α-Glycosphingolipids via Chelation-Induced Anomerization of O- and S-Glucuronic and Galacturonic Acid Derivatives

Bacterial glycolipids containing either α-glucuronic acid or α-galacturonic acid residues have an important role in the innate-type immune response to Gram-negative bacteria. Synthesis of closely related compounds, including a novel α-SO2 glycolipid mimetic, is described from carbohydrate precursors where anomerization is a key step. Very high stereoselectivites (>97:3 in favor of α) were observed from O-glycoside precursors.