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

摘要

New thioglycosyl donors (o-methoxycarbonylphenyl 2,3,4,6-tetra-O-benzyl-1-thio-#beta#-D-galactopyranoside and its 6-O-acetyl analogue) were designed and used for the synthesis of glycoconjugate polymers carrying Gb_3[Gal(#alpha#->4)Gal(#beta#1->4)Glc] and isoGb3[Gal(#alpha#1->3)Gal(#beta#1->4)Glc] clusters as side chains. These donors scarcely evolved the unpleasant odor of thiophenols and showed a high #alpha#-anomeric selectivity in the galactosylation of p-nitrophenyl #beta#-lactoside derivatives, although in moderate yields. The derived trisaccharides were converted to multivalent carbonhydrate ligands and were subjected to a biological assay with Shiga toxins. The multivalent Gb_3 ligand was highly active in inhibiting the toxicity. while the isoGb_3 ligand showed no activity, indicating that Stx-I discriminates between the carbohydrate structures.