Abstract:
The advent of well-engineered small-molecule catalysts and enzyme catalysts has revolutionized the field of synthetic science. Using tailored small-molecule catalysts, synthetic chemists have developed a diverse range of chemical reactions not encountered in nature. With these human-invented processes, a variety of simple and easily available building blocks can be converted into value-added products. On the other hand, by harnessing fully genetically encoded enzyme catalysts, synthetic biologists and bioengineers assemble complex molecules with excellent efficiency and selectivity. These enzyme catalysts can be conveniently expressed in bacteria or yeasts using biorenewable feedstocks, and their performance can be easily optimized by directed evolution. In this talk, by further leveraging small-molecule catalysis and enzyme catalysis, I will describe two strategies to address challenging problems in asymmetric synthesis. In the first part of this talk, I will discuss the use of copper(I) hydride (CuH) catalysts for the asymmetric hydrofunctionalization of simple olefins. Specifically, we have developed a CuH-catalyzed method for the enantioselective hydroamination of unactivated olefins and a set of methods for the enantioselective addition of olefin-derived nucleophiles to carbonyls and imines. These processes provided a powerful means to prepare highly enantioenriched amines and alcohols, many of which are challenging to access by other catalytic methods. In the second half of this talk, I will introduce an enzymatic platform for the asymmetric amination of sp3 hybridized C-H bonds. Through directed evolution of cytochrome P450 enzymes, we have engineered biocatalysts for the enantioselective amination of three types of C(sp3)-H bonds, including primary, secondary, and tertiary ones. Together, these evolved enzymes provided a new solution to tackle challenges in enantioselective catalysis.