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  • 1.
    Ahlford, Katrin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lind, Jesper
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Mäler, Lena
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rhodium-catalyzed asymmetric transfer hydrogenation of alkyl and aryl ketones in aqueous media2008In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 10, no 8, p. 832-835Article in journal (Refereed)
    Abstract [en]

    A novel lipophilic rhodium catalyst was evaluated in the enantioselective transfer hydrogenation of ketones in water using sodium formate as the hydride donor, and in the presence of sodium docecylsulfonate. Alkyl alkyl ketones were reduced in good yields and in moderate to good enantioselectivities, and the reduction of aryl alkyl ketones proceeded with excellent enantioselectivity (up to 97% ee).

  • 2.
    Andersson, Linnéa
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry. Oorganisk kemi.
    Exploring expandable microspheres as a novel pore former in gel-cast macroporous alumina2008Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Expandable microspheres have been explored as sacrificial templates for the production of macroporous ceramics. Concentrated alumina powder suspensions that contain expandable microspheres have been consolidated by gel-casting. The temperature range for the setting of the monomers and cross-linkers in the gel-casting system was tailored to allow the gas-filled polymer spheres to expand before the surrounding powder body became rigid. It has been demonstrated that it is possible to tune and tailor the porosity up to 86 % and the pore size distribution from 15 up to 150 micrometers by controlling the amount and size of the expandable microspheres. Scanning electron microscopy showed that the porosity became more and more open as the total porosity increased. This was corroborated by a preliminary study by X-ray µ Computed Tomography, which showed a very high connectivity between the pores, in a macroporous alumina body with a high porosity. The connectivity was reduced when alumina particles were deposited as a homogenous coating of on the expandable microspheres by a layer-by-layer coating process. The expandable microspheres has the advantage that a relatively low amount of organic material results in a large pore volume, which allow rapid and facile burn-out. It was demonstrated that the temperature induced expansion of the microspheres, and the associated increase of the suspension volume could be used as a novel casting method to yield macroporous alumina bodies with complex shapes. Ceramics produced with this method could find application ranging from bone scaffolds to low mass kiln furniture.

  • 3.
    Aydin, Juhanes
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantioselective palladium pincer complex catalyzed carbon carbon coupling reactions between tosylimines and various nucleophiles2008In: Abstracts of Papers, 236th ACS National Meeting, Philadelphia, PA, United States, August 17-21, 2008, Washington, DC: American Chemical Society , 2008Conference paper (Other academic)
  • 4.
    Aydin, Juhanes
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mechanistic considerations for the enantioselective palladium pincer complex catalyzed carbon-carbon coupling reactions2008In: Abstracts of Papers, 236th ACS National Meeting, Philadelphia, PA, United States, August 17-21, 2008, Washington, DC: American Chemical Society , 2008Conference paper (Other academic)
  • 5.
    Ayesa Alvarez, Susana
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Design and Synthesis of Amine Building Blocks and Protease Inhibitors2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The first part of this thesis addresses the design and synthesis of amine building blocks accomplished by applying two different synthetic procedures, both of which were developed using solid-phase chemistry. Chapter 1 presents the first of these methods, entailing a practical solid-phase parallel synthesis route to N-monoalkylated aminopiperidines and aminopyrrolidines achieved by selective reductive alkylation of primary and/or secondary amines. Solid-phase NMR spectroscopy was used to monitor the reactions for which a new pulse sequence was developed. The second method, reported in Chapter 2, involves a novel approach to the synthesis of secondary amines starting from reactive alkyl halides and azides. The convenient solid-phase protocol that was devised made use of the Staudinger reaction in order to accomplish highly efficient alkylations of N-alkyl phosphimines or N-aryl phosphimines with reactive alkyl halides.

    The second part of the thesis describes the design and synthesis of three classes of protease inhibitors targeting the cysteine proteases cathepsins S and K, and the serine protease hepatitis C virus (HCV) NS3 protease. Chapter 4 covers the design, solid-phase synthesis, and structure-activity relationships of 4-amidofurane-3-one P1-containing inhibitors of cathepsin S and the effects of P3 sulfonamide groups on the potency and selectivity towards related cathepsin proteases. This work resulted in the discovery of highly potent and selective inhibitors of cathepsin S. Two parallel solid-phase approaches to the synthesis of a series of aminoethylamide inhibitors of cathepsin K are presented in Chapter 5. Finally, Chapter 6 reports peptide-based HCV NS3 protease inhibitors containing a non-electrophilic allylic alcohol moiety as P1 group and also outlines efforts to incorporate this new template into low-molecular-weight drug-like molecules.

  • 6.
    Ayesa, Susana
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Samuelsson, Bertil
    Classon, Björn
    A One-Pot, Solid-Phase Synthesis of Secondary Amines from Reactive Alkyl Halides and an Alkyl Azide2008In: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry, ISSN 0936-5214, E-ISSN 1437-2096, no 1, p. 77-79Article in journal (Refereed)
  • 7.
    Bartoszewicz, Agnieszka
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Livendahl, Madeleine
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of b-Hydroxy Ketones from Allylic Alcohols via Catalytic Formation of Ruthenium Enolates2008In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 14, no 34, p. 10547-10550Article in journal (Refereed)
    Abstract [en]

    The most efficient Ru-catalyzed isomerization–aldol reaction from allylic alcohols has been achieved by using [η5-(Ph5Cp)Ru(CO)2Cl] as the catalyst. The bulky pentaphenylcyclopentadienyl ligand on the ruthenium atom prevents protonation at the oxygen of the Ru–enolate intermediate and completely suppresses the formation of unwanted ketone byproducts (see scheme). The domino transformation is as good as it can be: aldols are obtained in quantitative yields at ambient temperature.

  • 8.
    Bielawski, Marcin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient and High-Yielding Routes to Diaryliodonium Salts2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis summarizes three novel and general reaction protocols for the synthesis of diaryliodonium salts. All protocols utilize mCPBA as oxidant and the acids used are either TfOH, to obtain triflate salts, or BF3•Et2O that gives the corresponding tetrafluoroborate salts in situ.

    Chapter two describes the reaction of various arenes and aryl iodides, delivering electron-rich and electron-deficient triflates in moderate to excellent yields.

    In chapter three, it is shown that the need of aryl iodides can be circumvented, as molecular iodine can be used together with arenes in a direct one-pot, three-step synthesis of symmetric diaryliodonium triflates.

    The final and fourth chapter describes the development of a sequential one-pot reaction from aryl iodides and boronic acids, delivering symmetric and unsymmetric, electron-rich and electron-deficient iodonium tetrafluoroborates in moderate to excellent yields. This protocol was developed to overcome mechanistic limitations existing in the protocols described in chapter two and three.

    The methodology described in this thesis is the most general, efficient and high-yielding existing up to date, making diaryliodonium salts easily available for various applications in synthesis.

  • 9.
    Bielawski, Marcin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Aili, David
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Regiospecific One-Pot Synthesis of Diaryliodonium Tetrafluoroborates from Arylboronic Acids and Aryl Iodides2008In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 73, no 12, p. 4602-4607Article in journal (Refereed)
    Abstract [en]

    Diaryliodonium salts have recently received considerable attention as mild arylation reagents in organic synthesis. This paper describes a regiospecific, sequential one-pot synthesis of symmetrical and unsymmetrical diaryliodonium tetrafluoroborates, which are the most popular salts in metal-catalyzed arylations. The protocol is fast and high-yielding and has a large substrate scope. Furthermore, the corresponding diaryliodonium triflates can conveniently be obtained via an in situ anion exchange.

  • 10.
    Borén, Linnéa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantioselective Synthesis of Sec-Alcohol Derivatives and Diols via Combined Ruthenium and Enzyme Catalysis2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The first part of this thesis describes the synthesis of enantiopure secondary alcohol derivatives. These syntheses are carried out via the combination of an enzyme as a resolution catalyst and a ruthenium catalyst as a racemization catalyst, in what is called dynamic kinetic resolution (DKR). By varying the resolution catalyst enantio-complementary processes can be obtained. A lipase (PS-C II) catalyzed DKR of γ-hydroxyamides gave the corresponding (R)-acetates in high yields and with high enantioselectivity. The synthetic usefulness of these obtained (R)-acetates was demonstrated by the synthesis of (R)-5-methyltetrahydrofurane-2-one. A protease (Subtilisin Carlsberg) catalyzed DKR of various secondary alcohols gave the corresponding (S)-acetates in high yields and with high enantioselectivity. In the second part of this thesis the DKR process has been extended into a dynamic kinetic asymmetric transformation (DYKAT) of diols. Various 1,5- and 1,4-diols were transformed into enantiopure diacetates in a lipase (CALB and PS-C II) catalyzed DYKAT. The synthetic utility of the obtained enantiopure diacetates were demonstrated by the synthesis of various enantiopure disubstituted heterocycles.

  • 11.
    Ericsson, Daniel J.
    et al.
    1Department of Cell and Molecular Biology, Uppsala University, Biomedical Center.
    Kasrayan, Alex
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johansson, Patrik
    1Department of Cell and Molecular Biology, Uppsala University, Biomedical Center.
    Bergfors, Terese
    1Department of Cell and Molecular Biology, Uppsala University, Biomedical Center.
    Sandström, Anders G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mowbray, Sherry L.
    Department of Molecular Biology, Swedish University of Agricultural Sciences, Biomedical Center.
    X-Ray structure of Candida antarctica lipase A shows a novel lid structure and a likely mode of interfacial activation2008In: Journal of Molecular Biology, ISSN 0022-2836, Vol. 376, no 1, p. 109-119Article in journal (Refereed)
    Abstract [en]

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

  • 12.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramon
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vesely, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Cordova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic enantioselective 5-hydroxyisoxazolidine synthesis: An asymmetric entry to beta-amino acids2008In: Synthesis (Stuttgart), ISSN 0039-7881, E-ISSN 1437-210X, no 7, p. 1153-1157Article in journal (Refereed)
    Abstract [en]

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

  • 13.
    Kalek, Marcin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stawinski, Jacek
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-catalyzed C-P bond formation: Mechanistic studies on the ligand substitution and the reductive elimination. An intramolecular catalysis by the acetate group in PdII complexes2008In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 27, no 22, p. 5876-5888Article in journal (Refereed)
    Abstract [en]

    Ligand substitution and reductive elimination of the palladium-catalyzed C−P bond forming cross-coupling were investigated in depth. It was found that for PhPdII(PPh3)2X (X = I, Br, Cl) complexes, a step commonly referred to as ligand substitution commenced with coordination of an H-phosphonate diester, followed by its deprotonation to form an equilibrium mixture of penta- and tetracoordinate palladiumphosphonate intermediates, from which reductive elimination of the product (diethyl phenylphosphonate) occurred. For the acetate counterpart, PhPdII(PPh3)2(OAc), the incorporation of a phosphonate moiety to the complex was preceded by a rate-determining removal of the supporting phosphine ligand, facilitated by an intramolecular catalysis by the acetate group. Both the reaction steps, i.e., formation of palladiumphosphonate intermediates and reductive elimination, were significantly faster for the acetate versus halides containing PdII complexes investigated. Similar observations were found to be true also for bidentate ligand complexes [(dppp)PdII(Ph)X]; however, in this instance, a single palladiumphosphonate intermediate, (dppp)PdII(Ph)(PO(OEt)2), could be observed by 31P NMR spectroscopy. The synthetic and kinetic studies on the cross-coupling reaction of diethyl H-phosphonate with phenyl halides permitted us to elucidate a crucial catalytic role of an acetate group in PdII complexes and to propose two distinctive catalytic cycles, which complemented traditional Pd0/PdII schemes, for the palladium-mediated C−P bond formation.

  • 14.
    Kalek, Marcin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ziadi, Asraa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stawinski, Jacek
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Microwave-assisted palladium-catalyzed cross-coupling of aryl and vinyl halides with H-phosphonate diesters2008In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 10, no 20, p. 4637-4640Article in journal (Refereed)
    Abstract [en]

    A general and efficient method for the microwave-assisted formation of the C−P bond was developed. Using a prevalent palladium catalyst, Pd(PPh3)4, a quantitative cross-coupling of various H-phosphonate diesters with aryl and vinyl halides was achieved in less than 10 min. The reactions occurred with retention of configuration at the phosphorus center and in the vinyl moiety. Using this protocol, several C-phosphonates, including those bearing nucleoside and cholesteryl moieties, were prepared in high yields.

  • 15.
    Karlsson, Erik A.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mechanism of the palladium-catalyzed carbohydroxylation of allene-substituted conjugated dienes: rationalization of the recently observed nucleophilic attack by water on a (pi-allyl)palladium intermediate2008In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 14, no 30, p. 9175-9180Article in journal (Refereed)
    Abstract [en]

    The mechanism of the palladium-catalyzed oxidative carbohydroxylation of allene-substituted 1,3-cyclohexadiene was studied by DFT calculations. All intermediates and transition states of the reaction were identified and their structures were calculated. The calculations confirm the mechanism previously proposed and show that the CC bond-forming step occurs via insertion of one of the double bonds of 1,3-cyclohexadiene into a Pdvinyl bond of a vinylpalladium intermediate. This reaction leads to a (π-allyl)palladium intermediate, and coordination of benzoquinone and a double bond in the molecule to Pd creates a highly reactive cationic π-allyl complex, which is readily attacked by water according to the calculations.

  • 16. Koshino, Masanori
    et al.
    Solin, Niclas
    Tanaka, Takatsugu
    Isobe, Hiroyuki
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nakamura, Eiichi
    Imaging the passage of a single hydrocarbon chain through a nanopore2008In: Nature Nanotechnology, ISSN 1748-3387, E-ISSN 1748-3395, Vol. 3, no 10, p. 595-597Article in journal (Refereed)
    Abstract [en]

    Molecular transport through nanoscale pores in films, membranes and wall structures is of fundamental importance in a number of physical, chemical and biological processes(1-6). However, there is a lack of experimental methods that can obtain information on the structure and orientation of the molecules as they pass through the pore, and their interactions with the pore during passage. Imaging with a transmission electron microscope is a powerful method for studying structural changes in single molecules as they move(7,8) and for imaging molecules confined inside carbon nanotubes(9). Here, we report that such imaging can be used to observe the structure and orientation of a hydrocarbon chain as it passes through nanoscale defects in the walls of a single-walled carbon nanotube to the vacuum outside, and also to study the interactions between the chain and the nanopore. Based on experiments at 293 K and 4 K we conclude that the major energy source for the molecular motions observed at 4 K is the electron beam used for the imaging.

  • 17.
    Leijondahl, Karin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis and asymmetric transformations of diols by enzyme- and ruthenium catalysis2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The major part of this thesis describes the synthesis of aliphatic secondary diols and the development of lipase- and ruthenium-catalyzed asymmetric transformations of these diols.

    Several acyclic 1,4-diols and 1,5-diols were synthesized, and by combining a lipase-catalyzed asymmetric transformation with a ruthenium-catalyzed epimerization, enantiomerically- and diastereomerically enriched diacetates were obtained. The scope and limitations of the system were also investigated, and some problems were encountered with electron-deficient diols. The diacetate products were further transformed into natural product heterocycles and chiral ligands.

    A thorough study of the enzyme-catalyzed asymmetric transformation of 1,3-cyclohexanediol was also performed. It was found that there was a difference in the enzyme selectivity for the cis- and trans- diols, respectively, and while poor selectivity was observed for the trans-diol, cis-1,3-cyclohexanediol could be efficiently desymmetrized. By adding different epimerization catalysts, both cis- and trans-1,3-cyclohexanediol could be obtained in high enantio- and diastereoselectivities.

    The use of hydrogen transfer for the reduction of cyclic 1,3-diketones was also demonstrated, and the reactions could in many cases be carried out in a microwave oven.

  • 18.
    Leijondahl, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Borén, Linnéa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Braun, Roland
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantiopure 1,5-diols from dynamic kinetic asymmetric transformation: Useful synthetic intermediates for the preparation of chiral heterocycles2008Conference paper (Other academic)
  • 19.
    Leijondahl, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Borén, Linnéa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Braun, Roland
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantiopure 1,5-diols from dynamic kinetic asymmetric transformation: Useful synthetic intermediates for the preparation of heterocycles2008In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 10, no 10, p. 2027-2030Article in journal (Refereed)
    Abstract [en]

    Dynamic kinetic asymmetric transformation (DYKAT) of a series of 1,5-diols has been performed in the presence of Candida antarctica lipase B (CALB), Pseudomonas cepacia lipase H (PS-C II), and ruthenium catalyst 4. The resulting optically pure 1,5-diacetates are useful synthetic intermediates, which was demonstrated by the syntheses of both an enantiopure 2,6-disubstituted piperidine and an enantiopure 3,5-disubstituted morpholine.

  • 20.
    Nozière, Barbara
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    A Kinetic and Mechanistic Study of the Amino Acid Catalyzed Aldol Condensation of Acetaldehyde in Aqueous and Salt Solutions2008In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 112, no 13, p. 2827-2837Article in journal (Refereed)
    Abstract [en]

    The amino acid-catalyzed aldol condensation is of great interest in organic synthesis and natural environments such as atmospheric particles. But kinetic and mechanistic information on these reactions is limited. In this work, the kinetics of the aldol condensation of acetaldehyde in water and aqueous salt solutions (NaCl, CaCl2, Na2SO4, MgSO4), catalyzed by five amino acids (glycine, alanine, serine, arginine, and proline) at room temperature (295 ± 2K) has been studied. Monitoring the formation of three products, crotonaldehyde, 2,4-hexadienal, and 2,4,6-octatrienal by UV-Visible absorption over 200 – 1100 nm revealed two distinct kinetic regimes: at low amino acid concentrations (in all cases, below 0.1 M) the overall reaction was first order with respect to acetaldehyde and kinetically limited by the formation of the enamine intermediate. At larger amino acid concentrations (at least 0.3 M) the kinetics was second order and controlled by the C-C bond-forming step. The first-order rate constants increased linearly with amino acid concentration, consistent with the enamine formation. Inorganic salts further accelerated the enamine formation according to their pKb plausibly by facilitating the iminium and/or enamine formation. The rate constant of the C-C bond-forming step varied with the square of amino acid concentration, suggesting the involvement of two amino acid molecules. Thus, the reaction proceeded via a Mannich pathway. However, the contribution of an aldol pathway, first-order in amino acid, could not be excluded. Our results show that the rate constant for the self-condensation of acetaldehyde in aqueous atmospheric aerosols (up to 10 of mM of amino acids) is identical as in sulfuric acid 10 - 15 M (kI ~ 10-7 - 10-6 s-1), clearly illustrating the potential importance of amino acid catalysis in natural environments. This work also demonstrates that under usual laboratory conditions and in natural environments aldol condensation is likely to be kinetically controlled by the enamine formation. Notably, kinetic investigations of the C-C bond-forming addition step would only be possible with high concentrations of amino acids.

  • 21.
    Olsson, Ulrika
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Structural Studies of O-antigen polysaccharides, Synthesis of 13C-labelled Oligosaccharides and Conformational Analysis thereof, using NMR Spectroscopy2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In order to understand biological processes, to treat and diagnose diseases, find appropriate vaccines and to prevent the outbreak of epidemics, it is essential to obtain more knowledge about carbohydrate structures. This thesis deals with structure and conformation of carbohydrates, analysed by NMR spectroscopy and MD simulations.In the first two papers, the structures of O-antigen polysaccharides (PS) from two different E. coli bacteria were determined using NMR spectroscopy. The O-antigenic PS from E. coli O152 (paper I) consists of branched pentasaccharide repeating units, built up of three different carbohydrate residues and a phosphodiester, whilst the repeating unit of the O-antigen from E. coli O176 (paper II) is built up of a linear tetrasaccharide consisting of two different monosaccharides.

    In papers III and IV, the conformational analysis of different disaccharides is described. Conformational analysis was performed using NMR spectroscopy and MD simulations (paper IV). In paper III four different glucobiosides were studied using coupling constants and Karplus-type relationships. By use of specific 13C isotopically labelled derivatives, additional coupling constants were obtained and the number of possible torsion angles was reduced by half. In paper IV, we examine the conformations of two disaccharides that are part of an epitope of malignant cells. From NOE and T-ROE experiments, short proton-proton distances around the glycosidic linkage were estimated. Furthermore, interpretation of the extracted coupling constants using Kaplus relationships gave the values of the torsion angles. As in paper III, isotopically labelled compounds were synthesised in order to enhance the sensitivity of the analysis. Finally, MD simulations were performed and the results were compared with results from NMR data.

  • 22.
    Olsson, Ulrika
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Serianni, Anthony S.
    Stenutz, Roland
    Conformational analysis of β-linked glucobiosides based on hetero- and homonuclear couplings across the glycosidic linkage2008In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Journal of physical chemistry, ISSN 0022-3654, Vol. 112, no 14, p. 4447-4453Article in journal (Refereed)
    Abstract [en]

    Four β-linked glucobioses selectively 13C labeled at C1‘ or C2‘ have been prepared. The inter-residue coupling constants, JCH, and JCC, have been determined and related to the solution conformations of the disaccharides using Karplus-type relationships. Relying only on the experimental coupling constants, glycosidic linkage conformation in methyl α-sophoroside (methyl 2-O-β-d-glucopyranosyl-α-d-glucopyranoside), methyl α-laminarabioside (methyl 3-O-β-d-glucopyranosyl-α-d-glucopyranoside), and methyl α-cellobioside (methyl 4-O-β-d-glucopyranosyl-α-d-glucopyranoside) were found to be close to those observed in the solid state (39° < H < 41°, −24° < ψH < −36°). The laminarabioside and cellobioside were found to have conformations that accommodate an intramolecular hydrogen bond to O5‘ that is observed in the solid state. In all compounds, the exocyclic hydroxymethyl groups retain a conformation close to that observed in unsubstituted glucose (gt/gg 1:1). Methyl α-gentiobioside (methyl 6-O-β-d-glucopyranosyl-α-d-glucopyranoside) shows greater flexibility at the ψ-torsion than the other disaccharides, but the population distribution around the C5−C6 bond is essentially unaffected by substitution. None of the O2‘ hydroxyl groups of the β-d-glucopyranosyl residues in any of the disaccharides appear to be involved in inter-residue hydrogen bonding since 1JCH, 1JCC, and 2JCH values sensitive to C2‘−O2‘ rotamer distribution remain close to those observed in methyl β-d-glucopyranoside.

  • 23.
    Olsson, Ulrika
    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 determination of the O-antigenic polysaccharide from the verocytotoxin-producing Escherichia coli O1762008In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 343, no 4, p. 805-809Article in journal (Refereed)
    Abstract [en]

    The structure of the O-antigen polysaccharide (PS) from Escherichia coli O176 has been determined. Component analysis together with H-1 and C-13 NMR spectroscopy was employed to elucidate the structure. Inter-residue correlations were determined by H-1,H-1 NOESY and H-1, C-13 heteronuclear multiple-bond correlation experiments. The PS is composed of tetrasaccharide repeating units with the following structure: -> 4)-alpha-D-Manp-(1 -> 2)-alpha-D-Manp-(1 -> 2)-beta-D-Manp-(1 -> 3)-alpha-D-GalpNAc-(-> Cross-peaks of low intensity from alpha-linked mannopyranosyl residues were present in the H-1, H-1 TOCSY NMR spectra and further analysis of these showed that they originate from the terminal part of the polysaccharide. Consequently, the biological repeating unit has a 3-substituted N-acetyl-D-galactosamine residue at its reducing end. The repeating unit of the E coli O176 O-antigen is similar to those from E coli 017 and 077, thereby explaining the reported cross-reactivities between the strains, and identical to that of Salmonella cerro (O:6, 14, 18).

  • 24. Palmgren, P.
    et al.
    Yu, S.
    Hennies, F.
    Nilson, K.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Göthelid, M.
    Changing adsorption mode of FePc on TiO2(110) by surface modification with bipyridine2008In: The Journal of Chemical Physics, ISSN 0021-9606, Vol. 129, no 7, p. 074707-1Article in journal (Refereed)
  • 25. Pan, Qinhe
    et al.
    Li, Jiyang
    Christensen, Kirsten Elvira
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Bonneau, Charlotte
    Ren, Xiaoyan
    Shi, Lei
    Zou, Xiaodong
    Li, Guanghua
    Yu, Jihong
    Xu, Ruren
    A germanate built from from 68126 cavity co-templated by a (H2O)16 water cluster and 2-methylpiperazine2008In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773Article in journal (Refereed)
  • 26.
    Selander, Nicklas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Development of Multi-Component Reactions using Catalytically Generated Allyl Metal Reagents2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This licentiate thesis is based on the development of catalytic reactions for the synthesis and application of organometallic reagents. By use of palladium pincer-complex catalysts, we have developed an efficient procedure for the synthesis of allylboronates starting from allylic alcohols. These reactions were further extended by including various one-pot multi-component reactions, using the in situ generated allylboronates. Furthermore, novel unsymmetrical palladium pincer-complexes were synthesized and studied in auto-tandem catalysis.

  • 27.
    Skantz, Linnéa
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Oscarson, Stefan
    Lahmann, Martina
    Flexible glycodendrimers targeting Galectin-32008In: 24th International Carbohydrate Symposium (ICS 2008), 27th July - 1st August, 2008, Oslo, Norway, 2008Conference paper (Other academic)
  • 28.
    Tran, Lien-Hoa
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, department of Structural Chemistry.
    Sun, Licheng
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    A New Square Planar Mn(III) Complex for Catalytic Epoxidation of Stilbene2008In: Journal of Organometallic Chemistry, ISSN 0022-328X, E-ISSN 1872-8561, Vol. 693, p. 1150-1153Article in journal (Refereed)
  • 29.
    Träff, Annika
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bogár, Krisztián
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Warner, Madeleine
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Highly efficient route for enantioselctive preparation of chlorohydrins via dynamic kinetic resolution2008In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 10, no 21, p. 4807-4810Article in journal (Refereed)
    Abstract [en]

    Dynamic kinetic resolution (DKR) of various aromatic chlorohydrins with the use of Pseudomonas cepacia lipase (PS-C “Amano” II) and ruthenium catalyst 1 afforded chlorohydrin acetates in high yields and high enantiomeric excesses. These optically pure chlorohydrin acetates are useful synthetic intermediates and can be transformed to a range of important chiral compounds.

  • 30.
    Wagner, Samuel
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Klepsch, Mirjam M.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Schlegel, Susan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Appel, Ansgar
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Draheim, Roger
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Tarry, Michael
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Högbom, Martin
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    van Wijk, Klaas J.
    Slotboom, Dirk J.
    Persson, Jan O.
    Stockholm University, Faculty of Science, Department of Mathematics.
    de Gier, Jan-Willem
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Tuning Escherichia coli for membrane protein overexpression2008In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 105, no 38, p. 14371-17376Article in journal (Refereed)
    Abstract [en]

    A simple generic method for optimizing membrane protein overexpression in Escherichia coli is still lacking. We have studied the physiological response of the widely used “Walker strains” C41(DE3) and C43(DE3), which are derived from BL21(DE3), to membrane protein overexpression. For unknown reasons, overexpression of many membrane proteins in these strains is hardly toxic, often resulting in high overexpression yields. By using a combination of physiological, proteomic, and genetic techniques we have shown that mutations in the lacUV5 promoter governing expression of T7 RNA polymerase are key to the improved membrane protein overexpression characteristics of the Walker strains. Based on this observation, we have engineered a derivative strain of E. coli BL21(DE3), termed Lemo21(DE3), in which the activity of the T7 RNA polymerase can be precisely controlled by its natural inhibitor T7 lysozyme (T7Lys). Lemo21(DE3) is tunable for membrane protein overexpression and conveniently allows optimizing overexpression of any given membrane protein by using only a single strain rather than a multitude of different strains. The generality and simplicity of our approach make it ideal for high-throughput applications.

  • 31.
    Wahlström, Karolina
    et al.
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Planstedt, Ove
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Undén, Anders
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    A carbamoyl-protective group for tyrosine that facilitatespurification of hydrophobic synthetic peptides2008In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 49, no 23, p. 3779-3781Article in journal (Refereed)
  • 32. 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)
  • 33.
    Wettergren, Jenny
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Selective transfer hydrogenations: Catalyst development and mechanistic investigations2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    By generating a library of amino acid-based ligands, pseudo-dipeptides, and combining them with transition metals, we have created selective and efficient ruthenium and rhodium catalysts for the asymmetric transfer hydrogenation of ketones. The ruthenium-catalyzed reaction was studied in detail, and we found that alkali metals play a crucial role for the reactivity and selectivity of the reaction. Furthermore, we have performed kinetic studies on the catalytic system, and the experimental data does neither support the established inner-sphere nor the classical outer-sphere mechanism. Hence, a novel mechanism for the ruthenium-pseudo-dipeptide-catalyzed transfer hydrogenation is proposed. In this unprecedented outer-sphere mechanism, a hydride and an alkali metal ion are transferred from the donor to the ruthenium complex in the rate determining step.

    In addition, the pseudo-dipeptide ligands were employed in the rhodium-catalyzed transfer hydrogenation of aryl alkyl ketones to yield the corresponding alcohols in high yields and excellent enantioselectivities (up to 98% ee). The study revealed that the alkali metals, so important in the ruthenium analogue of the reaction, do not improve the enantioselectivity of the reaction. Deuterium labeling experiments showed that the reaction follows the mono hydridic route.

    Furthermore, a novel method for efficient catalyst screening has been developed. We have demonstrated that ligand synthesis, catalyst formation, and enantioselective catalysis can be performed using an in situ one-pot procedure. The efficacy of the concept was demonstrated in the enantioselective reduction of ketones. In addition to the simplification of the catalyst formation, this approach resulted in improvement of the product ee.

    Finally, the development of a reduction protocol for the transfer hydrogenation of ketones to alcohols without the involvement of transition metal catalysts is described. Using microwave irradiation, a range of ketones was efficiently reduced in high yields using catalytic amounts of lithium 2-propoxide in 2-propanol.

  • 34.
    Zhu, Mingzhao
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Jalalian, Nazli
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    One-pot synthesis of diaryliodonium salts using toluenesulfonic acid - a fast entry to electron-rich diaryliodonium tosylates and triflates2008In: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry, ISSN 0936-5214, E-ISSN 1437-2096, no 4, p. 592-596Article in journal (Refereed)
    Abstract [en]

    A direct synthesis of symmetric and unsymmetric electron-rich diaryliodonium salts is described. The use of MCPBA and toluenesulfonic acid delivers diaryliodonium tosylates in high yields. An in situ anion exchange has also been developed, giving access to the corresponding triflate salts.

1 - 34 of 34
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