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Patrick M M Shelton, Caroline E Weller, Champak Chatterjee
The C-terminal selective electrophilic activation of polypeptides is essential for site-specific peptide mod-ification and conjugation techniques such as Native Chemi-cal Ligation (NCL). Peptide C-terminal α-thioesters are par-ticularly valuable precursors for NCL, due to their hydrolytic stability in aqueous buffers and reactivity toward thiol nucle-ophiles. The synthesis of peptide α-thioesters, however, re-quires harsh acidic conditions or complex chemical manipu-lations, which ultimately limits their functional group com-patibility and broad utility...
February 23, 2017: Journal of the American Chemical Society
Alois Fürstner, Wouter Debrouwer
The gold acetylide complex 20 endowed with a biaryl backbone provides opportunities for a study on the formation and fate of gold vinylidenes. While the formyl group in 20 per se is not sufficiently electrophilic to get attacked by the acetylide in proximity, its activation with TBSOTf at low temperature triggered instantaneous formation of a gold vinylidene (21). This metastable species evolved into the cationic gold carbene complex 22 bearing a phenanthrene unit and a hydroxyl group at the aurated center; the recorded data suggest that this product might be better viewed as an acylgold species protonated by triflic acid...
February 23, 2017: Chemistry: a European Journal
S Yogendra, F Hennersdorf, A Bauzá, A Frontera, R Fischer, J J Weigand
A carbodiphosphorane ((Ph3P)2C) mediated synthesis of the first triflyloxyphosphonium dication (12+) bearing two electrophilic sites is presented. Depending on the nucleophile, 12+ reacts selectively either at the sulfur atom of the triflyloxy moiety or at the directly attached phosphorus atom. In substitution reactions at the phosphorus atom the triflyloxy moiety serves as a leaving group and enables the synthesis of rare examples of pseudo-halophosphonium dications.
February 23, 2017: Chemical Communications: Chem Comm
Christian Slawik, Christiane Rickmeyer, Martin Brehm, Alexander Böhme, Gerrit Schüürmann
Glutathione (GSH) has so far been considered to facilitate detoxification of soft organic electrophiles through covalent binding at its cysteine (Cys) thiol group, followed by stepwise catalyzed degradation and eventual elimination along the mercapturic acid pathway. Here we show that in contrast to expectation from HSAB theory, Michael-acceptor ketones, aldehydes and esters may form also single, double and triple adducts with GSH involving β-carbon attack at the much harder N-terminus of the γ-glutamyl (Glu) unit of GSH...
February 22, 2017: Environmental Science & Technology
Xun Hu, Shengjuan Jiang, Liping Wu, Shuai Wang, Chun-Zhu Li
Direct conversion of biomass-derived xylose and furfural into levulinic acid, a platform molecule, via acid-catalysis has been accomplished for the first time in dimethoxymethane/methanol. Dimethoxymethane acted as an electrophile to transform furfural into 5-hydroxymethylfurfural (HMF). Methanol suppressed both the polymerisation of the sugars/furans and the Aldol condensation of levulinic acid/ester.
February 22, 2017: Chemical Communications: Chem Comm
Chao Wu, Xiufang Hou, Yuheng Zheng, Pengfei Li, Dongmei Lu
We carried out a survey of the relative reactivity of a collection of 91 neutral boryl radicals using density functional calculations. Their reactivities were characterized by four indices, i.e., the global electrophilicity, global nucleophilicity, local electrophilicity, and local nucleophilicity. Particularly, the global electrophilicity and nucleophilicity indices span over a moderately wider range than those of carbon radicals, indicating their potentially broader reactivity. Thus boryl radicals may be utilized in electrophilic radical reactions, while traditionally they are only considered for nucleophilic radical reactions...
February 22, 2017: Journal of Organic Chemistry
Megan L Matthews, Lin He, Benjamin D Horning, Erika J Olson, Bruno E Correia, John R Yates, Philip E Dawson, Benjamin F Cravatt
Activity-based protein profiling (ABPP) serves as a chemical proteomic platform to discover and characterize functional amino acids in proteins on the basis of their enhanced reactivity towards small-molecule probes. This approach, to date, has mainly targeted nucleophilic functional groups, such as the side chains of serine and cysteine, using electrophilic probes. Here we show that 'reverse-polarity' (RP)-ABPP using clickable, nucleophilic hydrazine probes can capture and identify protein-bound electrophiles in cells...
March 2017: Nature Chemistry
Han Zhou, Yan Peng, Aneetha Halikhedkar, Pusheng Fan, David R Janero, Ganesh A Thakur, Richard Warren Mercier, Xin Sun, Xiaoyu Ma, Alexandros Makriyannis
Cannabinoid receptor 2 (CB2R)-dependent signaling is implicated in neuronal physiology and immune surveillance by brain microglia. Selective CB2R agonists hold therapeutic promise for inflammatory and other neurological disorders. Information on human CB2R (hCB2R) ligand-binding and functional domains is needed to inform the rational design and optimization of candidate drug-like hCB2R agonists. Prior demonstration that hCB2R transmembrane helix 2 (TMH2) cysteine C2.59(89) reacts with small-molecule methanethiosulfonates showed that this cysteine residue is accessible to sulfhydryl derivatization reagents...
February 21, 2017: ACS Chemical Neuroscience
Jan Nickolaus, Dominik A Imbrich, Simon H Schlindwein, Adrian H Geyer, Martin Nieger, Dietrich Gudat
The outcome of the reduction of [(cod)PtX2] (X = Cl, Br; cod = 1,5-cyclooctadiene) with N-heterocyclic phosphenium hydrides (R)NHP-H depends strongly on the steric demand of the N-aryl group R and the nature of X. Reaction of [(cod)PtCl2] with (Dipp)NHP-H featuring bulky N-Dipp groups produced an unprecedented monomeric phosphenium metal(0) halide [((Dipp)NHP)((Dipp)NHP-H)PtCl] stabilized by a single phosphine ligand. The phosphenium unit exhibits a pyramidal coordination geometry at the phosphorus atom and may according to DFT calculations be classified as a Z-type ligand...
February 20, 2017: Inorganic Chemistry
Lucía González-Perilli, Mauricio Mastrogiovanni, Denise de Castro Fernandes, Homero Rubbo, Francisco Laurindo, Andrés Trostchansky
BACKGROUND: Nitroarachidonic acid (NO2AA) exhibits pleiotropic anti-inflammatory actions in a variety of cell types. We have recently shown that NO2AA inhibits phagocytic NADPH oxidase 2 (NOX2) by preventing the formation of the active complex. Recent work indicates the participation of protein disulfide isomerase (PDI) activity in NOX2 activation. Cysteine (Cys) residues at PDI active sites could be targets for NO2AA- nitroalkylation regulating PDI activity which could explain our previous observation...
February 12, 2017: Biochimica et Biophysica Acta
Virendra R Mishra, Nagaiyan Sekar
Using density functional theory approach, the trend in photostability of fluorescent coumarin laser dyes were investigated with the help global reactivity descriptors. The effect of different basis sets on global reactivity descriptors i.e. electrophilicity index (ω) is studied. The local reactivity descriptors such as Fukui function, local softness and local electrophilicity index have been used to understand the reactive site in the molecule. Photodegradation mechanism of fluorescent coumarin laser dyes in presence of singlet oxygen is explained using density functional theory...
February 17, 2017: Journal of Fluorescence
Jiapian Huang, Yangfei Huang, Tao Wang, Qin Huang, Zhihua Wang, Zhiyuan Chen
A microwave-assisted, Cp*Co(III)-catalyzed direct C-H activation/double C-N bond formation reaction of simple NH-sulfoximines with 1,4,2-dioxazol-5-ones to produce diverse thiadiazine-1-oxides is reported. The reaction tolerates a broad range of functional groups under external oxidant-free conditions and only releases CO2 and H2O as the sole byproducts. The preliminary mechanistic studies revealed an electrophilic metalation pathway is likely involved in the reaction.
February 17, 2017: Organic Letters
Naganaboina Naveen, Rengarajan Balamurugan
A facile method for the synthesis of α-fluoro-β-hydroxy ketones/α-fluoro-ynols from tertiary propargyl alcohols under electrophilic fluorination conditions using F-TEDA-BF4 has been presented. The products bear pharmaceutically important α-fluoro ketone, gem-diaryl and fluorohydrin moieties in the same molecule. Interestingly, this catalyst free protocol results in monofluorination.
February 17, 2017: Organic & Biomolecular Chemistry
Kang-Lok Lee, Ji-Sun Yoo, Gyeong-Seok Oh, Atul K Singh, Jung-Hye Roe
Bacteria in natural habitats are exposed to myriad redox-active compounds (RACs), which include producers of reactive oxygen species (ROS) and reactive electrophile species (RES) that alkylate or oxidize thiols. RACs can induce oxidative stress in cells and activate response pathways by modulating the activity of sensitive regulators. However, the effect of a certain compound on the cell has been investigated primarily with respect to a specific regulatory pathway. Since a single compound can exert multiple chemical effects in the cell, its effect can be better understood by time-course monitoring of multiple sensitive regulatory pathways that the compound induces...
2017: Frontiers in Microbiology
Kai Yin, Fei Li, Ying Wang, Qunying He, Yongxiu Deng, Shuo Chen, Chengbin Liu
Acesulfame has attracted much attention due to its wide application, environmental persistence and potential safety risk of transformation products (TPs). Little information is known on acesulfame transformation in the presence of oxidants/disinfectants. The acesulfame oxidation by permanganate (Mn(VII)) in water under environmentally relevant conditions was systematically evaluated. The pH of water showed negligible influence in acesulfame oxidation. Inorganic ligand (pyrophosphate) exhibited insignificant effect whereas organic ligands (oxalate, ethylene diamine tetraacetic acid, and humic acid) exerted obvious suppression on acesulfame oxidation...
February 9, 2017: Journal of Hazardous Materials
Arjun Sham, Khaled Moustafa, Shamma Al-Shamisi, Sofyan Alyan, Rabah Iratni, Synan AbuQamar
The WRKY33 transcription factor was reported for resistance to the necrotrophic fungus Botrytis cinerea. Using microarray-based analysis, we compared Arabidopsis WRKY33 overexpressing lines and wrky33 mutant that showed altered susceptibility to B. cinerea with their corresponding wild-type plants. In the wild-type, about 1660 genes (7% of the transcriptome) were induced and 1054 genes (5% of the transcriptome) were repressed at least twofold at early stages of inoculation with B. cinerea, confirming previous data of the contribution of these genes in B...
2017: PloS One
Bo-Liang Zhao, Da-Ming Du
A novel bifunctional squaramide-catalyzed one-pot electrophilic trifluoromethylthiolation-sulfur-Michael/aldol cascade reaction for the construction of CF3S-containing spiro-cyclopentanone-thiochromanes was developed. This convenient, one-pot cascade reaction serves as a powerful tool for the enantioselective construction of potential bioactive spiro-cyclopentanone-thiochromanes, which have one quaternary stereocenter containing a CF3S group and three contiguous stereocenters including one spiro all-carbon quaternary center, in moderate to good yields with excellent stereoselectivities (up to 15:1 dr, >99% ee)...
February 15, 2017: Organic Letters
Stef Vanhaecht, Thomas Quanten, Tatjana N Parac-Vogt
A new postfunctionalization method was developed for the Anderson-type POM based on a nucleophilic substitution reaction occurring at an electrophilic sp(3) hybridized carbon localized on the hybrid POM. Using this method, several types of different nucleophiles including primary and secondary amines, carboxylates, and thiolates were efficiently coupled to a chloride-functionalized Anderson-type POM in high yields and purity. The heterogeneous acetonitrile-Na2CO3 conditions were found to be superior over other bases and solvents for the coupling of amines and thiolates to the chloride-functionalized POM...
February 15, 2017: Inorganic Chemistry
Feng Shen, Panpan Zhang, Long Lu, Qilong Shen
A shelf-stable and easily convertible reagent for the preparation of diversified fluoroalkylthiolated compounds, [[(ethoxycarbonyl)difluoromethyl]thio]phthalimide, was developed. [[(Ethoxycarbonyl)difluoromethyl]thio]phthalimide is an efficient electrophilic fluoroallylthiolating reagent that reacted with electron-rich heteroarenes/arenes, β-ketoesters, oxindoles, benzofuranones, and thiols. More importantly, the ethoxycarbonyl group of the resulting fluoroalkylthiolated compounds could be easily converted into various other functional groups such as chloride, alkynyl, hydrocarbonyl, carbomoyl, hydromethyl, or heteroaryl groups...
February 15, 2017: Organic Letters
Nenad R Filipović, Hana Elshaflu, Sonja Grubišić, Ljiljana S Jovanović, Marko Rodić, Irena Novaković, Aleksandar Malešević, Ivana S Djordjević, Haidong Li, Nešo Šojić, Aleksandar Marinković, Tamara R Todorović
The first Co(iii) complexes with (1,3-selenazol-2-yl)hydrazones as an unexplored class of ligands were prepared and characterized by NMR spectroscopy and X-ray diffraction analysis. The novel ligands act as NNN tridentate chelators forming octahedral Co(iii) complexes. The impact of structural changes on ligands' periphery as well as that of isosteric replacement of sulphur with selenium on the electrochemical and electronic absorption features of complexes are explored. To support the experimental data, density functional theory (DFT) calculations were also conducted...
February 15, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
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