Digitala Vetenskapliga Arkivet

Change search
Refine search result
6789101112 401 - 450 of 4163
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 401.
    Bermejo-López, Aitor
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Direct N-alkylation of unprotected amino sugars by alcohols. Application to the synthesis of sugar-based surfactantsManuscript (preprint) (Other academic)
    Abstract [en]

    Herein, we report a direct N-alkylation of unprotected aminosugars with a wide variety of alcohols as alkylating agents. Excellent selectivity towards monoalkylation is achieved in most of the cases with the amino group present at different positions along the carbohydrate ring. Access to methylated products using methanol is also reported in this work. The applicability of the method is further demonstrated by the synthesis of a variety of carbohydrate-based surfactants.

  • 402.
    Bermejo-López, Aitor
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Selective and Quantitative Functionalization of Unprotected a-Amino Acids Using a Recyclable Homogeneous CatalystManuscript (preprint) (Other academic)
    Abstract [en]

    A new Ir(III)-NHC catalyst is reported that shows remarkable activity in the N-alkylation of unprotected amino acids. The catalytic system gives excellent selectivity towards monoalkylated a-amino acids, and a high degree of retention of stereochemistry. A wide range of unprotected nonnatural amino acids have been prepared. These compounds represent an array of building blocks that could be used for the direct synthesis of peptidomimetics. The synthesis of aminoacid-based surfactants is also reported. This catalytic method gives the amino acid products in quantitative yield, so tedious purifications by derivatization are therefore avoided. Furthermore, although the catalyst is a homogeneous metal complex, it can be recycled and reused for several runs. This also contributes to the efficiency and sustainability of the method.

  • 403. Bermejo-López, Aitor
    et al.
    Tortajada, Pedro J.
    Carrasco, Sergio
    Kopf, Kenji
    Sanz-Marco, Amparo
    Hvid, Mathias S.
    Martín-Matute, Belen
    Selective Synthesis of Imines via Photooxidative AmineCross-Condensation Catalyzed by PCN-222(Pd)Manuscript (preprint) (Other academic)
    Abstract [en]

    Palladium metallated PCN-222 enables the selective cross-condensation of anilines with benzylic aminesunder photooxidative conditions and at ambient temperature. The method affords a series of linear and cyclic Schiffbases. The mild conditions used in this catalytic system results in the isolation of resourceful intermediates such as 2-(benzylideneamino)aniline and 2-(benzylideneamino)phenols, which can be further modified.

  • 404.
    Bermejo-Velasco, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Polymer Chemistry.
    Insights into Covalent Chemistry for the Developmen­t of Biomaterials2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Covalent cross-linking chemistry is currently exploited in the preparation of biomaterial for biomedical applications. Choice of these chemistries for the preparation of biomaterials and bioconjugates strongly influences the biological output of these materials. Therefore, this thesis aims to develop novel bioconjugation strategies understanding their advantages and drawbacks. Our results provide new insight to adapt these chemical transformations for a specific application.

    The first part of this thesis points out the relevance of tuning different properties of biomaterials with specific emphasis on the development of hyaluronic acid (HA) hydrogels. The second part of the thesis describes how different chemical transformations including hydrazone formation (Paper I), thiazolidine formation (Paper II), cross-aldol addition reaction (Paper III) and disulfide formation (Paper IV) dictate material properties.

    This thesis explores both basic organic reaction mechanism and application of these reactions to influence material characteristics. The detailed study of the reaction conditions, kinetics, and stability of the products will help to understand the mechanical properties, hydrolytic stability, and degradability of the materials described here.

    Additionally, we performed degradation studies of gadolinium labeled HA hydrogels using magnetic resonance imaging. Furthermore, we also explored post-synthetic modification of hydrogels to link model fluorescent moieties as well as explored the tissue adhesive properties using Schiff-base formation.

    In summary, this thesis presents a selection of different covalent chemistries for the design of advanced biomaterials. The advantages and disadvantages of these chemistries are rigorously investigated. We believe, such an investigation provides a better understanding of the bioconjugation strategies for the preparation of biomaterials with potential clinical translation.

    Download full text (pdf)
    fulltext
    Download (jpg)
    presentationsbild
  • 405.
    Bermúdez, Eduardo
    et al.
    Universidad de la Republic, URY.
    Ventura, Oscar N
    Universidad de la Republic, URY.
    Saenz Mendez, Patricia
    Universidad de la Republic, URY.
    Mechanism of the organocatalyzed decarboxylative Knoevenagel-Doebner reaction. A theoretical study.2010In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 114, no 50, p. 13086-92Article in journal (Refereed)
    Abstract [en]

    We have investigated important intermediates and key transition states of the organocatalyzed Knoevenagel condensation using density functional theory and two different basis sets (6-31 G(d,p) and 6-311++G(2df,2pd)), both in gas phase and simulating the bulk solvent (pyridine) using the PCM method. Calculated structures for reactants, intermediates, and key transition states suggest that the secondary amine catalyst is essential, both for activating the aldehyde for nucleophilic attack, and in the possible decarboxylation pathways. The calculated results are shown to agree with available experimental information. On the basis of the results obtained, the studied mechanism may be important in the understanding of vinylphenol production during malting and brewing of wheat and barley grains.

  • 406. Bernardo-Garcia, Noelia
    et al.
    Sánchez-Murcia, Pedro A.
    Espaillat, Akbar
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Martínez-Caballero, Siseth
    Cava, Felipe
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Hermoso, Juan A.
    Gago, Federico
    Cold-induced aldimine bond cleavage by Tris in Bacillus subtilis alanine racemase2019In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 17, no 17, p. 4350-4358Article in journal (Refereed)
    Abstract [en]

    Pyridoxal 5'-phosphate (PLP) is a versatile cofactor involved in a large variety of enzymatic processes. Most of PLP-catalysed reactions, such as those of alanine racemases (AlaRs), present a common resting state in which the PLP is covalently bound to an active-site lysine to form an internal aldimine. The crystal structure of BsAlaR grown in the presence of Tris lacks this covalent linkage and the PLP cofactor appears deformylated. However, loss of activity in a Tris buffer only occurred after the solution was frozen prior to carrying out the enzymatic assay. This evidence strongly suggests that Tris can access the active site at subzero temperatures and behave as an alternate racemase substrate leading to mechanism-based enzyme inactivation, a hypothesis that is supported by additional X-ray structures and theoretical results from QM/ MM calculations. Taken together, our findings highlight a possibly underappreciated role for a common buffer component widely used in biochemical and biophysical experiments.

  • 407.
    Berner, Simon
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Biela, Sarah
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ledung, Greger
    Gogoll, Adolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry I.
    Bäckvall, Jan-E.
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Oscarsson, Sven
    Activity boost of a biomimetic oxidation catalyst by immobilization onto a gold surface2006In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 244, no 1, p. 86-91Article in journal (Refereed)
    Abstract [en]

    Thiol-functionalized cobalt porphyrins were used as a model system for investigating catalytic activity in homogeneous and heterogeneous oxidation catalysis. Self-assemble monolayers of thiol-functionalized cobalt porphyrins were prepared on a gold surface and served as heterogenous catalysts. These immoblilized molecules prevented the strong inactivation observed for their homogeneous congener. As a result, the turnover number per molecule in heterogeneous catalysis was at least 100 times higher than that of the corresponding homogeneous catalyst. It is atypical for a heterogenized catalyst to outperform its homogeneous congener. The properties of the molecular layers were characterized on the molecular level by means of X-ray photoelectorn spectroscopy (XPS) and scanning tunneling microscopy (STM). The results demonstrate that the performance of these biomimetic catalysts can be dramatically improved if the catalyst arangement can be controlled on the molecular level.

  • 408.
    Bernin, Diana
    et al.
    Swedish NMR Ctr, Gothenburg, Sweden..
    Bialik, Erik
    Lund Univ, Div Theoret Chem, Lund, Sweden..
    Stenqvist, Bjorn
    Lund Univ, Div Theoret Chem, Lund, Sweden..
    Fang, Yuan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Ostlund, Asa
    SP Tech Res Inst Sweden, Stockholm, Sweden..
    Furo, Istvan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Lindman, Bjorn
    Lund Univ, Chem, Lund, Sweden..
    Lund, Mikael
    Lund Univ, Div Theoret Chem, Lund, Sweden..
    On the ionization of cellulose in aqueous alkali2017In: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 253Article in journal (Other academic)
  • 409.
    Bernlind, Christian
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of LPS epitopes containing Kdo, L-, and D-Glycero-D-manno-heptose to be used in potential conjugate vaccines against Haemophilus species1998Doctoral thesis, comprehensive summary (Other academic)
  • 410.
    Berthold, Malin
    Stockholm University, Faculty of Science, Department of Neurochemistry and Neurotoxicology.
    Galanin: ligand - receptor interactions1997Doctoral thesis, comprehensive summary (Other academic)
  • 411.
    Bertilsson, Sophie
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I.
    Andersson, Pher
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I.
    Asymmetric base-promoted epoxide rearrangement: achiral lithium amides revisited2002In: Tetrahedron, no 58, p. 4665-4668Article in journal (Refereed)
  • 412.
    Bertilsson, Sophie
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I.
    Södergren, Mikael
    Andersson, Pher
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I.
    New Catalysts for the Base-Promoted Isomerization of Epoxides to Allylic Alcohols. Broadened Scope and Near-Perfect Asymmetric Induction2002In: J. Org. Chem., no 67, p. 1567-1573Article in journal (Refereed)
  • 413.
    Bertilsson, Sophie
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I.
    Tedenborg, Lars
    Alonso, Diego
    Andersson, Pher
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I.
    Chiral N, N' - and N,O-Bidentate Anionic Ligands. Preparation, Metal Complexation, and Evalution in the Asymmetric Aziridination of Olefins1999In: Organometallics, no 18, p. 1281-1286Article in journal (Refereed)
  • 414.
    Besev M, Engman L,
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Diastereocontrol by Hydroxyl Auxiliary in the Synthesis of Pyrrolidines via Radical Cyclization2002In: Org. Lett., no 4, p. 3023-Article in journal (Other scientific)
  • 415.
    Beshara, Soheir
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Chemistry.
    Sörensen, Jens
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Radiology, Oncology and Radiation Science, Section of Nuclear Medicine and PET. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
    Lubberink, Mark
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Radiology, Oncology and Radiation Science, Section of Nuclear Medicine and PET.
    Tolmachev, Vladimir
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Radiology, Oncology and Radiation Science, Biomedical Radiation Sciences.
    Långström, Bengt
    PET Centre, University Hospital, Uppsala, Sweden.
    Antoni, Gunnar
    PET Centre, University Hospital, Uppsala, Sweden.
    Danielsson, Bo G.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Internal Medicine.
    Lundqvist, Hans
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Radiology, Oncology and Radiation Science, Biomedical Radiation Sciences.
    Pharmacokinetics and red cell utilization of 52Fe/59Fe-labelled iron polymaltose in anaemic patients using positron emission tomography2003In: British Journal of Haematology, ISSN 0007-1048, E-ISSN 1365-2141, Vol. 120, no 5, p. 853-859Article in journal (Other academic)
    Abstract [en]

    Parenteral iron-polysaccharide complexes are increasingly applied. The pharmacokinetics of iron sucrose have been assessed by our group using positron emission tomography (PET). A single intravenous injection of 100 mg iron as iron (III) hydroxide-polymaltose complex, labelled with a tracer in the form of 52Fe/59Fe, was similarly assessed in six patients using PET for about 8 h. Red cell utilization was followed for 4 weeks. Iron polymaltose was similarly distributed to the liver, spleen and bone marrow. However, a larger proportion of this complex was rapidly distributed to the bone marrow. The shorter equilibration phase for the liver, about 25 min, indicates the minimal role of the liver for direct distribution. Splenic uptake also reflected the reticuloendothelial handling of this complex. Red cell utilization ranged from 61% to 99%. Despite the relatively higher uptake by the bone marrow, there was no saturation of marrow transport systems at this dose level. In conclusion, high red cell utilization of iron polymaltose occurred in anaemic patients. The major portion of the injected dose was rapidly distributed to the bone marrow. In addition, the reticuloendothelial uptake of this complex may reflect the safety of polysaccharide complexes. Non-saturation of transport systems to the bone marrow indicated the presence of a large interstitial transport pool, which might possibly be transferrin.

  • 416.
    Beşev, Magnus
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Organic Chemistry.
    Radical Cyclization Approaches to Pyrrolidines2002Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Five-membered rings are readily prepared by 5-exo-trig radical cyclization. This thesis is concerned with novel methodology for pyrrolidine synthesis. We have synthesised selenium containing radical precursors from aziridines and α-phenylseleno ketones, and cyclized them to 2,4- and 3,4-disubstituted pyrrolidines. A few examples of 5-exo-dig cyclization were also demonstrated. In another study we investigated the capacity of the nitrogen protecting group to direct diastereoselectivity in the formation of 2,4-disubstituted pyrrolidines. The diphenylphosphinoyl protecting group directed cyclization to occur in a highly cis-selective manner. When cyclizations were performed at 17 oC, cis/trans-ratios as high as 24/1 were obtained. In contrast, cyclization of the unprotected pyrrolidine precursor afforded the trans-diastereomer as the major product (cis/trans = 1/3.3 – 1/20). We also examined the use of a hydroxyl auxiliary for controlling diastereoselectivity in radical cyclization. The required selenium containing radical precursors were synthesised from 2-cyanoaziridines by addition of organometallic reagents, reduction of the resulting aziridine ketone, and benzeneselenol ring-opening of the aziridine. Cyclization at 17 oC produced 2,4-disubstituted pyrrolidines substantially enriched in the trans-isomer (cis/trans = 1/9 – 1/12). Novel radical cyclization approaches to thiazolines and pyrrolines were also tried.

    The thesis also describes attempts to improve the Hassner aziridine synthesis by employing stannous chloride as a functional group tolerant reducing agent.

    Download full text (pdf)
    FULLTEXT01
  • 417.
    Bharate, Jaideep B.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ådén, Jörgen
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gharibyan, Anna
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Adolfsson, Dan E.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Jayaweera, Sanduni Wasana
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Singh, Pardeep
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Vielfort, Katarina
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Tyagi, Mohit
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bonde, Mari
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bergström, Sven
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    K2S2O8-mediated coupling of 6-amino-7-aminomethyl-thiazolino-pyridones with aldehydes to construct amyloid affecting pyrimidine-fused thiazolino-2-pyridones2021In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 19, no 44, p. 9758-9772Article in journal (Refereed)
    Abstract [en]

    We herein present the synthesis of diversely functionalized pyrimidine fused thiazolino-2-pyridones via K2S2O8-mediated oxidative coupling of 6-amino-7-(aminomethyl)-thiazolino-2-pyridones with aldehydes. The developed protocol is mild, has wide substrate scope, and does not require transition metal catalyst or base. Some of the synthesized compounds have an ability to inhibit the formation of Amyloid-β fibrils associated with Alzheimer's disease, while others bind to mature amyloid-β and α-synuclein fibrils.

    Download full text (pdf)
    fulltext
  • 418. Bharate, Jaideep B.
    et al.
    Ådén, Jörgen
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gharibyan, Anna
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Adolfsson, Dan E.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Jayaweera, Sanduni Wasana
    Vielfort, Katarina
    Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Singh, Pardeep
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Tyagi, Mohit
    Bergström, Sven
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    K2S2O8-mediated aerobic oxidative coupling of 6-amino-7-(aminomethyl)-thiazolino-pyridones with aldehydes: Direct access to highly functionalized pyrimidine fused thiazolino-2-pyridones with amyloid fibril binding activity or inhibitors of Amyloid-β fibril formationManuscript (preprint) (Other academic)
    Abstract [en]

    We herein present the synthesis of diversely functionalized pyrimidine fused thiazolino-2-pyridones via K2S2O8-mediated oxidative coupling of 6-amino-7-(aminomethyl)- thiazolino-2-pyridones with aldehydes. The developed protocol is mild, has wide substrate scope, and does not require transition metal catalyst or base. Some of the synthesized compounds have the ability to inhibit the formation of Amyloid-β fibrils associated with Alzheimer's disease, while others bind to mature Amyloid-β and α-Synuclein fibrils.

  • 419. Bhattacharjee, Snehasish
    et al.
    Chakraborty, Sandipan
    Chorell, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sengupta, Pradeep K.
    Bhowmik, Sudipta
    Importance of the hydroxyl substituents in the B-ring of plant flavonols on their preferential binding interactions with VEGF G-quadruplex DNA: Multi-spectroscopic and molecular modeling studies2018In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 118, p. 629-639Article in journal (Refereed)
    Abstract [en]

    G-quadruplex (G4) structures are known to be promising anticancer drug targets and flavonols (an important class of fiavonoids) are small molecules reported to possess several health-promoting properties including those of anticancer activities. In this work, we explored the interactions of the structurally related plant flavonols kaempferol (KAE; 3,5,7,4'-OH flavone) and morin (MOR; 3,5,7,2',4'-OH flavone) with various G4-DNA sequences along with duplex DNA using a combination of spectroscopic and molecular docking studies. Our results revealed that KAE shows preferential interaction with VEGF G4-DNA in comparison to the other G4 sequences and duplex DNA. Moreover, KAE enhances the thermal stability of VEGF G4-DNA. In contrast, MOR exhibits an appreciably weaker level of interaction with both duplex and various G4-DNAs, with no significant structural specificity. The contrasting DNA binding behaviors suggest a crucial role of the 2'-OH substituent in the Bring of flavonol moiety. While KAE is relatively planar, MOR adopts a significantly non-planar conformation attributable to steric hindrance from the additional 2'-OH substituent. This small structural difference is apparently very important for the ability of KAE and MOR to interact with VEGF G4-DNA. Thus, KAE (but not MOR) appears to be an effective ligand for VEGF G4-DNA, opening up possibilities of its application for regulation of gene expression in cancer cells. 

  • 420.
    Bhimpuria, Rohan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Baddigam, Kiran Reddy
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Xu, Felix
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Wells, Jordann A. L.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Synthetic Molecular Chemistry.
    Borbas, K. Eszter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Synthesis of styrene, phenyl acrylate and allyloxyphenyl-functionalized porphyrins, and preliminary exploration of their utility for assembling multiple porphyrin units2023In: Journal of Porphyrins and Phthalocyanines, ISSN 1088-4246, E-ISSN 1099-1409, Vol. 27, no 07N10, p. 1398-1408Article in journal (Refereed)
    Abstract [en]

    Three free-base and two Zn(II) porphyrins carrying one alkene-substituted meso-aryl group and three solubilizing pentyl groups were prepared via mixed aldehyde-type syntheses. A meso p-allyloxyphenyl porphyrin was obtained via the corresponding 5-(p-allyloxyphenyl) dipyrromethane. The porphyrins were fully characterized using a combination of NMR spectroscopy, high-resolution mass spectrometry, and UV-Vis absorption and emission spectroscopies. Two of the free-base porphyrins were heated in the presence of AIBN or benzoyl peroxide as the initiator. The major isolated products of these reactions contained two porphyrin units based on the results of MALDI-MS and H-1 NMR analysis data, which was supported by the results of FTIR, UV-Vis absorption and emission spectroscopies, and gel permeation and liquid chromatographies. Additionally, the acrylamide-functionalized porphyrin could be attached to a polylysine scaffold under basic conditions. These results suggest that the olefinic handle can be used to assemble structures containing multiple porphyrinic macrocycles.

  • 421.
    Bhowmick, Asmit
    et al.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Simon, Philipp S.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Bogacz, Isabel
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Hussein, Rana
    Department of Biology, Humboldt-Universität zu Berlin, Berlin, Germany.
    Zhang, Miao
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Makita, Hiroki
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Ibrahim, Mohamed
    Department of Biology, Humboldt-Universität zu Berlin, Berlin, Germany.
    Chatterjee, Ruchira
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Doyle, Margaret D.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Cheah, Mun Hon
    Molecular Biomimetics, Department of Chemistry-Ångström, Uppsala University, Uppsala, Sweden.
    Chernev, Petko
    Molecular Biomimetics, Department of Chemistry-Ångström, Uppsala University, Uppsala, Sweden.
    Fuller, Franklin D.
    Linac Coherent Light Source, SLAC National Accelerator Laboratory, CA, Menlo Park, United States.
    Fransson, Thomas
    Department of Physics, AlbaNova University Center, Stockholm University, Stockholm, Sweden.
    Alonso-Mori, Roberto
    Linac Coherent Light Source, SLAC National Accelerator Laboratory, CA, Menlo Park, United States.
    Brewster, Aaron S.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Sauter, Nicolas K.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Bergmann, Uwe
    Department of Physics, University of Wisconsin-Madison, WI, Madison, United States.
    Dobbek, Holger
    Department of Biology, Humboldt-Universität zu Berlin, Berlin, Germany.
    Zouni, Athina
    Department of Biology, Humboldt-Universität zu Berlin, Berlin, Germany.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Molecular Biomimetics, Department of Chemistry-Ångström, Uppsala University, Uppsala, Sweden.
    Kern, Jan
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Yachandra, Vittal K.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Yano, Junko
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Going around the Kok cycle of the water oxidation reaction with femtosecond X-ray crystallography2023In: IUCrJ, E-ISSN 2052-2525, Vol. 10, no 6, p. 642-655Article, review/survey (Refereed)
    Abstract [en]

    The water oxidation reaction in photosystem II (PS II) produces most of the molecular oxygen in the atmosphere, which sustains life on Earth, and in this process releases four electrons and four protons that drive the downstream process of CO2 fixation in the photosynthetic apparatus. The catalytic center of PS II is an oxygen-bridged Mn4Ca complex (Mn4CaO5) which is progressively oxidized upon the absorption of light by the chlorophyll of the PS II reaction center, and the accumulation of four oxidative equivalents in the catalytic center results in the oxidation of two waters to dioxygen in the last step. The recent emergence of X-ray free-electron lasers (XFELs) with intense femtosecond X-ray pulses has opened up opportunities to visualize this reaction in PS II as it proceeds through the catalytic cycle. In this review, we summarize our recent studies of the catalytic reaction in PS II by following the structural changes along the reaction pathway via room-temperature X-ray crystallography using XFELs. The evolution of the electron density changes at the Mn complex reveals notable structural changes, including the insertion of OX from a new water molecule, which disappears on completion of the reaction, implicating it in the O-O bond formation reaction. We were also able to follow the structural dynamics of the protein coordinating with the catalytic complex and of channels within the protein that are important for substrate and product transport, revealing well orchestrated conformational changes in response to the electronic changes at the Mn4Ca cluster.

    Download full text (pdf)
    fulltext
  • 422. Bhowmick, Asmit
    et al.
    Simon, Philipp S.
    Bogacz, Isabel
    Hussein, Rana
    Zhang, Miao
    Makita, Hiroki
    Ibrahim, Mohamed
    Chatterjee, Ruchira
    Doyle, Margaret D.
    Cheah, Mun Hon
    Chernev, Petko
    Fuller, Franklin D.
    Fransson, Thomas
    Stockholm University, Faculty of Science, Department of Physics.
    Alonso-Mori, Roberto
    Brewster, Aaron S.
    Sauter, Nicolas K.
    Bergmann, Uwe
    Dobbek, Holger
    Zouni, Athina
    Messinger, Johannes
    Kern, Jan
    Yachandra, Vittal K.
    Yano, Junko
    Going around the Kok cycle of the water oxidation reaction with femtosecond X-ray crystallography2023In: IUCrJ, E-ISSN 2052-2525, Vol. 10, p. 642-655Article, review/survey (Refereed)
    Abstract [en]

    The water oxidation reaction in photosystem II (PS II) produces most of the molecular oxygen in the atmosphere, which sustains life on Earth, and in this process releases four electrons and four protons that drive the downstream process of CO2 fixation in the photosynthetic apparatus. The catalytic center of PS II is an oxygen-bridged Mn4Ca complex (Mn4CaO5) which is progressively oxidized upon the absorption of light by the chlorophyll of the PS II reaction center, and the accumulation of four oxidative equivalents in the catalytic center results in the oxidation of two waters to dioxygen in the last step. The recent emergence of X-ray free-electron lasers (XFELs) with intense femtosecond X-ray pulses has opened up opportunities to visualize this reaction in PS II as it proceeds through the catalytic cycle. In this review, we summarize our recent studies of the catalytic reaction in PS II by following the structural changes along the reaction pathway via room-temperature X-ray crystallography using XFELs. The evolution of the electron density changes at the Mn complex reveals notable structural changes, including the insertion of O-X from a new water molecule, which disappears on completion of the reaction, implicating it in the O-O bond formation reaction. We were also able to follow the structural dynamics of the protein coordinating with the catalytic complex and of channels within the protein that are important for substrate and product transport, revealing well orchestrated conformational changes in response to the electronic changes at the Mn4Ca cluster.

  • 423.
    Biasi, P.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemical Engineering, Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre (PCC), Åbo Akademi University, Åbo-Turku, Finland.
    Salmi, T.
    Department of Chemical Engineering, Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre (PCC), Åbo Akademi University, Åbo-Turku, Finland.
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemical Engineering, Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre (PCC), Åbo Akademi University, Åbo-Turku, Finland.
    Tailoring the process of H2O2 direct synthesis: Catalyst design and reaction engineering to reach an industrial feasibility2014In: 21st International Congress of Chemical and Process Engineering, CHISA 2014 and 17th Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction, PRES 2014, Czech Society of Chemical Engineering , 2014, p. 65-65Conference paper (Refereed)
  • 424.
    Bidleman, Terry F.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ericson, Lars
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Liljelind, Per
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Tysklind, Mats
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Drosophilin a methyl ether (DAME) and other chlorinated dimethoxybenzenes in fungi and forest litter from Sweden2023In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 347, article id 140685Article in journal (Refereed)
    Abstract [en]

    Fungi and substrates undergoing fungal decomposition were collected from forests in northern and southernSweden and analyzed for chlorinated dimethoxybenzenes (DMBs). Specimens were fungi fruiting bodies, rottingwood, forest litter and underlying humus. Targeted compounds were DAME (1,2,4,5-tetrachloro-3,6-DMB) andrelated fungal secondary metabolites. A screening procedure was developed which involved soaking the speci-mens in ethyl acetate followed by analysis by capillary gas chromatography – mass spectrometry with mass selec-tive detection (GC-MSD). DAME was the most frequently found (62% of 47 specimens) and often the most abun-dant target compound, with range and mean ± SD concentrations of <0.0017–3.81 and 0.21 ± 0.63 mg kg−1ww. Based on log-log correlations of partition coefficients of hydrophobic compounds between fungal biomass/water (KD) and octanol/water (KOW), five species of fungi are suggested to produce DAME de novo versus bioaccu-mulation from forest runoff water. Full-scan mass spectra of some high-concentration specimens indicated thepresence of a Cl2DMB and a Cl3DMB, which could not be identified further due to lack of standards, anddrosophilin A (DA = 2,3,5,6-tetrachloro-4-methoxyphenol), the precursor to DAME. Tetrachloroveratrole(TeCV = 1,2,3,4-tetrachloro-5,6-DMB) was found in only a few specimens. This study supports our hypothesis offungi as a source of DAME in terrestrial runoff and indicates that other chlorinated secondary metabolites arepresent. DAME is widely distributed globally, and it would be good to have a better understanding of its sourcesand pathways as a marker of terrestrial organochlorines and their availability for bioaccumulation

    Download full text (pdf)
    fulltext
  • 425.
    Bidleman, Terry Frank
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Air Quality Processes Research Section, Environment Canada.
    Jantunen, L. M.
    Hung, H.
    Ma, J.
    Stern, G. A.
    Rosenberg, B.
    Racine, J.
    Annual cycles of organochlorine pesticide enantiomers in Arctic air suggest changing sources and pathways2015In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 15, no 3, p. 1411-1420Article in journal (Refereed)
    Abstract [en]

    Air samples collected during 1994-2000 at the Canadian Arctic air monitoring station Alert (82 degrees 30'N, 62 degrees 20'W) were analysed by enantiospecific gas chromatography-mass spectrometry for alpha-hexachlorocyclohexane (alpha-HCH), trans-chlordane (TC) and cis-chlordane (CC). Results were expressed as enantiomer fractions (EF = peak areas of (+)/[(+) + (-)] enantiomers), where EFs = 0.5, <0.5 and >0.5 indicate racemic composition, and preferential depletion of (+) and (-) enantiomers, respectively. Long-term average EFs were close to racemic values for alpha-HCH (0.504 +/- 0.004, n = 197) and CC (0.505 +/- 0.004, n = 162), and deviated farther from racemic for TC (0.470 +/- 0.013, n = 165). Digital filtration analysis revealed annual cycles of lower alpha-HCH EFs in summer-fall and higher EFs in winter-spring. These cycles suggest volatilization of partially degraded alpha-HCH with EF < 0.5 from open water and advection to Alert during the warm season, and background transport of alpha-HCH with EF > 0.5 during the cold season. The contribution of sea-volatilized alpha-HCH was only 11% at Alert, vs. 32% at Resolute Bay (74.68 degrees N, 94.90 degrees W) in 1999. EFs of TC also followed annual cycles of lower and higher values in the warm and cold seasons. These were in phase with low and high cycles of the TC / CC ratio (expressed as F-TC = TC/(TC + CC)), which suggests greater contribution of microbially "weathered" TC in summer-fall versus winter-spring. CC was closer to racemic than TC and displayed seasonal cycles only in 1997-1998. EF profiles are likely to change with rising contribution of secondary emission sources, weathering of residues in the environment, and loss of ice cover in the Arctic. Enantiomer-specific analysis could provide added forensic capability to air monitoring programs.

    Download full text (pdf)
    fulltext
  • 426.
    Bielawski, Marcin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Diaryliodonium Salts: Development of Synthetic Methodologies and α-Arylation of Enolates2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes novel reaction protocols for the synthesis of diaryliodonium salts and also provides an insight to the mechanism of α-arylation of carbonyl compounds with diaryliodonium salts.

     The first chapter gives a general introduction to the field of hypervalent iodine chemistry, mainly focusing on recent developments and applications of diaryliodonium salts.

    Chapter two describes the synthesis of electron-rich to electron-poor diaryliodonium triflates, in moderate to excellent yields from a range of arenes and iodoarenes.

    In chapter three, it is described that molecular iodine can be used together with arenes in a direct one-pot, three-step synthesis of symmetric diaryliodonium triflates. A large scale synthesis of bis(4-tert-butylphenyl)iodonium triflate is also described, controlled and verified by an external research group, further demonstrating the reliability of this methodology.

    The fourth chapter describes the development of a sequential one-pot synthesis of diaryliodonium salts from aryl iodides and boronic acids, furnishing symmetric and unsymmetric, electron-rich to electron-poor diaryliodonium tetrafluoroborates in moderate to excellent yields. This method was developed to overcome the regiochemical limitations imposed by the reaction mechanism in the protocols described in the preceding chapters.

    Chapter five describes a one-pot synthesis of heteroaromatic iodonium salts under similar conditions described in chapter two.

    The final chapter describes the reaction of enolates with chiral diaryliodonium salts or together with a phase transfer catalyst yielding racemic products. DFT calculations were performed, which revealed a low lying energy transition state (TS) between intermediates, which is believed to be responsible for the lack of selectivity observed in the experimental work. It is also proposed that a [2,3] rearrangement is preferred over a [1,2] rearrangement in the α-arylation of carbonyl compounds.

    The synthetic methodology described in this thesis is the most generally applicable, efficient and high-yielding to date for the synthesis of diaryliodonium salts, making these reagents readily available for various applications in synthesis.

    Download full text (pdf)
    FULLTEXT01
    Download (pdf)
    errata
  • 427.
    Bielawski, Marcin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient and High-Yielding Routes to Diaryliodonium Salts2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

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

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

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

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

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

    Download full text (pdf)
    FULLTEXT01
  • 428.
    Bielawski, Marcin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Aili, David
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Regiospecific One-Pot Synthesis of Diaryliodonium Tetrafluoroborates from Arylboronic Acids and Aryl Iodides2008In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 73, no 12, p. 4602-4607Article in journal (Refereed)
    Abstract [en]

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

  • 429.
    Bielawski, Marcin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient one-pot synthesis of bis(4-tert-butylphenyl)iodonium triflate2009In: Organic Syntheses, ISSN 0078-6209, E-ISSN 2333-3553, Vol. 86, p. 308-314Article in journal (Refereed)
    Download full text (pdf)
    Ar2I Org Synth
  • 430.
    Bielawski, Marcin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    High-Yielding One-Pot Synthesis of Diaryliodonium Triflates from Arenes and Iodine or Aryl Iodides2007In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, no 24, p. 2521-2523Article in journal (Refereed)
    Abstract [en]

    Unsymmetric and symmetric diaryliodonium triflates are synthesized from both electron-deficient and electron-rich substrates in a fast, high yielding, and operationally simple protocol employing arenes and aryl iodides or iodine.

    Download full text (pdf)
    fulltext
  • 431.
    Bielawski, Marcin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhu, Mingzhao
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient and General One-Pot Synthesis of Diaryliodonium Triflates: Optimization, Scope and Limitations2007In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 349, no 17-18, p. 2610-2618Article in journal (Refereed)
    Abstract [en]

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

  • 432.
    Bielawski, Marcin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhu, Mingzhao
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient and general one-pot synthesis of diaryliodonium triflates: scope and limitations2007In: SIS Report: The 10th Symposium on Iodine Science, Chiba University, Japan 2007, 2007, p. 19-22Conference paper (Other academic)
    Download full text (pdf)
    fulltext
  • 433.
    Billinger, Erika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Biochemistry.
    Zuo, Shusheng
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Biochemistry.
    Johansson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Biochemistry.
    Characterization of Serine Protease Inhibitor from Solanum tuberosum Conjugated to Soluble Dextran and Particle Carriers2019In: ACS Omega, E-ISSN 2470-1343, Vol. 4, no 19, p. 18456-18464Article, review/survey (Refereed)
    Abstract [en]

    A serine protease inhibitor was extracted from potato tubers. The inhibitor was conjugated to soluble, prefractionated dextran and titanium dioxide and zinc oxide nanoparticles. Conjugation to dextran was achieved by periodate oxidation of the dextran, followed by Schiff base coupling to inhibitor amino groups, and finally reduction, whereas the conjugation to the oxide particles was carried out by aminosilanization and carbonyldiimidazole activation. The inhibitory effect of the conjugated inhibitor was compared to that of free inhibitor in solution and with gelatin gel as a direct substrate. A certain degree of inhibitory activity was retained for both the dextran-conjugated and particle-conjugated inhibitors. In particular, the apparent Ki value of the dextran-conjugated inhibitor was found to be in the same range as that for free inhibitor. The dextran conjugate retained a higher activity than the free inhibitor after 1 month of storage at room temperature.

    Download full text (pdf)
    fulltext
  • 434. Biosca, Maria
    et al.
    Paptchikhine, Alexander
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pàmies, Oscar
    Andersson, Pher G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Diéguez, Montserrat
    Extending the Substrate Scope of Bicyclic P-Oxazoline/Thiazole Ligands for Ir-Catalyzed Hydrogenation of Unfunctionalized Olefins by Introducing a Biaryl Phosphoroamidite Group2015In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, no 8, p. 3455-3464Article in journal (Refereed)
    Abstract [en]

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

    Download full text (pdf)
    fulltext
  • 435.
    Biswas, Dipsikha
    et al.
    Dalhousie Med New Brunswick, St John, NB, Canada.
    Cowie, Andrew
    Dalhousie Med New Brunswick, St John, NB, Canada.
    Tozer, Kathleen
    Dalhousie Med New Brunswick, St John, NB, Canada.
    Perez, Lester J.
    Dalhousie Med New Brunswick, St John, NB, Canada.
    Trivedi, Purvi
    Dalhousie Med New Brunswick, St John, NB, Canada.
    Bartlett, Jordan J.
    Dalhousie Med New Brunswick, St John, NB, Canada.
    Duffley, Luke
    Univ New Brunswick, St John, NB, Canada.
    Dao, Khoi Thien
    Univ New Brunswick, St John, NB, Canada.
    Paramel Varghese, Geena
    Dalhousie Med New Brunswick, St John, NB, Canada..
    Aguiar, Christie
    St Johns Hosp, St John, NB, Canada.
    Yip, Alexandra M.
    St Johns Hosp, St John, NB, Canada.
    Shea, Jennifer
    St Johns Hosp, St John, NB, Canada.
    Brunt, Keith
    Dalhousie Med New Brunswick, St John, NB, Canada.
    Legare, Jean-Francois
    St Johns Hosp, St John, NB, Canada.
    Hassan, Ansar
    St Johns Hosp, St John, NB, Canada.
    Kienesberger, Petra
    Dalhousie Med New Brunswick, St John, NB, Canada.
    Pulinilkunnil, Thomas
    Dalhousie Med New Brunswick, St John, NB, Canada.
    Adverse Cardiometabolic Outcomes in Obese Patients Correlates Strongly with Defective Branched-Chain Amino Acid Catabolism2018In: Journal of Molecular and Cellular Cardiology, ISSN 0022-2828, E-ISSN 1095-8584, Vol. 124, p. 121-122Article in journal (Other academic)
    Download full text (pdf)
    sammanfattning
  • 436.
    Björk, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Sanchez-Sanchez, Carlos
    Swiss Fed Labs Mat Sci & Technol, Switzerland; Inst Mat Sci Madrid ICMM CSIC, Spain.
    Chen, Qiang
    Max Planck Inst Polymer Res, Germany; Univ Oxford, England.
    Pignedoli, Carlo A.
    Swiss Fed Labs Mat Sci & Technol, Switzerland.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Ruffieux, Pascal
    Swiss Fed Labs Mat Sci & Technol, Switzerland.
    Feng, Xinliang
    Tech Univ Dresden, Germany; Tech Univ Dresden, Germany.
    Narita, Akimitsu
    Max Planck Inst Polymer Res, Germany; Okinawa Inst Sci & Technol Grad Univ, Japan.
    Mullen, Klaus
    Max Planck Inst Polymer Res, Germany.
    Fasel, Roman
    Swiss Fed Labs Mat Sci & Technol, Switzerland; Univ Bern, Switzerland.
    The Role of Metal Adatoms in a Surface-Assisted Cyclodehydrogenation Reaction on a Gold Surface2022In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 61, no 49, article id e202212354Article in journal (Refereed)
    Abstract [en]

    Dehydrogenation reactions are key steps in many metal-catalyzed chemical processes and in the on-surface synthesis of atomically precise nanomaterials. The principal role of the metal substrate in these reactions is undisputed, but the role of metal adatoms remains, to a large extent, unanswered, particularly on gold substrates. Here, we discuss their importance by studying the surface-assisted cyclodehydrogenation on Au(111) as an ideal model case. We choose a polymer theoretically predicted to give one of two cyclization products depending on the presence or absence of gold adatoms. Scanning probe microscopy experiments observe only the product associated with adatoms. We challenge the prevalent understanding of surface-assisted cyclodehydrogenation, unveiling the catalytic role of adatoms and their effect on regioselectivity. The study adds new perspectives to the understanding of metal catalysis and the design of on-surface synthesis protocols for novel carbon nanomaterials.

    Download full text (pdf)
    fulltext
  • 437.
    Björk, Linnea
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry.
    Synthesis of proteophenes that can be utilized as fluorescent ligands for biological targets2019Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    Small fluorescent probes are important tools when studying protein aggregates involved in different neurodegenerative diseases, such as Alzheimer’s disease. Luminescent conjugated oligothiophenes have been developed and shown to be excellent ligands when studying morphology among amyloids, due to their conjugated thiophene backbone that provides them with unique photophysical properties. This kind of probes are being developed successively to enhance the specificity of their biological targets. In this project, luminescent conjugated oligothiophenes functionalized with amino acids, so called proteophenes, have been synthesized to investigate their optical properties. Since amino acids are chiral molecules, the possibility of induced chirality to the thiophene backbone was examined, as well as the proteophenes ability to work as amyloidospecific ligands for the study of protein aggregates. The synthesis of four different proteophenes are presented in this report, along with analysis results of their photophysical properties.

    Download full text (pdf)
    fulltext
  • 438.
    Björk, Linnea
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Selegård, Robert
    Linköping University, Department of Physics, Chemistry and Biology, Biophysics and bioengineering. Linköping University, Faculty of Science & Engineering.
    Bäck, Marcus
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Hammarström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Lindgren, Mikael
    Norwegian Univ Sci & Technol, Norway.
    Nilsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Amino-Acid Side-Chain Nanoarchitectonics for Tuning the Chiroptical Properties and Supramolecular Structure of Pentameric Oligothiophenes2024In: ChemPhotoChem, E-ISSN 2367-0932Article in journal (Refereed)
    Abstract [en]

    Oligothiophenes with specific photophysical properties and molecular organization are of great interest, since this class of materials are used in organic electronics and bioelectronics, as well as biosensing. Herein, 8 different pentameric oligothiophenes, denoted proteophenes, with different amino acid substitution patterns at distinct positions along the thiophene backbone were investigated. Spectroscopic and microscopic studies of the ligands revealed the formation of optically active self-assembled materials under acidic or basic conditions. The distinct photophysical characteristics, including induced circular dichroism, as well as the supramolecular structures of the assemblies deduced from light scattering and transmission electron microscopy, were highly influenced by the positioning of distinct amino acid moieties along the thiophene backbone. Proteophenes functionalized with only glutamate residues or these functionalities in combination with hydrophobic valine moieties formed fibrillar structures with excellent chiroptical properties under acidic conditions. In addition, the amino acid functionality at the beta-position of distinct thiophene moieties influenced the induced circular dichroism pattern observed from the proteophenes. Overall, the obtained results demonstrate how changes in the position of various amino acid functionalities, as well as the chemical nature of the amino acid side chain functionality greatly affect the optical properties as well as the architecture of the self-assembled materials. Self-assembled Proteophenes. Oligothiophenes with distinct amino acid side-chain functionalities along the conjugated backbone displayed distinct chiroptical and structural properties in acidic or alkaline solutions. The distinct photophysical characteristics, as well as the supramolecular structures of the assemblies were highly influenced by the chemical nature of the amino acid, as well as the positioning of distinct amino acid moieties along the thiophene backbone.image

  • 439.
    Björk, Malin
    Södertörn University, School of Life Sciences. Karolinska Institutet.
    Synthesis of sulfur and seleniumn heterocycles, including derivatives of imidazopyridine and benzimidazole2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The chemistry developed in this thesis can be divided into two parts. The first part, which is the major part of the thesis, contains syntheses towards analogues to mutagenic heterocyclic amines found in e.g. meat fried at high temperatures. The second part concentrates on the palladium-(0)catalyzed cross-coupling reactions of 4- and 5-substituted 2,1,3-benzoselenadiazoles. The heterocyclic amines described can be divided into the linear and the angular compounds. Five linear imidazo[4,5-b]pyridines were synthesised via the Friedländer reaction: 2-amino-1 - methylbenzothieno[2,3-e]imidazo[4,5-b]pyridine, 2-amino-1-methy-benzothieno [3,2-e] imidazo[4,5-b] pyridine, 2-amino-1-methylthieno[2,3-elimidazo[4,5-b]-pyridine, 2-amino-1methylthieno[3,2-e]imidazo[4,5-b]pyridine and the sulfur analogue to the cooked-food mutagen IFP, 2-amino- 1,6-dimethylthieno[2,3-e]imidazo[4,5-b]pyridine. Attempts were made to form three thienoimidazo[4,5-b]pyridines via stepwise condensation. The first condensation between creatinine and 2-nitro-3-thiophene-carbaldehyde, 3-amino-2thiophenecarbaldehyde and 4-azido3-thiophenecarbaldehyde yielded thenylidenomethyleneimidazolinones, but only one of these gave the ring closed compound 2-amino-1-methylthieno[2,3-e]imidazo[4,5-b]pyridine by a second condensation. In addition, 2-amino- 1 methyl benzoth ieno[3,2-e] imidazo[4,5 -b] pyridine was transformed into the 2-nitro- and 2-hydroxy derivative. The last linear isomer 2-amino-1methylimidazo[4,5-b]benzothiophene, was synthesized by a different route. The series of angular compounds are considered analogues to the food-mutagen IQx. A series of six homologues of 7-amino-imidazo[4,5-e]-2,1,3-benzoselenadiazoles. Four ring systems were obtained by treating 4-methylamino-3-nitro-phenylenedianmine with a range of biselectrophiles, namely: 2-amino-1-methylbenzo-thiadiazole, -triazole, -diazepinone and 2amino1 -methylimidazobenzimidazole. Among the palladium-(0)-catalyzed cros s- couplings, the Suzuki, Stille, Fleck and Sonogashira reactions were used. These were applied to 4-, or 5-bromo-2,1,3-benzoselenadiazoles. In addition, the 4- and 5-trimethyltin-2,1,3-benzoselenadiazole were synthesized.

  • 440.
    Björk, Malin
    et al.
    Södertörn University, School of Life Sciences. Karolinska Institutet.
    Grivas, Spiros
    Södertörn University, School of Life Sciences. Karolinska Institutet.
    Classical conditions of Suzuki, Stille, Heck and Sonogashira couplings applied on 4- and 5-substituted 2,1,3-benzoselenadiazolesManuscript (preprint) (Other academic)
  • 441.
    Björk, Malin
    et al.
    Södertörn University, School of Life Sciences. Karolinska Institutet.
    Grivas, Spiros
    Södertörn University, School of Life Sciences. Karolinska Institutet.
    Synthesis of imidazo[4,5-e]-2,1,3-benzoselenadiazoles and derivatives thereofManuscript (preprint) (Other academic)
  • 442.
    Björk, Malin
    et al.
    Södertörn University, School of Life Sciences. Karolinska Institute.
    Grivas, Spiros
    Södertörn University, School of Life Sciences. Karolinska Institute.
    Synthesis of novel 2-aminoimidazo[4,5-b]pyridines, including the thieno analogue of the cooked-food mutagen IFP2006In: Journal of Heterocyclic Chemistry, ISSN 0022-152X, E-ISSN 1943-5193, Vol. 43, no 1, p. 101-109Article in journal (Refereed)
    Abstract [en]

    Eight new compounds, including three new ring systems obtained via the Friedlander condensation of ortho-aminothiophenecarbaldehydes 11, 21 and 24 with creatinine (8), are reported. The condensation afforded 1, which is the thieno analogue of the cooked-food mutagen IFP (2-amino-1,6-dimethylfuro[2,3-e]imidazo[4,5-b]pyridine), and the benzothieno[2,3-e]- and benzothieno[3,2-e]imidazo[4,5-b]pyridines 2 and 3. Attempts to condense 11 with isocreatinine (12) were unsuccessful. Desulfurization of 3 gave the known cooked-food carcinogen PhIP. The 2-nitro (4) and 2-hydroxy (5) derivatives of 3 are reported. The related 2-amino-1-methyl-imidazo[4,5-b]benzothiophene (25) was synthesized by a different route. Fully assigned H-1 and C-13 nmr data of all new compounds are reported.

  • 443.
    Björk, Malin
    et al.
    Södertörn University, School of Life Sciences. Karolinska Institutet.
    Grivas, Spiros
    Södertörn University, School of Life Sciences. Karolinska Institutet.
    Synthesis of thienoimidazo[4,5-b]pyridines and thenylidenoimidazolinones2005In: Heterocycles, ISSN 0385-5414, E-ISSN 1881-0942, Vol. 65, no 10, p. 2369-2380Article in journal (Refereed)
    Abstract [en]

    The two isomers 2-amino-1-methylimidazo[4,5-b]thieno[3,2-e]pyridine (3) and 2-amino-1-methylimidazo[4,5-b]thieno[2,3-e]pyridine (4) were synthesized by the Friedlander reaction starting from creatinine and the appropriate aminothiophenecarbaldehydes (11 and 13). Creatinine was also condensed with 2-nitro-3-thiophenecarbaldehyde (10) in ethylene glycol to yield the 2-amino-1-methyl-5-[2-(2-nitro-3-thenylidene)]-2-imidazolin-4-one (7a), with 3-amino-2-thiophenecarbaldehyde (13) under Perkin conditions to yield 2-acetamido-5-[2-(3-acetamido-2-thenylidene)]-1-methyl-2-imidazolin-4-on e (8), and with 4-azido-3-thiophenecarbaldehyde (17) in acetic acid to yield 2-amino-5[2-(4-azido-3-thenylidene)]-1-methyl-2-imidazolin-4-one (9). The thenylidenoimidazolinonc (8) was converted into compound (4).

  • 444.
    Björklund, Catarina
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Design and Synthesis of BACE-1 Inhibitors: Novel Compounds Targeting an Aspartic Protease Important in the Pathogenesis of Alzheimer’s Disease2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

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

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

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

  • 445.
    Björklund Jansson, Marianne
    et al.
    RISE, Innventia.
    Nilvebrant, N. -O
    Wood Extractives2009In: Wood Chemistry and Wood Biotechnology, Walter de Gruyter, 2009, p. 147-171Chapter in book (Refereed)
  • 446.
    Björndal, Håkan
    Stockholm University.
    Studies on some polysaccarides from wood-destroying fungi1970Doctoral thesis, comprehensive summary (Other academic)
  • 447.
    Björsne, Magnus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of potential candidates for therapeutic intervention against the human immunodeficiency virus1995Doctoral thesis, comprehensive summary (Other academic)
  • 448.
    Blasi Romero, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Nanotechnology and Functional Materials.
    Ångström, Molly
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Nanotechnology and Functional Materials.
    Franconetti, Antonio
    Muhammad, Taj
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Farmakognosi. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Jiménez-Barrero, Jesús
    Göransson, Ulf
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Farmakognosi. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Palo-Nieto, Carlos
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Nanotechnology and Functional Materials.
    Ferraz, Natalia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Nanotechnology and Functional Materials.
    KR-12 derivatives endow nanocellulose with antibacterial and anti-inflammatory properties: Role of conjugation chemistry2023In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 15, no 20, p. 24186-24196Article in journal (Refereed)
    Abstract [en]

    This work combines the wound-healing-related properties of the host defense peptide KR-12 with wood-derived cellulose nanofibrils (CNFs) to obtain bioactive materials, foreseen as a promising solution to treat chronic wounds. Amine coupling through carbodiimide chemistry, thiol-ene click chemistry, and Cu(I)-catalyzed azide-alkyne cycloaddition were investigated as methods to covalently immobilize KR-12 derivatives onto CNFs. The effects of different coupling chemistries on the bioactivity of the KR12-CNF conjugates were evaluated by assessing their antibacterial activities against Escherichia coli and Staphylococcus aureus. Potential cytotoxic effects and the capacity of the materials to modulate the inflammatory response of lipopolysaccharide (LPS)-stimulated RAW 245.6 macrophages were also investigated. The results show that KR-12 endowed CNFs with antibacterial activity against E. coli and exhibited anti-inflammatory properties and those conjugated by thiol-ene chemistry were the most bioactive. This finding is attributed to a favorable peptide conformation and accessibility (as shown by molecular dynamics simulations), driven by the selective chemistry and length of the linker in the conjugate. The results represent an advancement in the development of CNF-based materials for chronic wound care. This study provides new insights into the effect of the conjugation chemistry on the bioactivity of immobilized host defense peptides, which we believe to be of great value for the use of host defense peptides as therapeutic agents.

  • 449.
    Blid, Jan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Asymmetric [2,3]-Sigmatropic Rearrangement of Allylic Ammonium Ylides2005Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The thesis describes the realization of an asymmetric [2,3]-sigmatropic rearrangement of achiral allylic amines. It is divided into two parts; the first part deals with the development of a Lewis acid-mediated [2,3]-sigmatropic rearrangement and the second the asymmetric version thereof. Quaternization of an -amino amide with various Lewis acids established BBr3 and BF3 to be the most appropriate ones. Various allylic amines were subsequently rearranged into the corresponding homoallylic amines in good to excellent syn-diastereoselectivities, revealing the endo-transition state to be the preferred pathway. The structures of the intermediate Lewis acid-amine complexes were confirmed by NMR spectroscopy studies and DFT calculations.

    Based on this investigation a chiral diazaborolidine was chosen as Lewis acid and was shown to efficiently promote the asymmetric [2,3]-sigmatropic rearrangement furnishing homoallylic amines in good yields and excellent enantiomeric excesses. In contrast to the achiral rearrangement mediated by BBr3 and BF3, the asymmetric version gave the opposite major diastereomer, revealing a preference for the exo-transition state in the asymmetric rearrangement. To account for the observed selectivities, a kinetic and thermodynamic pathway was presented. On the basis of a deuterium exchange experiment on a rearranged Lewis acid-amine complex and an NMR spectroscopic investigation, the kinetic pathway was shown to be favored.

    Download full text (pdf)
    FULLTEXT01
  • 450.
    Blid, Jan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Panknin, Olaf
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Tuzina, Pavel
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Somfai, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Lewis acid mediated asymmetric 2,3 -sigmatropic rearrangement of allylic amines. Scope and mechanistic investigation2007In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 72, no 4, p. 1294-1300Article in journal (Refereed)
    Abstract [en]

    [GRAPHIC] The first asymmetric [2,3]-sigmatropic rearrangement of achiral allylic amines has been realized by quaternization of the amines with an enantiomerically pure diazaborolidine and subsequent treatment with Et3N. The resultant homoallylic amines were obtained in good yields and excellent ee's. The observed diastereo- and enantioselectivities were rationalized by invoking a kinetically controlled process, and support for this model was obtained from an NMR spectroscopic investigation of the chiral Lewis acid-substrate complex. The structure of the Lewis acid-product complex was established by X-ray crystallographic analysis and supported the proposed mechanism.

6789101112 401 - 450 of 4163
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf