Directed Evolution of Nonheme Iron Enzymes for Enantioselective Aminative Difunctionalization of Alkenes.

Abstract

The direct aminative difunctionalization of alkenes offers a powerful strategy for synthesizing valuable amine-containing compounds. However, achieving this transformation enantioselectively remains a significant challenge in both synthetic chemistry and biocatalysis. In this study, we engineered a nonheme iron enzyme, quercetin 2,3-dioxygenase from Bacillus subtilis (BsQueD), to catalyze three distinct alkene aminofunctionalization reactions with high efficiency and enantiocontrol. Through directed evolution, we developed an optimized BsQueD variant capable of producing a wide array of chiral 2-azidoamines, 2-aminothiazolines, and 2-aminooxazolines with up to 72% yield and 99:1 enantiomeric ratio (e.r.). Mechanistic investigations suggest a stepwise radical addition pathway. This work broadens the scope of biocatalytic alkene difunctionalization, providing a sustainable and efficient route for synthesizing diverse chiral primary amines.