title: Preparative-scale kinetic resolutions catalysed by microbial lipases immobilised in AOT-stabilised microemulsion-based organogels: cryoenzymology as a tool for improving enantioselectivity.
abstract: 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 esterification with decanoic acid have been performed using Chromobacterium viscosum (CV) lipase. CV lipase is highly enantioselective in favour of the (R)-(-) isomer of octan-3-ol, but the enantioselectivity is both reversed and decreased by the introduction of unsaturation at the 1-position. Marked improvements in enantioselectivity were achieved by carrying out the reaction at -15 degrees C, the enantiomeric excess of the ester product increasing from 47% (E = 3) to 73% (E = 8) in the 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 approximately 85% (E approximately 15) for octan-3-ol, and there was no marked improvement in enantioselectivity even at -15 degrees C. Apparent activation energies for the esterification using decanoic acid of octan-3-ol, 1-octen-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 energy of 21 kJ mol-1 for the esterification of octan-1-ol with decanoic acid using CV lipase under the same conditions. Lipases from Pseudomonas (Fluka), Pseudomonas (Genzyme) and lipoprotein lipase ex Microbial (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 performed in a 1 dm3 batch reactor in which 200 cm3 of pelleted MBG (containing 350 mg of CV lipase) was used repeatedly for the kinetic resolution of octan-3-ol.
mesh_terms: D002151:Calorimetry; D002175:Candida / Q000201:enzymology*; D002841:Chromatiaceae / Q000201:enzymology*; D004655:Emulsions; D004800:Enzymes, Immobilized / Q000378:metabolism*; D005780:Gelatin; D005782:Gels; D007700:Kinetics; D008049:Lipase / Q000378:metabolism*; D008071:Lipoprotein Lipase / Q000378:metabolism*; D009904:Optical Rotation; D011549:Pseudomonas / Q000201:enzymology*; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D004655:Emulsions; D004800:Enzymes, Immobilized; D005782:Gels; D005780:Gelatin; D008049:Lipase; D008071:Lipoprotein Lipase