Stannylene-mediated regioselective 6-O-glycosylation of unprotected phenyl 1-thioglycopyranosides
Faculty of Pharmaceutical, Biomedical and Veterinary Sciences. Pharmacy
European journal of organic chemistry. - Weinheim
, p. 2683-2691
A straightforward procedure is described for the synthesis of (1[RIGHTWARDS ARROW]6)-linked saccharides by regioselective glycosylation of unprotected glycosyl acceptors. Phenyl 1-thioglycopyranosides derived from D-glucose, D-galactose and D-mannose were treated with dibutyltin oxide to introduce a stannylene acetal, and then subjected to selective glycosylation at the 6-position with the KoenigsKnorr protocol. Peracylated glycosyl bromides of D-glucose, D-galactose, D-mannose and D-glucosamine were employed as the donors to give the corresponding (1[RIGHTWARDS ARROW]6)-linked disaccharides in moderate to good yields. The best results were obtained with glycosyl donors and acceptors derived from D-glucose and D-galactose. Fully acylated disaccharide thioglycosides could also serve as glycosyl donors for the regioselective coupling. Brominolysis and subsequent KoenigsKnorr coupling with the stannylene acetal of phenyl 1-thio-β-D-glucopyranoside gave rise to the corresponding (1[RIGHTWARDS ARROW]6)-linked trisaccharides in moderate yields.