A facile synthesis of 1′-C-alkyl-α-disaccharides from 1-C-alkyl-hexopyranoses and methyl 1-C-methyl-hexopyranosides

Direct O-glycosidations using the 1-C-alkyl-2,3,4,6-tetra-O-benzyl-hexopyranoses as the glycosyl donors were carried out with a catalytic amount (0.2 equiv.) of trimethylsilyl trifluoromethanesulfonate (TMSOTf). The glycosidations proceeded α-stereoselectively and furnished the corresponding 1′-C-alkyl-α-disaccharides in 71–90% yields. The O-transglycosidations from the benzylated and acetylated methyl 1-C-methyl-α-hexopyranosides to the corresponding 1′-C-methyl-α-O-disaccharides were also examined, respectively. These transglycosidations took place on α-stereoselectivity and provided the 1′-C-methyl-α-O-disaccharides as the sole products, implying that no neighboring group participation occured in the reactions.