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  • 101.
    Bielawski, Marcin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Zhu, Mingzhao
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Olofsson, Berit
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Efficient and General One-Pot Synthesis of Diaryliodonium Triflates: Optimization, Scope and Limitations2007Inngår i: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 349, nr 17-18, s. 2610-2618Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Symmetrical and unsymmetrical diaryliodonium triflates have been synthesized from both electron-deficient and electron-rich arenes and aryl iodides with mCPBA and triflic acid. A thorough investigation of the optimization, scope and limitations has resulted in an improved one-pot protocol that is fast, high-yielding, and operationally simple. The reaction has been extended to the direct synthesis of symmetrical iodonium salts from iodine and arenes, conveniently circumventing the need for aryl iodides.

  • 102.
    Bielawski, Marcin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Zhu, Mingzhao
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Olofsson, Berit
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Efficient and general one-pot synthesis of diaryliodonium triflates: scope and limitations2007Inngår i: SIS Report: The 10th Symposium on Iodine Science, Chiba University, Japan 2007, 2007, s. 19-22Konferansepaper (Annet vitenskapelig)
  • 103. Biosca, Maria
    et al.
    Paptchikhine, Alexander
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Pàmies, Oscar
    Andersson, Pher G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Diéguez, Montserrat
    Extending the Substrate Scope of Bicyclic P-Oxazoline/Thiazole Ligands for Ir-Catalyzed Hydrogenation of Unfunctionalized Olefins by Introducing a Biaryl Phosphoroamidite Group2015Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, nr 8, s. 3455-3464Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study identifies a series of Ir-bicyclic phosphoroamidite-oxazoline/thiazole catalytic systems that can hydrogenate a wide range of minimally functionalized olefins (including E-and Z-tri- and disubstituted substrates, vinylsilanes, enol phosphinates, tri- and disubstituted alkenylboronic esters, and alpha,beta-unsaturated enones) in high enantioselectivities (ee values up to 99%) and conversions. The design of the new phosphoroamidite-oxazoline/thiazole ligands derives from a previous successful generation of bicyclic N-phosphane-oxazoline/thiazole ligands, by replacing the N-phosphane group with a pi-acceptor biaryl phosphoroamidite moiety. A small but structurally important family of Ir-phosphoroamidite-oxazoline/thiazole precatalysts has thus been synthesized by changing the nature of the N-donor group (either oxazoline or thiazole) and the configuration at the biaryl phosphoroamidite moiety. The substitution of the N-phosphane by a phosphoroamidite group in the bicyclic N-phosphane-oxazoline/thiazole ligands extended the range of olefins that can be successfully hydrogenated.

  • 104.
    Björklund, Catarina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Design and Synthesis of BACE-1 Inhibitors: Novel Compounds Targeting an Aspartic Protease Important in the Pathogenesis of Alzheimer’s Disease2009Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis deals with the design and synthesis of protease inhibitors targeting the aspartic protease BACE-1 (β-site APP cleaving enzyme-1), an enzyme important in the pathogenesis of Alzheimer’s disease. The inhibitors are evaluated with respect to inhibition data, in a structure-activity relationship part.

    Alzheimer’s disease is a disabling, progressive and ultimately fatal form of dementia afflicting approximately 40 percent of the population over 80 years, with over 30 million people suffering from Alzheimer’s disease worldwide. This makes Alzheimer’s disease the most common form of dementia. The identification of the amyloid-β peptide (Aβ) as the main constituent of extracellular plaques, which characterize Alzheimer’s disease, suggests that Aβ plays a vital role in the pathology of Alzheimer’s disease. The formation of Aβ occurs when amyloid-β precursor protein (APP) is cleaved by β-secretase (BACE-1) and γ-secretase, which differ in length by 39-42 amino acids. This suggests that β-secretase is a suitable target for the development of therapeutics against Alzheimer’s disease.

    The synthetic work of this thesis comprises development of BACE-1 inhibitors containing a hydroxyethylene (HE) central core transition state isostere. The target molecules were readily synthesized from chiral carbohydrate starting materials. Highly potent inhibitors were produced by varying the substituents coupled to the HE central core. Selecting an aryloxymethyl P1 side-chain and a methoxy P1’ side-chain resulted in exceptionally potent BACE-1 inhibitors that also exhibit high selectivity over cathepsin D. In a further development, the ether oxygen linkage in the P1 side-chain was removed, resulting in a carba analogue, providing improved potency in a cell-based assay.

  • 105.
    Björndal, Håkan
    Stockholms universitet.
    Studies on some polysaccarides from wood-destroying fungi1970Doktoravhandling, med artikler (Annet vitenskapelig)
  • 106.
    Björsne, Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Synthesis of potential candidates for therapeutic intervention against the human immunodeficiency virus1995Doktoravhandling, med artikler (Annet vitenskapelig)
  • 107.
    Blomberg, Margareta R. A.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Active Site Midpoint Potentials in Different Cytochrome c Oxidase Families: A Computational Comparison2019Inngår i: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 58, nr 15, s. 2028-2038Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cytochrome c oxidase (CcO) is the terminal enzyme in the respiratory electron transport chain, reducing molecular oxygen to water. The binuclear active site in CcO comprises a high-spin heme associated with a Cu-B complex and a redox active tyrosine. The electron transport in the respiratory chain is driven by increasing midpoint potentials of the involved cofactors, resulting in a release of free energy, which is stored by coupling the electron transfer to proton translocation across a membrane, building up an electrochemical gradient. In this context, the midpoint potentials of the active site cofactors in the CcOs are of special interest, since they determine the driving forces for the individual oxygen reduction steps and thereby affect the efficiency of the proton pumping. It has been difficult to obtain useful information on some of these midpoint potentials from experiments. However, since each of the reduction steps in the catalytic cycle of oxygen reduction to water corresponds to the formation of an O-H bond, they can be calculated with a reasonably high accuracy using quantum chemical methods. From the calculated O-H bond strengths, the proton-coupled midpoint potentials of the active site cofactors can be estimated. Using models representing the different families of CcO's (A, B, and C), the calculations give midpoint potentials that should be relevant during catalytic turnover. The calculations also suggest possible explanations for why some experimentally measured potentials deviate significantly from the calculated ones, i.e., for Cu-B in all oxidase families, and for heme b(3) in the C family.

  • 108.
    Blomberg, Margareta R. A.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Mechanism of Oxygen Reduction in Cytochrome c Oxidase and the Role of the Active Site Tyrosine2016Inngår i: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 55, nr 3, s. 489-500Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cytochrome c oxidase, the terminal enzyme in the respiratory chain, reduces molecular oxygen to water and stores the released energy through electrogenic chemistry and proton pumping across the membrane. Apart from the heme-copper binuclear center, there is a conserved tyrosine residue in the active site (BNC). The tyrosine delivers both an electron and a proton during the O-O bond cleavage step, forming a tyrosyl radical. The catalytic cycle then occurs in four reduction steps, each taking up one proton for the chemistry (water formation) and one proton to be pumped. It is here suggested that in three of the reduction steps the chemical proton enters the center of the BNC, leaving the tyrosine unprotonated with radical character. The reproprotonation of the tyrosine occurs first in the final reduction step before binding the next oxygen molecule. It is also suggested that this reduction mechanism and the presence of the tyrosine are essential for the proton pumping. Density functional theory calculations on large cluster models of the active site show that only the intermediates with the proton in the center of the BNC and with an unprotonated tyrosyl radical have a high electron affinity of similar size as the electron donor, which is essential for the ability to take up two protons per electron and thus for the proton pumping. This type of reduction mechanism is also the only one that gives a free energy profile in accordance with experimental observations for the amount of proton pumping in the working enzyme.

  • 109.
    Blomberg, Margareta R. A.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Borowski, Tomasz
    Himo, Fahmi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Liao, Rong-Zhen
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Siegbahn, Per E. M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Quantum Chemical Studies of Mechanisms for Metalloenzymes2014Inngår i: Chemical Reviews, ISSN 0009-2665, E-ISSN 1520-6890, Vol. 114, nr 7, s. 3601-3658Artikkel, forskningsoversikt (Fagfellevurdert)
  • 110.
    Blomberg, Margareta R. A.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Siegbahn, Per E. M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    How cytochrome c oxidase can pump four protons per oxygen molecule at high electrochemical gradient2015Inngår i: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1847, nr 3, s. 364-376Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Experiments have shown that the A-family cytochrome c oxidases pump four protons per oxygen molecule, also at a high electrochemical gradient. This has been considered a puzzle, since two of the reduction potentials involved, Cu(II) and Fe(III), were estimated from experiments to be too low to afford proton pumping at a high gradient The present quantum mechanical study (using hybrid density functional theory) suggests a solution to this puzzle. First, the calculations show that the charge compensated Cu(II) potential for Cu-B is actually much higher than estimated from experiment, of the same order as the reduction potentials for the tyrosyl radical and the ferryl group, which are also involved in the catalytic cycle. The reason for the discrepancy between theory and experiment is the very large uncertainty in the experimental observations used to estimate the equilibrium potentials, mainly caused by the lack of methods for direct determination of reduced Cu-B. Second, the calculations show that a high energy metastable state, labeled E-H, is involved during catalytic turnover. The E-H state mixes the low reduction potential of Fe(III) in heme a(3) with another, higher potential, here suggested to be that of the tyrosyl radical, resulting in enough exergonicity to allow proton pumping at a high gradient In contrast, the corresponding metastable oxidized state, O-H, is not significantly higher in energy than the resting state, O. Finally, to secure the involvement of the high energy E-H state it is suggested that only one proton is taken up via the K-channel during catalytic turnover.

  • 111.
    Blomberg, Margareta R. A.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Siegbahn, Per E. M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Improved free energy profile for reduction of NO in cytochrome c dependent nitric oxide reductase (cNOR)2016Inngår i: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987X, Vol. 37, nr 19, s. 1810-1818Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Quantum chemical calculations play an essential role in the elucidation of reaction mechanisms for redox-active metalloenzymes. For example, the cleavage and the formation of covalent bonds can usually not be described only on the basis of experimental information, but can be followed by the calculations. Conversely, there are properties, like reduction potentials, which cannot be accurately calculated. Therefore, computational and experimental data has to be carefully combined to obtain reliable descriptions of entire catalytic cycles involving electron and proton uptake from donors outside the enzyme. Such a procedure is illustrated here, for the reduction of nitric oxide (NO) to nitrous oxide and water in the membrane enzyme, cytochrome c dependent nitric oxide reductase (cNOR). A surprising experimental observation is that this reaction is nonelectrogenic, which means that no energy is conserved. On the basis of hybrid density functional calculations a free energy profile for the entire catalytic cycle is obtained, which agrees much better with experimental information on the active site reduction potentials than previous ones. Most importantly the energy profile shows that the reduction steps are endergonic and that the entire process is rate-limited by high proton uptake barriers during the reduction steps. This result implies that, if the reaction were electrogenic, it would become too slow when the gradient is present across the membrane. This explains why this enzyme does not conserve any of the free energy released.

  • 112.
    Blomberg, Margareta R. A.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Siegbahn, Per E. M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Proton pumping in cytochrome c oxidase: Energetic requirements and the role of two proton channels2014Inngår i: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1837, nr 7, s. 1165-1177Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cytochrome c oxidase is a superfamily of membrane bound enzymes catalyzing the exergonic reduction of molecular oxygen to water, producing an electrochemical gradient across the membrane. The gradient is formed both by the electrogenic chemistry, taking electrons and protons from opposite sides of the membrane, and by proton pumping across the entire membrane. In the most efficient subfamily, the A-family of oxidases, one proton is pumped in each reduction step, which is surprising considering the fact that two of the reduction steps most likely are only weakly exergonic. Based on a combination of quantum chemical calculations and experimental information, it is here shown that from both a thermodynamic and a kinetic point of view, it should be possible to pump one proton per electron also with such an uneven distribution of the free energy release over the reduction steps, at least up to half the maximum gradient. A previously suggested pumping mechanism is developed further to suggest a reason for the use of two proton transfer channels in the A-family. Since the rate of proton transfer to the binuclear center through the D-channel is redox dependent, it might become too slow for the steps with low exergonicity. Therefore, a second channel, the K-channel, where the rate is redox-independent is needed. A redox-dependent leakage possibility is also suggested, which might be important for efficient energy conservation at a high gradient. A mechanism for the variation in proton pumping stoichiometry over the different subfamilies of cytochrome oxidase is also suggested. This article is part of a Special Issue entitled: 18th European Bioenergetic Conference.

  • 113.
    Bogár, Krisztián
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Synthetic Transformations via Metal- and Enzyme-Catalyzed Dynamic Kinetic Resolution2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis deals with the preparation of a new half-sandwich type ruthenium(II)- catalyst for racemization of optically active secondary alcohols and the development of a highly efficient method in combination with lipases such as Candida antarctica lipase B and Pseudomonas cepacia lipase for dynamic kinetic resolution of various functionalized alcohols under mild reaction conditions.

    It was shown that the RuCl(CO)25-C5Ph5) complex can racemize optically active aliphatic and aromatic secondary alcohols at room temperature in rather short times. Different parameters, such as the nature of the catalyst, catalyst loading and solvent effect were studied. After the optimization steps, the Ru-catalyzed racemization of (S)-1-phenylethanol in the presence of Candida antarctica lipase B was also investigated. The compatibility of the metal- and enzyme-catalyzed reactions led to a highly efficient coupled catalytic system for transformation of racemic alcohols to their enantiomerically pure acetates. This protocol was applied for a wide range of secondary alcohols. It was shown that in the case of allylic alcohols the obtained enantiopure allylic acetates are useful compounds for synthesis of α-methyl carboxylic acids such as (R)-Flurbiprofen and acyloin acetates. Highly selective dynamic kinetic asymmetric transformation of 3,5-piperidine diol to deliver various 3,5-dioxygenated piperidines is also described.

  • 114.
    Bogár, Krisztián
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    High-yielding metalloenzymatic dynamic kinetic resolution of fluorinated aryl alcohols2007Inngår i: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 48, nr 31, s. 5471-5474Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dynamic kinetic resolution (DKR) of various fluorinated aryl alcohols by a combination of lipase-catalyzed enzymatic resolution with in situ ruthenium-catalyzed alcohol racemization is described. (R)-Selective Candida antarctica lipase B (CALB) was employed for transesterification of different fluoroaryl alcohols in DKR reactions delivering the corresponding acetates in high yield (97%) with excellent enantiomeric excess (98%).

  • 115.
    Bogár, Krisztián
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Hoyos Vidal, Pilar
    Alcántara León, Andrés R.
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Chemoenzymatic Dynamic Kinetic Resolution of Allylic Alcohols: A Highly Enantioselective Route to Acyloin Acetates2007Inngår i: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 9, nr 17, s. 3401-3404Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dynamic kinetic resolution (DKR) of a series of sterically hindered allylic alcohols has been conducted with Candida antarctica lipase B (CALB) and ruthenium catalyst 1. The optically pure allylic acetates obtained were subjected to oxidative cleavage to give the corresponding acylated acyloins in high yields without loss of chiral information.

  • 116.
    Bogár, Krisztián
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Krumlinde, Patrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bacsik, Zoltán
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Bäckvall, Jan E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Heterogenized Wilkinson's Catalyst for Transfer Hydrogenation of Carbonyl Compounds2011Inngår i: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, nr 23, s. 4409-4414Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wilkinson’s catalyst [RhCl(PPh3)3] was heterogenized on common silica by the use of a grafting/anchoring technique. The immobilized catalyst showed high activity and selectivity in transfer hydrogenation reactions of a range of carbonyl compounds in 2-propanol. Reactions carried out in 2-propanol at reflux afforded the corresponding alcohols in high yields in short reaction times. The heterogeneous feature ofthe catalyst allows for easy recovery and efficient reuse in the same reaction up to 5 times without any detectible loss of catalytic activity.

  • 117. Bogár, Krisztián
    et al.
    Krumlinde, Patrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Hydrogenized Wilkinson´s Catalyst for Transfer Hydrogenation of Carbonyl CompoundsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Combining the advantages of homogeneous and heterogeneous catalysis is possible by heterogenization of homogeneous transition metal complexes based on a grafting/anchoring technique. Wilkinson’s catalyst ((RhCl(PPh3)3) immobilized on common silica showed high activity and selectivity in transfer hydrogenation reactions of different carbonyl compounds in isopropanol. Reactions conducted at reflux in isopropanol afforded the corresponding carbinols in high yields in short reaction times. The heterogeneous feature of the catalyst allows easy recovery and efficient reuse in the same reaction up to 5 times without loss of catalytic activity.

  • 118. Bogár, Krisztián
    et al.
    Martín-Matute, Belén
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Large-scale ruthenium- and enzyme-catalyzed dynamic kinetic resolution of (rac)-1-phenylethanol2007Inngår i: Beilstein Journal of Organic Chemistry, ISSN 1860-5397, Vol. 3, s. artikel nr 50-Artikkel i tidsskrift (Fagfellevurdert)
  • 119.
    Bogár, Krisztián
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Olofsson, Berit
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Fransson, Ann-Britt L.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Asymmetric synthesis of 3,5-disubstituted piperidines by enzyme-metal combo catalysis2006Inngår i: Enzymatic Synthesis, Stockholm, Sweden, 2006Konferansepaper (Annet (populærvitenskap, debatt, mm))
  • 120.
    Bollmark, Martin
    Stockholms universitet.
    Studies on the synthesis of nucleotide analogues containing P-F and P-Se bonds2001Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In the present work, new synthetic approaches to the synthesis of nucleoside phosphorofluoridate and phosphorofluoridothioate diesters have been developed. These procedures involve either oxidative transformation of the corresponding H-phosphonate or H-phosphonothioate diesters in the presence of fluoride anion or iodine-promoted desulfurization of phosphorothioate or phosphorodithioate diesters in the presence of fluoride anion. Also, efficient protocols for the synthesis of nucleoside phosphorofluoridate, nucleoside phosphorofluoridothioate and nucleoside phosphorofluoridodithioate monoesters were developed.

    Furthermore, the chemistry of a new class of P(III) compounds containing selenium, i. e. H-phosphonoselenoate monoesters was developed and synthetic procedures for the conversion of these compounds into the corresponding diesters were designed. In addition, the usefulness of H-phosphonoselenoate diesters for the preparation of various selenium-containing nucleotide analogues was demonstrated.

    Finally, the possibility of employing triphenylphosphine selenide as a reagent for selenizing P(III) compounds was examined. Under mild conditions, this commercially available reagent was found to convert phosphite triesters and H-phosphonate diesters efficiently into the corresponding phosphoroselenoate derivatives.

  • 121.
    Bornschein, Christoph
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi. Universität Rostock, Germany.
    Gustafson, Karl P. J.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Verho, Oscar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Beller, Matthias
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Evaluation of Fe and Ru Pincer-Type Complexes as Catalysts for the Racemization of Secondary Benzylic Alcohols2016Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, nr 33, s. 11583-11586Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fe and Ru pincer-type catalysts are used for the racemization of benzylic alcohols. Racemization with the Fe catalyst was achieved within 30 minutes under mild reaction conditions, with a catalyst loading as low as 2 mol %. This reaction constitutes the first example of an iron-catalyzed racemization of an alcohol. The efficiency for racemization of the Fe catalyst and its Ru analogue was evaluated for a wide range of sec-benzylic alcohols. The commercially available Ru complex proved to be highly robust and even tolerated the presence of water in the reaction mixture.

  • 122.
    Borén, Linnéa
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Enantioselective Synthesis of Sec-Alcohol Derivatives and Diols via Combined Ruthenium and Enzyme Catalysis2008Doktoravhandling, med artikler (Annet vitenskapelig)
    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.

  • 123.
    Borén, Linnéa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Leijondahl, Karin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Dynamic Kinetic Asymmetric Transformation of 1,4-diols and Preparation of Trans-2,5-Disubstituted pyrrolidines2009Inngår i: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 50, nr 26, s. 3237-3240Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dynamic kinetic asymmetric transformation (DYKAT) of a series of 1,4-diols is carried out with Candida antarctica lipase B (CALB), Pseudomonas cepacia lipase II (PS-C II), and a ruthenium catalyst. A β-chloro-substituted 1,4-diol is successfully transformed into an optically pure 1,4-diacetate, which is a highly useful synthetic intermediate. The usefulness of the optically pure 1,4-diacetates is demonstrated by the synthesis of enantiopure 2,5-disubstituted pyrrolidines.

  • 124. Both, P.
    et al.
    Green, A. P.
    Gray, C. J.
    Sardzik, R.
    Voglmeir, J.
    Fontana, Carolina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Austeri, M.
    Rejzek, M.
    Richardson, D.
    Field, R. A.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Flitsch, S. L.
    Eyers, C. E.
    Discrimination of epimeric glycans and glycopeptides using IM-MS and its potential for carbohydrate sequencing2014Inngår i: Nature Chemistry, ISSN 1755-4330, E-ISSN 1755-4349, Vol. 6, nr 1, s. 65-74Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mass spectrometry is the primary analytical technique used to characterize the complex oligosaccharides that decorate cell surfaces. Monosaccharide building blocks are often simple epimers, which when combined produce diastereomeric glycoconjugates indistinguishable by mass spectrometry. Structure elucidation frequently relies on assumptions that biosynthetic pathways are highly conserved. Here, we show that biosynthetic enzymes can display unexpected promiscuity, with human glycosyltransferase pp-a-GanT2 able to utilize both uridine diphosphate N-acetylglucosamine and uridine diphosphate N-acetylgalactosamine, leading to the synthesis of epimeric glycopeptides in vitro. Ion-mobility mass spectrometry ( IM-MS) was used to separate these structures and, significantly, enabled characterization of the attached glycan based on the drift times of the monosaccharide product ions generated following collision-induced dissociation. Finally, ion-mobility mass spectrometry following fragmentation was used to determine the nature of both the reducing and non-reducing glycans of a series of epimeric disaccharides and the branched pentasaccharide Man3 glycan, demonstrating that this technique may prove useful for the sequencing of complex oligosaccharides.

  • 125.
    Bouma, M. J.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Olofsson, Berit
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    7.07 α-Oxygenation of Carbonyl Compounds2014Inngår i: Comprehensive Organic Synthesis II (Second Edition) / [ed] Paul Knochel and Gary A. Molander, Amsterdam: Oxford: Elsevier , 2014, 2nd, s. 213-241Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Abstract The chapter describes synthetically useful strategies for α-oxygenation of carbonyl compounds, with special emphasis on recent methods for catalytic and asymmetric reactions. The oxidation of enolates, enols, enol ethers, and α,β-unsaturated compounds is discussed in detail. Classical oxidation reagents like metal oxides, molecular oxygen, peroxides, and peracids are covered, with asymmetric dihydroxylation of enol ethers giving the highest enantioselectivities together with organocatalytic methods using peroxides. Oxaziridines, nitrosoarenes, and hypervalent iodine compounds are more recently developed α-oxygenation alternatives that allow metal-free oxidations under mild conditions. The combination of nitrosoarenes with organocatalysis is currently the best method for enantioselective α-oxygenations. The area of asymmetric α-oxygenations with hypervalent iodine compounds is currently under development, and high enantioselectivities have only been achieved in intramolecular reactions and epoxidations.

  • 126.
    Bouma, Marinus J.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Olofsson, Berit
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    General One-Pot Synthesis of Alkynyliodonium Salts and Alkynyl Benziodoxolones from Aryl Iodides2012Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, nr 45, s. 14242-14245Artikkel i tidsskrift (Fagfellevurdert)
  • 127.
    Bowden, Tim
    Stockholms universitet.
    Studies on glycosylation mechanisms and synthesis of structures related to inositolphosphoglycans2000Doktoravhandling, med artikler (Annet vitenskapelig)
  • 128. Bratt, Emma
    et al.
    Verho, Oscar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Johansson, Magnus J.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    A General Suzuki Cross-Coupling Reaction of Heteroaromatics Catalyzed by Nanopalladium on Amino-Functionalized Siliceous Mesocellular Foam2014Inngår i: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 79, nr 9, s. 3946-3954Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Suzuki-Miyaura cross-coupling reactions of heteroaromatics catalyzed by palladium supported in the cavities of amino-functionalized siliceous mesocellular foam are presented. The nanopalladium catalyst effectively couples not only heteroaryl halides with boronic acids but also heteroaryl halides with boronate esters, potassium trifluoroborates, MIDA boronates, and triolborates, producing a wide range of heterobiaryls in good to excellent yields. Furthermore, the heterogeneous palladium nanocatalyst can easily be removed from the reaction mixture by filtration and recycled several times with minimal loss in activity. This catalyst provides an alternative, environmentally friendly, low-leaching process for the preparation of heterobiaryls.

  • 129.
    Brea, Oriana
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Daver, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Rebek, Julius
    Himo, Fahmi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Modeling Decomposition of N-Nitrosoamides in a Self-Assembled Capsule2019Inngår i: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 84, nr 11, s. 7354-7361Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Density functional theory calculations are employed to investigate the mechanism and energies of the decomposition of N-nitrosoamides in the presence of a resorcinarene-based self-assembled nanocapsule. From experiments, it is known that confinement in the capsule inhibits the thermal decomposition of these compounds. N-Nitrosoamides with both aromatic and aliphatic substituents are considered here and the calculations show that, for both kinds, binding to the capsule leads to a significant increase in the energy barrier of the rate-determining step, the 1,3 N -> O acyl transfer reaction. A distortion-interaction analysis is conducted to probe the reasons behind the inhibition of the reaction. In addition, we characterized hypothetical intermediates that might be involved in the formation of the decomposition products inside the capsule. Interestingly, it is found that the capsule stabilizes ion-pair species that are unstable in mesitylene solution. Finally, a possible explanation is proposed for the observed encapsulation of the decomposition product of only one of the substrates.

  • 130. Brown, Michael
    et al.
    Delorme, Marion
    Malmedy, Florence
    Malmgren, Joel
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Olofsson, Berit
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Wirth, Thomas
    Synthesis of New Chiral Diaryliodonium Salts2015Inngår i: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry, ISSN 0936-5214, E-ISSN 1437-2096, Vol. 26, nr 11, s. 1573-1577Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A structurally diverse range of chiral diaryliodonium salts have been synthesised which have potential application in metal-free stereoselective arylation reactions.

  • 131.
    Buitrago, Elina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Transition metal catalyzed reduction of ketones2010Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 132.
    Buitrago, Elina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Transition metal-catalyzed reduction of carbonyl compounds: Fe, Ru and Rh complexes as powerful hydride mediators2012Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    A detailed mechanistic investigation of the previously reported ruthenium pseudo-dipeptide-catalyzed asymmetric transfer hydrogenation (ATH) of aromatic ketones was performed. It was found that the addition of alkali metals has a large influence on both the reaction rate and the selectivity, and that the rate of the reaction was substantially increased when THF was used as a co-solvent. A novel bimetallic mechanism for the ruthenium pseudo-dipeptide-catalyzed asymmetric reduction of prochiral ketones was proposed.

    There is a demand for a larger substrate scope in the ATH reaction, and heteroaromatic ketones are traditionally more challenging substrates. Normally a catalyst is developed for one benchmark substrate, and a substrate screen is carried out with the best performing catalyst. There is a high probability that for different substrates, another catalyst could outperform the one used. To circumvent this issue, a multiple screen was executed, employing a variety of ligands from different families within our group’s ligand library, and different heteroaromatic ketones to fine-tune and to find the optimum catalyst depending on the substrate. The acquired information was used in the formal total syntheses of (R)-fluoxetine and (S)-duloxetine, where the key reduction step was performed with high enantioselectivities and high yield, in each case.

    Furthermore, a new iron-N-heterocyclic carbene (NHC)-catalyzed hydrosilylation (HS) protocol was developed. An active catalyst was formed in situ from readily available imidazolium salts together with an iron source, and the inexpensive and benign polymethylhydrosiloxane (PMHS) was used as hydride donor. A set of sterically less demanding, potentially bidentate NHC precursors was prepared. The effect proved to be remarkable, and an unprecedented activity was observed when combining them with iron. The same system was also explored in the reduction of amides to amines with satisfactory results.

  • 133.
    Buitrago, Elina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Lundberg, Helena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Andersson, Hans
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Ryberg, Per
    Adolfsson, Hans
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    High Throughput Screening of a Catalyst Library for the Asymmetric Transfer Hydrogenation of Heteroaromatic Ketones: Formal Syntheses of (R)-Fluoxetine and (S)-Duloxetine2012Inngår i: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 4, nr 12, s. 2082-2089Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A total of 21 amino acid based ligands including hydroxy amide, thioamide, and hydroxamic acid functionalities, respectively, were combined with [Ru(p-cymene)Cl2]2 and [RhCp*Cl2]2, and used as catalysts for the asymmetric transfer hydrogenation of four different heteroaromatic ketones in 2-propanol. The reactions were performed on a Chemspeed automated high-throughput screening robotic platform. Optimal catalysts were identified for the individual heterocyclic substrate classes. Based on these results, the formal syntheses of the antidepressant drugs (R)-fluoxetine and (S)-duloxetine were conducted by using the found catalysts in the key reaction step, which results in high isolated yields (94?%) and excellent product enantioselectivities (>99?% ee) of the formed 1,3-amino alcohols.

  • 134.
    Buitrago, Elina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Lundberg, Helena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Andersson, Hans
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Ryberg, Per
    Aztra Zeneca, Global Process R&D, Södertälje, Sweden.
    Adolfsson, Hans
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Selective reduction of heteroaromatic ketones: A combinatorial approach2011Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The enantioselective reduction of prochiral ketones is a most productiveway towards enantio enriched secondary alcohols used in the preparation of biologically active compounds. There are numerous transition metal catalyzed methods for this transformation, particularly based on Ru(II)-and Rh(I)-complexes, but there is a demand for a larger substrate scope. Heteroaromatic ketones are traditionally more challenging substrates. Normally a catalyst is developed for one benchmark substrate, and asubstrate screen is made with the best performing catalyst. Using this methodology, there is a high probability that for different substrates, another catalyst could outperform the one used. We have executed a multiple screen, containing a variety of different ligands together with both Ru and Rh, and heteroaromatic ketones to fine-tune, and find the optimum catalyst depending on the substrate. The acquired information was used to synthesize known, biologically active compounds, where the key reduction steps were performed with high enantioselectivities and yields.

  • 135.
    Buitrago, Elina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Tinnis, Fredrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Adolfsson, Hans
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Efficient and Selective Hydrosilylation of Carbonyls Catalyzed by Iron Acetate and N-Hydroxyethylimidazolium Salts2012Inngår i: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 354, nr 1, s. 217-222Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aromatic aldehydes, along with aryl alkyl, heteroaryl alkyl, and dialkyl ketones were efficiently reduced to their corresponding primary and secondary alcohols, respectively, in high yields, using the commercially available and inexpensive polymeric silane, polymethylhydrosiloxane (PMHS), as reducing agent. The reaction is catalyzed by in situ generated iron complexes containing hydroxyethyl-functionalized NHC ligands. Turnover frequencies up to 600 h−1 were obtained

  • 136.
    Buitrago, Elina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Zani, Lorenzo
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Adolfsson, Hans
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Fe/NHC-catalyzed hydrosilylation of aromatic ketones2009Inngår i: Abstracts of Papers, 238th ACS National Meeting, Washington, DC, United States, August 16-20, 2009, Washington, DC: American Chemical Society , 2009Konferansepaper (Annet vitenskapelig)
  • 137.
    Buitrago, Elina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Zani, Lorenzo
    Adolfsson, Hans
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Selective hydrosilylation of ketones catalyzed by in situ-generated iron NHC complexes2011Inngår i: Applied organometallic chemistry, ISSN 0268-2605, E-ISSN 1099-0739, Vol. 25, nr 10, s. 748-752Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aryl alkyl-, heteroaryl alkyl- and dialkyl ketones were readily reduced to their corresponding secondary alcohols in high yields, using the commercially available and inexpensive polymeric silane polymethylhydrosiloxane (PMHS), as reducing agent. The reaction is catalyzed by an in situ-generated iron complex, conveniently generated from iron(II) acetate and the commercially available N-heterocyclic carbene (NHC) precursor IPr·HCl.

  • 138.
    Bunrit, Anon
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi. Stockholm University.
    Direct Catalytic Nucleophilic Substitution of Non-Derivatized Alcohols2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis focuses on the development of methods for the activation of the hydroxyl group in non-derivatized alcohols in substitution reactions. The thesis is divided into two parts, describing three different catalytic systems.

    The first part of the thesis (Chapter 2) describes nucleophilic allylation of amines with allylic alcohols, using a palladium catalyst to generate unsymmetrical diallylated amines. The corresponding amines were further transformed by a one-pot ring-closing metathesis and aromatization reaction to afford β-substituted pyrroles with linear and branched alkyl, benzyl, and aryl groups in overall moderate to good yields.

    The second part (Chapters 3 and 4) describes the direct intramolecular stereospecific nucleophilic substitution of the hydroxyl group in enantioenriched alcohols by Lewis acid and Brønsted acid/base catalysis.

    In Chapter 3, the direct intramolecular substitution of non-derivatized alcohols has been developed using Fe(OTf)3 as catalyst. The hydroxyl groups of aryl, allyl, and alkyl alcohols were substituted by the attack of O- and N-centered nucleophiles, to provide five- and six-membered heterocycles in up to excellent yields with high enantiospecificities. Experimental studies showed that the reaction follows first-order dependence with respect to the catalyst, the internal nucleophile, and the internal electrophile of the substrate. Competition and catalyst-substrate interaction experiments demonstrated that this transformation proceeds via an SN2-type reaction pathway.

    In Chapter 4, a Brønsted acid/base catalyzed intramolecular substitution of non-derivatized alcohols was developed. The direct intramolecular and stereospecific substitution of different alcohols was successfully catalyzed by phosphinic acid (H3PO2). The hydroxyl groups of aryl, allyl, propargyl, and alkyl alcohols were substituted by O-, N-, and S-centered nucleophiles to generate five- and six-membered heterocycles in good to excellent yields with high enantiospecificities. Mechanistic studies (both experiments and density functional theory calculations) have been performed on the reaction forming five-membered heterocyclic compounds. Experimental studies showed that phosphinic acid does not promote SN1 reactivity. Rate-order determination indicated that the reaction follows first-order dependence with respect to the catalyst, the internal nucleophile, and the internal electrophile. DFT calculations corroborated with a reaction pathway in which the phosphinic acid has a dual activation mode and operates as a bifunctional Brønsted acid/Brønsted base to simultaneously activate both the nucleophile and nucleofuge, resulting in a unique bridging transition state in an SN2-type reaction mechanism.

  • 139. Bunrit, Anon
    et al.
    Dahlstrand, Christian
    Olsson, Sandra K.
    Srifa, Pemikar
    Huang, Genping
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Orthaber, Andreas
    Sjöberg, Per J. R.
    Biswas, Srijit
    Himo, Fahmi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Samec, Joseph S. M.
    Brønsted Acid-Catalyzed Intramolecular Nucleophilic Substitution of the Hydroxyl Group in Stereogenic Alcohols with Chirality Transfer2015Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 137, nr 14, s. 4646-4649Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The hydroxyl group of enantioenriched benzyl, propargyl, allyl, and alkyl alcohols has been intramolecularly displaced by uncharged O-, N-, and S-centered nucleophiles to yield enantioenriched tetrahydrofuran, pyrrolidine, and tetrahydrothiophene derivatives with phosphinic acid catalysis. The five-membered heterocyclic products are generated in good to excellent yields, with high degree of chirality transfer, and water as the only side-product. Racemization experiments show that phosphinic acid does not promote S(N)1 reactivity. Density functional theory calculations corroborate a reaction pathway where the phosphinic acid operates as a bifunctional catalyst in the intramolecular substitution reaction. In this mechanism, the acidic proton of the phosphinic acid protonates the hydroxyl group, enhancing the leaving group ability. Simultaneously, the oxo group of phosphinic acid operates as a base abstracting the nucleophilic proton and thus enhancing the nucleophilicity. This reaction will open up new atom efficient techniques that enable alcohols to be used as nucleofuges in substitution reactions in the future.

  • 140.
    Bunrit, Anon
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Srifa, Pemikar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Dahlstrand, Christian
    Huang, Genping
    Biswas, Srijit
    Himo, Fahmi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Watile, Rahul
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Samec, Joseph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    H3PO2-Catalyzed Intramolecular Stereospecific Substitution of the Hydroxyl Group in Stereogenic Secondary Alcohols by N-, O-, and S-centered Nucleophiles to Generate HeterocyclesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The direct intramolecular stereospecific substitution of the hydroxyl group in stereogenic secondary alcohols was successfully accomplished by phosphinic acid catalysis. The hydroxyl group was displaced by O-, S-, and N-centered nucleophiles to provide enantioenriched five- and six-membered heterocycles in good to excellent yields and high enantiospecificity with water as the only by product. Mechanistic studies using both experiments and calculations have been performed. Rate order determination shows first-order dependences in catalyst, internal nucleophile, and electrophile concentrations, however, independence on external nucleophile and electrophile. Furthermore, phosphinic acid does not promote SN1 reactivity. Computational studies support a bifunctional role of the phosphinic acid in which activations of both nucleofuge and nucleophile occur in a bridging SN2-type transition state. 

  • 141.
    Bunrit, Anon
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Watile, Rahul
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Lagerspets, Emi
    Lanekoff, Ingela
    Biswas, Srijit
    Repo, Timo
    Samec, Joseph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Iron (III)-Catalyzed Intramolecular Stereospecific Substitution of the OH Group in Stereogenic Secondary and Tertiary AlcoholsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    We herein report a Fe(OTf)3-catalyzed stereospecific substitution of the hydroxyl (OH) group in secondary and tertiary alcohols by N-, and O-centered nucleophiles to generate synthetically precious enantioenriched pyrrolidines, tetrahydrofuran, 1,2,3,4-tetra-hydroquinolines, and chromanes. The substitution of the OH group in benzylic, allylic, and aliphatic alcohols proceed with high yields and high degree of enantiospecificity to give saturated five- and six-membered heterocyclic products and water as the only by-product. Mechanistic studies revealed that the intramolecular substitution reaction proceeds through an SN2 reaction with secondary alcohols and an SN1 reaction, comprising a tight ion pair, with tertiary alcohols giving products with inversion of configuration at the stereogenic carbon in both cases. The iron interacts with both nucleofile and nucloefuge, where the latter leads to a controlled carbon−oxygen (C–O) bond cleavage. The procedure opens up new atom efficient technique for catalytic stereospecific reactions that allow easily accessible stereogenic secondary and tertiary alcohols to be considered as substrates in substitution reactions. 

  • 142.
    Burkhardt, Anja
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Eriksson, Lars
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, Avdelningen för strukturkemi.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Cumpstey, Ian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    (Z)-1,2:5,6-di-O-isopropylidene-α-D-ribo-hexofuranos-3-ulose O-benzyloxime2009Inngår i: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. E65, nr Part 3, s. o633-o633Artikkel i tidsskrift (Fagfellevurdert)
  • 143.
    Buskas, Therese
    Stockholms universitet.
    Synthesis of lactosamine-containing carbohydrate structures and development for their easy assembly and conjugation1999Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis is based on four publications. The first chapter describes preparation of anomerically pure thioethyl-, thiophenyl-, and n-pentenyl 2-azido-2-deoxy glycosyl building blocks from easily accessible per-acetylated glycosamines.

    In the second part, acetylated, benzylated and non-protected n-pentenyl glycosides are used as substrates for preparing various spacer functionalities, which are obtained by means of radical elongations, oxidations and reductions.

    The syntheses of a trisaccharide,a-D-GlcpNAc-(1-->4)-b-D-Galp-(1-->4)-b-D-GlcpNAc, and fragments thereof, linked to a long lipophilic aglycon, are described in the third part. For the formation of theb-D-Galp-(1-->4)-D-GlcpNAc bond, several differently protected glucosamine acceptors were prepared and their reactivity towards a disaccharide donor evaluated.

    Finally, lactosamine derivatives were prepared by regioselective galactosylation and used as building blocks in the chemical synthesis of various oligosaccharides. The syntheses of polylactosamine di-, tri- and tetramers were achieved by regioselective glycosylation. Also spacer containing sulfated N-acetyllactosamine and Lewis x structures were synthesised.

  • 144.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Catalytic asymmetric synthesis via combined metal and enzyme catalysis2009Inngår i: 3rd Hellenic Symposium on Organic Synthesis, October 15-17, 2009, Athens, Greece: Abstracts of papers, Athens, 2009Konferansepaper (Annet vitenskapelig)
  • 145.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Modern Oxidation Methods2010Collection/Antologi (Annet vitenskapelig)
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    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Palladium- and ruthenium-catalyzed redox reactions in selective organic synthesis2009Inngår i: Abstract of LOST II Symposium in honour of Prof. Alain Krief, March 18-20, 2009, Namur, Belgium, 2009Konferansepaper (Annet vitenskapelig)
  • 147.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Pd- and Ru-catalyzed redox reactions in catalysis. Application to the combination with enzyme catalysis2009Inngår i: Abstract of 42nd Jahrestreffen Deutscher Katalytiker, March 11-13, 2009, Weimar, Germany, 2009Konferansepaper (Annet vitenskapelig)
  • 148.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Preface2010Inngår i: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 53, nr 13-14, s. 831-831Artikkel i tidsskrift (Fagfellevurdert)
  • 149.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Recent advances in the combination of metal and enzyme catalysis2009Inngår i: Abstract of the 10th Netherlands Catalysis and Chemistry Conference (NCCC-X), March 2-4, 2009, Noordwijkerhout, the Netherlands, 2009Konferansepaper (Annet vitenskapelig)
  • 150.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Selective oxidation of amines and sulfides2010Inngår i: Modern Oxidation Methods / [ed] Jan-Erling Bäckvall, Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA , 2010, 2, s. 277-313Kapittel i bok, del av antologi (Annet vitenskapelig)
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