SYNTHESIS OF BLOOD-GROUP SUBSTANCES .8. SYNTHESIS OF THE BRANCHED TRISACCHARIDE 2-ACETAMIDO-2-DEOXY-4-ORTHO-(ALPHA-L-FUCOPYRANOSYL)-3-ORTHO-(BETA-D-GALACTOPYRANOSYL)-D-GLUCOPYRANOSE

Reaction of 2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl bromide with benzyl 2-acetamido-4-O-allyl-6-O-benzyl-2-deoxy-α-D-glucopyranoside provided crystalline benzyl 2-acetamido-3-O-(2,3,4,6-tetra-O-acetyl-β-D- galacto-pyranosyl)-4-O-allyl-6-O-benzyl-2-deoxy-α-D-glucopyranoside in 87% yield. Deallylation followed by condensation with 1-O-(N-methyl)acetimidyl-2,3, 4-tri-O-benzyl-β-L-fucopyranose provided the crystalline derivative (13). The title trisaccharide was obtained after O-deacetylation followed by catalytic hydrogenolysis. Preparations of 2-acetamido-2-deoxy-3-O-(β-D- galactopyranosyl)-D-glucopyranose and 2-acetamido-2-deoxy-4-O-(α-L- fucopyranosyl)-D-glucopyranose are reported.