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  • 351.
    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.

  • 352.
    Ioannidis, Panagiotis
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of 5'-C-phosphonomethyl, 2'-C- and 3'-C-branched nucleoside analogues as potential candidates for therapeutic intervention towards HIV1993Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Syntheses of some 5'-C-phosphonomethyl-, 2'-C- and 3'-C-branched nucleoside analogues as potential anti-HIV agents are described. Synthesis of the various nucleoside analogues is based either on the construction of a suitably protected sugar moiety that can be glycosylated with different nucleoside bases by the Vorbrüggen procedure, or on the use of a novel alcohol transposition in the carbohydrate moiety of different 2'-C- or 3'-C-methylene nucleoside analogues, using the reagent system chlorodiphenylphosphine-iodine-imidazole. All target compounds were tested for anti-HIV activity. Of these, only 2',3'-dideoxy-2'-Chydroxymethylcytidine and l-(3,5-dideoxy-ß-D-cryrAro-hexofuranosyl)thymine demonstrated moderate and weak anti-HIV activities, respectively.

  • 353. 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.

  • 354.
    Jalalian, Nazli
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Development and Applications of Hypervalent Iodine Compounds: Powerful Arylation and Oxidation Reagents2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The first part of this thesis describes the efficient synthesis of several hypervalent iodine(III) compounds. Electron-rich diaryliodonium salts have been synthesized in a one-pot procedure, employing mCPBA as the oxidant. Both symmetric and unsymmetric diaryliodonium tosylates can be isolated in high yields. An in situ anion exchange also enables the synthesis of previously unobtainable diaryliodonium triflates.

    A large-scale protocol for the synthesis of a derivative of Koser’s reagent, that is an isolable intermediate in the diaryliodonium tosylate synthesis, is furthermore described. The large-scale synthesis is performed in neat TFE, which can be recovered and recycled. This is very desirable from an environmental point of view.

    One of the few described syntheses of enantiopure diaryliodonium salts is discussed. Three different enantiopure diaryliodonium salts bearing electron-rich substituents are synthesized in moderate to high yields. The synthesis of these three salts shows the challenge in the preparation of electron-rich substituted unsymmetric salts.

    The second part of the thesis describes the application of both symmetric and unsymmetric diaryliodonium salts in organic synthesis. A metal-free efficient and fast method for the synthesis of diaryl ethers from diaryliodonium salts has been developed. The substrate scope is wide as both the phenol and the diaryliodonium salt can be varied. Products such as halogenated ethers, ortho-substituted ethers and bulky ethers, that are difficult to obtain with metal-catalyzed procedures, are readily prepared. The mild protocol allows arylation of racemization-prone a-amino acid derivatives without loss of enantiomeric excess.

    A chemoselectivity investigation was conducted, in which unsymmetric diaryliodonium salts were employed in the arylation of three different nucleophiles in order to understand the different factors that influence which aryl moiety that is transferred to the nucleophile.

  • 355.
    Jalalian, Nazli
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis and applications of diaryliodonium salts2010Licentiate thesis, comprehensive summary (Other academic)
  • 356.
    Jalalian, Nazli
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ishikawa, Eloisa E.
    Universidade de Sao Paulo, Instituto de Quimica.
    Silva Jr., Luiz F.
    Universidade de Sao Paulo, Instituto de Quimica.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Room temperature, metal-free synthesis of diaryl ethers with use of diaryliodonium salts2011In: Abstracts of Papers, 242nd ACS National Meeting & Exposition, Denver, CO, United States, August 28-September 1, 2011, American Chemical Society , 2011Conference paper (Other academic)
    Abstract [en]

    Diaryl ethers are common structural features in numerous natural products and biol. active compds.  Despite more than a century of immense focus on finding efficient synthetic routes to this compd. class, diaryl ethers remain difficult to obtain.  Routes that are catalytic in copper have been developed, but high catalyst loadings, excess reagents, elevated temps. and long reaction times are still needed.  Pd-catalyzed cross-couplings of phenols and aryl halides at temps. up to 100 °C have recently been reported to give high yields of diaryl ethers.  Diaryliodonium salts are non-toxic alternatives to transition metals in the synthesis of diaryl ethers and we have recently developed effective synthetic routes to these salts.  Herein we report a fast, high-yielding synthesis of diaryl ethers.  The reaction conditions are mild, metal-free, and avoid the use of halogenated solvents, additives, or excess reagents.  Precautions to avoid air or moisture are not needed.  The scope includes ortho- and halo-substituted diaryl ethers, which are difficult to obtain by metal-catalyzed protocols .

  • 357.
    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.

  • 358.
    Jalalian, Nazli
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Asymmetric α-arylation of carbonyl compounds with chiral diaryliodonium salts2009In: Abstracts of Papers, 238th ACS National Meeting, Washington, DC, United States, August 16-20, 2009, Washington, D.C.: American Chemical Society , 2009Conference paper (Other academic)
  • 359.
    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.

  • 360.
    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)
  • 361.
    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.

  • 362.
    Janson, Pär
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Oxidative Trifluoromethylation and other Functionalization Reactions of Alkenes and Alkynes2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis concerns the use of various potent oxidants in organic synthesis. The main focus is directed at selectively introducing trifluoromethyl groups into compounds containing double or triple bonds. All reactions proceed under mild conditions and can in most cases be performed on the bench-top.

    We have developed three different procedures for transformations of activated alkenes and alkynes as well as quinones. In paper I the selective introduction of a trifluoromethyl group together with an oxygen functionality to double and triple bonds is demonstrated.

    Paper II is focused on the related chemoselective cyanotrifluoromethylation in which a cyano group is added instead of the oxygen functionality.

    Paper III describes a new procedure for C–H trifluoromethylation of quinones. Our studies on the mechanistic aspects of the above reactions are described in Paper IV. In these studies we investigated the ligand and substituent effects in Cu-catalyzed reactions.

    Paper V is focused on a conceptually new palladium-catalyzed allylic C–H acyloxylation of olefins under oxidative conditions. The procedure uses an inexpensive, safe and environmentally benign oxidant, sodium perborate, which is activated with acetic anhydride.

  • 363.
    Janson, Pär G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Metal-catalyzed oxidative formation of C-CF3 and C-O bonds in alkenes and alkynes2012Licentiate thesis, comprehensive summary (Other academic)
  • 364.
    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.

  • 365.
    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.

  • 366.
    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.

  • 367.
    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.

  • 368.
    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.

  • 369.
    Jiang, Tuo
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium(II)-Catalyzed Oxidative Carbocyclization: Stereoselective Formation of C–C and C–B Bonds2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Transition metal catalysis has emerged as one of the most versatile methods for the selective formation of carbon–carbon and carbon–heteroatom bonds. In particular, oxidative carbon–carbon bond forming reactions have been widely studied due to their atom economic feature. This thesis has been focused on the development of new palladium(II)-catalyzed carbocyclization reactions under oxidative conditions.

    The first part of the thesis describes the palladium(II)-catalyzed oxidative carbocyclization-borylation and -arylation of enallenes. In these reactions, the (σ-alkyl)palladium(II) intermediate, which was shown previously to undergo β-hydride elimination, could be trapped in situ by organoboron reagents (B2pin2 and arylboronic acids) to form new carbon–boron and carbon–carbon bonds. Through these two protocols, a range of borylated and arylated carbocycles were obtained as single diastereomers in high yields.

    The second part deals with a palladium(II)-catalyzed oxidative diarylative carbocyclization of enynes. The reaction was proposed to start with a syn-arylpalladation of an alkyne, followed by insertion of the coordinated alkene. Subsequent arylation afforded a series of valuable diarylated tetrahydrofuran and tetrahydropyran products.

    The final part of the thesis advances the previously developed palladium(II)-catalyzed oxidative carbocyclization-borylation of enallenes in an enantioselective manner. C2-symmetric chiral phosphoric acids were used as the novel co-catalyst to trigger the enantioselective formation of intramolecular carbon–carbon bonds. By using this chiral anion strategy, a number of enallenes were converted to the borylated carbocycles with high to excellent enantioselectivity.

  • 370.
    Jiang, Tuo
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium(II)-catalyzed oxidativecarbocyclization: Functionalization with Boron-Containing Reagents2012Licentiate thesis, comprehensive summary (Other academic)
  • 371.
    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.

  • 372.
    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.

  • 373.
    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.

  • 374.
    Jiang, Yan
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Deiana, Luca
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhang, Kaiheng
    Lin, Shuangzheng
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Mid Sweden University, Sweden.
    Total Asymmetric Synthesis of Quinine, Quinidine, and Analogues via Catalytic Enantioselective Cascade Transformations2019In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690Article in journal (Refereed)
    Abstract [en]

    A catalytic asymmetric strategy for the total synthesis of quinuclidine natural products, which includes the completed enantioselective synthesis of the classical targets quinine and quinidine is disclosed. It is based on catalytic asymmetric cascade transformations, which paves the road for the synthesis of both enantiomers of the crucial C4 stereocenter with high enantioselectivity (up to 99 % ee) in one pot. Next, developing a route to all possible stereoisomers of a common early-stage intermediate sets the stage for the total synthesis of different enantiomers or epimers of quinine, quinidine and analogues with high selectivity.

  • 375. 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.

  • 376. 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.

  • 377.
    Johansson, Karl-Jonas
    Stockholm University.
    Studies of the anomeric center: mechanism and synthesis2000Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is based on three publications and one appendix and is divided into two parts. The first part is a mechanistic study of the anomerization reaction of both aldo and keto glycosides and the second part is a synthetic study of a unusual type of glycosidic linker found in the lipopolysaccharide core Proteus Mirabilis 0270.

    The first chapter contains a general introduction to the thesis.The second chapter treats the anomerization reaction of alkyl furanosides both by trapping experiments and kinetics. The conclusion from these studies is that the reaction proceeds via a concerted endo-cyclic C-O bond cleavage.The third chapter concerns the anomerization of alkyl pyranosides by the same techniques as those used in chapter 2. The results from these studies confirm that the reaction proceeds via exo-cyclic C-O bond cleavage.In the fourth chapter the anomerization of methyl fructosides has been investigated by trapping experiments. The outcome of this study is that the anomerization of fructosides occur via exo-cyclic C-O bond cleavage and that the anomerization reaction proceeds faster than ring-interconverison.In the final chapter an analogue of the unusual type of glycosidic linker fond in Proteus Mirabilis 0270 has been synthesised i.e. methyl ((1S)-arabinosyl o-(1Æ4,6))-a-D-galactopyranoside.

  • 378.
    Johansson, Olof
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Wolpher, Henriette
    Borgström, Magnus
    Hammarström, Leif
    Bergquist, Jonas
    Sun, Licheng
    Åkermark, Björn
    Intramolecular charge separation in a hydrogen bonded tyrosune-ruthenium(II) baphthalene diimide triad2004In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, p. 194-195Article in journal (Refereed)
  • 379.
    Johansson, Tommy
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Studies on Transformations of H-Phosphonates into DNA Analogues Containing P-S or P-C Bonds2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, mechanistic and synthetic studies on transformations of H-phosphonates into DNA analogues containing P-S or P-C bonds are described.

    Configurational stability of dinucleoside H-phosphonates and the stereochemical course of their sulfurisation in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) were investigated. In light of these studies, the reported stereoselective sulfurisation of dinucleoside H-phosphonates and benzoylphosphonates in the presence of DBU was proved to be incorrect.

    Efficient protocols for the synthesis of new nucleotide analogues with non-ionic C-phosphonate internucleotide linkages were developed. The synthesis of dinucleoside 2-pyridylphosphonates was successfully performed by a DBU-promoted reaction of H-phosphonate diesters with N-methoxypyridinium salts. The thio analogues, 2-pyridyl- and 4-pyridyl phosphonothioate diesters, could be obtained by modifying the reactions developed for their oxo counterparts. Dinucleoside 3-pyridylphosphonates were prepared via a palladium(0)-catalysed cross coupling strategy that could be extended also to the synthesis of nucleotide analogues with metal-complexing properties, i.e. terpyridyl- and bipyridylphosphonate derivatives.

    Oligonucleotides modified with pyridylphosphonate internucleotide linkages have been prepared and preliminary studies on their hybridisation properties and resistance towards enzymatic degradation were performed.

    Finally, nucleotidic units for the incorporation of pyridylphosphonate groups at the 5’-terminus of oligonucleotides were designed. Condensations of such units with a suitably protected nucleoside afforded after oxidation the expected dinucleoside (3’-5’)-phosphates with pyridylphosphonate monoester functions at the 5’-ends.

  • 380.
    Johansson, Tommy
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kers, Annika
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stawinski, Jacek
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    2-Pyridylphosphonates: A New type of Modification for Nucleotide Analogues2001In: Tetrahedron Letters, ISSN 0040-4039, Vol. 42, no 11, p. 2217-2220Article in journal (Refereed)
    Abstract [en]

    Suitably protected dithymidine H-phosphonates afforded the corresponding dinucleoside 2-pyridylphosphonates upon treatment with N-methoxypyridinium tosylate in acetonitrile in the presence of 1,8-diazabicylo[5.4.0]undec-7-ene (DBU). The reaction was rapid (ca. 5 min), practically quantitative and proceeded stereospecifically, most likely with retention of configuration at the phosphorus centre.

    A simple and efficient protocol for the preparation of a new type of oligonucleotide analogue bearing a 2-pyridylphosphonate internucleotide linkage was developed

  • 381.
    Johansson, Tommy
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stawinski, Jacek
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of Dinucleoside Pyridylphosphonates Involving Palladium(0)-catalysed Phosphorus-carbon Bond Formation as a Key Step2001In: Chemical Communications, ISSN 1359-7345, no 24, p. 2564-2565Article in journal (Refereed)
    Abstract [en]

    Dinucleoside 3-pyridylphosphonates, as well as their 2- and 4-pyridyl positional isomers, have been synthesised using a palladium(0)-catalysed cross coupling strategy

  • 382.
    Johansson, Tommy
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stawinski, Jacek
    The Case for Configurational Stability of H-Phosphonate Diesters in the Presence of Diazabicyclo[5.4.0]undec-7-ene (DBU)2001In: Bioorganic & Medicinal Chemistry, ISSN 0968-0896, Vol. 9, no 9, p. 2315-2322Article in journal (Refereed)
    Abstract [en]

    Configurational stability of dinucleoside H-phosphonates and the stereochemical course of their sulfurisation in the presence of diazabicyclo[5.4.0]undec-7-ene (DBU) were investigated using 31P NMR spectroscopy. It was found that under the reaction conditions and irrespective of the type of protecting groups present in the nucleoside moieties, the H-phosphonate diesters investigated did not undergo any detectable epimerisation at the phosphorus centre, and their sulfurisation with elemental sulfur in the presence of DBU, proceeded stereospecifically. Thus, we could not confirm reports from another laboratory on a stereoselective course of sulfurisation of H-phosphonate diesters and the corresponding acylphosphonates in the presence of DBU.

  • 383.
    Johnston, Eric
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Biomimetic oxidation methods: Efficient reoxidation of palladium and ruthenium by the use of a hybrid electron transfer catalyst.2009Licentiate thesis, comprehensive summary (Other academic)
  • 384.
    Johnston, Eric
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    New Tools for Green Catalysis: Studies on a Biomimetic Hybrid Catalyst and a Novel Nanopalladium Catalyst2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The first part of this thesis describes an improved synthetic route to hybrid (hydroquinone-Schiff base)cobalt catalysts. Preparation of the 5-(2,5-hydroxyphenyl)salicylaldehyde building block was improved by altering the protective groups of the hydroquinone (HQ) starting material. Both protection and deprotection could be carried out under mild conditions, resulting in high yields. By optimizing the reaction conditions of the Suzuki cross-coupling, an efficient and inexpensive synthetic route with a good overall yield was developed.

    The second part describes the use of the hybrid catalyst as an electron transfer mediator (ETM) in the palladium-catalyzed aerobic carbocyclization of enallenes. By covalently linking the HQ to the cobalt Schiff-base complex the reaction proceeded at lower temperatures with a five-fold increase of the reaction rate compared to the previously reported system.

    The third part describes the application of the hybrid catalyst in the biomimetic aerobic oxidation of secondary alcohols. Due to the effi­ciency of the intramolecular electron transfer, the hybrid catalyst allowed for a lower catalytic loading and milder reaction conditions compared to the previous separate-component system. Benzylic alcohols as well as aliphatic alcohols were oxidized to the corresponding ketones in excellent yield and selectivity using this methodology.

    The fourth part describes the synthesis and characterization of highly dispersed palladium nanoparticles supported on aminopropyl-modified siliceous mesocellular foam. The Pd nanocatalyst showed excellent activity for the aerobic oxidation of a wide variety of alcohols under air atmosphere. Moreover, the catalyst can be recycled several times without any decrease in activity or leaching of the metal into solution.

    Finally, the fifth part describes the application of the Pd nanocatalyst in transfer hydrogenations and Suzuki coupling reactions. The catalyst was found to be highly efficient for both transformations, resulting in chemoselective reduction of various alkenes as well as coupling of a variety of aryl halides with various boronic acids in excellent yields. Performing the latter reaction under microwave irradiation significantly increased the reaction rate, compared to conventional heating. However, no significant increase in reaction rate was observed for the transfer hydrogenations, under microwave heating.

  • 385.
    Johnston, Eric V
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bogár, Krisztián
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantioselective synthesis of (R)-bufuralol via dynamic kinetic resolution in the key step2010In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 75, no 13, p. 4596-4599Article in journal (Refereed)
    Abstract [en]

    An enantioselective synthesis of (R)-bufuralol via a ruthenium- and enzyme-catalyzed dynamic kinetic resolution (DKR) has been achieved. The synthesis starts from readily available 2-ethylphenol and provides (R)-bufuralol in high ee and a good overall yield of 31%.

  • 386.
    Johnston, Eric V.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Oxidation of carbonyl compounds2010In: Modern Oxidation Methods / [ed] Jan-Erling Bäckvall, Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA , 2010, 2, p. 353-369Chapter in book (Other academic)
  • 387.
    Johnston, Eric V
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Karlsson, Erik A
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lee, Bao-Lin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Novel dinuclear Ru-complex for water oxidation2010In: Abstracts of Papers, 240th ACS National Meeting, Boston, MA, United States, August 22-26, 2010 (2010), American Chemical Society , 2010Conference paper (Other academic)
  • 388.
    Johnston, Eric V.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Karlsson, Erik A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lindberg, Staffan A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient reoxidation of palladium by a hybrid catalyst in aerobic palladium-catalyzed carbocyclization of enallenes2009In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 28, p. 6799-6801Article in journal (Refereed)
  • 389.
    Johnston, Eric V.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Karlsson, Erik A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tran, Lien-Hoa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient aerobic ruthenium-catalyzed oxidation of secondary alcohols by the use of a hybrid electron transfer catalyst2010In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, no 10, p. 1971-1976Article in journal (Refereed)
    Abstract [en]

    Biomimetic aerobic oxidation of secondary alcohols has been performed using hybrid catalyst 1 and Shvo's catalyst 2. This combination allows mild reaction conditions and low catalytic loading, due to the efficiency of intramolecular electron transfer. By this method a wide range of different alcohols have been converted into their corresponding ketones. Oxidation of benzylic as well as aliphatic, electron-rich, electron-deficient and sterically hindered alcohols could be oxidized in excellent yield and selectivity. Oxidation of (S)-1-phenyl-ethanol showed that no racemization occurred during the course of the reaction, indicating that the hydride 2b adds to the quinone much faster than it re-adds to the ketone product. The kinetic deuterium isotope effect of the oxidation was determined by the use of 1-phenylethanol (3a) and 1-deuterio-1-phenylethanol (3a-d1) in parallel and competitive manner, which gave the same isotope effect within experimental error (k(H)/k(D) approximate to 2.8). This indicates that there is no strong coordination of the substrate to the catalyst.

  • 390.
    Johnston, Eric V.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Karlsson, Erik A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tran, Lien-Hoa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient synthesis of hybrid (hydroquinone-Schiff base)cobalt oxidation catalysts2009In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, no 23, p. 3973-3976Article in journal (Refereed)
    Abstract [en]

    Hybrid catalysts A and B have recently been found to efficiently transfer electrons from a metal catalyst to molecular oxygen in biomimetic oxidations. In the present work hybrid catalysts A and B were synthesized in high yield from inexpensive starting materials. The key step is an efficient Suzuki cross-coupling, which allows the use of unprotected aldehyde 5. The new synthesis of the title hybrid catalysts is easy to carry out and can be scaled up.

  • 391.
    Johnston, Eric V.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shakeri, Mozaffar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Palmgren, Pål
    Eriksson, Kristofer
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Oscarsson, Sven
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Highly dispersed palladium nanoparticles on mesocellular foam: an efficient and recyclable heterogeneous catalyst for alcohol oxidation2012In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, no 39, p. 12202-12206Article in journal (Refereed)
  • 392.
    Jonasson, Catrin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium (II)-catalyzed oxidations of allenes and conjugated dienes2000Doctoral thesis, comprehensive summary (Other academic)
  • 393.
    Jonsson, Hanna
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Exploring the structure of oligo- and polysaccharides: Synthesis and NMR spectroscopy studies2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A deeper understanding of the diversity of carbohydrates and the many applications of oligo- and polysaccharides found in nature are of high interest. Many of the processes involving carbohydrates affect our everyday life. This thesis is based on six papers all contributing to an extended perspective of carbohydrate property and functionality. An introduction to carbohydrate chemistry together with a presentation of selected carbohydrate synthesis and analysis methods introduces the reader to the research field. The first paper is an NMR spectroscopy reinvestigation of the structures of the O-antigens from the lipopolysaccharides (LPS) of Shigella dysenteriae type 3 and Escherichia coli O124. The repeating units were concluded to be built of identical branched pentasaccharides now with the correct anomeric configurations. Paper II is a structural investigation of the O-antigen from the LPS of E. coli O74 which is built of branched tetrasaccharide repeating units including the uncommon monosaccharide d-Fuc3NAc. Paper III is a conformational study of a rhamnose derivative, using NMR spectroscopy and X-ray crystallography. The benzoyl ester group positioned at C4 prefers an “eclipsed” conformation in the crystal as well as in solution. The use of site-specifically 13C-labeled compounds in conformational studies is discussed in Papers IV and V. The disaccharide α-L-Rhap-(1→2)-α-L-Rhap-OMe was synthesized together with two 13C-isotopologues and studied with NMR spectroscopy to give seven J-couplings related to torsion angles φ and ψ. The trisaccharide α-L-Rhap-(1→2)[α-L-Rhap-(1→3)]-α-L-Rhap-OMe was synthesized with 13C-labeling at two positions which presented a solution to a problem of overlapping signals in the 1H NMR spectrum. The site-specific labeling also facilitated the measurement of two 3JCC and two 2JCH coupling constants. Finally, chapter 6 gives a short introduction to glycosynthase chemistry and discusses the synthesis of α-glycosyl fluorides. A novel cyclic heptasaccharide was synthesized from α-laminariheptaosyl fluoride using a mutant of the enzyme laminarase 16A and subsequently analyzed by NMR spectroscopy.

  • 394.
    Jonsson, K. Hanna M.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pendrill, Robert
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    NMR analysis of conformationally dependent nJC,H and nJC,C in the trisaccharide α-L-Rhap-(1→2)[α-L-Rhap-(1→3)]-α-L-Rhap-OMe and a site-specifically labeled isotopologue thereof2011In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 49, no 3, p. 117-124Article in journal (Refereed)
    Abstract [en]

    An array of NMR spectroscopy experiments have been carried out to obtain conformationally dependent 1H,13C- and 13C,13C-spin–spin coupling constants in the trisaccharide α-L-Rhap-(1 → 2)[α-L-Rhap-(1 → 3)]-α-L-Rhap-OMe. The trisaccharide was synthesized with 13C site-specific labeling at C2′ and C2″, i.e. in the rhamnosyl groups in order to alleviate 1H spectral overlap. This facilitated the measurement of a key trans-glycosidic proton–proton cross-relaxation rate using 1D 1H,1H-T-ROESY experiments as well as a 3JC, H coupling employing 1D 1H,13C-long-range experiments, devoid of potential interference from additional J coupling. By means of both the natural abundance compound and the 13C-labeled sample 2D 1H,13C-J-HMBC and 1H,13C-HSQC-HECADE NMR experiments, total line-shape analysis of 1H NMR spectra and 1D 13C NMR experiments were employed to extract 3JC, H, 2JC, H, 3JC, C, and 1JC, C coupling constants. The 13C site-specific labeling facilitates straightforward determination of nJC, C as the splitting of the 13C natural abundance resonances. This study resulted in eight conformationally dependent coupling constants for the trisaccharide and illustrates the use of 13C site-specific labeling as a valuable approach that extends the 1D and 2D NMR methods in current use to attain both hetero- and homonuclear spin–spin coupling constants that subsequently can be utilized for conformational analysis.

  • 395.
    Jonsson, K. Hanna M.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Säwén, Elin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Studies on the conformational flexibility of alpha-L-rhamnose-containing oligosaccharides using C-13-site-specific labeling, NMR spectroscopy and molecular simulations: implications for the three-dimensional structure of bacterial rhamnan polysaccharides2012In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 10, no 12, p. 2453-2463Article in journal (Refereed)
    Abstract [en]

    Bacterial polysaccharides are comprised of a variety of monosaccharides, L-rhamnose (6-deoxy-L-mannose) being one of them. This sugar is often part of alpha-(1 -> 2)- and/or alpha-(1 -> 3)-linkages and we have therefore studied the disaccharide alpha-L-Rhap-(1 -> 2)-alpha-L-Rhap-OMe to obtain information on conformational preferences at this glycosidic linkage. The target disaccharide was synthesized with C-13 site-specific labeling at C1' and at C2', i.e., in the terminal group. 2D H-1, C-13-HSQC-HECADE and H-1, C-13-J-HMBC NMR experiments, 1D C-13 and H-1 NMR spectra together with total line-shape analysis were used to extract conformationally dependent hetero- and homonuclear spin-spin coupling constants. This resulted in the determination of (2)JC(2',H1'), (3)J(C1',C1), (3)J(C1',C3), (3)J(C2',C2), (2)J(C1',C2), (1)JC(1',C2'), and (1)J(C1',H1'). These data together with previously determined J(CH) and H-1, H-1 NOEs result in fourteen conformationally dependent NMR parameters that are available for analysis of glycosidic linkage flexibility and conformational preferences. A 100 ns molecular dynamics (MD) simulation of the disaccharide with explicit water molecules as solvent showed a major conformational state at phi(H) approximate to 40 degrees and psi(H) approximate to -35 degrees, consistent with experimental NMR data. In addition, MD simulations were carried out also for alpha-L-Rhap-(1 -> 3)-alpha-L-Rhap-OMe and a rhamnan hexasaccharide. The gathered information on the oligosaccharides was used to address conformational preferences for a larger structure, a 2- and 3-linked nonasaccharide, with implications for the 3D structure of rhamnan polysaccharides, which should be regarded as flexible polymers.

  • 396.
    Jonsson, K. Hanna M.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Weintraub, Andrej
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Structural studies of the O-antigenic polysaccharide from Shigella dysenteriae type 3 and Escherichia coli O124, a reinvestigation2006In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 341, p. 2986-2989Article in journal (Refereed)
  • 397. Jonsson, Sandra Y.
    Selective functionalisation of carbon-carbon double bonds: dihydroxylation of olefins by H₂O₂ & transformation of sulfonyl 1,3-dienes2002Doctoral thesis, comprehensive summary (Other academic)
  • 398.
    Joosten, Antoine
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Persson, Andreas K. A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Millet, Renaud
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnson, Magnus T.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium(II)-Catalyzed Oxidative Cyclization of Allylic Tosylcarbamates: Scope, Derivatization, and Mechanistic Aspects2012In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, no 47, p. 15151-15157Article, review/survey (Refereed)
    Abstract [en]

    A highly selective oxidative palladium(II)-catalyzed (Wacker-type) cyclization of readily available allylic tosylcarbamates is reported. This operationally simple catalytic reaction furnishes tosyl-protected vinyl-oxazolidinones, common precursors to syn-1,2-amino alcohols, in high yield and excellent diasteroselectivity (>20:1). It is demonstrated that both stoichiometric amounts of benzoquinone (BQ) as well as aerobic reoxidation (molecular oxygen) is suitable for this transformation. The title reaction is shown to proceed through overall trans-amidopalladation of the olefin followed by beta-hydride elimination. This process is scalable and the products are suitable for a range of subsequent transformations such as: kinetic resolution (KR) and oxidative Heck-, Wacker-, and metathesis reactions.

  • 399.
    Jönsson, Daniel
    Stockholm University, Faculty of Science, Department of Neurochemistry and Neurotoxicology.
    Applications of multi-component condensations and development of polyamine synthesis on solid-phase2002Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Solid-phase synthesis of small non-polymeric molecules has become increasingly important as a tool in the development of pharmacologically active compounds. Of particular interest are the syntheses of compounds with low molecular weight, low polarity and a reduced flexibility of the functional groups, i.e. physiochemical properties typical for the majority of drugs currently in use.

    The first part of this thesis describes the synthesis of polycyclic structures with constrained conformation, by the application of multi-component condensations on solid-phase. The 8-azabicyclo[3.2.1]octan-3-one structure of the tropane alkaloids was synthesized on solid-phase by a modification of the well known Robinson tropinone synthesis. The 3-component reaction was performed with the amino component anchored to a solid support, consisting of polyethyleneglycol-grafted polystyrene. Treatment of the primary amine with 1,3-acetonedicarboxylic acid and excess of succinaldehyde, resulted in high purity of the corresponding tropane derivative. Further derivatization of the resin-bound tropane derivative was performed by reduction of the keto-group and acylation of the hydroxyl-group.

    The oxygen-bridged tetrahydropyridones are relatively complex polycyclic structures, which previously have been synthesized in solution by condensation of primary amines, coumarin-3-carboxylic acid and ketones. In the evaluation of a solid-phase approach of this 3-component condensation, several members of this class of compounds were synthesized with the amine anchored to a solid support. The yield and purity of the products were dependent on the ketones used in the reaction, but the expected products were obtained using both acyclic and cyclic ketones and substituted acetophenones.

    The second part of this thesis describes the development of a solid-phase polyamine synthesis. The polyamines are a class of compounds with a wide range of pharmacological and physiological effects, which are constituents in many types of venoms of wasps and spiders. Synthesis of polyamines in homogenous solution is accompanied with several problems concerning selectivity, work-up and yield. By employing a solid-phase approach, a rapid and convenient method for synthesis of polyamines is achieved. In the developed protocol, acid labile benzhydryls are used as amino-protecting groups. The polyamine backbone is assembled sequentially by reductive alkylation of the protected secondary amine with Fmoc-amino aldehydes. The protecting groups allow the use of excess of aldehyde, to avoid underivatized amines, without the risking dialkaylation of the amines, which occurs during reductive alkylations of primary amines with unhindered aliphatic aldehydes. The versatility of the method is displayed by a convenient synthesis of four analogues of a wasp toxin, philanthotoxin.

  • 400. Kabeshov, Mikhail A.
    et al.
    Kysilka, Ondřej
    Rulíšek, Lubomír
    Suleimanov, Yury V.
    Bella, Marco
    Malkov, Andrei V.
    Kočovský, Pavel
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Czech Academy of Sciences, Czech Republic; Charles University Prague, Czech Republic.
    Cross-Aldol Reaction of Isatin with Acetone Catalyzed by Leucinol: A Mechanistic Investigation2015In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, no 34, p. 12026-12033Article in journal (Refereed)
    Abstract [en]

    Comprehensive mechanistic studies on the enantioselective aldol reaction between isatin (1a) and acetone, catalyzed by L-leucinol (3a), unraveled that isatin, apart from being a substrate, also plays an active catalytic role. Conversion of the intermediate oxazolidine 4 into the reactive syn-enamine 6, catalyzed by isatin, was identified as the rate-determining step by both the calculations (G=26.1kcalmol(-1) for the analogous L-alaninol, 3b) and the kinetic isotope effect (k(H)/k(D)=2.7 observed for the reaction using [D-6]acetone). The subsequent reaction of the syn-enamine 6 with isatin produces (S)-2a (calculated G=11.6kcalmol(-1)). The calculations suggest that the overall stereochemistry is controlled by two key events: 1)the isatin-catalyzed formation of the syn-enamine 6, which is thermodynamically favored over its anti-rotamer 7 by 2.3kcalmol(-1); and 2)the high preference of the syn-enamine 6 to produce (S)-2a on reaction with isatin (1a) rather than its enantiomer (G=2.6kcalmol(-1)).

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