Synthesis of Chiral Sulfoxides by A Cyclic Oxidation‐Reduction Multi‐Enzymatic Cascade Biocatalysis

Abstract Optically pure sulfoxides are valuable organosulfur compounds extensively employed in medicinal and organic synthesis. In this study, we present a biocatalytic oxidation‐reduction cascade system designed for the preparation of enantiopure sulfoxides. The system involves the cooperation of a low‐enantioselective chimeric oxidase SMO (styrene monooxygenase) with a high‐enantioselective reductase MsrA (methionine sulfoxide reductase A), facilitating “non‐selective oxidation and selective reduction” cycles for prochiral sulfide oxidation. The regeneration of requisite cofactors for MsrA and SMO was achieved via a cascade catalysis process involving three auxiliary enzymes, sustained by cost‐effective D‐glucose. Under the optimal reaction conditions, a series of heteroaryl alkyl, aryl alkyl and dialkyl sulfoxides in R configuration were synthesized through this “one‐pot, one step” cascade reaction. The obtained compounds exhibited high yields of >90 % and demonstrated enantiomeric excess ( ee ) values exceeding 90 %. This study represents an unconventional and efficient biocatalytic way in utilizing the low‐enantioselective oxidase for the synthesis of enantiopure sulfoxides.