Biocatalysis has become a green and popular tool for asymmetric organic synthesis due to the high selectivity, non-toxicity, and mild reaction conditions. Furthermore, many enzymes catalyze reactions in a similar conditions and thus enable performing multiple transformations in a cascade manner in one pot or even one cell. Cascade biocatalysis circumvents the time-consuming, yield-decreasing, waste-producing, and labor-demanding intermediates recovery and purification in traditional multi-step synthesis. Recently, we have developed several new types of cascade biocatalysis for asymmetric oxyfunctionalization of easily available alkenes to produce enantiopure valuable chemicals. We engineered a green, facile, and efficient cascade biocatalysis system for enantioselective trans-dihydroxylation of conjugated aryl alkenes with oxygen and water as reactants. The engineered recombinant Escherichia coli cells coexpressing styrene monooxygenase and epoxide hydrolase are highly active for cascade enantioselective epoxidation and regioselective hydrolysis. Moreover, both enantiomers of various vicinal diols can be achieved in high ee and high yield by using two different epoxide hydrolases with complementary regioselectivity. Two recombinant E. coli strains with complementary selectivity were applied for the transformation of 22 conjugated aryl olefins to produce more than 30 different chiral vicinal diols in high ee and good yield. The biocatalytical trans-dihydroxylation is complementary to the famous Sharpless asymmetric dihydroxylation. Currently, we further extend the cascade reaction to prepare enantiopure a-hydroxy carboxylic acids from terminal alkenes by introduction of oxidase and/or dehydrogenase into the epoxidase and hydrolase system. Our whole-cell based cascade biocatalysis represents a promising method for asymmetric oxyfunctionalization of alkenes, with potential for industrial application.

Cascade biocatalysis for asymmetric oxyfunctionalization of alkenes

247th National Meeting (2014)

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