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Carbohydrate Research

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https://www.readbyqxmd.com/read/29145075/isolation-and-characterisation-of-an-unexpected-byproduct-in-the-regioselective-butane-diacetal-protection-of-%C3%AE-methyl-galactopyranoside
#1
Clément Q Fontenelle, Ramakrishna Kuppala, Mark Light, Bruno Linclau
The regioselective protection of both methyl galactopyranoside anomers at the 2 and 3-positions as the butane diacetal (BDA) is well known. Here we describe the formation of an unexpected byproduct, which mainly occurs when α-methyl galactopyranoside is reacted with 2,3-butanedione under BF3•OEt2 catalysis. The structure of the byproduct, which did not arise from anomerisation to the β-anomer or from BDA formation at the galactopyranoside 3,4-positions, was elucidated by NMR and X-ray crystallographic analysis, and proved to be the expected BDA protected galactopyranoside, but in which the stereochemistry of both its BDA acetal centres are inverted...
November 6, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/29128704/tandem-mass-spectrometry-of-fucoidan-derived-fragments-labeled-with-heavy-oxygen
#2
Stanislav D Anastyuk, Natalia M Shevchenko, Kristina V Belokozova, Pavel S Dmitrenok
A procedure for the partial depolymerization of sulfated fucans and selective labeling with (18)O was developed. A tandem electrospray ionization mass spectrometry (ESI MS/MS) was applied for the direct analysis of mixtures of structurally-different oligosaccharides, derived from the fucoidans of known structure. The presence of label allowed unambiguous distinguishing between the fragment ions of (0,2)X0-type at m/z 287 and (2,4)A-type at m/z 285, since (18)O at the reducing end gave +2 mass shifting. Thus, ESI MS/MS was able to detect (1,2)-type of linkage in disaccharides from the fucoidan of brown alga S...
November 4, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/29107815/synthesis-of-p-1-11-phenoxyundecyl-p-2-2-acetamido-2-deoxy-3-o-%C3%AE-d-rhamnopyranosyl-%C3%AE-d-glucopyranosyl-diphosphate-and-p-1-11-phenoxyundecyl-p-2-2-acetamido-2-deoxy-3-o-%C3%AE-d-galactopyranosyl-%C3%AE-d-galactopyranosyl-diphosphate-for-the-investigation-of-biosynthesis
#3
Vladimir Torgov, Leonid Danilov, Natalia Utkina, Vladimir Veselovsky, Inka Brockhausen
Two new phenoxyundecyl diphosphate sugars were synthesized for the first time: P(1)-(11-phenoxyundecyl)-P(2)- (2-acetamido-2-deoxy-3-O-α-D-rhamnopyranosyl-α-D-glucopyranosyl) diphosphate and P(1)-(11-phenoxyundecyl)-P(2)-(2-acetamido-2-deoxy-3-O-β-D-galactopyranosyl-α-D-galactopyranosyl) diphosphate to study the third step of biosynthesis of the repeating units of O-antigenic polysaccharides in Pseudomonas aeruginosa and E.coli O104 respectively.
November 3, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/29107814/synthesis-of-substrate-analogues-as-potential-inhibitors-for-mycobacterium-tuberculosis-enzyme-mshc
#4
Krishnakant Patel, Fengling Song, Peter R Andreana
Mycothiol cysteine ligase (MshC) is a key enzyme in the mycothiol (MSH) biosynthesis and a promising target for developing new anti-mycobacterial compounds. Herein, we report on the synthesis of substrate analogues, as potential inhibitors, for the MshC enzyme. The target molecules were synthesized employing a Schmidt glycosylation strategy using an enantiomerically pure inositol acceptor and 2-deoxy trichloroacetimidate glycosyl donors with glycosylation yields greater than 70% and overall yields >5%. The inositol acceptor was obtained via chiral resolution of (±)-myo-inositol...
November 3, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/29127846/supramolecular-glycorhodamine-polymer-dot-ensembles-for-the-homogeneous-fluorogenic-analysis-of-lectins
#5
Chang-Zheng Wang, Xiao-Peng He
We have developed a new series of glycoprobe-polymer dot ensembles for the fluorogenic, homogeneous detection of lectins. Electrostatic self-assembly between positively charged rhodamine-based glycosides and negatively charged poly(3-hexylthiophene-2,5-diyl)/poly(styrene-co-maleic anhydride) polymer dots produces the ensembles with a quenched fluorescence. Fluorescence spectroscopy showed that the ensembles exhibited a concentration-dependent fluorescence enhancement with selective lectins over a range of unselective lectins and proteins...
November 1, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/29127847/effect-of-sucralose-on-the-enzyme-kinetics-of-invertase-using-real-time-nmr-spectroscopy-and-progress-curve-analysis
#6
Cheenou Her, Jaideep Singh, V V Krishnan
Sucralose, a derivative of sucrose, is widely used in noncaloric artificial sweeteners (NAS). Contrary to the belief that sucralose is physiologically inert and a healthy alternative sweetener to natural sugar, emerging studies indicate that sucralose alters the host metabolism as well as the composition of the microbiome. In this manuscript, we use real-time nuclear magnetic resonance (NMR) spectroscopy to demonstrate that sucralose alters the enzymatic conversion of sucrose to glucose and fructose. The real-time NMR progress curve analysis suggests that sucralose has the characteristic of a competitive inhibitor on the kinetics of the enzymatic process...
October 31, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/29121497/mannosylcalix-n-arenes-as-multivalent-ligands-for-dc-sign
#7
Ilaria Morbioli, Vanessa Porkolab, Andrea Magini, Alessandro Casnati, Franck Fieschi, Francesco Sansone
DC-SIGN is a receptor protruded from the membrane of immature dendritic cells (DCs) that participates in the activation of the immune response through the recognition of pathogen-associated molecular patterns (PAMPs). On the other hand, HIV exploits the interaction between high-mannose structures of its envelope glycoprotein gp120 and DC-SIGN to be transported towards and infect T-cells. DC-SIGN is involved in the recognition process in the form of a tetramer and the multiple exposition of carbohydrate recognition sites (CRSs) is amplified by the formation on the DCs membrane of patches of tetramers...
October 31, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/29102716/overview-on-the-antiviral-activities-and-mechanisms-of-marine-polysaccharides-from-seaweeds
#8
Qimin Shi, Anjian Wang, Zhonghua Lu, Chunjun Qin, Jing Hu, Jian Yin
Marine polysaccharides are attracting increasing attention in medical and pharmaceutical development because of their important biological properties. The seaweed polysaccharides have now become a rich resource of potential antiviral drugs due to their antiviral activities against various viruses. The structural diversity and complexity of marine polysaccharides and their derivatives contribute to their antiviral activities in different phases of many different viral infection processes. This review mainly introduces the different types of seaweed polysaccharides and their derivatives with potent antiviral activities...
October 31, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/29121496/properties-of-two-fungal-endo-%C3%AE-1-3-galactanases-and-their-synergistic-action-with-an-exo-%C3%AE-1-3-galactanase-in-degrading-arabinogalactan-proteins
#9
Yoshihisa Yoshimi, Kaori Yaguchi, Satoshi Kaneko, Yoichi Tsumuraya, Toshihisa Kotake
Arabinogalactan-proteins (AGPs) are plant proteoglycans, which are widely encountered in the plant kingdom, usually localized on the cell surface. The carbohydrate moieties of AGPs consist of β-1,3-galactan main chains and β-1,6-galactan side chains, to which other auxiliary sugars are attached. To date, FvEn3GAL isolated from Flammulina velutipes is the sole β-1,3-galactanase acting on β-1,3-galactan in an endo-manner. Here we cloned two homologous genes, designated Af3G and NcEn3GAL, possibly encoding endo-β-1,3-galactanase from Aspergillus flavus and Neurospora crassa, respectively...
October 25, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/29128696/concise-synthesis-of-2-7-anhydrosialic-acid-derivatives-and-its-application
#10
Kesatebrhan Haile Asressu, Cheng-Chung Wang
In N-acetylneuraminic acid, apart from O9 and O8, a possible glycosylation site is the O4 position. For example, gangliosides HLG-2 and HPG-7 are considered to be potential lead compounds for carbohydrate-based drug development to treat neural disorders. However, the construction of their α(1 → 4) fucosyl sialic acid and α(2 → 4) linkages between sialic acids is difficult because of the regioselectivity problem. Herein, N-acetyl-2,7-anhydroneuraminic acid was synthesized in three steps from Neu5Ac methyl ester through per-O-trimethylsilylation, heating-assisted intramolecular anomeric protection (iMAP) and desilylation...
October 19, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/28968549/preparation-of-new-%C3%AE-d-xyloside-and-%C3%AE-d-xylobioside-based-ionic-liquids-through-chemical-and-or-enzymatic-reactions
#11
S Gatard, R Plantier-Royon, C Rémond, M Muzard, C Kowandy, S Bouquillon
Several tetraalkylphosphonium and tetraalkylammonium salts containing xyloside- and xylobioside-based anionic moieties have been prepared. Two stereoselective routes have been developed: i) a chemical pathway in four steps from D-xylose, and ii) a chemoenzymatic pathway directly from biomass-derived xylans. These salts displayed interesting properties as ionic liquids. Their structures have been correlated to their thermal properties (melting, glass transition and decomposition temperatures).
September 23, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/28965067/the-convergent-synthesis-and-anticancer-activity-of-broussonetinines-related-analogues
#12
Dominika Jacková, Miroslava Martinková, Jozef Gonda, Kvetoslava Stanková, Martina Bago Pilátová, Peter Herich, Jozef Kožíšek
The convergent synthesis of broussonetinines related congeners 3 and 4 with the simple C13 alkyl side chain and differently configured pyrrolidine skeleton has been achieved. Our approach relied on the [3,3]-sigmatropic rearrangements of chiral allylic substrates derived from d-xylose. Cross metathesis of the common oxazolidinone intermediates 7 and 8 with tridec-1-ene followed by alkylative cyclization completed the construction of both C-alkyl iminosugars. The targeted compounds 3 and 4 were screened for antiproliferative/cytotoxic activities against multiple cancer cell lines by MTT assay...
September 19, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/28950209/limitations-in-the-description-of-conformational-preferences-of-c-disaccharides-the-1%C3%A2-%C3%A2-%C3%A2-3-c-mannobiose-case
#13
Ivan Raich, Zuzana Lövyová, Ladislav Trnka, Kamil Parkan, Jiří Kessler, Radek Pohl, Jakub Kaminský
Conformational preferences of two C-glycosyl analogues of Manp-(1 → 3)-Manp, were studied using a combined method of theoretical and experimental chemistry. Molecular dynamics was utilized to provide conformational behavior along C-glycosidic bonds of methyl 3-deoxy-3-C-[(α-d-mannopyranosyl)methyl]-α-d- and l-mannopyranosides. The OPLS2005 and Glycam06 force fields were used. Simulations were performed with explicit water (TIP3P) and methanol. Results were compared with a complete conformational scan at the MM4 level with the dielectric constant corresponding to methanol...
September 18, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/28987928/synthesis-and-gelation-property-of-a-series-of-disaccharide-triazole-derivatives
#14
Ifeanyi S Okafor, Guijun Wang
Low molecular weight gelators are important for the study of supramolecular chemistry and have useful applications for biomaterials. Glycomimetics that are easily accessible and have useful gelation properties are especially interesting molecules. In this research, nine per-O-acetyl lactosyl- and thirteen per-O-acetyl maltosyl triazole derivatives were synthesized and analyzed. Most of the maltosyl triazoles and one of the lactosyl derivatives were found to be effective molecular gelators. The supramolecular gels were characterized using rheology and optical microscopy and they exhibited morphologies ranging from fibers to planar sheets...
September 15, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/28941406/theoretical-study-on-the-anomeric-effect-in-%C3%AE-substituted-tetrahydropyrans-and-piperidines
#15
Francisco A Martins, Josué M Silla, Matheus P Freitas
Conformational effects, including some controversial examples, have been reported in this work for 2-substituted tetrahydropyrans and piperidines, and for the respective protonated compounds [substituent = F, OH, OCH3, NH2, NHCH3 and N(CH3)2]. Hyperconjugation plays a major role in most cases, either due to endo or exo-anomeric interactions, especially when nitrogen is the electron donor to an antiperiplanar σ* orbital. This interaction also seems to contribute for the Perlin and reverse fluorine Perlin-like effects, which are related to the relative magnitude of (1)JC,H and (1)JC,F coupling constants, respectively, in axial and equatorial conformers...
September 15, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/28942028/novel-teichulosonic-acid-and-glycosyl-1-phosphate-polymers-from-the-cell-walls-of-arthrobacter-sp-strains-vkm-ac-2549-and-vkm-ac-2550-phylogenetically-close-to-arthrobacter-crystallopoietes
#16
Natalia V Potekhina, Nikolay P Arbatsky, Alexander S Shashkov, Andrey S Dmitrenok, Sofya N Senchenkova, Lubov V Dorofeeva, Lyudmila I Evtushenko
Novel teichulosonic acid with the repeating unit →6)-β-D-GlcpNAc-(1→8)-α-Kdn-(2→ has been found in the cell walls of two Arthrobacter strains, VKM Ac-2549 and VKM Ac-2550. The teichulosonic acid was revealed in representatives of the genus Arthrobacter for the first time. Two other polymers identified in the above strains were poly(monoglycosyl 1-phosphate) and poly(diglycosyl 1-phosphate) of hitherto unknown structures, i.e., -6)-α-D-GalpNAc-(1-P-, and -6)-β-D-GlcpNAc-(1→3)-α-D-Galp-(1-P-. The structures of all three polymers were established by using chemical, NMR spectroscopic and ESI-MS methods...
September 14, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/28934626/stereoselective-sialylation-with-o-trifluoroacetylated-thiosialosides-hydrogen-bonding-involved
#17
Nikita M Podvalnyy, Nelly N Malysheva, Maria V Panova, Alexander I Zinin, Alexander O Chizhov, Anna V Orlova, Leonid O Kononov
A series of novel sialyl donors containing O-trifluoroacetyl (TFA) groups at various positions was synthesized. The choice of protecting groups in sialyl donors was based on hypothesis that variations in ability of different acyl groups to act as hydrogen bond acceptors would influence the supramolecular structure of reaction mixture (solution structure), hence the outcome of sialylation. These glycosyl donors were examined in the model glycosylation of the primary hydroxyl group of 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose in comparison with sialyl donors without O-TFA groups...
September 8, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/28917967/synthesis-of-a-trisaccharide-repeating-unit-of-the-o-antigen-from-burkholderia-cenocepacia-and-its-dimer
#18
Ningning Bi, Chenghe Xiong, Guoxia Jin, Zhongwu Guo, Guofeng Gu
The trisaccharide repeating unit of an O-antigen derived from Burkholderia cenocepacia and its dimer, i.e., α-L-Rhap-(1 → 3)-α-D-GalpNAc-(1 → 3)-β-D-GalpNAc-O(CH2)3N3 (1) and α-L-Rhap-(1 → 3)-α-D-GalpNAc-(1 → 3)-β-D-GalpNAc-(1 → 4)-α-L-Rhap-(1 → 3)-α-D-GalpNAc-(1 → 3)-β-D-GalpNAc-O(CH2)3N3 (2), respectively, were synthesized via a highly convergent strategy. Glycosylation of galactosaminyl acceptor 4 with galactosaminyl trichloroacetimidate donor 5 was followed by condensation of resulting disaccharide acceptor 12 with rhamnosyl imidate donor 6 to furnish stereoselectively trisaccharyl thioglycoside 3, which was used as a key and common glycosyl donor for the construction of both 1 and 2...
September 8, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/28923409/recent-advances-in-the-chemical-synthesis-of-sugar-nucleotides
#19
Sanaz Ahmadipour, Gavin J Miller
No abstract text is available yet for this article.
September 1, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/28881237/synthesis-of-a-series-of-new-glycoclusters-and-the-evaluation-of-their-anti-adhesion-activities
#20
Xiaorong Zhang, Aqin Liu, Zhihui Zhao, Zhongjun Li, Qing Li
According to our early researches, some glycoclusters having glucose, mannose, cellose and lactose residues showed good anti-adhesion activity of leukocytes to endothelial cells and exerted anti-inflammatory effects. Based on these results and combination principles of drugs, a series of new glycoclusters modifying with potentially anti-oxidant activity pharmacophores have been synthesized, and their anti-adhesion activities were assessed by static state cell-based adhesion assay. The results showed that some modified glycoclusters displayed better activities than their leading compound...
September 1, 2017: Carbohydrate Research
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