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  • 1.
    Görbe, Tamás
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Löfgren, Johanna
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Oschmann, Michael
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    S. Humble, Maria
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Transesterification of tert-Alcohols by Engineered Candida antarctica Lipase AManuscript (preprint) (Other academic)
  • 2.
    Löfgren, Johanna
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Görbe, Tamás
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Oschmann, Michael
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Svedendahl Humble, Maria
    Bäckvall, Jan-E
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Transesterification of a Tertiary Alcohol by Engineered Candida antarctica Lipase A2019In: ChemBioChem (Print), ISSN 1439-4227, E-ISSN 1439-7633, Vol. 20, no 11, p. 1438-1443Article in journal (Refereed)
    Abstract [en]

    Tertiary alcohols are known to be challenging substrates for applications in asymmetric synthesis due to their complexity and steric hinderance. The occurrence of tertiary alcohols and their esters in nature indicates the presence of natural biocatalytic synthetic routes for their preparation. Lipase A from Candida antarctica (CalA) is a hydrolase that has previously been shown to catalyze the transesterification of racemic 2-phenylbut-3-yn-2-ol at a low rate. In this work, the activity of that enzyme was improved by protein engineering through a semi-rational design strategy. An enzyme library was created and screened for transesterification activity towards racemic 2-phenylbut-3-yn-2-ol in an organic solvent. One successful enzyme variant (L367G) showed a tenfold increased reaction rate compared to the wild-type enzyme, while maintaining a high enantioselectivity.

  • 3.
    Olsén, Peter
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Oschmann, Michael
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of highly functional carbamates through ring-opening of cyclic carbonates with unprotected alpha-amino acids in water2018In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 20, no 2, p. 469-475Article in journal (Refereed)
    Abstract [en]

    The present work shows that it is possible to ring-open cyclic carbonates with unprotected amino acids in water. Fine tuning of the reaction parameters made it possible to suppress the degree of hydrolysis in relation to aminolysis. This enabled the synthesis of functionally dense carbamates containing alkenes, carboxylic acids, alcohols and thiols after short reaction times at room temperature. When Glycine was used as the nucleophile in the ring-opening with four different five membered cyclic carbonates, containing a plethora of functional groups, the corresponding carbamates could be obtained in excellent yields (> 90%) without the need for any further purification. Furthermore, the orthogonality of the transformation was explored through ring-opening of divinylenecarbonate with unprotected amino acids equipped with nucleophilic side chains, such as serine and cysteine. In these cases the reaction selectively produced the desired carbamate, in 70 and 50% yield respectively. The synthetic design provides an inexpensive and scalable protocol towards highly functionalized building blocks that are envisioned to find applications in both the small and macromolecular arena.

  • 4.
    Oschmann, Michael
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Placais, Clotilde
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nagendiran, Anuja
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient 1,3-Oxazolidin-2-one Synthesis through Heterogeneous Pd-II-Catalyzed Intramolecular Hydroamination of Propargylic Carbamates2019In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 25, no 25, p. 6295-6299Article in journal (Refereed)
    Abstract [en]

    Herein, we present an operationally simple protocol for the cycloisomerization of propargylic carbamates in which a heterogeneous catalyst consisting of Pd species immobilized on amino-functionalized siliceous mesocellular foam (Pd-II-AmP-MCF) is used. This Pd nanocatalyst displayed high efficiency at low catalyst loading and reaction temperatures, which allowed for the efficient and mild synthesis of a wide range of 1,3-oxazolidin-2-one derivatives and related compounds. Moreover, it proved possible to re-use the Pd nanocatalyst for several reactions, although a gradual decrease in activity was observed in the subsequent cycles.

  • 5.
    Schmitz, Alexander J.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. RWTH Aachen, Germany.
    Ricke, Alexander
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Oschmann, Michael
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Convenient Access to Chiral Cyclobutanes with Three Contiguous Stereocenters from Verbenone by Directed C(sp(3))-H arylation2019In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 25, no 20, p. 5154-5157Article in journal (Refereed)
    Abstract [en]

    This work demonstrates how a series of complex, chiral cyclobutane derivatives can be accessed in four steps from the terpene verbenone through the application of a directed C-H functionalization approach. The developed synthetic route involved an 8-aminoquinoline-directed C(sp(3))-H arylation as the key step, and this reaction could be carried out with a wide range of aryl and heteroaryl iodides to furnish a variety of cyclobutane products with three contiguous stereocenters. Moreover, it was shown that the 8-aminoquinoline auxiliary could be effectively removed from the cyclobutane derivatives using an ozonolysis-based cleavage method.

  • 6.
    Shatskiy, Andrey
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bardin, Andrey A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Oschmann, Michael
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Matheu, Roc
    Benet-Buchholz, Jordi
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kärkäs, Markus D.
    Johnston, Eric
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Gimbert-Suriñach, Carolina
    Llobet, Antoni
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Electrochemically Driven Water Oxidation by a Highly Active Ruthenium-Based Catalyst2019In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 12, no 10, p. 2251-2262Article in journal (Refereed)
    Abstract [en]

    The highly active ruthenium-based water oxidation catalyst [Ru-X(mcbp)(OHn)(py)(2)] [mcbp(2-)=2,6-bis(1-methyl-4-(carboxylate)benzimidazol-2-yl)pyridine; n=2, 1, and 0 for X=II, III, and IV, respectively], can be generated in a mixture of Ru-III and Ru-IV states from either [Ru-II(mcbp)(py)(2)] or [Ru-III(Hmcbp)(py)(2)](2+) precursors. The precursor complexes are isolated and characterized by single-crystal X-ray analysis, NMR, UV/Vis, EPR, and FTIR spectroscopy, ESI-HRMS, and elemental analysis, and their redox properties are studied in detail by electrochemical and spectroscopic methods. Unlike the parent catalyst [Ru(tda) (py)(2)] (tda(2-)=[2,2:6,2-terpyridine]-6,6-dicarboxylate), for which full transformation into the catalytically active species [Ru-IV(tda)(O)(py)(2)] could not be carried out, stoichiometric generation of the catalytically active Ru-aqua complex [Ru-X(mcbp)(OHn)(py)(2)] from the Ru-II precursor was achieved under mild conditions (pH7.0) and short reaction times. The redox properties of the catalyst were studied and its activity for electrocatalytic water oxidation was evaluated, reaching a maximum turnover frequency (TOFmax) of around 40000s(-1) at pH9.0 (from foot-of-the-wave analysis), which is comparable to the activity of the state-of-the-art catalyst [Ru-IV(tda)(O)(py)(2)].

  • 7.
    Verho, Oscar
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pourghasemi Lati, Monireh
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Oschmann, Michael
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    A Two-Step Procedure for the Overall Transamidation of 8-Aminoquinoline Amides Proceeding via the Intermediate N-Acyl-Boc-Carbamates2018In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 83, no 8, p. 4464-4476Article in journal (Refereed)
    Abstract [en]

    Herein a two-step strategy for achieving overall transamidation of 8-aminoquinoline amides has been explored. In this protocol, the 8-aminoquinoline amides were first treated with Boc(2)O and DMAP to form the corresponding N-acyl-Boc-carbamates, which were found to be sufficiently reactive to undergo subsequent aminolysis with different amines in the absence of any additional reagents or catalysts. To demonstrate the utility of this approach, it was applied on a number of 8-aminoquinoline amides from the recent C-H functionalization literature, enabling access to a range of elaborate amide derivatives in good to high yields

  • 8.
    Yuan, Ning
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Guðmundsson, Arnar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Gustafson, Karl
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Oschmann, Michael
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bajnóczi, Éva
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    In Situ XAS Investigation of the Deactivation and Reactivation Mechanisms of a Heterogeneous Palladium(II) catalyst during the Cycloisomerization of Acetylenic Acids2019Manuscript (preprint) (Other academic)
    Abstract [en]

    The cause and mechanism of deactivation of a well-studied heterogeneous palladium(II) catalyst in the intramolecular lactonization of acetylenic acids to γ-alkylidene lactones have been investigated. It was shown that the deactivation was driven by the formation of reduced palladium species following the addition of the base triethylamine. In this work, X-ray absorption spectroscopy (XAS) was used to identify the palladium species and follow their evolution over the course of the reaction. It was also found that the choice of substrates has significant influences on the Pd species under the same reaction conditions. With these insights into the deactivation mechanism derived from XAS, different strategies were tested and illustrated to regain or maintain the active state of the catalyst. This information was further used to develop a new protocol, which can effectively prevent the deactivation of the catalyst and prolong its usage. 

1 - 8 of 8
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