Asymmetric synthesis of stereogenic-at-sulfur compounds via biocatalytic oxidation with Unspecific Peroxygenases

Stereogenic-at-sulfur compounds are vitally important biologically active small molecules, with many drugs featuring chiral sulfur atoms. Methods for the asymmetric synthesis of sulfoxide centres are well established, but methods that produce enantiomerically enriched sulfoximines and sulfinimines are far less well developed, with no known biocatalytic methods based on oxygenation. In this study, we demonstrate that Unspecific Peroxygenases (UPOs) catalyse the biocatalytic oxygenation of sulfilimines and sulfenimines to form enantiomerically enriched sulfoximines and sulfinimines respectively, on preparative scale. In the sulfilimine series, sulfoximines are generated in up to 98% ee via a kinetic resolution approach. In the sulfenimine series, the selective, synthesis of both (R)- and (S)-sulfinimine products (both up to 99% ee) can be achieved, with different UPOs affording products with opposite enantioselectivity. Both series represent additional applications of UPO technology to an ever-growing list of selective, practical and industrially relevant biotransformations.