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Carbohydrate Derivatives (carbohydrate + derivative)
Selected AbstractsHydrogen-Bonding Cooperativity: Using an Intramolecular Hydrogen Bond To Design a Carbohydrate Derivative with a Cooperative Hydrogen-Bond Donor CentreCHEMISTRY - A EUROPEAN JOURNAL, Issue 17 2004Virginie Vicente Dr. Abstract Neighbouring groups can be strategically located to polarise HO,,,OH intramolecular hydrogen bonds in an intended direction. A group with a unique hydrogen-bond donor or acceptor character, located at hydrogen-bonding distance to a particular OH group, has been used to initiate the hydrogen-bond network and to polarise a HO,,,OH hydrogen bond in a predicted direction. This enhanced the donor character of a particular OH group and made it a cooperative hydrogen-bond centre. We have proved that a five-membered-ring intramolecular hydrogen bond established between an amide NH group and a hydroxy group (1,2-e,a), which is additionally located in a 1,3 -cis- diaxial relationship to a second hydroxy group, can be used to select a unique direction on the six-membered-ring intramolecular hydrogen bond between the two axial OH groups, so that one of them behaves as an efficient cooperative donor. Talose derivative 3 was designed and synthesised to prove this hydrogen-bonding network by NMR spectroscopy, and the mannopyranoside derivatives 1 and 2 were used as models to demonstrate the presence in solution of the 1,2-(e,a)/five-membered-ring intramolecular hydrogen bond. Once a well-defined hydrogen-bond is formed between the OH and the amido groups of a pyranose ring, these hydrogen-bonding groups no longer act as independent hydrogen-bonding centres, but as hydrogen-bonding arrays. This introduces a new perspective on the properties of carbohydrate OH groups and it is important for the de novo design of molecular recognition processes, at least in nonpolar media. Carbohydrates 1,3 have shown to be efficient phosphate binders in nonpolar solvents owing to the presence of cooperative hydroxy centres in the molecule. [source] Lectin-Based Drug Design: Combined Strategy to Identify Lead Compounds using STD NMR Spectroscopy, Solid-Phase Assays and Cell Binding for a Plant Toxin ModelCHEMMEDCHEM, Issue 3 2010Abstract The growing awareness of the sugar code,i.e. the biological functionality of glycans,is leading to increased interest in lectins as drug targets. The aim of this study was to establish a strategic combination of screening procedures with increased biorelevance. As a model, we used a potent plant toxin (viscumin) and lactosides synthetically modified at the C6/C6, positions and the reducing end aglycan. Changes in the saturation transfer difference (STD) in NMR spectroscopy, applied in inhibition assays, yielded evidence for ligand activity and affinity differences. Inhibitory potency was confirmed by the blocking of lectin binding to a glycoprotein-bearing matrix. In cell-based assays, iodo/azido-substituted lactose derivatives were comparatively active. Interestingly, cell-type dependence was observed, indicating the potential of synthetic carbohydrate derivative to interact with lectins in a cell-type (glycan profile)-specific manner. These results are relevent to research into human lectins, glycosciences, and beyond. [source] Stereodivergent Syntheses of Highly Substituted Enantiopure 4-Alkoxy-3,6-dihydro-2H -1,2-oxazines by Addition of Lithiated Alkoxyallenes to Carbohydrate-Derived AldonitronesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2005Matthias Helms Abstract Additions of lithiated alkoxyallenes to D -glyceraldehyde-based nitrones 1 and 2 did not provide the expected hydroxylamine derivatives. Instead, a novel [3+3] cyclization process furnished 4-alkoxy-3,6-dihydro-2H -1,2-oxazines 9,14 with excellent syn selectivities and in moderate to good yields. Through precomplexation of the nitrones the corresponding anti -configured 1,2-oxazines 9, 10 and 13 could be obtained with high stereoselectivity. The reactions of nitrones 3,6, derived from D -erythrose or D -threose, generally proceeded less diastereoselectively, but reasonable yields of anti -configured 1,2-oxazines such as anti - 17 and anti - 19 could be obtained under Lewis acid promotion conditions. This was also the case for reactions of the D -arabinose-derived nitrone 7, which provided the anti -1,2-oxazines 23 and 24 with excellent diastereoselectivity and in good yields. Bis-nitrone 8 and lithiated methoxyallene furnished a mixture of six compounds, among which the major componentwas the C2 -symmetric syn/syn -1,2-oxazine 29. The diastereoselectivities of these reactions are interpreted on the basis of Dondoni's model for reactions between organolithium compounds and nitrones. The mechanisms for formation of 1,2-oxazines and of side products are discussed. The method introduced here seems to be of broad applicability and an excellent tool for diastereoselective chain elongation of carbohydrate derivatives, affording stereodefined precursors of aminopolyols and other highly functionalized compounds. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Synthesis of Polyfluorinated Nitrogen-Containing Heterocycles from Hemifluorinated Enones or Organofluorosilicon Building Blocks as Synthetic EquivalentsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2004Frédéric Chanteau Abstract A series of polyfluorinated heterocycles has been prepared by heterocyclisation of hemifluorinated enones or organofluorosilicon synthetic equivalents with different bis(nucleophiles). These polyfluorinated building blocks were obtained by treatment of acylsilanes with perfluoro organometallic reagents. The method is general and has been applied to aliphatic, aromatic and carbohydrate derivatives, to give oxazolidines, imidazolidines, benzodia- and -thiazepines, quinolines and pyrimidines bearing both a fluorine atom and a perfluoroalkyl group in vicinal positions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Recent advances in the chemistry of parainfluenza-1 (Sendai) virus inhibitorsMEDICINAL RESEARCH REVIEWS, Issue 4 2003Raffaele Saladino Abstract Purine and pyrimidine derivatives, antioxidants, fusion inhibitors, statins, prostaglandins, antibiotic nucleosides, inhibitors of Ca2+ homeostasis, carbohydrate derivatives, antisense polynucleotides and chimeras, are described as inhibitors of parainfluenza-1 (Sendai) viral infections. © 2003 Wiley Periodicals, Inc. Med Res Rev, 23, No. 4, 427,455, 2003 [source] The nucleotidase/phosphatase SAL1 is a negative regulator of drought tolerance in ArabidopsisTHE PLANT JOURNAL, Issue 2 2009Pip B. Wilson Summary An Arabidopsis thaliana drought-tolerant mutant, altered expression of APX2 (alx8), has constitutively increased abscisic acid (ABA) content, increased expression of genes responsive to high light stress and is reported to be drought tolerant. We have identified alx8 as a mutation in SAL1, an enzyme that can dephosphorylate dinucleotide phosphates or inositol phosphates. Previously identified mutations in SAL1, including fiery (fry1-1), were reported as being more sensitive to drought imposed by detachment of rosettes. Here we demonstrate that alx8, fry1-1 and a T-DNA insertional knockout allele all have markedly increased resistance to drought when water is withheld from soil-grown intact plants. Microarray analysis revealed constitutively altered expression of more than 1800 genes in both alx8 and fry1-1. The up-regulated genes included some characterized stress response genes, but few are inducible by ABA. Metabolomic analysis revealed that both mutants exhibit a similar, dramatic reprogramming of metabolism, including increased levels of the polyamine putrescine implicated in stress tolerance, and the accumulation of a number of unknown, potential osmoprotectant carbohydrate derivatives. Under well-watered conditions, there was no substantial difference between alx8 and Col-0 in biomass at maturity; plant water use efficiency (WUE) as measured by carbon isotope discrimination; or stomatal index, morphology or aperture. Thus, SAL1 acts as a negative regulator of predominantly ABA-independent and also ABA-dependent stress response pathways, such that its inactivation results in altered osmoprotectants, higher leaf relative water content and maintenance of viable tissues during prolonged water stress. [source] Synthesis of Benzaldehyde-Functionalized Glycans: A Novel Approach Towards Glyco-SAMs as a Tool for Surface Plasmon Resonance StudiesCHEMISTRY - A EUROPEAN JOURNAL, Issue 23 2010Sebastian Kopitzki Dipl.-Chem. Abstract In recent years the interest in tools for investigating carbohydrate,protein (CPI) and carbohydrate-carbohydrate interactions (CCI) has increased significantly. For the investigation of CPI and CCI, several techniques employing different linking methods are available. Surface plasmon resonance (SPR) imaging is a most appropriate tool for analyzing the formation of self-assembled monolayers (SAM) of carbohydrate derivatives, which can mimic the glycocalyx. In contrast to the SPR imaging methods used previously to analyze CPI and CCI, the novel approach reported herein allows a facile and rapid synthesis of linker spacers and carbohydrate derivatives and enhances the binding event by controlling the amount and orientation of ligand. For immobilization on biorepulsive amino-functionalized SPR chips by reductive amination, diverse aldehyde-functionalized glycan structures (glucose, galactose, mannose, glucosamine, cellobiose, lactose, and lactosamine) have been synthesized in several facile steps that include olefin metathesis. Effective immobilization and the first binding studies are presented for the lectin concanavalin A. [source] | ||||||||||