Enantioselective esterification of 2-arylpropionic acids catalyzed by immobilized Rhizomucor miehei lipase

A systematic study of the enzymatic activity of immobilized lipase from Rhizomucor miehei (Lipozyme IM) in the enantioselective esterification of 2-arylpropionic acids has been carried out. The main variables controlling the process (enzyme amount, water amount, temperature, stirring speed, and type of organic solvent) were studied using factorial analysis. The negative effect of water amount is explained by means of water activity (a,) considerations. A new and easy to calculation parameter (Enantiomeric Factor, EF) is defined for evaluating the enantioselectivity of the reaction. Influence of the alcohol and acid moieties is also considered. Lipozyme IM shows S-(+) enantiorecognition in all cases, except for (R,S)-Ketoprofen, where the R-(-) stereobias is confirmed using pure enantiomers (V-R/V-S = 8). An explanation for this different enantiopreference is suggested by means of MD calculus.