Lipase-catalyzed solid-phase synthesis of sugar esters, IV: Selectivity of lipases towards primary and secondary hydroxyl groups in carbohydrates

The acylation of several pyranoses and fructose with fatty acids by lipases in a solid-phase system was investigated. Highest selectivity was found using lipase from candida antarctica B immobilized on polypropylene EP 100. For beta-D(+)-glucose 98% mono- and 2% diacylation using palmitic acid in t-butanol were observed. Much lower selectivities were achieved with D-(+)-mannose (75% monoacylation) and D(+)-galactose (50% monoacylation), which was explained by the different orientation of the C2-hydroxyl groups. The selectivity in the acylation of fructose was significantly influenced by the fatty acid chain length and the organic solvent. Monoacylation was favored in less hydrophobic solvents (e.g. t-butanol) using long chain fatty acids.