Glycosyl 6-nitro-2-benzothiazoate.: A highly efficient donor for β-stereoselective glycosylation

Highly beta-stereoselective glycosylations of glycosyl acceptors having a primary hydroxyl group by using a novel glycosyl donor, alpha-glycosyl 6-nitro-2-benzothiazoate (3), proceeded smoothly in the presence of a catalytic amount of trifluoromethanesulfonic acid (TfOH) in CH2Cl2 at -78degreesC to afford the corresponding glycosides in high yields. The donor 3 gave beta-saccharides more dominantly compared with those using other alpha-glycosyl donors such as thioform- and trichloroacet-imidates or fluoride under the same conditions.