Efficient Synthesis of Antigenic Trisaccharides Containing <i>N</i>‐Acetylglucosamine: Protection of NHAc as NAc₂

Abstract

The antigenic trisaccharides, α‐gal epitope and H antigen, containing N ‐acetyl‐ d ‐glucosamine (GlcNAc) were synthesized using a diacetyl strategy, in which NHAc is tentatively converted to NAc 2 during oligosaccharide construction. Acetylation of NHAc in GlcNAc significantly improved the reactivity in glycosylation reactions. The diacetyl strategy allowed to achieve the efficient synthesis of α‐gal through a sequential one‐pot and one‐flow procedure. Meanwhile, H antigen was synthesized by stepwise elongation from the reducing end side of GlcNAc. The enhancement of the reactivity by NAc 2 protection was observed in both glycosylations at proximal and distal positions to GlcNAc. This diacetyl strategy is expected to be applicable to the synthesis of a wide range of glycans.