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

Abstract

Syntheses of galactose derivatives that are useful in probing te 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( → 2) and Fal(1 →3) linkages. The β-linked Gal disaccharide isomers were produced using 2,3,4,6-tetra- O-acetyl-α-D-galactopyranosyl bromide, α-D-mannopyranoside, and 2-acetamido-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- 2deoxygalactopyranoside 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 employint the 1-trichloro-actimidate or 1- N-methylacetimidate of 2,3,4,6,-tetra- O-benzyl-C-galactopyranose as the glycosyl donor. The latter imidate produced a mixture of Gal(α, 1 » 3)Gal derivatives as major products, but the former gave the Fal(β, 1 » 2)Gal isomer as the major product.