Synthesis of a truncated bi-antennary complex-type N-glycan oxazoline; glycosylation catalysed by the endohexosaminidases Endo A and Endo M

The synthesis of a truncated complex N-glycan hexasaccharide oxazoline was achieved producing a substrate that was assayed as an activated donor for glycosylation catalysed by the endohexosaminidases Endo A and Endo M. For Endo M competitive product hydrolysis was seen to limit synthetic efficiency. In spite of its natural hydrolytic selectivity wild type Endo A was able to process the truncated complex N-glycan oxazoline, albeit with limited synthetic efficiency; notably the product was not a substrate for Endo A catalysed hydrolysis. Two Endo A mutants, E173Q and E173H, were also assayed, but were unable to process this oxazoline.