Chemo-Enzymatic Synthesis of (R)- and (S)-2-Hydroxy-4-phenylbutanoic Acid via Enantio-Complementary Deracemization of (±)-2-Hydroxy-4-phenyl-3-butenoic Acid Using a Racemase-Lipase Two-Enzyme System

Deracemization of (±)-2-hydroxy-4-phenylbut-3-enoic acid was accomplished by lipase-catalyzed kinetic resolution coupled to mandelate racemase-mediated racemization of the non-reacting substrate enantiomer. Stepwise cyclic repetition of this sequence led to a single enantiomeric product, the stereochemical outcome of which could be controlled by switching between lipasecatalyzed acyl-transfer/ester hydrolysis reactions. Both enantiomeric products were easily transformed into (R)- and (S)-2hydroxy-4-phenylbutanoic acid, important building blocks for ACE-inhibitors.