Dynamic kinetic resolution of (rac)-1-Phenylethanol using lipase and a promising vanadium catalyst

The dynamic kinetic resolution (DKR) is an attractive method for the preparation of optically active sec-alcohols and esters that combines the enzyme-catalyzed KR of racemic alcohols with the in situ racemization of the slow-reacting enantiomer, providing optically enriched esters in quantitative yields. However, it is still necessary to search strategies for the racemization step that uses non-expensive catalysts under mild reaction conditions. In this study, we report a DKR of (rac)-1-phenylethanol combining the low-cost and readily available vanadyl sulfate (VOSO4) as racemization catalyst and CAL-B lipase. First, the vanadium-catalyzed racemization conditions were optimized, leading to a process at 50 °C with 50 mg of VOSO4 in heptane as solvent (4,6% ee of (S)-1-phenyletanol (62,5 mM) in 1 hour). Under these conditions, the DKR was performed using 20 mg of CAL-B and 125 mM of ethyl or vinyl acetate as acyl donor, which provided the corresponding ester with high optical purity.