Asymmetric sulfoxidations mediated by α-chymotrypsin

The oxidation of aryl alkyl sulfides with H₂O₂ in aqueous solution is a reasonably facile reaction producing racemic sulfoxides. We show that in the presence of the hydrolytic enzyme α-chymotrypsin such a sulfoxidation is accelerated and, more importantly, becomes stereoselective. With phenyl isobutyl sulfide as a model, the chymotrypsin-mediated, highly asymmetric oxidation is shown to occur in the hydrophobic binding pocket of the enzyme active site. The stereoselectivity of the chymotrypsin-mediated sulfoxidations is correctly explained by means of structure-based molecular modeling of the enzyme-sulfide complexes.