title: Synthesis of methyl glycosides of beta-(1----6)-linked D-galactobiose, galactotriose, and galactotetraose having a 3-deoxy-3-fluoro-beta-D-galactopyranoside end-residue.
abstract: Methyl 2,4-di-O-acetyl-3-deoxy-3-fluoro-beta-D-galactopyranoside was synthesized by sequential tritylation, acetylation, and detritylation of methyl 3-deoxy-3-fluoro-beta-D-galactopyranoside, and used as the initial nucleophile in the synthesis of methyl beta-glycosides of (1----6)-beta-D-galacto-biose, -triose (20), and -tetraose (22) having a 3-deoxy-3-fluoro-beta-D-galactopyranoside end-residue. The extension of the oligosaccharide chains, to form the internal units in 20 and 22, was achieved by use of 2,3,4-tri-O-acetyl-6-O-bromoacetyl-alpha-D-galactopyranosyl bromide as a glycosyl donor, and mercuric cyanide or silver triflate as the promotor. While fewer by-products were formed in the reactions involving mercuric cyanide, the reactions catalyzed by silver triflate were stereospecific and yielded only the desired beta (trans) products.
mesh_terms: D002236:Carbohydrate Conformation; D005690:Galactose; D006027:Glycosides / Q000138:chemical synthesis*; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D008745:Methylation; D009844:Oligosaccharides / Q000138:chemical synthesis*; D009904:Optical Rotation
chemical_list: D006027:Glycosides; D007202:Indicators and Reagents; D009844:Oligosaccharides; D005690:Galactose