Engineering of Methionine Sulfoxide Reductase A with Expanded Substrate Scope for Deracemization of Sulfinyl Esters

Chiral sulfinyl esters are an essential source for preparation of chiral sulfur-containing fine chemicals and pharmaceuticals. However, sustainable and enantioselective syntheses of optically pure sulfinyl esters remain to be explored. Herein, we have developed methionine sulfoxide reductase A (MsrA) variants with expanded substrate scope using in silico docking and semirational mutagenesis techniques, aimed at preparing enantiopure sulfinyl esters. The variant paMsrA-F59A exhibited exceptional activity and enantioselectivity across various sulfinyl esters, yielding the R enantiomers with approximately 50% yield and 99% enantiomeric excess. Furthermore, this variant overcame the significant limitation of wild-type (WT) MsrA, broadening its substrate scope from methyl and ethyl substituents to n-propyl/butyl and ester substituents. Afterward, by employing the paMsrA-F59A in conjunction with the oxidase styrene monooxygenase (SMO), we achieved the cyclic deracemization of racemic sulfinyl esters, obtaining a series of (R)-sulfinyl esters with >90% yield and 99% enantiomeric excess. This study successfully expanded the substrate scope of MsrA, providing an environmentally friendly strategy for efficiently preparing enantiopure sulfinyl esters. Moreover, our study extended the application of MsrA in the sustainable and enantioselective synthesis of chiral sulfinyl compounds with bulkier frameworks, highlighting its potential in green chemistry applications.