Total Synthesis of a Rare-Sugar-Enriched -Antigenic Tetrasaccharide Repeating Unit of EK30A.

Herein, we communicate a concise synthetic strategy for the first total synthesis of the -antigenic tetrasaccharide repeating unit of EK30A polysaccharide. The structurally unique tetrasaccharide possesses three consecutive 1,2--glycosidic linkages and two rare sugar units, .., d-FucNAc and d-Qui4NAc. 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.