Biocatalytic Lactone Carbene C–H, B–H, and N–H Insertion Reactions Enabled by Directed Evolution

Author: Zhou, Andrew Z.

Year: 2021

Degree: Senior thesis (Major)

Advisor: Arnold, Frances Hamilton

Committee Member: None, None

Option: Chemistry; Biology

DOI: 10.7907/zqcp-jt95

Abstract

Enzymes are biological catalysts, and they accelerate reactions by lowering the activation barrier. In nature, enzymes have been optimized by natural selection and possess precise three-dimensional active sites. With these active sites, they can typically catalyze reactions with high efficiency and specificity. Compared to traditional catalysts, enzymes are generally more environmentally friendly, and they can catalyze reactions in water and at ambient temperature and pressure. However, native enzymes are usually only well suited for a restricted range of substrates and are limited in the types of reactions they perform. The Arnold lab has recently focused on endowing enzymes with the ability to catalyze new-to-nature reactions through directed evolution. Here, we present a set of enzymes engineered for the ability to insert a lactone carbene into B–H, C–H, and N–H bonds with high yield and enantioselectivity. B–H insertion is achieved by engineered cytochrome c enzymes, while N–H and C–H insertions are achieved by engineered cytochrome P450 enzymes. With this work, we expand nature’s toolbox for lactone insertion chemistry. Since lactones are highly bioactive, these engineered enzymes could be powerful tools in the synthesis of a range of pharmaceuticals and natural product targets.

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