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

Herein, we communicate a concise synthetic strategy for the first total synthesis of the <i>O</i>-antigenic tetrasaccharide repeating unit of <i>Acinetobacter lwoffii</i> EK30A polysaccharide. The structurally unique tetrasaccharide possesses three consecutive 1,2-<i>cis</i>-glycosidic linkages and two rare sugar units, <i>i</i>.<i>e</i>., d-Fuc<i>p</i>NAc and d-Qui<i>p</i>4NAc. 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.