Towards oligosaccharide libraries: A study of the random galactosylation of unprotected N-acetylglucosamine

A single reaction of an unprotected β-d-GlcNAc glycoside with tetra-O-acetyl-α-d-galactopyranosyl trichloroacetimidate in dioxane, catalyzed by BF3-etherate, was shown to yield all six possible Gal-GlcNAc disaccharides. This result is surprising not only because significant amounts of α-linked disaccharides were formed, despite the presence of a participating group at O-2 of the glycosyl donor, but also because glycosylation of the primary OH-6 is not the dominant reaction. These results suggest ‘random-glycosylation’ to be a valid strategy for the rapid production of oligosaccharide libraries.