1,2-Cis selective glycosylation with glycosyl fluoride by using a catalytic amount of trifluoromethanesulfonic acid (TfOH) in the coexistence of molecular sieve 5Å (MS5Å)

Stereoselective glycosylation of several glycosyl accepters with 2,3,4,6-tetra-O-benzyl-beta -D-glucopyranosyl fluoride was successfully carried out in diethyl ether by using a catalytic amount of trifluoromethanesulfonic acid (TfOH) in the coexistence of molecular sieve 5 Angstrom (MS5 Angstrom) to afford predominantly the corresponding alpha -linked disaccharides in high yields, which was applied to one-pot sequential syntheses of trisaccharides.