Studies in oligosaccharide chemistry. Part 8. Synthesis of lacto-N-triose I, a core chain trisaccharide of human blood-group substances

Abstract

Condensation of 4,6-di-O-acetyl-1,2-dideoxy-2′-methyl-3-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-α-D-glucopyranoso[2,1-d]-Δ^2′-oxazoline (4) with benzyl 6-O-allyl-2,4-di-O-benzyl-α-D-galactopyranoside (5) in the presence of toluene-p-sulphonic acid gave a protected trisaccharide (6) in 84% yield. Removal of the protecting groups gave the free trisaccharide β-D-Gal-(1 → 3)-β-D-GlcNAc-(1 → 3)-D-Gal (10), identical in properties with ‘Lacto-N-triose-I,’ a product of acidic hydrolysis of carbohydrates from human milk and blood-group substances. The carbohydrate sequence of the trisaccharide (10) is representative of the ‘core’ portion of blood-group substances.