Lipase‐catalyzed dynamic resolution of naproxen 2,2,2‐trifluoroethyl thioester by hydrolysis in isooctane

A lipase‐catalyzed enantioselective hydrolysis process under continuous in situ racemization of substrate by using trioctylamine as an organic base was developed for the production of (S)‐naproxen from racemic naproxen thioesters in isooctane. Naproxen 2,2,2‐trifluoroethyl thioester and 45°C were selected as the best substrate and temperature, respectively, by comparing the time‐course variations for the racemization of (S)‐naproxen thioesters containing an electron‐withdrawing group. A detailed investigation of the effect of trioctylamine concentration on the kinetic behaviors of the thioester in racemization and enzymatic reaction was conducted, in which more than 70% conversion of the racemate (or 67.2% yield of (S)‐naproxen) with ee_p value higher than 92% was obtained. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 120–126, 1999.