摘要:

The disaccharide, which corresponds to the terminal fragment of theVibrio choleraeO1 LPS, was prepared starting from the corresponding trichloroacetimidate derivative of the monosaccharide in the presence of trimethylsilyl triflate. After selective reduction of the azido group, the reaction with 2,4-di-O-acetyl-3-deoxy-L-glycero- tetronic acid in the presence of EEDQ afforded the corresponding amides. The cleavage of dioxolane protecting group followed by careful deacetylation and coupling with Bovine Serum Albumin or Meningococcal Outer Membrane Protein in the presence of sodium cyanoborohydride gave the corresponding neoglycoconjugates.

ISSN:0732-8303    

DOI:10.1080/07328309808002355

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Evidence of rearrangement of 3-acyl derivatives of ascorbic acid to 2-acyl derivatives has been found for carbon and phosphorus acyl groups. The observations are consistent with intramolecular rearrangement through a cyclic intermediate in which the acyl group is bonded to both the 2- and 3-oxygen atoms of ascorbic acid. A rate of rearrangement has been measured for the 3-diphenylphosphinate ester. Calculated results indicate an increase in negative atomic charge at O-2 in the 3-acyl esters but a decrease in the charge of O-3 in the 2-acyl esters.

ISSN:0732-8303    

DOI:10.1080/07328309808002356

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The synthesis of 5-glycosyl isoxazoles with 3-alkyl-, 3-aryl, 3,4-dialkyl, 3-aryl-4-alkyl or 3-alkyl-4-bromo substituents is reported. Deoxyenuloses were obtained from reaction of 2,3-O-isopropylidene-D-glyceraldehyde and several phosphorus ylides, which contain a carbonyl group, by a Wittig reaction.C-glycosyl α,β-unsaturated ketones were obtained, with the polyhydroxylate chain lengthened by two or three carbon atoms. In the second phase the ketones were transformed into the correspondingC-glycosyl α,β-unsaturated ketoximes, leading to theC-glycosyl isoxazoles, which were converted into the title compounds via removal of the isopropylidene group of suitably protected carbohydrates. The solubility of the synthetizedC-glycosyl isoxazoles were modified by free hydroxyl groups in such a way that their behaviour against certain viruses and their potential antiviral activity could be studied.

ISSN:0732-8303    

DOI:10.1080/07328309808002357

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

4-O-(2-Acetamido-2-deoxy-β-D-glucopyranosyl)-2-acetamido-2-deoxy-D-mannopyranose (2) was prepared from diacetylchitobiose (1) by Lobry de Bruyn-Alberda van Ekenstein rearrangement under catalysis of Ca(OH)2. The disaccharide2shows about ten times higher affinity than1towards NKR-P1 protein acting as a crucial activating receptor of rat natural killer cells (leukocytes). Chitotriose (3) can be epimerized analogously to give GlcNAcβ1-4GlcNAcβ1-4ManNAc (4) and its binding properties to NKR-P1 are also about ten times higher than those of3.

ISSN:0732-8303    

DOI:10.1080/07328309808002358

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A one-step synthesis for cyclodextrin methacrylate monomers was examined starting from α-, β- and γ-cyclodextrin. The reaction of 2-isocyanatoethyl methacrylate as well as allylisocyanate with the corresponding cyclodextrin gave the monofunctionalized carbamate-linked cyclodextrin methacrylates2, 6and9and allylcarbamates11and14in moderate yields. By NMR spectroscopic means, it could be proven that in all cases only the primary 6-hydroxyl groups of the cyclodextrins reacted with the isocyanate group. For the synthesis of a β-cyclodextrin monoallyl compound, a substitution reaction of purchasable 6-O-monotoluenesulfonyl-β-cyclodextrin with allylamine gave 6-N-allylamino-6-deoxy-β-cyclodextrin18in high yield. The reaction of 2-isocyanatoethyl methacrylate with α-cyclodextrin to the 6-O-carbamoyl-2-methylpropenoylethyl-α-cyclodextrin(2)was optimized so that the monomer2could be prepared on a larger scale without chromatographic separation. The aqueous radical homopolymerization of2with the peroxodisulfate/bisulfite redox initiator gave the water soluble cyclodextrin polymer19in good yield. Its molecular weight was determined by gel permeation chromatography to beMn= 101,800 corresponding to an average degree of polymerizationPn= 90.

ISSN:0732-8303    

DOI:10.1080/07328309808002359

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Iodoacetoxylation of 3,4,6-tri-O-acetyl-1,5-anhydro-2-deoxy-D-arabino-hex-1-enitol (tri-O-acetyl-D-glucal) (1) and 3,4-di-O-acetyl-1,5-anhydro-2,6-dideoxy-L-arabino-hex-1-enitol (di-O-acetyl-L-rhamnal) (3) gave the α-1,2-trans-1-O-acetyl-2-deoxy-2-iodo adducts with high stereoselectivities and good yields, in accordance with the results reported on 3,6-di-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-1,5-an-hydro-2-deoxy-D-arabino-hex-1-enitol (hexa-O-acetyl lactal) (2). The α-1,2-transadducts were reacted with an excess of alcohol in the presence of trimethylsilyl trifluoromethane-sulfonate affording the corresponding α-1,2-trans-2-deoxy-2-iodo-glycopyranosides in good yields. The octyl 2-deoxy-2-iodo-α-D-glycosides10and11prepared in two steps from the glycals1and2were deiodinated and deacetylated, giving28and29, and the physicochemical-properties (cmc) of29are reported.

ISSN:0732-8303    

DOI:10.1080/07328309808002360

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

4-Substituted-butenolides treated with free hydroxylamine at pH=5 undergo conjugate addition - rearrangement to afford isoxazolidin-5-ones. This is in contrast to N-substituted hydroxylamines which under the same conditions produce Michael adducts only. In the presence of base, butenolides undergo racemizationviaflat tautomeric forms.

ISSN:0732-8303    

DOI:10.1080/07328309808002361

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The conformational maps of eight derivatives of the disaccharide α-D-Galp-(1→3)-β-D-Galpsulfated in different positions were obtained using the MM3 force-field specially parameterized for sulfate ester groups. As occurred with MM2, the conformational flexibility of the glycosidic linkage is only slightly hindered by sulfation. A substantial effect of sulfation of the β-D-galactose unit on position 4 shifts the global minimum to positive ΨH(C1′-O3-C3-H3) angles, while sulfation at position 2 of the same unit deepens the well at negative ΨHangles. On the other hand, sulfation on the α-D-galactose unit has a lesser effect, which in any case tends to stabilize the minimum at negative ΨHangles.

ISSN:0732-8303    

DOI:10.1080/07328309808002362

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Structural investigations have shown that lipid A constitutes the active principle of lipopoly saccharide (LPS, endotoxin), a complex amphipathic molecule located on the cell surface of Gram-negative bacteria.1Lipid A elicits not only the typical endotoxic reactions such as fever and lethal shock but also adjuvant, antitumor and other beneficial effects.1As a result, there has been a great deal of interest in the synthesis of lipid A derivatives possessing low toxicity.1,2

ISSN:0732-8303    

DOI:10.1080/07328309808002363

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor