LIPASE-CATALYZED KINETIC RESOLUTION OF GAMMA-HYDROXY PHENYL SULFONES

Lipase PS (from Pseudomonas cepacia) catalyzed the enantioselective transesterification of racemic gamma-hydroxy-alpha,beta-unsaturated phenyl sulfones 1 and their alpha,beta-saturated derivatives 3 with vinyl acetate in an organic solvent (usually (i)Pr2O). Remarkably, in substrates 1 with (E)-stereochemistry, the enantioselectivity of the process was little influenced by the nature of the R chain. Hence, very high enantiomeric ratios (E greater-than-or-equal-to 45) were observed in substrates 1 bearing short (R = Me or Et), long (R = n-Cr6H13 or n-C10H21), bulky (R = (i)Pr), or functionalized R chains. The (R)-enantiomer was the fast-reacting enantiomer in all cases. Concerning the reactivity, the rate of the reaction decreased significantly with an increase in size or length of the R chain (reaction time for 50% conversion from 3.5 to 162 h). Less satisfactory enantioselectivities (E = 5-48) were obtained when the saturated substrates 3 were used instead of the corresponding alpha,beta-unsaturated alcohols 1.