The kinetic study on lipase-catalyzed asymmetric alcoholysis of α-cyano-benzyl acetate in organic media

Optically active mandelonitrile was synthesized by the lipase-catalyzed asymmetric alcoholysis of α-cyano-benzyl acetate in organic media. Through screening, the preferable system for the asymmetric reaction were: lipase Alcaligenes sp., tetrahydrofuran and methanol. Effects of various parameters were studied to deduce the kinetics and mechanism of the reaction. The optimal temperature was 40 °C. The external diffusion limitation could be excluded by raising the rotation speed and the internal diffusion could be ignored. The experimental results indicated that the decomposition of the mandelonitrile was the main reason of the decrease of the yield and e.e. value and benzaldehyde could greatly inhibit the enzyme activity. The kinetics was found to obey the Ping-Pong bi-bi mechanism with substrate inhibition of methanol.