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  • 201.
    Cumpstey, Ian
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Short synthesis of a benzyl ether protected building block for the synthesis of carbocyclic galactopyranose mimics2010In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 345, no 8, p. 1056-1060Article in journal (Refereed)
  • 202.
    Cumpstey, Ian
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of carbasugar-containing non-glycosidically linked pseudodisaccharides and higher pseudooligosaccharides2009In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 344, no 17, p. 2285-2310Article, review/survey (Refereed)
  • 203.
    Cumpstey, Ian
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Agrawal, Santosh
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Borbas, K. Eszter
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Iridium-catalysed condensation of alcohols and amines as a method for aminosugar synthesis2011In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 47, no 27, p. 7827-7829Article in journal (Refereed)
    Abstract [en]

    Primary carbohydrate amines at primary and secondary carbons are alkylated by alcohols in the presence of [Cp*IrCl2]2. When primary carbohydrate alcohols are used as the coupling partners and in the presence of Cs2CO3, amine-linked pseudodisaccharides are obtained. Secondary carbohydrate alcohols are unaffected under these conditions, which allows regioselective reactions.

  • 204.
    Cumpstey, Ian
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Alonzi, Dominic S.
    Butters, Terry D.
    Carbasugar-thioether pseudodisaccharides related to N-glycan biosynthesis2009In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 344, no 4, p. 454-459Article in journal (Refereed)
  • 205. Cumpstey, Ian
    et al.
    Frigell, jens
    Pershagen, Elias
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Alonzi, D.S.
    Butters, T.D.
    N-linked neodisaccharides: Synthesis facilitated by the enhanced reactivity of allylic electrophiles, and glycosidase inhibitory activityManuscript (preprint) (Other academic)
    Abstract [en]

    Neodisaccharides consisting of two monosaccharides linked by a bridging nitrogen atom have been synthesised. Converting one of the monosaccharide coupling components into an unsaturated derivative enhances its electrophilicity at the allylic position, facilitating coupling reactions. Mitsunobu coupling between nosylamides and 2,3-unsaturated 4-alcohols gave the 4-amino pseudodisaccharides with inversion of configuration as single regio- and diastereoisomers. A palladium catalysed coupling between an amine and a 2,3-unsaturated 4-trichloroacetimidate gave a 2-amino pseudodisaccharide as the major product along with other minor products. Derivatisation of the C=C double bond in pseudodisaccharides allowed the formation of Man(N4–6)Glc and Man(N4–6)Man neodisaccharides. The inhibitory activity of some N-linked neodisaccharides against the enzyme α-Glucosidase II is reported.

  • 206.
    Cumpstey, Ian
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ramstadius, Clinton
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Akhtar, Tashfeen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Goldstein, Irwin J.
    Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI .
    Winter, Harry C.
    Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI .
    Non-glycosidically linked pseudodisaccharides: thioethers, sulfoxides, sulfones, ethers, selenoethers, and their binding to lectins2010In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, no 10, p. 1951-1970Article in journal (Refereed)
    Abstract [en]

    Hydrolytically stable non-glycosidically linked tail-to-tail pseudodisaccharides are linked by a single bridging atom remote from the anomeric centre of the constituent monosaccharides. Some such pseudodisaccharides with sulfur or oxygen bridges were found to act as disaccharide mimetics in their binding to the Banana Lectin and to Concanavalin A. A versatile synthetic route to a small library of such compounds is described

  • 207.
    Cumpstey, Ian
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ramstadius, Clinton
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Borbas, K. Eszter
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Investigation of Coupling Reactions for the Synthesis of Valienamine Pseudodisaccharides2011In: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry, ISSN 0936-5214, E-ISSN 1437-2096, no 12, p. 1701-1704Article in journal (Refereed)
    Abstract [en]

    Amine-linked pseudodisaccharides based on valienamine were synthesised by C-N bond-forming reactions between valienol-derived C-1 electrophiles and carbohydrate nitrogen nucleophiles. Palladium-catalysed coupling with trichloroacetimidate leaving groups, Mitsunobu reactions with a nosylamide nucleophile, and alkylation of amines by C-1 bromides were investigated.

  • 208.
    Cumpstey, Ian
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ramstadius, Clinton
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Borbas, Katalin Eszter
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Alonzi, Dominic
    Oxford University.
    Butters, Terry
    Oxford University.
    Coupling reactions of valienol C-1 electrophiles for valienamine pseudodisaccharide synthesis: synthesis and α-Glucosidase II inhibitory activity of pseudodisaccharides relevant to N-glycan biosynthesisManuscript (preprint) (Other academic)
  • 209.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Asymmetric bifunctional catalysis using heterobimetallic and multimetallic systems in enantioselective conjugate additions2010In: Catalytic Asymmetric Conjugate Reactions / [ed] Armando Córdova, Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA , 2010, 1, p. 169-190Chapter in book (Other academic)
  • 210.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic Asymmetric Conjugate Reactions2010Collection (editor) (Other academic)
  • 211.
    Córdova, Armando
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Engqvist, Magnus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ibrahem, Ismail
    Casas, Jésus
    Sundén, Henrik
    Plausible origins of homochirality in the amino acid catalyzed neogenesis of carbohydrates2005In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 2005, p. 2047-2049Article in journal (Refereed)
    Abstract [en]

    The intrinsic ability of amino acids to catalyze the asymmetric formation of carbohydrates, which enzymes have mediated for millions of years, with significant amplification of enantiomeric excess suggests a plausible ancient catalytic process for the evolution of homochirality.

  • 212.
    Córdova, Armando
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramón
    The University of Barcelona, Departament Química Orgànica.
    Highly Z- and enantioselective ring-opening/cross-metathesis reactions and Z-selective ring-opening metathesis polymerization2009In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 48, no 47, p. 8827-8831Article in journal (Refereed)
  • 213. Daikoku, S.
    et al.
    Pendrill, Robert
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kanie, Y.
    Ito, Y.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kanie, O.
    Synthesis and structural investigation of a series of mannose-containing oligosaccharides using mass spectrometry2018In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 16, no 2, p. 228-238Article in journal (Refereed)
    Abstract [en]

    A series of compounds associated with naturally occurring and biologically relevant glycans consisting of alpha-mannosides were prepared and analyzed using collision-induced dissociation (CID), energy-resolved mass spectrometry (ERMS), and H-1 nuclear magnetic resonance spectroscopy. The CID experiments of sodiated species of disaccharides and ERMS experiments revealed that the order of stability of mannosyl linkages was as follows: 6-linked > 4-linked >= 2-linked > 3-linked mannosyl residues. Analysis of linear trisaccharides revealed that the order observed in disaccharides could be applied to higher glycans. A branched trisaccharide showed a distinct dissociation pattern with two constituting disaccharide ions. The estimation of the content of this ion mixture was possible using the disaccharide spectra. The hydrolysis of mannose linkages at 3- and 6-positions in the branched trisaccharide revealed that the 3-linkage was cleaved twice as fast as the 6-linkage. It was observed that the solution-phase hydrolysis and gas-phase dissociation have similar energetics.

  • 214. Daikoku, Shusaku
    et al.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kanie, Osamu
    Analysis of a series of isomeric oligosaccharides by energy-resolved mass spectrometry: a challenge on homobranched trisaccharides2009In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 23, no 23, p. 3713-3719Article in journal (Refereed)
  • 215.
    Das, Arindam
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Alam, Rauful
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stereocontrol in Synthesis of Homoallylic Amines. Syn Selective Direct Allylation of Hydrazones with Allylboronic Acids2014In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 16, no 14, p. 3808-3811Article in journal (Refereed)
    Abstract [en]

    Allylboronic acids directly react with acyl hydrazones, affording homoallylic amine derivatives. The reaction proceeds with very high syn selectivity, which is the opposite of the stereochemistry observed for allylboration of imines. The reaction can be carried out with both aromatic and aliphatic acyl hydrazones. Based on our studies the excellent syn stereochemistry can be explained by chelation control of the acyl hydrazone and the B(OH)(2) moiety.

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  • 216.
    Das, Arindam
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Wang, Dong
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Belhomme, Marie-Charlotte
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Copper-Catalyzed Cross-Coupling of Allylboronic Acids with alpha-Diazoketones2015In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 17, no 19, p. 4754-4757Article in journal (Refereed)
    Abstract [en]

    Copper-catalyzed cross-coupling of substituted allylboronic acids with alpha-diazoketones was studied. This allylation reaction is highly regioselective, providing the branched allylic product. The process involves creation of a new C(sp(3))-C(sp(3)) bond by retaining the keto functional group of the alpha-diazoketone precursor.

  • 217. Das, Biswanath
    et al.
    Daver, Henrik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pyrkosz-Bulska, Monika
    Persch, Elke
    Barman, Suman K.
    Mukherjee, Rabindranath
    Gumienna-Kontecka, Elzbieta
    Jarenmark, Martin
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nordlander, Ebbe
    A dinuclear zinc(II) complex of a new unsymmetric ligand with an N(5)0(2) donor set; A structural and functional model for the active site of zinc phosphoesterases2014In: Journal of Inorganic Biochemistry, ISSN 0162-0134, E-ISSN 1873-3344, Vol. 132, p. 6-17Article in journal (Refereed)
    Abstract [en]

    The dinuclear complex [Zn-2(DPCPMP)(pivalate)](C10(4)), where DPCPMP is the new unsymmetrical ligand [2-(N-(3-((bis((pyridin-2-yl)methyl)amino)methyl)-2-hydroxy-5-methylbenzyl)-N-((pyridin2-y1)methyl)amino)acetic acid], has been synthesized and characterized. The complex is a functional model for zinc phosphoesterases with dinuclear active sites. The hydrolytic efficacy of the complex has been investigated using bis-(2,4-dinitrophenyl)phosphate(BDNPP), a DNA analog, as substrate. Speciation studies using potentiometric titrations have been performed for both the ligand and the corresponding dizinc complex to elucidate the formation of the active hydrolysis catalyst; they reveals that the dinuclear zinc(II) complexes, [Zn-2(DPCPMP)](2) and [Zn-2(DPCPMP)(OH)1 predominate the solution above pH 4. The relatively high pKa of 8.38 for water deprotonation suggests that a terminal hydroxide complex is formed. Kinetic investigations of BDNPP hydrolysis over the pH range 5.5-11.0 and with varying metal to ligand ratio (metal salt:ligand = 0.5:1 to 3:1) have been performed. Variable temperature studies gave the activation parameters triangle H double dagger = 95.6 kJ mol(-1), triangle S double dagger = 44.8 J mo1(-1) K-1, and 6,triangle G double dagger = 108.0 kJ mo1-1. The cumulative results indicate the hydroxido-bridged dinuclear Zn(II) complex [Zn-2(DPCPMP)(mu-OH)] (+) as the effective catalyst. The mechanism of hydrolysis has been probed by computational modeling using density functional theory (DFF). Calculations show that the reaction goes through one concerted step (S(N)2 type) in which the bridging hydroxide in the transition state becomes terminal and performs a nucleophilic attack on the BDNPP phosphorus; the leaving group dissociates simultaneously in an overall inner sphere type activation. The calculated free energy barrier is in good agreement with the experimentally determined activation parameters.

  • 218. Das, Biswanath
    et al.
    Daver, Henrik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Singh, Amrendra
    Singh, Reena
    Haukka, Matti
    Demeshko, Serhiy
    Meyer, Franc
    Lisensky, George
    Jarenmark, Martin
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nordlander, Ebbe
    A Heterobimetallic FeIIIMnII Complex of an Unsymmetrical Dinucleating Ligand: A Structural and Functional Model Complex for the Active Site of Purple Acid Phosphatase of Sweet Potato2014In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, Vol. 2014, no 13, p. 2204-2212Article in journal (Refereed)
    Abstract [en]

    The heterodinuclear mixed-valence complex [FeMn(ICIMP)(OAc)(2)Cl] (1) {H2ICIMP = 2-(N-carboxylmethyl)-[N-(N-methylimidazolyl-2-methyl)aminomethyl]-[6-(N-isopropylmethyl)-[N-(N-methylimidazolyl-2-methyl)]aminomethyl-4-methylphenol], an unsymmetrical N4O2 donor ligand} has been synthesized and fully characterized by several spectroscopic techniques as well as by X-ray crystallography. The crystal structure of the complex reveals that both metal centers in 1 are six-coordinate with the chloride ion occupying the sixth coordination site of the Mn-II ion. The phenoxide moiety of the ICIMP ligand and both acetate ligands bridge the two metal ions of the complex. Mossbauer spectroscopy shows that the iron ion in 1 is high-spin Fe-III. Two quasi-reversible redox reactions for the complex, attributed to the (FeMnII)-Mn-III/(FeMnII)-Mn-II (at -0.67 V versus Fc/Fc(+)) and (FeMnII)-Mn-III/(FeMnIII)-Mn-III (at 0.84 V), were observed by means of cyclic voltammetry. Complex 1, with an Fe-III-Mn-II distance of 3.58 angstrom, may serve as a model for the mixed-valence oxidation state of purple acid phosphatase from sweet potato. The capability of the complex to effect organophosphate hydrolysis (phosphatase activity) has been investigated at different pH levels (5.5-11) by using bis(2,4-dinitrophenyl)phosphate (BDNPP) as the substrate. Density functional theory calculations indicate that the substrate coordinates to the Mn-II ion. In the transition state, a hydroxide ion that bridges the two metal ions becomes terminally coordinated to the Fe-III ion and acts as a nucleophile, attacking the phosphorus center of BDNPP with the concomitant dissociation of the leaving group.

  • 219. Das, Biswanath
    et al.
    Lee, Bao-Lin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Karlsson, Erik A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shatskiy, Andrey
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Demeshko, Serhiy
    Liao, Rong-Zhen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Laine, Tanja M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Haukka, Matti
    Zeglio, Erica
    Abdel-Magied, Ahmed F.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Nuclear Materials Authority, Egypt.
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Meyer, Franc
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nordlander, Ebbe
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Water oxidation catalyzed by molecular di- and nonanuclear Fe complexes: importance of a proper ligand framework2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 34, p. 13289-13293Article in journal (Refereed)
    Abstract [en]

    The synthesis of two molecular iron complexes, a dinuclear iron(III,III) complex and a nonanuclear iron complex, based on the di-nucleating ligand 2,2'-(2-hydroxy-5-methyl-1,3-phenylene)bis(1H-benzo[d]imidazole-4-carboxylic acid) is described. The two iron complexes were found to drive the oxidation of water by the one-electron oxidant [Ru(bpy)(3)](3+).

  • 220.
    Daver, Henrik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Quantum Chemical Modeling of Phosphoesterase Mimics and Chemistry in Confined Spaces2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, density functional theory is employed in the study of two kinds of systems that can be considered to be biomimetic in their own ways. First, three binuclear metal complexes, synthesized by the group of Prof. Ebbe Nordlander, have been investigated. The complexes are designed to resemble the active sites of phosphatase enzymes and have been examined in complexes where either two Zn(II) ions or one Fe(III) and one Mn(II) ion are bound. These dinuclear compounds were studied as catalysts for the hydrolysis of bis(2,4-dinitrophenyl) phosphate and the transesterification of 2-hydroxypropyl p-nitrophenyl phosphate, which are model systems for the same reactions occurring in DNA or RNA. It was found that the two reactions take place in similar ways: a hydroxide ion that is terminally bound to one of the metal centers acts either as a nucleophile in the hydrolysis reaction or as a base in the transesterification. The leaving groups depart in an effectively concerted manner, and the formed catalyst-product complexes are predicted to be the resting states of the catalytic cycles. The rate-determining free energy barriers are identified from the catalyst-product complex in one catalytic cycle to the transition state of nucleophilic attack in the next.

    Another type of biomimetic modeling is made with an aim of imitating the conceptual features of selective binding of guests and screening them from solute-solvent interactions. Such features are found in so-called nanocontainers, and this thesis is concerned with studies of two capsules synthesized by the group of Prof. Julius Rebek, Jr. First, the cycloaddition of phenyl acetylene and phenyl azide has experimentally been observed to be accelerated in the presence of a capsule. Computational studies were herein performed on this system, and a previously unrecognized structure of the capsule is discovered. Two main factors are then identified as sources of the rate acceleration compared to the uncatalyzed reaction, namely the reduction of the entropic component and the selective destabilization of the reactant supercomplex over the transition state.

    In the second capsule study, the alkane binding trends of a water-soluble cavitand was studied. It is found that implicit solvation models fail severely in reproducing the experimental equilibrium observed between binding of n-decane by the cavitand monomer and encapsulation in the capsule dimer. A mixed explicit/implicit solvation protocol is developed to better quantify the effect of hydrating the cavitand, and a simple correction to the hydration free energy of a single water molecule is proposed to remedy this. The resulting scheme is used to predict new hydration free energies of the cavitand complexes, resulting in significant improvement vis-à-vis experiments.

    The computational results presented in this thesis show the usefulness of the quantum chemical calculations to develop understanding of experimental trends observed for substrate binding and catalysis. In particular, the methodology is shown to be versatile enough such that experimental observations can be reproduced for such diverse systems as studied herein.

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    Quantum Chemical Modeling of Phosphoesterase Mimics and Chemistry in Confined Spaces
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    Errata - Quantum Chemical Modeling of Posphoesterase Mimics and Chemistry in Confined Spacces
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  • 221.
    Daver, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Algarra, Andrés G.
    Rebek, Jr., Julius
    Harvey, Jeremy N.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Toward Accurate Quantum Chemical Modeling of Water-Soluble Self-Assembled CapsulesManuscript (preprint) (Other academic)
  • 222.
    Daver, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Das, Biswanath
    Nordlander, Ebbe
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Theoretical Study of Phosphodiester Hydrolysis and Transesterification Catalyzed by an Unsymmetric Biomimetic Dizinc Complex2016In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 55, no 4, p. 1872-1882Article in journal (Refereed)
    Abstract [en]

    Density functional theory calculations have been used to investigate the reaction mechanisms of phosphodiester hydrolysis and transesterification catalyzed by a dinuclear zinc complex of the 2-(N-isopropyl-N-((2-pyridyl)methyl)-aminomethyl)-6-(N-(carboxylmethyl)-N-((2-pyridyl)methyl)amino-methyl)-4-methylphenol (IPCPMP) ligand, mimicking the active site of zinc phosphotriesterase. The substrates bis(2,4)-dinitrophenyl phosphate (BDNPP) and 2-hydroxypropyl-p-nitrophenyl phosphate (HPNP) were employed as analogues of DNA and RNA, respectively. A number of different mechanistic proposals were considered, with the active catalyst harboring either one or two hydroxide ions. It is concluded that for both reactions the catalyst has only one hydroxide bound, as this option yields lower overall energy barriers. For BDNPP hydrolysis, it is suggested that the hydroxide acts as the nucleophile in the reaction, attacking the phosphorus center of the substrate. For HPNP transesterification, on the other hand, the hydroxide is proposed to act as a Bronsted base, deprotonating the alcohol moiety of the substrate, which in turn performs the nucleophilic attack. The calculated overall barriers are in good agreement with measured rates. Both reactions are found to proceed by essentially concerted associative mechanisms, and it is demonstrated that two consecutive catalytic cycles need to be considered in order to determine the rate-determining free energy barrier.

  • 223.
    Daver, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Harvey, Jeremy N.
    Rebek, Jr., Julius
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Quantum Chemical Modeling of Cycloaddition Reaction in a Self-Assembled Capsule2017In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 139, no 43, p. 15494-15503Article in journal (Refereed)
    Abstract [en]

    Dispersion-corrected density functional theory is used to study the cycloaddition reaction between phenyl acetylene and phenyl azide inside a synthetic, self-assembled capsule. The capsule is first characterized computationally and a previously unrecognized structure is identified as being the most stable. Next, an examination of the free energies of host-guest complexes is conducted, considering all possible reagent, solvent and solvent impurity combinations as guests. The experimentally observed relative stabilities of host-guest complexes are quite well reproduced, when the experimental concentrations are taken into account. Experimentally, the presence of the host capsule has been shown to accelerate the cycloaddition reaction and to yield exclusively the 1,4-regioisomer product. Both these observations are reproduced by the calculations. A detailed energy decomposition analysis shows that reduction of the entropic cost of bringing together the reactants along with a geometric destabilization of the reactant supercomplex are the major contributors to the rate acceleration compared to the background reaction. Finally, a sensitivity analysis is conducted to assess the stability of the results with respect to the choice of methodology.

  • 224.
    Deiana, Luca
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Development of Catalytic Enantioselective Approaches for the Synthesis of Carbocycles and Heterocycles2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In biological systems, most of the active organic molecules are chiral. Some of the main constituents of living organisms are amino acids and sugars. They exist predominantly in only one enantiomerically pure form. For example, our proteins are built-up by L-amino acids and as a consequence they are enatiomerically pure and will interact in different ways with enantiomers of chiral molecules. Indeed, different enantiomers or diastereomers of a molecule could often have a drastically different biological activity. It is of paramount importance in organic synthesis to develop new routes to control and direct the stereochemical outcome of reactions. The aim of this thesis is to investigate new protocols for the synthesis of complex chiral molecules using simple, environmentally friendly proline-based organocatalysts. We have investigated, the aziridination of linear and branched enals, the stereoselective synthesis of β-amino acids with a carbene co-catalyst, the synthesis of pyrazolidines, the combination of heterogeneous transition metal catalysis and amine catalysis to deliver cyclopentenes bearing an all-carbon quaternary stereocenter and a new heterogeneous dual catalyst system for the carbocyclization of enals. The reactions presented in this thesis afforded the corresponding products with high levels of chemo-, diastero- and enantioselectivity.

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    PhD Thesis Luca Deiana
  • 225.
    Deiana, Luca
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Afewerki, Samson
    Palo-Nieto, Carlos
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Cordova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Mid Sweden University.
    Highly Enantioselective Cascade Transformations by Merging Heterogeneous Transition Metal Catalysis with Asymmetric Aminocatalysis2012In: Scientific Reports, E-ISSN 2045-2322, Vol. 2, p. 851-Article in journal (Refereed)
    Abstract [en]

    The concept of combining heterogeneous transition metal and amine catalysis for enantioselective cascade reactions has not yet been realized. This is of great advantage since it would allow for the recycling of expensive and non-environmentally friendly transition metals. We disclose that the use of a heterogeneous Pd-catalyst in combination with a simple chiral amine co-catalyst allows for highly enantioselective cascade transformations. The preparative power of this process has been demonstrated in the context of asymmetric cascade Michael/carbocyclization transformations that delivers cyclopentenes bearing an all carbon quaternary stereocenters in high yields with up to 30: 1 dr and 99% ee. Moreover, a variety of highly enantioselective cascade hetero-Michael/carbocyclizations were developed for the one-pot synthesis of valuable dihydrofurans and pyrrolidines (up to 98% ee) by using bench-stable heterogeneous Pd and chiral amines as co-catalysts.

  • 226. Deiana, Luca
    et al.
    Badali, Elham
    Rafi, Abdolrahim A.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Mid Sweden University, Sundsvall, Sweden.
    Cordova, Armando
    Cellulose-Supported Heterogeneous Gold-Catalyzed Cycloisomerization Reactions of Alkynoic Acids and Allenynamides2023In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 13, no 15, p. 10418-10424Article in journal (Refereed)
    Abstract [en]

    Herein, we describe efficient nanogold-catalyzed cycloisomerization reactions of alkynoic acids and allenynamides to enol lactones and dihydropyrroles, respectively (the latter via an Alder-ene reaction). The gold nanoparticles were immobilized on thiol-functionalized microcrystalline cellulose and characterized by electron microscopy (HAADF-STEM) and by XPS. The thiol-stabilized gold nanoparticles (Au-0) were obtained in the size range 1.5-6 nm at the cellulose surface. The robust and sustainable cellulose-supported gold nanocatalyst can be recycled for multiple cycles without losing activity.

  • 227.
    Deiana, Luca
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ibrahem, Ismail
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramon
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic asymmetric aziridination of α, β- unsaturated aldehydes2011In: Abstracts of Papers, 242nd ACS National Meeting & Exposition, Denver, CO, United States, August 28-September 1, 2011, American Chemical Society , 2011Conference paper (Other academic)
    Abstract [en]

    The development, scope and application of the highly enantioselective organocatalytic aziridination of a, b- unsaturated aldehydes is presented. The aminocatalytic aziridination of a, b- unsaturated aldehydes enables the asymmetric formation of b-formylaziridines with up to >19:1 dr and 99% ee. The aminocatalytic aziridination of a-monosobstituted enals gives access to terminal a-substituted-a-formyl aziridines in high yields and up to 99% ee. In the case of the organocatalytic aziridination of disubstituted a, b-unsaturated aldehydes, the transformations gives nearly enantiomeric pure b-formyl-functionalized aziridine products. A higly enantioselective one-pot cascade sequence based on combination of asymmetric amine and N-heterocyclic carbene catalysis is also disclosed. This transformation gives the corresponding N-Boc and N-Cbz protected b-amino acid esters with ee´s ranging from 92-99%.

  • 228.
    Deiana, Luca
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ullah, Farman
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lin, Shuangzheng
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dynamic kinetic asymmetric transformation (DYKAT) by combination of amine and transition metal cascade catalysis2010In: Abstracts of Papers, 239th ACS National Meeting, San Francisco, CA, United States, March 21-25, 2010, Washington, D C: American Chemical Society , 2010Conference paper (Other academic)
  • 229.
    Deiana, Luca
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vesely, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ibrahem, Ismail
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramón
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic asymmetric aziridination of α,β-unsaturated aldehydes2011In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 28, p. 7904-7917Article in journal (Refereed)
    Abstract [en]

    The development, scope, and application of the highly enantioselective organocatalytic aziridination of α,β-unsaturated aldehydes is presented. The aminocatalytic azirdination of α,β-unsaturated aldehydes enables the asymmetric formation of β-formyl aziridines with up to >19:1 d.r. and 99% ee. The aminocatalytic aziridination of α-monosubstituted enals gives access to terminal α-substituted-α-formyl aziridines in high yields and upto 99% ee. In the case of the organocatalytic aziridination of disubstituted α,β-unsaturated aldehydes, the transformations were highly diastereo- and enantioselective and give nearly enantiomerically pure β-formyl-functionalized aziridine products (99% ee). A highly enantioselective one-pot cascade sequence based on the combination of asymmetric amine and N-heterocycliccarbene catalysis (AHCC) is also disclosed. This one-pot three-component co-catalytic transformation between α,β-unsaturated aldehydes, hydroxylamine derivatives, and alcohols gives the corresponding N-tert-butoxycarbonyl and N-carbobenzyloxy-protected β-amino acid esters with ee values ranging from 92–99%. The mechanisms and stereochemistry of all these catalytic transformations are also discussed.

  • 230.
    Deiana, Luca
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ghisu, Lorenza
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Afewerki, Samson
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bacsik, Zoltan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Mid-Sweden University, Sweden.
    Enantioselective Heterogeneous Synergistic Catalysis for Asymmetric Cascade Transformations2014In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 356, no 11-12, p. 2485-2492Article in journal (Refereed)
    Abstract [en]

    A modular design for a novel heterogeneous synergistic catalytic system, which simultaneously activates the electrophile and nucleophile by the combined activation modes of a separate metal and non-metal catalyst, for asymmetric cascade transformations on a solid surface is disclosed. This modular catalysis strategy generates carbocycles (up to 97.5: 2.5 er) as well as spirocyclic oxindoles (97.5: 2.5 to > 99: 0.5 er), containing all-carbon quaternary centers, in a highly enantioselective fashion via a one-pot dynamic relay process.

  • 231.
    Deiana, Luca
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dziedzik, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramón
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vesely, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ekström, Jesper
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    One-pot highly enantioselective catalytic Mannich-type reactions between aldehydes and stable α-amido sulfones: asymmetric synthesis of β-amino aldehydes and β-amino acids2010In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 51, no 2, p. 234-237Article in journal (Refereed)
    Abstract [en]

    A highly enantioselective catalytic route to carbamate- and benzoate-protected beta-amino aldehydes and beta-amino acids is presented. The amino acid-catalyzed one-pot asymmetric reaction between unmodified aldehydes and alpha-amido sulfones gives the corresponding beta-amino compounds with up to 95:5 dr and 97-99%

  • 232.
    Deiana, Luca
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Leijonmarck, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Lehmann, Christian W.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Mid Sweden University, Sweden.
    Direct Catalytic Asymmetric Synthesis of Pyrazolidine Derivatives2012In: ChemistryOpen, ISSN 2191-1363, Vol. 1, no 3, p. 134-139Article in journal (Refereed)
    Abstract [en]

    A highly enantioselective, metal-free cascade reaction between di-1,2-N-protected hydrazine and α,β-unsaturated aldehydes is disclosed. The catalytic, asymmetric cascade transformation is a direct entry to 3-hydroxypyrazolidine and 3-allylpyrazolidine derivatives in one step and two steps, respectively, with >19:1 d.r. and 98–99 % ee using simple chiral pyrrolidines as catalysts.

  • 233.
    Deiana, Luca
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lin, Shuangzheng
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhang, Qiong
    Leijonmarck, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Organocatalytic enantioselective aziridination of α-substituted α,β-unsaturated aldehydes: asymmetric synthesis ot terminal aziridines2010In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 352, no 18, p. 3201-3207Article in journal (Refereed)
    Abstract [en]

    The first example of a highly enantioselective organocatalytic aziridination of α-substituted α,β-unsaturated aldehydes is presented. The reaction is catalyzed by simple chiral amines and gives access to highly functional terminal azirdines containing an α-tertiary amine stereocenter in high yields and enantiomeric ratios (95.5:4.5–98:2).

  • 234.
    Deliaval, Marie
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of chiral allyl and propargyl boronates by organocatalytic carbene insertion to carbon-boron bonds2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes the development of a novel organocatalytic method for the synthesis of chiral allyl- and propargyl- organoboron compounds with high enantioselectivity. These organoboron species are versatile building blocks in asymmetric synthesis.

    We have developed a new efficient homologation method of alkenyl boronic acids. This reaction affords enantiomerically enriched trifluoromethylated allylboronates. These organoboron species were used in allylboration of carbonyl compounds, imines and indole derivatives. The reactions proceeded with a remarkably high stereoselectivity to give homoallylic alcohols and amines. In addition, the chiral allylboronic acids can be oxidized to the corresponding alcohols with retention of the configuration.

    Based on the homologation of alkenylboronic acids a new three-component reaction is developed. This reaction involved coupling of alkynyl boronates, diazo compounds and ketones in the presence of chiral organocatalysts. This coupling proceeds with high selectivity under mild reaction conditions. The three-component coupling reaction is based on a homologation–allylboration sequence. The process is suitable for synthesis of CF3- and TMS-substituted allenols with excellent diastereo- and enantioselectivity. Application of aromatic, cyclic and non-cyclic ketones leads to formation of chiral tertiary allenols.

    We have also studied the effects of boronic acid esters on the outcome of the homologation reaction. It was found that a facile transesterification of the boronate precursors with the organocatalyst, BINOL derivatives, is a prerequisite of the successful homologation reaction.

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  • 235.
    Deng, Hong-Ping
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Wang, Dong
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Direct Allylation of Quinones with Allylboronates2015In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 80, no 6, p. 3343-3348Article in journal (Refereed)
    Abstract [en]

    Allylboronates undergo C-H allylation of unsubstituted or monosubstituted benzoquinone and naphthoquinone substrates. In the case of 2,5- or 2,6-disubstituted quinones addition involving the substituted carbon takes place. Allylation with stereodefined allylboronates occurs with retention of the configuration.

  • 236.
    Deng, Youqian
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bartholomeyzik, Teresa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Persson, Andreas K. A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Junliang
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-Catalyzed Oxidative Arylating Carbocyclization of Allenynes2012In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 51, no 11, p. 2703-2707Article in journal (Refereed)
  • 237.
    Deng, Youqian
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-Catalyzed Oxidative Acyloxylation/Carbocyclization of Allenynes2013In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 52, no 11, p. 3217-3221Article in journal (Refereed)
  • 238.
    Deska, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enzymatic kinetic resolution of primary allenic alcohols. Application to the total synthesis and stereochemical assignment of striatisporolide A2009In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 7, no 17, p. 3379-3381Article in journal (Refereed)
  • 239.
    Deska, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    del Pozo Ochoa, Carolina
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Chemoenzymatic dynamic kinetic resolution of axially chiral allenes2010In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 16, no 15, p. 4447-4451Article in journal (Refereed)
    Abstract [en]

    Dimeric palladium bromide complexes bearing monodentate N-heterocyclic carbene ligands have been identified as efficient catalysts for the chemoselective racemization of axially chiral allenyl alcohols. In combination with porcine pancreatic lipase as biocatalyst, a dynamic kinetic resolution has been developed, giving access to optically active allenes in good yield and high enantiomeric purity (

  • 240.
    Dey, Chandan
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lindstedt, Erik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Wallenberg Research Centre at Stellenbosch University, South Africa.
    Metal-Free C-Arylation of Nitro Compounds with Diaryliodonium Salts2015In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 17, no 18, p. 4554-4557Article in journal (Refereed)
    Abstract [en]

    An efficient, mild, and metal-free arylation of nitro-alkanes with diaryliodonium salts has been developed, giving easy access to tertiary nitro compounds. The reaction proceeds in high yields without the need for excess reagents and can be extended to alpha-arylation of nitroesters. Nitroalkanes were selectively C-arylated in the presence of other easily arylated functional groups, such as phenols and aliphatic alcohols.

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  • 241.
    Di Francesco, Davide
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic valorization of lignocellulose: Direct and sidestream upgrading approaches2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This work aims to explore different approaches for the valorization of lignocellulosic biomass. In this regard, two different strategies are presented: the catalytic upgrading of lignocellulose derivatives from industrial streams, such as pyrolytic oil and kraft lignin, and the direct catalytic fractionation of woody biomass. The first approach is explored in Paper I and II, while the second in Paper III and IV.

    Different phenolic compounds were hydro-dearomatized using a heterogeneous catalytic system based on Pd/C and polymethylhydrosiloxane/H2O as a liquid hydrogen source. High yields of either cyclohexanones or cyclohexanols were achieved in high selectivity by varying the concentration of water. To prove the broad applicability of the method, commercially available bio-oils such as beechwood tar creosote and cardanol oil underwent hydrodearomatization using the developed catalytic systems (Paper I).

    Kraft lignin, a byproduct of the paper manufacturing industry, has been valorized by steering its solubility properties through the production of a lipophilic lignin oil suitable for hydrotreatment. The enhanced solubility allowed its blending in common refinery carriers and full hydrodeoxygenation yielding hydrocarbons in the gasoline-diesel range. A particular focus was set on the mechanistic study of the esterification where a 13C labeling analysis was performed (Paper II).

    Untreated birch wood was fractionated into its components while lignin was consequently depolymerized into monophenolic compounds. Cobalt was scrutinized to replace noble metals in reductive catalytic fractionation by synthetizing a heterogeneous catalyst supported on nitrogen-doped carbon. We found that adjusting the pH of the reaction medium affected the yields of the reaction. Under optimized conditions, monophenolic compounds could be obtained in up to 34 wt% yield relative to initial lignin. The role of the catalyst and reductants was investigated (Paper III).

    The last chapter describes a pulping system able to parallelly perform the glucan purification and the catalytic upgrade of the lignin by-products while avoiding the contamination of the pulp with the heterogeneous catalyst. The system is based on a high-pressure Soxhlet combined with the ethanol-water organosolv, where Pd/C was selected as the heterogeneous catalyst. Using only CO2 as the acid source, lyocell grade dissolving pulp was produced in addition to lignin oil (Paper IV).

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  • 242.
    Di Tommaso, Ester Maria
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthetic and Mechanistic Studies with Iodine(III) Reagents2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes the development of metal-free transformations and mechanistic studies on the reactivity of two classes of hypervalent iodine reagents: diaryliodonium salts and vinylbenziodoxolones (VBX). Recently, they have been recognized as valuable synthetic reagents with broad applicability in organic synthesis. Moreover, hypervalent iodine reagents are non-toxic compounds and sustainable alternatives to heavy metals. In Chapter 1, an overview of hypervalent iodine(III) compounds is provided, with emphasis on the reagents that have been used in the thesis. First, the synthesis and general reactivity of diaryliodonium salts is described. Vinylbenziodoxolones are presented as a novel class of iodine(III) compounds that are powerful electrophilic vinylating reagents. Finally, a brief description of density functional theory and computational methods used in this thesis are outlined. The synthesis and applications of azobenzene-derived diaryliodonium salts is the topic of Chapter 2. The novel iodonium reagents were employed in chemoselective arylation reactions with a wide range of C, N, O and S-nucleophiles under mild and metal-free conditions. In Chapter 3, a mild and transition metal-free vinylation of thiols and mercapto heterocycles using vinylbenziodoxolones reagents is presented. The method allows the synthesis of a wide variety of S-vinylated products with complete chemo-, regio- and stereoselectivity. In Chapter 4, the first mechanistic investigation of VBX vinylations is presented. By exploiting the use of NMR analysis, deuterium labelling and DFT calculations, the observed regio- and stereochemical outcome of the vinylations of sulfur and phosphorous nucleophiles with VBX reagents has been rationalized. A transition metal-free, photocatalyzed C-vinylation method using VBX reagents is described in Chapter 5. The reactions proceed under mild conditions and the method tolerates a series of functional groups that lead to straightforward access to corresponding alkenes in good to high yields with high stereoselectivity.

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  • 243.
    Di Tommaso, Ester Maria
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Walther, Melanie
    University of Bremen, MAPEX Center for Materials and Processes.
    Staubitz, Anne
    University of Bremen, Institute for Analytical and Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ortho-Functionalization of Azobenzenes via Hypervalent Iodine ReagentsManuscript (preprint) (Other academic)
    Abstract [en]

    Ortho-functionalized azobenzenes are much sought-after molecular switches. They may be tuned to absorb in the visible range of light and in many cases, the Z-isomers have very high thermal half-lives. However, methods to introduce substituents in ortho-position are still rare. This work presents the synthesis of azobenzenes with an iodine(III) moiety in the ortho-position. This novel class of diaryliodonium salts is demonstrated to efficiently arylate oxygen, nitrogen, carbon and sulfur nucleophiles under metal-free conditions. Selective transfer of the azobenzene moiety to the nucleophile gives access to an unprecedented range of ortho-substituted azobenzenes. In addition, the structure of these versatile reagents has been analyzed by X-ray crystallography and their photo-switching properties were investigated by NMR and UV-vis spectroscopy.

  • 244. Dorau, Robin
    et al.
    Görbe, Tamás
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Svedendahl Humble, Maria
    Improved Enantioselectivity of Subtilisin Carlsberg Towards Secondary Alcohols by Protein Engineering2018In: ChemBioChem (Print), ISSN 1439-4227, E-ISSN 1439-7633, Vol. 19, no 4, p. 338-346Article in journal (Refereed)
    Abstract [en]

    Generally, the catalytic activity of subtilisin Carlsberg (SC) for transacylation reactions with secondary alcohols in organic solvent is low. Enzyme immobilization and protein engineering was performed to improve the enantioselectivity of SC towards secondary alcohols. Possible amino-acid residues for mutagenesis were found by combining available literature data with molecular modeling. SC variants were created by site-directed mutagenesis and were evaluated for a model transacylation reaction containing 1-phenylethanol in THF. Variants showing high E values (>100) were found. However, the conversions were still low. A second mutation was made, and both the E values and conversions were increased. Relative to that shown by the wild type, the most successful variant, G165L/M221F, showed increased conversion (up to 36 %), enantioselectivity (E values up to 400), substrate scope, and stability in THF.

  • 245.
    Dorst, Kevin M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Deciphering Carbohydrate Structure: From NMR Chemical Shifts to Conformational Analysis2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Carbohydrates are ubiquitous in nature and exhibit a multitude of roles. Besides nucleic and amino acids, they can be regarded as the third alphabet of life. They are used as energy source to fuel the cells, as structural building blocks and play a key role in cellular recognition processes. Compared to the other two groups of biomacromolecules, carbohydrates display a higher level of structural complexity by virtue of the number of individual monosaccharide building blocks, as well as the greater number of possibilities of connecting them and additional modifications. This renders a high information content and a good understanding of the structure-function relationship of glycans is important, since the presence or absence of specific structures can make the difference between health and disease.

    Carbohydrate structures can be characterized and studied by NMR spectroscopy at the atomic level. This process is time-consuming and error-prone, due to the narrow spectral window, in which most carbohydrate resonances are located leading to severe spectral overlap. Computer programs have been developed, aiding this process. This thesis investigates the quality of prediction of NMR chemical shifts of glycopeptides, highly branched oligosaccharide structures and those bearing a non-natural organic aglycone at the reducing end, as well as the automated determination of primary carbohydrate structures from unassigned NMR spectroscopic data thereof. Novel developments of the CASPER program are highlighted.

    The three-dimensional structure of carbohydrates plays an important role during carbohydrate-protein interactions. This thesis investigates the conformational preferences and dynamics of glycan structures ranging from di- to tetrasaccharides. A particular focus lies on the measurement of transglycosidic 3JCH coupling constants by NMR. Furthermore, the experimental spectroscopic data is compared to results from MD simulations.

    Synthetic carbohydrate chemistry has a strong focus on stereoselective C−O bond formation for the synthesis of oligo- and polysaccharides. Each glycosylation reaction can produce two stereoisomeric structures. To date, the mechanistic pathway of glycosylation reactions is still not fully understood, since many different parameters influence the stereoselectivity. A combined experimental and computational study exploring the role of the solvent is presented and a linear correlation of the selectivity with a solvatochromic parameter for the polarizability of the solvent was found.

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  • 246. Dorst, Kevin M.
    et al.
    Engstöm, Olof
    Angles d'Ortoli, Thibault
    Mobarak, Hani
    Ebrahemi, Azad
    Fagerberg, Ulf
    Whitfield, Dennis M.
    Widmalm, Göran
    On the Influence of Solvent on the Stereoselectivity of Glycosylation ReactionsManuscript (preprint) (Other academic)
    Abstract [en]

    Methodology development in carbohydrate chemistry entails the stereoselective formation of C–O bonds as a key step in the synthesis of oligo- and polysaccharides. The anomeric selectivity of aglycosylation reaction is affected by a multitude of parameters, such as the nature of the donor andacceptor, activator/promotor system, temperature and solvent. The influence of different solvents onthe stereoselective outcome of glycosylation reactions employing thioglucopyranosides as glycosyldonors with a non-participating protecting group at position 2 has been studied. A large change inselectivity as a function of solvent was observed and a correlation between selectivity and the Kamlet-Taft solvent parameter π* was found. Furthermore, molecular modeling using density functionaltheory methodology was conducted to decipher the role of the solvent and possible reaction pathwayswere investigated.

  • 247. Dorst, Kevin M.
    et al.
    Widmalm, Göran
    Conformational preferences at the glycosidic linkage of disaccharides in solution as deduced from NMR experiments and MD simulations: comparison to crystal structuresManuscript (preprint) (Other academic)
    Abstract [en]

    Glycans are central to information content and regulation in biological systems. These carbohydrate molecules are active either as oligo- or polysaccharides, often in the form of glycoconjugates. The monosaccharide entities are joined by glycosidic linkages and stereochemical arrangements are of utmost importance in determining conformation and flexibility of saccharides. The conformational preferences and population distributions at the glycosidic torsion angles f and y have been investigated for three disaccharides where the substitution takes place at a secondary alcohol, viz., in a-l-Fucp-(1→3)-β-d-Glcp-OMe, a-l-Fucp-(1→3)-a-d-Galp-OMe and a-d-Glcp-(1→4)-a-d-Galp-OMe. Stereochemical differences at or adjacent to the glycosidic linkage were explored by solution state NMR spectroscopy using one‑dimensional 1H,1H-NOESY NMR experiments to obtain transglycosidic proton‑proton distances and one- and two-dimensional heteronuclear NMR experiments to obtain 3JCH transglycosidic coupling constants related to torsion angles f and y. Computed effective proton‑proton distances from molecular dynamics (MD) simulations showed excellent agreement to experimentally derived distances for the a-(1→3)-linked disaccharides and revealed that for the bimodal distribution at the y torsion angle for the a-(1→4)-linked disaccharide experiment and simulation were at variance with each other, calling for further force field developments. The MD simulations disclosed a highly intricate inter‑residue hydrogen bonding pattern for the a-(1→4)-linked disaccharide, including a nonconventional hydrogen bond between H5' in the glucosyl residue and O3 in the galactosyl residue, supported by a large downfield 1H NMR chemical shift displacement compared to a-d-Glcp-OMe. Comparison of population distributions of the glycosidic torsion angles f and y in the disaccharide entities to those of corresponding crystal structures highlighted the potential importance of solvation on the preferred conformation. 

  • 248. Dorst, Kevin M.
    et al.
    Widmalm, Göran
    NMR chemical shifts prediction of glycopeptides and glycoproteins aided by the computer program CASPERManuscript (preprint) (Other academic)
    Abstract [en]

    In posttranslational modifications of proteins and peptides by glycosylation the two major classes are N-linked and O-linked glycans. The sugar residue proximal to the peptide chain is in N-glycans linked to l-asparagine and in O-linked glycans it is linked to either l-serine, l-threonine or l-tyrosine, although other amino acids may be glycosylated. Identifying and assigning the 1H and 13C NMR chemical shifts of these glycoconjugates are a prerequisite for structural characterization as well as for subsequent conformational and interaction studies thereof. The web-based computer program CASPER (http://www.casper.organ.su.se/casper) is a tool that provides prediction of 1H and 13C NMR chemical shift for glycans, as well as those linked to l-Asn, l-Ser, l-Thr or l-Tyr, for which the predicted NMR chemical shifts of the glycan show good agreement to those from NMR experiments of glycopeptides and glycoproteins. This highlights that an approximation in which a single amino acid is present at the reducing end of the glycan structure is sufficient to predict NMR data well, as shown for different N-linked and O-linked glycans of various complexity.

  • 249.
    Dorst, Kevin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Conformational Preferences at the Glycosidic Linkage of Saccharides in Solution as Deduced from NMR Experiments and MD Simulations: Comparison to Crystal Structures2024In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765Article in journal (Refereed)
    Abstract [en]

    Glycans are central to information content and regulation in biological systems. These carbohydrate molecules are active either as oligo- or polysaccharides, often in the form of glycoconjugates. The monosaccharide entities are joined by glycosidic linkages and stereochemical arrangements are of utmost importance in determining conformation and flexibility of saccharides. The conformational preferences and population distributions at the glycosidic torsion angles phi and psi have been investigated for O-methyl glycosides of three disaccharides where the substitution takes place at a secondary alcohol, viz., in alpha-l-Fucp-(1 -> 3)-beta-d-Glcp-OMe, alpha-l-Fucp-(1 -> 3)-alpha-d-Galp-OMe and alpha-d-Glcp-(1 -> 4)-alpha-d-Galp-OMe, corresponding to disaccharide structural elements present in bacterial polysaccharides. Stereochemical differences at or adjacent to the glycosidic linkage were explored by solution state NMR spectroscopy using one-dimensional 1H,1H-NOESY NMR experiments to obtain transglycosidic proton-proton distances and one- and two-dimensional heteronuclear NMR experiments to obtain 3JCH transglycosidic coupling constants related to torsion angles phi and psi. Computed effective proton-proton distances from molecular dynamics (MD) simulations showed excellent agreement to experimentally derived distances for the alpha-(1 -> 3)-linked disaccharides and revealed that for the bimodal distribution at the psi torsion angle for the alpha-(1 -> 4)-linked disaccharide experiment and simulation were at variance with each other, calling for further force field developments. The MD simulations disclosed a highly intricate inter-residue hydrogen bonding pattern for the alpha-(1 -> 4)-linked disaccharide, including a nonconventional hydrogen bond between H5 ' in the glucosyl residue and O3 in the galactosyl residue, supported by a large downfield 1H NMR chemical shift displacement compared to alpha-d-Glcp-OMe. Comparison of population distributions of the glycosidic torsion angles phi and psi in the disaccharide entities to those of corresponding crystal structures highlighted the potential importance of solvation on the preferred conformation. The importance of solvation on the preferred conformation of saccharides in solution and in crystals is unraveled by solution-state NMR and computational MD studies of solvated disaccharides. Crystal structures containing solvated glycan structures have glycosidic linkage conformations similar to those of the carbohydrate molecules in solution. 

  • 250.
    Dorst, Kevin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    NMR chemical shift prediction and structural elucidation of linker-containing oligo- and polysaccharides using the computer program CASPER2023In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 533, article id 108937Article in journal (Refereed)
    Abstract [en]

    Carbohydrate structures containing alkyl groups as aglycones are useful for investigating enzyme activity and glycan-protein interactions. Moreover, linker-containing oligosaccharides with a spacer group are commonly used to print glycan microarrays or to prepare protein-conjugates as vaccine candidates. The structural accuracy of these synthesized glycans are essential for interpretation of results from biological experiments in which the compounds have been used and NMR spectroscopy can unravel and confirm their structures. An approach for efficient 1H and 13C NMR chemical shift assignments employed a parallel NOAH-10 measurement followed by NMR spin-simulation to refine the 1H NMR chemical shifts, as exemplified for a disaccharide with an azidoethyl group as an aglycone, the NMR chemical shifts of which have been used to enhance the quality of CASPER (http://www.casper.organ.su.se/casper/). The CASPER program has been further developed to aid characterization of linker-containing oligo- and polysaccharides, either by chemical shift prediction for comparison to experimental NMR data or as structural investigation of synthesized glycans based on acquired unassigned NMR data. The ability of CASPER to elucidate structures of linker-containing oligosaccharides is demonstrated and comparisons to assigned or unassigned NMR data show the utility of CASPER in supporting a proposed oligosaccharide structure. Prediction of NMR chemical shifts of an oligosaccharide, corresponding to the repeating unit of an O-antigen polysaccharide, having a linker as an aglycone and a non-natural substituent derivative thereof are presented to exemplify the diversity of structures handled. Furthermore, NMR chemical shift predictions of synthesized polysaccharides, corresponding to bacterial polysaccharides, containing a linker are described showing that in addition to oligosaccharide structures also polysaccharide structures having an aglycone spacer group can be analyzed by CASPER.

2345678 201 - 250 of 1257
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