Synthesis of the methyl α-glycosides of some isomalto-oligosaccharides specifically deoxygenated at position C-3

Methyl α-isomaltoside and methyl α-isomaltotrioside specifically deoxygenated at position C-3 of various glucopyranosyl units were synthesized by condensation of either 1,6- di-O- acetyl-2,4-di-O- benzyl-3-deoxy-α,β- d -ribo- hexopyranose (7) or 1,6- di-O- acetyl-2,3,4-tri-O- benzyl-α,β- d-glucopyranose [mediated by silver perchlorate and tin(IV) chloride] with suitably blocked derivatives of methyl α- d-glucopyranoside, its 3-deoxy analog (6), or methyl 3′-deoxy α-isomaltoside (10), respectively.