Kinetic Resolution of Enantiomers in Racemic and Enantiomerically Enriched 2-Alkanols by Pseudomonas cepacia Lipase Catalyzed Transesterification with Isopropenyl Acetate in Organic Solvent

Abstract

Kinetic resolution of enantiomers in racemic and enantiomerically enriched 2-alkanols by Pseudomonas cepacia lipase catalyzed transesterification has been studied using isopropenyl acetate as an acetylating reagent, six alcohols and different organic solvents. The optical resolution data did not fit the previously reported theory: the enantioselectivity (E for the homocompetitive reaction) showed the maxima against the extent of conversion (c) in all systems studied and its correlation was different depending on the substrate and solvent. The optical resolution of (S)-2-alkanol with above 95% of enantiomeric excess (ee) was attained by controlling c. Low or moderate ee was observed in the resolution of (R) isomer from the racemate owing to low or moderate enantioselectivity. The resolution from enantiomerically enriched alcohol was carried out: the ee values of the resolved alcohols showed an excellent agreement with those determined by the previously reported equations using the optical resolution data and (R)- and (S)-2-alkanols with high ee could be resolved by controlling c and the initial optical purity of the substrate. Optically pure (R)- and (S)-2-octanols (ee≥99%) were resolved from racemic 2-octanol by repeating the transesterification three times and twice, respectively.