1 mL). The organics were dried over sodium sulfate and concentrated to ca. 0.1 mL. Purification of the concentrate (100% hexanes initially to flush through residual 2,6-di-tert-butylpyridine, then 10% ethyl acetate in hexanes) was followed by pooling fractions containing the product and concentrating to a volume of ca. 0.1 mL. A 0.5 mL portion of deuteriated benzene (99.5 atom % D) was added and the resulting solution was concentrated to a volume of ca. 0.1 mL. This procedure was repeated 4 times. After the last iteration, the concentrated solution was taken up in approximately 0.4 mL deuteriated benzene (99.95 atom % D). trans- 330 Dichloroethylene (10 µL of a 0.130 M solution in deuteriated chloroform (10 µL dichloroethylene diluted to 1.0 mL)) was added as an internal standard. Analysis of the sample by 1H NMR showed it to contain 4.00 x 10-3 mmol (45%) of bisepoxy enediyne 147 as determined by integration of the internal standard against the C-12 proton. 5.88 (t, lH, J = 2.56 Hz, C12 H), 5.14 (s, lH, C8 H), 4.49 (d, lH, J = 2.20 Hz, C11 H), 3.90 (m, 2H, CIO and C13 H), 3.78 (dd, lH, J = 8.80, 6.60 Hz, C14 H), 3.69 (t, lH, J =5.84 Hz, C14 H), 3.15 (s, IH, C5 H), 1.49 (s, 3H, C(CH 3) 2), 1.25 (s, 3H, C(CH 3) 2), 1.04 (t, 9H, J = 8.04 Hz, OSi(CH2CH 3) 3), 0.92 (s, 9H, OSiC(CH 3)/CH 3) 2), 0.69 (m, 6H, OSi(CH2CH 3) 3), OSiC(CH 3) 3(CH 3) 2), -0.027 -0.050 OSiC(CH 3)iCH 3) 2). TLC (20% EtOAc in Hexanes), Rf 146: 0.21 (anisaldehyde) 147: 0.33 (UV, anisaldehyde) (s, 3H, (s, 3H, 331 II II 11 II a H .,,OH 0 .:- TBSO.: TBSO 147 10 148 Secondaiy alcohol 14 8 (±)-Camphorsulfonic acid (4.0 mg, 1.8 x 10·2 mmol, 5 equiv) was added in one portion to a solution of bisepoxy enediyne 147 (2.0 mg, 3.7 x 10·3 mmol, 1 equiv) in 2:1 acetonitrile/water (0.37 mL) at 23 °C. The resultant pale yellow solution was maintained at 23 °C for 15 min and extracted with 1:1 ethyl acetate/hexanes (3 2-mL portions). The combined organic layers were washed once with brine (2 mL), dried over sodium sulfate and concentrated to a volume of ca. 0.1 mL. Purification of the residue by flash column chromatography (10% ethyl acetate in hexanes grading to 20% ethyl acetate in hexanes) was followed by pooling fractions containing the product and concentrating to a volume of ca. 0.1 mL. A 0.5 mL portion of deuteriated benzene (99.5 atom % D) was added and the resulting solution was concentrated to a volume of ca. 0.1 mL. repeated 4 times. This procedure was After the last iteration, the concentrated solution was taken up in approximately 0.4 mL deuteriated benzene (99.95 atom % D). trans-Dichloroethylene (10 µL of a 0.130 M solution in deuteriated chloroform (10 µL dichloroethylene diluted to 1.0 mL)) was added as an internal standard. Analysis of the sample by 1H NMR showed it to contain 3.2 x 10·3 mmol (87%) of secondary alcohol 148 as determined by integration of the internal standard against the C-12 proton. 332 5.82 (t, lH, J = 2.56 Hz, C12 H), 5.14 (d, lH, J = 10.60 Hz, C8 H), 4.42 (d, lH, J = 2.20 Hz, Cl 1 H), 3.95 (dd, lH, J = 8.80, 5.48 Hz, C13 H), 3.79 (dd, lH, J = 8.80, 6.60 Hz, C14 H), 3.66 (m, 2H, ClO, C14 H), 3.15 (s, lH, C5 H), 2.02 (d, lH, J = 11.00 Hz, C8 OH), 1.51 (s, 3H, C(CH 3)2), 1.24 (s, 3H, C(CH 3)z), 0.89 (s, 9H, OSiC(CH 3)iCH 3) 2), --0.067 (s, 3H, OSiC(CH 3)iCH 3) 2) , --0.087 (s, 3H, OSiC(CH 3) 3(CH 3) 2). 1LC (20% EtOAc in Hexanes), Rf. 147: 0.38 (UV, anisaldehyde) 148: 0.15 (UV, anisaldehyde) 333 11 II CS(lm) 2 , DMAP, 11 CH202,23 °C TBSO,:: 11 s s H)l ··,o ~N 0 '==1 10 149 Thiocarbonylimidazolide I 4 9 Thiocarbonyldiimidazole (3.2 mg of 90% pure, 1.63 x 10-2 mmol, 10 equiv) and 4dimethylaminopyridine (1.0 mg, 8.1 x 10-3 mmol, 5 equiv) were added sequentially to a solution of secondary alcohol 148 (0.70 mg, 1.6 x 10-3 mmol, 1 equiv) in dichloromethane (0.1 mL). The resultant orange solution was stirred at 23 °C for 5 min, and loaded directly onto a column packed with silica gel and 25% ethyl acetate in hexanes. Elution of the product with the same solvent system was followed by pooling fractions containing the product and concentrating to a volume of ca. 0.1 mL. A 0.5 mL portion of deuteriated benzene (99.5 atom % D) was added and the resultant solution concentrated to a volume of ca. 0.1 mL. This procedure was repeated 4 times. After the last iteration, the concentrated solution was taken up in approximately 0.4 mL deuteriated benzene (99.95 atom % D). Analysis of the sample by 1H NMR showed it to contain thiocarbonylimidazolide 149. 334 8.23 (s, lH, imidazole), 7.26 (s, lH, imidazole), 6.82 (s, lH, imidazole), 6.38 (s, lH, C8 H), 5.85 (t, lH, J = 2.20 Hz, C12 H), 4.42 (d, lH, J = 2.56 Hz, Cll H), 3.95 (dd, lH, J = 8.80, 5.48 Hz, C13 H), 3.79 (dd, lH, J = 8.76, 6.56 Hz, C14 H), 3.66 (d, lH, J = 2.56 Hz, ClO H), 3.62 (t, lH, J = 5.52 Hz, C14 H), 3.09 (s, lH, C5 H), 1.53 (s, 3H, C(CH 3)i), 1.24 (s, 3H, C(CH 3)i), 0.88 (s, 9H, OSiC(CH 3)iCH 3) 2), -0.063 (s, 3H, OSiC(CH 3)iCH 3) 2), --0.079 OSiC(CH 3)/CH 3) 2). TLC (50% EtOAc in Hexanes), Rf. 148: 0.48 (UV, anisaldehyde) 149: 0.36 (UV, anisaldehyde) (s, 3H, 335 II~ TlPSOTf, 2,6-lutidine, H CH2C'2, -78 ➔ 0 °C 89% 11 HO,,.. 12 f TIPSO 47 10 150 TIPS ether 1 5Q 2,6-Lutidine (4.09 mL, 3.76 g, 35.1 mmol, 10 equiv) and triisopropylsilyl trifluoromethanesulfonate (4.72 mL, 5.38 g, 17.6 mmol, 5 equiv) were added sequentially via syringe to a solution of diol 47 (1.28 g, 3.51 mmol, 1 equiv) in dichloromethane (87 mL) at-78 °C. The resultant pale yellow solution was maintained at this temperature for an additional 20 min before warming to 0 °C for 5 min. Excess silyl triflate was quenched by the addition of triethylamine and methanol (10 mL each), and the reaction mixture was poured into 1:1 ethyl acetate/hexanes (75 mL). The resultant solution was washed twice with water (50 mL) and once with saturated aqueous sodium chloride (50 mL). The organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (10% ethyl acetate in hexanes grading to 30% ethyl acetate in hexanes) afforded triisopropylsilyl ether 150 (1.63 g, 89%) as a pale yellow oil. 336 6.25 (m, lH, ClO H), 5.44 (m, lH, C8 H), 4.92 (m, lH, C11 H), 4.09 (dd, lH, J = 8.76, 5.84 Hz, C13 H), 3.97 (s, lH, OH), 3.84 (m, lH, C14 H), 3.60 (t, lH, J = 5.88 Hz, C14 H), 3.37 (d, lH, J = 1.48 Hz, C5 H), 3.20 (dd, lH, J = 12.80, 7.32 Hz, C12 (3H), 3.19 (s, 3H, CH(OCH 3) 2), 3.16 (s, 3H, CH(OCH 3) 2), 2.56 (dd, lH, J = 13.20, 5.12 Hz, C12 aH), 2.03 (d, lH, J = 1.48 Hz, C7 H), 1.46 (s, 3H, C(CH 3)2), 1.20 (s, 3H, C(CH 3) 2), 1.10-0.90 (complex, 21H, OSi(CH(CH 3}i) 3). 142.8, 136.1, 110.7, 99.8, 90.1, 78.5, 77.2, 75.2, 74.8, 73.4, 66.9, 58.0, 52.7, 52.5, 52.2, 50.1, 26.3, 25.3, 18.1, 12.3. FTIR (thin film), cm· 1: 3487 (m, OH), 3309 (m, C=C-H), 2943 (s), 2866 (s), 2237 (w, C=C), 2131 (w, C=C), 1462 (m), 1372 (m), 1191 (m), 1069 (s), 884 (m). HRMS (FAB): Calc'd for C28 H43 O7 Si [M-H] +: 519.279800 Found: 519.277808 337 1LC (40% EtOAc in Hexanes), Rf. 47: 0.05 (anisaldehyde) 150: 0.44 (anisaldehyde) 338 II i i7 p-TsOH, acetone, 23 "C 11 H 94% H HO,,,. CHO 12 .: llPSO.: TIPSO 150 10 151 Enal 151 p-Toluenesulfonic acid (65 mg) was added in one portion to a solution of triisopropylsilyl ether 150 (191 mg, 0.366 mmol, 1 equiv) in acetone (9 mL) at 23 °C. The resultant pale yellow solution was maintained at 23 °C for 10 min and poured into water (20 mL). The reaction mixture was extracted with 1:1 ethyl acetate/hexanes (3 20mL portions), and the combined organics were washed once with saturated aqueous sodium chloride (25 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (20% ethyl acetate in hexanes) afforded enal 151 (164 mg, 94%) as a colorless oil. 339 9.29 (s, lH, C8 H), 6.20 (d, lH, J = 1.44 Hz, ClO H), 4.91 (td, lH, J = 6.96, 1.44 Hz, Cl 1 H), 4.09 (dd, lH, J = 8.76, 5.84 Hz, C13 H), 3.87 (s, lH, OH), 3.84 (dd, lH, J = 8.76, 6.96 Hz, C14 H), 3.57 (t, lH, J = 6.20 Hz, C14 H), 3.36 (d, lH, J = 1.80 Hz, C5 H), 3.11 (dd, lH, J = 12.84, 6.96 Hz, C12 H), 2.41 (dd, lH, J = 12.84, 6.96 Hz, C12 H), 2.09 (d, lH, J = 1.84 Hz, C7 H), 1.44 (s, 3H, C(CH 3) 2), 1.19 (s, 3H, C(CH 3) 2), 1.12-0.91 (complex, 21 H, OSi(CH(CH 3) 2) 3). 189.2, 151.8, 145.6, 110.7, 88.5, 78.4, 78.3, 77.1, 74.8, 73.6, 73.4, 66.9, 57.9, 52.3, 50.1, 26.3, 25.3, 18.0, 12.2. FTIR (thin film), cm· 1: 3448 (m, OH), 3278 (m, C=C-H), 2943 (s), 2866 (s), 2131 (w, C=C), 1686 (s, C=O), 1461 (m), 1352 (m), 1259 (m), 1121 (m), 1071 (s), 882 (m). HRMS (FAB): Calc'd for C26H37 O6 Si [M-H] +: 473.2346000 Found: 473.255943 340 TLC (40% EtOAc in Hexanes), Rf. 150: 0.40 (anisaldehyde) 151: 0.45 (UV, anisaldehyde) 341 H3CXO TMSOTf, 2,6-lutidine, H3C s O a CH2 2, -78 °C HO,,.. H CHO 99% H CHO 12 TIPSO.:· 151 ~ 1 II TMSO,,. 10 152 ]MS ether 15 2 2,6-Lutidine (2.99 mL, 2.75 g, 25.7 mmol, 10 equiv) and trimethylsilyl trifluoromethanesulfonate (2.48 mL, 2.86 g, 12.9 mmol, 5 equiv) were added sequentially via syringe to a solution of enal 151 (1.22 g, 2.57 mmol, 1 equiv) in dichloromethane (51 mL) at -78 °C. The resultant pale yellow solution was maintained at this temperature for an additional 15 min before the excess silyl triflate was quenched by the addition of triethylamine and methanol (10 mL each). The reaction mixture was poured into 1:1 ethyl acetate/hexanes (50 mL) and was washed with water (2 50-mL portions) and saturated aqueous sodium chloride (50 mL). The organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (5% ethyl acetate in hexanes grading to 10% ethyl acetate in hexanes) afforded TMS ether 152 (1.40 g, 99%) as a pale yellow oil. 342 9.80 (s, lH, C8 H), 6.53 (d, lH, J = 1.87 Hz, ClO H), 4.89 (td, lH, J = 6.56, 1.85 Hz, C11 H), 4.10 (dd, lH, J = 8.69, 5.92 Hz, C13 H), 3.91 (m, lH, C14 H), 3.60 (t, lH, J = 6.16 Hz, C14 H), 3.32 (d, lH, J = l.62 Hz, C5 H), 3.26 (dd, lH, J = 12.78, 6.96 Hz, C12 H), 2.47 (dd, lH, J = 12.76, 6.24 Hz, C12 H), 2.08 (d, lH, J = 1.58 Hz, C7 H), 1.44 (s, 3H, C(CH 3)i), 1.18 (s, 3H, C(CH 3) 2), 1.10-0.92 (complex, 21H, OSi(CH(CH 3)2)3), 0.41 (s, 9H, OSi(CH 3) 3). 187.5, 146.8, 146.6, 110.7, 88.5, 79.9, 78.2, 76.9, 75.2, 74.2, 73.5, 66.9, 57.9, 55.6, 50.0, 26.4, 25.1, 18.1, 12.3, 2.0. FTIR (thin film), cm· 1: 3309, (m, C=C-H), 2945 (s), 2867 (s), 2129 (w, C=C), 1699 (s, C=O), 1463 (m), 1350 (m), 1253 (m), 1190 (m), 1073 (s), 882 (s), 846 (s), 684 (m). HRMS (FAB): Calc'd for C29H46 O6Si 2 [Mr: 546.283296 Found: 546.285721 343 TLC (20% EtOAc in Hexanes), Rf. 151: 0.15 (UV, anisaldehyde) 152: 0.36 (UV, anisaldehyde) 344 H3CXO H3C II TMSO,,.. t H CHO s O DIBAL, PhCH 3, -78 °C 96% II t1 TMSO,,.. H 12 TlPSO.:· 152 10 153 Allylic alcohol 1 s3 Diisobutylaluminum hydride (390 µL of a 1.5 M solution in toluene, 0.585 mmol, 2 equiv) was added dropwise via syringe to a solution of aldehyde 152 (160 mg, 0.293 mmol, 1 equiv) in toluene (6 mL) at-78 °C. The reaction was maintained at-78 °C for an additional IO min, and excess reducing agent was quenched by the addition of methanol (1 mL). The reaction mixture was warmed to 0 °C and stirred for 20 min. A 10% aqueous solution of potassium sodium tartrate (5 mL) was added, and the mixture was warmed to 23 °C and stirred vigorously for 20 min. The reaction mixture was poured into water (15 mL) and extracted with ethyl acetate (3 20-mL portions). The combined organics were washed with saturated aqueous sodium chloride (25 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (15% ethyl acetate in hexanes) provided allylic alcohol 153 (155 mg, 96%) as-a colorless oil. 345 5.96 (m, lH, ClO H), 4.98 (m, lH, C11 H), 4.54 (m, 2H, C8 H), 4.04 (dd, lH, J = 8.76, 5.48 Hz, C13 H), 3.78 (dd, 1 H, J = 8.40, 6.56 Hz, C14 H), 3.47 (dd, lH, J = 6.96, 5.84 Hz, C14 H), 3.27 (dd, lH, J = 12.44, 6.96 Hz, C12 BH), 3.21 (d, lH, J = 1.44 Hz, C5 H), 2.45 (dd, lH, J = 12.44, 5.84 Hz, C12 aH), 2.09 (d, lH, J = 1.80 Hz, C7 H), 1.48 (s, 3H, C(CH 3) 2), 1.18 (s, 3H, C(CH 3) 2 ), 1.13-0.94 (complex, 21H, OSi(CH(CH 3)2)3), 0.33 (s, 9H, OSi(CH 3) 3). 148.5, 131.3, 110.7, 89.4, 78.8, 78.3, 77.4, 76.9, 75.2, 73.9, 66.7, 59.0, 57.9, 54.9, 50.3, 26.4, 25.0, 18.2, 12.4, 1.9. FTIR (thin film), cm- 1: 3447 (m, OH), 3310 (m, C=C-H), 2945 (s), 2867 (m), 2133 (w, C=C), 1436 (m), 1372 (m), 1253 (s), 1216 (m), 1075 (s), 881 (s), 846 (s). HRMS (FAB): Calc'd for C29H48 0 6Si 2 [Mt: 548.298947 Found: 548.295807 346 1LC (20% EtOAc in Hexanes), Rf. 152: 0.38 (UV, anisaldehyde) 153: 0.31 (anisaldehyde) 347 (+)-DET, Ti(i-Pr)4 , TBHP, 11 II i 4A MS, CH 2C'2, -78 C TMSO,,,. TMSO,,,. 89'% 7 H 12 TIPSO.: 153 154 Epoxy alcohol t 54 A suspension of 4A molecular sieves (ca. 5 g, powdered, activated) in dichloromethane (65 mL) was cooled to -20 °C. (+)-Diethyl-L-tartrate (5.65 mL, 6.81 g, 33.01 mmol, 12 equiv) and titanium(IV) isopropoxide (8.19 mL, 7.82 g, 27.51 mmol, 10 equiv) were added sequentially via syringe. The mixture was allowed to stir at -20 °C for an additional 50 min, and allylic alcohol 153 (1.51 g, 2.75 mmol, 1 equiv) in dichloromethane (50 mL) was added via cannula over a 10 min period. The resultant mixture was stirred at -20 °C for another 40 min, and tert-butyl hydroperoxide (5.85 mL of a 4.7 M solution in dichloromethane, 27.5 mmol, 10 equiv) was added dropwise through a slit in the septum at the neck of the flask via a gastight syringe equipped with a Teflon needle. The reaction was maintained at -20 °C for 24 h, and the catalyst was quenched by addition of 10% aqueous D-tartaric acid (150 mL). The reaction mixture was warmed to 23 °C and stirred vigorously for 20 min. The reaction mixture was filtered through a plug of celite. The filtrate layers were separated and the aqueous layer was further extracted with dichloromethane (2 100-mL portions). The combined organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography 348 (10% ethyl acetate in dichloromethane grading to 20% ethyl acetate in dichloromethane) afforded epoxy alcohol 154 (1.38 g, 89%) as a colorless oil. 4.41 (d, lH, J =5.84 Hz, Cl 1 H), 4.38 (br s, 2H, C8 H), 4.10 (dd, lH, J = 8.80, 5.52 Hz, Cl3 H), 3.85 (dd, 1 H, J = 8.80, 6.96 Hz, C14 H), 3.73 (s, lH, ClO H), 3.63 (dd, lH, J = 6.60, 5.88 Hz, C14 H), 3.45 (d, lH, J = 1.84 Hz, C5 H), 2.51 (dd, lH, J = 14.28, 5.84 Hz, C12 BH), 2.21 (d, lH, J = 14.64 Hz, C12 aH), 2.06 (d, lH, J = 1.80 Hz, C7 H), 1.89 (br s, lH, OH), 1.50 (s, 3H, C(CH 3)2), 1.28 (s, 3H, C(CH 3)2), 1.15-0.92 (complex, 21H, OSi(CH(CH 3\) 3), 0.40 (s, 9H, OSi(CH 3)3). 110.8, 87.8, 80.1, 78.3, 77.1, 75.4, 74.8, 71.7, 71.6, 66.7, 63.8, 58.0, 57.9, 51.2, 49.9, 26.3, 25.1, 18.1, 12.3, 1.9. 3483 (m, OH), 3271 (m, C:C-H), 2944 (s), 2866 (s), 1462 (m), 1373 (m), 1252 (s), 1213 (m), 1137 (s), 1073 (s), 883 (m), 846 (s). 349 HRMS (FAB): Calc'd for C 29H49 O1Si2 [MHt: 565.301686 Found: 565.301025 153: 0.57 (anisaldehyde) 154: 0.52 (anisaldehyde) 350 II TMSO,,.. iH Dess-Martin periodinane, Py, CH 2C~, 23 °C TMSO,,,. 94% 12 H .,,CHO 0 TIPSO.$. 154 155 Epoxy aldehyde 1 5 5 Dess-Martin periodinane (243 mg, 0.574 mmol, 3 equiv) was added in one portion to a solution of epoxy alcohol 154 (108 mg, 0.191 mmol, 1 equiv) and pyridine (155 µL, 151 mg, 1.91 mmol, 10 equiv) in dichloromethane (3 mL). The resultant pale yellow solution was maintained at 23 °C for 1 h, and the reaction mixture was diluted with diethyl ether (5 mL). Saturated aqueous sodium bicarbonate (5 mL) and saturated aqueous sodium thiosulfate (5 mL) were added sequentially, and the mixture was stirred vigorously until the organic layer was clear (approximately 5 min). The mixture was poured into water (20 mL) and extracted with diethyl ether (3 25-mL portions). The combined organics were washed once with saturated aqueous sodium chloride (30 mL), and were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (15% ethyl acetate in hexanes) afforded epoxy aldehyde 155 (101 mg, 94%) as a colorless oil. 351 9.91 (s, lH, C8 H), 4.26 (d, lH, J = 5.52 Hz, Cl 1 H), 4.05 (dd, lH; J = 8.80, 5.88 Hz, C13 H), 3.85 (dd, 1 H, J = 8.80, 6.96 Hz, C14 H), 3.82 (s, lH, ClO H), 3.61 (t, lH, J = 6.24 Hz, C14 H), 3.33 (d, lH, J = 1.48 Hz, C5 H), 2.38 (dd, lH, J = 14.64, 5.88 Hz, C12 ~H), 2.19 (d, lH, J = 14.28 Hz, C12 aH), 2.08 (d, lH, J = 1.48 Hz, C7 H), 1.46 (s, 3H, C(CH 3) 2), 1.18 (s, 3H, C(CH 3) 2), 1.10-0.91 (complex, 21H, 0Si(CH(CH 3) 2 ) 3), 0.45 (s, 9H, O~i(CH 3)3). 193.1, 110.8, 86.4, 81.0, 78.0, 76.8, 75.5, 73.1, 71.3, 70.7, 67.0, 66.8, 57.9, 51.1, 49.9, 26.3, 25.2, 18.1, 12.2, 1.9. FI1R (thin film), cm-1: 3274 (m, C=C-H), 2946 (s), 2867 (s), 2131 (w, C=C), 1730 (s, C=O), 1462 (m), 1381 (m), 1252 (s), 1141 (s), 1073 (s), 884 (m), 846 (s). HRMS (FAB): Calc'd for C29H41O1Si 2 [MHt: 563.286036 Found: 563.288330 352 154: 0.51 (anisaldehyde) 155: 0.63 (anisaldehyde) 353 II TMSO,,,. i UN(TMS)2 , UCI, .,,CHO 0 TlPSO.: 155 11 THF,-78°C 11 H 62% TlPSO.: 10 156 Cyclic alcohol 15 6 A suspension of dry lithium chloride (2.03 g, 47.9 mmol, 50 equiv) and epoxy alcohol 15S (539 mg, 0.958 mmol, 1 equiv) in tetrahydrofuran (48 mL) was stirred vigorously at 23 'C for 5 min and cooled to -78 °C. Lithium hexamethyldisilazide (2.87 mL of a 1.0 M solution in hexanes, 2.87 mmol, 3 equiv) was added dropwise over a 5 min period to the suspension and the reaction mixture was allowed to stir at -78 'C for an additional IO min. Excess base was quenched by the addition of pH 7 .2 phosphate buffer (10 mL). The mixture was warmed to 23 'C and partitioned between water (20 mL) and 1:1 ethyl acetate/hexanes (20 mL). The layers were separated and the aqueous layer was further extracted with 1:1 ethyl acetate/hexanes (2 25-mL portions). The combined organics were washed once with saturated aqueous sodium chloride (25 mL), and were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (4% ethyl acetate in dichloromethane) afforded cyclic alcohol 1S6 (335 mg, 62%) as a yellow oil. 354 5.36 (d, lH, J = 11.00 Hz, C8 H), 4.18 (d, lH, J = 5.84 Hz, Cl 1 H), 3.89 (dd, lH, J = 8.44, 5.52 Hz, C13 H), 3.79 (s, lH, CIO H), 3.74 (dd, lH, J = 8.44, 6.60 Hz, C14 H), 3.64 (t, lH, J = 5.88 Hz, C14 H), 3.18 (s, lH, C5 H), 2.35 (dd, lH, J = 14.28, 5.88 Hz, C12 ~H), 2.04 (d, lH, J = 14.64 Hz, C12 a.H), 1.89 (d, lH, J = 10.96 Hz, OH), 1.48 (s, 3H, C(CH 3\), 1.23 (s, 3H, C(CH 3)2), 1.09-0.92 (complex, 21H, OSi(CH(CH 3)2)3), 0.36 (s, 9H, C(CH 3) 3). 127.5, 110.7, 92.9, 88.4, 87.6, 86.7, 80.9, 75.2, 70.9, 66.8, 64.1, 61.8, 57.2, 52.5, 48.7, 26.4, 25.5, 18.1, 12.2, 1.8. FI1R (thin film), cm· 1: 3448 (m, OH), 2945 (s), 2867 (s), 2214 (w, C=C), 1463 (m), 1381 (m), 1252 (s), 1217 (m), 1074 (s), 953 (m), 846 (s), 680 (m). HRMS (FAB): Calc'd for C29 H47 0 7 Si 2 [MHt: 563.286036 Found: 563.285300 155: 0.81 (anisaldehyde) 156: 0.75 (anisaldehyde) 355 HO H3C,, 0 H3C,,, 0 14 A. H H3Cxo,·· H3Cxo,•· 5 1% p-TsOH/CH 30H 11 11 2s c 0 11 11 12 ~ TIPSO 156 5 11 + 11 12 TIPSO,.: 10 ~ TIPSO 10 157 158 (62%) (10%) Tetraol 15 7 and diol 15 8 Cyclic alcohol 156 (290 mg, 0.515 mmol, 1 equiv) was dissolved in a 1% solution of p-toluenesulfonic acid in methanol (26 mL) at 23 °C. The resultant solution was maintained at 23 °C for an additional 80 min, during which time the solution gradually became pale yellow. The reaction mixture was neutralized with saturated aqueous sodium bicarbonate (25 mL) and poured into water (20 mL). The mixture was extracted with ethyl acetate (3 15-mL portions). The combined organics were washed with saturated aqueous sodium chloride (20 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (30% ethyl acetate in hexanes grading to 70% ethyl acetate in hexanes) provided tetraol 157 (144 mg, 62%) as a colorless foam and diol 158 (36 mg, 10%) as a yellow oil. 356 For tetraol 157: 5.29 (d, lH, J = 10.96 Hz, C8 H), 4.54 (d, lH, J = 4.36 Hz, Cl 1 H), 3.86 (br m, 2H, C13, C 14 H), 3.71 (m, 3H, C14 H, ClO H, OH), 3.08 (s, lH, CS H), 2.42 (br s, lH, OH), 2.21 (br d, lH, J = 10.80 Hz, OH), 2.18 (dd, lH, J = 14.64, 4.76 Hz, C12 f3H), 2.01 (br s, lH, OH), 1.98 (d, lH, J = 14.64 Hz, C12 aH), 1.21-1.02 (complex, 21H, OSi(CH(CH 3) 2) 3). 92.5, 88.5, 87.2, 87.1, 80.0, 74.8, 71.8, 71.5, 64.1, 63.4, 62.3, 57.0, 52.3, 46.9, 18.3, 12.7. +48.57° (c 0.28, CH3CN) FTIR (thin film), cm- 1: 3380 (s, OH), 2943 (s), 2866 (s), 2214 (w, C=C), 1462 (m), 1384 (m), 1131 (m), 1067 (m), 882 (m), 745 (m). HRMS (FAB): Calc'd for C23H35 0 7 Si [MHr: 451.215207 Found: 451.213867 1LC (70% EtOAc in Hexanes), Rf: 156: 0.77 (anisaldehyde) 157: 0.23 (anisaldehyde) 357 For diol 158: 5.41 (d, lH, J = 10.64 Hz, C8 H), 4.13 (d, lH, J = 4.4 Hz, Cll H), 3.95 (dd, lH, J = 8.80, 5.48 Hz, CB H), 3.75 (dd, lH, J = 8.80, 6.60 Hz, C14 H), 3.68 (s, lH, ClO H), 3.61 (t, lH, J = 6.20 Hz, C14 H), 3.18 (s, lH, Cl OH), 3.02 (s, lH, CS H), 2.21 (dd, lH, J = 14.28, 4.40 Hz, C12 ~H), 1.87 (d, lH, J = 14.28 Hz, C12 aH), 1.79 (d, lJ, J = 10.60 Hz, C8 OH), 1.53 (s, 3H, C(CH 3) 2 ), 1.25 (s, 3H, C(CH 3) 2), 0.95-0.80 (complex, 21H, OSi(CH(CH 3) 2) 3). 110.8, 91.7, 88.4, 87.0, 79.0, 75.5, 74.7, 71.4, 67 .0, 62.4, 61.8, 57 .0, 52.8, 45.8, 26.4, 25.5, 17.9, 12.1. FI1R (thin film), cm· 1: 3441 (m. OH), 2943 (m), 2867 (m), 2279 (w, C=C), 2220 (w, C=C), 1729 (w), 1620 (w), 1463 (m), 1382 (m), 1257 (m), 1217 (m), 1134 (m), 1107 (m), 1070 (m), 882 (m), 682 (m). 1LC (70% EtOAc in Hexanes), Rf. 156: 0.73 (anisaldehyde) 158: 0.65 (anisaldehyde) 358 14 ~ 12 TIPSO,,.. TIPSO .... imidazole, DMF, 23 °C 158 44% ~, Pr i-Pr-Si/O I I 0-Si. I ''i-Pr i-Pr 159 Disiloxane 1 5 9 1,3-Dichloro-1,1,3,3-tetraisopropyldisiloxane (0.026 mL, 26 mg, 0.082 mmol, 5 equiv) was added via syringe to a solution of diol 158 (8.0 mg, 0.016 mmol, 1 equiv) and imidazole (22 mg, 0.33 mmol, 20 equiv) in DMF (0.8 mL) at 23 °C. The reaction mixture was held at 23 °C for an additional 3 h. The solution was poured into saturated aqueous sodium chloride (5 mL) and extracted with 1:1 ethyl acetate/hexanes (3 5-mL portions). The combined organics were dried over sodium sulfate and were concentrated. Purification of the residue by flash column chromatography (10% ethyl acetate in hexanes) was followed by chromatography over Sephadex LH-20 (dichloromethane) to afford the disiloxane 159 (5.3 mg, 44%) as a colorless oil. 359 6.07 (s, lH, C8 H), 4.19 (d, lH, J = 4.76 Hz, Cl 1 H), 3.91 (dd, lH, J = 8.80, 5.84 Hz, C13 H), 3.74 (dd, lH, J = 8.44, 6.96 Hz, C14 H), 3.63 (t, lH, J = 6.20 Hz, C14 H), 3.36 (s, lH, ClO H), 3.16 (s, lH, C5 H), 2.31 (dd, lH, J = 14.28, 4.76 Hz, C12 PH), 1.92 (d, lH, J = 14.28 Hz, C12 a.H), 1.51 (s, 3H, C(CH 3) 2), 1.30-0.84 (complex, C(CH 3 ) 2 , OSi(CH(CH 3) 2) 3, and Si(CH(CH 3) 2) 2). HRMS (FAB): Calc'd for C3sH 65 O8Si 3 [MHt: 733.3987 Found: 733.3991 lLC (30% EtOAc in Hexanes), Rf 158: 0.22 (anisaldehyde) 159: 0.49 (anisaldehyde) 52H, 2 x 360 HO 0 i. COi, THF, o ➔ 23 °c o=< O'' 5 ii. (±)-CSA, 2:1 11 11 H 11 CH3CN/ H20, 23 °C 72% 12 ~ TIPSO 11 ~ TIPSO 10 160 157 Carbonate 1 6 Q Carbonyldiimidazole (37 mg, 0.23 mmol, 0.75 equiv) was added in one portion to a solution of tetraol 157 (135 mg, 0.300 mmol, I equiv) in tetrahydrofuran (10 mL) at 0 0 C. After stirring for an additional 20 min, another portion of carbonyldiimidazole (37 mg, 0.23 mmol, 0.75 equiv) was added. The reaction was kept at 0 CC for an additional 10 min, and warmed to 23 °C for 2.5 h. The reaction mixture was poured into water (10 mL) and extracted with ethyl acetate (3 20-mL portions). The combined organics were dried over sodium sulfate and concentrated. The residue was then taken up in 2: 1 acetonitrile/water (12 mL), and (±)-camphorsulfonic acid (150 mg) was added. The resultant pale yellow solution was maintained at 23 CC for 30 min, and poured into water (20 mL) and extracted with ethyl acetate (3 20-mL portions). The combined organics were washed with saturated aqueous sodium chloride (25 mL) and were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (50% ethyl acetate in hexanes grading to ethyl acetate) provided carbonate 160 (103 mg, 72%) as a colorless foam along with recovered tetraol (31 mg, 23% ). 361 5.36 (d, lH, J = 10.24 Hz, C8 H), 4.07 (d, lH, J = 4.76 Hz, Cl 1 H), 3.69 (dd, lH, J = 7.68, 4.04 Hz, C13 H), 3.65 (s, lH, ClO H), 3.26 (m, 2H, C14 H), 3.06 (s, lH, OH), 2.86 (s, lH, C5 H), 2.04 (dd, lH, J = 14.64, 4.76 Hz, C12 ~H), 1.88 (d, lH, J = 10.60 Hz, OH), 1.74 (d, lH, J = 14.28 Hz, C12 aH), 0.98-0.76 (complex, 21H, OSi(CH(CH 3) 2) 3). 153.9, 94.2, 89.3, 85.9, 84.1, 79.0, 74.8, 74.1, 71.3, 66.2, 62.2, 60.7, 56.9, 53.1, 45.4, 17.9, 12.0. FTIR (thin film), cm-1: 3482 (m, OH), 2944 (s), 2866 (s), 1816 (s, C=O), 1367 (m), 1082 (s), 881 (s). HRMS (FAB): Calc'd for C24H 32 0 8Si [Mt: 476.186647 Found:476.184998 TLC (70% EtOAc in Hexanes), Rf. 157: 0.30 (anisaldehyde) 160: 0.65 (anisaldehyde) 362 0 0 o=<o,,. o=< H 0''' 11 5 TESCI, imidazole, 11 H 11 CH2a2, -78 °C 11 12 97% TIPSO.: .: TIPSO 160 10 161 Triethylsilyl ether 1 61 Triethylsilyl chloride (313 µL, 274 mg, 1.82 mmol, 7 equiv) was added dropwise via syringe to a solution of carbonate 160 (124 mg, 0.260 mmol, 1 equiv) and imidazole (354 mg, 5.20 mmol, 20 equiv) in dichloromethane (13 mL) at 0 °C. The resultant solution was maintained at 0 °C for 10 min and partitioned between 1:1 ethyl acetate/hexanes (25 mL) and water (15 mL). The aqueous layer was further extracted with 1:1 ethyl acetate/hexanes (2 20-mL portions), and the combined organics were washed with saturated aqueous sodium chloride (25 mL), dried over sodium sulfate, and concentrated. Purification of the residue by flash column chromatography (20% ethyl acetate in hexanes) afforded triethylsilyl ether 161 (148 mg, 97%) as a pale yellow oil. 363 5.79 (s, lH, C8 H), 4.09 (d, lH, J = 4.40 Hz, C11 H), 3.87 (s, lH, ClO H), 3.65 (dd, lH, J = 6.96, 3.68 Hz, C13 H), 3.26 (m, 2H, C14 H), 3.13 (s, lH, OH), 2.78 (s, lH, C5 H), 2.14 (dd, lH, J = 14.28, 4.40 Hz, C12 (3H), 1.76 (d, lH, J = 14.64 Hz, C12 aH), 1.06 (t, 9H, J = 8.04 Hz, OSi(CH2CH 3) 3), 0.95-0.81 (complex, 21H, OSi(CH(CH 3) 2) 3), 0.69 (m, 6H, OSi(CH 2CH 3) 3). 153.5, 90.4, 89.8, 85.7, 80.4, 80.0, 74.8, 73.9, 71.6, 65.8, 62.5, 60.4, 57.5, 53.2, 45.7, 17.9, 12.0, 6.9, 5.0. FTIR (thin fihn), cm· 1: 3490 (m, OH), 2954 (s), 2870 (s), 2214 (w, C=C), 1822 (s, C=O), 1469 (m), 1240 (m), 1148 (s), 1104 (s), 881 (m), 727 (m). HRMS (FAB): Calc'd for C30 H47 0 8Si2 [MHt: 591.2810 Found: 591.2809 160: 0.28 (anisaldehyde) 161: 0.83 (anisaldehyde) 364 0 0 o=< o=<o•·· O''' 5 Martin Sulfurane, 11 11 11 CH2Cl 2, 23 °C 11 e 93% TIPSO..: 161 H .,,OTES . TIPSO..: 0 10 162 Olefin 162 A solution of triethylsilyl ether 161 (20 mg, 0.034 mmol, 1 equiv) in dichloromethane (0.85 mL) was added via cannula to a solution of Martin sulfurane dehydrating agent (114 mg, 0.169 mmol, 5 equiv) in dichloromethane (0.85 mL) at 0 °C. The resultant yellow solution was warmed to 23 °C, allowed to stand at that temperature for 1 h, and concentrated. Purification of the residue by flash column chromatography (2% ethyl acetate in dichloromethane) afforded enediyne along with a close running by-product of the sulfurane. A second flash purification by flash column chromatography (20% ethyl acetate in hexanes) afforded pure olefin 162 (18 mg, 93%) as a pale yellow oil. 365 5.94 (t, lH, J = 2.56 Hz, C12 H), 5.07 (s, lH, C8 H), 4.59 (d, lH, J = 2.20 Hz, Cl 1 H), 3.96 (d, lH, J = 2.56 Hz, ClO H), 3.58 (dd, lH, J = 8.44, 5.48 Hz, C13 H), 3.39 (dd, IH, J = 8.04, 5.48 Hz, C14 H), 3.27 (t, IH, J = 8.40 Hz, C14 H), 2.76 (s, IH, C5 H), 1.070.90 (complex, 30H, OSi(CH2CH 3) 3 and OSi(CH(CH 3) 2) 3), 0.67 (m, 6H, OSi(CH 2CH 3) 3). 153.5, 143.5, 96.7, 90.4, 88.4, 86.1, 77 .2, 73.6, 65.8, 62.9, 61.4, 58.6, 52.7, 18.0, 12.3, 6.9, 5.1. FTIR (thin film), cm- 1: 2953 (s), 2870 (s), 2190 (w, C=C), 1823 (s, C=O), 1462 (m), 1323 (m), 1154 (s), 1091 (s), 879 (m), 747 (m). HRMS (FAB): Calc'd for C30 H45 O7Si2 [MHt: 573.2704 Found: 573.2709 1LC (25% EtOAc in Hexanes), Rf. 161: 0.14 (anisaldehyde) 162: 0.25 (UV, anisaldehyde) 366 0 o=<o··· 11 II llPSO.: 162 163 Triol163 A solution of bis-epoxide 162 (1.0 mg, 1.7 x 10-3 mmol, 1 equiv) in tetrahydrofuran (0.1 mL) was added dropwise via cannula to a green solution of dicyclopentadienyltitanium(Ill) chloride (13 µL of a 0.4 M stock solution m tetrahydrofuran prepared by the in situ method of RajanBabu and Nugent,96 5.2 x 10·3 mmol, 3 equiv) in tetrahydrofuran (0.1 mL) at 23 °C. The reaction mixture turned orange upon addition of the alcohol. The solution was maintained at 23 °C for an additional 10 min and pH 7.2 phosphate buffer (1 mL) was added. The mixture was extracted with ethyl acetate (3 1-mL portions) and the combined organics were washed with saturated aqueous sodium bicarbonate (2 mL) and saturated aqueous sodium chloride (2 mL). The organics were dried over sodium sulfate and concentrated to ca. 0.1 mL. Purification of the concentrate by flash column chromatography (20% ethyl acetate in hexanes grading to 50% ethyl acetate in hexanes) was followed by pooling the fractions containing the product and concentrating to a volume of ca. 0.1 mL. A 0.5 mL portion of deuteriated benzene (99.5 atom % D) was added and the resulting solution was concentrated to a volume of ca. 0.1 mL. This procedure was repeated 4 times. After the last iteration, the concentrated 367 solution was taken up in approximately 0.4 mL deuteriated benzene (99.95 atom % D). Analysis of the sample by 1H NMR showed it to contain triol 163. 6.00 (t, lH, J = 2.56 Hz, C12 H), 5.97 (complex, 2H, C4, C5 H), 5.40 (d, lH, J = 2.60 Hz, C8 H), 4.73 (br m, lH, C13 H), 4.62 (d, lH, J = 2.56 Hz, C11 H), 4.16 (br m, 2H, C14 H), 4.11 (d, lH, J = 2.56 Hz, CIO H), 1.08-0.71 OSi(CH(CH FTIR (thin film), cm- 1: ) 3 ) 2 ) 3 (complex, and OSi(CH CH ) 3 H, ). 3 3364 (m, OH), 2924 (s), 1723 (w), 1461 (m), 1093 (m). 1LC (50% EtOAc in Hexanes), Rf. 2 36 162: 0.61 (UV, anisaldehyde) 163: 0.29 (UV, anisaldehyde) 368 0 o=<o•·· 11 11 (±)-CSA, 2:1 acetonitrile/water, 23 °C 11 11 92% npso"' 162 164 Alcohol 164 (±)-Camphorsulfonic acid (214 mg, 0.920 mmol, 5 equiv) was added in one portion to a solution of olefin 162 (105 mg, 0.184 mmol, 1 equiv) in 2:1 acetonitrile/water (6 mL). The resultant yellow solution was stirred at 23 °C for 15 min, and poured into water (15 mL). The mixture was then extracted with ethyl acetate (3 25-mL portions) and the combined organics were washed once with saturated aqueous sodium chloride (30 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (20% ethyl acetate in hexanes grading to 40% ethyl acetate in hexanes) afforded alcohol 164 (77 mg, 92%) as a colorless oil. 369 5.89(t, lH, J =2.20 Hz, C12 H), 4.54 (d, lH, J = 2.20 Hz, Cll H), 4.13 (d, lH, J = 9.12 Hz, C8 H), 3.76 (d, lH, J = 2.20 Hz, ClO H), 3.66 (dd, lH, J = 8.80, 5.12 Hz, C13 H), 3.37 (dd, lH, J = 8.08, 5.12 Hz, C14 H), 3.31 (t, lH, J = 8.44 Hz, C14 H), 2.82 (s, lH, C5 H), 2.14 (d, lH, J = 9.88 Hz, OH), 1.13-0.48 (complex, 21 H, 0Si(CH(CH 3) 2) 3). 153.3, 143.7, 126.6, 96.1, 89.8, 88.0, 85.3, 76.2, 73.6, 73.4, 65.7, 63.5, 61.2, 56.9, 52.7, 17.7, 11.8. FTIR (thin film), cm- 1: 3448 (rn, OH),2943 (s), 2866 (s), 2202 (w, C=C), 1818 (s, C=O), 1463 (m), 1321 (rn), 1154 (s), 1082 (s), 881 (rn). HRMS (FAB): Calc'd for C24H30 O1Si [Mt: 458.176082 Found: 458.177483 1LC (50% EtOAc in Hexanes), Rf. 162: 0.66 (UV, anisaldehyde) 164: 0.44 (UV, anisaldehyde) 370 0 o=< Pflh:i, 12 , imidazole, H CH 2Cl 2 , o °C 11 11 llPSO~ 164 165 TESOTf, 2,6-lutidine, 11 CH 2Cl2, -78 °C II 12 TIPSO.:' OTES 166 Dienediynes 16 5 and 166 Iodine (3.0 mg, 2.2 x 10·2 mmol, 10 equiv) was added in one portion to a solution of triphenylphosphine (7.0 mg, 2.7 x 10·2 mmol, 12 equiv) and imidazole (3.0 mg, 4.4 x 10·2 mmol, 20 equiv) in dichloromethane (0.05 mL) at 0 0 C. The resultant pale yellow suspension was stirred at 0 °C for an additional 5 min, and a solution of alcohol 164 (1 mg, 2.2 x 10·3 mmol, 1 equiv) in dichloromethane (0.2 mL) was added in a dropwise manner. The reaction was monitored by thin-layer chromatography (silica, 50% ethyl acetate in hexanes), and was judged to be complete in 7 min. The reaction mixture was concentrated to ca. one-third of the original volume. The concentrated sample was applied directly to a pipet column packed with 20% ethyl acetate in hexanes, and the product was 371 eluted with a solvent system of 20% ethyl acetate in hexanes grading to 30% ethyl acetate in hexanes. Fractions containing the product were pooled and concentrated to a volume of ca. 0.1 mL. A 0.5 mL portion of deuteriated benzene (99.5 atom % D) was added and the resulting solution was concentrated to a volume of ca. 0.1 mL. repeated 4 times. This procedure was After the last iteration, the concentrated solution was taken up in approximately 0.4 mL deuteriated benzene (99.95 atom % D). Analysis of the sample by 1 H NMR showed it to contain dienediyne 165. The NMR sample was placed in a 10 mL round-bottom flask and concentrated to approximately 0.05 mL. The concentrate was diluted with dry dichloromethane (0.1 mL) and cooled to-78 °C. 2,6-Lutidine (13 µL, 12 mg, 0.11 mmol, 50 equiv) and triethylsilyl trifluoromethanesulfonate (12.5 µL, 15 mg, 5.6 x 10·2 mmol, 25 equiv) were added sequentially via syringe. The reaction was held at -78 °C for an additional 15 min, and warmed to 0 °C. After 10 min at 0 °C, the reaction was diluted with hexanes (2 mL) and washed with water (3 1-mL portions). The organics were dried over sodium sulfate and were concentrated to a volume of ca. 0.1 mL. A 0.5 mL portion of deuteriated benzene (99.5 atom% D) was added and the resulting solution was concentrated to a volume of ca. 0.1 mL. This procedure was repeated 4 times. After the last iteration, the concentrated solution was taken up in approximately 0.4 mL deuteriated benzene (99.95 atom % D). Analysis of the sample by 1H NMR showed it to contain dienediyne 166. 372 For 165: 5.88 (t, lH, J = 1.6 Hz, C12 H), 5.16 (br s, lH, C8 H), 4.37 (t, lH, J = 2.4 Hz, Cl 1 H), 4.08 (br S, OH), 4.06 (br s, lH, ClO H), 3.75 (dd, lH, J = 8.40, 4.76 Hz, C13 H), 3.30 (t, lH, J = 8.44 Hz, C14 H), 3.25 (dd, lH, J = 8.40, 4.76 Hz, C14 H), 3.18 (d, lH, J = 1.3 Hz, C5 H), 1.10-0.82 (complex, 21 H, OSi(CH(CH 3) 2) 3). FTIR (thin film), cm- 1: 3401 (m, OH), 2923 (s), 1807 (m, C=O), 1530 (m), 1085 (m). 1LC (50% EtOAc in Hexanes), Rf 164: 0.40 (UV, anisaldehyde) 165: 0.49 (UV, anisaldehyde) 373 For 166: 6.04 (br s, lH, C12 H), 5.51 (br s, lH, C8 H), 4.67 (t, lH, J = 2.6 Hz, Cl 1 H), 4.47 (t, lH, J = 2.6 Hz, ClO H), 3.73 (m, lH, C13 H), 3.28 (m, 2H, C14 H), 3.10 (d, lH, J = 1.7 Hz, CS H), 1.12-0.50 (complex, 21 H, OSi(CH(CH 3) 2) 3). 1LC (50% EtOAc in Hexanes), Rf. 165.: 0.49 (UV, anisaldehyde) 166: 0.61 (UV, anisaldehyde) 374 5 (QCH 2COl:!O, pyridine, 11 CH2Cl2 , O °C 11 11 H 11 s -.. H ~ Cl 0 0 81% ,~ TIPSO .: TIPSO 164 10 167 Chloroacetate 16 7 Chloroacetic anhydride (216 mg, 1.26 mmol, 10 equiv) was added in one portion to a solution of alcohol 164 (58 mg, 0.13 mmol, 1 equiv) and pyridine (205 µL, 200 mg, 2.538 mmol, 20 equiv) in dichloromethane (3.0 mL) at 0 °C. The reaction was maintained at 0 °C for an additional 10 min, diluted with 1:1 ethyl acetate/hexanes (10 mL) and washed with water (3 5-mL portions) and saturated aqueous sodium chloride (5 mL). The organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (5% ethyl acetate in hexanes grading to 50% ethyl acetate in hexanes) provided chloroacetate ester 167 (54 mg, 81 %) as a yellow oil. 375 5.91 (t, lH, J = 2.60 Hz, C12 H), 5.68 (s, lH, C8 H), 4.56 (d, lH, J = 2.56 Hz, Cll H), 3.89 (d, lH, J = 2.56 Hz, ClO H), 3.61 (dd, lH, J = 8.40, 5.12 Hz, C13 H), 3.37 (dd, lH, J = 8.44, 5.12 Hz, C14 H), 3.30 (t, lH, J = 8.40 Hz, C14 H), 3.18 (abq, 2H, J = 15.97 Hz, l:!i.v = 17.28 Hz, COCH2Cl), 2.73 (s, lH, C5 H), 1.02-0.91 (complex, 21H, OSi(CH (CH 3) 2) 3). 165.4, 153.4, 144.3, 127.1, 96.5, 88.9, 88.1, 85.6, 74.2, 73.8, 73.6, 65.9, 64.1, 61.5, 59.6, 52.7, 39.8, 17.6, 12.3. FI1R (thin film), cm- 1: 2944 (m), 2872 (m), 2202 (w, C=C), 1819 (s, carbonate C=O), 1772 (m, ester C=O), 1466 (w), 1325 (w), 1249 (w), 1151 (s), 1078 (s), 996 (m), 881 (m). HRMS (FAB): Calc'd for C26H32ClO8Si [MHr: 535.155500 Found: 535.153870 TLC (40% EtOAc in Hexanes), Rf 164: 0.32 (UV, anisaldehyde) 167: 0.43 (UV, anisaldehyde) 376 II 11 0 HF-pyridine, CH 3 CN, 23 °C II II 0 e H II ·,,~.Jl_,c1 0 0 HO,. TIPSO~ 167 •,, ~ C I 0 10 168 II 9% (two steps) 11 0 e H II .. ·,, ~ C I O 0 Allylic alcohol 168 and naphthoate ester 169 Hydrogen fluoride - pyridine complex (1 mL) was added to a solution of chloroacetate ester 167 (110 mg, 0.206 mmol, 1 equiv) in acetonitrile (9 mL) at 23 °C. The resultant orange-brown solution was stirred at 23 °C for an additional 2 h, during which time the solution darkened considerably. The reaction mixture was poured into water (25 mL) and extracted with ethyl acetate (3 20-mL portions). The combined organics were dried over sodium sulfate and concentrated to a volume of ca. 3 mL. The crude alcohol 168 was taken up in dichloromethane (21 mL) and cooled to 0 °C. 2-Hydroxy-7methoxy-5-methyl-l-naphthoic acid (22, 287 mg, 1.24 mmol, 6 eq) was added in one 377 portion followed by 1-(3-dimethylarninopropyl)-3-ethylcarbodiimide (EDC) (355 mg, 1.85 mmol, 9 equiv), also in one portion. The reaction was maintained at 0 °C for 30 min, then another portion of EDC (150 mg, 0.782 mmol, 3.7 equiv) was added. Stirring was continued for an additional 30 min, and the reaction mixture was poured into a bilayer of ethyl acetate (10 mL) and water (10 mL). The layers were separated and the aqueous layer was further extracted with ethyl acetate (2 10-mL portions). The combined organics were washed with saturated aqueous sodium chloride (25 mL), and were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (25% ethyl acetate in hexanes grading to 50% ethyl acetate in hexanes) provided naphthoate ester 169 (11.2 mg, 9% two-step yield) as a colorless film along with recovered alcohol 168 (17 mg, 23%) as an orange oil. 378 For alcohol 168: 5.83 (s, lH, C8 H), 5.58 (t, lH, J = 2.56 Hz, C12 H), 3.99 (hr s, lH, Cl 1 H), 3.51 (dd, lH, J = 8.80, 5.48 Hz, C13 H), 3.45 (d, lH, J = 2.56 Hz, CIO H), 3.37 (dd, lH, J = 8.04, 5.48 Hz, C14 H), 3.23 (m, 3H, C14 H and CH 2Cl), 2.71 (s, lH, C5 H). FTIR (thin film), cm·1: 3448 (m, OH), 2919 (m), 2202 (w, C=C), 1813 (s, carbonate C=O), 1791 (s, ester C=O), 1401 (w), 1307 (m), 1249 (w), 1154 (s), 1080 (s}, 995 (m) 868 (m), 767 (m). HRMS (FAB): Calc'd for C17H 12ClO7 [Mr: 363.027156 Found: 363.027054 lLC (70% EtOAc in Hexanes), Rf: 167: 0.66 (UV, anisaldehyde) 168.: 0.41 (fluoresces under UV, anisaldehyde) 379 For 169: 12.58 (s, lH, C2" OH), 8.00 (s, lH, C8" H), 7.70 (d, lH, J = 9.16 Hz, C4" H), 7.14 (d, lH, J= 9.16 Hz, C3" H), 6.99 (s, lH, C6" H), 5.75 (t, lH, J = 2.20 Hz, C12 H), 5.69 (s, lH, C8 H), 5.47 (d, lH, J = 2.20 Hz, C11 H), 3.72 (d, lH, J = 2.56 Hz, ClO H), 3.66 (s, 3H, CT' OCH 3), 3.49 (dd, lH, J = 8.80, 5.52 Hz, C13 H), 3.36 (dd, lH, J = 8.04, 5.48 Hz, C14 H), 3.23 (t, lH, J = 8.76 Hz, C14 H), 3.18 (abq, 2H, J = 14.64 Hz, Av = 23.80 Hz, COCH 2Cl), 2.71 (s, lH, C5 H), 2.23 (s, 3H, C5" CH 3). 171.7, 166.1, 165.5, 160.0, 153.7, 139.9, 137 .8, 134.2, 133.9, 130.6, 123.4, 117 .0, 116.2, 104.1, 97.9, 89.0, 87.1, 84.8, 75.1, 74.3, 67.0, 61.6, 61.4, 61.3, 59.4, 55.4, 53.0, 40.9, 30.0, 20.1. -126.90° (c 0.29, CH 3CN) FTIR (thin film), cm· 1: 2927 (m), 1819 (s, C=O), 1648 (m), 1616 (s), 1411 (m), 1257 (m), 1201 (s), 1150 (s), 1079 (m). 380 HRMS (FAB): Calc'd for C 30H 22ClO11 [MHt: 593.085065 Found: 593.084457 lLC (70% EtOAc in Hexanes), Rf 168: 0.46 (UV, anisaldehyde) 169: 0.68 (fluoresces under UV, anisaldehyde) 381 0 o=< O''' II 11 ·,, H)l_,c1 00 11 0 aq. NaHC03 , CH 3OH, o °C ~ 0 0 11 H3CO~OH ~ 169 CH3 o oi 50% H 3 C O W'<::: 8 ' OH :::::,... I ~ 4• CH3 120 Epoxy alcohol 12 Q Sodium bicarbonate (13 mg, 0.16 mmol, 10 equiv) was added to a solution of ester 169 (9.2 mg, 0.016 mmol, 1 equiv) in methanol (1.6 mL) at 0 0 C. The resultant suspension was stirred at 0 °C for an additional 60 minutes, then was diluted with ethyl acetate (10 mL). The reaction mixture was washed with water (3 5-mL portions) and saturated aqueous sodium chloride (5 mL). The organics were dried over sodium sulfate and were concentrated. Purification of the residue by flash column chromatography (10% ethyl acetate in dichloromethane grading to 20% ethyl acetate in dichloromethane) afforded the epoxy alcohol 120 (4.1 mg, 50%) as a yellow film. 382 12.57 (s, lH, C2" OH), 7.98 (s, lH, C8" H), 7.70 (d, lH, J = 9.16 Hz, C4" H), 7.15 (d, lH, J = 9.52 Hz, C3" H), 6.98 (s, lH, C6" H), 5.69 (t, lH, J = 2.56 Hz, C12 H), 5.47 (d, lH, J = 2.56 Hz, Cl 1 H), 4.40 (d, lH, J = 10.28 Hz, C8 H), 3.64 (d, lH, J = 2.56 Hz, ClO H), 3.53 (dd, lH, J = 8.80, 5.48 Hz, C13 H), 3.50 (s, 3H, CT' OCH 3), 3.34 (dd, lH, J = 8.04, 5.48 Hz, C14 H), 3.23 (t, lH, J = 8.40 Hz, C14 H), 2.77 (s, lH, C5 H), 2.24 (s, 3H, C5" CH 3), 1.84 (d, lH, J = 10.28 Hz, OH). 171.8, 164.3, 160.5, 155.0, 140.1, 138.4, 134.9, 134.0, 131.7, 123.9, 117.7, 116.4, 105.7, 104.4, 99.1, 90.2, 86.9, 86.2, 77.6, 75.9, 75.3, 67.1, 61.8, 61.2, 57.6, 57.2, 53.5, 19.9. 3684 (m, OH), 3070 (m), 3036 (m), 2957 (m), 1823 (s, C=O), 1732 (w), 1649 (w), 1611 (m), 1478 (s), 1199 (m), 1035 (m). 383 HRMS (FAB): Calc'd for C 28H21 O 10 [MHt: 517.1135 Found: 517.1137 TLC (40% EtOAc in CH2Cli), Rf. 169: 0.71 (fluoresces under UV, anisaldehyde) 120: 0.49 (fluoresces under UV, anisaldehyde) 384 5 11 11 II 11 PPh:3, 12 , imidazole, CH 2a 2 , -15 °C d o H3 C O ~ O H YlJ CH3 f 0 OH H3COW---:::: "'--:::: OH I h 120 0 h 4• CH3 6 Neocarzinostatin chromophore aglycone (6) Epoxy alcohol 120 (0.6 mg, 1 x 10·3 mmol, 1 equiv) in dichloromethane (0.1 mL) was added via cannula to a pale yellow suspension of triphenylphosphine (7.5 mg, 2.9 x 10·2 mmol, 25 equiv), imidazole (3.9 mg, 5.7 x 10·2 mmol, 50 equiv) and iodine (7.2 mg, 2.9 x 10·2 mmol, 25 equiv) in dichloromethane (0.1 mL) at -15 °C. The reaction mixture was maintained at -15 °C for an additional 30 min, and the reaction mixture was loaded directly onto a pipet column packed with silica gel and 20% ethyl acetate in dichloromethane. Elution with the same solvent system was followed by pooling the fractions containing the aglycone 6. The collected fractions were concentrated to a small volume (ca. 0.1 mL), and the concentrate taken up in methanol (1.0 mL). The yield of neocarzinostatin chromophore aglycone was determined by UV absorption using the extinction coefficient determined for neocarzinostatin chromophore (e 302 = 7040 M-1 cm -!) . By this method, the amount of neocarzinostatin chromophore aglycone (6) isolated was 3 x 10·4 mmol, or 22% of theoretical. 385 11.69 (s, lH, C2" OH), 8.14 (d, lH, J = 9.52 Hz, C4" H), 7.99 (br s, lH, C8" H), 7.07 (d, lH, J =9.16 Hz, C3" H), 6.95 (br s, lH, C6" H), 6.65 (br s, lH, C12 H), 6.30 (t, lH, J = 2.56 Hz, Cl 1 H), 5.69 (br s, lH, C8 H), 4.92 (m, lH, ClO H), 4.90 (dd, lH, J = 8.44, 5.48 Hz, C13 H), 4.62 (t, lH, J = 8.80 Hz, C14 H), 4.39 (dd, lH, J = 8.76, 5.12 Hz, C14 H), 4.24 (d, lH, J = 5.16 Hz, OH), 4.06 (d, lH, J = 1.44 Hz, C5 H), 3.85 (s, 3H, C7'' OCH3), 2.62 (s, 3H, C5" CH 3). -58.90° (c 0.146, CH 3OH) 3684 (m, OH), 3624 (w, OH), 3060 (m), 2938 (m), 2178 (w, C=C), 1820 (s, carbonate C=O), 1733 (m, ester C=O), 1614 (s), 1466 (m), 1413 (m), 1376 (m), 1309 (m), 1244 (m), 1203 (vs), 1082 (s), 1018 (s). 120: 0.49 (fluoresces under UV, anisaldehyde) 6: 0.60 (UV, anisaldehyde) 386 H3C,,, 0 H3Cxo••· 11 i TMSO,,. H Ai. ,CH 3 .Si-CH3 Lil'! .Si-CH \ 3 Al CH 3 , LiCI, 14 H3CXO H3C 0'' 5 11 11 8 12 ~ THF,-78 °C TBSO 138 79% 0 TBSO~ ··, H OH 10 139 Cyclic alcohol 13 9 (improved procedure) Lithium diphenyltetramethyldisilazide (1.78 mL of a 1.0 M solution in hexanes/THF, 1.78 mmol, 2.0 equiv) was added dropwise via syringe to a rapidly stirring suspension of epoxy aldehyde 138 (463 mg, 0.891 mmol, 1 equiv) and lithium chloride (1.89 g, 44.53 mmol, 50 equiv) in tetrahydrofuran (45 mL) at -78 °C. The reaction mixture was stirred at-78 °C for 5 min, and excess base was quenched by the addition of aqueous pH 7.2 phosphate buffer (20 mL). The reaction was warmed to 23 °C, the layers were separated, and the aqueous layer was further extracted with 1: 1 ethyl acetate/hexanes (2 20-mL portions). The combined organics were washed with saturated aqueous sodium chloride (20 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (20% ethyl acetate in hexanes) provided cyclic alcohol 139 (368 mg, 79%) as a yellow oil. 387 5.35 (d, lH, J = 10.60 Hz, C8 H), 4.18 (d, lH, J = 5.84 Hz, Cl 1 H), 3.88 (dd, lH, J = 8.76, 5.84 Hz, C13 H), 3.74 (dd, lH, J = 8.40, 6.60 Hz, C14 H), 3.66 (s, lH, ClO H), 2.65 (t, lH, J = 6.20 Hz, C14 H), 3.18 (s, lH, C5 H), 2.27 (dd, lH, J = 14.28, 5.84 Hz, C12 ~H), 1.93 (d, lH, J = 14.28 Hz, C12 aH), 1.87 (d, lH, J = 11.00 Hz, OH), 1.48 (s, 3H, C(CH 3) 2), 1.23 (s, 3H, C(CH 3) 2 ), 0.91 (s, 9H, OSiC(CH 3) 3)(CH 3) 2), 0.36 (s, 9H, OSi(CH) 3), -0.023 (s, 6H, OSiC(CH 3) 3)(CH 3) 2), -0.026 (s, 6H, OSiC(CH 3) 3)(CH 3) 2). 100.7, 92.9, 88.3, 87.6, 86.7, 80.8, 75.1, 70.68, 66.8, 64.0, 61.8, 57.2, 52.4, 48.2, 26.3, 25.9, 25.5, 18.2, 1.8, -4.8. FTIR (thin film), cm· 1: 3448 (m, OH), 2954 (s), 2860 (m), 2214 (w, C=C), 1373 (m), 1252 (s), 1135 (s), 1075 (s), 953 (m), 843 (s). HRMS: Calc'd for C26H39O7 Si 2 [M-Ht: 519.223436 Found: 519.222949 388 138: 0.69 (anisaldehyde) 139: 0.60 (anisaldehyde) 389 H3C, 0 H3CXO H3Cxo,•• (CICH 2 COl2O, Py, II TBSO 139 o••· 5 II II CH 2 Cl2 , 0 °C 11 H 89"/o .: H3 C 14 o e ·, H ~ Cl 0 12 0 ~ TBSO 10 170 Chloroacetate 17o Chloroacetic anhydride (706 mg, 4.12 mmol, 5 equiv) was added in one portion to a solution of cyclic alcohol 139 (430 mg, 0.826 mmol, 1 equiv) and pyridine (0.688 mL, 653 mg, 8.26 mmol, 10 equiv) in dichloromethane (17 mL) at 0 0 C. The resultant pale yellow solution was stirred at 0 CC for 10 minutes, then diluted with 1: 1 ethyl acetate/hexanes (20 mL). The mixture was washed with water (20 mL) and saturated aqueous sodium chloride (20 mL). The organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (15% ethyl acetate in hexanes) provided chloroacetate ester 170 (440 mg, 89%) as a yellow oil. 390 6.59 (s, lH, CS H), 4.22 (d, lH, J = 5.88 Hz, Cl 1 H), 3.83 (dd, lH, J = 8.76, 5.84 Hz, C13 H), 3.80 (s, lH, ClO H), 3.70 (dd, lH, J = 8.44, 6.56 Hz, C14 H), 3.62 (t, lH, J = 6.24 Hz, C14 H), 3.17 (abq, 2H, llv = 14.32 Hz, J = 14.64 Hz, CH 2Cl), 3.06 (s, lH, CS H), 2.30 (dd, lH, J = 14.28, 5.88 Hz, C12 ~H), 1.96 (d, lH, J = 14.28 Hz, C12 aH), 1.48 (s, 3H, C(CH 3) 2 ), 1.24 (s, 3H, C(CH 3) 2 ), 0.92 (s, 9H, OSiC(CH 3)/CH 3) 2), 0.38 (s, 9H, OSi(CH 3) 3), 0.012 OSiC(CH 3)/CH 3) 2), -0.012 (s, 3H, (s, 3H, OSiC(CH 3)/CH 3) 2). 165.2, 110.7, 92.1, 89.6, 87.5, 84.1, 79.2, 75.4, 75.0, 70.9, 66.6, 64.7, 61.5, 59.8, 52.2, 48.0, 40.0, 26.3, 25.9, 25.5, 18.1, 1.7, -4.7, -4.8. FI1R (thin film), cm·': 2954 (m), 2895 (m), 1775 (m, C=O), 1372 (w), 1253 (s), 1216 (m), 1138 (s), 1074 (s), 955 (m), 843 (s). 391 HRMS (FAB): Calc'd for C28 H40ClO 8Si2 [M-Ht: 595.195028 Found: 595.196716 TLC (30% EtOAc in Hexanes), Rf. 139: 0.37 (anisaldehyde) 170: 0.46 (anisaldehyde) 392 El:3N•3HF, CH 3 CN, 23 °C II 11 a 83% 0 TBSO..: 170 .:· HO 0 ·., ..........___,,c1 0 H II 10 171 Diol 171 Triethylamine trihydrofluoride (0.668 mL, 661 mg, 4.10 mmol, 10 equiv) was added via syringe to a solution of chloroacetate ester 170 (245 mg, 0.410 mmol, 1 equiv) in acetonitrile (8 mL) at 23 °C. The reaction was maintained at 23 °C for an additional 2 h, and then partitioned between 1:1 ethyl acetate/hexanes (20 mL) and water (20 mL). The aqueous layer was further extracted with 1:1 ethyl acetate/hexanes (2 15-mL portions) and the combined organics were washed with saturated aqueous sodium chloride (20 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (50% ethyl acetate in hexanes) afforded diol 171 (140 mg, 83%) as a white foam. 393 6.31 (s, lH, C8 H), 4.40 (d, lH, J = 5.16 Hz, Cl 1 H), 4.15 (dd, lH, J = 8.44, 6.24 Hz, C13 H), 4.13 (s, 2H, CH 2CI), 4.03 (t, lH, J = 6.24 Hz, C14 H), 3.98 (dd, lH, J = 8.44, 5.12 Hz, C14 H), 3.70 (s, lH, ClO H), 3.63 (s, lH, C5 H), 2.16 (dd, lH, J = 15.00, 5.12 Hz, C12 J3H), 1.98 (d, lH, J = 14.68 Hz, C12 aH), 1.45 (s, 3H, C(CH 3) 2), 1.33 (s, 3H, C(CH 3) 2). 166.6, 111.0, 91.3, 89.8, 87.2, 84.4, 77 .5, 74.8, 74.3, 70.4, 66.5, 63.3, 61.7, 59.8, 52.6, 45.1, 40.6, 26.3, 25.4. FTIR (thin film), cm· 1: 3440 (s, OH), 2989 (m), 2951 (m), 2222 (w, C=C), 1767 (s, C=O), 1381 (m), 1256 (m), 1217 (m), 1150 (s), 1072 (s), 952 (m), 848 (m). 1LC (70% EtOAc in Hexanes), Rf 170: 0.74 (anisaldehyde) 171: 0.36 (anisaldehyde) 394 II II HO 0 ·-, ~ C I 0 i. 22, DCC, THF, 0 °C 11 ii. n-PrNH 2 11 12 71% ~ 0 171 0 ~ H3COW8" OH ~ I '° 4• CH3 172 Naphthoate ester 1 7 2 Dicyclohexylcarbodiimide (414 mg, 2.01 mmol, 5 equiv) was added in one portion to a solution of diol 171 (165 mg, 0.402 mmol, 1 equiv) and naphthoate 22 (280 mg, 1.20 mmol, 3 equiv) in tetrahydrofuran (8 mL) at 0 °C. The solution was maintained at this temperature for 1 h, and precipitated dicyclohexylurea was removed by filtration, and the filtrate concentrated in vacuo. Purification of the residue by flash column chromatography (10% ethyl acetate in hexanes grading to 50% ethyl acetate in hexanes) afforded naphthoate ester and naphthoate diester (194 mg) as a 6:1 mixture as determined by integration of the 1 H NMR spectrum (158 mg monoester, 71 %, and 36 mg diester, 12%). The monoester could be isolated cleanly as a pale yellow film after a second chromatography (10% ethyl acetate in hexanes grading to 50% ethyl acetate in hexanes), but purification could be more easily accomplished subsequent to the next reaction. 395 1 H NMR (400 MHz, DMSO-d6 ) o: 10.56 (s, lH, C2" OH), 7.94 (d, lH, J = 9.16 Hz, C4" H), 7.18 (d, lH, J = 2.16 Hz, C8" H), 7.02 (d, lH, J = 9.16 Hz, C3" H), 6.87 (s, lH, C6" H), 6.42 (s, lH, Cl 1 H), 5.52 (d, lH, J = 6.24 Hz, C8 H), 5.15 (br d, lH, J = 3.64 Hz, OH), 4.09 (dd, lH, J = 8.80, 6.96 Hz, C13 H), 4.02 (dd, lH, J = 6.96, 4.40 Hz, C14 H), 3.90 (s, 2H, C5, ClO H), 3.80 (s, 3H, C7: OCH 3), 3.76 (dd, lH, J = 8.76, 3.96 Hz, C14 H), 2.54 (s, 3H, C5" H), 2.24 (dd, lH, J = 15.40, 6.24 Hz, C12 PH), 2.13 (d, lH, J = 15.36 Hz, C12 cxH), 1.41 (s, 3H, C(CH 3)2), 1.27 (s, 3H, C(CH 3)2). 13 C NMR (100 MHz, DMSO-d6 ), o: 168.0, 158.4, 156.5, 136.5, 133.0, 129.4, 122.0, 116.5, 115.2, 110.3, 109.8, 101.1, 92.7, 88.8, 85.5, 85.2, 80.2, 74.4, 72.3, 72.0, 67.8, 61.0, 60.5, 55.2, 43.1, 26.0, 25.0, 19.1. +32.58° (c 0.85, CH 3OH) FTIR (thin film), cm· 1: 3201 (m, OH), 2979 (m), 2931 (m), 1639 (m), 1614 (s, C=O), 1411 (m), 1375 (m), 1250 (m), 1206 (vs), 1024 (s), 847 (m) cm· 1 396 HRMS (FAB): Calc'd for C30H29 O10 [MHt: 549.1761 Found: 549.1755 1LC (50% EtOAc in Hexanes), Rf 171: 0.55 (anisaldehyde) 172: 0.40 (fluoresces under UV, anisaldehyde) 397 5 11 11 11 1% p-TsOH/CH 3OH, 11 23 °c d 67'% o ~ H3COWEr OH ~ CH3 '~ 4• 173 Pentaol 173 p-Toluenesulfonic acid (30 mg, 1% w/v relative to CH 3OH) was added in one portion to a solution of ester 172 (33 mg, 0.0602 mmol, 1 equiv) in methanol (3 mL). The resultant yellow solution was stirred at 23 °C for an additional 1.5 h and then diluted with ethyl acetate (5 mL). The reaction mixture was washed with water (2 5-mL portions) and saturated aqueous sodium chloride (5 mL), dried over sodium sulfate, and concentrated in vacuo. Purification of the residue by flash column chromatography (2% methanol in dichloromethane grading to 10% methanol in dichloromethane) afforded the pentaol 1 7 3 (20 mg, 67%) as a colorless film as well as recovered ester (7 mg, 23% ). 398 1 H NMR (400 MHz, CD 3CN) 8: 8.05 (d, lH, J = 9.12 Hz, C4" H), 8.01 (s, lH, C8" H), 6.97 (d, lH, J = 9.16 Hz, C3" H), 6.86 (s, lH, C6" H), 5.60 (d, lH, J = 5.88 Hz, Cl 1 H), 5.20 (s, lH, C8 H), 3.99 (s, lH, ClO H), 3.84 (s, 3H, C7'' OCH 3), 3.68 (s, lH, C5 H), 3.67-3.49 (complex, 4H, C13, C14 H, OH), 3.26 (s, lH, OH), 2.55 (s, 3H, C5" CH 3), 2.37 (dd, lH, J = 15.76, 5.88 Hz, C12 ~H), 2.25 (d, lH, J = 15.76 Hz, C12 aH). 171.6, 164.3, 160.6, 138.2, 135.2, 133.7, 117.8, 116.6, 106.0, 104.3, 92.1, 88.1, 87.7, 87.5, 80.7, 74.0, 71.5, 64.0, 62.3, 61.5, 61.0, 57.0, 56.1, 52.3, 44.0, 19.9, 14.5. +44.99° (c 1.067, CH3CN) FTIR (thin film), cm·': 3382 (m, OH), 2931 (m), 1614 (s, C=O), 1410 (m), 1378 (m), 1307 (m), 1246 (m), 1206 (s), 1092 (m). HRMS (FAB): Calc'd for C27 H25 0 10 [MHt: 509.1448 Found: 509.1443 399 n.c (70% EtOAc in Hexanes), Rf. 172: 0.66 (fluoresces under UV, anisaldehyde) 173: 0.17 (fluoresces under UV, anisaldeh yde) 400 i. COi, THF, 0 ➔ 23 °C; 11 11 H ••,OH 0 0~ ii. (±)-CSA, 2: 1 11 11 CH3CN/H 2O, 23 °C 67% 0 H3CO~OH ~ 173 CH3 Carbonate 1 7 4 Carbonyldiimidazole (19 mg, 0.011 mmol, 1 equiv) was added in one portion to a solution of pentaol 173 (58 mg, 0.011 mmol, 1 equiv) in dry THF (3.8 mL) at 0 °C. The resultant solution was stirred at 0 °C for 20 min, and then another portion of carbonyldiimidazole (19 mg, 0.011 mmol, 1 equiv) was added. The reaction mixture was maintained at 0 °C for an additional 10 min, then warmed to 23 °C and held at that temperature for 2 h. The reaction mixture was then diluted with ethyl acetate (10 mL) and washed with water (2 5-mL portions) and saturated aqueous sodium chloride (5 mL). The organics were dried over sodium sulfate and concentrated. The residue was then dissolved in 2:1 acetonitrile/water (2 mL). (±)-Camphorsulfonic acid (20 -mg) was added in one portion, and the reaction mixture stirred at 23 °C for 30 min. The reaction mixture was then diluted with ethyl acetate (15 mL) and washed with water (3 5-mL portions) and saturated aqueous sodium chloride (5 mL). The organics were dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (40% ethyl 401 acetate in hexanes grading to 100% ethyl acetate) provided the carbonate 174 (41 mg, 67%) as a colorless film as well as recovered pentaol 173 (17 mg, 29% ). 8.07 (d, lH, J = 9.12 Hz, C4" H), 8.01 (s, lH, C8" H), 6.99 (d, lH, J = 9.16 Hz, C3" H), 6.88 (s, lH, C6" H), 5.63 (d, lH, J = 5.84 Hz, Cll H), 5.23 (s, lH, C8 H), 4.78 (dd, lH, J = 8.40, 5.48 Hz, CB H), 4.56 (t, lH, J = 8.40 Hz, C14 H), 4.30 (dd, lH, J = 8.80, 5.16 Hz, C14 H), 4.03 (s, lH, ClO H), 3.85 (s, 3H, CT' OCH 3), 3.84 (s, lH, C5 H), 2.56 (s, 3H, C5" CH 3), 2.38 (dd, lH, J = 15.36, 5.48 Hz, C12 ~H), 2.29 (d, lH, J = 15.36 Hz, C12 aH), 2.18 (br s, lH, OH) 13 C NMR (100 MHz, CD 3CN), o: 171.6, 164.4, 160.6, 155.1, 138.2, 135.1, 133.7, 123.9, 117.8, 116.6, 105.9, 104.3, 94.4, 89.3, 86.0, 84.8, 80.8, 75.4, 73.9, 73.8, 67.1, 61.7, 61.1, 56.9, 56.1, 53.6, 43.9, 19.9. +18.22° (c 0.933, CH 3CN) 402 FflR (thin film), cm· 1: 3410 (m, OH), 2926 (m), 1817 (s carbonate C=O), 1641 (s), 1615 (s, ester C=O), 1412 (m), 1376 (m), 1310 (m), 1250 (m), 1206 (s), 1081 (s), 962 (w), 847 (m). HRMS (FAB): Calc'd for C 2sH23O 11 [MHt: 535.1240 Found: 535.1234 1LC (70% EtOAc in Hexanes), Rf. 173: 0.14 (fluoresces under UV, anisaldehyde) 174: 0.46 (fluoresces under UV, anisaldehyde) 403 11 11 11 H d o HaCO~OH Bis-TES ether 1 7 o.:· 90% o ~ H3COWEr OTES ~ fyU CHa 11 TESOTf, 2,6-lutidine, CH 2Cl2, -78 °C I h 4• 174 CHa 175 s 2,6-Lutidine (0.229 mL, 210 mg, 1.96 mmol, 12 equiv) and triethylsilyl trifluoromethanesulfonate (0.185 mL, 216 mg, 0.818 mmol, 5 equiv) were added sequentially via syringe to a solution of carbonate 174 (87 .5 mg, 0.163 mmol, 1 equiv) in dichloromethane (8 mL) at-78 cc_ The resultant solution was stirred at -78 cc for 10 min, and then excess triethylsilyl trifluoromethanesulfonate was quenched by the addition of triethylamine (1 mL) and methanol (1 mL). The reaction mixture was warmed to 23 cc, diluted with 1:1 ethyl acetate/hexanes (25 mL), and washed with water (10 mL) and saturated aqueous sodium chloride (10 mL). The organics were dried over sodium sulfate and were concentrated. Purification of the residue by flash column chromatography (20% ethyl acetate in hexanes grading to 50% ethyl acetate in hexanes) afforded bis-TES ether 17S ( 112 mg, 90%) as a colorless oil. 404 7.57 (d, lH, J = 9.16 Hz, C4" H), 7.23 (s, lH, C8" H), 6.98 (s, lH, C6" H), 6.86 (d, lH, J = 9.12 Hz, C3" H), 5.73 (d, lH, J = 5.88 Hz, Cl 1 H), 5.57 (s, lH, C8 H), 4.20 (s, lH, ClO H), 3.60 (s, 3H, C7'' OCH 3), 3.52 (dd, lH, J = 8.44, 5.84 Hz, C13 H), 3.47 (dd, lH, J = 8.04, 5.84 Hz, C14 H), 3.30 (t, lH, J = 8.04 Hz, C14 H), 2.77 (s, lH, C5 H), 2.49 (dd, lH, J = 15.76, 5.84 Hz, C12 PH), 2.30 (s, 3H, C5" CH 3), 2.28 (d, lH, J = 15.76 Hz, C12 aH), 1.04 (t, 9H, J = 8.04 Hz, OSi(CH 2CH 3) 3), 0.97 (t, 9H, J = 8.04 Hz, OSi(CH2CH 3) 3), 0.81 (m, 6H, OSi(CH 2CH 3) 3), 0.64 (m, 6H, OSi(CH 2CH 3) 3). 167.4, 159.3, 153.4, 152.0, 136.6, 133.7, 124.1, 119.7, 118.2, 117.3, 101.3, 93.9, 89.3, 85.9, 84.2, 80.7, 74.0, 73.6, 72.7, 72.6, 65.3, 65.2, 61.7, 61.6, 60.2, 57.5, 57.4, 55.1, 54.9, 54.8, 52.7, 44.2, 19.3, 7.6, 5.9, 5.2, 1.4. 405 FI1R (thin fihn), cm- 1: 3463 (m, OH), 2956 (s), 2877 (m), 2214 (w, C=C), 1821 (s, carbonate C=O), 1728 (m, ester C=O), 1620 (m), 1151 (m), 1465 (m), 1410 (m), 1264 (s), 1205 (s), 1150 (s), 1082 (s), 859 (m)_ HRMS (FAB): Calc'd for C 40H51 O11 Si 2 [MHt: 763-2970 Found: 763.2968 TLC (50% EtOAc in Hexanes), Rf. 174: 0.32 (fluoresces under UV, anisaldehyde) 175: 0.64 (fluoresces under UV, anisaldehyde) 406 0 o=< 0"' 11 11 11 11 Martin Sulfurane, CH 2Cl 2, 23 °C 79% Olefin 176 A solution of bis-TES ether 175 (17.6 mg, 0.0231 mmol, 1 equiv) in dichloromethane (1.2 mL) was added via cannula to Martin sulfurane dehydrating agent (78 mg, 0.12 mmol, 5 equiv). The resultant pale yellow solution was stirred at 23 'C for 1.5 h, during which time the solution darkened to light brown. The volatiles were removed in vacuo and the residue was purified by flash column chromatography (dichloromethane) to provide olefin 176 (13.6 mg, 79%) as a pale yellow oil that darkened upon standing. 407 7.60 (d, lH, J = 9.16 Hz, C4" H), 7.21 (s, lH, C8 "H), 6.99 (s, lH, C6" H), 6.89 (d, lH, J = 9.16 Hz, C3" H), 6.23 (t, lH, J = 2.20 Hz, C12 H), 6.01 (d, lH, J = 1.80 Hz, C11 H), 5.07 (s, lH, CS H), 4.18 (d, lH, J = 2.20 Hz, ClO H), 3.52 (s, 3H, C7" OCH 3), 3.46 (m, 2H, C13, C14 H), 3.25 (m, lH, C14 H), 2.77 (s, lH, C5 H), 2.30 (s, 3H, C5'' CH 3), 1.03 (m, 18 H, 2 x OSi(CH 2CH 3) 3), 0.80 (m, 6H, OSi(CH 2CH3 ) 3), 0.68 (m, 6H, OSi(CH 2CH3 ) 3). 167.4, 159.4, 152.1, 139.7, 139.6, 136.7, 133.8, 131.1, 124.1, 119.4, 118.3, 117.2, 101.2, 97.9, 89.9, 87.6, 86.6, 77.2, 74.9, 74.8, 73.1, 65.5, 65.4, 60.5, 60.3, 58.4, 58.3, 54.8, 54.7, 52.3, 52.2, 30.2, 19.3, 6.9, 5.7, 5.4, 1.4. FTIR (thin fihn), cm·1: 2922 (s), 1822 (s, carbonate C=O), 1735 (m, ester C=O), 1620 (m), 1511 (m), 1464 (m), 1264 (s), 1150 (s), 1079 (s), 1037 (m), 863 (m). 408 HRMS(FAB): Calc'd for C 40H49 O 10 Si 2 [MHt: 745.2864 Found: 745.2869 175: 0.49 (fluoresces under UV, anisaldehyde) 176.: 0.61 (fluoresces under UV, anisaldehyde) 409 11 11 11 11 Epoxy alcohol 1 2 Q Triethylamine trihydrofluoride (0.015 mL, 15 mg, 0.091 mmol, 5 equiv) was added via syringe to a solution of olefin 176 (13.6 mg, 0.0183 mmol, 1 equiv) in THF (0.91 mL) at 0 0 C. The resultant yellow solution was stirred at 0 °C for 1 h, and then diluted with ethyl acetate (10 mL). The reaction mixture was washed with water (3 5-mL portions) and saturated aqueous sodium chloride (5 mL), dried over sodium sulfate and concentrated. Purification of the residue by flash column chromatography (2% methanol in dichloromethane) provided epoxy alcohol 120 (13.5 mg, quantitative) as a pale yellow film. 410 12.57 (s, lH, C2" OH), 7.98 (s, lH, C8" H), 7.70 (d, lH, J = 9.16 Hz, C4" H), 7.15 (d, lH, J = 9.52 Hz, C3" H), 6.98 (s, lH, C6" H), 5.69 (t, lH, J = 2.56 Hz, C12 H), 5.47 (d, lH, J = 2.56 Hz, Cl 1 H), 4.40 (d, lH, J = 10.28 Hz, C8 H), 3.64 (d, lH, J = 2.56 Hz, ClO H), 3.53 (dd, lH, J = 8.80, 5.48 Hz, C13 H), 3.50 (s, 3H, CT' OCH 3), 3.34 (dd, lH, J = 8.04, 5.48 Hz, C14 H), 3.23 (t, lH, J = 8.40 Hz, C14 H), 2.77 (s, lH, C5 H), 2.24 (s, 3H, C5" CH 3), 1.84 (d, lH, J = 10.28 Hz, OH). 171.8, 164.3, 160.5, 155.0, 140.1, 138.4, 134.9, 134.0, 131.7, 123.9, 117.7, 116.4, 105.7, 104.4, 99.1, 90.2, 86.9, 86.2, 77.6, 75.9, 75.3, 67.1, 61.8, 61.2, 57.6, 57.2, 53.5, 19.9. 3684 (m, OH), 3070 (m), 3036 (m), 2957 (m), 1823 (s, C=O), 1732 (w), 1649 (w), 1611 (m), 1478 (s), 1199 (m), 1035 (m). 411 HRMS (FAB): Calc'd for C28H21 O10 [MHr: 517.1135 Found: 517.1137 412 Enantioselective Synthesis of Neocarzinostatin Chromophore Aglycone Volume II Thesis by Marlys Hammond In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy California Institute of Technology Pasadena, California 1997 (Submitted October 23, 1996) 413 Table of Contents Volume II Table of Contents (Yolume ID .............................................................. .413 List of Schemes, Fi~ures, and Tables ..................................................... .414 Chapter 5, Thiol Addition Chemist[y and DNA Cleavage Behavior of Neocarzinostatin Chromophore Aglycone........................................ .415 Thiol Addition Chemistry .......................................................... .416 DNA Cleavage by Neocarzinostatin Chromophore Aglycone ................. .421 Experimental Section............................. .................................... 429 References and Notes ......................................................................... 434 Appendix. Catalo~ of Spectra ............................................................... 451 414 List of Schemes, Figures, and Tables Scheme £age Scheme XXV ......................................................................... 417 fue Fi1:ures Figure 4........................................................................ .. ...... 422 Figure 5................................................................................424 Figure 6................................................................................426 Tuhk £age Table 3. Comparison of 1H NMR Data for Thiol Adducts 4, 179, and 180 . ..................................................................... 420 415 Chapter 5 Thiol Addition Chemistry and DNA Cleavage Behavior of Neocarzinostatin Chromophore Aglycone 416 Thiol Addition Chemistry With the development of a concise route to enantiomerically pure 6, the course of these studies shifted next to the investigation of the thiol addition chemistry of 6. As with the epoxy bicyclononadienediyne 5 13 and the chromophore 19c (Ch. 1), initial thiol addition experiments were conducted with a large excess of methyl thioglycolate (0.3 M) and 1,4cyclohexadiene (0.6 M) in a mixture of THF and acetic acid (9: 1) at 23 °C. It was soon noted that the aglycone 6 was not stable in the 9: 1 TIIF/acetic acid solvent mixture, as extensive decomposition of the substrate was noted prior to the addition of methyl thioglycolate (TLC analysis). The nature of this decomposition was not determined and no characterizable products were isolated from the reaction mixtures under these conditions; however, it was apparent that acetic acid, known to assist in the stabilization of the parent chromophore 1, was in fact hastening the decomposition of the aglycone 6. Consequently, further thiol addition studies with 6 were conducted with the omission of acetic acid from the reaction medium. In addition to changing the reaction solvent, further investigations were carried out in the presence of the radical inhibitor BHMS,74 added to solutions of 6 immediately subsequent to chromatographic purification. The inhibitor was found to prolong the lifetime of 6 in solution and during the repeated concentration-dilution processes necessary for the transfer of 6 from the flash column chromatographic eluant solution to the thiol addition reaction conditions. Addition of a deoxygenated solution of methyl thioglycolate (final concentration 0.5 M) to a deoxygenated solution of 6 and 1,4-cyclohexadiene (final concentration 1.0 M) in THF at 23 °C was followed by incubation at 23 °C for 3 hours. Removal of the volatiles in vacuo and 1H NMR analysis of the crude reaction mixture showed no evidence for the formation of the expected cycloaromatized thiol adduct 179 (Scheme XXV). In fact, the only identifiable signals in the spectrum were those corresponding to unreacted aglycone 6. Repetition of the reaction in the presence of 417 Scheme XXV ,-:s 0 HCO~SH 0 }-o a HC 3 ~ o, .... '-'- ~ ~~ ::::-... HO ~J Q OCH3 6 A ! 179 B 418 triethylamine (0.5 M, equimolar with MTG) followed by removal of volatiles after 55 minutes and 1 H NMR analysis of the crude reaction mixture this time provided spectroscopic evidence for the fonnation of the adduct 179. Purification of the reaction mixture by flash column chromatography proved to be difficult and appeared to be complicated by the instability of the adduct 179, which may be prone to air oxidation. A superior purification was achieved using reverse-phase HPLC (40% 10 mM aqueous ammonium acetate (pH 5.5)/60% acetonitrile), keeping the crude reaction mixture and column eluant under an argon atmosphere. 113 In this manner, the thiol adduct 179 was obtained in ~0% purity (1H NMR analysis). The 1H NMR data for the adduct 179 showed a remarkable homology with that of the methyl thioglycolate adducts 4 (Ch. 1) and 180 (from neocarzinostatin chromophore (1) and the model epoxydienediyne 5, respectively) (Table 3). The trans relative stereochemistry between the C-12 thioether and C-11 naphthoate ester groups of the adduct 179 was assigned based on the 1H- 1H coupling constant between these two centers, and was in full accord with the stereochemistry observed in the adduct 4. Electrospray mass spectral analysis of the cycloaromatized product 179 provided peaks corresponding to adducts of 179 with both sodium and potassium. 108 MTG, E'3N, 0 THF,0 ➔ 23°C 38% TBSO 5 180 The yield for the fonnation of thiol adduct 179 was detennined to be 13% by reverse-phase HPLC using 2,5-dimethoxybenzyl alcohol as an internal standard. Interestingly, when two parallel thiol addition reactions were conducted, one in the 419 presence of triethylamine and one in the absence of triethylamine, both showed complete conversion to the thiol adduct 179 within 35 minutes by rp-HPLC analysis. However, after incubation of both reactions at 23 'C for 1 hour, removal of volatiles, and repeat rpHPLC analysis, the reaction conducted in the presence of triethylamine showed complete conversion to the thiol adduct 179, while the reaction conducted in the absence of triethylamine showed no indication of formation of adduct 179, and in fact 58% of the starting aglycone 6 remained (vide infra). The formation of the indacene 179 is believed to occur via the pathway 6 ➔ A ➔ B ➔ 179 (Scheme XXV), in a manner analogous to that proposed for the formation of adduct 4 from the chromophore 1 (Ch. 1, Scheme I). 8 In addition, the thiol addition chemistry of 6 is fully consistent with the earlier findings regarding the thiol addition characteristics displayed by the model epoxydienediyne 5 .13 Both 5 and 6 failed to add MTG in the absence of an added external base. In fact, the epoxy cyclononadiyne 5 failed to add MTG up to a temperature of 60 'C (1H NMR analysis), a temperature at which significant decomposition of 5 ensued. 13 To contrast this behavior, the chromophore 1 undergoes facile thiol addition at - 70 °C in the absence of added base. sb In the presence of added triethylamine (equimolar to MTG), both 5 and 6 undergo addition of MTG at 23 'C to provide the cycloaromatized indacenes 180 (38%) 13 and 179 (13%), respectively. The initial misleading rp-HPLC analysis of the reaction between MTG and 6 in the absence of triethylamine was presumably the result of the buffer used in the HPLC mobile phase (40% pH 5.5 aqueous ammonium acetate (10 mM)/60% acetonitrile) catalyzing the addition of methyl thioglycolate into 6, as evidenced by the reappearance of the aglycone 6 upon removal of the excess MTG. The above results lend further support to the mechanistic postulate implicating the participation of the aminoglycoside as an internal base in the thiol activation of the chromophore 1. 13 The positioning of the sugar residue in the crystal structure of holoNCS such that the distance between the nitrogen of the aminoglycoside and the C-12 420 Adduct 4 179 180 (Solvent) (CDC13) (CD 3CN) (CDC13) C2 7.71 (s) 7.57 (s) 7.40 (s) C5 6.31 (d, J = 5.81) 6.26 (d, J = 5.84) 6.33 (d, J = 5.86) C6 6.95 (d, J = 5.48 ) 6.92 (d, J = 5.88) 6.70 (d, J = 5.86) C8 7.23 (s) 7.35 (s) 7.12 (s) ClO 5.26 (s) 5.34 (br m) 5.39 (m) C11 5.83 (s) 5.75 (t, J = 3.32) 2.5 (m) C12 4.63 (s) 4.60 (d, J = 3.28) 4.52 (d, J = 6.10) C13 4.86 (dd, J = 8.56, 4.67 (dd, J = 8.44, - 6.16) 5.52) 4.43 (dd, J = 8.90, 4.43 (t, J = 9.16) - 4.16 (dd, J = 8.89, 4.27 (dd, J = 8.76, - 6.16) 5.84) C3" 7.03 (d, J = 9.24) 7.04 (d, J = 9.16) - C4" 8.03 (d, J = 9.23) 8.10 (d, J = 9.53) - CS" 2.57 (s) 2.57 (s) - C6" 6.78 (br s) 6.84 (br s) - CT' 3.76 (s) 3.59 (s) - C8" 7.53 (brs) 7.78 (br s) - SCH 2 3.54 (abq, J = 15.14, 3.54 (abq, J = 15.36, 3.22 (abq, J = 14.90, =46.97) llv = 13.02) 3.48 (s) 3.72 (s) C14 8.55) C14 llv =78.55) CO2CH3 3.32 (s) l:w Table 3. Comparison of 1H NMR Data for Thiol Adducts 4, 179, and 180. 421 carbon of 1 is -5A, or approximately the van der Waals diameter of a sulfur atom, indicating that the sugar residue is suitably disposed for this type of assistance. It should be noted, however, that the C-12 position remains the preferred site of thiol addition even in the absence of the aminoglycoside, as the C-12 thiol adducts 179 and 180 were the major products obtained from the reactions of 5 and 6, respectively, with MTG. DNA Cleavage by Neocarzinostatin Chromophore Aglycone The efficacy of neocarzinostatin chromophore aglycone (6) in the cleavage of single-stranded DNA relative to that of the parent neocarzinostatin chromophore (1) was evaluated in this group by Dr. M. E. Kort. The results are briefly summarized below. 109 The DNA cleavage by 6 and the cofactor methyl thioglycolate (MTG) was evaluated using a 3'- 32P-labeled 193-base pair restriction fragment (Eco RI/Ssp I) from plasmid pBR322, and results are given in Figure 4. The aglycone 6 displayed essentially the same relative cleavage pattern as that of the chromophore 1, but the observed efficiency of 6 relative to 1 was markedly lower. Cleavage reactions conducted with the same concentration of drug showed a much higher level of cleavage for 1 (lane 9 vs. lane 11), while a ten-fold higher concentration of 6 was required to effect the same relative amount of cleavage as 1 (lane 7 vs. lane 11). The DNA cleavage by either 1 or 6 could be effectively suppressed at 2 °C by the addition of 1.8 equivalents of apo-NCS (lanes 8, 10, and 12), providing further evidence for the binding of 6 to apo-NCS. The aglycone 6 was found to cleave DNA with little sequence specificity, in full accord with the behavior of the parent chromophore 1. Inspection of histograms prepared by quantitative phosphorimaging of the gel in Figure 4 reveals considerable similarity in the base specificities of 1 and 6 (Figure 5). Both drugs cleave primarily at T and A residues, and the calculated base specificities for 1 and 6 at 2 °C are T (63 %) >> A (24 %) > C( 11 %) >> 0(2%), and T (65%) >> A (22%) > C (10%) >> G (3%), respectively. 73 422 Figure 4 ,... Q) Q) Q) u u Q) Q) C C :::l :::l 0- 0- Cf) Cf) <( CJ Q) Q) e -C ~ C >< 8 a: 0 ~ .c~ o..~ UN ON ~o .c . Q) c~ § E 2-N .?-o CJ) . <( <( 8E Cf) ~ \0 \0 CJ) s. • ~ E s. () s. ---- + - + - + (apo-NCS) 1 2 3 4 5 6 7 8 9101112 e - -= = •- -- Upper Region (41 bp) - - - --- Terminal Region (46 bp) 423 Figure 4. Thiol-dependent DNA cleavage (2 °C, 30 min) by NCS chromophore (1) and aglycone (6). Storage phosphor autoradiogram of an 8% denaturing polyacrylamide gel. All reaction mixtures contained calf thymus DNA (1 mM bp), 3'-labeled 193 bp restriction fragment (~50 kcpm), and NaCl (20 mM) in tris-HCl (50 mM, pH 7.6) with 5% methanol by volume. Lanes 1 and 2: Maxam-Gilbert sequencing reactions; lanes 3 and 4: 6 (0.2 mM) and 1 (0.02 mM), respectively, no added thiol; lanes 5 and 6: apo-NCS (0.036 mM and 0.36 mM, respectively) and methyl thioglycolate (MTG, 2 mM); lanes 7-12: 1 or 6 (at the indicated concentration) and MTG (2 mM) in the absence (-) or presence (+) of 1. 8 equiv (with respect to drug) of purified apo-NCS. 424 Figure 5 Sspl Eco RI 32 193 bp L ____J r p 7 Aglycone (6) Upper Region ,i)T .!!1 TIT! ,,,,, 'tt • 'tft' tll 5'-AAACAAATAGGGGTTCCGCGCACATTTCCCCGAAAAGTGCC-3' NCS Chromophore (1) Aglycone (6) Terminal Region NCS Chromophore (1) tft 425 Figure 5. Observed patterns of single-stranded DNA cleavage arising from treatment of 1 or 6 with MTG at 2 °C as described for Figure 4; consecutive 41 bp ("upper") and 47 bp ("terminal") regions within the 3'-end-labeled 193-bp restriction fragment. Arrow lengths are proportional to the amount of cleavage of the indicated base. 426 Figure6 50-+-_ _..__ __._ ____.__ ____..__ __.__ _-+- A 1 + MTG, 2 °C 40 ---------~------------•---------------------------___ .... - -------- ---------- ------.-----10 , .. 1 + GSH 2 °C 1•apo-NCS + MTG 1•apo-NCS + GSH ,, , o----~----~--~--~---+o 4 8 12 16 20 24 time/h 30-+---"----'-----'---___..__ __.__ _-+- B 6•apo-NCS + MTG ----· ........ --------,-a.,-.-· --- ---- -.:- --- ---- ---- -- -------- 6 + GSH, 2 °C _o------o---~-~-----.-----.---""T""--+ 0 4 8 12 time/h 16 20 6 + MTG, 2 °C 6•apo-NCS + GSH 24 427 Figure 6. Kinetics of thiol-dependent DNA cleavage at 37 °C by (A) NCS chromophore (1, 0.02 mM) and (B) aglycone (6, 0.2 mM) using methyl thioglycolate (MTG) or glutathione (GSH) in the absence or presence of 1.8 equiv of apo-NCS. Reactions were performed in tris-HCl (50 mM, pH 7.6) containing NaCl (20 mM), calf thymus DNA (1 mM bp), and 3'-labeled 193 bp restriction fragment (~150 kcpm) with 5% methanol by volume: (e ) 1 (0.02 mM), apo-NCS (0.036 mM); (0) 6 (0.2 mM), apo-NCS (0.36 mM); - reactions containing MTG (2 mM); ----- reactions containing GSH (2 mM). Reactions conducted at 2 °C in the absence of apo-NCS are shown for comparison: (~ ) 1 (0.02 mM); (A) 6 (0.2 mM). 428 The kinetics of thiol-dependent DNA damage by 1 and 6 were also investigated. These experiments were conducted using both MTG and glutathione (GSH) cofactors, and in the absence and presence of 1.8 equivalents of apo-NCS. The accumulated data, plotted in Figure 6, indicated that the DNA cleavage by 1 was in all cases faster than that of the corresponding reactions carried out with 6. With GSH, both 1 and 6 show similar or greater cleavage efficiency with apo-NCS than without This is also the case for 6 and MTG, but not for 1 and MTG, where the cleavage efficiency is significantly lower in the presence of apo-NCS than in its absence. This has been attributed to the ability of 1 to undergo a competitive protein-directed thiol addition which reduces the overall efficiency of the DNA cleavage reaction. 114 That the aglycone 6 does not show this reduced efficiency with MTG in the presence of apo-NCS may be interpreted to mean that 6 does not undergo the parallel protein-directed thiol addition reaction. It is proposed that the aminoglycoside of 1 again functions as an internal base, this time catalyzing the protein-directed thiol addition reaction. The findings from these studies suggest that the aminoglycoside of 1 both accelerates the rate and improves the efficiency of DNA cleavage versus the aglycone 6, but does not appear to be a major determinant of the base specificity of DNA cleavage by 1. These results emphasize the need for further investigations into the role of the carbohydrate residue of 1 in damaging DNA, and investigations of the DNA-cleaving activity of analogs of 1 bearing modified carbohydrate residues (i.e., non-aminoglydosides) should provide additional insight. The availability of the aglycone 6 in enantiomerically pure form should provide the necessary entry into the preparation of such analogs. 429 Experimental Section General procedures. All reactions were performed in flame-dried round bottom or modified Schlenk (Kjeldahl shape) flasks. The flasks were fitted with rubber septa and contained a positive pressure of argon unless otherwise stated. Stainless steel syringes or cannula were used to transfer air- and moisture-sensitive materials. Concentration in vacuo was accomplished by rotary evaporation at water aspirator pressure (approximately 25 torr). Analytical thin-layer chromatography was performed using glass plates pre-coated with 0.25 mm 230-400 mesh silica gel impregnated with fluorescent indicator (254 nm). Thin-layer chromatography plates were visualized by exposure to ultraviolet light (noted as 'UV') and by exposure to an acidic solution of p-anisaldehyde (noted as 'anisaldehyde') followed by heating on a hot plate. Materials. exceptions. Commercial reagents were used as received, with the following Tetrahydrofuran (THF) was distilled from sodium benzophenone ketyl. Acetonitrile, toluene, and triethylamine were distilled from calcium hydride at 760 torr. Methyl thioglycolate was distilled at 760 torr. 1,4-cyclohexadiene was filtered through a plug of basic alumina immediately prior to use. Instrumentation. Infrared (IR) spectra were obtained using a Perkin-Elmer 1600 Ff-IR spectrophotometer referenced to a polystyrene standard. Data are presented as follows: frequency of absorption (cm- 1) intensity of absorption (v = very, s = strong, m = 430 medium, w = weak) and assignment where appropriate. Proton nuclear magnetic resonance (1H NMR) spectra were recorded on a JEOL GX-400 (400 MHz) NMR spectrometer; chemical shifts for protons are reported in parts per million downfield from tetramethylsilane and are referenced to residual protium in the NMR solvent (CD2HCN: o 1.93). Data are represented as follows: chemical shift, multiplicity (br =broad, s =singlet, d = doublet, t = triplet, q = quartet, m = multiplet, abq = ab quartet), integration, coupling constant in Hertz (Hz), and assignment HPLC was conducted on a Beckman System Gold HPLC equipped with a Beckman ODS C18 reverse-phase column (10 mm x 25 cm) and a Beckman 168 Programmable Photodiode Detector set a 280 nm. Mass spectra were obtained at Beckman Research Institute of the City of Hope, Duarte, California on a Finnigan LCQ ion trap mass spectrometer equipped with a Finnigan-MAT electrospray ion source modified for microspray as previously described. 108 431 6 MTG Et3N, 0 ,23°C 3% 179 Thiol adduct t 7 9 2,5-Dimethoxybenzyl alcohol (ca. 0.6 mg) was added as an internal standard to a deoxygenated solution of the aglycone 6 in methanol (0.5 mL of a solution ~2 mg/mL) containing BHMS (ca. 0.05 mg), and the ratio of aglycone/internal standard was determined by rp-HPLC analysis (ODS C18 column, 10 mm x 25 cm, isocratic solvent system of 40% 10 mM ammonium acetate (pH 5.5)/60% acetonitrile, flow rate of 2.0 mUmin, monitoring at 240 nm; retention times: 6, 25.0 min; 179 , 14.1 min; 2,5dimethoxybenzyl alcohol, 7.3 min). The solution was concentrated to a volume of ca. 0.1 mL, the concentrate was diluted with toluene (0.5 mL), and the resulting solution was 432 concentrated to a volume of ca. 0.1 mL. This procedure was repeated twice. Tetrahydrofuran (0.2 mL) and 1,4-cyclohexadiene (24 mg, 0.028 mL, 0.30 mmol, final concentration 1.0 M) were added to the concentrate, and the solution was deoxygenated. A deoxygenated solution of methyl thioglycolate (16 mg, 0.013 mL, 0.15 mmol, final concentration 0.5 M), and triethylamine (15 mg, 0.021 mL, 0.15 mmol, final concentration 0.5 M) in tetrahydrofuran (0.1 mL) was added and, after 55 minutes, the volatiles were removed in vacuo. The residue was dissolved in toluene and the resulting solution was concentrated to ca. 0.1 mL. This procedure was repeated twice. The residue was then taken up in acetonitrile (0.3 mL), and the yield of 179 was determined by rp-HPLC analysis (as above, 13%). This procedure was repeated on two-fold larger scale and the product was isolated by rp-HPLC (as above) to afford the adduct 179 as a pale yellow oil (ca. 0.2 mg). 433 8.10 (d, 1 H, J = 9.53 Hz, C4" H), 7.78 (br s, 1 H, CS" H), 7 .57 (s, 1 H, C2 H), 7 .35 (s, 1 H, CS H), 7.04 (d, 1 H, J = 9.16 Hz, C3" H), 6.92 (d, 1 H, J = 5.88 Hz, C6 H), 6.84 (br s, 1 H, C6" H), 6.26 (d, 1 H, J = 5.84 Hz, CS H), 5.75 (t, 1 H, J = 3.32 Hz, Cll H), 5.34 (br m, 1 H, ClO H), 4.67 (dd, 1 H, J = 8.44, 5.52 Hz, Cl3 H), 4.60 (d, 1 H, J = 3.28 Hz, C12 H), 4.43 (t, 1 H, J = 9.16 Hz, Cl4 H), 4.27 (dd, lH, J = 8.76, 5.84 Hz, Cl4 H), 3.59 (s, 3 H, CT' OCH 3), 3.54 (abq, 2 H, J = 15.36 Hz, D.v = 46.97 Hz, SCH 2), 3.48 (s, 3 H, CO2CH 3), 2.57 (s, 3 H, CS" CH 3). 3628 (s, OH), 3542 (s, OH), 2932 (m), 1732 (m, C=O), 1631 (m, C=O), 1278 (m), 1204 (m), 1009 (w). MS (electrospray): 631 [M+Na] +, 647 [M+K] + 179: 0.42 (fluoresces under UV, anisaldehyde) 434 References and Notes 435 1. Isolation of neocarzinostatin: (a) Shoji, J. J. Antibiot. 1961, 14, 27. (b) Ishida, N.; Miyazaki, K.; Kumagai, K.; Rikimaru, M. J. Antibiot. 1965, 18, 68. Characterization of neocarzinostatin chromophore: (c) Napier, M. A.; Holmquist, B.; Strydom, D. J.; Goldberg, I. H. Biochem. Biophys. Res. Commun. 1979, 89, 635. (d) Koide, Y.; Ishii, F.; Hasuda, K.; Koyama, Y.; Edo, K.; Katamine, S.; Kitame, F.; Ishida, N. J. Antibiot. 1980, 33, 342. 2. For reviews of the chemistry and biology of the enediynes and other radical abstracting antibiotics, see: (a) Nicolaou, K.C.; Dai, W.-M. Angew. Chem., Int. Ed. Engl. 1991, 30, 1387. (b) Murphy, J. A.; Griffiths, J. Nat. Prod. Rep. 1993, 551. 3. For chromophore structure, see: (a) Edo, K.; Mizugaki, M.; Koide, Y.; Seto, H.; Furihata, K.; Otake, N.; Ishida, N. Tetrahedron Lett. 1985, 26, 331. For carbohydrate stereochemistry, see: (b) Edo, K.; Akiyama, Y.; Saito, K.; Mizugaki, M.; Koide, Y.; Ishida, N. J. Antibiot. 1986, 39, 1615. For chromophore stereochemistry, see: (c) Myers, A. G.; Proteau, P. J.; Handel, T. M. J. Am. Chem. Soc. 1988, J JO, 7212. 4. (a) Sim, S.-K.; Lown, J. W. Biochem. Biophys. Res. Commun. 1978, 81, 99. (b) Burger, R. M.; Peisach, J.; Horwitz, S. B. J. Biol. Chem. 1978, 253, 4830. (c) Kappen, L. S.; Goldberg, I. H. Nucleic Acids Res. 1978, 5, 2959. 5. Kappen, L. S.; Napier, M. A.; Goldberg, I. H. Proc. Nat. Acad. Sci., USA 1980, 77, 1970. 6. Kim, K.-H.; Kwon, B.-M.; Myers, A. G.; Rees, D. C. Science 1993, 262, 1042. 436 7. (a) Hatayama, T.; Goldberg, I. H.; Takeshita, M.; Grollman, A. P. Proc. Nat. Acad. Sci., USA 1978, 75, 3603. (b) Takeshita, M.; Kappen, L. S.; Grollman, A. P.; Eisenberg, M.; Goldberg, I. H. Biochemistry 1981, 20, 7599. (c) Lee, S. H.; Goldberg, I. H. Biochemistry 1989, 28, 1019. 8. (a) Myers, A.G. Tetrahedron Lett. 1987, 28, 4493. (b) Myers, A. G.; Proteau, P. J. J. Am. Chem. Soc. 1989, 111, 1146. 9. (a) Chin, D.-H.; Zheng, C.-h.; Costello, C. E.; Goldberg, I. H. Biochemistry 1988, 27, 8106. (b) Chin, D.-H, Goldberg, I. H. J. Am. Chem. Soc. 1993, 115, 9341. (c) Myers, A.G.; Cohen, S. B.; Kwon, B.-M. J. Am. Chem. Soc. 1994, 116, 1670. 10. Povirk, L. F.; Dattagupta, N.; Warf, B. C.; Goldberg, I. H. Biochemistry 1981, 20, 4007. 11. (a) Galat, A.; Goldberg, I. H. Nucleic Acids Res. 1990, 18, 2093. For other models of neocarzinostatin chromophore binding to DNA, see: (b) Suguiyama, H.; Fujiwara, T.; Kawabata, H.; Yoda, N.; Hirayama, N.; Saito, I. J. Am. Chem. Soc. 1992, 114, 5573. (c) Elbaum, D.; Schreiber, S. L. Bioorg. Med. Chem. 1994, 4, 309. 12. Napier, M. A.; Goldberg, I. H. Mol. Phramacol. 1983, 23, 500. 13. Myers, A.G.; Harrington, P. M.; Kwon, B.-M, J. Am. Chem. Soc. 1992, 114, 1086. 437 14. Myers, A.G.; Hammond, M.; Wu, Y.; Xiang, J.-N.; Harrington, P. M.; Kuo, E. Y. J. Am. Chem. Soc. 1996, 118, 10006. 15. For a review of synthetic studies of the enediyne antibiotics, see: Grissom, J. W.; Gunawardena, G. U.; Klingberg, D.; Huang, D. Tetrahedron 1996, 52, 6453. 16. For representative acyclic model systems, see: (a) Saito, I.; Yamaguchi, K.; Nagata, R.; Murahashi, E. Tetrahedron Lett. 1990, 31, 7469. (b) Wender, P. A.; Tebbe, M. J. Tetrahedron 1994, 50, 1419. For representative ten-membered ringcontaining model systems, see: (c) Nakatani, K.; Arai, K.; Terashima, S. Tetrahedron 1993, 49, 1901. (d) Kawata, S.; Oishi, T.; Hirama, M. Tetrahedron Lett. 1994, 35, 4595. (e) Matsumoto, Y.; Kuwatani, Y.; Ueda, I. Tetrahedron Lett. 1995, 36, 3197. (f) Eckhardt, M.; Bruckner, R.; Suffert, J. Tetrahedron Lett. 1995, 36, 5167. (g) Toshima, K.; Ohta, K.; Yanagawa, K.; Kano, T.; Nakata, M.; Kinoshita, M.; Matsumura, S. J. Am. Chem. Soc. 1995, 117, 10825. (h) Eckhardt, M.; Bruckner, R. Angew. Chem., Int. Ed. Engl. 1996, 35, 1093. 17. For the synthesis of the parent carbocyclic core of 1 (7), see: Wender, P.A.; Harmata, M.; Jeffrey, D.; Mukai, C.; Suffert, J. Tetrahedron Lett. 1988, 29, 909. 18. For the synthesis of model system 8, see: (a) Wender, P. A.; McKinney, J. A.; Mukai, C. J. Am. Chem. Soc. 1990, 112, 5369. For the synthesis of model system 9, see: (b) Takahashi, T.; Tanaka, H.; Hirai, Y.; Doi, T.; Yamada, H.; Shiraki, T.; Sugiura, Y. Angew. Chem., Int. Ed. Engl. 1993, 32, 1657. For the 438 synthesis of model system 10, see: (c) Magnus, P.; Carter, R.; Davies, M.; Elloitt, J.; Pitterna, J. Tetrahedron 1996, 52, 6283. 19. Myers, A. G.; Harrington, P. M.; Kuo, E. Y. J. Am. Chem. Soc. 1991, 113, 694. 20. Kuo, E. Y., Ph.D. Thesis, California Institute of Technology, 1993. 21. (a) Schmid, C.R.; Bryant, J. D.; Dowlatzedah, M.; Phillips, J. L.; Prather, D. E.; Schantz, R. D.; Sear, N. L.; Vianco, C. S. J. Org. Chem. 1991, 56, 4056. (b) Schmid, C.R.; Bryant, J. D. Org. Synth. 1993, 72, 6. 22. Brandsma, L. Preparative Acetylenic Chemistry; Elsevier: Amsterdam, 1988; p 24. 23. Czemecki, S.; Georgoulis, C.; Stevens, C. L.; Vijayakumarin, K. Tetrahedron Lett. 1985, 26, 1699. 24. Danheiser, R. L.; Stoner, E. J.; Koyama, H.; Yamashita, D. S.; Clade, C. A. J. Am. Chem. Soc. 1989, 111, 4407. 25. Garegg, P. J.; Samuelsson, B. J. J. Chem. Soc., Chem. Commun. 1979, 978. 26. (a) Corey, E. J.; Ruden, R. A. Tetrahedron Lett. 1973, 1495. (b) Ahmed, M.; Barley, G. C.; Heam, M. T. W.; Jones, E. R. H.; Thaller, V.; Yates, J. A. J. Chem. Soc., Perkin Trans. 1 1974, 1981. 27. Kiessling, L. L., Ph.D. Thesis, Yale University, 1989. 439 28. Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis; John Wiley & Sons: New York, 1991; p 125. 29. Sill, W. C.; Kahn, M.; Mitra, A. J. Org. Chem. 1978, 43, 2923. 30. Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis; John Wiley & Sons: -New York, 1991; p 83. 31. Gao, Y.; Hanson, R. M.; Klunder, J. M.; Ko, S. Y.; Masamune, H.; Sharpless, K. B. J. Am. Chem. Soc. 1987, 109, 5765. 32. Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis; John Wiley & Sons: New York, 1991; p 81. 33. Dale, J. A.; Dull, D. L.; Mosher, H. S. J. Org. Chem. 1969, 34, 2543. 34. Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis; John Wiley & Sons: New York, 1991; p 123. 35. Myers, A.G.; Hammond, M.; Wu, Y. Tetrahedron Lett. 1996, 37, 3083. 36. Suzuki, M.; Kawagishi, T.; Noyori, R. Tetrahedron Lett. 1981, 22, 1809. 37. Paquette, L.A.; Earle, M. J.; Smith, G. F. Org. Synth. 1995, 73, 36. 440 38. All capillary gas chromatographic analyses were canied out on a Chirasil-val chiral column (25 m x 0.25 mm ID, Alltech Associates, Inc.). In the ee determinations of (+)-30, 32a, and 34, an authentic sample of racemate was transformed and analyz.ed along with optically active material. In no case was the kinetic enrichment of the Mosher esters from a racemic mixture of alcohols >5%. In the ee determination of 32b, an authentic sample of the antipode was prepared by DIBAL reduction of (- )-30 39 for comparison purposes. 39. Danishefsky, S. J.; Cabal, M. P.; Chow, K. J. Am. Chem. Soc. 1989, 111, 3456. 40. (a) Deardorff, D. R.; Matthews, A. J.; McMeekin, D. S.; Craney, C. L.; Tetrahedron Lett. 1986, 27, 1255. (b) Deardorff, D. R.; Windham, C. Q.; Craney, C. L. Org. Synth. 1995, 73, 25. 41. Corey, E. J.; Venkateswarlu, A. J. Am. Chem. Soc. 1972, 94, 6190. 42. Corey, E. J.; Suggs, J. W. Tetrahedron Lett. 1975, 2647. 43. The following values for the optical rotation of (+)-30 have been reported:[a]~ [a]~= +67.0 ° (c 0.12, CH3OH); 43a [a]~= +66.6 ° (c 1.00, CH 3 OH); 43b [a]~= +67 .3 ° (c 0.82, CH 3OH); 43c [a]~ = +65.3 (c 0.40, CH 3OH) 37 (a) Gill, M.; Rickards, R. W. Tetrahedron Lett. 1979, 17, 1539. (b) Kitamura, M.; Kasahara, I.; Manabe, K.; Noyori, R.; Takaya, H. J. Org. Chem. 1988, 53, 710. (c) Kitano, Y.; Okamoto, S.; Sato, F. Tetrahedron: Asymmetry 1993, 4, 2277. 44. Myers, A.G.; Subramanian, V.; Hammond, M. Tetrahedron Lett. 1996, 37, 587. 441 45. Quinkert, G.; Weber, W.-D.; Schwartz, U.; Stark, H.; Baier, H.; Dlirner, G. Leibigs Ann. Chem. 1981, 2335. 46. Ziegler, C. B.; Heck, R. F.; J. Org. Chem. 1978, 43, 2941. 47. Bram, G.; Vilkas, M. Bull. Soc. Chim. Fr. 1964, 945. 48. Wyman, D. P.; Kaufman, P. R.; Freeman, W. R. J. Org. Chem. 1964, 29, 2706. 49. Takahashi, K.; Suzuki, T.; Hirama, M. Tetrahedron Lett. 1992, 33, 4603. 50. Myers, A. G.; Xiang, J.-N., California Institute of Technology, unpublished results. 51. Corey, E. J.; Snider, B. B. J. Am. Chem. Soc. 1972, 94, 2549. 52. (a) Neises, B.; Steglich, W. Angew. Chem., Int. Ed. Engl. 1978, 17, 522. (b) Hassner, A.; Alexanian, V. Tetrahedron Lett. 1978, 4475. 53. Kutney, J. P.; Ratcliffe, A. H. Synth. Commun. 1975, 5, 47. 54. Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis; 2nd ed., John Wiley & Sons: New York, 1991; p 68. 55. Corey, E. J.; Gras, J.-L.; Ulrich, P. Tetrahedron Lett. 1976, 809. 442 56. Jackman, L. M.; Sternhell, S. Applications of Nuclear Magnetic Resonance in Organic Chemistry; Pergamon Press: New York, 1969; pp 286-289, and references cited therein. 57. Lowrey, T. H.; Richardson, K. S. Mechanism and Theory in Organic Chemistry; Harper & Row: New York, 1987; p 429. 58. Corey, E. J.; Cho, H.; Rucker, C.; Hua, D. H. Tetrahedron Lett. 1981, 22, 3455. 59. Furst, A.; Koller, F. Helv. Chim. Acta 1947, 30, 1454. 60. (a) Papa, A. J. J. Org. Chem. 1966, 31, 1426. (b) Li, C.; Arasappan, A.; Fuchs, P. L. Tetrahedron Lett. 1993, 34, 3535. 61. (a) Martin, J.C.; Arhart, R. J. J. Am. Chem. Soc. 1971, 93, 4327. (b) Arhart, R. I.; Martin, J. C. J. Am. Chem. Soc. 1972, 94, 4997. 62. (a) Mitsunobu, 0. Synthesis 1981, 1. (b) Hughes, D. L. Org. React. 1992, 42, 335. 63. Sai"ah, M.; Bessodes, M.; Antonakis, K. Tetrahedron Lett. 1992, 33, 4317. 64. (a) Martin, S. F.; Dodge, J. A. Tetrahedron Lett. 1991, 32, 3017. (b) Dodge, J. A.; Trujillo, J. I.; Presnell, M. J. Org. Chem. 1994, 59, 234. (c) Dodge, J. A.; Nissen, J. S.; Presnell, M. Org. Synth. 1996, 73, 110. 443 65. Colvin. E. W.; Raphael. R. A.; Roberts, J. S. J. Chem. Soc., Chem. Commun. 1971, 858. 66. Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis; John Wiley & Sons: New York, 1991; p 85. 67. Myers. A.G.; Harrington, P. M., California Institute of Technology, unpublished results. 68. (a) Jackman, L. M.; Sternhell, S. Applications of Nuclear Magnetic Resonance in Organic Chemistry; Pergamon: New York, 1969; pp 345-348, and references cited therein. (b) Silverstein, R. M.; Bassler, G. C.; Morrill, T. C. Spectrometric Identification of Organic Compounds; John Wiley & Sons: New York, 1991; p 247. 69. Myers, A.G.; Wu, Y., California Institute of Technology, unpublished results. 70. The acid 72 was utilized as a nucleophile in the Mitsunobu reaction in anticipation of the selective cleavage of the nascent ester group in the presence of the naphthoate ester. Model studies with 3~-dihydrocholestanol had shown that Mitsunobu esterification with 72 could be followed by photolytic cleavage of the 2-nitrobenzyl ether71 and treatment of the resultant hydroxy ester with-dilute TFA in THF to afford 3a-dihydrocholestanol. 71. Pillia, V. N. R. Synthesis, 1980, 1. 444 72. HPLC purification of the Mitsunobu product was carried out on a Waters Delta Prep 3000 HPLC equipped with a Waters 994 programmable photodiode array detector set at 240 nm and a Vydac HS C18 reverse-phase column (22 mm x 25 cm). The system utilized an isocratic solvent system comprising 14% 10 mM aqueous ammonium acetate (pH 5.5)/86% acetonitrile at a flow rate of 7 .0 mLJminute. The retention time of the Mitsunobu product was approximately 30 minutes. 73. Tanaka, K.; Yoda, H.; Isobe, Y.; Kaji, A. J. Org. Chem 1986, 51, 1856. 74. Kishi, Y.; Aratani, M.; Tanino, H.; Fukuyama, T.; Goto, T.; Inoue, S.; Sugiura, S.; Kakoi, H.J. Chem. Soc., Chem. Commun. 1972, 64. 75. For the first reported use of ethylaluminum dichloride as a Lewis acid catalyst (For 2+2 cycloadditions), see: Lukas, J. H.; Kouwenhoven, A. P.; Baardman, F. Angew. Chem, Int. Ed. Engl. 1975, 14, 109. 76. For a review of the uses of trimethylsilyl trifluoromethanesulfonate, see: Noyori, R.; Murata, S.; Suzuki, M. Tetrahedron 1981, 37, 3899. 77. Heathcock, C.H.; Young, S. D.; Hagan, J. P.; Pilli, R.; Badertscher, U. J. Org. Chem 1985,50, 2095. 78. (a) Murray, R. W.; Jeyaraman, R. J. Org. Chem 1985, 50, 2847. (b) Adam, W.; Bialis, J.; Hadjiarapoglou, L. Chem. Ber. 1991, 124, 2377. 445 79. Mello, R.; Fiorentino, M.; Sciacovelli, O.; Curci, R. J. Org. Chem. 1988, 53, 3980. 80. (a) Vilkas, M. Bull. Soc. Chim Fr. 1959, 1401. (b) Swem, D. In Organic Peroxides; Swem, D., Ed.; Wiley lnterscience: New York, 1971; Vol. II, p 410. (c) Duke, R. K.; Rickards, R. W. J. Org. Chem 1984, 49, 1898. 81. Gagnieu, C.H.; Grouiller, A. V. J. Chem. Soc., Perkin Trans. 1 1982, 1009. 82. (a) Emmons, W. D.; Pagano, A. S.; Freeman, J. P. J. Am Chem. Soc. 1954, 76, 5199. (b) Quick, J.; Khandewal, Y.; Meltzer, P. C.; Weinberg, J. S. J. Org. Chem. 1983, 48, 5199. (c) McKittrick, B. A.; Ganem, B. Tetrahedron Lett. 1985, 26, 4895. 83. Kitamura, M.; Isobe, M.; Ichikawa, Y.; Goto, T. J. Org. Chem. 1984, 49, 3517. 84. Sharpless, K. B.; Michaelson, R. C. J. Am Chem Soc. 1973, 95, 6136. 85. Solladie, G.; Hutt, J. J. Org. Chem 1987, 52, 3560. 86. Sclessinger, R. H.; Bebemitz, G. R.; Lin, P. J. Am. Chem Soc. 1985, 107, 1778. 87. (a) Yang, N. C.; Finnegan, R. A. J. Am. Chem Soc. 1958, 80, 5848. (b) Grieco, P. A.; Nishizawa, M.; Oguri, T.; Burke, S. D.; Marinovic, N. J. Am. Chem. Soc. 1977, 99, 5773. 446 88. Burke, S. D.; Murtiashaw, C. W.; Saunders, J. O.; Oplinger, J. A.; Dike, M. S. J. Am. Chem. Soc. 1984, 106, 4558. 89. Danishefsky, S.; Zamboni, R.; Kahn, M.; Etheridge, S. J. J. Am. Chem. Soc. 1981, 103, 3460. 90. Mancuso, A. J.; Swem, D. Synthesis 1981, 165. 91. Although it is not clear what the effect of lithium chloride is in the present case, the effect of lithium halides on the diastereoselectivity of an intermolecular acetylide addition to a ketone has been examined, and the results have been attributed to the effects of the additive on the aggregation state of the lithium acetylide. 913 The effect of lithium halides on the structure and reactivity of enolates as related to their aggregation states has also been studied. 91 b (a) Carreira, E. M.; Du Bois, J. J. Am. Chem. Soc. 1995, 117, 8106, and references cited therein. (b) Seebach, D. Angew. Chem., Int. Ed. Engl. 1988, 27, 1624. 92. Barton, D. H. R.; Motherwell, R. S. H.; Motherwell, W. B. J. Chem. Soc., Perkin Trans. 1 1981, 2363. 93. Jackman, L. M.; Stemhell, S. Applications of Nuclear Magnetic Resonance in Organic Chemistry; Pergamon Press: New York, 1969; p 303, and references cited therein. 94. (a) Dess, D. B.; Martin, J.C. J. Am. Chem. Soc. 1991, 113, 7277. (b) Ireland, R. E.; Liu, L. J. Org. Chem. 1993, 58, 2899. 447 95. (a) Saha, A. K.; Schultz, P.; Rapoport, H.J. Am. Chem. Soc. 1989, 111, 4856. (b) Bahktiar, C.; Smith, E. H.J. Chem. Soc., Perkin Trans. 1 1994, 239. 96. (a) RajanBabu, T. V.; Nugent, W. A.; Beattie, M. S. J. Am. Chem. Soc. 1990, 112, 6408. (b) RajanBabu, T. V.; Nugent, W. A. J. Am. Chem. Soc. 1994, 116, 986. 97. For the use of triethylborane as an initiator in tin hydride-mediated radical reactions, see: (a) Miura, K.; Ichinose, Y.; Nozaki, K.; Fugami, K.; Oshima, K.; Utimoto, K. Bull. Chem. Soc. Jpn. 1989, 62, 143. (b) Nozaki, K.; Oshima, K.; Utimoto, K. Tetrahedron 1989, 45, 923. 98. Little to no difference has been observed m reactions utilizing trifluoromethanesulfonic anhydride when the expensive 2,6-di-tert-butylpyridine is replaced with the moderately priced 2-chloropyridine. The 2-chloropyridine also does not react with trifluoromethanesulfonic anhydride, as is observed with pyridine and 2,6-lutidine. 99 Myers, A. G.; Tom, N. J.; Hammond, M., California Institute of Technology, unpublished results. 99. Binkley, R. W.; Ambrose, M. G. J. Org. Chem. 1983, 48, 1776. 100. Bajwa, J. S.; Anderson, R .C. Tetrahedron Lett. 1991, 32, 3021. 101. Bonini, C.; Righi, G.; Sotgui, G. J. Org. Chem. 1991, 56, 6206. 102. For a review of ionic hydrogenations in organic synthesis, see: Kursamov, D. N.; Parnes, Z. N.; Loim, N. M. Synthesis 1974, 634. 448 103. (a) Doyle, M. P.; West. C. T.; Donnelly, S. J.; McOsker, C. C. J. Organomet. Chem. 1976, 117, 129. (b) Fry, J. L.; Orfanopoulos, M.; Adlington, M. G.; Dittmer, Jr., W.R.; Silverman, S. B. J. Org. Chem. 1978, 43, 374. 104. Hutchings, R. O.; Taffer, I. M.; Burgoyne, W. J. Org. Chem. 1981, 46, 5214. 105. Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis; John Wiley & Sons: New York, 1991; p 92. 106. For related transfonnations, see: (a) Mori, K.; Ueda, H. Tetrahedron 1981, 37, 2581. (b) Barluenga, J.; Fernandez-Simon, J. L.; Concell6n, J. M.; Yus, M. J. Chem. Soc., Perkin Trans. 1 1989, 77. (c) Burke, S. D.; Buchanan, J. L.; Rovin, J. D. Tetrahedron Lett. 1991, 32, 3961. 107. Denklau, D.; Kohnlein, W.; Ltiders, G.; Stellmach, J. Z. Naturforsch. 1983, 38c, 939. 108. Mass spectra were obtained on a Finnigan LCQ ion trap mass spectrometer equipped with a Finnigan-MAT electrospray ion source modified for microspray as previously described. Davis, M. T.; Stahl, D. C.; Hesta, S. A.; Lee, T. D. Anal. Chem. 1995, 67, 4549. 109. Myers, A. G.; Kort, M. E.; Hammond, M. Angew. Chem., Int. Ed. Engl. submitted for publication. 449 110. (a) Zhinkin, D. Y.; Mal'nova, G. N.; Gorislavskaya, Zh. V. 7h. Obshch. Khim. 1968, 38, 2800. (b) Masamune, S.; Ellingboe, J. W.; Choy, W. J. Am. Chem. Soc. 1982, 104, 5526. 111. Kimura, J.; Mitsunobu, 0. Bull. Chem. Soc. Jpn. 1978, 51, 1903. 112. The aglycone 6 has been successfully glycosylated with a protected fucosamine derivative to provide the neocarzinostatin chromophore analog 177 . 1128 Additionally, the fucose analog 178 has been prepared. 112b (a) Myers, A. G.; Wu, Y.; Hammond, M., California Institute of Technology, unpublished results. (b) Myers, A. G.; Liang, J.; Hammond, M., California Institute of Technology, unpublished results. 0 O?<:HO ~tf V NH ~CCll OTBS 3AMS,TIOH, PhCH,. -20 •c CH, G OR i w H,CO~OH CH, 177 o-- • o=(~H II 1. TESO CH, 0 NH lESO~CCll If' OTES 3AMS,TIOH, PhCH 3 ,-20·c 2 5% HF, CH,CN,-30"C II n ; WO OOR Hlco ~ ~ OH IO CH, -& 178 450 113. HPLC purification of the adduct 179 was carried out on a Beckman System Gold HPLC equipped with a Beckman 168 diode array detector set at 240 run and a Beckman ODS C18 reverse-phase column (10 mm x 25 cm). The system utilized an isocratic solvent system comprising 40% 10 mM aqueous ammonium acetate (pH 5.5)/60% acetonitrile at a flow rate of 2.0 mUminute. Retention times are as follows: 6, 25 min; 2,5-dimethoxybenzyl alcohol, 7.3 min; 179, 14.1 min. 114. Myers, A.G.; Arvedson, S. P.; Lee, R. W. J. Am. Chem. Soc. 1996, 118, 4725. 451 Appendix Catalog of Spectra 452 -----------==-'\ ·, f·[ ~~)7t" i : I • I ~., i : I~ I• -:c: l -c. ~· ~ : It ,....., i • I : i i I _,_ ' ' ''-., Cl) :E I - ~::r: 0 r• C") N .., 0 t 5. .;-0 (.) ::I:"' ► I :-2 t if I I l'1 6'0 I I 1·0 L'O 9·0 I , ·o I ~-o I £'0 I t ·o I 1·0 o· - . ·- ----- - 45: s R CH3 3 H C" -0- f - ~TMS 0 ¢, OH 23 Iii 2 .. • DJ 210 :Ill) "° 1-, no 1----r--- . - - tee> 1,0 '"° ry--i----r-- - , - ~ ,0 120 110 100 130 ., '10 eo .. ,0 «> ,0 2IJ IO 0 .,o .JD ca--t BOO ~-115 IT 4000 11500 3000 2!500 2000 11500 1000 454 C L.... r'° I I' _I .-... t t - ., 455 TBs--==-- 'er 26 ao moo moo 2l500 2000 456 i - .... I• I """l i 0 ... .., .c CD 0 Cl. Cl. 1fi en ~-o CD r I- f 0 - ·- - - -·- - - - · - - - -· ·- · - ···- - - - - -z 57 0 lil TBS-e:==----..,0 Br PPh3 27 113.19 IT «>00 !eOO 3000 2500 2000 1000 c:11-1 BOO 458 _J - ' -• ---: _.,., .. l _.., ~ -..... - -r- C') cti () + C0 N Cl) ::r: --:; ~ Cl) ::E 1- oxo .., .., (.) (.) ::r: ::r: 06Z cm OL? 09l: ~ O,? O£Z ~ 01? 00? 061 Oil OLI 091 OSI Ott 0£1 OZI 011 0()1 06 08 OL 09 OS Ot 0£ OZ 01 o· - -- --- . ~ - ---- - --- - -- · ·- • . -• - ~ -- -- - - - - - - - ·- 459 II i; H,C,,. 0 II - ::I ~ H~><ox ~ fl ;; TMS ti = TBS + ~ TBS :: ! H3CXO = H3C Ill 0'' :. ::? UJ = = -H TMS 2 • - 28 (ca. 3:1) .., . .. ......... T • - - - - r - - t -. .- -. 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