Synthesis and characterization of methyl 6-O-alpha- and -beta-D-galactopyranosyl-beta-D-galactopyranoside.
Sequential tritylation, acetylation and detritylation of methyl beta-D-galactopyranoside gave crystalline methyl 2,3,4-tri-O-acetyl-beta-D-galactopyranoside (4) and methyl 2,3,6-tri-O-acetyl-beta-D-galactopyranoside, the latter being the minor product resulting from acetyl migration. Reaction of 4 with 2,3,4,6-tetra-O-acetyl-alpha-D-galactosyl bromide in benzene, in the presence of mercuric cyanide and mercuric bromide, gave the alpha- and beta-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-alpha-D-galactopyranosyl-beta-D-galactopyranoside. O-Deacetylation of 9 gave the corresponding, beta-D-linked disaccharide methyl glycoside, the physical constants of which are discussed with respect to controversial data in the literature.
D002236:Carbohydrate Conformation; D055598:Chemical Phenomena; D002621:Chemistry; D004187:Disaccharides / Q000138:chemical synthesis*; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D008756:Methylgalactosides / Q000138:chemical synthesis*; D008759:Methylglycosides / Q000138:chemical synthesis*; D009904:Optical Rotation
D004187:Disaccharides; D007202:Indicators and Reagents; D008756:Methylgalactosides; D008759:Methylglycosides; C042212:methyl 6-O-D-galactopyranosyl-D-galactopyranoside