Mannosylation of several glycosyl acceptors with a novel mannosyl donor having the 6-nitro-2-benzothiazoate function at an anomeric position proceeded smoothly in the presence of a catalytic amount of tetrakis(pentafluorophenyl)boric acid [HB(C6F5)(4)] to afford the corresponding disaccharides in high yields with good to high beta-stereoselectivities.