2-METHYLALKANOIC ACIDS RESOLVED BY ESTERIFICATION CATALYZED BY LIPASEFROM CANDIDA-RUGOSA - ALCOHOL CHAIN-LENGTH AND ENANTIOSELECTIVITY

Enantiomerically pure (R)-2-methyldecanoic acid and (S)-2-methyl-1-dec anol were prepared in a multi gram scale by esterification reactions c atalysed by lipase from Candida rugosa. The enantiomeric ratios (E-val ues) were determined as a function of the chain length of the alcohol used as the complementary substrate in cyclohexane. In the resolution of 2-methyldecanoic acid the highest value (E = 37 +/- 5) was obtained , when either 1-hexanol, 1-heptanol or 1-octanol were used. In contras t, when resolving 2-methyloctanoic acid, the E-values increased contin ually with increasing chain length of the alcohol used. 1-Hexadecanol gave the highest value: E > 100. The E-values were determined from the enantiomeric excess (ee) of the product, at, a conversion below 0.4. After two consecutive esterification reactions enantiomerically pure ( R)-2-methyldecanoic acid, > 99.8% ee, and after subsequent reduction o f the ester produced, (S)-2-methyl-1-decanol, 96.7% ee, were obtained.