Synthetic studies on the carbohydrate moiety of the antigen from the parasite Echinococcus multilocularis

Stereocontrolled syntheses of branched tri-, tetra-, and pentasaccharides displaying a Galβ1→3GalNAc core in the glycan portion of the glycoprotein antigen from the parasite Echinococcus multilocularis have been accomplished. Trisaccharide Galβ1→3(GlcNAcβ1→6)GalNAcα1-OR (A), tetrasaccharide Galβ1→3(Galβ1→4GlcNAcβ1→6)GalNAcα1-OR (D), and pentasaccharides Galβ1→3(Galβ1→4Galβ1→4GlcNAcβ1→6)GalNAcα1-OR (E) and Gal β1→3(Galα1→4Galβ1→4GlcNAcβ1→6)GalNAcα1-OR (F) (R = 2-(trimethylsilyl)ethyl) were synthesized by block synthesis. The disaccharide 2-(trimethylsilyl)ethyl 2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl-(1→3)-2-azido-4-O-benzyl-2-deoxy-α-d-galactopyranoside served as a common glycosyl acceptor in the synthesis of the branched oligosaccharides. Moreover, linear trisaccharide Galβ1→4Galβ1→3GalNAcα1-OR (B) and branched tetrasaccharide Galβ1→4Galβ1→3(GlcNAcβ1→6)GalNAcα1-OR (C) were synthesized by stepwise condensation.