Stereo-Divergent Enzyme Cascades to Convert Racemic 4-Phenyl-2-Butanol into either (S)- or (R)-Corresponding Chiral Amine.

Abstract

The synthesis of enantiopure chiral amines from racemic alcohols is a key transformation in the chemical industry, e. g., in the production of active pharmaceutical ingredients (APIs). However, this reaction remains challenging. In this work, we propose a one‐pot enzymatic cascade for the direct conversion of a racemic alcohol into either (S)‐ or (R)‐enantiomers of the corresponding amine, with in‐situ cofactor recycling. This enzymatic cascade consists of two enantio‐complementary alcohol dehydrogenases, both NADH and NADPH oxidase for in‐situ recycling of NAD(P)+ cofactors, and either (S)‐ or (R)‐enantioselective transaminase. This cell‐free biocatalytic system has been successfully applied to the conversion of racemic 4‐phenyl‐2‐butanol into the high value (S)‐ or (R)‐enantiomers of the amine reaching good (73 % (S)) and excellent (>99 % (R)) enantioselectivities.