Regioselective glycosylation of 4,6-O-benzylidenated glucopyranosides.

Regioselective glycosylation with allyl 4,6-O-benzylidene-alpha,beta-D-glucopyranoside or methyl 4,6-O-benzylidene-alpha,beta-D-glucopyranoside as the acceptor was investigated. It was found that the regioselectivity depends upon donor size and anomeric configuration of the acceptor, i.e., with a monosaccharide donor and an alpha-form acceptor, the (1-->3)-linked product was obtained predominantly or exclusively, while with disaccharide or trisaccharide donors and either an alpha or beta form acceptor, the (1-->2)-linked oligosaccharides were the only products.