Synthetic Study of N-glycans

Asparagine-linked oligosaccharides (N-glycans) have high diversity and are involved in a variety of important physiological events. To reveal the molecular basis of N-glycans functions, we synthesized N-glycans. We employed convergent synthetic route: two non-reducing end donors were connected to the reducing-end acceptor at the blanched mannose. Intermolecular hydrogen bonds involving acetamide were discovered to reduce the reactivity in glycosylations: the protection of NHAc as NAc2 improved the reactivity. We also found that ether solvents enhanced the yields of key glycosylations between large fragments by stabilization of the oxocarbenium ion intermediate. To improve the alpha-selectivity of these glycosylations, we manipulated the remote participation because neighbouring group participation from 2 position of donor was not available.