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

Stereocontrolled syntheses of branched tri-, tetra-, and pentasaccharides displaying a Gal beta 1-->3GalNAc core in the glycan portion of the glycoprotein antigen from the parasite Echinococcus multilocularis have been accomplished. Trisaccharide Gal beta 1-->3(GlcNAc beta 1-->6)GalNAc alpha 1-OR (A), tetrasaccharide Gal beta 1-->3(Gal beta 1-->4GlcNAc beta 1-->6)GalNAc alpha 1-OR (D), and pentasaccharides Gal beta 1-->3(Gal beta 1-->4Gal beta 1-->4GlcNAc beta 1-->6)GalNAc alpha 1-OR (E) and Gal beta1-->3(Gal alpha 1-->4Gal beta 1-->4GlcNAc beta 1-->6)GalNAc alpha 1-OR (F) (R = 2-(trimethylsilyl)ethyl) were synthesized by block synthesis. The disaccharide 2-(trimethylsilyl)ethyl 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl-(1-->3)-2-azido-4-O-benzyl-2-deoxy-alpha-d-galactopyranoside served as a common glycosyl acceptor in the synthesis of the branched oligosaccharides. Moreover, linear trisaccharide Gal beta 1-->4Gal beta 1-->3GalNAc alpha 1-OR (B) and branched tetrasaccharide Gal beta 1-->4Gal beta 1-->3(GlcNAc beta 1-->6)GalNAc alpha 1-OR (C) were synthesized by stepwise condensation.