Solvent-free lipase-catalyzed thioesterification and transthioesterification of fatty acids and fatty acid esters with alkanethiols in vacuo

Palmitic acid hexadecylthioester and other long-chain acyl thioesters have been prepared in high yield (80-85%, purity >98%) by solvent-free lipase-catalyzed thioesterification of fatty acids with alkanethiols in vacuo, A lipase B preparation from Candida antarctica was more effective than a lipase preparation from Rhizomucor miehei and, particularly, those from papaya latex and porcine pancreas; Lipase-catalyzed transthioesterifcation of fatty acid methyl esters with alkanethiols was less effective than thioesterification for the preparation of acyl thioesters. However, in transthioesterification, a lipase preparation from R. miehei was more effective than a lipase B preparation from C. antarctica. Lipases from papaya latex and porcine pancreas led to moderate conversions to acyl thioesters in both thioesterification and transthioesterification reactions, whereas only small proportions of thioesters were formed using lipase from Rhizopus arrhizus. Lipases from Chromobacterium viscosum and Candida rugosa were not effective at all.