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  • 301.
    Engström, Karin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Nyhlén, Jonas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Sandström, Anders G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Enantioselective Kinetic Resolution of p-Nitrophenyl 2-Phenylpropanoate by a Variant of Candida antarctica Lipase A Developed by Directed Evolution2010Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 132, nr 20, s. 7038-7042Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A variant of Candida antarctica lipase A (CalA) was developed for the hydrolysis of α-substituted p-nitrophenyl esters by directed evolution. The E values of this variant for 7 different esters was 45−276, which is a large improvement compared to 2−20 for the wild type. The broad substrate scope of this enzyme variant is of synthetic use, and hydrolysis of the tested substrates proceeded with an enantiomeric excess between 95−99%. A 30-fold increase in activity was also observed for most substrates. The developed enzyme variant shows (R)-selectivity, which is reversed compared to the wild type that is (S)-selective for most substrates.

  • 302.
    Engström, Karin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Shakeri, Mozaffar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Dynamic Kinetic Resolution of β-Amino Esters by a Heterogeneous System of a Palladium Nanocatalyst and Candida antarctica Lipase A2011Ingår i: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, nr 10, s. 1827-1830Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A dynamic kinetic resolution (DKR) of β-amino esters have been developed by the use of a heterogeneous racemization catalyst and an immobilized enzyme that accepts aromatic, heteroaromatic and aliphatic substrates. The reaction conditions were optimized to yield an efficient catalytic system without by-product formation. The products are obtained in 96–99 % ee and high yields

  • 303.
    Engström, Karin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Vallin, Michaela
    Hult, Karl
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Kinetic resolution of diarylmethanols using a mutated variant of lipase CALB2012Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 68, nr 37, s. 7613-7618Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An enzymatic kinetic resolution of diarylmethanols via acylation has been developed. This was achieved by the use of a mutated variant of CALB that accepts larger substrates compared to the wild type. By the use of diarylmethanols with two differently sized aryl groups, enantioselective transformations were achieved. A larger size-difference led to a higher enantioselectivity. In addition, substrates with electronically different aryl groups, such as phenyl and pyridyl, also gave an enantioselective reaction. The highest E value was observed with a substrate where steric and electronic effects were combined.

  • 304.
    Engström, Karin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Vallin, Michaela
    Syrén, Per-Olof
    Hult, Karl
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Mutated variant of Candida antarctica lipase B in (S)-selective dynamickinetic resolution of secondary alcohols2011Ingår i: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 9, nr 1, s. 81-82Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An (S)-selective dynamic kinetic resolution of secondaryalcohols, employing a mutated variant of Candida antarcticalipase B (CalB) gave products in 84–88% yield and in 90–97%ee.

  • 305.
    Engström, Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Carbohydrate dynamics and interactions studied by NMR spectroscopy2013Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The combination of NMR spectroscopy and molecular dynamics (MD) simulations are powerful tools in the studying of bioorganic molecules in solution. In this thesis two such studies are presented with focus on the NMR aspect. The caffeine association to sugars (D-glucose and sucrose) was investigated by NMR titrations and NOESY experiments in paper I. The observations from the NMR experiments confirmed MD simulations showing that the binding occurs by a face-to-face interaction between the aromatic surface of the caffeine and axial protons of the sugar ring. Different sugar molecules and residues have different preferences regarding which side of the sugar ring that are involved in the binding. The sucrose residues bind with only one ring face each whereas β-D-glucopyranose has two sides of similar binding probability and the α-D-glucopyranose has something in between. The MD simulations showed that the driving force of the binding is partly driven by hydration effects that favor the enthalpy of the system. A new approach to calculate NMR relaxation parameters (that is dependent on molecular motions) from computational simulations is presented in paper II. Each sugar residue is assumed to be a rigid unit connected by flexible joints in the approach, thus the name diffusive chain model (DCM). The simplified model together with a stochastic simulation approach lowers the computational cost which makes it possible to acquire long enough trajectories to the calculations of spin relaxation parameters. Two case studies with slightly different methodologies are presented. In one of them, spin relaxation parameters are reproduced for the human milk oligosaccharide LNF-1 in a feasible way by the use of Brownian dynamics.

  • 306.
    Engström, Olof
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Mobarak, Hani
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Ståhle, Jonas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Conformational Dynamics and Exchange Kinetics of N-Formyl and N-Acetyl Groups Substituting 3-Amino-3,6-dideoxy-alpha-D-galactopyranose, a Sugar Found in Bacterial O-Antigen Polysaccharides2017Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 121, nr 41, s. 9487-9497Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three dimensional shape and conformation of. carbohydrates are important factors in molecular recognition events and the N-acetyl group of a monosaccharide residue can function as a conformational gatekeeper whereby it influences the overall shape of the oligosaccharide. NMR spectroscopy and quantum mechanics (QM) calculations are used herein to investigate both the conformational preferences and the dynamic behavior of N-acetyl and N-formyl substituents of 3-amino-3,6-dideoxy-alpha-D-galactopyranose, a sugar and substitution pattern found in bacterial O-antigen polysaccharides. QM calculations suggest that the amide oxygen can be involved in hydrogen bonding with the axial OH4 group primarily but also with the equatorial OH2 group. However, an NMR J coupling analysis indicates that the 01 torsion angle, adjacent to the sugar ring, prefers an ap conformation where conformations <180 degrees also are accessible, but does not allow for intramolecular hydrogen bonding. In the formyl-substituted compound (4)J(HH) coupling constants to the exo-cyclic group were detected and analyzed. A van't Hoff analysis revealed that the trans conformation at the amide bond is favored by Delta G degrees approximate to - 0.8 kcal.mol(-1) in the formyl-containing compound and with Delta G degrees approximate to -2.5 kcal.mol(-1) when the N-acetyl group is the substituent. In both cases the enthalpic term dominates to the free energy, irrespective of water or DMSO as solvent, with only a small contribution from the entropic term. The cis-trans isomerization of the theta(2) torsion angle, centered at the amide bond, was also investigated by employing H-1 NMR line shape analysis and C-13 NMR saturation transfer experiments. The extracted transition rate constants were utilized to calculate transition energy barriers that were found to be about 20 kcal.mol(-1) in both DMSO-d(6) and D2O. Enthalpy had a higher contribution to the energy barriers in DMSO-d(6) compared to in D2O, where entropy compensated for the loss of enthalpy.

  • 307.
    Erbing, Elis
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Selective C-H Iodination of Benzamides and Weinreb Amides through Iridium and Acid CatalysisManuskript (preprint) (Övrigt vetenskapligt)
  • 308.
    Ericsson, Daniel J.
    et al.
    1Department of Cell and Molecular Biology, Uppsala University, Biomedical Center.
    Kasrayan, Alex
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Johansson, Patrik
    1Department of Cell and Molecular Biology, Uppsala University, Biomedical Center.
    Bergfors, Terese
    1Department of Cell and Molecular Biology, Uppsala University, Biomedical Center.
    Sandström, Anders G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Mowbray, Sherry L.
    Department of Molecular Biology, Swedish University of Agricultural Sciences, Biomedical Center.
    X-Ray structure of Candida antarctica lipase A shows a novel lid structure and a likely mode of interfacial activation2008Ingår i: Journal of Molecular Biology, ISSN 0022-2836, Vol. 376, nr 1, s. 109-119Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In nature, lipases (EC 3.1.1.3) catalyze the hydrolysis of triglycerides to form glycerol and fatty acids. Under the appropriate conditions, the reaction is reversible, and so biotechnological applications commonly make use of their capacity for esterification as well as for hydrolysis of a wide variety of compounds. In the present paper, we report the X-ray structure of lipase A from Candida antarctica, solved by single isomorphous replacement with anomalous scattering, and refined to 2.2-Å resolution. The structure is the first from a novel family of lipases. Contrary to previous predictions, the fold includes a well-defined lid as well as a classic α/β hydrolase domain. The catalytic triad is identified as Ser184, Asp334 and His366, which follow the sequential order considered to be characteristic of lipases; the serine lies within a typical nucleophilic elbow. Computer docking studies, as well as comparisons to related structures, place the carboxylate group of a fatty acid product near the serine nucleophile, with the long lipid tail closely following the path through the lid that is marked by a fortuitously bound molecule of polyethylene glycol. For an ester substrate to bind in an equivalent fashion, loop movements near Phe431 will be required, suggesting the primary focus of the conformational changes required for interfacial activation. Such movements will provide virtually unlimited access to solvent for the alcohol moiety of an ester substrate. The structure thus provides a basis for understanding the enzyme's preference for acyl moieties with long, straight tails, and for its highly promiscuous acceptance of widely different alcohol and amine moieties. An unconventional oxyanion hole is observed in the present structure, although the situation may change during interfacial activation

  • 309.
    Eriksson, Kristofer
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Gothelid, Emmanuelle
    Puglia, Carla
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Oscarsson, Sven
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Performance of a biomimetic oxidation catalyst immobilized on silica particles2013Ingår i: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 303, s. 16-21Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A biomimetic oxidation catalyst, cobalt porphyrin with thiol linkers, was chemically conjugated to silica particles and utilized in the oxidation of hydroquinone to benzoquinone. The cobalt porphyrin/silica particle catalyst was characterized with Inductively Coupled Plasma (ICP) and X-ray Photoelectron Spectroscopy (XPS). The catalytic performance of the cobalt porphyrin molecules was compared to previous results for the same catalyst grafted to a gold surface and on silicon wafers. The measured catalytic activity, after background correction, was 100 times higher than that of its homogeneous counterpart, 10 times higher than that on a silicon wafer, and almost the same as that on a gold surface. The turnover frequency rates after 400 h are still comparable with initial rates reported for homogeneous porphyrins and salophens, whereas the use of particles as support increases the active surface area, which removes the limitations for scale-up associated with the previously used silicon wafers and gold surfaces.

  • 310. Eriksson, Kristofer L. E.
    et al.
    Chow, Winnie W. Y.
    Puglia, Carla
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Göthelid, Emmanuelle
    Oscarsson, Sven
    Performance of a biomimetic oxidation catalyst immobilized on silicon wafers: comparison with its gold congener2010Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, nr 21, s. 16349-16354Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With the aim of extending the usefulness of an existing biomimetic catalytic system, cobalt porphyrin catalytic units with thiol linkers were heterogenized via chemical grafting to silicon wafers and utilized for the catalytic oxidation of hydroquinone to p-benzoquinone. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to analyze the morphology and composition of the heterogeneous catalyst. The results of the catalytic oxidation of hydroquinone obtained with porphyrins grafted on silicon were compared with those obtained earlier with the same catalyst in homogeneous phase and immobilized on gold. It was found that the catalysis could run over 400 h, without showing any sign of deactivation. The measured catalytic activity is at least 10 times higher than that measured under homogeneous conditions, but also 10 times lower than that observed with the catalytic unit immobilized on gold. The reasons of this discrepancy are discussed in term of substrate influence and overlayer organization. The silicon-immobilized catalyst has potential as an advanced functional material with applications in oxidative heterogeneous catalysis of organic reactions, as it combines long-term relatively high activity with low cost.

  • 311.
    Eriksson, Kristofer
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Verho, Oscar
    Nyholm, Leif
    Oscarsson, Sven
    Bäckvall, Jan Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Electrochemical Preparation of Dispersed Gold Nanoparticles Supported in the Pores of Siliceous Mesocellular Foam: An Efficient Catalyst for Cycloisomerization of 4-Alkynoic Acids to LactonesManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    A versatile approach for the production of dispersed thiol-stabilized gold nanoparticles in the pores of siliceous mesocellular foam (MCF) is described and the thiol-stabilized gold nanoparticles were found to catalyze the cyclization of 4-pentynoic acids to lactones. The reported method is based on an electrochemical oxidation of a gold substrate generating oxidative Au(III) species which give rise to a surface-confined redox reaction yielding MCF supported Au(I)-thiolates. By reducing the MCF-S-Au(I) complex with sodium borohydride thiol-stabilized gold nanoparticles were obtained which were characterized with Transmission Electron Microscopy (TEM). The nanoparticles were found to be in the size of 1-8 nm. Inductive Coupled Plasma (ICP) analysis indicated an Au loading of 3 % (w/w) on the MCF. Further 0.5 mol% of the MCF-S-Au(0) solids were used to catalyze the cyclization reaction of 4-alkynoic acid under mild conditions with high selectivity (> 99%).

  • 312.
    Eriksson, Kristofer
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Verho, Oscar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Nyholm, Leif
    Oscarsson, Sven
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Dispersed Gold Nanoparticles Supported in the Pores of Siliceous Mesocellular Foam: A Catalyst for Cycloisomerization of Alkynoic Acids to gamma-Alkylidene Lactones2015Ingår i: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, nr 10, s. 2250-2255Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A versatile approach for the production of dispersed thiol-stabilized gold nanoparticles in the pores of siliceous mesocellular foam (MCF) is described. The reported method is based on an electrochemical oxidation of a gold surface generating oxidative Au-III species, which give rise to a surface-confined redox reaction yielding MCF-supported Au-I thiolates. By reducing the corresponding Au-I-S-MCF species with sodium borohydride, thiol-stabilized gold nanoparticles in the size range of 1-8 nm were obtained as determined by transmission electron microscopy. Elemental analysis indicated an Au loading of 3% (w/w) on the MCF. The surface-confined Au nanoparticles were used to catalyze the cycloisomerization of alkynoic acids to the corresponding -alkylidene lactones in high efficiency and complete 5-exo-dig selectivity under mild reaction conditions.

  • 313.
    Eriksson, Lars
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Widmalm, Göran
    Institutionen för organisk kemi.
    Methyl 3-O-alpha-D-mannopyranosyl beta-D-glucopyranoside tetrahydrate2008Ingår i: Acta Crystallographica Section E, ISSN 1600-5368, Vol. E64, nr 8, s. o1639-o1640Artikel i tidskrift (Refereegranskat)
  • 314.
    Eriksson, Lars
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Methyl 3-O-alpha-L-fucopyranosyl alpha-D-galactopyranoside: a synchrotron study2012Ingår i: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 68, s. o528-U1770Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The title compound, C13H24O10 is the methyl glycoside of a structural element alpha-L-Fucp-(1 -> 3)-alpha-D-Galp making up two thirds of the repeating unit in the capsular polysaccharide of Klebsiella K63. The conformation of the title compound is described by the glycosidic torsion angles phi(H) = 55 (1)degrees and psi H = -24 (1)degrees. The hydroxymethyl group in the galactose residue is present in the gauche-trans conformation. In the crystal, O-H center dot center dot center dot O hydrogen bonds connect the disaccharide units into chains along the a-axis direction and further hydrogen bonds cross-link the chains.

  • 315.
    Eriksson, Lars
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Methyl 3-O-α-l-fucopyranosyl β-d-glucopyranoside tetrahydrate2012Ingår i: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 68, s. o3180-o3181Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The title compound, C13H24O10·4H2O, is the methyl glycoside of a disaccharide structural element present in the backbone of the capsular polysaccharide from Klebsiella K1, which contains only three sugars and a substituent in the polysaccharide repeating unit. The conformation of the title disaccharide is described by the glycosidic torsion angles ϕH = 51.1 (1)° and ψH = 25.8 (1)°. In the crystal, a number of O—HO hydrogen bonds link the methyl glycoside and water mol­ecules, forming a three-dimensional network. One water mol­ecule is disordered over two positions with occupancies of 0.748 (4) and 0.252 (4).

  • 316. Eriksson, Lars
    et al.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Methyl α-l-rhamnosyl-(1→2)[α-l-rhamnosyl-(1→3)]-α-l-rhamnoside penta­hydrate: synchrotron study2012Ingår i: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 68, nr 7, s. o2221-o2222Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The title hydrate, C19H34O13·5H2O, contains a vicinally disubstituted tris­accharide in which the two terminal rhamnosyl sugar groups are positioned adjacent to each other. The conformation of the tris­accharide is described by the glycosidic torsion angles ϕ2 = 48 (1)°, ψ2 = −29 (1)°, ϕ3 = 44 (1)° and ψ3 = 4 (1)°, whereas the ψ2 torsion angle represents a conformation from the major state in solution, the ψ3 torsion angle conformation may have been caught near a potential energy saddle-point when compared to its solution structure, in which at least two but probably three conformational states are populated. Extensive inter­molecular O—HO hydrogen bonding is present in the crystal and a water-containing channel is formed along the b-axis direction.

  • 317. Ertem, Mehmed Z.
    et al.
    Cramer, Christopher J.
    Himo, Fahmi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Siegbahn, Per E. M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    N-O bond cleavage mechanism(s) in nitrous oxide reductase2012Ingår i: Journal of Biological Inorganic Chemistry, ISSN 0949-8257, E-ISSN 1432-1327, Vol. 17, nr 5, s. 687-698Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Quantum chemical calculations of active-site models of nitrous oxide reductase (N2OR) have been undertaken to elucidate the mechanism of N-O bond cleavage mediated by the supported tetranuclear Cu4S core (Cu-Z) found in the enzymatic active site. Using either a minimal model previously employed by Gorelsky et al. (J. Am. Chem. Soc. 128:278-290, 2006) or a more extended model including key residue side chains in the active-site second shell, we found two distinct mechanisms. In the first model, N2O binds to the fully reduced Cu-Z in a bent mu-(1,3)-O,N bridging fashion between the Cu-I and Cu-IV centers and subsequently extrudes N-2 while generating the corresponding bridged mu-oxo species. In the second model, substrate N2O binds loosely to one of the coppers of Cu-Z in a terminal fashion, i.e., using only the oxygen atom; loss of N-2 generates the same mu-oxo copper core. The free energies of activation predicted for these two alternative pathways are sufficiently close to one another that theory does not provide decisive support for one over the other, posing an interesting problem with respect to experiments that might be designed to distinguish between the two. Effects of nearby residues and active-site water molecules are also explored.

  • 318.
    Fawzy Abdel-Magied, Ahmed
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi. Nuclear Materials Authority, Egypt.
    Solid phase extraction of uranium from phosphoric acid: kinetic and thermodynamic study2017Ingår i: Radiochimica Acta, ISSN 0033-8230, E-ISSN 2193-3405, Vol. 105, nr 10, s. 813-820Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is a high interest to develop suitable solid phase extractants for uranium separation from aqueous solutions in order to reduce cost and enhance the efficiency. This paper describes solid phase extraction of uranium(VI) from aqueous phosphoric acid solution using MCM-41 based D2HEPA-TOPO organophosphorous extractants. The mixture of D2HEPA (di-2-ethyl-hexylphosphoric acid) and TOPO (tri-n-octylphosphine oxide) was impregnated into the pores of MCM-41 and the synthesized sorbent was fully characterized. The influences of different factors such as synergistic mixture ratio, phosphoric acid concentration, mixing time and temperature were investigated. The results showed that 90% of uranium(VI) extraction can be achieved within 5 min, using D2HEPATOPO@MCM-41 (mass ratio 2: 1 w/w) from 1 M phosphoric acid containing 64 ppm of uranium at room temperature. High adsorption capacity of uranium(VI) have been achieved at the mentioned conditions. The rate constant for the chemical adsorption of uranium(VI) was 0.988 g mg. 1 min. 1 calculated by the pseudo-second order rate equation. The obtained thermodynamics parameters showed that uranium(VI) adsorption from H-3 PO4 is an exothermic and spontaneous process.

  • 319.
    Fontana, Carolina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    NMR spectroscopy in structural and conformational analysis of bacterial polysaccharides2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Carbohydrates constitute one of the three major classes of biomolecules found in all living cells and, unlike nucleic acids and proteins, their polymeric structures are not based on a template. The structural diversity of these molecules confers them an enormous capacity to encode information in biological systems, acting as efficient mediators in the interaction of the cell with the environment. In order to understand the roles of glycans in biological processes it is of key importance to have a detailed understanding of their structures and conformational preferences, and NMR spectroscopy is one of most powerful techniques for the study of these molecules in solution.

    This thesis is focused on the structural and conformational analysis of lipopolysaccharides from Gram-negative bacteria. In the first two projects (Chapter 2 and 3) the structural analyses of the biological repeating units of the O-antigen polysaccharides from E. coli O174ab and O115 are described; in both cases a combination of NMR spectroscopy and gas chromatography techniques were used. Special emphasis was made in the characterization of the O-acetylation patterns observed in the native O-antigen polysaccharide from E. coli O115. Chapter 4 describes the development of a new methodology for the determination of the absolute configuration of monosaccharide components of glycans. This methodology was used in the structural elucidation of the O-antigen PS of E. coli O155 (Chapter 5) that was carried out in a semi-automated manner using the program CASPER and unassigned NMR data. The conformational preferences of O-antigen PS of E. coli O5ac and O5ab are analyzed in Chapter 6, using a combination of NMR spectroscopy and molecular modeling methods. In Chapter 7 the structural analysis is focused on the core region of the LPS, and the structures of the deacylated lipooligosaccharides of three rough mutants of B. melitesis are reported. In several of the aforementioned chapters, the biosynthetic aspects behind the assembly of the respective PSs were examined on the bases of genetic information available in the NCBI and ECODAB databases.  Finally, in Chapter 8, different NMR pulse sequences available for the study of proteins and nucleic acids were evaluated and optimized for the structural analysis of 13C uniformly-labeled oligo- and polysaccharides.

  • 320.
    Fontana, Carolina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural studies of glycans by NMR spectroscopy2012Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 321.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Conde-Alvarez, Raquel
    Ståhle, Jonas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Holst, Otto
    Iriarte, Maite
    Zhao, Yun
    Arce-Gorvel, Vilma
    Hanniffy, Sean
    Gorvel, Jean-Pierre
    Moriyon, Ignacio
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural Studies of Lipopolysaccharide-defective Mutants from Brucella melitensis Identify a Core Oligosaccharide Critical in Virulence2016Ingår i: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 291, nr 14, s. 7727-7741Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The structures of the lipooligosaccharides from Brucella melitensis mutants affected in the WbkD and ManB(core) proteins have been fully characterized using NMR spectroscopy. The results revealed that disruption of wbkD gives rise to a rough lipopolysaccharide (R-LPS) with a complete core structure (beta-D-Glcp-(1 -> 4)-alpha-Kdop-(2 -> 4)[beta-D-GlcpN-(1 -> 6)-beta-D-GlcpN-(1 -> 4)[beta-D-GlcpN-(1 -> 6)]-beta-D-GlcpN-(1 -> 3)-alpha-D-Manp-(1 -> 5)]-alpha-Kdop-(2 -> 6)-beta-D-GlcpN3N4P-(1 -> 6)-alpha-D-GlcpN3N1P), in addition to components lacking one of the terminal beta-D-GlcpN and/or the beta-D-Glcp residues (48 and 17%, respectively). These structures were identical to those of the R-LPS from B. melitensis EP, a strain simultaneously expressing both smooth and R-LPS, also studied herein. In contrast, disruption of man-B-core gives rise to a deep-rough pentasaccharide core (beta-D-Glcp-(1 -> 4)-alpha-Kdop-(2 -> 4)-alpha-Kdop-(2 -> 6)-beta-D-GlcpN3N4P-(1 -> 6)-alpha-D-GlcpN3N1P) as the major component (63%), as well as a minor tetrasaccharide component lacking the terminal beta-D-Glcp residue (37%). These results are in agreement with the predicted functions of the WbkD (glycosyltransferase involved in the biosynthesis of the O-antigen) and ManB(core) proteins (phosphomannomutase involved in the biosynthesis of a mannosyl precursor needed for the biosynthesis of the core and O-antigen). We also report that deletion of B. melitensis wadC removes the core oligosaccharide branch not linked to the O-antigen causing an increase in overall negative charge of the remaining LPS inner section. This is in agreement with the mannosyltransferase role predicted for WadC and the lack of GlcpN residues in the defective core oligosaccharide. Despite carrying the O-antigen essential in B. melitensis virulence, the core deficiency in the wadC mutant structure resulted in a more efficient detection by innate immunity and attenuation, proving the role of the beta-D-GlcpN-(1 -> 6)-beta-D-GlcpN-(1 -> 4)[beta-D-GlcpN-(1 -> 6)]-beta-D-GlcpN-(1 -> 3)-alpha-D-Manp-(1 -> 5) structure in virulence.

  • 322.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Holst, Otto
    Moriyón, Ignacio
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural studies of the rough lipopolysaccharides of Brucella melitensis mutants affected in the biosynthesis of the core and O-antigen polysaccharideManuskript (preprint) (Övrigt vetenskapligt)
  • 323.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Lundborg, Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Weintraub, Andrej
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural studies and biosynthetic aspects of the o antigen polysaccharide from Escherichia coli o1742012Ingår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 354, s. 102-105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The structure of the repeating unit of the O-antigenic polysaccharide (PS) from Escherichia coli O174 has been determined. Component analysis together with H-1 and C-13 NMR spectroscopy experiments were employed to elucidate the structure. Inter-residue correlations were determined by H-1, C-13-heteronuclear multiple-bond correlation and H-1, H-1-NOESY experiments. The PS is composed of tetrasaccharide repeating units with the following structure: -> 4)-beta-D-GlcpA-(1 -> 3)-beta-D-Galp-(1 -> 3)-beta-D-GalpNAc-(1 -> vertical bar beta-D-GlcpNAc-(1 -> 2) Cross-peaks of low intensity were present in the NMR spectra consistent with a beta-D-GlcpNAc-(1 -> 2)-beta-D-GlcpA(1 -> structural element at the terminal part of the polysaccharide, which on average is composed of similar to 15 repeating units. Consequently the biological repeating unit has a 3-substituted N-acetyl-D-galactosamine residue at its reducing end.

  • 324.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Ramström, Kristoffer
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Weintraub, Andrej
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural studies of the O-antigen polysaccharide from Escherichia coli O115 and biosynthetic aspects thereof2013Ingår i: Glycobiology, ISSN 0959-6658, E-ISSN 1460-2423, Vol. 23, nr 3, s. 354-362Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The structure of the O-antigen polysaccharide (PS) of Escherichia coliO115 has been investigated using a combination of component analysis and 1D and 2D nuclear magnetic resonance (NMR) spectroscopy experiments. The repeating unit of the O-antigen was elucidated using the O-deacetylated PS and has the following branched pentasaccharide structure: →3)[β-L-Rhap-(1 → 4)]-β-D-GlcpNAc-(1 → 4)-α-D-GalpA-(1 → 3)-α-D-Manp-(1 → 3)-β-D-GlcpNAc-(1→. Cross-peaks of low intensity, corresponding to a β-L-Rhap-(1 → 4)-β-D-GlcpNAc-(1→ structural element, were present in the NMR spectra and attributed to the terminal part of the PS; this information defines the biological repeating unit of the O-antigen by having a 3-substituted N-acetyl-D-glucosamine (GlcNAc) residue at its reducing end. Analysis of the NMR spectra of the native PS revealed O-acetyl groups distributed over different positions of theL-Rhap residue (∼0.70 per repeating unit) as well as at O-2 and O-3 of the D-GalpA residue (∼0.03 and ∼0.25 per repeating unit, respectively), which is in agreement with the presence of two acetyltransferases previously identified in the O-antigen gene cluster (Wang Q, Ruan X, Wei D, Hu Z, Wu L, Yu T, Feng L, Wang L. 2010. Mol Cell Probes. 24:286–290.). In addition, the four glycosyltransferases initially identified in the O-antigen gene cluster of E. coli O115 were analyzed using BLAST, and the function of two of them predicted on the basis of similarities with glycosyltransferases from Shigella dysenteriae type 5 and 12, as well as E. coli O58 and O152.

  • 325. Foster, R. A.
    et al.
    Carlin, N. I. A.
    Majcher, M.
    Tabor, H.
    Ng, L.-K.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural elucidation of the O-antigen of the Shigella flexneri provisionalserotype 88-893: structural and serological similarities with S. flexneri provisional serotype Y394 (1c)2011Ingår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 346, nr 6, s. 872-876Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The structure of the repeating unit of the O-antigen polysaccharide from Shigella flexneri provisional serotype 88-893 has been determined. 1H and 13C NMR spectroscopy as well as 2D NMR experiments were employed to elucidate the structure. The carbohydrate part of the hexasaccharide repeating unit is identical to the previously elucidated structure of the O-polysaccharide from S. flexneri prov. serotype Y394. The O-antigen of S. flexneri prov. serotype 88-893 carries 0.7 mol O-acetyl group per repeating unit located at O-2 of the 3-substituted rhamnosyl residue, as identified by H2BC and BS-CT-HMBC NMR experiments. The O-antigen polysaccharide is composed of hexasaccharide repeating units with the following structure: →2)-α-l-Rhap-(1→2)-α-l-Rhap-(1→3)-α-l-Rhap2Ac-(1→3)[α-d-Glcp-(1→2)-α-d-Glcp-(1→4)]-β-d-GlcpNAc-(1→. Serological studies showed that type antigens for the two provisional serotypes are identical; in addition 88-893 expresses S. flexneri group factor 6 antigen. We propose that provisional serotypes Y394 and 88-893 be designated as two new serotypes 7a and 7b, respectively, in the S. flexneri typing scheme.

  • 326. Fourniere, Viviane
    et al.
    Skantz, Linnea
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Sajtos, Ferenc
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Oscarson, Stefan
    Lahmann, Martina
    Synthesis of the Lewis b pentasaccharide and a HSA-conjugate thereof2010Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 66, nr 39, s. 7850-7855Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Helicobacter pylori, a gastric pathogen, binds to various blood group antigens, including the Lewis types, present in the gastric tissue and a relation between the presentation of the ligands and the overall strength of binding has been assumed. Synthetic Lewis b tetra- and hexasaccharide conjugates are available but not the analogous pentasaccharide. An efficient synthesis of the amino spacer equipped Lewis b pentasaccharide, 3-aminopropyl alpha-L-fucopyranosyl-(1 -> 2)-beta-D-galactopyranosyl-(1 3)-[alpha-L-fucopyranosyl-(1 -> 4)]-2-acetamido-2-deoxy-beta-D-glucopyranosyl-(1 -> 3)-beta-D-galactopyranoside, is presented to enable further investigation of the carbohydrate recognition process of H. pylori.

  • 327.
    Fournière, Viviane
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Cumpstey, Ian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Synthesis of non-glycosidically linked selenoether pseudodisaccharides2010Ingår i: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 51, nr 16, s. 2127-2129Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Non-glycosidically linked disaccharide mimetics with a selenoether functionality linking the two monosaccharide residues have been synthesised. Protected Glc(Se3–3)Glc, Glc(Se3–6)Glc and Glc(Se3–6)Man structures were obtained. Selenium was introduced by displacement of carbohydrate sulfonates with a selenobenzoate anion. Conversion into diselenides by methanolysis of the benzoate and aerial oxidation was followed by reduction of the diselenides to selenolates, and in situ displacement of a second carbohydrate sulfonate in an SN2 reaction to give selenoethers. Glc(Se3–3)Glc and Glc(Se3–6)Glc were also obtained in deprotected form.

  • 328. Francois, Camille
    et al.
    Pourchet, Sylvie
    Boni, Gilles
    Fontaine, Stephane
    Gaillard, Yves
    Placet, Vincent
    Galkin, Maxim V.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Orebom, Alexander
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Samec, Joseph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Plasseraud, Laurent
    Diglycidylether of iso-eugenol: a suitable lignin-derived synthon for epoxy thermoset applications2016Ingår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, nr 73, s. 68732-68738Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel lignin-based synthon, diglycidylether of iso-eugenol (DGE-isoEu) is used as a prepolymer for the preparation of thermosetting resins. DGE-isoEu is synthesized in a two-step procedure with a satisfactory yield from bio-based iso-eugenol (isoEu, 2-methoxy-4-(1-propenyl)phenol) catalytically fragmented from lignin in an organosolv process. DGE-isoEu was fully characterized by NMR, MS and FTIR. Curing of the DGE-isoEu monomer has then been investigated in the presence of several carboxylic acid derivatives hardeners. The thermal and mechanical properties of each material were recorded showing, in particular, a high T-g and instantaneous modulus values in the range of 78-120 degrees C and 4.6-5.5 GPa, respectively. The lignin derived new materials give very attractive thermo-mechanical properties comparable to that of common BPA-containing epoxy resins.

  • 329.
    Fransson, Ann-Britt L.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Borén, Linnéa
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Pàmies, Oscar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Kinetic Resolution and Chemoenzymatic Dynamic Kinetic Resolution of Functionalized γ-Hydroxy Amides2005Ingår i: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 70, nr 7, s. 2582-2587Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An efficient kinetic resolution of racemic gamma-hydroxy amides 1 was performed via Pseudomas cepacia lipase (PS-C)-catalyzed transesterification. The enzyme PS-C tolerates both variation in the chain length and different functionalities giving good to high enantioselectivity (E values of up to > 250). The combination of enzymatic kinetic resolution with a ruthenium-catalyzed racemization led to a dynamic kinetic resolution. The use of 2,4-dimethyl-3-pentanol as a hydrogen source to suppress ketone formation in the dynamic kinetic resolution yields the corresponding acetates in good yield and good to high enantioselectivity (ee's up to 98%). The synthetic utility of this procedure was illustrated by the practical synthesis of the versatile intermediate gamma-lactone (R)-5-methyltetrahydrofuran-2-one.

  • 330.
    Fransson, Ann-Britt L.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Leijondahl, Karin
    Bäckvall, Jan-Erling
    Highly Efficient Ru-catalyzed Transfer Hydrogenation/Hydrogenation Procedure for 1,3-Cycloalkandiols using Controlled Microwave HeatingManuskript (Övrigt vetenskapligt)
  • 331.
    Fransson, Ann-Britt L.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Xu, Yongmei
    Leijondahl, Karin
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Enzymatic Resolution, Desymmetrization and Dynamic Kinetic Asym-metric Transformation of 1,3-Cycloalkanediols2006Ingår i: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 71, nr 17, s. 6309-6316Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An efficient desymmetrization of cis-1,3-cyclohexanediol to (1S,3R)-3-(acetoxy)-1-cyclohexanol ((R,S)-2a) was performed via Candida antarctica lipase B (CALB)-catalyzed transesterification, in high yield (up to 93%) and excellent enantioselectivity (ee's up to >99.5%). (R,R)-Diacetate ((R,R)-3a) was obtained in a DYKAT process at room temperature from (1S,3R)-3-acetoxy-1-cyclohexanol ((R,S)-2a), in a high trans/cis ratio (91:9) and in excellent enantioselectivity of >99%. Metal- and enzyme-catalyzed dynamic transformation of cis/trans-1,3-cyclohexanediol using PS-C gave a high diastereoselectivity for cis-diacetate (cis/trans = 97:3). The (1R,3S)-3-acetoxy-1-cyclohexanol (ent-(R,S)-2a) was obtained from cis-diacetate by CALB-catalyzed hydrolysis in an excellent yield (97%) and selectivity (>99% ee). By deuterium labeling it was shown that intramolecular acyl migration does not occur in the transformation of cis-monoacetate to the cis-diacetate.

  • 332. Fransson, Ann-Britt
    et al.
    Xu, Yongmei
    Leijondahl, Karin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-Erling
    Enzymatic resolution, desymmetrization and dynamic kinetic asymmetric transformation of 1,3-cycloalkanediols2006Ingår i: Journal of organic chemistry, ISSN 0022-3263, Vol. 71, nr 17, s. 6309-6316Artikel i tidskrift (Refereegranskat)
  • 333.
    Franzén, Johan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Palladium-Catalyzed Carbocyclizations of Allenes with Unsaturated Hydrocarbons2004Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Palladium-catalyzed reactions of unsaturated hydrocarbons are important processes in organic chemistry especially for the generation of ring systems. This thesis describes the development and mechanistic studies of carbocyclization reactions of allenes with olefins, allyls or 1,3-dienes catalyzed by palladium(0)- and palladium(II)-complexes. These reactions generally exhibit high stereo- and regioselectivity and give rise to stereodefined [n,3,0] bicyclic systems (n=3,4,5,6) in good to excellent yields. The mechanisms for these reactions were investigated with special attention directed to the intramolecular reaction of (π-allyl)palladium(II)-complexes and (π-1,3-diene)palladium(II)-complexes with allenes. It was demonstrated that the carbon-carbon bond formation occurred by nucleophilic attack of the middle carbon atom of the allene on the face of the allyl or 1,3-diene opposite to that of the palladium atom. Further, two new types of oxidative palladium(II)-catalyzed reactions between allenes and olefins or 1,3-dienes have been developed. These cyclizations constitute a new type of carbon-carbon bond forming reaction and there are support for a palladium(II)-catalyzed C-H activation at the allenic moiety rendering a vinylidienepalladium-intermediate followed by carbon-carbon bond formation via insertion of the olefin or 1,3-diene.

  • 334.
    Franzén, Johan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Carbon-Carbon bond formation in Palladium(II)-Catalyzed Allylic Oxidation: A Novel Oxidative Carbozyclization of Allene-Substituted Olefins2003Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 125, nr 20, s. 6056-6057Artikel i tidskrift (Refereegranskat)
  • 335.
    Franzén, Johan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Löfstedt, Joakim
    Dorange, Ismet
    Bäckvall, Jan E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Allenes as Carbon Nucleophiles in Palladium-Catalyzed Reactions: Observation of anti Attack of Allenes on (p-Allyl)Palladium Complexes2002Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 124, nr 38, s. 11246-11247Artikel i tidskrift (Refereegranskat)
  • 336.
    Franzén, Johan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Löfstedt, Joakim
    Falk, Jennica
    Bäckvall, Jan-E
    Stereoselective Palladium-Catalyzed Carbocyclization of Allenic Allylic Carboxylates.2003Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 125, nr 46, s. 14140-14148Artikel i tidskrift (Refereegranskat)
  • 337. François, Camille
    et al.
    Pourchet, Sylvie
    Boni, Gilles
    Rautiainen, Sari
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Samec, Joseph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Fournier, Lucie
    Robert, Carine
    Thomas, Christophe M.
    Fontaine, Stephane
    Gaillard, Yves
    Placet, Vincent
    Plasseraud, Laurent
    Design and synthesis of biobased epoxy thermosets from biorenewable resources2017Ingår i: Comptes rendus. Chimie, ISSN 1631-0748, E-ISSN 1878-1543, Vol. 20, nr 11-12, s. 1006-1016Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Biobased diepoxy synthons derived from isoeugenol, eugenol or resorcinol (DGE-isoEu, DGE-Eu and DGER, respectively) have been used as epoxy monomers in replacement of the diglycidyl ether of bisphenol A (DGEBA). Their curing with six different biobased anhydride hardeners leads to fully biobased epoxy thermosets. These materials exhibit interesting thermal and mechanical properties comparable to those obtained with conventional petrosourced DGEBA-based epoxy resins cured in similar conditions. In particular, a high T-g in the range of 90-130 degrees C and instantaneous moduli higher than 4.3 GPa have been recorded. These good performances are very encouraging, making these new fully biobased epoxy thermosets compatible with the usual structural application of epoxy materials.

  • 338.
    Frigell, Jens
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Towards Carbasugar-Based Mimics of Mycobacerial Arabinogalactan2008Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 339.
    Frigell, Jens
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Cumpstey, Ian
    Carbasugar analogues of galactofuranose: α-O-linked derivativesManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Using an indirect method, we have synthesised α-linked carbasugar analogues of galactofuranosides for the first time. Opening of a β-talo configured carbasugar 1,2-epoxide by alcohol nucleophiles under Lewis acidic conditions proceeded with very good regioselectivity to give α-talo configured C-1-substituted ethers with OH-2 free. Inversion of configuration at OH-2 by an oxidation–reduction sequence gave the α-galacto configured carbahexofuranose C-1 ethers. A carbadisaccharide corresponding to the Galf(α1→3)Manp substructure from Apodus deciduus galactomannan was synthesised to exemplify the method.

  • 340.
    Frigell, Jens
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Cumpstey, Ian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Carbasugar analogues of galactofuranosides: alpha-O-linked derivatives2010Ingår i: BEILSTEIN J ORG CHEM, ISSN 1860-5397, Vol. 6, s. 1127-1131Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using an indirect method, we have synthesised alpha-linked carbasugar analogues of galactofuranosides for the first time. Ring opening of a beta-talo configured carbasugar 1,2-epoxide by alcohol nucleophiles under Lewis acidic conditions proceeded with very good regioselectivity to give alpha-talo configured C1-substituted ethers with a free OH-group at the C2 position. Inversion of configuration at C2 by an oxidation-reduction sequence gave the alpha-galacto configured carbahexofuranose C1 ethers. A carbadisaccharide corresponding to the Galf(alpha 1 -> 3)Manp substructure from Apodus deciduus galactomannan was synthesised to exemplify the method.

  • 341.
    Frigell, Jens
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Eriksson, Lars
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Cumpstey, Ian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Carbasugar analogues of galactofuranosides: beta-O-linked derivatives and towards beta-S-linked derivatives2011Ingår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 346, nr 11, s. 1277-1290Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A selectively protected carbasugar analogue of beta-galactofuranose was synthesised from glucose using ring-closing metathesis as the key step. The carbasugar was converted into an alpha-galacto configured 1,2-epoxide, which was an effective electrophile in Lewis acid catalysed coupling reactions with alcohols. The epoxide was opened with regioselective attack at C-1 to give beta-galacto configured C-1 ethers. Using carbohydrates as nucleophiles, we synthesised a number of pseudodisaccharides. The epoxide was also regioselectively opened at C-1 with a sulfur nucleophile under basic conditions to give a beta-galacto configured C-1 thioether.

  • 342.
    Frigell, Jens
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Eriksson, Lars
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Cumpstey, Ian
    Carbasugar analogues of galactofuranosides: β-O-linked derivativesManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    A selectively protected carbasugar analogue of β-galactofuranose was synthesised from glucose using ring-closing metathesis as the key step. The carbasugar was converted into an α-galacto configured 1,2-epoxide, which was an effective electrophile in Lewis acid catalysed coupling reactions with alcohols. The epoxide was opened with regioselective attack at C-1 to give β-galacto configured C-1 ethers. Using carbohydrates as nucleophiles, we synthesised a number of pseudodisaccharides.

  • 343.
    Frigell, Jens
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Pearcey, J.A.
    Lowary, T.
    Cumpstey, Ian
    Carbasugar Analogues of Galactofuranose: Pseudodisaccharide Mimics of Fragments of Mycobacterial ArabinogalactanManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    A partially protected carbasugar analogue of β-galactofuranose was converted into an α-galacto configured 1,2-epoxide, which was was opened by alcohols under Lewis acid catalysis with regioselective attack at C-1 to give β-galacto configured C-1 ethers. Using OH-5 and OH-6 carbagalactofuranose derivatives as nucleophiles, we synthesised pseudodisaccharide analogues of substructures of the arabinogalactan from M. tuberculosis. The dicarba analogue of the disaccharide Galf(β1→5)Galf was found to moderately inhibit the action of GlfT2 galactofuranosyl transferase from M. tuberculosis.

  • 344.
    Frigell, Jens
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Pearcey, Jean A.
    Lowary, Todd L.
    Cumpstey, Ian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Carbasugar Analogues of Galactofuranosides: Pseudodisaccharide Mimics of Fragments of Mycobacterial Arabinogalactan2011Ingår i: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, nr 7, s. 1367-1375Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A partially protected carbasugar analogue of beta-galactofuranose was converted into an alpha-galacto-configured 1,2-epoxide, which was opened by alcohols under Lewis acid catalysis with regioselective attack at C-1 to give beta-galacto-configured C-1 ethers. Using OH-5 and OH-6 carbagalactofuranose derivatives as nucleophiles, we synthesised pseudodisaccharide analogues of substructures of the arabinogalactan from M. tuberculosis. The dicarba analogue of the disaccharide Galf(beta 1 -> 5) Galf was found to moderately inhibit the action of GlfT2 galactofuranosyl transferase from M. tuberculosis.

  • 345.
    Fryxelius, Jacob
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Design and Synthesis of Ligands for High-Valent Metal Oxidation Catalysts2006Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis describes several approaches towards the design of a water oxidation catalyst. Different aspects of coordination and water oxidation chemistry are adressed and result in various syntheses of ligands and their metal complexes.

  • 346.
    Fryxelius, Jacob
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Anderlund, Magnus
    Xu, Yunhua
    Huang, Ping
    Magnuson, Ann
    Sun, Licheng
    Åkermark, Björn
    A Tetranuclear Mn Dimer of DimersManuskript (Övrigt vetenskapligt)
  • 347.
    Fryxelius, Jacob
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Eilers, Gerriet
    Feyziyev, Yashar
    Magnuson, Ann
    Sun, Licheng
    Lomoth, Reiner
    Synthesis and redox properties of a [meso-tris(4-nitrophenyl)corrolato]Mn(III) complex2005Ingår i: Journal of Porphyrins and Phtalocyanines, Vol. 9, s. 379-386Artikel i tidskrift (Refereegranskat)
  • 348.
    Fryxelius, Jacob
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Pica, Delphine
    Eriksson, Lars
    Åkermark, Björn
    Preparation of Copper(II) Complexes of a Mixed Amide-Phenolate LigandIngår i: Inorganic Chemistry CommunicationsArtikel i tidskrift (Refereegranskat)
  • 349.
    Färnbäck, Magnus
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Eriksson, Lars
    Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Methyl 2-O-beta-L-fucopyranosyl alpha-D-glucopyranoside monohydrate: a synchrotron study2008Ingår i: Acta Crystallographica Section C, ISSN 0108-2701, Vol. 64, nr 2, s. o31-o32Artikel i tidskrift (Refereegranskat)
  • 350.
    Färnbäck, Magnus
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Söderman, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Eriksson, Lars
    Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Methyl 3,4,6-tri-O-acetyl-2-deoxy-2-azido-alpha-D-galactopyranosyl-(1-2)-: [3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl-(1-3)]-4-O-benzoyl-alpha-L-rhamnopyranoside n-hexane 0.1-solvate2007Ingår i: Acta Crystallographica: Section E, Vol. E63, s. o1581-o1583Artikel i tidskrift (Refereegranskat)
45678910 301 - 350 av 1369
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