PREPARATIVE-SCALE KINETIC RESOLUTIONS CATALYZED BY MICROBIAL LIPASES IMMOBILIZED IN AOT-STABILIZED MICROEMULSION-BASED ORGANOGELS - CRYOENZYMOLOGY AS A TOOL FOR IMPROVING ENANTIOSELECTIVITY

Gelatin-containing microemulsion based organogels have been used as an immobilisation matrix for lipases from a number of different sources. Kinetic resolutions of octan-3-ol, 1-octen-3-ol and 1-octyn-3-ol by e sterification with decanoic acid have been performed using Chromobacte rium viscosum (CV) lipase. CV lipase is highly enantioselective in fav our of the (R)-(-) isomer of octan-3-ol, but the enantioselectivity is both reversed and decreased by the introduction of unsaturation at th e 1-position. Marked improvements in enantioselectivity were achieved by carrying out the reaction at -15 degrees C, the enantiomeric excess of the eater product increasing from 47% (E = 3) to 73% (E = 8) in th e case of 1-octen-3-ol, and from 17% (E = 1.4) to 38% (E = 2.5) in the case of 1-octyn-3-ol. The enantiomeric excess was approximate to 85% (E approximate to 15) for octan-3-ol, and there was no marked improvem ent in enantioselectivity even at -15 degrees C. Apparent activation e nergies for the esterification using decanoic acid of octan-3-ol, 1-oc ten-3-ol and 1-octyn-3-ol by CV lipase were 32 kJ mol(-1), 31 kJ mol(- 1) and 41 kJ mol(-1), respectively. This compares to an activation ene rgy of 21 kJ mol(-1) for the esterification of octan-1-ol with decanoi c acid using CV lipase under the same conditions. Lipases from Pseudom onas (Fluka), Pseudomonas (Genzyme) and lipoprotein lipase ex Microbia l (Genzyme) also selectively esterified the (R)-(-) isomer of racemic octan-3-ol, the two Pseudomonas preparations yielding product with an enantiomeric excess of 90%. Candida cylindracea lipase did not exhibit activity in gelatin-containing MBGs. Large-scale syntheses were perfo rmed in a 1 dm(3) batch reactor in which 200 cm(3) of pelleted MBG (co ntaining 350 mg of CV lipase) was used repeatedly for the kinetic reso lution of octan-3-ol.