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  • 1051. von der Lieth, Claus-Wilhelm
    et al.
    Ardà Freire, Ana
    Blank, Dennis
    Campbell, Matthew P.
    Ceroni, Alessio
    Damerell, David R.
    Dell, Anne
    Dwek, Raymond A.
    Ernst, Beat
    Fogh, Rasmus
    Frank, Martin
    Geyer, Hildegard
    Geyer, Rudolf
    Harrison, Mathew J.
    Henrick, Kim
    Herget, Stefan
    Hull, William E.
    Ionides, John
    Joshi, Hiren J.
    Kamerling, Johannis P.
    Leeflang, Bas R.
    Lütteke, Thomas
    Lundborg, Magnus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Maass, Kai
    Merry, Anthony
    Ranzinger, René
    Rosen, Jimmy
    Royle, Louise
    Rudd, Pauline M.
    Schloissnig, Siegfried
    Stenutz, Roland
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vranken, Wim F.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Haslam, Stuart M.
    EUROCarbDB: an open-access platform for glycoinformatics2011In: Glycobiology, ISSN 0959-6658, E-ISSN 1460-2423, Vol. 21, no 4, p. 493-502Article in journal (Refereed)
    Abstract [en]

    The EUROCarbDB project is a design study for a technical framework, which provides sophisticated, freely accessible, open-source informatics tools and databases to support glycobiology and glycomic research. EUROCarbDB is a relational database containing glycan structures, their biological context and, when available, primary and interpreted analytical data from high-performance liquid chromatography, mass spectrometry and nuclear magnetic resonance experiments. Database content can be accessed via a web-based user interface. The database is complemented by a suite of glycoinformatics tools, specifically designed to assist the elucidation and submission of glycan structure and experimental data when used in conjunction with contemporary carbohydrate research workflows. All software tools and source code are licensed under the terms of the Lesser General Public License, and publicly contributed structures and data are freely accessible. The public test version of the web interface to the EUROCarbDB can be found at http://www.ebi.ac.uk/eurocarb.

  • 1052. von Langermann, Jan
    et al.
    Kaspereit, Malte
    Shakeri, Mozaffar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lorenz, Heike
    Hedberg, Martin
    Jones, Matthew J.
    Larson, Kerstin
    Herschend, Bjorn
    Arnell, Robert
    Temmel, Erik
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kienle, Achim
    Seidel-Morgenstern, Andreas
    Design of an Integrated Process of Chromatography, Crystallization and Racemization for the Resolution of 2 ',6 '-Pipecoloxylidide (PPX)2012In: Organic Process Research & Development, ISSN 1083-6160, E-ISSN 1520-586X, Vol. 16, no 2, p. 343-352Article in journal (Refereed)
    Abstract [en]

    An integrated process for the chiral separation of the industrially relevant substance 2',6'-pipecoloxylidide (PPX), an intermediate in the manufacture of a number of anesthetics, was developed. By combining three different techniques, chromatography, crystallization, and racemization, high productivity was achieved. All unit operations were executed using a common solvent system, full recycling, and a minimum of solvent exchanges or removals. The target molecule was obtained with an enantiopurity of >99.5 wt %.

  • 1053.
    Västilä, Patrik
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pastor, Isidro
    Adolfsson, Hans
    2-(Aminomethyl)-oxazolines: Highly modular scaffold for the preparation of novel asymmetric ligands2005In: Journal of Organic Chemistry, Vol. 70, no 8, p. 2921-2929Article in journal (Refereed)
  • 1054. Västilä, Patrik
    et al.
    Wettergren, Jenny
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Adolfsson, Hans
    In situ formation of ligand and catalyst- application in ruthenium-catalyzed enantioselective reduction of ketones2005In: Chemical communications, ISSN 1359-7345, no 32, p. 4039-4041Article in journal (Refereed)
  • 1055. Västilä, Patrik
    et al.
    Zaitsev, Alexey
    Wettergren, Jenny
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Privalov, Timofei
    Adolfsson, Hans
    The Importance of Alkali Cations in the [{RuCl2(p-cymene)}2]-Pseudo-dipeptide-Catalyzed Enantioselective Transfer Hydrogenation of Ketones2006In: Chemistry - A European Journal, ISSN 0947-6539, Vol. 12, no 12, p. 3218-3225Article in journal (Refereed)
  • 1056.
    Wallin, Richard
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kalek, Marcin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bartoszewicz, Agnieszka
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Thelin, Mats
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stawinski, Jacek
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    On the sulfurization of H-phosphonate diesters and phosphite triesters using elemental sulfur2009In: Phosphorus Sulfur and Silicon and the Related Elements, ISSN 1042-6507, E-ISSN 1563-5325, Vol. 184, no 4, p. 908-916Article in journal (Refereed)
  • 1057.
    Wallner, Olov
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olsson, Vilhelm J
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, L.
    Szabó, Kálmán J
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of New Chiral Pincer-Complex Catalysts for Asymmetric Allylation of Sulfonimines2006In: Inorganica Chimica Acta, ISSN 0020-1693, E-ISSN 1873-3255, Vol. 359, no 6, p. 1767-1772Article in journal (Refereed)
    Abstract [en]

    Four new chiral pincer-complexes were prepared based on coupling of BINOL and TADDOL moieties with iodoresorcinol followed by oxidative addition of palladium(0). The X-ray analysis of complex 5a revealed that the BINOL rings form a well-defined chiral pocket around the palladium atom. This chiral environment can be further modified by γ-substitution of the BINOL rings. Preliminary studies for electrophilic allylation of sulfonimine 2 with allylstannane revealed that the presented chiral complexes are promising asymmetric catalysts for preparation of chiral homoallyl amines. The best result was achieved employing catalytic amounts of γ-Me BINOL complex 6 affording homoallyl amine 4 with 59% ee and 74% isolated yield.

  • 1058.
    Wallner, Olov
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J
    Employment of Palladium Pincer-Complexes in Phenylselenylation of Organohalides2005In: Journal of Organic Chemistry, ISSN 0022-3263, Vol. 70, no 23, p. 9215-9221Article in journal (Refereed)
  • 1059.
    Wallner, Olov
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J
    Origin of the Regio- and Stereoselectivity in Palladium-Catalyzed Electrophilic Substitution via Bis-allylpalladium Complexes2003In: Chemistry : a European journal, ISSN 0947-6539, Vol. 9, no 17, p. 4025-4030Article in journal (Refereed)
  • 1060.
    Wallner, Olov
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J
    Palladium Pincer Complex-Catalyzed Allylic Stannylation with Hexaalkylditin Reagents2004In: Organic Letters, ISSN 1523-7060, Vol. 6, no 11, p. 1829-1831Article in journal (Refereed)
  • 1061.
    Wallner, Olov
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J
    Palladium-Catalyzed Electrophilic Allylic Substitution of Allyl Chlorides and Acetates via Bis-allylpalladium Intermediates2003In: Journal of Organic Chemistry, ISSN 0022-3263, Vol. 68, no 7, p. 2934-2943Article in journal (Refereed)
  • 1062.
    Wallner, Olov
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J
    Regioselective Palladium-Catalyzed Electrophilic Allylic Substitution in the Presence of Hexamethylditin2002In: Organic letters, ISSN 1523-7060, Vol. 4, no 9, p. 1563-1566Article in journal (Refereed)
  • 1063.
    Wang, Dong
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    de Wit, Martin J. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of Densely Substituted Conjugated Dienes by Transition-Metal-Free Reductive Coupling of Allenylboronic Acids and Tosylhydrazones2018In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 83, no 15, p. 8786-8792Article in journal (Refereed)
    Abstract [en]

    Tosylhydrazones and allenylboronic acids underwent a transition-metal-free reductive coupling reaction. This process is suitable for synthesis of tetra- and pentasubstituted conjugated dienes. The corresponding allenyl-Bpin substrate showed a very poor reactivity. The reaction is suggested to involve coupling of the in situ formed diazo compound and allenylboronic acid. The intermediate formed in this coupling undergoes allenyl migration followed by protodeboronation to furnish a conjugated diene as major product.

  • 1064.
    Wang, Dong
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Copper-Catalyzed, Stereoselective Cross-Coupling of Cyclic Allyl Boronic Acids with alpha-Diazoketones2017In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 19, no 7, p. 1622-1625Article in journal (Refereed)
    Abstract [en]

    In this study; we present the synthesis of new, Stereodefined allylboronic adds employed to investigate the stereochemistry of the Cu-catalyzed cross-coupling of allylboronic acids with alpha-diazoketones. According to our results, this reaction proceeds with retention of the relative configurtion of the allylberonic acid substrate. We suggest that the stereoinduction step involves a syn S(E)2'-type transrnetalation of the allylboronic acid substrate with a Cu-carbene species.

  • 1065. Wang, Lei
    et al.
    Duan, Lele
    Stewart, Beverly
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pu, Maoping
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Liu, Jianhui
    Privalov, Timofei
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Licheng
    Toward Controlling Water Oxidation Catalysis: Tunable Activity of Ruthenium Complexes with Axial Imidazole/DMSO Ligands2012In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 45, p. 18868-18880Article in journal (Refereed)
    Abstract [en]

    Using the combinations of imidazole and dimethyl :sulfoxide (DMSO) as axial ligands and 2,2'-bipyridine-6,6'-dicarboxylate (bda) as the equatorial ligand, we have synthesized six novel ruthenium complexes with noticeably different activity as water oxidation catalysts (WOCs). In four C-s symmetric Ru-II(kappa(3)-bda)(DMSO)L-2 complexes L = imidazole (1), N-methylimidazole (2), 5-methylimidazole (3), and 5-bromo-N-methylimidazole (4). Additionally, in two C-2v symmetric Ru-II(kappa(4)-bda)L-2 complexes L = 5-nitroimidazole (5) and 5-bromo-N-methylimidazole (6), that is, fully equivalent axial imidazoles. A detailed characterization of all complexes and the mechanistic investigation of the catalytic water oxidation have been carried out with a number of experimental techniques, that is, kinetics, electrochemistry and high resolution mass spectrometry (HR-MS), and density functional theory (DFT) calculations. We have observed the in situ formation: of a Ru-II-complex with the accessible seventh coordination position. The measured catalytic activities and kinetics of complex 1-6 revealed details about an important structure activity relation: the connection between the nature of axial ligands in the combination and either the increase or decrease of the catalytic activity. In particular, an axial DMSO group substantially increases the turnover frequency of WOCs reported in article, with the ruthenium-complex having one axial 5-bromo-N-methylimidazole and one axial DMSO: (4), we have obtained a high initial turnover frequency of similar to 180 s(-1). DFT modeling Of the binuclear reaction pathway of the O-O bond formation in catalytic Water oxidation further corroborated the concept of the mechanistic significance of the axial ligands and rationalized the experimentally observed difference in the activity of complexes with imidazole/DMSO and imidazole/imidazole combinations of axial ligands.

  • 1066. Wang, Zhen
    et al.
    Jiang, Wenfeng
    Liu, Jianhui
    Jiang, Weina
    Wang, Yu
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Licheng
    Pendant bases as proton transfer relays in diiron dithiolate complexes inspired by [Fe-Fe] hydrogenase active site2008In: Journal of Organometallic Chemistry, ISSN 0022-328X, Vol. 693, no 17, p. 2828-2834Article in journal (Refereed)
  • 1067. Wang, Zhen
    et al.
    Liu, Jian-Hui
    He, Cheng-Jiang
    Jiang, Shi
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Li-Cheng
    Azadithiolates cofactor of the iron-only hydrogenase and its PR3-monosubstituted derivatives: Synthesis, structure, electrochemistry and protonation2007In: Journal of Organometallic Chemistry, ISSN 0022-328X, E-ISSN 1872-8561, Vol. 692, no 24, p. 5501-5507Article in journal (Refereed)
    Abstract [en]

    The core structure (mu-SCH2)(2)NH[Fe-2(CO)(6)](5) of Fe-only hydrogenases active site model has been synthesized by the condensation of iron carbonyl sulfides, formaldehyde and silyl protected amine. Its monosubstituted complexes (mu-SCH2)(2)NH[Fe-2(CO)(5)PR3] (R = Ph (6), Me (7)) were accordingly prepared. The coordination configurations of 5 and 6 were characterized by X-ray crystallography. Protonation of complex 7 to form the N-protonated product occurs in an acetonitrile solution upon addition of triflic acid. The redox properties of these model complexes were studied by cyclic voltammetry.

  • 1068. Wang, Zhen
    et al.
    Liu, Jianhui
    He, Chengjiang
    Jiang, Shi
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Licheng
    Diiron azadithiolates with hydrophilic phosphatriazaadamantane ligand as iron-only hydrogenase active site models: Synthesis, structure, and electrochemical study2007In: Inorganica Chimica Acta, ISSN 0020-1693, E-ISSN 1873-3255, Vol. 360, no 7, p. 2411-2419Article in journal (Refereed)
    Abstract [en]

    Three novel complexes (mu-adt)[Fe-2(CO)(5)PTA] (2-PTA), (mu-adt)[Fe-2(CO)(4)PTA(2)](2-PTA(2)) and (mu-adt)[Fe-2(CO)(5)DAPTA] (2-DAPTA), where adt is SCH2N(CH2CH2CH3)CH2S, PTA stands for 1,3,5-triaza-7-phosphaadamantane and DAPTA is 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane, were prepared as the models of the iron hydrogenase active site through controlled CO displacement of (mu-adt)[Fe-2(CO)(6)] with PTA and DAPTA. The coordination configurations of 2-PTA and 2-PTA(2) were characterized by X-ray crystallography. The disubstituted diiron complex 2-PTA(2) features a basal/apical coordination mode, instead of the typical transoid basal/basal configuration. Protonation of three complexes only occurred at the bridging-N atom, rather than at the tertiary nitrogen atom on the PTA or DAPTA ligands. Electrochemical properties of the complexes were studied in acetonitrile or a mixture of acetonitrile and water in the presence of acetic acid, by cyclic voltammetry. The current sensitivity of the reduced species to acid concentration in the presence of H2O is greater than in the pure CH3CN solution.

  • 1069. Wangsell, Fredrik
    et al.
    Gustafsson, Karin
    Kvarnström, Ingemar
    Borkakoti, Neera
    Edlund, Michael
    Jansson, Katarina
    Lindberg, Jimmy
    Hallberg, Anders
    Rosenquist, Asa
    Samuelsson, Bertil
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of potent BACE-1 inhibitors incorporating a hydroxyethylene isostere as central core2010In: European Journal of Medicinal Chemistry, ISSN 0223-5234, E-ISSN 1768-3254, Vol. 45, no 3, p. 870-882Article in journal (Refereed)
    Abstract [en]

    We herein describe the design and synthesis of a series of BACE-1 inhibitors incorporating a P1-substituted hydroxyl ethylene transition state isostere. The synthetic route starting from commercially available carbohydrates yielded a pivotal lactone intermediate with excellent stereochemical control which subsequently could be diversified at the PI-position. The final inhibitors were optimized using three different amines to provide the residues in the P2'-P3' position and three different acids affording the residues in the P2-P3 position. In addition we report on the stereochemical preference of the P1'-methyl substituent in the synthesized inhibitors. All inhibitors were evaluated in an in vitro BACE-I assay where the most potent inhibitor, 34-(R), exhibited a BACE-1 IC50 Value of 3.1 nM.

  • 1070. Wangsell, Fredrik
    et al.
    Nordeman, Patrik
    Savmarker, Jonas
    Emanuelsson, Rikard
    Jansson, Katarina
    Lindberg, Jimmy
    Rosenquist, Asa
    Samuelsson, Bertil
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Larhed, Mats
    Investigation of alpha-phenylnorstatine and alpha-benzylnorstatine as transition state isostere motifs in the search for new BACE-1 inhibitors2011In: Bioorganic & Medicinal Chemistry, ISSN 0968-0896, E-ISSN 1464-3391, Vol. 19, no 1, p. 145-155Article in journal (Refereed)
    Abstract [en]

    Inhibition of the BACE-1 protease enzyme has over the recent decade developed into a promising drug strategy for Alzheimer therapy. In this report, more than 20 new BACE-1 protease inhibitors based on alpha-phenylnorstatine, alpha-benzylnorstatine, iso-serine, and beta-alanine moieties have been prepared. The inhibitors were synthesized by applying Fmoc solid phase methodology and evaluated for their inhibitory properties. The most potent inhibitor, tert-alcohol containing (R)-12 (IC(50) = 0.19 mu M) was co-crystallized in the active site of the BACE-1 protease, furnishing a novel binding mode in which the N-terminal amine makes a hydrogen bond to one of the catalytic aspartic acids.

  • 1071.
    Warner, Madeleine C.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Racemization of Olefinic Alcohols by a Carbonyl(cyclopentadienyl)ruthenium Complex: Inhibition by the Carbon-Carbon Double Bond2015In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, no 11, p. 2388-2393Article in journal (Refereed)
    Abstract [en]

    In this article, racemization of various olefinic sec-alcohols by Ru(CO)(2)((5)-C5Ph5)Cl was investigated. The racemization of three aliphatic sec-alcohols with different chain lengths containing terminal double bonds was studied. A dramatic decrease of the racemization rate was found for these sec-alcohols compared to that of the corresponding saturated substrates. The slow racemization rate of the former alcohols is ascribed to coordination of the double bond to the ruthenium centre, which blocks the free site needed for -hydride elimination. This mechanism was supported by a recent study, in which 5-hexen-2-ol was found to form an alkoxycarbonyl complex having the double bond coordinated to the ruthenium atom. Aliphatic sec-alcohol substrates with a di- or trisubstituted double bond were found to give a lower degree of inhibition of the racemization rate than the substrates with a monosubstituted double bond.

  • 1072.
    Warner, Madeleine C.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nagendiran, Anuja
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bogár, Krisztián
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantioselective Route to Ketones and Lactones from Exocyclic Allylic Alcohols via Metal and Enzyme Catalysis2012In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 14, no 19, p. 5094-5097Article in journal (Refereed)
    Abstract [en]

    A general and efficient route for the synthesis of enantiomerically pure a-substituted ketones and the corresponding lactones has been developed. Ruthenium- and enzyme-catalyzed dynamic kinetic resolution (DKR) with a subsequent Cu-catalyzed alpha-allylic substitution are the key steps of the route. The a-substituted ketones were obtained in high yields and with excellent enantiomeric excess. The methodology was applied to the synthesis of a naturally occurring caprolactone, (R)-10-methyl-6-undecanolide, via a subsequent Baeyer-Villiger oxidation.

  • 1073.
    Warner, Madeleine C.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shevchenko, Grigory A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Jouda, Suzan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bogar, Krisztian
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dynamic Kinetic Resolution of Homoallylic Alcohols: Application to the Synthesis of Enantiomerically Pure 5,6-Dihydropyran-2-ones and delta-Lactones2013In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, no 41, p. 13859-13864Article in journal (Refereed)
    Abstract [en]

    Dynamic kinetic resolution of various homoallylic alcohols with the use of Candida antarctica lipaseB and ruthenium catalyst 2 afforded homoallylic acetates in high yields and with high enantioselectivity. These enantiopure acetates were further transformed into homoallylic acrylates after hydrolysis of the ester function and subsequent DMAP-catalyzed esterification with acryloyl chloride. After ring-closing metathesis 5,6-dihydropyran-2-ones were obtained in good yields. Selective hydrogenation of the carboncarbon double bond afforded the corresponding -lactones without loss of chiral information.

  • 1074.
    Warner, Madeleine C
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    CO dissociation mechanism in racemization of alcohols by a cyclopentadienyl ruthenium dicarbonyl catalyst2011In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 133, no 9, p. 2820-2823Article in journal (Refereed)
    Abstract [en]

    13CO exchange studies of racemization catalyst (η5-Ph5C5)Ru(CO)2Cl and (η5-Ph5C5)Ru(CO)2(Ot-Bu) by 13C NMR spectroscopy are reported. CO exchange for the active catalyst form, (η5-Ph5C5)Ru(CO)2(Ot-Bu) is approximately 20 times faster than that for the precatalyst (η5-Ph5C5)Ru(CO)2Cl. An inhibition on the rate of racemization of (S)-1-phenylethanol was observed on addition of CO. These results support the hypothesis that CO dissociation is a key step in the racemization of sec-alcohols by (η5-Ph5C5)Ru(CO)2Cl, as also predicted by DFT calculations.

  • 1075. Watcharinyanon, Somsakul
    et al.
    Puglia, Carla
    Göthelid, Emmanuelle
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Moons, Ellen
    Johansson, Lars S.O.
    Molecular orientation of thiol-derivatized tetraphenylporphyrin on gold studied by XPS and NEXAFS2009In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 603, no 7, p. 1026-1033Article in journal (Refereed)
  • 1076. Wei, Wen-Jie
    et al.
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Liao, Rong-Zhen
    Theoretical Study of the Mechanism of the Nonheme Iron Enzyme EgtB2017In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 56, no 6, p. 3589-3599Article in journal (Refereed)
    Abstract [en]

    EgtB is a nonheme iron enzyme catalyzing the C - S bond formation between gamma-glutamyl cysteine (gamma GC) and N-alpha-trimethyl histidine (TMH) in the ergothioneine biosynthesis. Density functional calculations were performed to elucidate and delineate the reaction mechanism of this enzyme. Two different mechanisms were considered, depending on whether the sulfoxidation or the S C bond formation takes place first. The calculations suggest that the S - O bond formation occurs first between the thiolate and the ferric superoxide, followed by homolytic O-O bond cleavage, very similar to the case of cysteine dioxygenase. Subsequently, proton transfer from a second-shell residue Tyr377 to the newly generated iron - oxo moiety takes place, which is followed by proton transfer from the TMH imidazole to Tyr377, facilitated by two crystallographically observed water molecules. Next, the S C bond is formed between gamma GC and TMH, followed by proton transfer from the imidazole CH moiety to Tyr377, which was calculated to be the rate-limiting step for the whole reaction, with a barrier of 17.9 kcal/mol in the quintet state. The calculated barrier for the rate-limiting step agrees quite well with experimental kinetic data. Finally, this proton is transferred back to the imidazole nitrogen to form the product. The alternative thiyl radical attack mechanism has a very high barrier, being 25.8 kcal/mol, ruling out this possibility.

  • 1077. Wellens, Adinda
    et al.
    Garofalo, Corinne
    Nguyen, Hien
    Van Gerven, Nani
    Slättegård, Rikard
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hernalsteens, Jean-Pierre
    Wyns, Lode
    Oscarson, Stefan
    De Greve, Henri
    Hultgren, Scott
    Bouckaert, Julie
    Intervening with urinary tract infections using anti-adhesives based on the crystal structure of the FimH-oligomannose-3 complex2008In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 3, no 4, p. e2040; 1-13Article in journal (Refereed)
  • 1078.
    Wettergren, Jenny
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Buitrago, Elina
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ryberg, Per
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mechanistic Investigation on the Asymmetric Transfer Hydrogenation of Ketones Catalyzed by Pseudo-Dipeptides Ruthenium complexes2009In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 23, p. 5709-5718Article in journal (Refereed)
    Abstract [en]

    Lithium-powered: A kinetic investigation into the asymmetric transfer hydrogenation of non-activated aryl alkyl ketones, catalyzed by N-Boc-protected -amino acid hydroxyamide ruthenium–arene complexes, has revealed that the reactions proceed through an unprecedented bimetallic outer-sphere mechanism. Under optimized conditions, these catalysts provide access to secondary alcohols in high yields and with excellent enantioselectivities (>99 % ee).

    The combination of N-Boc-protected -amino acid hydroxyamides (pseudo-dipeptides) and [{Ru(p-cymene)Cl2}2] resulted in the formation of superior catalysts for the asymmetric transfer hydrogenation (ATH) of non-activated aryl alkyl ketones in propan-2-ol. The overall kinetics of the ATH of acetophenone to form 1-phenylethanol in the presence of ruthenium pseudo-dipeptide catalysts were studied, and the individual rate constants for the processes were determined. Addition of lithium chloride to the reaction mixtures had a strong influence on the rates and selectivities of the processes. Kinetic isotope effects (KIEs) for the reduction were determined and the results clearly show that the hydride transfer is rate-determining, whereas no KIEs were detected for the proton transfer. From these observations a novel bimetallic outer-sphere-type mechanism for these ATH process is proposed, in which the bifunctional catalysts mediate the transfer of a hydride and an alkali metal ion between the hydrogen donor and the substrate. Furthermore, the use of a mixture of propan-2-ol and THF (1:1) proved to enhance the rates of the ATH reactions. A series of aryl alkyl ketones were reduced under these conditions in the presence of 0.5 mol % of catalyst, and the corresponding secondary alcohols were formed in high yields and with excellent enantioselectivities (>99 % ee) in short reaction times.

  • 1079.
    Wettergren, Jenny
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Buitrago, Elina
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ryberg, Per
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mechanistic investigations into the asymmetric transfer hydrogenation of ketones catalyzed by pseudo-dipeptide ruthenium complexes2009In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 23, p. 5709-5718Article in journal (Refereed)
  • 1080.
    Wettergren, Jenny
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bøgevig, Anders
    Portier, Maude
    Adolfsson, Hans
    Ruthenium-Catalyzed Enantioselective Reduction of Electron-Rich Aryl Alkyl Ketones2006In: Advanced Synthesis and Catalysis, ISSN 1615-4150, Vol. 348, no 10-11, p. 1277-1282Article in journal (Refereed)
  • 1081.
    Wettergren, Jenny
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zaitsev, Alexey
    Adolfsson, Hans
    Rhodium-Catalyzed Asymmetric Transfer Hydrogenation of Aryl Alkyl Ketones Employing Ligands Derived from Amino Acids2007In: Advanced Synthesis and Catalysis, ISSN 1615-4150, Vol. 349, no 17-18, p. 2556-2562Article in journal (Refereed)
  • 1082.
    Wettergren, Jenny
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zaitsev, Alexey B.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rhodium-catalyzed asymmetric transfer hydrogenation of aryl alkyl ketones employing ligands derived from amino acids2007In: Advanced Synthesis & Catalysis, ISSN 1615-4150, Vol. 349, p. 2556-2562Article in journal (Refereed)
  • 1083.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    A perspective on the primary and three-dimensional structures of carbohydrates2013In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 378, p. 123-132Article in journal (Refereed)
    Abstract [en]

    Carbohydrates, in more biologically oriented areas referred to as glycans, constitute one of the four groups of biomolecules. The glycans, often present as glycoproteins or glycolipids, form highly complex structures. In mammals ten monosaccharides are utilized in building glycoconjugates in the form of oligo-(up to about a dozen monomers) and polysaccharides. Subsequent modifications and additions create a large number of different compounds. In bacteria, more than a hundred monosaccharides have been reported to be constituents of lipopolysaccharides, capsular polysaccharides, and exopolysaccharides. Thus, the number of polysaccharide structures possible to create is huge. NMR spectroscopy plays an essential part in elucidating the primary structure, that is, monosaccharide identity and ring size, anomeric configuration, linkage position, and sequence, of the sugar residues. The structural studies may also employ computational approaches for NMR chemical shift predictions (CASPER program). Once the components and sequence of sugar residues have been unraveled, the three-dimensional arrangement of the sugar residues relative to each other (conformation), their flexibility (transitions between and populations of conformational states), together with the dynamics (timescales) should be addressed. To shed light on these aspects we have utilized a combination of experimental liquid state NMR techniques together with molecular dynamics simulations. For the latter a molecular mechanics force field such as our CHARMM-based PARM22/SU01 has been used. The experimental NMR parameters acquired are typically H-1, H-1 cross-relaxation rates (related to NOEs), (3)JCH and (3)JCC trans-glycosidic coupling constants and H-1, C-13-and H-1, H-1-residual dipolar couplings. At a glycosidic linkage two torsion angles phi and psi are defined and for 6-substituted residues also the omega torsion angle is required. Major conformers can be identified for which highly populated states are present. Thus, in many cases a well-defined albeit not rigid structure can be identified. However, on longer timescales, oligosaccharides must be considered as highly flexible molecules since also anti-conformations have been shown to exist with H-C-O-C torsion angles of similar to 180 degrees, compared to syn-conformations in which the protons at the carbon atoms forming the glycosidic linkage are in close proximity. The accessible conformational space governs possible interactions with proteins and both minor changes and significant alterations occur for the oligosaccharides in these interaction processes. Transferred NOE NMR experiments give information on the conformation of the glycan ligand when bound to the proteins whereas saturation transfer difference NMR experiments report on the carbohydrate part in contact with the protein. It is anticipated that the subtle differences in conformational preferences for glycan structures facilitate a means to regulate biochemical processes in different environments. Further developments in the analysis of glycan structure and in particular its role in interactions with other molecules, will lead to clarifications of the importance of structure in biochemical regulation processes essential to health and disease.

  • 1084. Wieczorek, Birgit
    et al.
    Träff, Annika
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Krumlinde, Patrik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dijkstra, Harm P.
    Egmond, Maarten R.
    van Koten, Gerard
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Klein Gebbink, Robertus J. M.
    Covalent anchoring of a racemization catalyst to CALB-beads: towards dual immobilization of DKR catalysts2011In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 52, no 14, p. 1601-1604Article in journal (Refereed)
    Abstract [en]

    The preparation of a heterogeneous bifunctional catalytic system, combining the catalytic properties of an organometallic catalyst (racemization) with those of an enzyme (enantioselective acylation) is described. A novel ruthenium phosphonate inhibitor was synthesized and covalently anchored to a lipase immobilized on a solid support (CALB, Novozym® 435). The immobilized bifunctional catalytic system showed activity in both racemization of (S)-1-phenylethanol and selective acylation of 1-phenylethanol.

  • 1085.
    Wikmark, Ylva
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Engelmark Cassimjee, Karim
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lihammar, Richard
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Removing the Active-Site Flap in Lipase A from Candida antarctica Produces a Functional Enzyme without Interfacial Activation2016In: ChemBioChem (Print), ISSN 1439-4227, E-ISSN 1439-7633, Vol. 17, no 2, p. 141-145Article in journal (Refereed)
    Abstract [en]

    A mobile region is proposed to be a flap that covers the active site of Candida antarctica lipase A. Removal of the mobile region retains the functional properties of the enzyme. Interestingly interfacial activation, required for the wild-type enzyme, was not observed for the truncated variant, although stability, activity, and stereoselectivity were very similar for the wild-type and variant enzymes. The variant followed classical Michaelis-Menten kinetics, unlike the wild type. Both gave the same relative specificity in the transacylation of a primary and a secondary alcohol in organic solvent. Furthermore, both showed the same enantioselectivity in transacylation of alcohols and the hydrolysis of alcohol esters, as well as in the hydrolysis of esters chiral at the acid part.

  • 1086.
    Wikmark, Ylva
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Humble, Maria Svedendahl
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Combinatorial Library Based Engineering of Candida antarctica Lipase A for Enantioselective Transacylation of sec-Alcohols in Organic Solvent2015In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 54, no 14, p. 4284-4288Article in journal (Refereed)
    Abstract [en]

    A method for determining lipase enantioselectivity in the transacylation of sec-alcohols in organic solvent was developed. The method was applied to a model library of Candida antarctica lipase A (CalA) variants for improved enantioselectivity (E values) in the kinetic resolution of 1-phenylethanol in isooctane. A focused combinatorial gene library simultaneously targeting seven positions in the enzyme active site was designed. Enzyme variants were immobilized on nickel-coated 96-well microtiter plates through a histidine tag (His6 -tag), screened for transacylation of 1-phenylethanol in isooctane, and analyzed by GC. The highest enantioselectivity was shown by the double mutant Y93L/L367I. This enzyme variant gave an E value of 100 (R), which is a dramatic improvement on the wild-type CalA (E=3). This variant also showed high to excellent enantioselectivity for other secondary alcohols tested.

  • 1087. Wojcik, Anna
    et al.
    Broclawik, Ewa
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lundberg, Marcus
    Moran, Graham
    Borowski, Tomasz
    Role of Substrate Positioning in the Catalytic Reaction of 4-Hydroxyphenylpyruvate Dioxygenase-A QM/MM Study2014In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 136, no 41, p. 14472-14485Article in journal (Refereed)
    Abstract [en]

    Ring hydroxylation and coupled rearrangement reactions catalyzed by 4-hydroxyphenylpyruvate dioxygenase were studied with the QM/MM method ONIOM(B3LYP:AMBER). For electrophilic attack of the ferryl species on the aromatic ring, five channels were considered: attacks on the three ring atoms closest to the oxo ligand (C1, C2, C6) and insertion of oxygen across two bonds formed by them (C1-C2, C1-C6). For the subsequent migration of the carboxymethyl substituent, two possible directions were tested (C1-C2, C1-C6), and two different mechanisms were sought (stepwise radical, single-step heterolytic). In addition, formation of an epoxide (side)product and benzylic hydroxylation, as catalyzed by the closely related hydroxymandelate synthase, were investigated. From the computed reaction free energy profiles it follows that the most likely mechanism of 4-hydroxyphenylpyruvate dioxygenase involves electrophilic attack on the C1 carbon of the ring and subsequent single-step heterolytic migration of the substituent. Computed values of the kinetic isotope effect for this step are inverse, consistent with available experimental data. Electronic structure arguments for the preferred mechanism of attack on the ring are also presented.

  • 1088.
    Wolpher, Henriette
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Borgström, Magnus
    Hammarström, Leif
    Bergquist, Jonas
    Sundström, Villy
    Styring, Stenbjörn
    Sun, Licheng
    Åkermark, Björn
    Synthesis and Properties of an Iron Hydrogenase Active Site Model Linked to Ruthenium tris-Bipyridine Photosensitizer2003In: Inorganic Chemical Communications, Vol. 6, p. 989-991Article in journal (Refereed)
  • 1089. Wolpher, Henriette
    et al.
    Johansson, Olof
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Abrahamsson, Maria
    Kritikos, Mikael
    Sun, Licheng
    Åkermark, Björn
    A tridentate ligand for preparation of bisterpyridine-like ruthenium(II) complexes with an increased excited state lifetime2004In: Inorganic Chemistry Communications, ISSN 1387-7003, Vol. 7, no 3, p. 337-340Article in journal (Refereed)
  • 1090.
    Wolpher, Henriette
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johansson, Olof
    Abrahamsson, Maria
    Kritikos, Mikael
    Sun, Licheng
    Åkermark, Björn
    A tridentate ligand for preparation of bisterpyridine-like ruthenium(II) complexes with an increased excited state lifetime2004In: Inorganic Chemistry Communications, ISSN 1387-7003, Vol. 7, no 3, p. 337-340Article in journal (Refereed)
  • 1091.
    Wolpher, Henriette
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sinha, Subrata
    Pan, Jingxi
    Johansson, Anh
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lundqvist, Maria J.
    Persson, Petter
    Lomoth, Reiner
    Bergquist, Jonas
    Sun, Licheng
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sundström, Villy
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Polívka, Tomás
    Synthesis and electron transfer studies of ruthenium-terpyridine-based dyads attached to nanostructured TiO22007In: Inorganic Chemistry, ISSN 0020-1669, Vol. 46, no 3, p. 638-651Article in journal (Refereed)
  • 1092. Wu, Emilia L.
    et al.
    Engström, Olof
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Jo, Sunhwan
    Stuhlsatz, Danielle
    Yeom, Min Sun
    Klauda, Jeffery B.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Im, Wonpil
    Molecular Dynamics and NMR Spectroscopy Studies of E. coli Lipopolysaccharide Structure and Dynamics2013In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 105, no 6, p. 1444-1455Article in journal (Refereed)
    Abstract [en]

    Lipopolysaccharide (LPS), a component of Gram-negative bacterial outer membranes, comprises three regions: lipid A, core oligosaccharide, and O-antigen polysaccharide. Using the CHARMM36 lipid and carbohydrate force fields, we have constructed a model of an Escherichia coil R1 (core) 06 (antigen) LPS molecule. Several all-atom bilayers are built and simulated with lipid A only (LIPA) and varying lengths of 0 (LPS0), 5 (LPS5), and 10 (LPS10) O6 antigen repeating units; a single unit of 06 antigen contains five sugar residues. From H-1,H-1-NOESY experiments, cross-relaxation rates are obtained from an O-antigen polysaccharide sample. Although some experimental deviations are due to spin-diffusion, the remaining effective proton-proton distances show generally very good agreement between NMR experiments and molecular dynamics simulations. The simulation results show that increasing the LPS molecular length has an impact on LPS structure and dynamics and also on LPS bilayer properties. Terminal residues in a LPS bilayer are more flexible and extended along the membrane normal. As the core and O-antigen are added, per-lipid area increases and lipid bilayer order decreases. In addition, results from mixed LPS0/5 and LPS0/10 bilayer simulation's show that the LPS O-antigen conformations at a higher concentration of LPS5 and LPS10 are more orthogonal to the membrane and less flexible. The O-antigen concentration of mixed LPS bilayers does not have a significant effect on per-lipid area and hydrophobic thickness. Analysis of ion and water penetration shows that water molecules can penetrate inside the inner core region, and hydration is critical to maintain the integrity of the bilayer structure.

  • 1093. Wu, Emilia L.
    et al.
    Fleming, Patrick J.
    Yeom, Min Sun
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Klauda, Jeffery B.
    Fleming, Karen G.
    Im, Wonpil
    E. coil Outer Membrane and Interactions with OmpLA2014In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 106, no 11, p. 2493-2502Article in journal (Refereed)
    Abstract [en]

    The outer membrane of Gram-negative bacteria is a unique asymmetric lipid bilayer composed of phospholipids (PLs) in the inner leaflet and lipopolysaccharides (LPSs) in the outer leaflet. Its function as a selective barrier is crucial for the survival of bacteria in many distinct environments, and it also renders Gram-negative bacteria more resistant to antibiotics than their Gram-positive counterparts. Here, we report the structural properties of a model of the Escherichia coli outer membrane and its interaction with outer membrane phospholipase A (OmpLA) utilizing molecular dynamics simulations. Our results reveal that given the lipid composition used here, the hydrophobic thickness of the outer membrane is similar to 3 angstrom thinner than the corresponding PL bilayer, mainly because of the thinner LPS leaflet. Further thinning in the vicinity of OmpLA is observed due to hydrophobic matching. The particular shape of the OmpLA barrel induces various interactions between LPS and PL leaflets, resulting in asymmetric thinning around the protein. The interaction between OmpLA extracellular loops and LPS (headgroups and core oligosaccharides) stabilizes the loop conformation with reduced dynamics, which leads to secondary structure variation and loop displacement compared to that in a DLPC bilayer. In addition, we demonstrate that the LPS/PL ratios in asymmetric bilayers can be reliably estimated by the per-lipid surface area of each lipid type, and there is no statistical difference in the overall membrane structure for the outer membranes with one more or less LPS in the outer leaflet, although individual lipid properties vary slightly.

  • 1094. Wångsell, Fredrik
    et al.
    Russo, Francesco
    Sävmarker, Jonas
    Åsa, Rosenquist
    Samuelsson, Bertil
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Larhed, Mats
    Design and synthesis of BACE-1 inhibitors utilizing a tertiary hydroxyl motif as the transition state mimic2009In: Bioorganic & Medicinal Chemistry Letters, ISSN 0960-894X, Vol. 19, no 16, p. 4711-4714Article in journal (Refereed)
  • 1095. Xia, Ming
    et al.
    Liu, Jianhui
    Gao, Yan
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Licheng
    Synthesis and photophysical and electrochemical study of tyrosine covalently linked to high-valent copper(III) and manganese(IV) complexes2007In: Helvetica Chimica Acta, ISSN 0018-019X, Vol. 90, no 3, p. 553-561Article in journal (Refereed)
  • 1096.
    Xu, Chao
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Deiana, Luca
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Afewerki, Samson
    Incerti-Pradillos, Celia
    Córdova, Oscar
    Guo, Peng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Mid-Sweden University, Sweden.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    The Use of Porous Palladium(II)-polyimine in Cooperatively-catalyzed Highly Enantioselective Cascade Transformations2015In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 357, no 9, p. 2150-2156Article in journal (Refereed)
    Abstract [en]

    Porous organic polymers have prospects as functional substrates for catalysis, with quite different molecular properties from inorganic substrates. Here we disclose for the first time that porous palladium(II)-polyimines are excellent catalysts for cooperatively catalyzed and enantioselective cascade reactions. In synergy with a chiral amine co-catalyst, polysubstituted cyclopentenes and spirocyclic oxindoles, including the all-carbon quaternary stereocenter, were synthesized in high yields. High diastereo- and enantioselectivities were achieved for these dynamic kinetic asymmetric transformations (DYKAT) of enals with propargylic nucleophiles.

  • 1097.
    Xu, Quan
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kerdphon, Sutthichat
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Andersson, Pher G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    C-C Coupling of Ketones with Methanol Catalyzed by a N-Heterocyclic Carbene-Phosphine Iridium Complex2015In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, p. 3576-3579Article in journal (Refereed)
    Abstract [en]

    An N-heterocyclic carbene–phosphine iridium complex system was found to be a very efficient catalyst for the methylation of ketone via a hydrogen transfer reaction. Mild conditions together with low catalyst loading (1 mol %) were used for a tandem process which involves the dehydrogenation of methanol, CC bond formation with a ketone, and hydrogenation of the new generated double bond by iridium hydride to give the alkylated product. Using this iridium catalyst system, a number of branched ketones were synthesized with good to excellent conversions and yields.

  • 1098. Xu, Yunhua
    et al.
    Duan, Lele
    Tong, Lianpeng
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Licheng
    Visible light-driven water oxidation catalyzed by a highly efficient dinuclear ruthenium complex2010In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 46, no 35, p. 6506-6508Article in journal (Refereed)
  • 1099.
    Xu, Yunhua
    et al.
    Royal Institute of Technology (KTH).
    Duan, Lele
    Royal Institute of Technology (KTH).
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Tong, Lianpeng
    Royal Institute of Technology (KTH).
    Lee, Bao-Lin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhang, Rong
    Dalian University of Technology (DUT), (P.R. China).
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Licheng
    Royal Institute of Technology (KTH), Department of Organic Chemistry.
    Synthesis and catalytic water oxidation activities of ruthenium complexes containing neutral ligands2011In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 34, p. 9520-9528Article in journal (Refereed)
    Abstract [en]

    Two dinuclear and one mononuclear ruthenium complexes containing neutral polypyridyl ligands have been synthesised as pre-water oxidation catalysts and characterised by 1H and 13C NMR spectroscopy and ESI-MS. Their catalytic water oxidation properties in the presence of [Ce-(NH4)2(NO3)6] (CeIV) as oxidant at pH 1.0 have been investigated. At low concentrations of CeIV (5 mM), high turnover numbers of up to 4500 have been achieved. An 18O-labelling experiment established that both O atoms in the evolved O2 originate from water. Combined electrochemical study and electrospray ionisation mass spectrometric analysis suggest that ligand exchange between coordinated 4-picoline and free water produces Ru aquo species as the real water oxidation catalysts.

  • 1100. Xu, Yunhua
    et al.
    Fischer, Andreas
    Duan, Lele
    Tong, Lianpeng
    Gabrielsson, Erik
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Licheng
    Chemical and light-driven oxidation of water catalyzed by an efficient dinuclear ruthenium complex2010In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 49, no 47, p. 8934-8937Article in journal (Refereed)
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