title: Synthesis of methyl O-(3-deoxy-3-fluoro-beta-D-galactopyranosyl)-(1----6)-beta-D- galactopyranoside and methyl O-(3-deoxy-3-fluoro-beta-D-galactopyranosyl)-(1----6)-O-beta-D- galactopyranosyl-(1----6)-beta-D-galactopyranoside.
abstract: Condensation of 2,4,6-tri-O-acetyl-3-deoxy-3-fluoro-alpha-D-galactopyranosyl bromide (3) with methyl 2,3,4-tri-O-acetyl-beta-D-galactopyranoside (4) gave a fully acetylated (1----6)-beta-D-galactobiose fluorinated at the 3'-position which was deacetylated to give the title disaccharide. The corresponding trisaccharide was obtained by reaction of 4 with 2,3,4-tri-O-acetyl-6-O-chloracetyl-alpha-D-galactopyranosyl bromide (5), dechloroacetylation of the formed methyl O-(2,3,4-tri-O-acetyl-6-O-chloroacetyl-beta-D-galactopyranosyl)-(1----6) -2,3, 4-tri-O-acetyl-beta-D-galactopyranoside to give methyl O-(2,3,4-tri-O-acetyl-beta-D-galactopyranosyl)-(1----6)-2,3, 4-tri-O-acetyl-beta-D-galactopyranoside (14), condensation with 3, and deacetylation. Dechloroacetylation of methyl O-(2,3,4-tri-O-acetyl-6-O-chloroacetyl-beta-D-galactopyranosyl)-(1----6) -O-(2,3 , 4-tri-O-acetyl-beta-D-galactopyranosyl)-(1----6)-2,3,4-tri-O-acetyl-beta -D- galactopyranoside, obtained by condensation of disaccharide 14 with bromide 5, was accompanied by extensive acetyl migration giving a mixture of products. These were deacetylated to give, crystalline for the first time, the methyl beta-glycoside of (1----6)-beta-D-galactotriose in high yield. The structures of the target compounds were confirmed by 500-MHz, 2D, 1H- and conventional 13C- and 19F-n.m.r. spectroscopy.
mesh_terms: D002236:Carbohydrate Conformation; D055598:Chemical Phenomena; D002621:Chemistry; D002855:Chromatography, Thin Layer; D004187:Disaccharides / Q000138:chemical synthesis*; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D014312:Trisaccharides / Q000138:chemical synthesis*
chemical_list: D004187:Disaccharides; D007202:Indicators and Reagents; D014312:Trisaccharides; C046975:methyl-O-(3-deoxy-3-fluorogalactopyranosyl)(1-6)galactopyranosyl(1-6)galactopyranoside; C046974:methyl O-(3-deoxy-3-fluorogalactopyranosyl)(1-6)galactopyranoside