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  • 251. Eriksson, Lars
    et al.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Methyl α-l-rhamnosyl-(1→2)[α-l-rhamnosyl-(1→3)]-α-l-rhamnoside penta­hydrate: synchrotron study2012Inngår i: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 68, nr 7, s. o2221-o2222Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The title hydrate, C19H34O13·5H2O, contains a vicinally disubstituted tris­accharide in which the two terminal rhamnosyl sugar groups are positioned adjacent to each other. The conformation of the tris­accharide is described by the glycosidic torsion angles ϕ2 = 48 (1)°, ψ2 = −29 (1)°, ϕ3 = 44 (1)° and ψ3 = 4 (1)°, whereas the ψ2 torsion angle represents a conformation from the major state in solution, the ψ3 torsion angle conformation may have been caught near a potential energy saddle-point when compared to its solution structure, in which at least two but probably three conformational states are populated. Extensive inter­molecular O—HO hydrogen bonding is present in the crystal and a water-containing channel is formed along the b-axis direction.

  • 252.
    Fontana, Carolina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    NMR spectroscopy in structural and conformational analysis of bacterial polysaccharides2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Carbohydrates constitute one of the three major classes of biomolecules found in all living cells and, unlike nucleic acids and proteins, their polymeric structures are not based on a template. The structural diversity of these molecules confers them an enormous capacity to encode information in biological systems, acting as efficient mediators in the interaction of the cell with the environment. In order to understand the roles of glycans in biological processes it is of key importance to have a detailed understanding of their structures and conformational preferences, and NMR spectroscopy is one of most powerful techniques for the study of these molecules in solution.

    This thesis is focused on the structural and conformational analysis of lipopolysaccharides from Gram-negative bacteria. In the first two projects (Chapter 2 and 3) the structural analyses of the biological repeating units of the O-antigen polysaccharides from E. coli O174ab and O115 are described; in both cases a combination of NMR spectroscopy and gas chromatography techniques were used. Special emphasis was made in the characterization of the O-acetylation patterns observed in the native O-antigen polysaccharide from E. coli O115. Chapter 4 describes the development of a new methodology for the determination of the absolute configuration of monosaccharide components of glycans. This methodology was used in the structural elucidation of the O-antigen PS of E. coli O155 (Chapter 5) that was carried out in a semi-automated manner using the program CASPER and unassigned NMR data. The conformational preferences of O-antigen PS of E. coli O5ac and O5ab are analyzed in Chapter 6, using a combination of NMR spectroscopy and molecular modeling methods. In Chapter 7 the structural analysis is focused on the core region of the LPS, and the structures of the deacylated lipooligosaccharides of three rough mutants of B. melitesis are reported. In several of the aforementioned chapters, the biosynthetic aspects behind the assembly of the respective PSs were examined on the bases of genetic information available in the NCBI and ECODAB databases.  Finally, in Chapter 8, different NMR pulse sequences available for the study of proteins and nucleic acids were evaluated and optimized for the structural analysis of 13C uniformly-labeled oligo- and polysaccharides.

  • 253.
    Fontana, Carolina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural studies of glycans by NMR spectroscopy2012Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 254.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Conde-Alvarez, Raquel
    Ståhle, Jonas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Holst, Otto
    Iriarte, Maite
    Zhao, Yun
    Arce-Gorvel, Vilma
    Hanniffy, Sean
    Gorvel, Jean-Pierre
    Moriyon, Ignacio
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural Studies of Lipopolysaccharide-defective Mutants from Brucella melitensis Identify a Core Oligosaccharide Critical in Virulence2016Inngår i: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 291, nr 14, s. 7727-7741Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structures of the lipooligosaccharides from Brucella melitensis mutants affected in the WbkD and ManB(core) proteins have been fully characterized using NMR spectroscopy. The results revealed that disruption of wbkD gives rise to a rough lipopolysaccharide (R-LPS) with a complete core structure (beta-D-Glcp-(1 -> 4)-alpha-Kdop-(2 -> 4)[beta-D-GlcpN-(1 -> 6)-beta-D-GlcpN-(1 -> 4)[beta-D-GlcpN-(1 -> 6)]-beta-D-GlcpN-(1 -> 3)-alpha-D-Manp-(1 -> 5)]-alpha-Kdop-(2 -> 6)-beta-D-GlcpN3N4P-(1 -> 6)-alpha-D-GlcpN3N1P), in addition to components lacking one of the terminal beta-D-GlcpN and/or the beta-D-Glcp residues (48 and 17%, respectively). These structures were identical to those of the R-LPS from B. melitensis EP, a strain simultaneously expressing both smooth and R-LPS, also studied herein. In contrast, disruption of man-B-core gives rise to a deep-rough pentasaccharide core (beta-D-Glcp-(1 -> 4)-alpha-Kdop-(2 -> 4)-alpha-Kdop-(2 -> 6)-beta-D-GlcpN3N4P-(1 -> 6)-alpha-D-GlcpN3N1P) as the major component (63%), as well as a minor tetrasaccharide component lacking the terminal beta-D-Glcp residue (37%). These results are in agreement with the predicted functions of the WbkD (glycosyltransferase involved in the biosynthesis of the O-antigen) and ManB(core) proteins (phosphomannomutase involved in the biosynthesis of a mannosyl precursor needed for the biosynthesis of the core and O-antigen). We also report that deletion of B. melitensis wadC removes the core oligosaccharide branch not linked to the O-antigen causing an increase in overall negative charge of the remaining LPS inner section. This is in agreement with the mannosyltransferase role predicted for WadC and the lack of GlcpN residues in the defective core oligosaccharide. Despite carrying the O-antigen essential in B. melitensis virulence, the core deficiency in the wadC mutant structure resulted in a more efficient detection by innate immunity and attenuation, proving the role of the beta-D-GlcpN-(1 -> 6)-beta-D-GlcpN-(1 -> 4)[beta-D-GlcpN-(1 -> 6)]-beta-D-GlcpN-(1 -> 3)-alpha-D-Manp-(1 -> 5) structure in virulence.

  • 255.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Holst, Otto
    Moriyón, Ignacio
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural studies of the rough lipopolysaccharides of Brucella melitensis mutants affected in the biosynthesis of the core and O-antigen polysaccharideManuskript (preprint) (Annet vitenskapelig)
  • 256.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Kovacs, Helena
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    NMR structure analysis of uniformly 13C-labeled carbohydrates2014Inngår i: Journal of Biomolecular NMR, ISSN 0925-2738, E-ISSN 1573-5001, Vol. 59, nr 2, s. 95-110Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, a set of nuclear magnetic resonance experiments, some of them commonly used in the study of C-13-labeled proteins and/or nucleic acids, is applied for the structure determination of uniformly C-13-enriched carbohydrates. Two model substances were employed: one compound of low molecular weight [(UL-C-13)-sucrose, 342 Da] and one compound of medium molecular weight (C-13-enriched O-antigenic polysaccharide isolated from Escherichia coli O142, similar to 10 kDa). The first step in this approach involves the assignment of the carbon resonances in each monosaccharide spin system using the anomeric carbon signal as the starting point. The C-13 resonances are traced using C-13-C-13 correlations from homonuclear experiments, such as (H)CC-CT-COSY, (H)CC-NOESY, CC-CT-TOCSY and/or virtually decoupled (H)CC-TOCSY. Based on the assignment of the C-13 resonances, the H-1 chemical shifts are derived in a straightforward manner using one-bond H-1-C-13 correlations from heteronuclear experiments (HC-CT-HSQC). In order to avoid the (1) J (CC) splitting of the C-13 resonances and to improve the resolution, either constant-time (CT) in the indirect dimension or virtual decoupling in the direct dimension were used. The monosaccharide sequence and linkage positions in oligosaccharides were determined using either C-13 or H-1 detected experiments, namely CC-CT-COSY, band-selective (H)CC-TOCSY, HC-CT-HSQC-NOESY or long-range HC-CT-HSQC. However, due to the short T-2 relaxation time associated with larger polysaccharides, the sequential information in the O-antigen polysaccharide from E. coli O142 could only be elucidated using the H-1-detected experiments. Exchanging protons of hydroxyl groups and N-acetyl amides in the C-13-enriched polysaccharide were assigned by using HC-H2BC spectra. The assignment of the N-acetyl groups with N-15 at natural abundance was completed by using HN-SOFAST-HMQC, HNCA, HNCO and C-13-detected (H)CACO spectra.

  • 257.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Li, Shengyu
    Yang, Zhennai
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural studies of the exopolysaccharide from Lactobacillus plantarum C88 using NMR spectroscopy and the program CASPER2015Inngår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 402, s. 87-94Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Some lactic acid bacteria, such as those of the Lactobacillus genus, have the ability to produce exopolysaccharides (EPSs) that confer favorable physicochemical properties to food and/or beneficial physiological effects on human health. In particular, the EPS of Lactobacillus plantarum C88 has recently demonstrated in vitro antioxidant activity and, herein, its structure has been investigated using NMR spectroscopy and the computer program CASPER (Computer Assisted Spectrum Evaluation of Regular polysaccharides). The pentasaccharide repeating unit of the O-deacetylated EPS consists of a trisaccharide backbone, -> 4)-alpha-DGalp-(1 -> 2)-alpha-D-Glcp-(1 -> 3)-beta-D-Glcp-(1 ->, with terminal D-Glc and D-Gal residues (1.0 and 0.8 equiv per repeating unit, respectively) extending from O3 and O6, respectively, of the -> 4)-alpha-D-Galp-(1 -> residue. In the native EPS an O-acetyl group is present, 0.85 equiv per repeating unit, at O2 of the alpha-linked galactose residue; thus the repeating unit of the EPS has the following structure: -> 4)[beta-D-Glcp-(1 -> 3)][beta-D-Galp-(1 -> 6)]alpha-D-Galp2Ac-(1 -> 2)-alpha-D-Glcp-(1 -> 3)-beta-D-Glcp-(1 ->. These structural features, and the chain length (similar to 10(3) repeating units on average, determined in a previous study), are expected to play an important role in defining the physicochemical properties of the polymer.

  • 258.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Lundborg, Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Weintraub, Andrej
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Rapid structural elucidation of polysaccharides employing predicted functions of glycosyltransferases and NMR data: Application to the O-antigen of Escherichia coli O592014Inngår i: Glycobiology, ISSN 0959-6658, E-ISSN 1460-2423, Vol. 24, nr 5, s. 450-457Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A computerized method that uses predicted functions of glycosyltransferases (GTs) in conjunction with unassigned NMR data has been developed for the structural elucidation of bacterial polysaccharides (PSs). In this approach, information about the action of GTs (consisting of possible sugar residues used as donors and/or acceptors, as well as the anomeric configuration and/or substitution position in the respective glycosidic linkages) is extracted from the Escherichia coli O-antigen database and is submitted, together with the unassigned NMR data, to the CASPER program. This time saving methodology, which alleviates the need for chemical analysis, was successfully implemented in the structural elucidation of the O-antigen PS of E. coli O59. The repeating unit of the O-specific chain was determined using the O-deacylated PS and has a branched structure, namely, -> 6)[alpha-d-GalpA3Ac/4Ac-(1 -> 3)]-alpha-d-Manp-(1 -> 3)-alpha-d-Manp-(1 -> 3)-beta-d-Manp-(1 -> 3)-alpha-d-GlcpNAc-(1 ->. The identification of the O-acetylation positions was efficiently performed by comparison of the H-1,C-13 HSQC NMR spectra of the O-deacylated lipopolysaccharide and the lipid-free PS in conjunction with chemical shift predictions made by the CASPER program. The side-chain d-GalpA residue carries one equivalent of O-acetyl groups at the O-3 and O-4 positions distributed in the LPS in a 3:7 ratio, respectively. The presence of O-acetyl groups in the repeating unit of the E. coli O59 PS is consistent with the previously proposed acetyltransferase WclD in the O-antigen gene cluster.

  • 259.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Lundborg, Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Weintraub, Andrej
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural studies and biosynthetic aspects of the o antigen polysaccharide from Escherichia coli o1742012Inngår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 354, s. 102-105Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure of the repeating unit of the O-antigenic polysaccharide (PS) from Escherichia coli O174 has been determined. Component analysis together with H-1 and C-13 NMR spectroscopy experiments were employed to elucidate the structure. Inter-residue correlations were determined by H-1, C-13-heteronuclear multiple-bond correlation and H-1, H-1-NOESY experiments. The PS is composed of tetrasaccharide repeating units with the following structure: -> 4)-beta-D-GlcpA-(1 -> 3)-beta-D-Galp-(1 -> 3)-beta-D-GalpNAc-(1 -> vertical bar beta-D-GlcpNAc-(1 -> 2) Cross-peaks of low intensity were present in the NMR spectra consistent with a beta-D-GlcpNAc-(1 -> 2)-beta-D-GlcpA(1 -> structural element at the terminal part of the polysaccharide, which on average is composed of similar to 15 repeating units. Consequently the biological repeating unit has a 3-substituted N-acetyl-D-galactosamine residue at its reducing end.

  • 260.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Ramström, Kristoffer
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Weintraub, Andrej
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural studies of the O-antigen polysaccharide from Escherichia coli O115 and biosynthetic aspects thereof2013Inngår i: Glycobiology, ISSN 0959-6658, E-ISSN 1460-2423, Vol. 23, nr 3, s. 354-362Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure of the O-antigen polysaccharide (PS) of Escherichia coliO115 has been investigated using a combination of component analysis and 1D and 2D nuclear magnetic resonance (NMR) spectroscopy experiments. The repeating unit of the O-antigen was elucidated using the O-deacetylated PS and has the following branched pentasaccharide structure: →3)[β-L-Rhap-(1 → 4)]-β-D-GlcpNAc-(1 → 4)-α-D-GalpA-(1 → 3)-α-D-Manp-(1 → 3)-β-D-GlcpNAc-(1→. Cross-peaks of low intensity, corresponding to a β-L-Rhap-(1 → 4)-β-D-GlcpNAc-(1→ structural element, were present in the NMR spectra and attributed to the terminal part of the PS; this information defines the biological repeating unit of the O-antigen by having a 3-substituted N-acetyl-D-glucosamine (GlcNAc) residue at its reducing end. Analysis of the NMR spectra of the native PS revealed O-acetyl groups distributed over different positions of theL-Rhap residue (∼0.70 per repeating unit) as well as at O-2 and O-3 of the D-GalpA residue (∼0.03 and ∼0.25 per repeating unit, respectively), which is in agreement with the presence of two acetyltransferases previously identified in the O-antigen gene cluster (Wang Q, Ruan X, Wei D, Hu Z, Wu L, Yu T, Feng L, Wang L. 2010. Mol Cell Probes. 24:286–290.). In addition, the four glycosyltransferases initially identified in the O-antigen gene cluster of E. coli O115 were analyzed using BLAST, and the function of two of them predicted on the basis of similarities with glycosyltransferases from Shigella dysenteriae type 5 and 12, as well as E. coli O58 and O152.

  • 261.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Weintraub, Andrej
    Karolinska Institute.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Facile Structural Elucidation of Glycans Using NMR Spectroscopy Data and the Program CASPER: Application to the O-Antigen Polysaccharide of Escherichia coli O1552013Inngår i: ChemPlusChem, ISSN 2192-6506, Vol. 78, nr 11, s. 1327-1329Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The program CASPER was successfully employed to rapidly elucidate a new O-antigen polysaccharide structure (obtained from a strain of Escherichia coli serogroup O155), using solelyunassigned NMR spectroscopy data as input information. Thus, what is considered the most tedious and time-consuming part of the structural elucidation process has been reduced from several hours (or even days) of manual interpretation to about four minutes of automated analysis.

  • 262.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Weintraub, Andrej
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural studies and biosynthetic aspects of the O-antigen polysaccharide from Escherichia coli O422015Inngår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 403, s. 174-181Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure of the O-antigen polysaccharide (PS) from Escherichia coli O42 has been investigated by NMR spectroscopy as the main method, which was complemented with sugar analysis, mass spectrometry, and analysis of biosynthetic information. The O-specific chain of the O-deacylated lipopolysaccharide (LPS-OH) consists of branched tetrasaccharide-glycerol repeating units joined by phosphodiester linkages. The lipid-free polysaccharide contains 0.8 equiv of O-acetyl groups per repeating unit and has the following teichoic acid-like structure: Based on biosynthetic aspects, this should also be the biological repeating unit. This O-antigen structure is remarkably similar to that of E. coli O28ac, differing only in the presence or absence, respectively, of a glucose residue at the branching point. The structural similarity explains the serological cross-reactivity observed between strains of these two serogroups, and also their almost identical O-antigen gene cluster sequences. -> 2)-(R)-Gro-(1-P-4)-beta-D-GlcpNAc-(1 -> 3)-beta-D-Galf2Ac-(1 -> 3)-alpha-D-GlcpNAc-(1 -> vertical bar a-D-Glcp-(1 -> 3)

  • 263.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Zaccheus, Mona V.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Weintraub, Andrej
    Ansaruzzaman, Mohammad
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural studies of a polysaccharide from Vibrio parahaemolyticus strain AN-160002016Inngår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 432, s. 41-49Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure of a polysaccharide from Vibrio parahaemolyticus strain AN-16000 has been investigated. The sugar and absolute configuration analysis revealed D-Glc, D-GalN, D-QuiN and L-FucN as major components. The PS was subjected to dephosphorylation with aqueous 40% HF to obtain an oligosaccharide that was analyzed by H-1 and C-13 NMR spectroscopy. The HR-MS spectrum of the oligosaccharide revealed a pentasaccharide composed of two Glc residues, one QuiNAc and one GalNAc, one FucNAc, as well as a glycerol moiety. The structure of the PS was determined using H-1, C-13, N-15 and P-31 NMR spectroscopy; inter-residue correlations were identified by H-1, C-13-heteronuclear multiple-bond correlation, H-1, H-1-NOESY and H-1, P-31-hetero-TOCSY experiments. The PS backbone has the following teichoic acid-like structure: -> 3)-D-Gro-(1-P-6)-beta-D-Glcp-(1 -> 4)-alpha-L-FucpNAc-(1 -> 3)-beta-D-QuipNAc-(1 -> with a side-chain consisting of alpha-D-Glcp-(1 -> 6)-alpha-D-GalpNAc-(1 -> linked to the O3 position of the FucNAc residue.

  • 264. Foster, R. A.
    et al.
    Carlin, N. I. A.
    Majcher, M.
    Tabor, H.
    Ng, L.-K.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural elucidation of the O-antigen of the Shigella flexneri provisionalserotype 88-893: structural and serological similarities with S. flexneri provisional serotype Y394 (1c)2011Inngår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 346, nr 6, s. 872-876Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure of the repeating unit of the O-antigen polysaccharide from Shigella flexneri provisional serotype 88-893 has been determined. 1H and 13C NMR spectroscopy as well as 2D NMR experiments were employed to elucidate the structure. The carbohydrate part of the hexasaccharide repeating unit is identical to the previously elucidated structure of the O-polysaccharide from S. flexneri prov. serotype Y394. The O-antigen of S. flexneri prov. serotype 88-893 carries 0.7 mol O-acetyl group per repeating unit located at O-2 of the 3-substituted rhamnosyl residue, as identified by H2BC and BS-CT-HMBC NMR experiments. The O-antigen polysaccharide is composed of hexasaccharide repeating units with the following structure: →2)-α-l-Rhap-(1→2)-α-l-Rhap-(1→3)-α-l-Rhap2Ac-(1→3)[α-d-Glcp-(1→2)-α-d-Glcp-(1→4)]-β-d-GlcpNAc-(1→. Serological studies showed that type antigens for the two provisional serotypes are identical; in addition 88-893 expresses S. flexneri group factor 6 antigen. We propose that provisional serotypes Y394 and 88-893 be designated as two new serotypes 7a and 7b, respectively, in the S. flexneri typing scheme.

  • 265. Fourniere, Viviane
    et al.
    Skantz, Linnea
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Sajtos, Ferenc
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Oscarson, Stefan
    Lahmann, Martina
    Synthesis of the Lewis b pentasaccharide and a HSA-conjugate thereof2010Inngår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 66, nr 39, s. 7850-7855Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Helicobacter pylori, a gastric pathogen, binds to various blood group antigens, including the Lewis types, present in the gastric tissue and a relation between the presentation of the ligands and the overall strength of binding has been assumed. Synthetic Lewis b tetra- and hexasaccharide conjugates are available but not the analogous pentasaccharide. An efficient synthesis of the amino spacer equipped Lewis b pentasaccharide, 3-aminopropyl alpha-L-fucopyranosyl-(1 -> 2)-beta-D-galactopyranosyl-(1 3)-[alpha-L-fucopyranosyl-(1 -> 4)]-2-acetamido-2-deoxy-beta-D-glucopyranosyl-(1 -> 3)-beta-D-galactopyranoside, is presented to enable further investigation of the carbohydrate recognition process of H. pylori.

  • 266.
    Fournière, Viviane
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Cumpstey, Ian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Synthesis of non-glycosidically linked selenoether pseudodisaccharides2010Inngår i: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 51, nr 16, s. 2127-2129Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Non-glycosidically linked disaccharide mimetics with a selenoether functionality linking the two monosaccharide residues have been synthesised. Protected Glc(Se3–3)Glc, Glc(Se3–6)Glc and Glc(Se3–6)Man structures were obtained. Selenium was introduced by displacement of carbohydrate sulfonates with a selenobenzoate anion. Conversion into diselenides by methanolysis of the benzoate and aerial oxidation was followed by reduction of the diselenides to selenolates, and in situ displacement of a second carbohydrate sulfonate in an SN2 reaction to give selenoethers. Glc(Se3–3)Glc and Glc(Se3–6)Glc were also obtained in deprotected form.

  • 267.
    Fransson, Ann-Britt L.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Deracemization of Functionalized Alcohols via Combined Ruthenium and Enzyme Catalysis2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The major part of this thesis describes the synthesis of enantiopure alcohols and diols by combining ruthenium-catalyzed racemization or epimerization and lipase-catalyzed asymmetric transformations. A minor part of this thesis is focused on ruthenium-catalyzed redox reactions for transfer hydrogenation of 1,3-cycloalkanediketones.

    Kinetic resolution of racemic γ-hydroxy acid derivatives was performed via Pseudomonas cepacia lipase (PS-C)-catalyzed transesterification. γ-Hydroxy esters and γ-hydroxy amides were studied showing in higher selec-tivity and yields for the γ-hydroxy amides. The enzyme PS-C tolerates both variation in the chain length and different functionalities giving good to high enantioselectivity. Combining enzymatic kinetic resolution with a ruthenium-catalyzed racemization led to a dynamic kinetic resolution (DKR). The use of 2,4-dimethyl-3-pentanol as a hydrogen source to suppress ketone formation in the dynamic kinetic resolution increased the yields of the acetate product. The synthetic utility of this procedure was illustrated by the practical synthesis of the γ-lactone (R)-5-methyltetrahydrofuran-2-one.

    A distereoselective transformation of cis/trans-1,3-cyclohexandiol using Candida antarctica lipase B (CALB)-catalyzed transesterification was of interest. Desymmetrization of cis-1,3-cyclohexanediol to the (R-monoacetate was successfully accomplished. Enantiopure (R,R)-diacetate was obtained from the (R)-monoacetate in a DYKAT process at room tem-perature. Metal- and enzyme-catalyzed transformation of cis/trans-1,3-cyclohexanediol using PS-C, gives a high diastereoselectivity for cis-diacetate. The (S)-mono-acetate was obtained from cis-diacetate by CALB-catalyzed hydrolysis. In addition, it was shown, by the use of deuterium-labeling that intramolecular acyl migration does not occur in the transformation of cis-monoacetate to the cis-diacetate.

    Ruthenium-catalyzed transfer hydrogenation of 1,3-cyclohexanedione under microwave heating was developed as an efficient and fast method for the preparation of 1,3-cycloalkandiols.

  • 268.
    Fransson, Ann-Britt L.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Borén, Linnéa
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Pàmies, Oscar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Kinetic Resolution and Chemoenzymatic Dynamic Kinetic Resolution of Functionalized γ-Hydroxy Amides2005Inngår i: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 70, nr 7, s. 2582-2587Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An efficient kinetic resolution of racemic gamma-hydroxy amides 1 was performed via Pseudomas cepacia lipase (PS-C)-catalyzed transesterification. The enzyme PS-C tolerates both variation in the chain length and different functionalities giving good to high enantioselectivity (E values of up to > 250). The combination of enzymatic kinetic resolution with a ruthenium-catalyzed racemization led to a dynamic kinetic resolution. The use of 2,4-dimethyl-3-pentanol as a hydrogen source to suppress ketone formation in the dynamic kinetic resolution yields the corresponding acetates in good yield and good to high enantioselectivity (ee's up to 98%). The synthetic utility of this procedure was illustrated by the practical synthesis of the versatile intermediate gamma-lactone (R)-5-methyltetrahydrofuran-2-one.

  • 269.
    Fransson, Ann-Britt L.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Xu, Yongmei
    Leijondahl, Karin
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Enzymatic Resolution, Desymmetrization and Dynamic Kinetic Asym-metric Transformation of 1,3-Cycloalkanediols2006Inngår i: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 71, nr 17, s. 6309-6316Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An efficient desymmetrization of cis-1,3-cyclohexanediol to (1S,3R)-3-(acetoxy)-1-cyclohexanol ((R,S)-2a) was performed via Candida antarctica lipase B (CALB)-catalyzed transesterification, in high yield (up to 93%) and excellent enantioselectivity (ee's up to >99.5%). (R,R)-Diacetate ((R,R)-3a) was obtained in a DYKAT process at room temperature from (1S,3R)-3-acetoxy-1-cyclohexanol ((R,S)-2a), in a high trans/cis ratio (91:9) and in excellent enantioselectivity of >99%. Metal- and enzyme-catalyzed dynamic transformation of cis/trans-1,3-cyclohexanediol using PS-C gave a high diastereoselectivity for cis-diacetate (cis/trans = 97:3). The (1R,3S)-3-acetoxy-1-cyclohexanol (ent-(R,S)-2a) was obtained from cis-diacetate by CALB-catalyzed hydrolysis in an excellent yield (97%) and selectivity (>99% ee). By deuterium labeling it was shown that intramolecular acyl migration does not occur in the transformation of cis-monoacetate to the cis-diacetate.

  • 270.
    Franzén, Johan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Palladium-Catalyzed Carbocyclizations of Allenes with Unsaturated Hydrocarbons2004Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Palladium-catalyzed reactions of unsaturated hydrocarbons are important processes in organic chemistry especially for the generation of ring systems. This thesis describes the development and mechanistic studies of carbocyclization reactions of allenes with olefins, allyls or 1,3-dienes catalyzed by palladium(0)- and palladium(II)-complexes. These reactions generally exhibit high stereo- and regioselectivity and give rise to stereodefined [n,3,0] bicyclic systems (n=3,4,5,6) in good to excellent yields. The mechanisms for these reactions were investigated with special attention directed to the intramolecular reaction of (π-allyl)palladium(II)-complexes and (π-1,3-diene)palladium(II)-complexes with allenes. It was demonstrated that the carbon-carbon bond formation occurred by nucleophilic attack of the middle carbon atom of the allene on the face of the allyl or 1,3-diene opposite to that of the palladium atom. Further, two new types of oxidative palladium(II)-catalyzed reactions between allenes and olefins or 1,3-dienes have been developed. These cyclizations constitute a new type of carbon-carbon bond forming reaction and there are support for a palladium(II)-catalyzed C-H activation at the allenic moiety rendering a vinylidienepalladium-intermediate followed by carbon-carbon bond formation via insertion of the olefin or 1,3-diene.

  • 271. François, Camille
    et al.
    Pourchet, Sylvie
    Boni, Gilles
    Rautiainen, Sari
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Samec, Joseph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Fournier, Lucie
    Robert, Carine
    Thomas, Christophe M.
    Fontaine, Stephane
    Gaillard, Yves
    Placet, Vincent
    Plasseraud, Laurent
    Design and synthesis of biobased epoxy thermosets from biorenewable resources2017Inngår i: Comptes rendus. Chimie, ISSN 1631-0748, E-ISSN 1878-1543, Vol. 20, nr 11-12, s. 1006-1016Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Biobased diepoxy synthons derived from isoeugenol, eugenol or resorcinol (DGE-isoEu, DGE-Eu and DGER, respectively) have been used as epoxy monomers in replacement of the diglycidyl ether of bisphenol A (DGEBA). Their curing with six different biobased anhydride hardeners leads to fully biobased epoxy thermosets. These materials exhibit interesting thermal and mechanical properties comparable to those obtained with conventional petrosourced DGEBA-based epoxy resins cured in similar conditions. In particular, a high T-g in the range of 90-130 degrees C and instantaneous moduli higher than 4.3 GPa have been recorded. These good performances are very encouraging, making these new fully biobased epoxy thermosets compatible with the usual structural application of epoxy materials.

  • 272.
    Friberg, Stig
    Stockholms universitet.
    Relationship between the structure of aluminium soaps and their colloid and surface chemistry1966Doktoravhandling, med artikler (Annet vitenskapelig)
  • 273.
    Frigell, Jens
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Synthesis of O-linked Carbasugar Analogues of Galactofuranosides and N-linked Neodisaccharides2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In this thesis, carbohydrate mimicry is investigated through the syntheses of carbohydrate analogues and evaluation of their inhibitory effects on carbohydrate-processing enzymes.

    Galactofuranosides are interesting structures because they are common motifs in pathogenic microorganisms but not found in mammals. M.tuberculosis, responsible for the disease tuberculosis, has a cell wall containing a repeating unit of alternating (1→5)- and (1→6)-linked β-D-galactofuranosyl residues. Synthetic inhibitors of the enzymes involved in the biosynthesis of the cell wall could find great therapeutic use.

    The first part of this thesis describes the first synthesis of the hydrolytically stable carbasugar analogue of galactofuranose, 4a-carba-β-D-Galf, and the synthetic work of synthesising β-linked pseudodisaccharides containing carba-Galf, which were tested for glycosyltransferease inhibitory activity. The pseudodisaccharide carba-Galf-(β1→5)-carba-Galf was found to be a moderate inhibitor of the glycosyltransferase GlfT2 of M.tuberculosis. The thesis also describes how a general method towards biologically relevant α-linked carba-Galf ethers was developed.

    The final part of this thesis is focussed on the formation of nitrogen-linked monosaccharides without the participation of the anomeric centre. Such a mode of coupling is called tail-to-tail neodisaccharide formation. The couplings of carbohydrate derivatives via the Mitsunobu reaction are successfully reported herein. The method describes the key introduction of an allylic alcohol in the electrophile and the subsequent functionalisation of the alkene to obtain the neodisaccharide. Two synthesised neodisaccharides presented in this thesis have been sent to be tested for glycosidase inhibitory activity.

  • 274.
    Frigell, Jens
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Cumpstey, Ian
    Carbasugar analogues of galactofuranose: α-O-linked derivativesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Using an indirect method, we have synthesised α-linked carbasugar analogues of galactofuranosides for the first time. Opening of a β-talo configured carbasugar 1,2-epoxide by alcohol nucleophiles under Lewis acidic conditions proceeded with very good regioselectivity to give α-talo configured C-1-substituted ethers with OH-2 free. Inversion of configuration at OH-2 by an oxidation–reduction sequence gave the α-galacto configured carbahexofuranose C-1 ethers. A carbadisaccharide corresponding to the Galf(α1→3)Manp substructure from Apodus deciduus galactomannan was synthesised to exemplify the method.

  • 275.
    Frigell, Jens
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Cumpstey, Ian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Carbasugar analogues of galactofuranosides: alpha-O-linked derivatives2010Inngår i: BEILSTEIN J ORG CHEM, ISSN 1860-5397, Vol. 6, s. 1127-1131Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using an indirect method, we have synthesised alpha-linked carbasugar analogues of galactofuranosides for the first time. Ring opening of a beta-talo configured carbasugar 1,2-epoxide by alcohol nucleophiles under Lewis acidic conditions proceeded with very good regioselectivity to give alpha-talo configured C1-substituted ethers with a free OH-group at the C2 position. Inversion of configuration at C2 by an oxidation-reduction sequence gave the alpha-galacto configured carbahexofuranose C1 ethers. A carbadisaccharide corresponding to the Galf(alpha 1 -> 3)Manp substructure from Apodus deciduus galactomannan was synthesised to exemplify the method.

  • 276.
    Frigell, Jens
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Cumpstey, Ian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    First synthesis of 4a-carba-beta-D-galactofuranose2007Inngår i: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 48, nr 52, s. 9073-9076Artikkel i tidsskrift (Fagfellevurdert)
  • 277.
    Frigell, Jens
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Cumpstey, Ian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Synthesis of carbadisaccharide mimics of galactofuranosides2009Inngår i: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 50, nr 36, s. 5142-5144Artikkel i tidsskrift (Fagfellevurdert)
  • 278.
    Frigell, Jens
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Eriksson, Lars
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Cumpstey, Ian
    Carbasugar analogues of galactofuranosides: β-O-linked derivativesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    A selectively protected carbasugar analogue of β-galactofuranose was synthesised from glucose using ring-closing metathesis as the key step. The carbasugar was converted into an α-galacto configured 1,2-epoxide, which was an effective electrophile in Lewis acid catalysed coupling reactions with alcohols. The epoxide was opened with regioselective attack at C-1 to give β-galacto configured C-1 ethers. Using carbohydrates as nucleophiles, we synthesised a number of pseudodisaccharides.

  • 279.
    Frigell, Jens
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Pearcey, J.A.
    Lowary, T.
    Cumpstey, Ian
    Carbasugar Analogues of Galactofuranose: Pseudodisaccharide Mimics of Fragments of Mycobacterial ArabinogalactanManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    A partially protected carbasugar analogue of β-galactofuranose was converted into an α-galacto configured 1,2-epoxide, which was was opened by alcohols under Lewis acid catalysis with regioselective attack at C-1 to give β-galacto configured C-1 ethers. Using OH-5 and OH-6 carbagalactofuranose derivatives as nucleophiles, we synthesised pseudodisaccharide analogues of substructures of the arabinogalactan from M. tuberculosis. The dicarba analogue of the disaccharide Galf(β1→5)Galf was found to moderately inhibit the action of GlfT2 galactofuranosyl transferase from M. tuberculosis.

  • 280.
    Frigell, Jens
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Pearcey, Jean A.
    Lowary, Todd L.
    Cumpstey, Ian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Carbasugar Analogues of Galactofuranosides: Pseudodisaccharide Mimics of Fragments of Mycobacterial Arabinogalactan2011Inngår i: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, nr 7, s. 1367-1375Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A partially protected carbasugar analogue of beta-galactofuranose was converted into an alpha-galacto-configured 1,2-epoxide, which was opened by alcohols under Lewis acid catalysis with regioselective attack at C-1 to give beta-galacto-configured C-1 ethers. Using OH-5 and OH-6 carbagalactofuranose derivatives as nucleophiles, we synthesised pseudodisaccharide analogues of substructures of the arabinogalactan from M. tuberculosis. The dicarba analogue of the disaccharide Galf(beta 1 -> 5) Galf was found to moderately inhibit the action of GlfT2 galactofuranosyl transferase from M. tuberculosis.

  • 281.
    Gao, Weiming
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Sun, Junliang
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Li, Mingrun
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Åkermark, Torbjörn
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Romare, Kristina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Sun, Licheng
    Royal Institute of Technology (KTH), Department of Organic Chemistry.
    Åkermark, Björn
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Synthesis of a [3Fe2S] cluster with low redox potential from [2Fe2S] hydrogenase models: electrochemical and photochemical generation of hydrogen2011Inngår i: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, Vol. 2011, nr 7, s. 1100-1105Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the attempted replacement of carbon monoxide by the bis(phosphane) dppv in a dinuclear [2Fe2S] complex, a trinuclear [3Fe2S] complex with two bis(phosphane) ligands was unexpectedly obtained. On protonation, this gave a bridged hydride complex with an unusually low potential for the reduction of protons to molecular hydrogen. The redox potential also appears sufficiently positive for direct electron transfer from an excited [Ru(bpy)(3)](2+) sensitizer.

  • 282.
    Gao, Weiming
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Sun, Junliang
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, Avdelningen för strukturkemi.
    Åkermark, Torbjörn
    Li, Mingrun
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, Avdelningen för strukturkemi.
    Eriksson, Lars
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, Avdelningen för strukturkemi.
    Sun, Licheng
    Åkermark, Björn
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Attachment of a hydrogen-bonding carboxylate side chain to an [FeFe]-hydrogenase model complex: Influence on the catalytic mechanism2010Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 16, nr 8, s. 2537-2546Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Azapropanedithiolate (adt)-bridged model complexes of [FeFe]-hydrogenase bearing a carboxylic acid functionality have been designed with the aim of decreasing the potential for reduction of protons to hydrogen. Protonation of the bisphosphine complexes 46 has been studied by in situ IR and NMR spectroscopy, which revealed that protonation with triflic acid most likely takes place first at the N-bridge for complex 4 but at the FeFe bond for complexes 5 and 6. Using an excess of acid, the diprotonated species could also be observed, but none of the protonated species was sufficiently stable to be isolated in a pure state. Electrochemical studies have provided an insight into the catalytic mechanisms under strongly acidic conditions, and have also shown that complexes 3 and 6 are electro-active in aqueous solution even in the absence of acid, presumably due to hydrogen bonding. Hydrogen evolution, driven by visible light, has been observed for three-component systems consisting of [Ru(bpy)3]2+, complex 1, 2, or 3, and ascorbic acid in CH3CN/D2O solution by on-line mass spectrometry.

  • 283.
    Gao, Yan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Åkermark, Torbjörn
    Liu, Jianhui
    Sun, Licheng
    Åkermark, Björn
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Nucleophilic attack of hydroxide on a MnV oxo complex: a model of the O-O bond formation in the oxygen evolving complex of photosystem II2009Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 131, nr 25, s. 8726-8727Artikkel i tidsskrift (Fagfellevurdert)
  • 284.
    Garegg, Per J.
    Stockholms universitet.
    Studies on some partially substituted glycosides and polysaccharides1965Doktoravhandling, med artikler (Annet vitenskapelig)
  • 285.
    Gemma, Emiliano
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Synthesis of Oligosaccharides for Interaction Studies with Various Lectins2005Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In this thesis, the syntheses of oligosaccharides for interaction studies with various lectins are described. The first section reports the syntheses of tetra, tri- and disaccharides corresponding to truncated versions of the glucosylated arm of Glc1Man9(GlcNAc)2, found in the biosynthesis of N-glycans. The thermodynamic parameters of their interaction with calreticulin, a lectin assisting and promoting the correct folding of newly synthesised glycoproteins, were established by isothermal titration calorimetry. In the second section, a new synthetic pathway leading to the same tetra- and trisaccharides is discussed. Adoption of a convergent strategy and of a different protecting group pattern resulted in significantly increased yields of the target structures. The third section describes the syntheses of a number of monodeoxy-trisaccharides related to the above trisaccharide Glc-α-(1→3)-Man-α-(1→2)-Man-α-OMe. Differentsynthetic approaches were explored and the choice of early introduction of the deoxy functionality proved the most beneficial. In the last section, the synthesis of spacer-linked LacNAc dimers as substrates for the lectins galectin-1 and -3 is presented. This synthesis was realized by glycosidation of a number diols with peracetylated LacNAc-oxazoline. Pyridinium triflate was tested as a new promoter, affording the target dimers in high yields. This promoter in combination with microwave irradiation gave even higher yields and also shortened the reaction times.

  • 286.
    Gemma, Emiliano
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Lahmann, Martina
    Oscarson, Stefan
    Synthesis of the tetrasaccharide α-D-Glcp-(1→3)-α-D-Manp-(1→2)-α-D-Manp-(1→2)-α-D-Manp recognised by Calreticulin/Calnexin2005Inngår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 340, nr 16, s. 2558-2562Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The title compound as its methyl glycoside was efficiently synthesized using a block synthesis approach. Halide-assisted glycosidations between 6-O-acetyl-2,3,4-tri-O-benzyl-α-d-glucopyranosyl iodide and ethyl 2-O-acetyl-4,6-di-O-benzyl-1-thio-α-d-mannopyranoside using triphenylphosphine oxide as promoter yielded, with complete α-selectivity, a disaccharide building block in high yield. The perbenzylated derivative of this proved to be an excellent donor affording 88% of the protected target tetrasaccharide in an NIS/AgOTf-promoted coupling to a known methyl dimannoside acceptor. Deprotection through catalytic hydrogenolysis then gave the target compound in 47% overall yield.

  • 287.
    Georgieva, Polina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Himo, Fahmi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Quantum chemical modeling of enzymatic reactions: The Case of histone lysine methyltransferase2010Inngår i: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987X, Vol. 31, nr 8, s. 1707-1714Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Quantum chemical cluster models of enzyme active sites are today an important and powerful tool in the study of various aspects of enzymatic reactivity. This methodology has been applied to a wide spectrum of reactions and many important mechanistic problems have been solved. Herein, we report a systematic study of the reaction mechanism of the histone lysine methyltransferase (HKMT) SET7/9 enzyme, which catalyzes the methylation of the N-terminal histone tail of the chromatin structure. In this study, HKMT SET7/9 serves as a representative case to examine the modeling approach for the important class of methyl transfer enzymes. Active site models of different sizes are used to evaluate the methodology. In particular, the dependence of the calculated energies on the model size, the influence of the dielectric medium, and the particular choice of the dielectric constant are discussed. In addition, we examine the validity of some technical aspects, such as geometry optimization in solvent or with a large basis set, and the use of different density functional methods.

  • 288. Georgieva, Polina
    et al.
    Wu, Qian
    McLeish, Michael J.
    Himo, Fahmi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    The reaction mechanism of phenylethanolamine N-methyltransferase: A density functional theory study2009Inngår i: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1794, nr 12, s. 1831-1837Artikkel i tidsskrift (Fagfellevurdert)
  • 289.
    Ghosh, Raju
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Lindstedt, Erik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Jalalian, Nazli
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Olofsson, Berit
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Room Temperature, Metal-Free Arylation of Aliphatic Alcohols2014Inngår i: ChemistryOpen, ISSN 2191-1363, Vol. 3, nr 2, s. 54-57Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Diaryliodonium salts are demonstrated as efficient arylating agents of aliphatic alcohols under metal-free conditions. The reaction proceeds at room temperature within 90min to give alkyl aryl ethers in good to excellent yields. Aryl groups with electron-withdrawing substituents are transferred most efficiently, and unsymmetric iodonium salts give chemoselective arylations. The methodology has been applied to the formal synthesis of butoxycaine.

  • 290.
    Ghosh, Raju
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Olofsson, Berit
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Metal-Free Synthesis of N-Aryloxyimides and Aryloxyamines2014Inngår i: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 16, nr 6, s. 1830-1832Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    N-Hydroxyphthalimide and N-hydroxysuccinimide have been arylated with diaryliodonium salts to provide N-aryloxyimides in excellent yields in short reaction times. A novel hydrolysis under mild and hydrazine-free conditions yielded aryloxyamines, which are valuable building blocks in the synthesis of oxime ethers and benzofurans.

  • 291.
    Ghosh, Raju
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Stridfeldt, Elin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Olofsson, Berit
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Metal-Free One-Pot Synthesis of Benzofurans2014Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, nr 29, s. 8888-8892Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ethyl acetohydroxamate was efficiently arylated with diaryliodonium salts at room temperature under transition-metal-free conditions. The obtained O-arylated products were reacted in situ with ketones under acidic conditions to yield substituted benzo[b]furans through oxime formation, [3,3]-rearrangement, and cyclization in a fast and operationally simple one-pot fashion without using excess reagents. Alternatively, the O-arylated products could be isolated or transformed in situ to aryloxyamines or O-arylaldoximes. The methodology was applied to the synthesis of Stemofuran A and the formal syntheses of Coumestan, Eupomatenoid 6, and (+)-machaeriol B.

  • 292.
    Gigant, Nicolas
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Access to Cinnamyl Derivatives from Arenes and Allyl Esters by a Biomimetic Aerobic Oxidative Dehydrogenative Coupling2014Inngår i: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 16, nr 6, s. 1664-1667Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An efficient biomimetic aerobic oxidative dehydrogenative alkenylation of arenes with allyl esters is presented. The reaction proceeds under an ambient pressure of oxygen with relatively low catalyst loading of palladium acetate, employing catalytic amounts of electron-transfer mediators (ETMs). This study represents a new environmentally friendly method for the synthesis of cinnamyl derivatives.

  • 293.
    Gigant, Nicolas
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Aerobic Direct C-H Arylation of Nonbiased Olefins2014Inngår i: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 16, nr 17, s. 4432-4435Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An efficient ligand-promoted biomimetic aerobic oxidative dehydrogenative cross-coupling between arenes and nonbiased olefins is presented. Acridine as a ligand was found to significantly enhance the rate, the yield, and the scope of the reaction under ambient oxygen pressure, providing a variety of alkenylarenes via an environmentally friendly procedure.

  • 294.
    Gigant, Nicolas
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Aerobic Double Dehydrogenative Cross Coupling between Cyclic Saturated Ketones and Simple Arenes2014Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, nr 20, s. 5890-5894Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The synthesis of 3-aryl-2-cyclohexenones is a topic of current interest as they are not only privileged structures in bioactive molecules, but they are also relevant feedstocks for the synthesis of substituted phenols or anilines, which are ubiquitous structural elements both in drug design and medicinal chemistry. A simple and sustainable one-pot aerobic double dehydrogenative reaction under mild conditions for the introduction of arenes in the -position of cyclic ketones has been developed. Starting from the corresponding saturated ketone, this reaction sequence proceeds under relatively low Pd catalyst loading and involves catalytic amounts of electron-transfer mediators (ETMs) under ambient oxygen pressure.

  • 295.
    Gigant, Nicolas
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi. Université Paris-Sud, France.
    Quintin, Francois
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Preparation of Tetrasubstituted Olefins Using Mono or Double Aerobic Direct C-H Functionalization Strategies: Importance of Steric Effects2015Inngår i: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 80, nr 5, s. 2796-2803Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel protocol for the synthesis of tetrasubstituted olefins through a biomimetic approach has been explored. Both mono- and diarylations were performed under ambient oxygen pressure, giving a range of highly hindered tetrasubstituted alkenes. For diarylation of disubstituted substrates, it was demonstrated that the second arylation is the rate-limiting step of the overall transformation.

  • 296. Girgis, Adel S.
    et al.
    Mabied, Ahmed F.
    Stawinski, Jacek
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Hegazy, Lamees
    George, Riham F.
    Farag, Hanaa
    Shalaby, ElSayed M.
    Farag, I. S. Ahmed
    Synthesis and DFT studies of an antitumor active spiro-oxindole2015Inngår i: New Journal of Chemistry, ISSN 1144-0546, E-ISSN 1369-9261, Vol. 39, nr 10, s. 8017-8027Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An anti-oncological active spiro-oxindole 7 was synthesized regioselectively via a [3+2]-cycloaddition reaction of azomethine ylide to exocyclic olefinic linkage of 4-piperidone 6, exhibiting properties against diverse tumor cell lines including leukemia, melanoma and cancers of the lung, colon, brain, ovary, breast, prostate, and kidney. Compound 7 crystallizes in the monoclinic system and P21/c space group with four molecules in the unit cell. The structure was also studied by AM1, PM3 and DFT techniques. DFT studies support the stereochemical selectivity of the reaction and determine the molecular electrostatic potential and frontier molecular orbitals.

  • 297. Godefroid, Marie
    et al.
    Svensson, Mona V
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Cambier, Pierre
    Uzureau, Sophie
    Mirabella, Aurélie
    De Bolle, Xavier
    Van Cutsem, Pierre
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Letesson, Jean-Jacques
    Brucella melitensis 16M produces a mannan and other extracellular matrix components typical of a biofilm2010Inngår i: FEMS Immunology and Medical Microbiology, ISSN 0928-8244, E-ISSN 1574-695X, Vol. 59, nr 3, s. 364-377Artikkel i tidsskrift (Fagfellevurdert)
  • 298.
    Goncalves, Sylvie
    et al.
    Universite de Strasbourg, Faculte de Pharmacie UMR/CNRS 7199, Laboratoire des Systemes Chimiques Fonctionnels, Illkirch, France.
    Santoro, Stefano
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Nicolas, Marc
    Les Laboratoires Pierre Fabre, Centre de Developpement Chimique et Industriel, Gaillac, France.
    Wagner, Alain
    Universite de Strasbourg, Faculte de Pharmacie UMR/CNRS 7199, Laboratoire des Systemes Chimiques Fonctionnels, Illkirch, France.
    Maillos, Philippe
    Les Laboratoires Pierre Fabre, Centre de Developpement Chimique et Industriel, Gaillac, France.
    Himo, Fahmi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Baati, Rachid
    Universite de Strasbourg, Faculte de Pharmacie UMR/CNRS 7199, Laboratoire des Systemes Chimiques Fonctionnels, Illkirch, France.
    Cationic cyclization of 2-alkenyl-1,3-dithiolanes: DiastereoselectiveSynthesis of trans-decalins2011Inngår i: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 76, nr 9, s. 3274-3285Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An unprecedented and highly diastereoselective 6-endo-trig cyclization of 2-alkenyl-1,3-dithiolanes has beendeveloped yielding trans-decalins, an important scaffold present in numerous di- and triterpenes. The novelty of this 6-endo-trigc yclization stands in the stepwise mechanism involving 2-alkenyl-1,3-dithiolane, acting as a novel latent initiator. It is suggested that the thioketal opens temporarily under the influence of TMSOTf, triggering the cationic 6-endo-trig cyclization, andcloses after C−C bond formation and diastereoselective protonation to terminate the process. DFT calculations confirm this mechanistic proposal and provide a rationale for the observed diastereoselectivity. The reaction tolerates a wide range of functionalities and nucleophilic partners within the substrate. We have also shown that the one-pot 6-endo-trig cyclization followedby in situ 1,3-dithiolane deprotection afford directly the corresponding ketone. This improvement allowed the achievement of the shortest total synthesis of triptophenolide and the shortest formal synthesis of triptolide.

  • 299.
    González Miera, Greco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Homogeneous and heterogeneous Cp*Ir(III) catalytic systems: Mechanistic studies of redox processes catalyzed by bifunctional iridium complexes, and synthesis of iridium-functionalized MOFs2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The purpose of this doctoral thesis is to investigate and develop catalytic processes mediated by iridium(III) complexes. By understanding the mechanisms, the weaknesses of the designed catalysts can be identified and be overcome in the following generation.

    The thesis is composed of two general sections dedicated to the synthesis and applications of homogeneous catalysts and to the preparation of heterogeneous catalysts based on metal-organic frameworks (MOFs). After a general introduction (Chapter 1), the first part of the thesis (Chapters 2-4, and Appendix 1) covers the use of several homogeneous bifunctional [Cp*Ir(III)] catalysts in a variety of chemical transformations, as well as mechanistic studies.

    Chapter 2 summarizes the studies on the N-alkylation of anilines with benzyl alcohols catalyzed by bifunctional Ir(III) complexes. Mechanistic investigations when the reactions were catalyzed by Ir(III) complexes with a hydroxy-functionalized N-heterocyclic carbene (NHC) ligand are discussed, followed by the design of a new generation of catalysts. The chapter finishes presenting the improved catalytic performance of these new complexes.   

    A family of these NHC-iridium complexes was evaluated in the acceptorless dehydrogenation of alcohols, as shown in Chapter 3. The beneficial effect of a co-solvent was investigated too. Under these base-free conditions, a wide scope of alcohols was efficiently dehydrogenated in excellent yields. The unexpected higher activity of the hydroxy-containing bifunctional NHC-Ir(III) catalysts, in comparison to that of the amino-functionalized one, was investigated experimentally.

    In the fourth chapter, the catalytic process presented in Chapter 3 was further explored on 1,4- and 1,5-diols, which were transformed into their corresponding tetrahydrofurans and dihydropyrans, respectively. Mechanistic investigations are also discussed.

    In the second part of the thesis (Chapter 5), a Cp*Ir(III) complex was immobilized into a MOF. The heterogenization of the metal complex was achieved efficiently, reaching high ratios of functionalization. However, a change in the topology of the MOF was observed. In this chapter, the use of advanced characterization techniques such as X-ray absorption spectroscopy (XAS) and pair distribution function (PDF) analyses enabled to study a phase transformation in these materials.

  • 300.
    González Miera, Greco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Nonclassical cyclodehydration of diols assisted by metal-ligand cooperation2017Artikkel i tidsskrift (Fagfellevurdert)
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