• Aldol condensations on a 3-alkylidene-2,5-diketopiperazine - synthesis of two marine natural products 

      Fairhurst, Magnus John E.; Muhammad, Zeeshan; Haug, Bengt Erik; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06)
      The synthesis of two marine natural products containing a 3-alkylidene-6-arylidene-2,5-diketopiperazine scaffold by employing two consecutive aldol condensations starting with 1,4-diacetyl-2,5-diketopiperazine is reported. The target compounds contain a phenol or an imidazole group as aryl substituents, respectively, and suitable conditions for the aldol condensation of 1-acyl-3-alkylidene-2,5-dik ...
    • Antimicrobial activity of amphipathic α,α-disubstituted β-amino amide derivatives against ESBL–CARBA producing multi-resistant bacteria; effect of halogenation, lipophilicity and cationic character 

      Paulsen, Marianne Hagensen; Ausbacher, Dominik; Bayer, Annette; Engqvist, Magnus; Hansen, Terkel; Haug, Tor; Anderssen, Trude; Andersen, Jeanette Hammer; Sollid, Johanna U. Ericson; Strøm, Morten B. (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-09-06)
      The rapid emergence and spread of multi-resistant bacteria have created an urgent need for new antimicrobial agents. We report here a series of amphipathic α,α-disubstituted β-amino amide derivatives with activity against 30 multi-resistant clinical isolates of Gram-positive and Gram-negative bacteria, including isolates with extended spectrum β-lactamase – carbapenemase (ESBL-CARBA) production. A ...
    • Caesium Fluoride-Mediated Hydrocarboxylation of Alkenes and Allenes: Scope and Mechanistic Insights 

      Gevorgyan, Ashot; Obst, Marc; Guttormsen, Yngve; Maseras, Feliu; Hopmann, Kathrin Helen; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-09-11)
      A caesium fluoride-mediated hydrocarboxylation of olefins is disclosed that does not rely on precious transition metal catalysts and ligands. The reaction occurs at atmospheric pressures of CO<sub>2</sub> in the presence of 9-BBN as a stoichiometric reductant. Stilbenes, β-substituted styrenes and allenes could be carboxylated in good yields. The developed methodology can be used for preparation of ...
    • Carbonylative Suzuki-Miyaura couplings of sterically hindered aryl halides: Synthesis of 2-aroylbenzoate derivatives 

      Ismael, Aya; Skrydstrup, Troels; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-10)
      We have developed a carbonylative approach to the synthesis of diversely substituted 2-aroylbenzoate esters featuring a new protocol for the carbonylative coupling of aryl bromides with boronic acids and a new strategy to favour carbonylative over non-carbonylative reactions. Two different synthetic pathways – (i) the alkoxycarbonylation of 2-bromo benzophenones and (ii) the carbonylative Suzuki–Miyaura ...
    • Computational and experimental insights into asymmetric Rh‐catalyzed hydrocarboxylation with CO2 

      Pavlovic, Ljiljana; Pettersen, Martin; Gevorgyan, Ashot; Vaitla, Janakiram; Bayer, Annette; Hopmann, Kathrin Helen (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-18)
      The asymmetric Rh‐catalyzed hydrocarboxylation of α,β‐unsaturated carbonyl compounds was originally developed by Mikami and co‐workers but gives only moderate enantiomeric excesses. In order to understand the factors controlling the enantioselectivity and to propose novel ligands for this reaction, we have used computational and experimental methods to study the Rh‐catalyzed hydrocarboxylation with ...
    • Computational and experimental insights into asymmetric Rh‐catalyzed hydrocarboxylation with CO2 

      Pavlovic, Ljiljana; Pettersen, Martin; Gevorgyan, Ashot; Vaitla, Janakiram; Bayer, Annette; Hopmann, Kathrin Helen (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-18)
      The asymmetric Rh‐catalyzed hydrocarboxylation of α,β‐unsaturated carbonyl compounds was originally developed by Mikami and co‐workers but gives only moderate enantiomeric excesses. In order to understand the factors controlling the enantioselectivity and to propose novel ligands for this reaction, we have used computational and experimental methods to study the Rh‐catalyzed hydrocarboxylation with ...
    • A concise SAR-analysis of antimicrobial cationic amphipathic barbiturates for an improved activity-toxicity profile 

      Langer, Manuel K; Rahman, Ataur; Dey, Hymonti; Anderssen, Trude; Zilioli, Francesco; Haug, Tor; Blencke, Hans-Matti; Stensvåg, Klara; Strøm, Morten B.; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-05)
      An amphipathic barbiturate mimic of the marine eusynstyelamides is reported as a promising class of antimicrobial agents. We hereby report a detailed analysis of the structure-activity relationship for cationic amphipathic N,N′ -dialkylated-5,5-disubstituted barbiturates. The influence of various cationic groups, hydrocarbon linkers and lipophilic side chains on the compounds’ antimicrobial potency ...
    • A Concise Total Synthesis of Breitfussin A and B 

      Pandey, Sunil Kumar; Guttormsen, Yngve; Haug, Bengt Erik; Hedberg, Christian; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)
    • Enantioselective incorporation of CO2: status and potential 

      Vaitla, Janakiram; Guttormsen, Yngve; Mannisto, Jere K.; Nova, Ainara; Repo, Timo; Bayer, Annette; Hopmann, Kathrin Helen (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-09-09)
      CO<sub>2</sub> is a promising and sustainable carbon feedstock for organic synthesis. New catalytic protocols for efficient incorporation of CO<sub>2</sub>into organic molecules are continuously being reported. However, little progress has been made in the enantioselective conversion of CO<sub>2</sub>to form enantioenriched molecules. In order to allow CO<sub>2</sub>to become a versatile carbon ...
    • Enhanced teaching and learning outcomes from restructuring a basic organic chemistry course 

      Hansen, Jørn Hedløy; Bayer, Annette; Haugland, Marius Myreng (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-10)
      The first course in organic chemistry is tough for many students, and motivation may be an additional serious problem if you are taking the course as a part of your study program but do not intend to become a chemist. The combination of long, speedy traditional lectures, complicated material and the use of an important new language (electron flow arrows) does not contribute to easing the cognitive ...
    • Experimental and four-component relativistic DFT studies of tungsten carbonyl complexes 

      Demissie, Taye Beyene; Kostenko, Nataliya; Komorovsky, Stanislav; Repisky, Michal; Isaksson, Johan; Bayer, Annette; Ruud, Kenneth (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-07-24)
      We present a theoretical and experimental study of the structure and nuclear magnetic resonance (NMR) parameters of the pentacarbonyltungsten complexes of η<sup>1</sup>-2-(trimethylstannyl)-4,5-dimethylphosphinine, η<sup>2</sup>-norbornene, and imidazolidine-2-thione. The three complexes have a pseudo-octahedral molecular structure with the six ligands bonded to the tungsten atom. The η<sup>1</sup ...
    • Exploration of New Biomass-Derived Solvents: Application to Carboxylation Reactions 

      Gevorgyan, Ashot; Hopmann, Kathrin Helen; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-07)
      A range of hitherto unexplored biomass‐derived chemicals have been evaluated as new sustainable solvents for a large variety of CO<sub>2</sub>‐based carboxylation reactions. Known biomass‐derived solvents (biosolvents) are also included in the study and the results are compared with commonly used solvents for the reactions. Biosolvents can be efficiently applied in a variety of carboxylation reactions, ...
    • A focused fragment library targeting the antibiotic resistance enzyme - Oxacillinase-48: Synthesis, structural evaluation and inhibitor design 

      Ahkter, Sundus; Lund, Bjarte Aarmo; Ismael, Aya; Langer, Manuel; Isaksson, Johan; Christopeit, Tony; Leiros, Hanna-Kirsti S.; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-02-10)
      β-Lactam antibiotics are of utmost importance when treating bacterial infections in the medical community. However, currently their utility is threatened by the emergence and spread of β-lactam resistance. The most prevalent resistance mechanism to β-lactam antibiotics is expression of β-lactamase enzymes. One way to overcome resistance caused by β-lactamases, is the development of β-lactamase ...
    • Formal C-H carboxylation of unactivated arenes with carbon dioxide 

      Gevorgyan, Ashot; Hopmann, Kathrin Helen; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-31)
      A formal C−H carboxylation of unactivated arenes using CO<sub>2</sub> in green solvents is described. The present strategy combines a sterically controlled Ir‐catalyzed C−H borylation followed by a Cu‐catalyzed carboxylation of the in situ generated organoboronates. The reaction is highly regioselective for the C−H carboxylation of 1,3‐disubstituted and 1,2,3‐trisubstituted benzenes, 1,2‐ or ...
    • Improved Buchwald–Hartwig Amination by the Use of Lipids and Lipid Impurities 

      Gevorgyan, Ashot; Hopmann, Kathrin Helen; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-25)
      The development of green Buchwald–Hartwig aminations has long been considered challenging, due to the high sensitivity of the reaction to the environment. Here we show that food-grade and waste vegetable oils, triglycerides originating from animals, and natural waxes can serve as excellent green solvents for Buchwald–Hartwig amination. We further demonstrate that amphiphiles and trace ingredients ...
    • Investigation of tetrasubstituted heterocycles reveals hydantoins as a promising scaffold for development of novel antimicrobials with membranolytic properties 

      Langer, Manuel K; Rahman, Ataur; Dey, Hymonti; Anderssen, Trude; Blencke, Hans-Matti; Haug, Tor; Stensvåg, Klara; Strøm, Morten B.; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-01-24)
      Mimics of antimicrobial peptides (AMPs) have been proposed as a promising class of antimicrobial agents. We report the analysis of five tetrasubstituted, cationic, amphipathic heterocycles as potential AMP mimics. The analysis showed that the heterocyclic scaffold had a strong influence on the haemolytic activity of the compounds, and the hydantoin scaffold was identified as a promising template for ...
    • Iridium-PHOX-mediated alkene hydrogenation: Isomerisation influences the stereochemical outcome 

      Hopmann, Kathrin Helen; Frediani, Luca; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-05-27)
      Recent experimental studies of iridium-phosphinooxazoline-mediated alkene hydrogenation indicated two dihydride species as resting states, with the minor isomer assumed to give rise to the major product enantiomer [Gruber and Pfaltz, Angew. Chem. Int. Ed. 2014, 53, 1896]. B3LYP-D2 calculations confirm the two dihydride intermediates as resting states but show that these species do not give rise to ...
    • Iron‐Catalyzed Carbenoid Transfer Reactions of Vinyl Sulfoxonium Ylides: An Experimental and Computational Study 

      Vaitla, Janakiram; Bayer, Annette; Hopmann, Kathrin Helen (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-10-15)
      A method for the generation of unprecedented vinyl carbenoids from sulfoxonium ylides has been developed and applied in the synthesis of a diverse array of heterocycles such as indolizines, pyrroles, 3‐pyrrolin‐2‐ones, and furans. The reactions proceed by FeBr<sub>2</sub> catalysis under mild reaction conditions with a broad substrate scope. A reaction pathway involving iron carbenoids is proposed ...
    • Lipids as Versatile Solvents for Chemical Synthesis 

      Gevorgyan, Ashot; Hopmann, Kathrin Helen; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-23)
      Development of safe, renewable, cheap and versatile solvents is a longstanding challenge in chemistry. We show here that vegetable oils and related systems can become prominent solvents for organic synthesis. Suzuki–Miyaura, Hiyama, Stille, Sonogashira and Heck cross-couplings proceed with quantitative yields in a range of vegetable oils, fish oil, butter and waxes used as solvents. Appropriate ...
    • Mechanistic Insights into Copper-Catalyzed Carboxylations 

      Obst, Marc; Gevorgyan, Ashot; Bayer, Annette; Hopmann, Kathrin Helen (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-02)
      The copper-NHC-catalyzed carboxylation of organoboranes with CO<sub>2</sub> was investigated using computational and experimental methods. The DFT and DLPNO-CCSD(T) results indicate that nonbenzylic substrates are converted via an inner-sphere carboxylation of an organocopper intermediate, whereas benzylic substrates may simultaneously proceed along both inner- and outer-sphere CO<sub>2</sub> insertion ...