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  Subjects -> CHEMISTRY (Total: 845 journals)
    - ANALYTICAL CHEMISTRY (51 journals)
    - CHEMISTRY (595 journals)
    - CRYSTALLOGRAPHY (21 journals)
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CHEMISTRY (595 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 8)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 34)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 18)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 24)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 39)
ACS Nano     Full-text available via subscription   (Followers: 248)
ACS Photonics     Full-text available via subscription   (Followers: 11)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 21)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription   (Followers: 1)
Acta Chimica Slovaca     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 8)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 51)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 56)
Advances in Chemical Science     Open Access   (Followers: 13)
Advances in Chemistry     Open Access   (Followers: 15)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 9)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 16)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 9)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 21)
Advances in Nanoparticles     Open Access   (Followers: 15)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 17)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Science and Technology     Full-text available via subscription   (Followers: 12)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 2)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 67)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Chemistry     Open Access   (Followers: 27)
American Journal of Plant Physiology     Open Access   (Followers: 14)
American Mineralogist     Hybrid Journal   (Followers: 14)
Analyst     Full-text available via subscription   (Followers: 40)
Angewandte Chemie     Hybrid Journal   (Followers: 194)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 221)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 4)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 8)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 15)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 28)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 4)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Full-text available via subscription   (Followers: 309)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
Bioinspired Materials     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 1)
Biomacromolecules     Full-text available via subscription   (Followers: 19)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 5)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 119)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 91)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 3)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 4)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 66)
Catalysis for Sustainable Energy     Open Access   (Followers: 7)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 7)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 8)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 14)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 72)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 24)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 20)
Chemical Reviews     Full-text available via subscription   (Followers: 181)
Chemical Science     Open Access   (Followers: 22)
Chemical Technology     Open Access   (Followers: 16)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemical Week     Full-text available via subscription   (Followers: 8)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 58)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 26)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 6)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry - A European Journal     Hybrid Journal   (Followers: 149)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 20)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 44)
Chemistry of Materials     Full-text available via subscription   (Followers: 253)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 22)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 4)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 9)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 10)
Chromatographia     Hybrid Journal   (Followers: 24)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Cogent Chemistry     Open Access  
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 10)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 7)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 18)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 3)
Copernican Letters     Open Access   (Followers: 1)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Crystal Structure Theory and Applications     Open Access   (Followers: 4)
CrystEngComm     Full-text available via subscription   (Followers: 13)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Opinion in Molecular Therapeutics     Full-text available via subscription   (Followers: 17)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 61)
Dalton Transactions     Full-text available via subscription   (Followers: 23)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 12)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 4)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 3)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
EJNMMI Radiopharmacy and Chemistry     Open Access  
Elements     Full-text available via subscription   (Followers: 3)
Environmental Chemistry     Hybrid Journal   (Followers: 7)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 5)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)

        1 2 3 | Last

Journal Cover Carbohydrate Research
  [SJR: 0.612]   [H-I: 98]   [26 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0008-6215 - ISSN (Online) 0008-6215
   Published by Elsevier Homepage  [3048 journals]
  • A concise synthesis of rhamnan oligosaccharides with alternating
           α-(1→2)/(1→3)-linkages and repeating α-(1→3)-linkages by iterative
           α-glycosylation using disaccharide building blocks
    • Abstract: Publication date: Available online 14 November 2017
      Source:Carbohydrate Research
      Author(s): Hidenori Tanaka, Yu Hamaya, Nagatoshi Nishiwaki, Hideharu Ishida
      A concise synthetic route to rhamnan oligosaccharides with alternating α-(1→2)/(1→3)-linkages and repeating α-(1→3)-linkages is reported. This synthesis was achieved by iterative α-glycosylation using disaccharide building blocks and through orthogonal coupling between thioglycosides of L-rhamnose. To investigate the detailed structure-activity relationship of rhamnan sulfate from Monostroma nitidum against herpes simplex virus type 2, the synthesized oligosaccharides, bearing different orthogonal protecting groups (i.e., benzoyl, benzyl, 2-naphthylmethyl, and/or p-methoxybenzyl) are expected to be suitable for conversion into a range of rhamnan structures with diverse sulfation patterns.
      Graphical abstract image

      PubDate: 2017-11-16T12:19:17Z
       
  • Chemo-enzymatic synthesis of the glucagon containing N-linked
           oligosaccharide and its characterization
    • Abstract: Publication date: Available online 13 November 2017
      Source:Carbohydrate Research
      Author(s): Takayuki Higashiyama, Midori Umekawa, Masaya Nagao, Toshihiko Katoh, Hisashi Ashida, Kenji Yamamoto
      The chemo-enzymatic synthesis of an artificially N-glycosylated derivative of glucagon, a peptide hormone that regulates the blood sugar level, is described. We synthesized the glycosylated glucagon by chemical synthesis of an N-acetylglucosaminyl peptide and enzymatic transfer of an oligosaccharide using the transglycosylation activity of the glycosynthase-like mutant of Mucor hiemalis endo-β-N-acetylglucosaminidase (Endo-M) and sialo-oligosaccharide oxazoline as a donor substrate. The sialo-oligosaccharide-attached glucagon synthesized showed high resistance against protease degradation and stimulated the release of glucose from mouse hepatocytes when added to cells. The synthetic glucagon showed slightly higher activity than native glucagon and has potential as a therapeutic agent for treating diabetic patients.
      Graphical abstract image

      PubDate: 2017-11-16T12:19:17Z
       
  • Role of 6-O-α-maltosyl-β-cyclodextrin in lysosomal cholesterol
           deprivation in Npc1-deficient Chinese hamster ovary cells
    • Abstract: Publication date: Available online 10 November 2017
      Source:Carbohydrate Research
      Author(s): Yasuyo Okada, Erika Ueda, Yuki Kondo, Yoichi Ishitsuka, Tetsumi Irie, Taishi Higashi, Keiichi Motoyama, Hidetoshi Arima, Muneaki Matuso, Katsumi Higaki, Kousaku Ohno, Junichi Nishikawa, Atsushi Ichikawa
      We aimed to investigate whether 6-O-α-maltosyl-β-cyclodextrin (Mal-βCD) is incorporated into cells and lysosomes during the release of unesterified cholesterol in Npc1-deficient Chinese hamster ovary (CHO) cells (Npc1 KO cells) and CHO-JP17 cells (JP17 cells). Internalization of Mal-βCD in cells and lysosomes and extracellular release of lysosomal unesterified cholesterol were demonstrated by LC/MS/MS and LC/MS, respectively. Internalization of Mal-βCD was greater in Npc1 KO cells than in JP17 cells. The majority of internalized Mal-βCD in both cell types was metabolized by lysosomal α-glucosidase to 6-O-α-D-glucosyl-β-cyclodextrin (Glc-βCD). However, Mal-βCD did not directly enter the lysosomes prepared from cell homogenates. Mal-βCD-treated Npc1 KO cells and JP17 cells both released Mal-βCD and Glc-βCD, together with unesterified cholesterol, out of cells. The release of unesterified cholesterol by Mal-βCD in Npc1 KO cells was much greater than that in JP17 cells. This study is the first to report the influx of Mal-βCD into the lysosomes of Npc1 KO cells and JP17 cells, followed by generation of Glc-βCD, and the efflux of Mal-βCD/Glc-βCD and unesterified cholesterol to the extracellular fluid, based on the quantitative LC/MS analysis.
      Graphical abstract image

      PubDate: 2017-11-16T12:19:17Z
       
  • Synthesis of substrate analogues as potential inhibitors for Mycobacterium
           tuberculosis enzyme MshC
    • Abstract: Publication date: 1–14 December 2017
      Source:Carbohydrate Research, Volumes 453–454
      Author(s): 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.
      Graphical abstract image

      PubDate: 2017-11-09T07:26:15Z
       
  • Synthesis of
           P1-(11-phenoxyundecyl)-P2-(2-acetamido-2-deoxy-3-O-α-D-rhamnopyranosyl-α-D-glucopyranosyl)
           diphosphate and
           P1-(11-phenoxyundecyl)-P2-(2-acetamido-2-deoxy-3-O-β-D-galactopyranosyl-α-D-galactopyranosyl)
           diphosphate for the investigation of biosynthesis of O-antigenic
           polysaccharides in Pseudomonas aeruginosa and Escherichia coli O104
    • Abstract: Publication date: 1–14 December 2017
      Source:Carbohydrate Research, Volumes 453–454
      Author(s): Vladimir Torgov, Leonid Danilov, Natalia Utkina, Vladimir Veselovsky, Inka Brockhausen
      Two new phenoxyundecyl diphosphate sugars were synthesized for the first time: P1-(11-phenoxyundecyl)-P2- (2-acetamido-2-deoxy-3-O-α-D-rhamnopyranosyl-α-D-glucopyranosyl) diphosphate and P1-(11-phenoxyundecyl)-P2-(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.
      Graphical abstract image

      PubDate: 2017-11-09T07:26:15Z
       
  • Graphical contents list
    • Abstract: Publication date: 27 November 2017
      Source:Carbohydrate Research, Volume 452


      PubDate: 2017-11-09T07:26:15Z
       
  • Highly efficient synthesis of bioactive oleanane-type saponins
    • Abstract: Publication date: 27 November 2017
      Source:Carbohydrate Research, Volume 452
      Author(s): Jing-Jing Sui, Wen-Hui Zhou, De-Yong Liu, Ming-Qing Li, Jian-Song Sun
      Leveraging on Schmidt glycosylation method, a highly efficient approach to obtain oleanane-type triterpene saponins was fixed, whereby oleanyl mono-, disaccharide (guaianin N), trisaccharide (elatoside E), as well as tetrasaccharide (elatoside F) were obtained efficiently. The synthetic investigation has resulted in the discovery of the effect of branch-sugar incorporation sequence on the overall synthetic efficiency. Moreover, through bioactivity investigation, the cytotoxic activity of the obtained triterpenoid saponins was evaluated, and the preliminary structure-activity relationship was deduced.
      Graphical abstract image

      PubDate: 2017-11-09T07:26:15Z
       
  • Conjugation of carbohydrates to proteins using of di(triethylene glycol
           monomethyl ether) squaric acid ester revisited
    • Abstract: Publication date: Available online 7 November 2017
      Source:Carbohydrate Research
      Author(s): Peng Xu, Michael N. Trinh, Pavol Kováč
      Properties of di(triethylene glycol monomethyl ether) squarate relevant to conjugation of carbohydrates to proteins have been reinvestigated and compared with those of dimethyl squarate. It is concluded that the commercially available, crystalline dimethyl squarate remains the most convenient and efficient reagent for conjugation of amine-containing carbohydrates to proteins by a two-step or one-pot conjugation protocol
      Graphical abstract image

      PubDate: 2017-11-09T07:26:15Z
       
  • Isolation and characterisation of an unexpected byproduct in the
           regioselective butane diacetal protection of α-methyl galactopyranoside
    • Abstract: Publication date: Available online 6 November 2017
      Source:Carbohydrate Research
      Author(s): 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. Interestingly, the conformation of the resulting six-membered BDA ring was distorted to a skew boat conformation in order to maintain anomeric stabilisation.
      Graphical abstract image

      PubDate: 2017-11-09T07:26:15Z
       
  • Synthesis of 3-aminopropyl β-(1 → 6)-d-glucotetraoside and its
           biotinylated derivative
    • Abstract: Publication date: Available online 6 November 2017
      Source:Carbohydrate Research
      Author(s): Dmitry V. Yashunsky, Alexander A. Karelin, Yury E. Tsvetkov, Nikolay E. Nifantiev
      3-Aminopropyl β-(1 → 6)-d-glucotetraoside has been synthesized from 3-benzyloxycarbonylaminopropanol and 6-O-acetyl-2,3,4-tri-O-benzoyl-d-glucopyranosyl trichloroacetimidate by successive attachment of one monosaccharide unit in total yield of 22%. Free aminopropyl glycoside was converted into a biotin derivative that can be used for controlled immobilization of the oligosaccharide on streptavidin-coated ELISA plates and for tracing carbohydrate binding molecules.
      Graphical abstract image

      PubDate: 2017-11-09T07:26:15Z
       
  • Tandem mass spectrometry of fucoidan-derived fragments, labeled with
           heavy-oxygen
    • Abstract: Publication date: Available online 4 November 2017
      Source:Carbohydrate Research
      Author(s): 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 18O 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 0,2X0-type at m/z 287 and 2,4A-type at m/z 285, since 18O 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. cichorioides for the first time. It was also discovered that 2,4A-type fragments in 4-linked disaccharides that were incorrectly assigned to 0,2X-type previously, suggested, probably, substitution at C-4 in mono- and disaccharide fragments, derived from the fucoidan of the brown alga F. evanescens.
      Graphical abstract image

      PubDate: 2017-11-09T07:26:15Z
       
  • Supramolecular glycorhodamine-polymer dot ensembles for the homogeneous,
           fluorogenic analysis of lectins
    • Abstract: Publication date: Available online 1 November 2017
      Source:Carbohydrate Research
      Author(s): 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. This research provides insight into the development of simple fluorogenic probes for homogeneous lectin analyses based on the supramolecular assembly between polymeric nanoparticles and fluorescent glycoprobes.
      Graphical abstract image

      PubDate: 2017-11-02T07:01:48Z
       
  • Mannosylcalix[n]arenes as multivalent ligands for DC-SIGN
    • Abstract: Publication date: Available online 31 October 2017
      Source:Carbohydrate Research
      Author(s): 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. DC-SIGN is then considered an interesting target to fight the virus and multivalent systems exposing multiple copies of ligating units for its CRSs are becoming valuable tools to reach this goal. We herein prepared four mannosylated calix[n]arenes (1a-d) and tested them by Surface Plasmon Resonance (SPR) competition assays as inhibitors of the binding between DC-SIGN and a mannosylated BSA used as model of HIV gp120. IC50s in the μM range were found evidencing in particular for compound 1a that, although rather moderate, a multivalent effect is taking place in the inhibition activity of this cluster. A relative potency (rp/n) around 4, respect to the monovalent methyl α-mannoside and normalized for the number of monosaccharide on the scaffold, was observed. This result, compared with previously reported data relative to dendrimers with the same valency, indicates the calixarene as a promising scaffold to build efficient inhibitors for DC-SIGN and, in perspective, for HIV.
      Graphical abstract image

      PubDate: 2017-11-02T07:01:48Z
       
  • The Shewanella woodyi galactokinase pool phosphorylates glucose at the
           6-position
    • Abstract: Publication date: Available online 31 October 2017
      Source:Carbohydrate Research
      Author(s): Louis Patrick Conway, Fang Fang Liu, Qian Li, Josef Voglmeir
      Galactokinases are a class of enzymes which belong to the GHMP (galactokinase, homoserine kinase, mevalonate kinase, and phosphomevalonate kinase) superfamily and catalyse the phosphorylation of galactose in the first step of the Leloir pathway. Here we report the discovery of three enzymes from Shewanella woodyi which have been classified as galactokinases based on sequence similarity. However, each of these enzymes show little to no significant activity towards galactose and instead exhibit a strong preference for glucose. Furthermore, in contrast to the usual galactose-1-phosphate product of the galactokinase-catalysed reaction, these enzymes produce glucose-6-phosphate. This radical change in enzyme functionality is postulated to be linked to the mutation of a glycine residue which is conserved in all other sequenced galactokinases.
      Graphical abstract image

      PubDate: 2017-11-02T07:01:48Z
       
  • Overview on the antiviral activities and mechanisms of marine
           polysaccharides from seaweeds
    • Abstract: Publication date: Available online 31 October 2017
      Source:Carbohydrate Research
      Author(s): 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. Moreover, the antiviral mechanisms and medical applications of certain marine polysaccharides from seaweeds are also demonstrated.
      Graphical abstract image

      PubDate: 2017-11-02T07:01:48Z
       
  • Effect of sucralose on the enzyme kinetics of invertase using real-time
           NMR spectroscopy and progress curve analysis
    • Abstract: Publication date: Available online 31 October 2017
      Source:Carbohydrate Research
      Author(s): 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. This affects the rate of glucose production, and thus indirectly affecting the mutarotation process of α-D-glucose to β-D-glucose conversion. At a 1:2 molar ratio of sucrose to sucralose, the results show that the catalytic efficiency of the enzyme is reduced by more than 50% in comparison to the measurements without sucralose. Altogether, as sucralose alters the rate of glucose production, sucralose cannot be considered inert to the metabolism as several downstream events in both prokaryotic and eukaryotic systems strongly depend on the rate of glucose metabolism.
      Graphical abstract image

      PubDate: 2017-11-02T07:01:48Z
       
  • Graphical contents list
    • Abstract: Publication date: 8 November 2017
      Source:Carbohydrate Research, Volume 451


      PubDate: 2017-10-26T03:58:36Z
       
  • Synthesis and gelation property of a series of disaccharide triazole
           derivatives
    • Abstract: Publication date: 8 November 2017
      Source:Carbohydrate Research, Volume 451
      Author(s): 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. The self-assembling properties of selected lactosyl and maltosyl triazole derivatives were studied using 1H NMR spectroscopy at different temperatures. The NMR studies revealed that the triazole moiety in these compounds played an important role in the formation of the supramolecular assembly, but the sugar moiety configurations are more influential towards gelation. Naproxen and chloramphenicol were used as the model drugs to assess the potential of these compounds in drug delivery applications. A pH responsive gelator showed faster delivery of chloramphenicol at mild basic conditions than neutral conditions. The effective disaccharide triazole-based molecular gelators are useful for the preparation of advanced soft materials that have potential applications as matrix for immobilization of drugs or biomolecules.
      Graphical abstract image

      PubDate: 2017-10-26T03:58:36Z
       
  • Recent advances in the chemical synthesis of sugar-nucleotides
    • Abstract: Publication date: 8 November 2017
      Source:Carbohydrate Research, Volume 451
      Author(s): Sanaz Ahmadipour, Gavin J. Miller
      Graphical abstract image

      PubDate: 2017-10-26T03:58:36Z
       
  • Membrane-enclosed multienzyme (MEME) synthesis of 2,7-anhydro-sialic acid
           derivatives
    • Abstract: Publication date: 8 November 2017
      Source:Carbohydrate Research, Volume 451
      Author(s): Marie Monestier, Dimitrios Latousakis, Andrew Bell, Sandra Tribolo, Louise E. Tailford, Ian J. Colquhoun, Gwenaelle Le Gall, Hai Yu, Xi Chen, Martin Rejzek, Simone Dedola, Robert A. Field, Nathalie Juge
      Naturally occurring 2,7-anhydro-alpha-N-acetylneuraminic acid (2,7-anhydro-Neu5Ac) is a transglycosylation product of bacterial intramolecular trans-sialidases (IT-sialidases). A facile one-pot two-enzyme approach has been established for the synthesis of 2,7-anhydro-sialic acid derivatives including those containing different sialic acid forms such as Neu5Ac and N-glycolylneuraminic acid (Neu5Gc). The approach is based on the use of Ruminoccocus gnavus IT-sialidase for the release of 2,7-anhydro-sialic acid from glycoproteins, and the conversion of free sialic acid by a sialic acid aldolase. This synthetic method, which is based on a membrane-enclosed enzymatic synthesis, can be performed on a preparative scale. Using fetuin as a substrate, high-yield and cost-effective production of 2,7-anhydro-Neu5Ac was obtained to high-purity. This method was also applied to the synthesis of 2,7-anhydro-Neu5Gc. The membrane-enclosed multienzyme (MEME) strategy reported here provides an efficient approach to produce a variety of sialic acid derivatives.
      Graphical abstract image

      PubDate: 2017-10-26T03:58:36Z
       
  • Cellodextrin phosphorylase from Ruminiclostridium thermocellum: X-ray
           crystal structure and substrate specificity analysis
    • Abstract: Publication date: 8 November 2017
      Source:Carbohydrate Research, Volume 451
      Author(s): Ellis C. O'Neill, Giulia Pergolizzi, Clare E.M. Stevenson, David M. Lawson, Sergey A. Nepogodiev, Robert A. Field
      The GH94 glycoside hydrolase cellodextrin phosphorylase (CDP, EC 2.4.1.49) produces cellodextrin oligomers from short β-1→4-glucans and α-D-glucose 1-phosphate. Compared to cellobiose phosphorylase (CBP), which produces cellobiose from glucose and α-D-glucose 1-phosphate, CDP is biochemically less well characterised. Herein, we investigate the donor and acceptor substrate specificity of recombinant CDP from Ruminiclostridium thermocellum and we isolate and characterise a glucosamine addition product to the cellobiose acceptor with the non-natural donor α-D-glucosamine 1-phosphate. In addition, we report the first X-ray crystal structure of CDP, along with comparison to the available structures from CBPs and other closely related enzymes, which contributes to understanding of the key structural features necessary to discriminate between monosaccharide (CBP) and oligosaccharide (CDP) acceptor substrates.
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      PubDate: 2017-10-26T03:58:36Z
       
  • Properties of two fungal endo-β-1,3-galactanases and their synergistic
           action with an exo-β-1,3-galactanase in degrading
           arabinogalactan-proteins
    • Abstract: Publication date: Available online 25 October 2017
      Source:Carbohydrate Research
      Author(s): 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. The recombinant Af3G (rAf3G) and rNcEn3GAL expressed in Pichia pastoris specifically hydrolyzed β-1,3-galactan in an endo-manner, as did the rFvEn3GAL. Among galactooligosaccharides, β-1,3-galactotriose was identified as the smallest substrate for these enzymes. These results suggest that enzymatic characteristics are conserved in many endo-β-1,3-galactanases belonging to the glycoside hydrolase 16 family. On the other hand, rAf3G and rNcEn3GAL generated more β-1,3-galactobiose from β-1,3-galactotetraose than did rFvEn3GAL, suggesting that rAf3G and rNcEn3GAL prefer hydrolyzing the central β-1,3-glycosidic linkage of three in β-1,3-galactotetraose. Although rAf3G and rNcEn3GAL alone hardly hydrolyze native AGP, they acted synergistically with a fungal exo-β-1,3-galactanase on the AGP. These endo-β-1,3-galactanases presumably aid hydrolysis by internally breaking up AGPs, which creates more sites of attack for exo-β-1,3-galactanase.
      Graphical abstract image

      PubDate: 2017-10-26T03:58:36Z
       
  • Monitoring of reactions catalyzed by lytic polysaccharide monooxygenases
           using highly-sensitive fluorimetric assay of the oxygen consumption rate
    • Abstract: Publication date: Available online 24 October 2017
      Source:Carbohydrate Research
      Author(s): Alexander V. Gusakov, Alexander G. Bulakhov, Ilya N. Demin, Arkady P. Sinitsyn
      Lytic polysaccharide monooxygenases (LPMOs) are recently discovered enzymes that catalyze the oxidative deconstruction of polysaccharides. However fast and reliable methods of determination of LPMO activity still need to be developed, especially those based on the initial reaction rates. A method based on the oxygen consumption rate (OCR) measurements, using a Seahorse XFp Analyzer with highly-sensitive fluorimetric sensors, was applied for monitoring the oxidation of amorphous cellulose by three fungal LPMOs: recombinant enzymes from Thielavia terrestris (GH61E), Trichoderma reesei (Cel61A), and a native LPMO9A from Myceliophthora thermophila. The turnover numbers for 4 μM enzymes acting on 4 mg mL−1 cellulose at 37 °C were 0.88, 1.26 and 0.93 min−1, respectively. A possibility of feeding the dissolved reagents into the reaction system during measurements with obtaining a simultaneous response in the OCR allowed in situ monitoring the LPMO inhibition and activation by EDTA and Cu2+ ions as well as studying other effects on the enzymatic reaction.
      Graphical abstract image

      PubDate: 2017-10-26T03:58:36Z
       
  • Regioselective glycosylation of novobiocin alters activity
    • Abstract: Publication date: Available online 22 October 2017
      Source:Carbohydrate Research
      Author(s): Guoxuan Sun, Pedro Ernesto de Resende, Paul Stapleton, Martyna Kuta, Xiangtao Wang, Shozeb Haider, Min Yang
      Glycosylation is a promising approach to overcome antimicrobial drug resistance. In this study, we investigated Koenigs-Knorr and phase transfer glycosylation on novobiocin. While the former only gave a 4′-OH product, the later produced mainly a kinetic controlled 5-OH product, but still achieved the 4′-OH modification and novoise-glycosylated products (with stronger base), as well as a diglycosylated compound. Investigation on the antibacterial activity indicate that the presence of galactose moiety helps to improve activity possibly via enhanced cellular uptake.
      Graphical abstract image

      PubDate: 2017-10-26T03:58:36Z
       
  • Boronic acid-based chemical sensors for saccharides
    • Abstract: Publication date: Available online 20 October 2017
      Source:Carbohydrate Research
      Author(s): Xiao-tai Zhang, Guang-jian Liu, Zhang-wei Ning, Guo-wen Xing
      During the past decades, the interaction between boronic acids-functionalized sensors and saccharides is of great interest in the frontier domain of the interdiscipline concerning both biology and chemistry. Various boronic acid-based sensing systems have been developed to detect saccharides and corresponding derivatives in vitro as well as in vivo, which embrace unimolecular sensors, two-component sensing ensembles, functional assemblies, and boronic acid-loaded nanomaterials or surfaces. New sensing strategies emerge in endlessly with excellent selectivity and sensitivity. In this review, several typical sensing systems were introduced and some promising examples were highlighted to enable the deep insight of saccharides sensing on the basis of boronic acids.
      Graphical abstract image

      PubDate: 2017-10-26T03:58:36Z
       
  • Acinetobacter baumannii K13 and K73 capsular polysaccharides differ only
           in K-unit side branches of novel non-2-ulosonic acids: di-N-acetylated
           forms of either acinetaminic acid or 8-epiacinetaminic acid
    • Abstract: Publication date: Available online 19 October 2017
      Source:Carbohydrate Research
      Author(s): Johanna J. Kenyon, Anastasiya A. Kasimova, Anna Notaro, Nikolay P. Arbatsky, Immacolata Speciale, Alexander S. Shashkov, Cristina De Castro, Ruth M. Hall, Yuriy A. Knirel
      Structures of capsular polysaccharides of Acinetobacter baumannii isolates carrying KL13 and KL73 gene clusters were established. The closely related KL73 and KL13 gene clusters differ only by one gene in the module responsible for synthesis of the non-2-ulosonic acids. The K13 and K73 polysaccharides differ only in a single side-chain sugar, which is either 5,7-diacetamido-3,5,7,9-tetradeoxy-l-glycero-l-altro- or -d-glycero-l-altro-non-2-ulosonic acid [di-N-acetylated forms of acinetaminic acid (Aci5Ac7Ac) or 8-epiacinetaminic acid (8eAci5Ac7Ac), respectively]. → 4 ) - α - D - Gal p - ( 1 → 3 ) - α - L - Fuc p NAc - ( 1 → 3 ) - α - D - Fuc p NAc - ( 1 → 6 ↑ 2 α - Sug p Sug = Aci 5 Ac 7 Ac in K 13 or 8 eAci 5 Ac 7 Ac in K 73 The KL13 also is closely related to the KL12 gene cluster, which contains a different wzy gene encoding the K unit polymerase. Accordingly, the otherwise near identical K units are linked differently via an α-d-FucpNAc-(1 → 4)-d-Galp linkage in K13 and K73 or an α-d-FucpNAc-(1 → 3)-d-GalpNAc linkage in K12. This finding confirms the predicted substrate of the ItrB3 initiating transferase as d-FucpNAc. Glycosyltransferases predicted to catalyse the linkage of d-Galp or d-GalpNAc to l-FucpNAc in the growing K13 and K73 or K12 units, respectively, differ by only two amino acids.
      Graphical abstract image

      PubDate: 2017-10-26T03:58:36Z
       
  • Concise synthesis of 2,7-anhydrosialic acid derivatives and its
           application
    • Abstract: Publication date: Available online 19 October 2017
      Source:Carbohydrate Research
      Author(s): 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. The iMAP simultaneously circumvents both the 2- and 7-OH protection. Upon protecting the 8- and 9-OH groups as a benzylidene acetal, only 4-OH is free for glycosylation. These 2,7-anhydro-8,9-O-benzylidenesialic acid derivatives were examined as acceptor for an α-selective fucosylation to construct the glycosidic linkage of fucosyl α(1 → 4) 2,7-anhydroneuraminic acid.
      Graphical abstract image

      PubDate: 2017-10-26T03:58:36Z
       
  • Recent advances in the synthesis of rare sugars using DHAP-Dependent
           aldolases
    • Abstract: Publication date: Available online 18 October 2017
      Source:Carbohydrate Research
      Author(s): Aimin Li, Li Cai, Zhou Chen, Mayan Wang, Ning Wang, Hideki Nakanishi, Xiao-Dong Gao, Zijie Li
      The occurrence rates of non-communicable diseases like obesity, diabetes and hyperlipidemia have increased remarkably due to excessive consumption of a high-energy diet. Rare sugars therefore have become increasingly attractive owing to their unique nutritional properties. In the past two decades, various rare sugars have been successfully prepared guided by the “Izumoring strategy”. As a valuable complement to the Izumoring approach, the controllable dihydroxyacetone phosphate (DHAP)-dependent aldolases have generally predictable regio- and stereoselectivity, which makes them powerful tools in C-C bond construction and rare sugar production. However, the main disadvantage for this group of aldolases is their strict substrate specificity toward the donor molecule DHAP, a very expensive and relatively unstable compound. Among the current methods involving DHAP, the one that couples DHAP production from inexpensive starting materials (for instance, glycerol, DL-glycerol 3-phosphate, dihydroxyacetone, and glucose) with aldol condensation appears to be the most promising. This review thus focuses on recent advances in the application of L-rhamnulose-1-phosphate aldolase (RhaD), L-fuculose-1-phosphate aldolase (FucA), and D-fructose-1,6-bisphosphate aldolase (FruA) for rare sugar synthesis in vitro and in vivo, while illustrating strategies for supplying DHAP in efficient and economical ways.
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      PubDate: 2017-10-26T03:58:36Z
       
  • Characterization of structural motifs for interactions between
           glycosaminoglycans and proteins
    • Abstract: Publication date: Available online 17 October 2017
      Source:Carbohydrate Research
      Author(s): Jiyuan Yang, Lianli Chi
      Glycosaminoglycans (GAGs) are a family of linear and anionic polysaccharides that play essential roles in many biological and physiological processes. Interactions between GAGs and proteins regulate function in many proteins and are related to many human diseases and disorders. The structural motifs and mechanisms for interactions between GAGs and proteins are not fully understood. Specific bindings, including minor but unique sequences sporadically distributed along the GAG chains or variably sulfated domains interspersed by undersulfated regions, may be specifically recognized by defined domains of a variety of proteins. Understanding the molecular basis of these interactions will provide a template for developing novel glycotherapeutic agents. The present article reviews recent methodologies and progress on the characterization of structural motifs in both GAGs and proteins involved in GAG-protein interactions. The analytical approaches are categorized into three groups: affinity-based methods; molecular docking, nuclear magnetic resonance (NMR) spectroscopy and X-ray crystallography; and mass spectrometry (MS) techniques. The advantages and limitations of each category of methods are discussed and are based on examples of using these techniques to investigate binding between GAGs and proteins.
      Graphical abstract image

      PubDate: 2017-10-26T03:58:36Z
       
  • NKT-cell glycolipid agonist as adjuvant in synthetic vaccine
    • Abstract: Publication date: Available online 17 October 2017
      Source:Carbohydrate Research
      Author(s): Zheng Liu, Jun Guo
      NKT cells are CD1d-restricted, glycolipid antigen-reactive, immunoregulatory T lymphocytes that can serve as a bridge between the innate and adaptive immunities. NKT cells have a wide range of therapeutic application in autoimmunity, transplant biology, infectious disease, cancer, and vaccinology. Rather than triggering “danger signal” and eliciting an innate immune response, αGalCer-based NKT-cell agonist act via a unique mechanism, recruiting NKT cells which play a T helper-like role even without peptide as Th epitope. Importantly, the non-polymorphism of CD1d render glycolipid a universal helper epitope, offering the potential to simplify the vaccine construct capable of eliciting consistent immune response in different individuals. This review details recent advances in the design of synthetic vaccines using NKT-cell agonist as adjuvant, highlighting the role of organic synthesis and conjugation technique to enhance the immunological actives and to simplify the vaccine constructs.
      Graphical abstract image

      PubDate: 2017-10-26T03:58:36Z
       
  • Improved isolation and characterization procedure of sialylglycopeptide
           from egg yolk powder
    • Abstract: Publication date: Available online 12 October 2017
      Source:Carbohydrate Research
      Author(s): Lin Liu, Anthony R. Prudden, Gerlof P. Bosman, Geert-Jan Boons
      Sialylglycopeptide (SGP) is a complex bi-antennary N-glycan bearing a short peptide fragment that can be isolated from the yolk of hen eggs. This natural product has gained popularity as a starting material for the semi-synthesis of N-glycans. We have found that current isolation methods provide a glycopeptide contaminated with several related structures, one being a glycopeptide having a hexose directly attached to peptide backbone, most like through the hydroxyl containing side chain of the threonine moiety. Furthermore, current methods employ fresh egg yolks that need to be lyophilized and involve several tedious purification steps. Herein, we report a convenient method for the isolation of gram quantities of homogeneous SGP from commercially available egg yolk powder using solid/liquid extraction and HILIC-HPLC purification.
      Graphical abstract image

      PubDate: 2017-10-14T14:20:40Z
       
  • Novel 1,2-cis-stereoselective glycosylations utilizing organoboron
           reagents and their application to natural products and complex
           oligosaccharide synthesis
    • Abstract: Publication date: Available online 12 October 2017
      Source:Carbohydrate Research
      Author(s): Daisuke Takahashi, Masamichi Tanaka, Nobuya Nishi, Kazunobu Toshima
      In this mini-review article, 1,2-cis-stereoselective glycosylation methods utilizing organoboron reagents and 1,2-anhydroglycosyl donors that were developed in our laboratory, including regio- and 1,2-cis-stereoselective glycosylations using glycosyl-acceptor-derived boronic ester catalysts and 1,2-cis-stereoselective glycosylations using glycosyl-acceptor-derived borinic ester catalysts, are recounted. Representative applications of these methods to the synthesis of biologically active natural products and a complex oligosaccharide are also described.
      Graphical abstract image

      PubDate: 2017-10-14T14:20:40Z
       
  • Synthesis of LewisX-O-core-1 threonine: A building block for O-linked
           LewisX glycopeptides
    • Abstract: Publication date: Available online 10 October 2017
      Source:Carbohydrate Research
      Author(s): Mohammed Y.R. Sardar, Venkata R. Krishnamurthy, Simon Park, Appi R. Mandhapati, Walter J. Wever, Dayoung Park, Richard D. Cummings, Elliot L. Chaikof
      Lewis X (LeX) is a branched trisaccharide Galβ1→4(Fucα1→3)GlcNAc that is expressed on many cell surface glycoproteins and plays critical roles in innate and adaptive immune responses. However, efficient synthesis of glycopeptides bearing LeX remains a major limitation for structure-function studies of the LeX determinant. Here we report a total synthesis of a LeX pentasaccharide 1 using a regioselective 1-benzenesulfinyl piperidine/triflic anhydride promoted [3 + 2] glycosylation. The presence of an Fmoc-threonine amino acid facilitates incorporation of the pentasaccharide in solid phase peptide synthesis, providing a route to diverse O-linked LeX glycopeptides. The described approach is broadly applicable to the synthesis of a variety of complex glycopeptides containing O-linked LeX or sialyl LewisX (sLeX).
      Graphical abstract image

      PubDate: 2017-10-11T14:12:53Z
       
  • Chemical remodeling cell surface glycans for immunotargeting of tumor
           cells
    • Abstract: Publication date: Available online 10 October 2017
      Source:Carbohydrate Research
      Author(s): Xuexia Li, Xiaoyan Xu, Xiongjian Rao, Yinping Tian, Wen Yi
      Recruitment of human endogenous antibodies to target and eliminate tumor cells is a promising therapeutic strategy in the biomedical field. Current antibody-recruiting molecules are typically bi-functional agents that utilize cell-surface receptor binding property for targeting. This approach has intrinsic limitations due to the heterogeneity of tumor cells and the limited number of receptors on the cell surface. Here we report a targeting strategy based on remodeling of cell surface glycans through metabolic engineering and bioorthogonal chemical ligation. In vitro cultured tumor cells and in vivo xenograft tumors were actively remodeled with rhamnose carbohydrate epitopes, which were capable of recruiting endogenous anti-rhamnose antibodies and activating complement-mediated cell cytotoxicity. This study highlights the therapeutic potential for modulating endogenous immune response through cell-surface glycan engineering.
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      PubDate: 2017-10-11T14:12:53Z
       
  • Synthesis and binding affinity analysis of α1-2- and α1-6-O/S-linked
           dimannosides for the elucidation of sulfur in glycosidic bonds using
           quartz crystal microbalance sensors
    • Abstract: Publication date: Available online 9 October 2017
      Source:Carbohydrate Research
      Author(s): Oscar Norberg, Bin Wu, Niranjan Thota, Jiantao Ge, Germain Fauquet, Ann-Kathrin Saur, Teodor Aastrup, Hai Dong, Mingdi Yan, Olof Ramström
      The role of sulfur in glycosidic bonds has been evaluated using quartz crystal microbalance methodology. Synthetic routes towards α1-2- and α1-6-linked dimannosides with S- or O-glycosidic bonds have been developed, and the recognition properties assessed in competition binding assays with the cognate lectin concanavalin A. Mannose-presenting QCM sensors were produced using photoinitiated, nitrene-mediated immobilization methods, and the subsequent binding study was performed in an automated flow-through instrumentation, and correlated with data from isothermal titration calorimetry. The recorded K d-values corresponded well with reported binding affinities for the O-linked dimannosides with affinities for the α1-2-linked dimannosides in the lower micromolar range. The S-linked analogs showed slightly disparate effects, where the α1-6-linked analog showed weaker affinity than the O-linked dimannoside, as well as positive apparent cooperativity, whereas the α1-2-analog displayed very similar binding compared to the O-linked structure.
      Graphical abstract image

      PubDate: 2017-10-11T14:12:53Z
       
  • 1H NMR studies of molecular interaction of D-glucosamine and
           N-acetyl-D-glucosamine with capsaicin in aqueous and non-aqueous media
    • Abstract: Publication date: Available online 29 September 2017
      Source:Carbohydrate Research
      Author(s): Inocencio Higuera-Ciapara, Claudia Virués, Marcela Jiménez-Chávez, Evelin Martínez-Benavidez, Javier Hernández, Zaira Domínguez, Roberto López-Rendón, Enrique F. Velázquez, Motomichi Inoue
      Complex formation of D-glucosamine (Gl) and N-acetyl-D-glucosamine (AGl) with capsaicin (Cp) were studied by 1H NMR titrations in H2O-d2 and DMSO-d6; capsaicin is the major bioactive component of chili peppers. Every titration curve has been interpreted by formulating a suitable model for the reaction equilibrium, to elucidate intermolecular interactions. In DMSO, glucosamine cations associate with each other to yield linear aggregates, and undergo pseudo-1:1-complexation with capsaicin, the formation constant being ca. 30 M−1. N-Acetylglucosamine, without self-association, forms a 2:1-complex AGl2Cp with the stability of ca. 70 M−2. These complexations are achieved by intermolecular hydrogen bonds. In D2O, glucosamine undergoes reversible protonation equilibrium between Gl0 and GlH+ with the logarithmic protonation constants log K D  = 8.63 for α-glucosamine and 8.20 for β-isomer. Both anomeric isomers of deprotonated glucosamine form Gl0Cp-type complexes of capsaicin, in a competitive manner, with a formation constant of 1040 M−1 for the α-glucosamine complex and 830 M−1 for the β-complex; the anomeric carbons result in the difference in thermodynamic stability. The reactant molecules are closed up by the solvent-exclusion effect and/or the van der Waals interaction; the resulting pair is stabilized by intermolecular hydrogen bonding within a local water-free space between the component molecules. By contrast, neither protonated glucosamine (GlH+) nor N-acetylglucosamine yields a capsaicin complex with the definite stoichiometry. The monosaccharides recognize capsaicin under only a controlled condition; the same phenomena are predicted for biological systems and nanocarriers based on polysaccharides such as chitosan.
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      PubDate: 2017-10-03T13:54:57Z
       
  • Tracking the leaving group in the remote activation of
           O-2-[(propan-2-yl)sulfinyl]benzyl (OPSB) glycoside
    • Abstract: Publication date: Available online 28 September 2017
      Source:Carbohydrate Research
      Author(s): Wei Chen, Jing Zeng, Hao Wang, Xiong Xiao, Lingkui Meng, Qian Wan
      In our recently developed interrupted Pummerer reaction mediated glycosylation with O-2-[(propan-2-yl)sulfinyl]benzyl (OPSB) glycosides as glycosyl donors, the anomeric leaving group was recovered as a benzyl alcohol which didn't affect the glycosylation efficiency. To investigate the mechanism of the occurrence of this alcohol, an 18O isotopic labeling reaction was carried out to track the leaving group. It was found that the benzyl alcohol was generated during the aqueous work up process from an inactive cyclic oxo-sulfonium ion intermediate. It was also proved that H2O prefer to attack the sulfur atom position during the hydrolysis of the intermediate.
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      PubDate: 2017-10-03T13:54:57Z
       
  • Preparation of new β-D-xyloside- and β-D-xylobioside-based ionic liquids
           through chemical and/or enzymatic reactions
    • Abstract: Publication date: Available online 23 September 2017
      Source:Carbohydrate Research
      Author(s): 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).
      Graphical abstract image

      PubDate: 2017-09-26T13:45:26Z
       
  • Structural characterisation of the capsular polysaccharide expressed by
           Burkholderia thailandensis strain E555:: wbiI (pKnock-KmR) and assessment
           of the significance of the 2-O-acetyl group in immune protection
    • Abstract: Publication date: Available online 21 September 2017
      Source:Carbohydrate Research
      Author(s): Marc Bayliss, Matthew I. Donaldson, Sergey A. Nepogodiev, Giulia Pergolizzi, Andrew E. Scott, Nicholas J. Harmer, Robert A. Field, Joann L. Prior
      Burkholderia pseudomallei and its close relative B. mallei are human pathogens that are classified as Tier 1 bio-threat agents. Both organisms have previously been shown to constitutively produce a capsular polysaccharide (CPS) that is both a virulence determinant and protective antigen. Extraction and purification of CPS for use as a potential vaccine candidate requires containment level 3 laboratories which is expensive and time-consuming. B. thailandensis strain E555 is closely related to B. pseudomallei and B. mallei, but is non-pathogenic to humans and based on immunological cross-reactivity has previously been shown to express a B. pseudomallei-like CPS. In this study, capsular polysaccharide isolated from an O-antigen deficient strain of B. thailandensis E555 was identified by 1H and 13C NMR spectroscopy as -3-)-2-O-acetyl-6-deoxy-β-d-manno-heptopyranose-(-1, and identical to that produced by B. pseudomallei. This was further substantiated by anti-CPS monoclonal antibody binding. In connection with the production of CPS fragments for use in glycoconjugate vaccines, we set out to assess the importance or otherwise of the CPS 2-OAc groups in immune protection. To this end conjugates of the native and de-O-acetylated CPS with the Hc fragment of tetanus toxin (TetHc) were used as vaccines in a mouse model of melioidosis. The level of protection provided by deacetylated CPS was significantly lower than that from native, acetylated CPS. In addition, sera from mice vaccinated with the deacetylated CPS conjugate did not recognise native CPS. This suggests that CPS extracted from B. thailandensis can be used as antigen and that the acetyl group is essential for protection.
      Graphical abstract image

      PubDate: 2017-09-26T13:45:26Z
       
  • Base-modified GDP-mannose derivatives and their substrate activity towards
           a yeast mannosyltransferase
    • Abstract: Publication date: Available online 21 September 2017
      Source:Carbohydrate Research
      Author(s): Alice Collier, Gerd K. Wagner
      We have previously developed a new class of inhibitors and chemical probes for glycosyltransferases through base-modification of the sugar-nucleotide donor. The key feature of these donor analogues is the presence of an additional substituent at the nucleobase. To date, the application of this general concept has been limited to UDP-sugars and UDP-sugar-dependent glycosyltransferases. Herein, we report for the first time the application of our approach to a GDP-mannose-dependent mannosyltransferase. We have prepared four GDP-mannose derivatives with an additional substituent at either position 6 or 8 of the nucleobase. These donor analogues were recognised as donor substrates by the mannosyltransferase Kre2p from yeast, albeit with significantly lower turnover rates than the natural donor GDP-mannose. The presence of the additional substituent also redirected enzyme activity from glycosyl transfer to donor hydrolysis. Taken together, our results suggest that modification of the donor nucleobase is, in principle, a viable strategy for probe and inhibitor development against GDP-mannose-dependent GTs.
      Graphical abstract image

      PubDate: 2017-09-26T13:45:26Z
       
  • The convergent synthesis and anticancer activity of broussonetinines
           related analogues
    • Abstract: Publication date: Available online 19 September 2017
      Source:Carbohydrate Research
      Author(s): 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. Compound 3 exhibited very good in vitro potency on Caco-2 and Jurkat cell lines with IC50 value of 5.1 μM and 5.8 μM, respectively.
      Graphical abstract image

      PubDate: 2017-09-26T13:45:26Z
       
  • Limitations in the description of conformational preferences of
           C-disaccharides: The (1 → 3)-C-mannobiose case
    • Abstract: Publication date: Available online 18 September 2017
      Source:Carbohydrate Research
      Author(s): 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. In order to verify predicted conformational preferences, vicinal 3 J HH NMR coupling constants were calculated by the Karplus equation on simulated potential energy surfaces (PES). A set of new parameters for the Karplus equation was also designed. Predicted 3 J HH were compared with experimental data. We also used reverse methodology, in which the 3 J HH coupling constants were calculated at the DFT level for each family of (ϕ, ψ)-conformers separately and then experimental values were decomposed onto calculated 3 J HH couplings in order to obtain experimentally derived populations of conformers. As an alternative method of evaluation of preferred conformers, analysis of sensitive 13C chemical shifts was introduced. We were able to thoroughly discuss several fundamental issues in predictions of preferred conformers of C-saccharides, such as the solvent effect, reliability of the force field, character of empirical Karplus equation or applicability of NMR parameters in predictions of conformational preferences in general.
      Graphical abstract image

      PubDate: 2017-09-19T19:38:50Z
       
  • Synthesis of a biotinylated keratan sulfate tetrasaccharide composed of
           dimeric Galβ1-4GlcNAcβ6S
    • Abstract: Publication date: Available online 18 September 2017
      Source:Carbohydrate Research
      Author(s): Naoko Takeda-Okuda, Yoshiki Yamaguchi, Jun Uzawa, Jun-ichi Tamura
      We successfully synthesized the biotinylated keratan sulfate tetrasaccharide, Galβ1-4GlcNAc(6S)β1-3Galβ1-4GlcNAcβ(6S) in a stereocontrolled manner. The suitably protected Galβ1-4GlcNPhth unit was converted to the corresponding donor and acceptor. Optimization in 2 + 2 coupling using AgOTf, CuBr2, and n-Bu4NBr in CH3NO2 at a low temperature afforded the desired tetrasaccharide that suppressed glycal formation. The subsequent chemoselective removal of the protecting group at O-6 of two GlcNAcs, sulfation, and deprotection procedures as well as biotinylation gave the target compound.
      Graphical abstract image

      PubDate: 2017-09-19T19:38:50Z
       
  • Chemoenzymatic synthesis of Neu5Ac9NAc-containing α2–3- and
           α2–6-linked sialosides and their use for sialidase substrate
           specificity studies
    • Abstract: Publication date: Available online 18 September 2017
      Source:Carbohydrate Research
      Author(s): Wanqing Li, An Xiao, Yanhong Li, Hai Yu, Xi Chen
      O-Acetylation of sialic acid (Sia) modulates its recognition by sialic acid-binding proteins and plays an important role in biological and pathological processes. 9-O-Acetylation is the most common modification of sialic acid in human. However, study of O-acetylated sialoglycans is hampered due to the instability of O-acetyl group towards pH changes and sensitivity to esterases. Our previous studies demonstrated a chemical biology method to this problem by replacing the oxygen atom in the C9 ester group of sialic acid by a nitrogen to form an amide. Here, we synthesized a library of sixteen new 9-acetamido-9-deoxy-N-acetylneuraminic acid (Neu5Ac9NAc)-containing α2–3- and α2–6-linked sialosides with various underlying glycans using efficient one-pot three-enzyme (OP3E) sialylation systems. Neu5Ac9NAc-containing compounds with a para-nitrophenol aglycon have been used together with their 9-O-acetyl analogs in microtiter plate-based high-throughput substrate specificity studies of nine different sialidases including those from humans and bacteria. In general, similar to 9-O-acetylation, 9-N-acetyl modification of sialic acid in the substrates lowers sialic acid-cleavage activity of most sialidases. In most cases, Neu5Ac9NAc is a good analog of 9-O-acetyl sialic acid. However, exceptions do exist. For example, 9-N- and 9-O-acetyl modifications have different effects on the sialosides cleave efficiencies of a commercially available C. perfringens sialidase as well as recombinant Streptococcus pneumoniae sialidase SpNanC and Bifidobacterium infantis sialidase BiNanH2. The mechanism for the difference awaits further investigation.
      Graphical abstract image

      PubDate: 2017-09-19T19:38:50Z
       
  • Theoretical study on the anomeric effect in α-substituted
           tetrahydropyrans and piperidines
    • Abstract: Publication date: Available online 15 September 2017
      Source:Carbohydrate Research
      Author(s): 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 J C,H and 1 J C,F coupling constants, respectively, in axial and equatorial conformers. However, the preference for an equatorial conformation appears when a hydrogen or methyl group of the substituent faces the ring, increasing the steric repulsion, even if concomitant with a hyperconjugative interaction in the axial isomer, such as for the well-known 2-aminotetrahydropyran. Unlike some reports in the literature, the gas phase 2-hydroxypiperidine experiences the herein called reverse anomeric effect, although the highly stabilizing n N → σ*C-O interaction in the axial isomer. Overall, steric effects should be taken into account when deciding for the normal or reverse anomeric effects as determinant factors of the stereochemical control of carbohydrate-like molecules.
      Graphical abstract image

      PubDate: 2017-09-19T19:38:50Z
       
  • 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
    • Abstract: Publication date: Available online 14 September 2017
      Source:Carbohydrate Research
      Author(s): 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. The strains studied in this work differ in the cell wall composition from the type strain of phylogenetically closely related species A. crystallopoietes which was reported to contain a teichoic acid and supposedly had a glycosyl 1-phosphate polymer.
      Graphical abstract image

      PubDate: 2017-09-19T19:38:50Z
       
  • Stereoselective sialylation with O-trifluoroacetylated thiosialosides:
           Hydrogen bonding involved'
    • Abstract: Publication date: Available online 8 September 2017
      Source:Carbohydrate Research
      Author(s): 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. The presence of O-TFA groups in a sialyl donor strongly affected the outcome of sialylation. Several sialyl donors studied showed promising results: yields of disaccharides can be as high as 86% as can be the stereoselectivities (α/β up to 15:1). The results obtained suggest that varying acyl O-protecting groups in sialyl donor may result in dramatic changes in the outcome of sialylation although further studies are required to dissect the influence of intermolecular hydrogen bonding and intramolecular substituent effects related to variations of electron-withdrawing properties of different acyl groups.
      Graphical abstract image

      PubDate: 2017-09-13T21:20:04Z
       
  • Synthesis of a trisaccharide repeating unit of the O-antigen from
           Burkholderia cenocepacia and its dimer
    • Abstract: Publication date: Available online 8 September 2017
      Source:Carbohydrate Research
      Author(s): 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. Title molecule 1 was prepared by glycosylation of 3-azidopropanol with 3 and subsequently global deprotection, whereas coupling reaction of 3 with a trisaccharide acceptor 21 containing an 2,3-O-position acetonide-modified rhamnose residue, followed by global deprotection, generated the dimer 2 in a convergent [3 + 3] manner.
      Graphical abstract image

      PubDate: 2017-09-13T21:20:04Z
       
 
 
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