Synthesis and characterization of methyl 6- O-α- and -β- d-galactopyranosyl-β- d-galactopyranoside

Abstract

Sequential tritylation, acetylation and detritylation of methyl β- d-galactopyranoside gave crystalline methyl 2,3,4-tri- O-acetyl-β- d-galactopyranoside ( 4) and methyl 2,3,6-tri- O-acetyl-β- d-galactopyranoside, the latter being the minor product resulting from acetyl migration. Reaction of 4 with 2,3,4,6-tetra- O-acetyl-α- d-galactosyl bromide in benzene, in the presence of mercuric cyanide and mercuric bromide, gave the α- and β- d-(1→6)-linked disaccharides ( 7 and 9, respectively) in high yield, and their structure was confirmed by 1H- and 13C-n.m.r. 1d. and 2d. spectroscopy. O-Deacetylation of 7 gave the hitherto unknown, crystalline methyl 6- O-α- d-galactopyranosyl-β- d-galactopyranoside. O-Deacetylation of 9 gave the corresponding, β- d-linked disaccharide methyl glycoside, the physical constants of which are discussed with respect to controversial data in the literature.