Lipase-catalyzed regioselective synthesis of steryl (6'-O-acyl)glucosides.

The regioselective acylation of cholesteryl beta-D-glucoside, at the C-6 of the glucose moiety, was achieved using microbial lipases in organic solvents. With palmitic acid as an acyl donor 81 or 63% conversions of cholesteryl glucoside to its 6'-O-palmitoyl derivative were obtained using Candida antarctica or Rhizomucor miehei enzymes, respectively. High yields (64-92%) were also obtained with fatty acids 6:0-22:0 and 16:1 (n-7). The synthesis of cholesteryl (6'-O-palmitoyl)glucoside was also achieved via transesterification, using mono-, di- and tri-palmitoylglycerols or methyl and ethyl palmitate as acyl sources. With R. miehei lipase transesterification between methyl palmitate (80 mM) and cholesteryl glucoside (1 mM) proceeded after 24 h with a nearly quantitative yield (97%).