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Sachin Asaram Ingale, Peter Leonard, Frank Seela
Glycosylation of non-functionalized 6-chloro-7-deazapurine with commercial available 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose (45% yield) followed by amination and deprotection gave tubercidin in only two steps. Similar conditions applied for the synthesis of 7-deazaguanosine employing pivaloylated 2-amino-6-chloro-7-deazapurine gave 18% glycosylation yield. Less bulky isobutyryl or acetyl protected amino group directed the glycosylation toward the exocyclic amino substituent. 7-Halogenated intermediates were glycosylated followed by dehalogenation to overcome the low glycosylation yield in the synthesis of 7-deazaguanosine...
June 18, 2018: Journal of Organic Chemistry
Matthias Lischka, Georg S Michelitsch, Natalia Martsinovich, Johanna Eichhorn, Atena Rastgoo-Lahrood, Thomas Strunskus, Rochus Breuer, Karsten Reuter, Michael Schmittel, Markus Lackinger
Even though the surface-assisted dehalogenative coupling constitutes the most abundant protocol in on-surface synthesis, its full potential will only become visible if selectivity issues with polybrominated precursors are comprehensively understood, opening new venues for both organometallic self-assembly and on-surface polymerization. Using the 3,3',5,5'-tetrabromo-2,2',4,4',6,6'-hexafluorobiphenyl (Br4F6BP) at Ag(111), we demonstrate a remote site-selective functionalization at room temperature and a marked temperature difference in double- vs...
June 15, 2018: Nanoscale
Weizhao Yin, Jing Ai, Li-Zhi Huang, Dominique J Tobler, Hans Christian Bruun Hansen
Layered FeII-FeIII hydroxide chloride (chloride green rust, GRCl) has high reactivity towards reducible pollutants such as chlorinated solvents. However, this reactive solid is prone to dissolution, and hence loss of reactivity during storage and handling. In this study, adsorption of silicate (Si) to GRCl was tested for its ability to minimize GRCl dissolution and to inhibit reduction of carbon tetrachloride (CT). Silicate adsorbed with high affinity to GRCl yielding a sorption maximum of 0.026 g Si per g GRCl...
June 15, 2018: Environmental Science & Technology
Kyle F Biegasiewicz, Simon J Cooper, Megan A Emmanuel, David C Miller, Todd K Hyster
Strategies that provide enzymes with the ability to catalyse non-natural reactions are of considerable synthetic value. Photoredox catalysis has proved adept at expanding the synthetic repertoire of existing catalytic platforms, yet, in the realm of biocatalysis it has primarily been used for cofactor regeneration. Here we show that photoredox catalysts can be used to enable new catalytic function in nicotinamide-dependent enzymes. Under visible-light irradiation, xanthene-based photocatalysts enable a double-bond reductase to catalyse an enantioselective deacetoxylation...
June 11, 2018: Nature Chemistry
Dominique Türkowsky, Patrick Lohmann, Marie Mühlenbrink, Torsten Schubert, Lorenz Adrian, Tobias Goris, Nico Jehmlich, Martin von Bergen
Thermal proteome profiling (TPP) is increasingly applied in eukaryotes to investigate protein-ligand binding through protein melting curve shifts induced by the presence of a ligand. In anaerobic bacteria, identification of protein-substrate interactions is a major challenge. We applied TPP to Sulfurospirillum multivorans, which is able to use trichloroethene as electron acceptor for growth, to investigate the interaction of its tetrachloroethene reductive dehalogenase PceA with trichloroethene. Several modifications in the protocol (e...
June 4, 2018: Journal of Proteomics
Dayyabu Shehu, Zazali Alias
Glutathione S-transferases (GSTs) are a family of enzymes that function in the detoxification of variety of electrophilic substrates. In the present work, we report a novel zeta-like GST (designated as KKSG9) from the biphenyl/polychlorobiphenyl degrading organism Acidovorax sp. KKS102. KKSG9 possessed low sequence similarity but similar biochemical properties to zeta class GSTs. Functional analysis showed that the enzyme exhibits wider substrate specificity compared to most zeta class GSTs by reacting with 1-chloro-2,4-dinitrobenzene (CDNB), p-nitrobenzyl chloride (NBC), ethacrynic acid (EA), hydrogen peroxide, and cumene hydroperoxide...
May 19, 2018: Protein Journal
Wanda Mączka, Małgorzata Grabarczyk, Katarzyna Wińska, Elżbieta Gębarowska, Tomasz Strzała, Marek Durajczyk
The aim of the project was to find new catalysts capable of chlorolactone biotransformation. Three bicyclic chlorolactones with structures possessing one or two methyl groups in their cyclohexane ring were subjected to screening biotransformation using seven bacterial strains and one fungal strain from a salt mine. Three strains of bacteria (Micrococcus luteus Pb10, Micrococcus luteus WSP45, Gordonia alkanivorans Pd25) and one fungal strain (Aspergillus sydowii KGJ10) were able to catalyse hydrolytic dehalogenation of one substrate...
2018: PloS One
Robert Naumann, Florian Lehmann, Martin Goez
We have explored alkyl substitution of the ligands as a means to improve the performance of the title complexes in photoredox catalytic systems that produce synthetically useable amounts of hydrated electrons through photon pooling. Despite generating a superreductant, these electron sources only consume the bioavailable ascorbate and are driven by a green light-emitting diode (LED). The substitutions influence the catalyst activity through the quenching and recombination rates across the micelle-water interface, and the photoionization quantum yield...
May 16, 2018: Chemistry: a European Journal
Abhishek Phatarphekar, Qi Su, Suk Ho Eun, Xin Chen, Steven E Rokita
The ability of iodotyrosine deiodinase to salvage iodide from iodotyrosine has long been recognized as critical for iodide homeostasis and proper thyroid function in vertebrates. The significance of its additional ability to dehalogenate bromo- and chlorotyrosine is less apparent and none of these functions could have been anticipated in invertebrates until recently. Drosophila , as most arthropods, contains a deiodinase homolog encoded by CG6279 , now named condet ( cdt ), with a similar catalytic specificity...
May 15, 2018: Journal of Biological Chemistry
Thiau-Fu Ang, Jonathan Maiangwa, Abu Bakar Salleh, Yahaya M Normi, Thean Chor Leow
The variety of halogenated substances and their derivatives widely used as pesticides, herbicides and other industrial products is of great concern due to the hazardous nature of these compounds owing to their toxicity, and persistent environmental pollution. Therefore, from the viewpoint of environmental technology, the need for environmentally relevant enzymes involved in biodegradation of these pollutants has received a great boost. One result of this great deal of attention has been the identification of environmentally relevant bacteria that produce hydrolytic dehalogenases—key enzymes which are considered cost-effective and eco-friendly in the removal and detoxification of these pollutants...
May 7, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Jingbo Yu, Zikun Hong, Xinjie Yang, Yu Jiang, Zhijiang Jiang, Weike Su
A mechanically-activated chemoselective Heck coupling for the synthesis of 3-vinylindazoles has been developed with the aid of catalytic amounts of TBAB and NaBr as both dehalogenation restrainer and grinding auxiliary. After tuning of the chemical conditions and mechanical parameters, a series of non-activated 3-bromoindazoles and a broad scope of olefins worked well to give the corresponding coupling products in good to excellent yields. A further application of this protocol was performed in a two-step mechanochemical Heck/Migita cross coupling, which provided a highly efficient route for the synthesis of axitinib...
2018: Beilstein Journal of Organic Chemistry
Linlin Yang, Xu Jing, Bowen An, Cheng He, Yang Yang, Chunying Duan
By synergistic combination of multicomponent self-assembly and template-directed approaches, triply interlocked metal organic catenanes that consist of two isolated chirally identical tetrahedrons were constructed and stabilized as thermodynamic minima. In the presence of suitable template anions, the structural conversion from the isolated tetrahedral conformers into locked catenanes occurred via the cleavage of an intrinsically reversible coordination bond in each of the tetrahedrons, followed by the reengineering and interlocking of two fragments with the regeneration of the broken coordination bonds...
January 28, 2018: Chemical Science
Dominique Türkowsky, Jens Esken, Tobias Goris, Torsten Schubert, Gabriele Diekert, Nico Jehmlich, Martin von Bergen
Organohalide respiration (OHR), comprising the reductive dehalogenation of halogenated organic compounds, is subject to a unique memory effect and long-term transcriptional downregulation of the involved genes in Sulfurospirillum multivorans. Gene expression ceases slowly over approximately 100 generations in the absence of tetrachloroethene (PCE). However, the molecular mechanisms of this regulation process are not understood. We show here that Sulfurospirillum halorespirans undergoes the same type of regulation when cultivated without chlorinated ethenes for a long period of time...
June 15, 2018: Journal of Proteomics
Wei Zhang, Wei Wu, Yu Long, Fushan Wang, Jiantai Ma
The design of lower-cost alternative heterogeneous catalysts for the hydrogenation of halogenated nitrobenzenes using green method to synthesize the corresponding anilines is highly desirable. In this study, Ag was incorporated into the Co-MOFs during the growing process (Co-Ag(n)-MOFs), and then followed the carbothermal reduction process without any additional procedures, we synthesized a series of Co-Ag(n)@NCs. The self-supported catalysts exhibited excellent and stable catalytic performances for the chemoselective hydrogenation of halogenated nitrobenzenes without obvious dehalogenation...
July 15, 2018: Journal of Colloid and Interface Science
Christof Holliger, Ivonne Nijenhuis
No abstract text is available yet for this article.
June 1, 2018: FEMS Microbiology Ecology
Steffi Franke, Steffen Kümmel, Ivonne Nijenhuis
RATIONALE: Halogenated benzoic acids occur in the environment due to their widespread agricultural and pharmaceutical use. Compound-specific stable isotope analysis (CSIA) has developed over the last decades for investigation of in situ transformation and reaction mechanisms of environmental pollutants amenable by gas chromatography (GC). As polar compounds are unsuitable for GC analysis we developed a method to perform liquid chromatography (LC)/CSIA for halogenated benzoates. METHODS: LC/isotope ratio mass spectrometry (IRMS) utilizing a LC-Surveyor pump coupled to a MAT 253 isotope ratio mass spectrometer via a LC-Isolink interface was applied...
June 15, 2018: Rapid Communications in Mass Spectrometry: RCM
Zsolt Majzik, Niko Pavliček, Manuel Vilas-Varela, Dolores Pérez, Nikolaj Moll, Enrique Guitián, Gerhard Meyer, Diego Peña, Leo Gross
Antiaromatic and open-shell molecules are attractive because of their distinct electronic and magnetic behaviour. However, their increased reactivity creates a challenge for probing their properties. Here, we describe the on-surface and in-solution generation and characterisation of a highly reactive antiaromatic molecule: indeno[1,2-b]fluorene (IF). In solution, we generated IF by KI-induced dehalogenation of a dibromo-substituted precursor molecule and found that IF survives for minutes at ambient conditions...
March 22, 2018: Nature Communications
Xi-Hui Xu, Xiao-Mei Liu, Long Zhang, Yang Mu, Xu-Yuan Zhu, Jing-Ya Fang, Shun-Peng Li, Jian-Dong Jiang
Although bioaugmentation of pollutant-contaminated sites is a great concern, there are few reports on the relationships among indigenous microbial consortia, exogenous inocula, and pollutants in a bioaugmentation process. In this study, bioaugmentation with Pseudochrobactrum sp. BSQ1 and Massilia sp. BLM18, which can hydrolytically and reductively dehalogenate chlorothalonil (TPN), respectively, was studied for its ability to remove TPN from soil; the alteration of the soil microbial community during the bioaugmentation process was investigated...
June 5, 2018: Journal of Hazardous Materials
Xuefeng Guo, Chao Yu, Zhouyang Yin, Shouheng Sun, Christopher T Seto
Ni30 Pd70 nanoparticles supported on nitrogen-doped graphene (NG) acts as a catalyst for the hydrodehalogenation of halogenated aromatics under mild reaction conditions. It reduces mono- or dichloroarenes to the corresponding dehalogenated arenes in >90 % yield in 10 % aqueous isopropanol solvent at or below 50 °C within 5 h. Tests on a variety of substrates containing various functional groups show that the catalyst is selective for reduction of C-Cl and C-Br bonds. In addition, this catalyst completely hydrodehalogenates high-concentration solutions of dioxin, polychlorinated biphenyls, chloroaromatic constituents of the defoliant agent orange, and polybrominated diphenyl ethers in 12 h...
March 14, 2018: ChemSusChem
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