Total Synthesis of a Rare-Sugar-Enriched O-Antigenic Tetrasaccharide Repeating Unit of Acinetobacter lwoffii EK30A

Abstract

Herein, we communicate a concise synthetic strategy for the first total synthesis of the O-antigenic tetrasaccharide repeating unit of Acinetobacter lwoffii EK30A polysaccharide. The structurally unique tetrasaccharide possesses three consecutive 1,2-cis-glycosidic linkages and two rare sugar units, i.e., d-FucpNAc and d-Quip4NAc. All functionalized monosaccharides were efficiently synthesized from naturally abundant and inexpensive d-galactose to make the synthetic route affordable and convenient. The tetrasaccharide was synthesized using highly stereoselective, convergent (1 + 2 + 1) and carefully optimizing a high-yielding glycosylation strategy.