1,721,002 research outputs found
A novel stereoselective synthesis of N-acetyl-α-neuraminosyl-galactose di-saccharide derivatives, using anomeric S-glycosyl xanthates
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SYNTHESIS OF SIALYLATED BRANCHED TRISACCHARIDE AND TETRASACCHARIDE DERIVATIVES WITH THE SEQUENCE OF THE CAD BLOOD-GROUP DETERMINANT
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N-p-methoxybenzylidene derivatives of 2-amino-2-deoxy-d-glucose as glycosyl donors: a reinvestigation
No full text6-O-Acetyl-3,4-di-O-benzyl-2-deoxy-2-p-methoxybenzylideneamino-d-glucopy ranosyl chloride, 3,4,6-tri-O-acetyl-2-deoxy-2-p-methoxybenzylideneamino-α-d-glucopy ranosyl bromide, 3,4,6-tri-O-acetyl-2-deoxy-2-p-methoxybenzylideneamino-α- and -β-d-glucopyranosyl trichloroacetimidate, and 3,4,6-tri-O-acetyl-2-deoxy-2-p-nitrobenzylideneamino-α-d-glucopyra nosyl bromide have been synthesised, and their behaviour as glycosylation agents with various soluble promoters has been investigated. The results obtained question the accepted non-participating character of the N-p-methoxybenzylideneamino group. © 1990
Stereoselective synthesis of 2-thioglycosides of N-acetylneuraminic acid
No full textTreatment of methyl 5-acetamido-2,4,7,8,9-penta-O-acetyl-3,5-dideoxy-β-d-glycero-d-gala cto-2-nonulopyranosonate (1) severally with thiophenol, phenylmethanethiol, and ethanethiol in the presence of boron trifluoride etherate gave the corresponding 2-thio-β-glycosides 3-5. Treatment of methyl (5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-β-d-glycero- d-galacto-2-nonulopyranosyl chloride)onate (2) severally with thiophenol in the presence of N,N-di-isopropylethylamine, O-ethyl S-potassium dithiocarbonate, and O-ethyl S-potassium thiocarbonate gave the corresponding 2-thio-α-glycosides 7, 10, and 11, of which 10 was converted into the ethyl 2-thio-α-glycoside 9 on heating with N,N-dimethylformamide-sodium iodide. The phenyl 2-thioglycosides 3 and 7 were converted into the corresponding sulfones. © 1989
CONVENIENT SYNTHESES OF SUBSTITUTED PYRANOID GLYCALS FROM THIOPHENYL GLYCOSIDES AND GLYCOSYL PHENYLSULFONES
No full textA series of substituted thiophenyl glycosides and glycosyl phenylsulfones were converted in high yield into glycals after reductive lithiation with lithium naphthalenide, followed by elimination of the substituent at C-2. © 1981
SYNTHESIS OF TRISACCHARIDE DERIVATIVES WITH THE SEQUENCE OF THE DESIALYLATED CAD BLOOD-GROUP DETERMINANT
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GLYCOSYLATION USING A ONE-ELECTRON-TRANSFER HOMOGENEOUS REAGENT - A NOVEL AND EFFICIENT SYNTHESIS OF BETA-LINKED DISACCHARIDES
No full textVariously substituted S-glycosides react in acetonitrile with the primary or secondary hydroxy group of O-glycosides in the presence of tris (4-bromophenyl)ammoniumyl hexachloroantimonate, a stable and commerically available radical cation, to give the corresponding β-O-linked disaccharides in high yield
CHEMICAL SYNTHESIS OF THE DESIALYLATED HUMAN CAD-ANTIGENIC DETERMINANT
No full textBenzyl 2-azido-2-deoxy-β-d-galactopyranoside was converted into benzyl 2-azido-4,6-O-benzyl-2-deoxy-β-d-galactopyranoside via benzylidenation, p-methoxybenzylation, acid hydrolysis, benzylation, and selective oxidation. Condensation of 1,2,3,4,6-penta-O-acetyl-β-d-galactopyranose with benzyl 2-azido-4,6-di-O-benzyl-2-deoxy- β-d-galactopyranoside in the presence of trimethylsilyl triflate gave crystalline benzyl 2-azido-4,6-di-O-benzyl-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-β-d-gal actopyranosyl)-β-d-galactopyranoside (76%), which was converted into benzyl 2-azido-4,6-di-O-benzyl-2-deoxy-3-O-(2,6-di-O-benzyl-β-d-galactopyr anosyl)-β-d-galactopyranoside and condensed with 3,4,6-tri-O-acetyl-2-azido-2-deoxy-α-d-galactopyranosyl bromide in the presence of silver silicate on alumina and molecular sieve 4 Å to give 61% of benzyl O-(3,4,6-tri-O-acetyl-2-azido-2-deoxy-β-d-galactopyranosyl)- (1→4)-O-(2,6-di-O-benzyl-β-d-galactopyranosyl)-(1→3)-2- azido-4,6-di-O-benzyl-2-deoxy-β-d-galactopyranoside. Reduction with sodium borohydride followed by N-acetylation, O-deacetylation, and catalytic hydrogenolysis then gave O-(2-acetamido-2-deoxy-β-d-galactopyranosyl)-(1→4)-O-β-d- galactopyranosyl-(1→3)-2-acetamido-2-deoxy-d-galactopyranose, the desialylated human Cad-antigenic determinant
Preparation of pyranoid glycal derivatives from phenyl thioglycosides and glycosyl phenyl sulphones
No full textPhenyl thioglycopyranosides with various protecting groups (acetal, ether, ester) underwent reductive lithiation at C-1, followed by rapid elimination of the 2-substituent, when treated with lithium naphthalenide in tetrahydrofuran at low temperature. Thus, pyranoid glycal derivatives with acid-labile protecting groups were obtained in excellent yields. Glycopyranosyl phenyl sulphones were prepared quantitatively by oxidation of the corresponding phenyl thioglycosides with catalytic amounts of ruthenium trichloride in the presence of sodium periodate in a biphasic solvent system. These compounds also gave rise to pyranoid glycal derivatives in excellent yields when treated with lithium naphthalenide in tetrahydrofuran at low temperature. A β-linked 2′-deoxydisaccharide glycal derivative was also prepared from the corresponding disaccharide phenyl thioglycoside. Phenyl thioglycopyranosides carrying a 2-xanthate group underwent a radical reductive elimination when treated with tributyltin hydride, to afford glycal derivatives in good yields under neutral conditions. © 1989
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