Efficient kinetic resolution of (±)-menthol by a lipase from Thermomyces lanuginosus.

A lipase from Thermomyces lanuginosus (Lipozyme TL IM) exhibited high enantioselectivity for kinetic resolution of (±)-menthol in organic solvent. The various reaction parameters affecting the conversion and enantioselectivity were studied. The optimum reaction conditions for the transesterification reaction were found with vinyl acetate in the solvent of methyl tert-butyl ether with a vinyl acetate:(±)-menthol molar ratio of 5:1 and an enzyme concentration of 200 g/L at 30 °C. In these conditions, (-)-menthyl acetate with 99.3% enantiomeric excess was obtained, whereas the conversion was 34.7% with the reaction time of 12 H at the substrate concentration of 0.5 M. In addition, the enzyme allowed the substrate loading to be increased up to 1.5 M without the decrease of the enantioselectivity. These results indicated that Lipozyme TL IM was a promising biocatalyst in the resolution of (±)-menthol.