Synthesis of allyl 3-deoxy- and 4-deoxy-β-D-galactopyranoside and simultaneous preparations of Gal(1 → 2)- and Gal(1 → 3)-linked disaccharide glycosides

Article abstract of DOI:10.1016/0008-6215(94)84276-0

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-β-D-xylo-hexopyranoside and several disaccharide glycosides having Gal(1 → 2) and Gal(1 → 3) linkages. The β-linked Gal disaccharide isomers were produced using 2,3,4,6-tetra-O-acetyl-α-D- galactopyranosyl bromide as glycosyl donor and the 4,6-O-benzylidene derivatives of allyl β-D-galactopyranoside, α-D-glucopyranoside, α-D- mannopyranoside, and 2-acetamido-2-deoxy-α-D-galactopyranoside as acceptors. 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(α, 1 → 2)Gal and Gal(α, 1 → 3)Gal disaccharide glycosides were made using the same strategy, but employing the 1-trichloro-acetimidate 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(α, 1 → 2)Gal and Gal(α, 1 → 3)Gal derivatives as major products, but the former gave the Gal(β, 1 → 2)Gal isomer as the major product. 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-β-D-xylo-hexophyranoside and several disaccharide glycosides having Gal(a→2)Gal and Gal(1→3) linkages. The β-linked Gal disaccharide isomers were produced using 2,3,4,6-tetra-O- acetyl-α-D-galactopyronosyl bromide as glycosyl donor and the 4,6-O-benzylidene deriatives of allyl β-D-galactopyranoside, α-D-glucopyranoside, α-D-manopyranoside, and 2-acetamido-2-deoxy-α-D-galactopyranoside as acceptors. Only the Gal(2→3)-linked disaccharide was obtained when the benzylidene derivatives of the mannopyranosde and 2-acetamido-2-deoxygalactopyranoside were used. Attempts at the preparation of Gal(α, 1→2)Gal and Gal(α, 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(α, 1→2)Gal and Gal(α, 1→3)Gal derivatives as major products, but the former gave the Gal(β, 1→2)Gal isomer as the major product.