摘要:

Two oligosaccharides β-GlcA-(1→3)-β-Gal and α-GalNAc-(1→4)-β-GlcA-(1→3)-β-Gal related to the glycosaminoglycan linkage region were synthesized. Both oligosaccharides, having a 2-aminoethyl aglycon, were biotinylated and used as immunogens to prepare carbohydrate specific monoclonal antibodies. The biotin-conjugated trisaccharide was able to form a complex with streptavidin which could be used directly for immunization.

ISSN:0732-8303    

DOI:10.1080/07328309908543974

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Branched-chain conjugated dienepyranosides including vinyl phosphate esters were subjected to catalytic hydrogenation under different conditions. Heterogeneous catalysts led to isomerization products that were resistant to further hydrogenation. On the other hand, under homogeneous conditions, complete stereoselective hydrogenation was achieved. Methyl 2,4-dideoxy-3-O-diethoxyphosphoryl-4-C-[(methoxycarbonyl)methyl]-α-D-ribo-hexopyranoside (6b), a potential precursor of thromboxane analogs, was obtained.

ISSN:0732-8303    

DOI:10.1080/07328309908543975

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Intermediate oxocarbenium ions or other intermediates produced during acid catalyzed anomerization of some methyl glycosides were trapped by reduction with 4-methylmorpholine borane. The glycosylium ion intermediate formed on anomerization of methyl 4-O-methyl-α-D-glucopyranoside gave, as expected, only a mixture of the α- and β-D-glucopyranosides, as this reaction is slow compared to the degradation of the reducing agent. The more reactive methyl 2-deoxy-4-O-methyl-α-D-arabino-hexopyranoside gave two reduction products, namely, 1,5-anhydro-2-deoxy-4-O-methyl-D-arabino-hexitol and 2-deoxy-1,4-di-O-methyl-D-arabino-hexitol, indicating alternative reaction pathways, involving eitherexoorendoC-O cleavage. The aldofuranosides, when necessary methylated on O-5 in order to avoid formation of pyranosides, gave 1-O-methylalditols, indicating protonation of the ring oxygen, followed byendoC-O cleavage. The methyl 2-deoxy-5-O-methyl-α-D-arabino-hexofuranosides, however, gave a mixture of the 1,5-di-O-methylalditol and the 5-O-methyl-1,4-anhydroalditol. The methyl fructosides and 1-deoxyfructosides, both furanosidic and pyranosidic, gave mixtures of 2,5- and 2,6- anhydrohexitols, indicating that the anomerization of these glycosides also proceedsvia exoC-O cleavage.

ISSN:0732-8303    

DOI:10.1080/07328309908543976

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Nanofiltration was used in downstream processing for the desalination and concentration of the nucleotide sugars, cytidine-5'-monophospho-β-N-acetylneuraminic acid (CMP-Neu5Ac)1and guanosine-5'-diphospho-α-D-mannose (GDP-Man)2. With appropriate membrances, the retention rate for CMP-Neu5Ac was 0.995 and for GDP-Man 0.983. Both nucleotide sugars were purified on a gram scale with a purity ≥95%.

ISSN:0732-8303    

DOI:10.1080/07328309908543977

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The variable temperature1H NMR spectra of the signals of the C-6 protons of 2-hydroxy-3-methylphenyl β-D-glucopyranoside (9a) and its 2,3,4,6-tetra-O-acetyl derivative (2a) had previously been interpreted as indicating that there was slow rotation around the C5-C6 bond in2aand for9a, that thetgrotamer was significantly populated while thegtrotamer had a negligible population. The data was reanalysed to demonstrate that neither conclusion was valid.

ISSN:0732-8303    

DOI:10.1080/07328309908543978

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

1,6-Anhydro-3-deoxy-4-S-ethyl-4-thio-β-D-erythro-hexopyranos-2-ulose (2) reacted with carbon disulphide and iodomethane to furnish 1,6-anhydro-3-[bis(methylthio)methylene]-3-deoxy-4-S-ethyl-4-thio-β-D-erythro-hexopyranos-2-ulose (3). Treatment of2with dimethylformamide dimethyl acetal yielded 1,6-anhydro-3-deoxy-3-(dimethylaminomethylene)-4-S-ethyl-4-thio-β-D-erythro-hexopyranos-2-ulose (4). The reactions of3with malononitrile and hydrazine hydrate furnished 1,6-anhydro-3-[bis-(methylthio)methylene]-2-(dicyanomethylene)-2,3-dideoxy-4-S-ethyl-4-thio-β-D-erythro-hexopyranose (7) and (1R,7R,8R)-2,3,5,6(2,4,5,6)-tetradehydro-7-ethylthio-5-methylthio-3,4-diaza-10,11-dioxatricyclo[6.2.1.02,6]undecane (8a,b), respectively.

ISSN:0732-8303    

DOI:10.1080/07328309908543979

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The synthesis and NMR characterisation of methyl mono- and di-O-α-L-rhamnopyranosyl-α-D-glucopyranosiduronic acids1-6are described. Two commercial starting products were used: methyl α-D-glucopyranoside7for the preparation of1and2, and methyl (R)-4,6-O-benzylidene-α-D-glucopyranoside8for3-6. Oxidation reaction of the hydroxymethyl group of glucose to a carboxylic acid group was performed by sodium hypochlorite 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-mediated procedure after the coupling reaction. Glycosylation was carried out using the trichloroacetimidate approach with trimethylsilyl trifluoromethanesulfonate (TMSOTf) as promoter, resulting in a completely stereoselective formation of the α glycosyl linkage.

ISSN:0732-8303    

DOI:10.1080/07328309908543980

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Starting from D-galactose and L-fucose, four disaccharides, namely methyl β-L-fucopyranosyl-(1→2)-α-D-galactopyranoside, methyl α-L-fucopyranosyl-(1→2)-α-D-galactopyranoside, methyl α-L-fucopyranosyl-(1→2)-β-D-galactopyranoside and methyl β-L-fucopyranosyl-(1→2)-β-D-galactopyranoside related to the repeating units ofE.coliO126 and O128 have been synthesized using NIS and TfOH as promoter.

ISSN:0732-8303    

DOI:10.1080/07328309908543981

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Cyclodextrins are cyclic oligosaccharides that function as chiral host molecules exhibiting enantioselectivity in reactions with racemic guests1and thus they represent a significant moiety of artificial enzymes.2The most easily obtainable and relatively inexpensive are ß-cyclodextrins (ß-CD), cyclic heptaglucosides in which glucopyranosyl residues are linked by an α(1-4) glycosidic bonds. ß-CD is surprisingly poorly soluble in water (1.8 g in 100 mL)3but the solubility of its derivatives is often significantly better. For instance, ß-CD with all secondary hydroxyls methylated, forms 50% aqueous solutions at room temperature,4and even completely methylated ß-CD is ten times more soluble in water (17 g in 100 mL)5than ß-CD itself. Methylation also alters the binding of the substrates to ß-CD often increasing its specificity and strength,6and renders the hydroxyl groups unreactive. Therefore, it is of interest to prepare derivatives of ß-CD in which the enzyme-mimicking group is bound to one hydroxyl (possibly through a tether) while the rest of the ß-CD moiety is permethylated.

ISSN:0732-8303    

DOI:10.1080/07328309908543982

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Chitin is a linear polysaccharide consisting of [−4) 2-acetamido-2-deoxy-β-D-glucopyranose (1− and −4) 2-amino-2-deoxy β-D-glucopyranose (1-]nwhich occurs widely in nature and which after further de-N-acetylation yields chitosan. Chitin, chitosan and many of their derivatives have found applications in industry, medicine, pharmacology and food technology.1Many recent studies have reported modifications of chitosan in attempts to bestow upon it a variety of properties.2−6

ISSN:0732-8303    

DOI:10.1080/07328309908543983

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor