Synthesis of 4-O-d-Mannopyranosyl-α-d-glucopyranosides by Intramolecular Glycosylation of 6-O-Tethered Mannosyl Donors

A series of mannosyl donors linked via position 6 by a carbonate, oxalate, malonate, succinate, and phthalate tether, respectively, to position 3 of a glucoside and glucosamine acceptor afforded during intramolecular glycosylation, anomeric mixture of the corresponding disaccharides. The dependence of the diastereoselectivity on the glycosylation procedure, the solvent, and the blocking groups in comparison to an intermolecular mannosylation is studied.