Artificial carbohydrate antigens: the synthesis of a tetrasaccharide hapten,a Shigella flexneri O-antigen repeating unit

The 8-methoxycarbonyloctyl glycoside of the tetrasaccharide hapten, O-α-l-rhamnopyranosyl-(1→2)-O-α-l-rhamnopyranosyl-(1→3)-O-α-l-rhamnopyranosyl-(1→ 3)-2-acetamido-2-deoxy-β-d-glucopyranoside and the trisaccharide glycoside 8-methoxycarbonyloctyl O-α-l-rhamnopyranosyl-(1→3)-O-α-l-rhamnopyr-anosyl-(1→3)-2-acetamido-2-deoxy-β-d-glucopyranoside were synthesized by sequential Koenigs-Knorr reactions from monosaccharide units. The tetrasaccharide represents the complete skeletal repeating unit of Shigella flexneri serogroup Y lipopolysaccharide. Both oligosaccharide haptens are functionalized for covalent attachment to proteins, cell surfaces, and solid supports. ¹H-N.m.r. evidence for the conformations of these oligosaccharides in solution is presented and shown to be consistent with predictions based on the exo-anomeric effect