The Influence of Organic Medium and Supports in the Resolution of (R,S)-Menthol Catalyzed by Lipases

In this study, various commercial and native lipases, free or immobilized, were used in the enantioselective resolution of (R,S)-menthol with vinyl acetate for the preparation of menthyl acetate. Lipase from Candida rugosa (AYL) was found to be the most appropriate. When the reaction was carried out at 35 oC, using 40 mg of AYL and a molar ratio of 1:2 (alcohol:ester), the values for the conversion degree, the enantiomeric excess of the substrate (ees) and product (eep) and the enantiomeric ratio (E) were 33.6, 50.3, > 99% and > 200, respectively. The results showed that the reaction was more efficient using toluene in comparison with other organic solvents or mixtures of toluene and ionic liquids (ILs). The best support for the AYL immobilization, was corn starch film. This system was used 4 times over 71 days of storage, and menthyl acetate was still obtained with good values of conversion degree, ees, eep, and E.