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  • 401.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hammar, Peter
    Vesely, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramón
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Department of Physical, Inorganic and Structural Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Organocatalytic asymmetric hydrophosphination of alpha,beta-unsaturated aldehydes: Development, mechanism and DFT calculations2008In: Advanced Synthesis & Catalysis, ISSN 1615-4150, Vol. 350, no 11-12, p. 1875-1884Article in journal (Refereed)
  • 402. Ibrahem, Ismail
    et al.
    Iqbal, Muhammad Naeem
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eivazihollagh, Alireza
    Olsén, Peter
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Edlund, Håkan
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Norgren, Magnus
    Johnston, Eric V.
    Copper Nanoparticles on Controlled Pore Glass and TEMPO for the Aerobic Oxidation of Alcohols2018In: ChemNanoMat, ISSN 2199-692X, Vol. 4, no 1, p. 71-75Article in journal (Refereed)
    Abstract [en]

    Herein, we report on the facile synthesis of a heterogeneous copper nanocatalyst and its combination with 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) for the aerobic oxidation of alcohols to their corresponding carbonyl compounds. This low cost copper nanocatalyst was found to exhibit excellent recyclability, making it a highly attractive catalytic system from an economical and environmental point of view. Extensive characterization of the catalyst by a number of techniques revealed that it was comprised of well-dispersed Cu(I/II) nanoparticles with an average size of around 6nm.

  • 403. Ibrahem, Ismail
    et al.
    Ma, Guangning
    Afewerki, Samson
    Cordova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium/chiral amine co catalyzed enantioselective beta arylation of alpha,beta unsaturated aldehydes2013In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 52, no 3, p. 878-882Article in journal (Refereed)
  • 404.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramon
    Vesely, Jan
    Hammar, Peter
    Eriksson, Lars
    Himo, Fahmi
    Cordova, Armando
    Enantioselective Organocatalytic Hydrophosphination of α,β- Unsaturated Aldehydes2007In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 46, p. 4507-Article in journal (Refereed)
  • 405.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramon
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vesely, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Cordova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic enantioselective 5-hydroxyisoxazolidine synthesis: An asymmetric entry to beta-amino acids2008In: Synthesis (Stuttgart), ISSN 0039-7881, E-ISSN 1437-210X, no 7, p. 1153-1157Article in journal (Refereed)
    Abstract [en]

    The highly chemo- and enantioselective organocatalytic tandem reaction between N-carbamate-protected hydroxylamines and a,p-unsaturated aldehydes is presented. The reaction represents a unique entry for the asymmetric synthesis of 5-hydroxyisoxazolidines, oxazolidin-5-ones or gamma-hydroxyamino alcohols in high yields and 90-99% ee. A procedure for the conversion of the oxazolidin-5-ones into the corresponding beta-amino acids is also described.

  • 406.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramon
    Vesely, Jan
    Zhao, Guiling
    Cordova, Armando
    Organocatalytic Asymmetric 5-Hydroxyisoxazolidine Synthesis: A Highly Enantioselective Route to β-Amino Acids2007In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, p. 849-852Article in journal (Refereed)
  • 407.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramón
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vesely, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Organocatalytic asymmetric multi-component [C+NC+CC] synthesis of highly functionalized pyrrolidine derivatives2007In: Tetrahedron Letters, ISSN 0040-4039, Vol. 48, no 36, p. 6252-6257Article in journal (Refereed)
  • 408.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramón
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vesely, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hammar, Peter
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Himo, Fahmi
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantioselective organocatalytic hydrophosphination of alpha,beta-unsaturated aldehydes2007In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 46, p. 4507-4510Article in journal (Refereed)
  • 409.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramón
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vesely, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic enantioselective 5-hydroxyisoxazolidine synthesis: an asymmetric entry to beta-amino acids2007In: Synthesis, ISSN 0039-7881, no 7, p. 1153-1157Article in journal (Refereed)
  • 410.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramón
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vesely, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Organocatalytic asymmetric 5-hydroxyisoxazolidine synthesis: a highly enantioselective route to beta-amino acids2007In: Chemical Communications, p. 849-851Article in journal (Refereed)
  • 411. ibrahem, Ismail
    et al.
    Samec, Joseph S M
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdiva, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantioselective addition of aldehydes to amines via combined catalytic biomimetic oxidation and organocatalytic C-C- bond formation2005In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 46, no 23, p. 3965-3968Article in journal (Refereed)
    Abstract [en]

    The biomimetic catalytic enantioselective addition of aldehydes to amines is reported. This was accomplished by combining biomimetic coupled catalytic aerobic oxidation of amines involving ruthenium-induced dehydrogenation and organocatalytic asymmetric Mannich reactions. The novel one-pot reactions furnished β-amino aldehyde and α-amino acid derivatives in high yields with excellent chemoselectivity and up to >99% ee.

  • 412. Ibrahem, Ismail
    et al.
    Santoro, Stefano
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantioselective conjugate silyl additions to α,β-unsaturated aldehydes catalyzed by combination of transition metal and chiral amine catalysts2011In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 353, no 2+3, p. 245-252Article in journal (Refereed)
    Abstract [en]

    We report that transition metal-catalyzed nucleophilic activation can be combined with chiral amine-catalyzed iminium activation as exemplified by the unprecedented enantioselective conjugate addition of a dimethylsilanyl group to α,β-unsaturated aldehydes. These reactions proceed with excellent 1,4-selectivity to afford the corresponding β-silyl aldehyde products 3 in high yields and up to 97:3 er using inexpensive bench stable copper salts and simple chiral amine catalysts. The reaction canalso generate a quaternary stereocenter with goodenantioselectivity. Density functional calculations are performed to elucidate the reaction mechanism and the origin of enantioselectivity.

  • 413.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sundén, Henrik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramón
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Asymmetric amplification in the amino acid-catalyzed synthesis of amino acid derivatives2007In: Advanced Synthesis & Catalysis, ISSN 1615-4150, Vol. 349, no 11-12, p. 1868-1872Article in journal (Refereed)
  • 414.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sundén, Henrik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramón
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    One-pot pyrrolidine-catalyzed synthesis of benzopyrans, benzothiopyranes, and dihydroquinolidines2007In: Chimia, ISSN 0009-4293, Vol. 61, no 5, p. 219-223Article in journal (Refereed)
  • 415.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Guiling
    Cordova, Armando
    Direct Catalytic Enantioselective α-Aminomethylation of Aldehydes2007In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 13, p. 683-Article in journal (Refereed)
  • 416.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Direct catalytic enantioselective alpha-aminomethylation of aldehydes2007In: Chemistry: a European journal, Vol. 13, p. 683-688Article in journal (Refereed)
  • 417.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramón
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vesely, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sundén, Henrik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    One-pot organocatalytic domino Michael/alpha-alkylation reactions: direct catalytic enantioselective cyclopropanation and cyclopentanation reactions2008In: Chemistry: a European journal, ISSN 0947-6539, Vol. 14, no 26, p. 7867-7879Article in journal (Refereed)
  • 418.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zou, Weibiao
    Casas, Jesus
    Sunden, Henrik
    Cordova, Armando
    Direct Organocatalytic Enantioselective α-Aminomethylation of Ketones2006In: Tetrahedron, Vol. 62, p. 357-Article in journal (Refereed)
  • 419.
    Ilchenko, Nadia O.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Cortes, Miguel Angel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-Catalyzed lodofluorination of Alkenes Using Fluorolodoxole Reagent2016In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 6, no 1, p. 447-450Article in journal (Refereed)
    Abstract [en]

    The application of an air- and moisture-stable fluoroiodane reagent was investigated in the palladium-catalyzed iodofluorination reaction of alkenes. Both the iodo and fluoro substituents arise from the fluoroiodane reagent. In the case of certain palladium catalysts, the alkene substrates undergo allylic rearrangement prior to the iodofluorination process. The reaction is faster for electron-rich alkenes than for electron-deficient ones.

  • 420.
    Ilchenko, Nadia O.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hedberg, Martin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Fluorinative ring-opening of cyclopropanes by hypervalent iodine reagents. An efficient method for 1,3-oxyfluorination and 1,3-difluorination2017In: Chemical Sience, ISSN 2041-6520, Vol. 8, no 2, p. 1056-1061Article in journal (Refereed)
    Abstract [en]

    A new method is presented for 1,3-difluorination and 1,3-oxyfluorination reactions. The process is based on iodonium mediated opening of 1,1-disubstituted cyclopropanes. The reaction proceeds with high chemo- and regioselectivity under mild reaction conditions typically at room temperature in a couple of hours. The reaction probably occurs via electrophilic ring-opening of cyclopropanes.

  • 421.
    Ilchenko, Nadia O.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Janson, Pär G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Copper-Mediated Cyanotrifluoromethylation of Styrenes Using the Togni Reagent2013In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 78, no 21, p. 11087-11091Article in journal (Refereed)
    Abstract [en]

    Styrenes with an electron-deficient double bond undergo cyanotrifluoromethylation with a trifluoromethylated hypervalent iodine reagent in the presence of CuCN. The reaction proceeds under mild conditions in the presence of bulky phosphines or B(2)pin(2) additives. The process is highly regioselective and involves the consecutive formation of two C-C bonds in a single addition reaction. In the presence of a p-methoxy substituent in the styrene, oxytrifluoromethylation occurs instead of the cyanotrifluoromethylation.

  • 422.
    Ilchenko, Nadia O.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Janson, Pär
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Copper-mediated C-H trifluoromethylation of quinones2013In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 49, no 59, p. 6614-6616Article in journal (Refereed)
    Abstract [en]

    Quinones undergo copper-mediated C-H trifluoromethylation reactions using a hypervalent iodine reagent. The reactions have a broad synthetic scope involving naphtho, alkyl, chloro and methoxy quinones.

  • 423.
    Ilchenko, Nadia O.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Geminal difluorination of alpha,alpha '-disubstituted styrenes using fluoro-benziodoxole reagent. Migration aptitude of the alpha-substituents2017In: Journal of fluorine chemistry, ISSN 0022-1139, E-ISSN 1873-3328, Vol. 203, p. 104-109Article in journal (Refereed)
    Abstract [en]

    alpha,alpha'-Disubstituted styrenes undergo a difluorination-rearrangement reaction with fluoro-benzoiodoxole reagent 1. The reaction is catalyzed by Pd(MeCN)(4)(BF4)(2) and Cu(MeCN)(4)PF6. We have studied the rearrangement of alpha,alpha'-diaryl substituted styrenes, in which the aryl groups have different electronic character. In the case of a aryl, alpha'-alkyl substituted styrenes, the aryl substituent has a higher migratory aptitude than the alkyl group. We have also extended the reactions to cycloalkyl styrenes, which underwent interesting ring contraction/expansion reactions. The regioselectivity of the migration can be explained on the basis of the formation of a phenonium intermediate.

  • 424.
    Ilchenko, Nadia O.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tasch, Boris O. A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mild Silver-Mediated Geminal Difluorination of Styrenes Using an Air- and Moisture-Stable Fluoroiodane Reagent2014In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 53, no 47, p. 12897-12901Article in journal (Refereed)
    Abstract [en]

    An air-and moisture-stable fluoroiodane in the presence of AgBF4 is suitable for selective geminal difluorination of styrenes under mild reaction conditions. One of the C-F bonds is formed by transfer of electrophilic fluorine from the hypervalent iodine reagent, while the other one arises from the tetrafluoroborate counterion of silver. Deuterium-isotope-labelling experiments and rearrangement of methyl styrene substrates suggest that the reaction proceeds through a phenonium ion intermediate.

  • 425.
    Iqbal, M. Naeem
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Abdel-Magied, Ahmed F.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Abdelhamid, Hani Nasser
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Olsén, Peter
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shatskiy, Andrey
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mesoporous Ruthenium Oxide: A Heterogeneous Catalyst for Water Oxidation2017In: ACS Sustainable Chemistry & Engineering, ISSN 2168-0485, Vol. 5, no 11, p. 9651-9656Article in journal (Refereed)
    Abstract [en]

    Herein we report the synthesis of mesoporous ruthenium oxide (MP-RuO2) using a template-based approach. The catalytic efficiency of the prepared MP-RuO2 was compared to commercially available ruthenium oxide nanoparticles (C-RuO2) as heterogeneous catalysts for water oxidation. The results demonstrated superior performance of MP-RuO2 for oxygen evolution compared to the C-RuO2 with respect to recyclability, amount of generated oxygen, and stability over several catalytic runs.

  • 426. Jakhetia, Richa
    et al.
    Marri, Aruna
    Ståhle, Jonas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verma, Naresh K.
    Serotype-conversion in Shigella flexneri: identification of a novel bacteriophage, Sf101, from a serotype 7a strain2014In: BMC Genomics, ISSN 1471-2164, E-ISSN 1471-2164, Vol. 15, p. 742-Article in journal (Refereed)
    Abstract [en]

    Background: Shigella flexneri is the major cause of bacillary dysentery in the developing countries. The lipopolysaccharide (LPS) O-antigen of S. flexneri plays an important role in its pathogenesis and also divides S. flexneri into 19 serotypes. All the serotypes with an exception for serotype 6 share a common O-antigen backbone comprising of N-acetylglucosamine and three rhamnose residues. Different serotypes result from modification of the basic backbone conferred by phage-encoded glucosyltransferase and/or acetyltransferase genes, or plasmid-encoded phosphoethanolamine transferase. Recently, a new site for O-acetylation at positions 3 and 4 of Rha(III), in serotypes 1a, 1b, 2a, 5a and Y was shown to be mediated by the oacB gene. Additionally, this gene was shown to be carried by a transposon-like structure inserted upstream of the adrA region on the chromosome. Results: In this study, a novel bacteriophage Sf101, encoding the oacB gene was isolated and characterised from a serotype 7a strain. The complete sequence of its 38,742 bp genome encoding 66 open reading frames (orfs) was determined. Comparative analysis revealed that phage Sf101 has a mosaic genome, and most of its proteins were >90% identical to the proteins from 12 previously characterised lambdoid phages. In addition, the organisation of Sf101 genes was found to be highly similar to bacteriophage Sf6. Analysis of the Sf101 OacB identified two amino acid substitutions in the protein; however, results obtained by NMR spectroscopy confirmed that Sf101-OacB was functional. Inspection of the chromosomal integration site of Sf101 phage revealed that this phage integrates in the sbcB locus, thus unveiling a new site for integration of serotype-converting phages of S. flexneri, and determining an alternative location of oacB gene in the chromosome. Furthermore, this study identified oacB gene in several serotype 7a isolates from various regions providing evidence of O-acetyl modification in serotype 7a. Conclusions: This is the first report on the isolation of bacteriophage Sf101 which contains the S. flexneri O-antigen modification gene oacB. Sf101 has a highly mosaic genome and was found to integrate in the sbcB locus. These findings contribute an advance in our current knowledge of serotype converting phages of S. flexneri.

  • 427.
    Jalalian, Nazli
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ishikawa, Eloisa E.
    Silva Jr., Luiz F.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Room temperature, metal-free synthesis of diaryl ethers with use of diaryliodonium salts2011In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 13, no 6, p. 1552-1555Article in journal (Refereed)
    Abstract [en]

    A fast, high-yielding synthesis of diaryl ethers with use of mild and metal-free conditions has been developed. The scope includes bulky orthosubstituteddiaryl ethers, which are difficult to obtain by metal-catalyzed protocols. Halo-substituents, racemization-prone amino acid derivatives,and heteroaromatics are also tolerated. The methodology is expected to be of high utility in the synthesis of complex molecules and in thepharmaceutical industry.

  • 428.
    Jalalian, Nazli
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Design and asymmetric synthesis of chiral diaryliodonium salts2010In: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 66, no 31, p. 5793-5800Article in journal (Refereed)
    Abstract [en]

    The application of chiral hypervalent iodine reagents in asymmetric synthesis is highly desirable, as the reagents are metal-free, environmentally benign and employed under mild conditions. Three chiral diaryliodonium salts have been designed to provide chemoselectivity and asymmetric induction in asymmetric alpha-phenylation of carbonyl compounds. The synthetic routes to the selected targets are detailed herein, together with a structural investigation into the diastereoselectivity of the alkylation process.

  • 429.
    Jalalian, Nazli
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of Koser’s Reagent and Derivatives2013In: Organic Syntheses, ISSN 0078-6209, Vol. 90, p. 1-9Article in journal (Refereed)
  • 430.
    Jalalian, Nazli
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Petersen, Tue B.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Metal-Free Arylation of Oxygen Nucleophiles with Diaryliodonium Salts2012In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, no 44, p. 14140-14149Article in journal (Refereed)
    Abstract [en]

    Phenols and carboxylic acids are efficiently arylated with diaryliodonium salts. The reaction conditions are mild, metal free, and avoid the use of halogenated solvents, additives, and excess reagents. The products are obtained in good-to-excellent yields after short reaction times. Steric hindrance is very well tolerated, both in the nucleophile and diaryliodonium salt. The scope includes ortho-and halo-substituted products, which are difficult to obtain by metal-catalyzed protocols. Many functional groups are tolerated, including carbonyl groups, heteroatoms, and alkenes. Unsymmetric salts can be chemoselectively utilized to obtain products with hitherto unreported levels of steric congestion. The arylation has been extended to sulfonic acids, which can be converted to sulfonate esters by two different approaches. With recent advances in efficient synthetic procedures for diaryliodonium salts the reagents are now inexpensive and readily available. The iodoarene byproduct formed from the iodonium reagent can be recovered quantitatively and used to regenerate the diaryliodonium salt, which improves the atom economy.

  • 431.
    Jalilian, Ehsan
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liao, Rong-Zhen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Brismar, Hjalmar
    Laurell, Fredrik
    Lidin, Sven
    Luminescence properties of the Cu4I62- cluster2011In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 13, no 14, p. 4729-4734Article in journal (Refereed)
    Abstract [en]

    Two new solvates were prepared in the system Cu(I)I using a solvolysis reaction. The structures for both of them were solved by X-ray crystllaography, showing that they constitute two modifications of the same compound with the net formula [Cu4I6](P(C6H5)4)2·2OC(CH3)2. Both types of crystals show vivid fluorescence when exposed to UV light. The formation of the first modification (I) seems to be preferred by kinetics and on ageing in the mother liquor it converts to modification (II). The Cu positions in (I) are disordered while those in (II) are fully ordered. The luminescent properties of both crystals were characterized using a confocal microscope and an excitation wavelength of 405 nm, resulting in fluorescence spectra with the intensities of 1.22 and 0.52 relative to the reference (fluorescein 10 µM). Density functional theory calculations on the ordered Cu4I62− core of modification (II) show that the de-excitation from LUMO to HOMO is responsible for the luminescence. The calculated emission spectrum has a maximum at 531 nm in good agreement with the results from confocal microscopy.

  • 432.
    Jalilian, Ehsan
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liao, Rong-Zhen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lidin, Sven
    Luminescence properties of monoclinic Cu4I4(Piperidine)42011In: Materials research bulletin, ISSN 0025-5408, E-ISSN 1873-4227, Vol. 46, no 8, p. 1192-1196Article in journal (Refereed)
    Abstract [en]

    A new modification of Cu4I4Pip4 has been synthesized under hydrothermal conditions. X-ray crystallography revealed that this compound crystallized in the monoclinic system and consists of a tetrahedral core with composition Cu4I4, in which each Cu atom is coordinated by a piperidine molecule via the N atom. In contrast to a previously reported modification of Cu4I4Pip4, the present modification shows luminescent properties when exposed to UV-light. In addition, we have used time-dependent density functional theory calculations to characterize both compounds in term of both absorption and emission.

  • 433.
    Janson, Pär G.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ghoneim, Ibrahim
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ilchenko, Nadia O.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Electrophilic Trifluoromethylation by Copper-Catalyzed Addition of CF3-Transfer Reagents to Alkenes and Alkynes2012In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 14, no 11, p. 2882-2885Article in journal (Refereed)
    Abstract [en]

    Regio- and stereoselective Cu-catalyzed addition of the above hypervalent iodine reagent to alkynes and alkenes was achieved. In the presence of Cul, the reaction is suitable to perform trifluoromethyl-benzoyloxylation and trifluoromethyl-halogenation of alkenes and alkynes. Electron-donating substituents accelerate the process, and alkenes react faster than alkynes emphasizing the electrophilic character of the addition reaction.

  • 434.
    Janson, Pär G.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ilchenko, Nadia O.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Diez-Varga, Alberto
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Effects of B(2)pin(2) and PCy3 on copper-catalyzed trifluoromethylation of substituted alkenes and alkynes with the Togni reagent2015In: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 71, no 6, p. 922-931Article in journal (Refereed)
    Abstract [en]

    The copper-catalyzed oxytrifluoromethylation of phenylacetylenes and C-H trifluoromethylation of quinones were studied. It was found that both reactions are accelerated by B(2)pin(2) and PCy3 additives. The two reactions have different substituent effects. The oxytrifluoromethylation is faster in the presence of electron-donating groups, while the C-H trifluoromethylation is faster with electron-withdrawing substituents. The Hammett plot for oxytrifluoromethylation gave a rho value of 0.76 indicating electron demand in the rate determining step of the reaction. According to the absolute value of rho the reaction probably does not proceed through a rate determining formation of a carbocation intermediate. The kinetic isotope effect measurements indicate that in C-H trifluoromethylation of quinones the cleavage of the C-H bond is not the rate determining step of the reaction.

  • 435. Ji, Sanhao
    et al.
    Ju, Yong
    Fu, Hua
    Zhao, Yufen
    Johansson, Tommy
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stawinski, Jacek
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    The influences of a nitrogen atom position in dinucleoside 2-,3-,4-pyridylphosphonates on fragmentation patterns in electrospray ionization multistage tandem mass spectra2006In: Nucleosides, Nucleotides, and Nucleic Acids, ISSN 1525-7770, Vol. 25, p. 771-784Article in journal (Refereed)
  • 436.
    Jiang, Liying
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Spacil, Zdenek
    Stockholm University, Faculty of Science, Department of Analytical Chemistry. University of Washington, USA.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nilsson, Lennart
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Cordova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Mid-Sweden University, Sweden.
    Abiotic synthesis of amino acids and self-crystallization under prebiotic conditions2014In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 4, article id 6769Article in journal (Refereed)
    Abstract [en]

    Building on previous research on the origin and homochirality of life, this study focuses on analyses profiling important building blocks of life: the natural amino acids. The spark discharge variation of the iconic Miller experiment was performed with a reducing gas mixture of ammonia, methane, water and hydrogen. Amino acid analysis using liquid chromatography coupled with tandem mass spectrometry after pre-column derivatizaiton revealed the generation of several amino acids including those essential for life. Re-crystallization of the synthetic products and enantiomeric ratio analysis were subsequently performed. Results from liquid chromatography coupled with either fluorescent detector or tandem mass spectrometry after pre-column derivatization with chiral reagent revealed spontaneous and effective asymmetric resolution of serine and alanine. This work describes a useful analytical platform for investigation of hypotheses regarding the origin and homochirality of amino acids under prebiotic conditions. The formation of numerous amino acids in the electric discharge experiment and the occurrence of high enantiomeric ratios of amino acids in re-crystallization experiment give valuable implications for future studies in unraveling fundamental questions regarding origins and evolution of life.

  • 437.
    Jiang, Liying
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Johnston, Eric
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åberg, K. Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Strategy for quantifying trace levels of BMAA in cyanobacteria by LC/MS/MS2013In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 405, no 4, p. 1283-1292Article in journal (Refereed)
    Abstract [en]

    The cyanobacterial neurotoxin β-N-methylamino--alanine (BMAA) is an amino acid that is putatively associated with the pathology of amyotrophic lateral sclerosis/Parkinsonism –dementia complex (ALS-PDC) disease. It raises serious health risk concerns since cyanobacteria are ubiquitous thus making human exposure almost inevitable. The identification and quantification of BMAA in cyanobacteria is challenging because it is present only in trace amounts and occurs alongside structurally similar compounds such as BMAA isomers. This work describes an enhanced liquid chromatography/tandem mass spectrometry platform that can distinguish BMAA from its isomers β-amino-N-methyl-alanine, N-(2-oethyl) glycine (AEG), and 2,4-diaminobutyric acid, thus ensuring confident identification of BMAA. The method's sensitivity was improved fourfold by a post-column addition of acetonitrile. The instrument and method limits of detection were shown to be 4.2 fmol/injection (or 0.5 g/one column) and 0.1 μg/g dry weight of cyanobacteria, respectively. The quantification method uses synthesized deuterated BMAA as an internal standard and exhibits good linearity, accuracy, and precision. Matrix effects were also investigated, revealing an ion enhancement of around 18 %. A lab-cultured cyanobacterial sample (Leptolyngbya PCC73110) was analyzed and shown to contain about 0.73 μg/g dry weight BMAA. The isomer AEG, whose chromatographic properties closely resemble those of BMAA, was also detected. These results highlight the importance of distinguishing BMAA from its isomers for reliable identification as well as providing a sensitive and accurate quantification method for measuring trace levels of BMAA in cyanobacterial samples.

  • 438.
    Jiang, Min
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-Catalyzed Oxidative Regio- and Diastereoselective Diarylating Carbocyclization of Dienynes2013In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, no 21, p. 6571-6575Article in journal (Refereed)
  • 439.
    Jiang, Min
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Jiang, Tuo
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-Catalyzed Oxidative Diarylating Carbocyclization of Enynes2012In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 14, no 13, p. 3538-3541Article in journal (Refereed)
    Abstract [en]

    A mild and efficient palladium-catalyzed oxidative diarylating carbocyclization of enynes is described. The reaction tolerates a range of functionalized arylboronic acids to give diarylated products in good yields. Control experiments suggest that the reaction starts with an arylpalladation of the alkyne, followed by carbocyclization, transmetalation, and reductive elimination to afford the diarylated product.

  • 440. Jiang, Shi
    et al.
    Liu, Jianhui
    Shi, Yu
    Wang, Zhen
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Licheng
    Fe-S complexes containing five-membered heterocycles: novel models for the active site of hydrogenases with unusual low reduction potential2007In: Dalton Transactions, ISSN 1477-9226, no 8, p. 896-902Article in journal (Refereed)
  • 441. Jiang, Shi
    et al.
    Liu, Jianhui
    Shi, Yu
    Wang, Zhen
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Licheng
    Preparation, characteristics and crystal structures of novel N-heterocyclic carbene substituted furan- and pyridine-containing azadithiolate Fe-S complexes2007In: Polyhedron, ISSN 0277-5387, Vol. 26, no 7, p. 1499-1504Article in journal (Refereed)
  • 442.
    Jiang, Tuo
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bartholomeyzik, Teresa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mazuela, Javier
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Willersinn, Jochen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium(II)/Bronsted Acid-Catalyzed Enantioselective Oxidative Carbocyclization-Borylation of Enallenes2015In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 54, no 20, p. 6024-6027Article in journal (Refereed)
    Abstract [en]

    An enantioselective oxidative carbocyclization-borylation of enallenes that is catalyzed by palladium(II) and a Bronsted acid was developed. Biphenol-type chiral phosphoric acids were superior co-catalysts for inducing the enantioselective cyclization. A number of chiral borylated carbocycles were synthesized in high enantiomeric excess.

  • 443.
    Jiang, Tuo
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Persson, Andreas K. A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-Catalyzed Oxidative Carbocyclization/Arylation of Enallenes2011In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 13, no 21, p. 5838-5841Article in journal (Refereed)
    Abstract [en]

    A stereoselective palladium-catalyzed oxidative carbocyclization/arylation of enallenes is described. The reaction shows wide tolerance toward highly functionalized arylboronic acids and results In a cis addition of two carbon moieties to an olefin in good to excellent yields.

  • 444.
    Jiang, Tuo
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Quan, Xu
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhu, Can
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Andersson, Pher G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-Catalyzed Oxidative Synthesis of a-Acetoxylated Enones from Alkynes2016In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 55, no 19, p. 5824-5828Article in journal (Refereed)
    Abstract [en]

    We report a palladium-catalyzed oxidative functionalization of alkynes to generate -acetoxylated enones in one step. A range of functional groups are well-tolerated in this reaction. Mechanistic studies, including the use of O-18-labeled DMSO, revealed that the ketone oxygen atom in the product originates from DMSO.

  • 445.
    Jiang, Yan
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Deiana, Luca
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Alimohammadzadeh, Rana
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Liu, Leifeng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Cordova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Highly Diastereo- and Enantioselective Cascade Synthesis of Bicyclic Lactams in One-Pot2018In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, no 9, p. 1158-1164Article in journal (Refereed)
    Abstract [en]

    A versatile and highly stereoselective synthetic route to functionalized bi- and tricyclic lactams (up to > 20:1 dr and 99% ee) in one pot from simple starting materials (allylic alcohols, enals, diamines and amino alcohols) using cascade transformations promoted by chiral amine/BrOnsted or metal/chiral amine/BrOnsted relay catalysis is disclosed. Here molecular oxygen is employed as the terminal oxidant for the latter relay catalysis approach.

  • 446.
    Jimenez-Halla, J. Oscar C.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bickelhaupt, F. Matthias
    Sola, Miquel
    Organomagnesium clusters: Structure, stability, and bonding in archetypal models2011In: Journal of Organometallic Chemistry, ISSN 0022-328X, E-ISSN 1872-8561, Vol. 696, no 25, p. 4104-4111Article in journal (Refereed)
    Abstract [en]

    We have studied the molecular structure and the nature of the chemical bond in the monomers and tetramers of the Grignard reagent CH(3)MgCl as well as MgX(2) (X = H, Cl, and CH(3)) at the BP86/TZ2P level of theory. For the tetramers, we discuss the stability of three possible molecular structures of C(2h), D(2h), and T(d) symmetry. The most stable structure for (MgCl(2))(4) is D(2h), the one for (MgH(2))(4) is C(2h), and that of (CH(3)MgCl)(4) is T(d). The latter is 38 kcal/mol more stable with chlorines in bridge positions and methyl groups coordinated to a Mg vertex than vice versa. We find through a quantitative energy decomposition analysis (EDA) that the tetramerization energy is predominantly composed of electrostatic attraction Delta V(elstat) (60% of all bonding terms Delta V(elstat) + Delta E(oi)) although the orbital interaction Delta E(oi) also provides an important contribution (40%).

  • 447.
    Jimenez-Halla, J. Oscar C.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kalek, Marcin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stawinski, Jacek
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Computational study of the mechanism and selectivity of palladium catalyzed propargylic substitution with phosphorus nucleophiles2012In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, no 39, p. 12424-12436Article in journal (Refereed)
    Abstract [en]

    The mechanism and sources of selectivity in the palladium-catalyzed propargylic substitution reaction that involves phosphorus nucleophiles, and which yields predominantly allenylphosphonates and related compounds, have been studied computationally by means of density functional theory. Full free-energy profiles are computed for both H-phosphonate and H-phosphonothioate substrates. The calculations show that the special behavior of H-phosphonates among other heteroatom nucleophiles is indeed reflected in higher energy barriers for the attack on the central carbon atom of the allenyl/propargyl ligand relative to the ligand-exchange pathway, which leads to the experimentally observed products. It is argued that, to explain the preference of allenyl- versus propargyl-phosphonate/phosphonothioate formation in reactions that involve H-phosphonates and H-phosphonothioates, analysis of the complete free-energy surfaces is necessary, because the product ratio is determined by different transition states in the respective branches of the catalytic cycle. In addition, these transition states change in going from a H-phosphonate to a H-phosphonothioate nucleophile.

  • 448. Jo, Sunhwan
    et al.
    Myatt, Daniel
    Qi, Yifei
    Doutch, James
    Clifton, Luke A.
    Im, Wonpil
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Multiple Conformational States Contribute to the 3D Structure of a Glucan Decasaccharide: A Combined SAXS and MD Simulation Study2018In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 122, no 3, p. 1169-1175Article in journal (Refereed)
    Abstract [en]

    The inherent flexibility of carbohydrates is dependent on stereochemical arrangements, and characterization of their influence and importance will give insight into the three-dimensional structure and dynamics. In this study, a beta-(1 -> 4)/beta-(1 -> 3)-linked glucosyl decasaccharide is experimentally investigated by synchrotron small-angle X-ray scattering from which its radius of gyration (R-g) is obtained. Molecular dynamics (MD) simulations of the decasaccharide show four populated states at each glycosidic linkage, namely, syn- and anti-conformations. The calculated R-g values from the MD simulation reveal that in addition to syn-conformers the presence of anti-psi conformational states is required to reproduce experimental scattering data, unveiling inherent glycosidic linkage flexibility. The CHARMM36 force field for carbohydrates thus describes the conformational flexibility of the decasaccharide very well and captures the conceptual importance that anti-conformers are to be anticipated at glycosidic linkages of carbohydrates.

  • 449. Johannessen, Christian
    et al.
    Pendrill, Robert
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hecht, Lutz
    Barron, Laurence D.
    Glycan structure of a high-mannose glycoprotein from Raman optical activity2011In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 50, no 23, p. 5349-5351Article in journal (Refereed)
    Abstract [en]

    A revealing signature: The glycan structure of intact yeast external invertase, a high-mannose glycoprotein used as biocatalyst, was investigated by using Raman optical activity (ROA) spectroscopy. The conformational preferences present in mannose-containing di- and trisaccharides were found to be preserved in the glycan chains, with secondary polpeptide backbone structure suppressed.

  • 450.
    Johansson, Mikael
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lindén, Auri A.
    Bäckvall, Jan-E.
    Osmium-catalyzed dihydroxylation of alkenes by H2O2 in room temperature ionic liquid co-catalyzed by VO(acac)2 or MeReO32005In: Journal of organometallic chemistry, ISSN 0022-328X, Vol. 690, no 15, p. 3614-3619Article in journal (Refereed)
6789101112 401 - 450 of 1217
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