摘要:

6-Bromo-6-deoxy-α-d-glucopyranosyl fluoride (2) was prepared in good yield from α-d-glucopyranosyl fluoride (1) by treatment with PPh3and CBr4in pyridine. Catalytic reduction of 2 gave the corresponding 6-deoxy-α-d-glucopyranosyl fluoride (3) while treatment with NaN3in DMF gave the 6-azido-6-deoxy-α-d-glucopyranosyl fluoride (4). The latter could be reduced to the 6-amino-6-deoxyglucosyl fluoride (5) which was converted into the 6-acetamido-6-deoxy-α-d-glucopyranosyl fluoride (6). The C-6 modified glucosyl fluorides 2, 3, 4, and 6 are crystalline compounds.

ISSN:0732-8303    

DOI:10.1080/07328309508006432

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The X-ray crystal structure of 3,3′,4,4′-tetra-O-benzoyl-2,2′,6,6′-tetradeoxy-α,α-ribotrehalose (1) (3,4-di-O-benzoyl-2,6-dideoxy-α-D-ribohexopyranosyl 3,4-di-O-benzoyl-2,6-dideoxy-α-d-ribohexopyranoside) is reported. The molecule possesses crystallographic C2symmetry. The hexopyranosyl residues have a distorted4C1conformation. The X-ray data show that O(3) and O(4) are optimally positioned to function as the Shallenberger AH,B glucophore in the free sugar, yet the free sugar is devoid of sweetness, and is, instead strongly bitter. A stereochemical basis of the biter taste of this compound has been proposed.

ISSN:0732-8303    

DOI:10.1080/07328309508006433

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A series of 2,3-O-cyclopentylidene C-glycoside analogs in which the furanose ring has been replaced with a N-hydroxypyrrolidine have been prepared. A structural study of these tricyclic compounds and the aminoxyl radicals thereof has been carried out using variable temperature1H NMR, X-ray diffraction, molecular dynamics and EPR spectroscopy. Both types of compounds,N-hydroxypyrrolidines and pyrrolidineN-oxyls, fundamentally prefer - in solutions-N-endoconformations over the alternate, N-exoforms found by X-ray diffraction studies and computed to be more stable by molecular dynamics.

ISSN:0732-8303    

DOI:10.1080/07328309508006434

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Convenient oxidation of carbohydrate derived lactols to lactones as well as the oxidation of ε-hydroxy-β-ketophosphonates to their corresponding β, ε-diketophosphonates can be performed with theDess-Martinperiodinane in high yields.

ISSN:0732-8303    

DOI:10.1080/07328309508006435

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A rate law for the oxidation of 2-deoxy-d-glucose (2DG) by Cr(VI) in perchloric acid has been derived. This rate law corresponds to the reaction leading to the formation of 2-deoxy-d-gluconic acid (2DGA). No cleavage to carbon dioxide takes place when a twenty-fold or higher excess of aldose over Cr(VI) is employed. Kinetic constants are interpreted in terms of the absence of an hydroxyl group at C-2 on the stability of the chromic ester formed in the first reaction step. Free radicals formed during the reaction convert Cr(VI) to Cr(V). The latter species was detected by EPR measurements.

ISSN:0732-8303    

DOI:10.1080/07328309508006436

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

L-Ascorbate (0) reacted rapidly with sodium trimetaphosphate (STMP) at 20–25°C and constant pH 9.5–10.0 in the presence of calcium ion. Barium and strontium ions also catalyzed the phosphorylation reaction, but not magnesium ion. The optimum reaction mixture was initially 1.4 M L-ascorbate, 1.8 M STMP, 1.7 M calcium hydroxide, and 0.4 M calcium chloride. Over a 20-min reaction period, pH was maintained by adding approximately 0.1 g calcium hydroxide in a 20% aqueous slurry. The initial and final Ca/P ratios were -0.36 and 0.42, respectively. The reaction products were 98.8% 2-phosphorylated L-ascorbate, 1.2% unreacted0, and a trace of 4,5-ene, probably formed through 5,6-phosphorylated L-ascorbate 2-polyphosphate. High-performance liquid chromatography with UV detection and preparative anion-exchange chromatography showed the presence of eight 2-phosphorylated derivatives of0and two of the 4,5-ene skeleton. Rapid 2-phosphorylation prevented accumulation of the 4, 5-elimination reaction, and three 5,6-cyclophosphoesters of0were found in the reaction products. A Ca/Na (3/1) salt of L-ascorbate 2-polyphosphate was isolated in 88% yield as a white, odorless powder containing 33% of L-ascorbate equivalents. Crystalline cyclohexylainmonium salts of L-ascorbate 2-mono, di, and triphosphates were prepared.

ISSN:0732-8303    

DOI:10.1080/07328309508006437

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The regioselective glycosylations ofN-2-bis(ethoxycarbonyl)vinyl-β-l-rhamno-(1) and fucopyranosylamine (2) with tetra-O-acetyl-α-d-glycopyranosyl bromides were performed. In this way theN-protected disaccharide and trisaccharide β-d-Glcp-(l→3)-β-l-Rhap(3), β-d-Glcp-(1→4)-β-l-Rhap(5), β-d-Galp-(1→3)-β-l-Rhap(7), β-d-Galp-(l→4)-β-l-Rhap(9), β-d-Glcp-(l→3)-β-l-Fucp(11), β-d-Glcp-(l→2)-β-l-Fucp(13), and β-d-Galp-(l→3)-[β-d-Galp-(l→2)]-β-l-Rhap(14) glycosylamines were obtained. The structures of compounds3, 5, 7, 9, 11, 13, and14are supported by the preparation of the corresponding per-O-acetyl derivatives and by spectroscopic (IR, NMR, and MS) data.

ISSN:0732-8303    

DOI:10.1080/07328309508006438

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A series of six disaccharides, α-l-IdoA-(l →4)-α-d-GlcNAc-l→OMe, α-l-IdoA-(l →4)-α-d-GlcNSO3-l →OMe, β-d-GlcA-(l →4)-α-d-GlcNAc-l →OMe, β-d-GlcA-(l→4)-α-d-GlcNSO3-l→OMe, α-d-GlcNAc-(l →4)-β-d-GlcA-l →OMe, β-d-GlcNAc-(l→4)-β-d-GlcA-l→OMe, and two trisaccharide, β-d-GlcA-(1 y4)-α-d-GlcNAc-(1 →4)-β-d-GlcA-l →OMe, α-l-IdoA-(l →4)-α-d-GIcNSO3-(1 →4)-β-d-GlcA-l →OMe was prepared and screened for biological activityin vitro. The oligosaccharides were tested, together with a previously synthesized trisaccharide, α-l-IdoA-(l →4)-α-d-GlcNAc-(l →4)-β-d-GlcA-l →OMe, and three tetrasaccharides, α-l-IdoA-(l →4)-α-d-GlcNAc-(l →4)-β-d-GlcA-(l →3)-β-d-Gal-l →OMe, β-d-GlcA-(l →3)-β-d-Gal-(l →3)-α-d-Gal-(1→3)-2-PO3-β-d-Xyl-l →OMe, β-d-GlcA-(1 →3)-β-d-Gal-(1 →3)-β-d-Gal-(1→3)-β-d-Xyl-l →OMe, for competitive binding to acidic and basic fibroblast growth factor in an assay using125I labelled heparin. It was found that the non-sulphated trisaccharides, α-l-IdoA-(l →4)-α-d-GlcNAc-(l →4)-β-d-GlcA-l →OMe and β-d-GlcA-(l →4)-α-d-GlcNAc-(l →4)-β-d-GlcA-l- →OMe, and two of the disaccharides can bind to acidic as well as basic FGF.

ISSN:0732-8303    

DOI:10.1080/07328309508006439

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Stereocontrolled synthesis of neolacto series ganglioside analogs containing GlcNAcβ1–6Gal substituted for the GlcNAcβ1–3Gal residue in sialyl Lewis X and sialyl neolactotetraosyl ceramide is described. Tri- and tetra- saccharides7and10containing GlcNAcβ1 →6Gal residue were obtained by glycosylation of 2-(trimethylsilyl)ethylO-(2,3-di-O-benzyl-β-d-galactopyranosyl)-(1 →4)-2,3,6-tri-O-benzyl-β-d-glucopyranoside (2) with methyl 3-O-benzyl-4,6-O-benzylidene-2-deoxy-2-phthalimido-l-thio-β-d-glucopyranoside (4) for the synthesis of sialyl paragloboside or methylO-(2,3,4-tri-O-benzyl-α-l-fucopyranosyl)-(l →3)-4,6-O-benzylidene-2-deoxy-2-phthalimido-1-thio-β-d-glucopyranoside (6) for sialyl Lexsynthesis. Compounds7and10were transformedviaremoval of the phthaloyl group followed byN-acetylation,O-acetylation and reductive ring-opening of the benzylidene acetal into the acceptors9and12. Dimethyl (methylthio)sulfonium triflate (DMTST)-promoted coupling of9or12with methylO-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-d-glycero-α-d-galacto-2-nonulopyranosylonate)-(2 →3)-2,4,6-tri-O-benzoyl-l-thio-β-d-galactopyranoside (13) gave the desired pentasaccharide14and hexasaccharide18, respectively, which were convertedviareductive removal of the benzyl groups,O-acetylation, removal of the 2-(trimethylsilyl)ethyl group and treatment with trichloroacetonitrile, into the α-trichloroacetimidates17and21. Condensation of17or21with (2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3-diol (22) gave the β-glycosides23and26, which were transformedviareduction of the azido group, coupling with octadecanoic acid,O-deacylation and saponification of the methyl ester group, into the desired positional isomers of sialyl neolactotetraosyl ceramide25and of sialyl Lexgangliosides28, respectively.

ISSN:0732-8303    

DOI:10.1080/07328309508006440

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The substitution site of partiallyO-methylated glycopyranoses is identified by HBMC. Their1H and13C NMR chemical shifts are evaluated by considering chemical shift increments. The3J(13C,1H) coupling constants are evaluated. Interesting applications of chemical shift increments are illustrated.

ISSN:0732-8303    

DOI:10.1080/07328309508006441

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor