SYNTHESIS OF ALLYL 3-DEOXY-BETA-D-GALACTOPYRANOSIDE AND 4-DEOXY-BETA-D-GALACTOPYRANOSIDE AND SIMULTANEOUS PREPARATIONS OF GAL(1-]2) AND GAL(1-]3)-LINKED DISACCHARIDE GLYCOSIDES

Syntheses of galactose derivatives that are useful in probing the binding specificity of galactose-specific lectins are reported. These include allyl 3-deoxy- and 4-deoxy-beta-D-xylo-hexopyranoside and several disaccharide glycosides having Gal(1 --> 2) and Gal(1 --> 3) linkages. The beta-linked Gal disaccharide isomers were produced using 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide as glycosyl donor and the 4,6-O-benzylidene derivatives of allyl beta-D-galactopyranoside, alpha-D-glucopyranoside, alpha-D-mannopyranoside, and 2-acetamido-2-deoxy-alpha-D-galactopyranoside as accepters. Only the Gal(1 -->, 3)-linked disaccharide was obtained when the benzylidene derivatives of the mannopyranoside and 2-acetamido-2-deoxygalactopyranoside were used. Attempts at the preparation of Gal(alpha, 1 -->, 2)Gal and Gal(alpha, 1 --> 3)Gal disaccharide glycosides were made using the same strategy, but employing the 1-trichloroacetimidate or 1-N-methylacetimidate of 2,3,4,6-tetra-O-benzyl-D-galactopyranose as the glycosyl donor. The latter imidate produced a mixture of Gal(alpha, 1 --> 2)Gal and Gal(alpha, 1--> 3)Gal derivatives as major products, but the former gave the Gal(beta, 1 --> 2)Gal isomer as the major product.