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 -> 4Gal beta 1 -> 6)GalNac alpha 1-OR(D), and pentasaccharides Gal beta 1 -> 3(Gal beta 1 -> 4Gal beta 1 -> 4Gl cNAc beta 1-6)GalNAc alpha 1-OR (E) and Gal beta 1-3(Gal alpha 1 -> 4Gal alpha 1 -> 4Gal alpha 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-P-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 oligosaccharicles. Moreover, linear trisaccharide Gal beta 1 -> Gal beta 1 -> 3GalNac alpha 1-OR (B) and branched tetrasaccharide Gal beta 1 -> Gal beta 1 -> 3(GalNac beta 1 -> 6)GalNac alpha 1-OR (C) were synthesized by stepwise condensation. (C) 2009 Elsevier Ltd. All rights reserved.