LIPASE-CATALYZED ENANTIOMERIC SYNTHESIS OF CITRONELLYL BUTYRATE

Lipases from Candida rugosa, Pseudomonas fluorescens and Rhizopus japo nicus were employed in direct sterification of the different optical i somers of citronellol with butyric acid both with and without addition al organic solvent. In systems with C. rugosa lipase and without addit ion of organic solvent, the highest ester yields in 18 h reaction were 98% for R(+)-citronellol at 12% water content and 67% for S(-)-citron ellol at 18% water content, respectively. In comparison, a yield of on ly 65% was obtained with at otherwise similar conditions but with an o ptimum water content of about 18%. No ester synthesis took place in 'd ry' n-hexane of about 1.2 ppm of water. When water content was increas ed to 0.1% in n-hexane system, rapid esterification occurred also in n -hexane with all three substrates, but there was little enantioselecti vity. Both P. fluorescens and R. japonicus lipases exhibited somewhat higher initial rates for citronellyl butyrate synthesis, with greater than 80% yield with R(+)-citronellol in 4 h.