Convenient use of non-malodorous thioglycosyl donors for the assembly of multivalent globo- and isoglobosyl trisaccharides Original Research Article

New thioglycosyl donors (o-methoxycarbonylphenyl 2,3,4,6-tetra-O-benzyl-1-thio-β-d-galactopyranoside and its 6-O-acetyl analogue) were designed and used for the synthesis of glycoconjugate polymers carrying Gb3 [Gal(α1→4)Gal(β1→4)Glc] and isoGb3 [Gal(α1→3)Gal(β1→4)Glc] clusters as side chains. These donors scarcely evolved the unpleasant odor of thiophenols and showed a high α-anomeric selectivity in the galactosylation of p-nitrophenyl β-lactoside derivatives, although in moderate yields. The derived trisaccharides were converted to multivalent carbohydrate ligands and were subjected to a biological assay with Shiga toxins. The multivalent Gb3 ligand was highly active in inhibiting the toxicity, while the isoGb3 ligand showed no activity, indicating that Stx-I discriminates between the carbohydrate structures.