Enzymatic optical resolution of a synthetic pyrethroid alcohol. Enantioselective transesterification by lipase in organic solvent

Abstract

Abstract To obtain ( S )‐4‐methyl‐1‐heptyn‐4‐en‐3‐ol [( S )‐ 1a ], enzymatic enantioselective esterification of ( R,S )‐ 1a in organic solvent was examined. Pseudomonas lipase catalyzed the transesterification of ( R,S )‐ 1a with vinyl acetate in n ‐hexane, and gave ( S )‐ 1a and the corresponding acetate of ( R )‐ 1a with good enantioselectivity and high reaction rate. The reaction was accelerated by increasing the hydrophobicity of the organic solvent used as reaction medium and decreasing the water content of the reaction mixture. Under optimum conditions, ( S )‐ 1a of 99% ee was obtained at a conversion ratio of 68.6%. A kinetic udy revealed that the enzymatic reaction proceeded under the ping‐pong mechanism involving the acyl‐enzyme as an intermediate.