4-(2'-Phenylethynylphenyl)phenyl glycosides as glycosylation donors

We have disclosed that 3,5-dimethyl-4-(2'-phenylethynylphenyl)phenyl (EPP) glycosides could be employed as glycosylation donors via an unprecedented activation mechanism. Here we report that the EPP glycosides without the 3,5-dimethyl groups, which were previously installed to prevent the plausible Friedel-Crafts-type side reactions, can also undergo glycosylation effectively. Employing such an EPP 2-azidoglucoside as donor, the construction of the challenging alpha-GlcN-(1 -> 4)-GlcA linkage is realized, leading to a heparin tri-saccharides precursor.