High enantioselective resolution of racemic 2-arylpropionic acids in an enzyme membrane reactor

The kinetic resolution of racemic 2-(2-fluoro-4-biphenyl)propanoic and (4-isobutylphenyl)propanoic acids in an enzyme membrane reactor is presented. It has been accomplished in two ways: enzymatic esterification or enzymatic transesterification of the acid with vinyl acetate. The enzyme membrane was prepared by immobilisation of lipase, preferably from Pseudomonas sp., on a dense surface layer of an asymmetric polyamide capillary membrane. The immobilised enzyme was more stable as compared to the native one; its catalytic activity reached 27% of that of the lipase in the native state. The enzyme membrane exhibited a constant activity in the reactor for at least 1 month. Effect of various operation conditions on the enantioselectivity and reaction rate was examined. The best resolution of the acid racemates was achieved in the sequenced enantioselective processes: esterification and hydrolysis of the formed esters. This afforded enantiomerically pure products with the enantiomeric excess exceeding 99%.