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Lindner S.,John Innes Center | Lindner S.,Karlsruhe Institute of Technology | Geu-Flores F.,Karlsruhe Institute of Technology | Brase S.,Karlsruhe Institute of Technology | And 3 more authors.
Chemistry and Biology | Year: 2014

The core structure of the iridoid monoterpenes is formed by a unique cyclization reaction. The enzyme that catalyzes this reaction, iridoid synthase, is mechanistically distinct from other terpene cyclases. Here we describe the synthesis of two substrate analogs to probe the mechanism of iridoid synthase. Enzymatic assay of these substrate analogs along with clues from the product profile of the native substrate strongly suggest that iridoid synthase utilizes a Michael reaction to achieve cyclization. This improved mechanistic understanding will facilitate the exploitation of the potential of iridoid synthase to synthesize new cyclic compounds from nonnatural substrates. © 2014 Elsevier Ltd. All rights reserved.


Hagendorn T.,Karlsruhe Institute of Technology | Brase S.,Karlsruhe Institute of Technology | Brase S.,Institute of Toxicology and Genetics
RSC Advances | Year: 2014

The current paper describes a new synthesis of heteroatom-substituted cyclooctynes. By using the Nicholas reaction we managed to design a concise synthesis that only uses three steps to build the eight-membered ring. It was also possible to functionalize said alkyne with a fluorophore. This journal is © the Partner Organisations 2014.


Li J.,Institute of Toxicology and Genetics | Li J.,University of Heidelberg | Kleintschek T.,Institute of Functional Interfaces | Rieder A.,Institute of Functional Interfaces | And 6 more authors.
ACS Applied Materials and Interfaces | Year: 2013

Biofilms represent a fundamental problem in environmental biology, water technology, food hygiene as well as in medical and technical systems. Recently introduced slippery liquid-infused porous surface (SLIPS) showed great promise for preventing biofilm formation owing to the low surface energy of such surface in combination with its self-cleaning properties. In this study we demonstrated a novel hydrophobic liquid-infused porous poly(butyl methacrylate-co-ethylene dimethacrylate) surface (slippery BMA-EDMA) with bacteria-resistance in BM2 mineral medium and long-term stability in aqueous environments. We showed that the slippery BMA-EDMA surface prevents biofilm formation of different strains of opportunistic pathogen Pseudomonas aeruginosa for at least up to 7 days in low nutrient medium. Only ∼1.8% of the slippery surface was covered by the environmental P. aeruginosa PA49 strain under investigation. In uncoated glass controls the coverage of surfaces reached ∼55% under the same conditions. However, in high nutrient medium, more relevant to physiological conditions, the biofilm formation on the slippery surface turned out to be highly dependent on the bacterial strain. Although the slippery surface could prevent biofilm formation of most of the P. aeruginosa strains tested (∼1% surface coverage), the multiresistant P. aeruginosa strain isolated from wastewater was able to cover up to 12% of the surface during 7 days of incubation. RAPD-PCR analysis of the used P. aeruginosa strains demonstrated their high genome variability, which might be responsible for their difference in biofilm formation on the slippery BMA-EDMA surface. The results show that although the slippery BMA-EDMA surface has a great potential against biofilm formation, the generality of its bacteria resistant properties is still to be improved. © 2013 American Chemical Society.


Yan W.,Fritz Haber Institute | Yan W.,CAS Beijing National Laboratory for Molecular | Seifermann S.M.,CYNORA GmbH | Pierrat P.,University of Strasbourg | And 2 more authors.
Organic and Biomolecular Chemistry | Year: 2015

Highly functionalized fullerenes can be efficiently constructed by various techniques. However, the challenge is to synthesize highly symmetrical fullerenes. Recently, a number of X-ray structures have been disclosed showing the high symmetry of substituted fullerenes. By reviewing the major types of multi functionalized fullerenes through selected examples with a link to the structural assignments, the authors intend to give a concise overview to the specialist in the field and to provide the non-specialist with a tool box of possibilities. ©The Royal Society of Chemistry 2015.


Seifermann S.M.,Karlsruhe Institute of Technology | Muller T.,Karlsruhe Institute of Technology | Brase S.,Karlsruhe Institute of Technology | Brase S.,Institute of Toxicology and Genetics
European Journal of Organic Chemistry | Year: 2013

The synthesis of four new bis(oxazoline) (BOX) derivatives bearing two additional coordination sites at the 4,4′-positions is presented. As these BOX scaffolds contain an unsubstituted methylene bridge, they should be capable of forming neutral metal complexes. Thus, these molecules are very interesting ligands for bifunctional catalysis. In addition, one BOX scaffold bearing two azide moieties was successfully employed in copper-free 1,3-dipolar cycloaddition reactions. The resulting products have yet again high ligand potential. The efficient synthesis of bis(oxazoline) (BOX) derivatives bearing two additional coordination sites at the 4,4′-positions is presented. As these BOX scaffolds contain an unsubstituted methylene bridge, they should be capable of forming neutral metal complexes. Thus, these molecules are very interesting ligands for bifunctional catalysis. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Hafner A.,Karlsruhe Institute of Technology | Fischer T.S.,Karlsruhe Institute of Technology | Brase S.,Karlsruhe Institute of Technology | Brase S.,Institute of Toxicology and Genetics
European Journal of Organic Chemistry | Year: 2013

A modified Julia-Kocienski protocol was investigated for the synthesis of CF3-substituted terminal olefins. By employing a simple one-step procedure, aldehydes were converted into the corresponding CF 3-substituted olefins using 2-[(2,2,2-trifluoroethyl)sulfonyl] benzo[d]thiazole as the trifluoromethylation agent. This sulfone was prepared on a gram scale in two steps from inexpensive and commercially available trifluoroethanol. The Julia-Kocienski olefination tolerated various functional groups, and the trifluoromethylated olefins were obtained in good yields. However, the E/Z selectivity was strongly substrate dependent, and only moderate selectivities could be achieved. By employing a two-step procedure, it was possible to synthesize an α-trifluoromethyl-substituted sulfone on a gram scale by starting from inexpensive and commercially available trifluoroethanol. This substrate could then be used in a modified Julia-Kocienski olefination to prepare trifluoromethyl-substituted terminal olefins). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Hagendorn T.,Karlsruhe Institute of Technology | Brase S.,Karlsruhe Institute of Technology | Brase S.,Institute of Toxicology and Genetics
European Journal of Organic Chemistry | Year: 2014

A new silver-free synthesis for cyclooctynol is introduced. The obtained alcohol was further functionalized by a Mitsunobu reaction to give an assortment of imide and phenol derivatives. It was also possible to further functionalize the cyclooctyne by treatment with a fluorescein dye. As an interesting application, we used a cyclooctyne-maleimide conjugate as an azide-thiol crosslinker. A new synthesis for cyclooct-2-ynol is presented that does not employ silver salts. The obtained alcohol was further functionalized by Mitsunobu chemistry to afford new cyclooctynes. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Monnereau L.,Fritz Haber Institute | Nieger M.,University of Helsinki | Muller T.,Fritz Haber Institute | Brase S.,Fritz Haber Institute | Brase S.,Institute of Toxicology and Genetics
Advanced Functional Materials | Year: 2014

The efficient syntheses of tetrakis(thiophenol)methane and of a new poly(disulfide) hyper-crosslinked polymer based on the former monomer are described. Controlled de-polymerization as well as surface post- functionalization are successfully conducted on this novel material. Direct prove of post-functionalization is obtained through solid-state fluorescence emission spectroscopy, and the number of unreacted thiol-functions on the surface of the polymeric material is indirectly quantified by de-polymerization of the post-functionalized material. The efficient generation of a hyper-crosslinked poly(disulfide) is described. After high yielding synthesis of the monomer tetrakis-(4-thiylphenyl)methane, the polymeric material is obtained in excellent yield under mild reaction conditions. Combination of controlled de-polymerization under bio-compatible conditions and postfunctionalization gives access to the number of free termini at the surface. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Muller T.,The Innovation Group | Brase S.,Fritz Haber Institute | Brase S.,Institute of Toxicology and Genetics
RSC Advances | Year: 2014

The preference of material chemists for specific organic building blocks for the generation of porous crystalline or amorphous covalently linked materials or supramolecular architectures, held together by hydrogen bonding or metal coordination, is reviewed. Tetrakisphenylmethane and adamantane cores are readily to hand and easily endowed with various functional groups suitable for network generation. Besides, these structures fulfil the stiffness requirements in order to generate permanently porous frameworks. By reviewing the major types of porous networks through selected examples, the authors intend to give a concise overview to the specialist in the field and to provide the non-specialist with a tool box of possibilities. © The Royal Society of Chemistry 2014.


Hafner A.,Fritz Haber Institute | Jung N.,Institute of Toxicology and Genetics | Brase S.,Fritz Haber Institute | Brase S.,Institute of Toxicology and Genetics
Synthesis (Germany) | Year: 2014

Direct perfluoroalkylation reactions, especially trifluoromethylations of organic substrates, are of particular importance in modern organic chemistry as they allow rapid access to perfluoroalkylated molecules. In contrast to common metal-mediated perfluoroalkylations, recently developed silver-mediated perfluoroalkylation protocols offer the opportunity for orthogonal introduction of fluorine containing groups in organic compounds. This review gathers recent progress on silver-mediated perfluoroalkylation reactions and gives an overview over efficient syntheses, properties, and reactivity of perfluoroorganosilver(I) compounds. In addition, cooperative effects with copper-mediated processes are discussed. 1 Introduction 2 Syntheses and Properties of Perfluoroorganosilver Compounds 3 Silver-Mediated Perfluoroalkylations 3.1 Perfluoroorganosilver Compounds in Copper-Mediated Perfluoroalkylations 3.2 Perfluoroorganosilver Compounds as Precursors for Radicals 3.3 Perfluoroorganosilver Compounds as Nucleophilic Reagents 3.4 Silver-Catalyzed Perfluoroalkylations 4 Conclusion and Outlook. ©Georg Thieme Verlag Stuttgart New York.

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