Alberto B. Zanlungo

Proton and carbon-13 nuclear magnetic resonance studies on methyl (methyl d-galactosid)uronates and their per-O-acetyl derivatives

Abstract The 1H- and 13C-n.m.r. spectra of the anomeric methyl (methyl d -galactosid)uronates, as well as the 1H-n.m.r. spectra of their acetyl derivatives, were analyzed. The spectra of the unacetylated d -galactopyranosiduronates showed good correlation with those of the corresponding anomeric d -galactopyranuronic acids and their methyl esters, and with those of the anomeric methyl d -galactopyranosides. From the values of the chemical shifts and coupling constants, it was concluded that the anomeric methyl (methyl d -galactopyranosid)uronates and their corresponding peracetates are in the 4C1( d ) conformation. The chemical shifts in the 13C-n.m.r. spectra show good correlation with those of the methyl d -galactosides. The signals of the furanose derivatives appear at fields lower than those of the corresponding pyranose compounds.

Acyl migrations in acylated monosaccharides. Formation of N-acetyl-β-D-galactofuranosylamine

Abstract The conformational and steric factors that determine the different contributions of the acyl groups to the formation of 1,1-bis(acylamido)-1-deoxyalditols by the ammonolysis of acyl esters of carbohydrates of different structures are discussed. The isolation and structure of N -acetyl β- D -galactofuranosylamine, obtained by such a reaction, are reported, and the conformation of this sugar and that of the N -acetyl-α- D -glucofuranosylamine previously described are considered on the basis of n.m.r. data.

The formation of N-acylglycosylamines of some monosaccharides. D-mannose and L-rhamnose derivatives

Abstract The factors that determine the favored formation of furanoid rings in the N -acylglycosylamines obtained by ammonolysis of O -acyl derivatives of some monosaccharides are discussed. The isolation and structure of N -acetyl-α- and -β- D -mannofuranosylamine, N acetyl-α- D - mannopyranosylamine, N -acetyl-α- L -rhamnopyranosylamine, and N acetyl-α- L -rhamnofuranosylamine are reported, and the conformation of the last two compounds is discussed on the basis of data from n.m.r. spectroscopy.

The reaction of ammonia with acetyl derivatives of gentiobiose

Abstract The reaction of aqueous ammonia with octa- O -acetylgentiobiose gives 1,1-bis-(acetamido)-1-deoxy-6- O -β- D -glucopyranosyl- D -glucitol ( 1 ) and N -acetyl-6- O -β- D -glucopyranosyl-β- D -glucofuranosylamine ( 3 ). The structure of the furanoid compound 3 was demonstrated by methylation and hydrolysis techniques, and its anomeric configuration through periodate oxidation and borohydride reduction.

The reaction of ammonia with acylated disaccharides. Part IX. Acetyl derivatives of melibiose

The reaction of methanolic or aqueous ammonia with octa-O-acetyl-β-melibiose gives N-acetyl-6-O-α-D-galactopyranosyl-β-D-glucofuranosylamine (I) and 1,1-bis(acetamido)-1-deoxy-6-O-α-D-galactopyranosyl-D-glucitol (IV). The structure of the furanoid compound was demonstrated by oxidation with periodate. The factors which determine the different yields of these products in both media are discussed and the yields are compared with those of nitrogenated products obtained by ammonolysis of acetates of 1,4-linked disaccharides.