SYNTHESIS OF BLOOD-GROUP SUBSTANCES .7. SYNTHESIS OF THE BRANCHED TRISACCHARIDE-O-ALPHA-L-FUCOPYRANOSYL-(1-]3)-[O-BETA-D-GALACTOPYRANOSYL-(1-]4)]-2-ACETAMIDO-2-DEOXY-D-GLUCOPYRANOSE

Reaction of 2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl bromide with benzyl 2-acetamido-3-O-allyl-6-O-benzyl-2-deoxy-α-D-glucopyranoside in 1,2-dichloroethane in the presence of mercuric bromide and molecular sieves (4 Å) provided crystalline benzyl 2-acetamido-4-O-(2,3,4,6-tetra-O-acetyl- β-D-galactopyranosyl)-3-O-allyl-6-O-benzyl-2-deoxy-α-o- glucopyranoside in 77% yield. Deallylation with chloro(tristriphenylphosphine)- rhodium(I) followed by condensation with 2,3,4-tri-O-benzyl-α-L- fucopyranosyl bromide provided the derivative (14). The title trisaccharide was obtained after O-deacetylation followed by catalytic hydrogenolysis.