Biocatalytic Reductions of Baylis-Hillman Adducts

Baylis-Hillman adducts are highly useful synthetic intermediates; to enhance their value further, we sought enantiocomplementary alkene reductases to introduce chirality. Two solutions emerged: (1) a wild-type protein from Pichia stipitis (OYE 2.6), whose performance significantly outstrips that of the standard enzyme (Saccharomyces pastorianus OYE1), and (2) a series of OYE1 mutants at position 116 (Tip in the wild-type enzyme). To understand how mutations could lead to inverted enantioselectivity, we solved the X-ray crystal structure of the Trp116Ile OYE1 variant complexed with a cydopentenone substrate. This revealed key protein ligand interactions that control the orientation of substrate binding above the FMN cofactor.