N. N. Malysheva

Synthesis of O-β-d-mannopyranosyl-(1→4)-O-α-l-rhamnopyranosyl-(1→3)-d-galactopyranose, the trisaccharide repeating-unit of the O-specific polysaccharide from Salmonella anatum

Abstract Glycosylation of 1,2:5,6-di- O -isopropylidene-α- d -galactofuranose with 2,3-di- O -acetyl-4- O -(2,3,4,6-tetra- O -acetyl-β- d -mannopyranosyl)-α- l -rhamnopyranosyl bromide, followed by removal of the protecting groups, gave O -β- d -mannopyranosyl-(1→4)- O -α- l -rhamnopyranosyl-(1→3)- d -galactose, which is the trisaccharide repeating-unit of the O-specific polysaccharide chain of the lipopolysaccharide from Salmonella anatum . The formation of the β- d -mannopyranosyl linkage was achieved by a glucose-mannose conversion via stereoselective reduction of the corresponding oxo-disaccharide.

A new stereospecific method for 1,2-cis-glycosylation

A new stereospecific method for 1,2-cis-glycosylation involves the reaction of 1,2-trans-glycosyl thiocyanates with sugar trityl ethers in the presence of triphenylmethylium perchlorate. The method has been applied to give disaccharide derivatives with (1----6), (1----3), and (1----2) linkages.

Novel highly stereospecific method of 1,2-cis-glycosylation. Synthesis of α-D-glucosyl-D-glucoses

Abstract Triphenylmethylium perchlorate-catalysed glycosylation of 2-, 3-, 4-, and 6-O-trityl-D-glucose derivatives with β-D-glucopyranosyl thiocyanates bearing a non-participating substituent at O-2 affords stereospecific derivatives of α-D-glucosyl-D-glucose

The synthesis of (1→4)-linked α-l-rhamnans

Abstract (1→4)-Linked α- l -rhamnans with d.p. 22 and 40 have been obtained by triphenylmethylium perchlorate-catalysed polycondensation of 3- O -acetyl-1,2- O -[1-( exo -cyano)ethylidene]-4- O -trityl- l -rhamnopyranose and 3- O -benzoyl-1,2- O -[1-( exo -cyano)ethylidene]-4- O -trityl- l -rhamnopyranose, respectively.

The effect of high pressure on the stereospecificity of the glycosylation reaction

At a pressure of 1.4 GPa and room temperature, the glycosylation of trityl ethers by 1,2-O-cyanoethylidene derivatives of sugars, and the polycondensation of the proper monomers in dichloromethane, proceed with absolute stereospecificity, giving rise to a 1,2-trans-glycosidic linkage, although, at the ambient pressure, the reactions studied reveal a rather low stereospecificity. The effect of high pressure on the stereospecificity of glycosidic linkage formation is explained as being due to the shift of the equilibrium between monocyclic glycosyl-cation and bicyclic acyloxonium cation towards the latter as the pressure is increased.

Stereospecific synthesis of 1,2-cis-glycosides of 2-amino sugars

The highly stereoselective synthesis of a 1,2-cis-glycosidic linkage is difficult and a satisfactory solution remains a problem in the synthetic chemistry of carbohydrates. Recently, we proposed a new approach to specific 1,2-cis-glycosylation, by using l,Ztruns-glycosyl thiocyanates with a non-participating substituent at C-2 as the glycosylation reagent’-3. We report now the application of this approach to the stereospecific synthesis of l,Zcis-glycosides of 2-amino sugars, which can also be regarded as a difficult problem [cf. ref. 41. The corresponding 1,2-truns-2-azido-2-deoxyglycosyl thiocyanate was used as glycosyl donor with subsequent conversion of the azido into an amino group. The stereospecific synthesis of 1,2-cis-glycosaminides is demonstrated by the synthesis of derivatives of a-D-glucosaminyl-o-glucoses with different types of glycosidic linkages. 3,4,6-Tri-0-acetyl-2-azido-2-deoxy-P-D-glu~pyranosyl thiocyanate (1) has been obtained by treatment of the known 3,4,6-tri-O-acetyl-2-azido-2-deoxy-a-D-glucopyranosyl bromide5 (5.6 mmol) with KSCN (16.9 mmol, dried in vacua at llO’C> in the presence of U-crown-6 (1.7 mmol, dried in vacua at 20°C) in acetone (6.5 h, TLC control, 20°C). After evaporation, addition of benzene, filtration through SiO,, evaporation, and chromatography (SiO,, benzene-ether gradient), 1, mp 124.5-125S”C (from ether-hexane), [(r]? -84.4” (c 1.15, CHCI,), was isolated in 71% yield *; v,,, 2162 cm-’ (SCN), 2116 cm-’ (N,); ‘H NMR data: 6 5.19 (dd, 3 H, I,,, 9.5 Hz, H-31, 5.09 (dd, 1 H, J4,5 9.5 Hz, H-4), 4.55 (d, 1 H, J,,, 9.5 Hz, H-l), 4.16-4.30 (m, 2 H, J5,6a 5, &, 2.5, J6a,6b 10 Hz, H-6a,6b), 3.86 (d, 1 H, I,,, 9.5 Hz,

Synthesis of the tetrasaccharide repeating-unit of the O-specific polysaccharide from Salmonella senftenberg

Abstract The oligosaccharide β- d -Man-(1 → 4)-α- l -Rha (1 → 3)- d -Gal-(6 ← 1)-α- d -Glc, which is the repeating unit of the O-specific polysaccharide chain of the lipopolysaccharide from Salmonella senftenberg , was obtained by glycosylation of benzyl 2,4-di- O -benzyl-6- O -(2,3,4-tri- O -benzyl-6- O - p -nitrobenzoyl-α- d -glucopyranosyl)-β- d -galactopyranoside or benzyl 2- O -acetyl-6- O -(2,3,4-tri- O -benzyl-6- O - p -nitrobenzoyl-α- d -glucopyranosyl)-β- d -galactopyranoside with 3- O -acetyl-4- O -(2,3,4,6-tetra- O -acetyl-β- d -mannopyranosyl)-β- l -rhamnopyranose 1,2-(methyl orthoacetate) followed by removal of protecting groups.

Synthesis of polysaccharides with 1,2-cis-glycosidic linkages by tritylthiocyanate polycondensation. Stereoregular α-(1-6)-D-glucan

Abstract The completely stereoregular polysaccharide, α-(1-6)-D-glucan, has been synthesised using a new highly stereospecific type of polycondensation process - trityl-thiocyanate polycondensation.

Structural analysis of oligosaccharides by mass spectrometry: acetates of N-arylglycosylamines

Abstract The electron-impact mass spectra of the acetylated N -arylglycosylamine derivatives of tri-, tetra-, and penta-saccharides allow the determination of molecular weight, the nature and sequence of the monosaccharide residues, and, in certain instances, the position of some of the interglycosidic linkages.

Synthesis of mono- and di-α-l-fucosylated 2-acetamido-2-deoxy-N-glycyl-β-d-glucopyranosylamines, spacered fragments of glycans of N-glycoproteins

Abstractα-l-Fucp-(1→3)-d-GlcNAc, α-l-Fucp-(1→6)-[α-l-Fucp-(1→3)]-d-GlcNAc, and β-d-Galp-(1→3)-[α-l-Fucp-(1→4)]-d-GlcNAc were converted into corresponding β-glycopyranosylamines by action of ammonium carbamate in aqueous boric acid, or in aqueous methanol in case of α-l-Fucp-(1→6)-d-GlcNAc. N-Acylation of these fucooligosaccharides with N-Z-glycine N-hydroxysuccinimide ester (Z is benzyloxycarbonyl) followed by hydrogenolytic removal of Z-group afforded corresponding N-glycyl-β-glycopyranosylamines of these fucooligosaccharides; three of them model carbohydrate-peptide region of N-glycoproteins, and the forth is an amino-spacered Lea-antigen.