Catalytic Stereoselective Glycosidation with Glycosyl Diphenyl Phosphates: Rapid Construction of 1,2‐ cis ‐α‐Glycosidic Linkages

A commercially available 0.1  M solution of HClO 4 in dioxane has been shown to catalyze the glycosidation of glycosyl diphenyl phosphates. The per‐ O ‐benzyl‐protected glucosyl and galactosyl donors and the 3,4,6‐tri‐ O ‐acetyl‐2‐azido‐2‐deoxygalactosyl donor each react with a range of acceptor alcohols in the presence of 0.05–0.2 equiv of HClO 4 in dioxane/Et 2 O (1:1) to afford glycosides in good yields with good to excellent α selectivities. The synthetic utility of this glycosidation method was demonstrated by a stereoselective synthesis of the α‐galactosylceramide KRN7000, an activator of natural killer (NK) T cells through CD1d molecules.