Enzymatic synthesis of dimeric and trimeric sugar-fatty acid esters

A new approach to the preparation of dimeric (gemini) and trimeric sugar fatty acid esters has been developed. It was shown that immobilized Candida antarctica lipase (Novozyme) readily catalyzes acylation of 1,2:3,4-di- O-isopropylidene -D-galactopyranose and methyl-α -D-glucopyranoside with 2-bromomyristic acid, with the reaction rate being about three times slower than that observed with myristic acid. However, virtually no product was detected after incubating this enzyme with 2-bromomyristic acid and 4- O-(3′,4′- O-isopropylidene-β -D-galactopyranosyl)-2,3:5,6-di- O-isopropylidene-1,1-di- O-methyl -D-glucose (lactose tetra-acetal) for 4 days. On the contrary, Mucor miehei lipase (Lipozyme) catalyzed the formation of 6′- O-(2-bromomyristoyl)-4- O-(3′,4′- O-isopropylidene-β -D-galactopyranosyl)-2,3:5,6-di- O-isopropylidene-1,1-di- O-methyl -D-glucose at preparatively useful rates, although it was found to be inferior to Novozyme in the acylation of the monosaccharide-based substrates. The products obtained after enzymatic transformation were chemically dimerised with dicarboxylic acids, and after deprotection, in the case of 1,2:3,4-di- O-isopropylidene -D-galactopyranose and lactose tetra-acetal esters, the desired gemini were obtained in reasonable overall yields. A trimeric sugar ester surfactant was prepared in a similar fashion in just one step by reacting 6- O-(2-bromomyristoyl) methyl-α -D-glucoside with 1,3,5- tris (4-carboxybutyloxy) benzene.