Prearranged glycosides, part 10. Intramolecular glycosylation with cellobiosyl, lactosyl, and maltosyl donors

Acetyl protected 1,2-O-(1-methoxyethylidene)-disaccharides 1 of maltose, ce llobiose, and Lactose, respectively were converted via the corresponding be nzyl protected couterparts 2, the benzyl protected phenyl 2-O-acetyl-3 and 2-O-unprotected 1-thio-glycoside disaccharides 4 into 2-O-succinoylated dis accharides 5. The latter were esterified with benzyl 2-O-benzoyl-4,6-di-O-b enzylidene-alpha-D-glucopyranoside (6) to afford succinyl linked derivative s 7 the benzylidene groups of which were regioselectively opened to give pr earranged glycoside trisaccharides 8. Intramolecular glycosylation of the l atter with N-iodosuccinimide resulted in exclusive formation of the corresp onding alpha-(1-->)-linked trisaccharides 9. No influence of the donor moie ty on the diastereoselectivity of the intramolecular glycosylation was obse rved.