The choice of activator is decisive for whether the α-(1→4)-linked disaccharide 2 α or the anomeric compound 2 β is formed from the prearranged glycoside 1. Other β-mannosylsaccharides can also be synthesized selectively by intramolecular glycosylation. Bn=benzyl, Bz=benzoyl, MeOTf= methyl trifluoromethanesulfonate, NIS=N-iodosuccinimide.