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https://www.readbyqxmd.com/read/28722282/metal-free-nitrile-diboration-through-activation-by-an-electron-rich-diborane
#1
Markus Frick, Elisabeth Kaifer, Hans-Jörg Himmel
Diboration of unsaturated organic compounds is an extremely useful reaction in synthetic chemistry. Herein we report the first diboration of a nitrile by an electron-rich diborane, mediated by an electrophilic borane. The reaction is metal-free, and all reagents are readily available.
July 19, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28722252/efficient-access-to-all-carbon-quaternary-and-tertiary-%C3%AE-functionalized-homoallyl-aldehydes-from-ketones
#2
Vittorio Pace, Laura Castoldi, Eugenia Mazzeo, Marta Rui, Thierry Langer, Wolfgang Holzer
Widely substituted all-carbon quaternary and tertiary α-homoallyl aldehydes are rapidly assembled through a unique synthetic operation from ketones consisting in: 1) C1-homologation; 2) epoxide-aldehyde Lewis acid mediated isomerization and, 3) electrophilic trapping. The synthetic equivalence between a vinyl oxirane and a β,γ-unsaturated aldehyde is the key concept for introducing such a previously undisclosed tactic. Mechanistic studies and labeled experiments suggest the intervention of an aldehyde enolate as the crucial intermediate...
July 19, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28720685/the-loss-of-gstm1-associates-with-kidney-failure-and-heart-failure
#3
Adrienne Tin, Robert Scharpf, Michelle M Estrella, Bing Yu, Megan L Grove, Patricia P Chang, Kunihiro Matsushita, Anna Köttgen, Dan E Arking, Eric Boerwinkle, Thu H Le, Josef Coresh, Morgan E Grams
Glutathione S-transferase mu 1 (GSTM1) encodes an enzyme that catalyzes the conjugation of electrophilic compounds with glutathione to facilitate their degradation or excretion. The loss of one or both copies of GSTM1 is common in many populations and has been associated with CKD progression. With the hypothesis that the loss of GSTM1 is also associated with incident kidney failure and heart failure, we estimated GSTM1 copy number using exome sequencing reads in the Atherosclerosis Risk in Communities (ARIC) Study, a community-based prospective cohort of white and black participants...
July 18, 2017: Journal of the American Society of Nephrology: JASN
https://www.readbyqxmd.com/read/28719844/phosphate-functionalized-4-4-armchair-cnts-as-novel-drug-delivery-systems-for-alendronate-and-etidronate-anti-osteoporosis-drugs
#4
Zahra Nikfar, Zahra Shariatinia
The ability of (4,4)-armchair CNT and its three phosphate functionalized forms (CNT-nH2PO4, n=1-3) were evaluated as novel drug delivery systems (DDSs) for the two commercially well-known anti-osteoporosis drugs namely alendronate (AL) and etidronate (ET). For this purpose, the DFT calculations were accomplished at both B3LYP and B3PW91 levels using 6-31g(d) basis set. The binding energy was increased by increasing number of H2PO4 moieties attached on the CNT with the most negative binding energy was measured for the carrier containing three phosphate groups...
July 8, 2017: Journal of Molecular Graphics & Modelling
https://www.readbyqxmd.com/read/28718624/covalent-enzyme-inhibition-through-fluorosulfate-modification-of-a-non-catalytic-serine-residue
#5
Olugbeminiyi O Fadeyi, Lise R Hoth, Chulho Choi, Xidong Feng, Ariamala Gopalsamy, Erik C Hett, Robert E Kyne, Ralph P Robinson, Lyn H Jones
Irreversible enzyme inhibitors often utilize the reaction of a protein cysteine residue with an appropriately positioned electrophile (an acrylamide for example) in the ligand template. Cysteine residues are not always available for site-specific protein labeling and therefore new approaches are needed to expand the toolkit of appropriate electrophiles that target alternative amino acids. We have previously described the rational targeting of tyrosine residues in the active site of a protein (the mRNA decapping scavenger enzyme, DcpS) using inhibitors armed with sulfonyl fluoride electrophiles that additionally enabled the subsequent development of clickable probe technology to measure drug-target occupancy in live cells...
July 18, 2017: ACS Chemical Biology
https://www.readbyqxmd.com/read/28716990/proof-of-principle-for-a-novel-class-of-antihypertensives-that-target-the-oxidative-activation-of-protein-kinase-g-i%C3%AE
#6
Joseph R Burgoyne, Oleksandra Prysyazhna, Daniel A Richards, Philip Eaton
Arterial hypertension continues to be a major health burden. Development of new antihypertensive drugs that engage vasodilatory mechanisms not harnessed by available therapies offer therapeutic potential. Oxidants induce an interprotein disulfide in protein kinase G Iα (PKG Iα) at C42, which is associated with its targeting and activation, resulting in vasodilation and blood pressure lowering. Consequently, we developed an assay and screened for electrophilic drugs that activate PKG Iα by selectively targeting C42, as such compounds have potential as novel antihypertensives with a mechanism of action that differs from current therapies...
July 17, 2017: Hypertension
https://www.readbyqxmd.com/read/28715212/kinetics-of-electrophilic-alkylations-of-barbiturate-and-thiobarbiturate-anions
#7
Alexander Schade, Ivan Tchernook, Mirko Bauer, Alexander Oehlke, Martin Breugst, Joachim Friedrich, Stefan Spange
Second-order rate constants (k2) of the reactions of various barbiturate anions such as the parent barbiturate, 1,3-dimethylbarbiturate, 2-thiobarbiturate, and 1,3-diethyl-2-thiobarbiturate with diarylcarbenium ions and Michael acceptors have been determined in dimethylsulfoxide solution at 20 °C. The reactivity parameters N and sN of the barbiturate anions were derived from the linear plots of log k2 versus the electrophilicity parameters E of these reference electrophiles, according to the linear-free-energy relationship log k2 (20 °C) = sN (E+N)...
July 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28714686/an-unconventional-redox-cross-claisen-condensation-aromatization-of-4-hydroxyprolines-with-ketones
#8
Mi Tang, Rengwei Sun, Hao Li, Xinhong Yu, Wei Wang
Reaction of α-amino acids particularly prolines and their derivatives with carbonyl compounds via decarboxylative redox process is a viable strategy for synthesis of structurally diverse nitrogen centered heterocyclics. In these processes, the decarboxylation is the essential driving force for the processes. The realization of the redox process without decarboxy-lation may offer an opportunity to explore new reactions. Herein, we report the discovery of an unprecedented redox Claisen type condensation aromatization cascade reaction of 4-substituted 4-hydroxyproline and its esters with unreactive ketones...
July 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28708383/unlocking-reactivity-of-trpb-a-general-biocatalytic-platform-for-synthesis-of-tryptophan-analogs
#9
David K Romney, Javier Murciano-Calles, Jöri Elias Wehrmüller, Frances H Arnold
Derivatives of the amino acid tryptophan (Trp) serve as precursors for the chemical and biological synthesis of complex molecules with a wide range of biological properties. Trp analogs are also valuable as building blocks for medicinal chemistry and as tools for chemical biology. While the enantioselective synthesis of Trp analogs is often lengthy and requires the use of protecting groups, enzymes have the potential to synthesize such products in fewer steps and with the pristine chemo- and stereoselectivity that is a hallmark of biocatalysis...
July 14, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28708088/metal-free-regiodivergent-addition-of-carbon-nucleophiles-to-%C3%AE-%C3%AE-unsaturated-electrophiles
#10
Cédric Spitz, Alain G Giuglio-Tonolo, Thierry Terme, Patrice Vanelle
A mild and metal-free regiodivergent addition of carbon nucleophiles to α,β-unsaturated electrophiles was developed. Total 1,2-regioselectivity was observed in the addition of nitrobenzyl chloride derivative 1 to α,β-unsaturated aldehydes 2 in the presence of TDAE. Moreover, the reaction between p-nitrobenzyl chloride 1a and α,β-unsaturated iminium salts 4 led to the formation of the 1,4-adduct with total regioselectivity.
July 14, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28704055/electrochemical-nickel-catalysis-for-sp-2-sp-3-cross-electrophile-coupling-reactions-of-unactivated-alkyl-halides
#11
Robert J Perkins, Dylan J Pedro, Eric C Hansen
A constant-current electrochemical method for reducing catalytic nickel complexes in sp(2)-sp(3) cross-electrophile coupling reactions has been developed. The electrochemical reduction provides reliable nickel catalyst activation and turnover and offers a tunable parameter for reaction optimization, in contrast to more standard activated metal powder reductants. The electrochemical reactions give yields (i.e., 51-86%) and selectivities as high or superior to those using metal powder reductants and provide access to a wider substrate scope...
July 13, 2017: Organic Letters
https://www.readbyqxmd.com/read/28702642/borata-wittig-olefination-reactions-of-ketones-carboxylic-esters-and-amides-with-bis-pentafluorophenyl-borata-alkene-reagents
#12
Tongdao Wang, Sonja Kohrt, Constantin G Daniliuc, Gerald Kehr, Gerhard Erker
The strongly electrophilic borane derivative amino-CH2CH2CH2-B(C6F5)26 was α-CH deprotonated with LiTMP to give the borata-alkene {[amino-(CH2)2-CH[double bond, length as m-dash]B(C6F5)2(-)][Li(+)]}29 which underwent facile [2 + 2] cycloaddition reactions with benzophenone or fluorenone to yield the respective 1,2-oxaboretanides 11a,b. Compounds 9 and 11 were characterized by the X-ray diffraction. Thermolysis or hydrolysis of compounds 11a,b gave the corresponding borata-Wittig olefination products 12a,b...
July 12, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28700238/regio-and-stereoselective-anti-carbozincation-of-alkynyl-ethers-using-znbr2-toward-z-%C3%AE-zincated-enol-ether-synthesis
#13
Yoshihiro Nishimoto, Kyoungmin Kang, Makoto Yasuda
(Z)-β-Aryloxyalkenylzincs are synthesized stereoselectively via anti-carbozincation among alkynyl ethers, silyl ketene acetals, and ZnBr2. X-ray analysis revealed the structure of the zinc species is a mononuclear two-coordinate dialkenylzinc that is transformed into functionalized enol ethers as a single isomer in the reaction of various electrophiles.
July 12, 2017: Organic Letters
https://www.readbyqxmd.com/read/28700219/versatile-site-selective-protein-reaction-guided-by-ww-domain-peptide-motif-interaction
#14
Miao Liu, Zeyang Ji, Mingjie Zhang, Jiang Xia
A short, flexible and unstructured peptide tag that has versatile and facile use in protein labeling applications is highly desirable. Here, we report an 11-residue peptide tag with an internal cysteine (a W-tag, derived from a Comm PY peptide motif that is known to bind with Nedd4 WW3* domain) that can be installed at different regions of the target protein without compromising its covalent reactivity with the reactive label (a 35-residue synthetic Nedd4 WW3* domain derivative). This versatility is explained by the unique structural features of the reaction...
July 12, 2017: Bioconjugate Chemistry
https://www.readbyqxmd.com/read/28699760/preparation-of-quinazolines-via-a-2-2-2-annulation-from-aryldiazonium-salts-and-nitriles
#15
Mani Ramanathan, Shiuh-Tzung Liu
A (2+2+2) modular synthesis of multi-substituted quinazolines has been realized by the direct reaction of aryldiazonium salts with two equivalent of nitriles. Reaction of aryldiazonium salt with a nitrile provides the initial formation of a reactive nitrilium ion, which is attacked by another molecule of nitrile followed by electrophilic cyclization to deliver the desired product. Notable flexibility in the substitution patterns, readily available substrates, short reaction time, transition metal-free and gram-scale synthesis are the advantages of this method...
July 12, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28699354/drug-mediated-intracellular-donation-of-nitric-oxide-potently-inhibits-5-lipoxygenase-a-possible-key-to-future-anti-leukotriene-therapy
#16
Jessica Roos, Marcus Peters, Isabelle V Maucher, Benjamin Kühn, Jasmin Fettel, Nadine Hellmuth, Camilla Brat, Benita Sommer, Anja Urbschat, Matthias Piesche, Anja Vogel, Ewgenij Proschak, René Blöcher, Estel la Buscato, Ann-Kathrin Häfner, Carmela Matrone, Oliver Werz, Juliana Heidler, Ilka Wittig, Carlo Angioni, Gerd Geisslinger, Michael J Parnham, Kai Zacharowski, Dieter Steinhilber, Thorsten Jürgen Maier
AIMS: 5-lipoxygenase (5-LO) is the key enzyme of leukotriene biosynthesis and is critically involved in a number of inflammatory diseases such as arthritis, gout, bronchial asthma, atherosclerosis and cancer. Because 5-LO contains critical nucleophilic amino acids, which are sensitive to electrophilic modifications, we determined the consequences of a drug-mediated intracellular release of nitric oxide (NO) on 5-LO product formation by human granulocytes and on 5-LO-dependent pulmonary inflammation in vivo...
July 12, 2017: Antioxidants & Redox Signaling
https://www.readbyqxmd.com/read/28696834/simultaneous-detection-of-the-tetrachloroethylene-metabolites-s-1-2-2-trichlorovinyl-glutathione-s-1-2-2-trichlorovinyl-l-cysteine-and-n-acetyl-s-1-2-2-trichlorovinyl-l-cysteine-in-multiple-mouse-tissues-via-ultra-high-performance-liquid-chromatography-electrospray
#17
Yu-Syuan Luo, Joseph A Cichocki, Thomas J McDonald, Ivan Rusyn
Tetrachloroethylene (perchloroethylene; PERC) is a high-production volume chemical and ubiquitous environmental contaminant that is hazardous to human health. Toxicity attributed to PERC is mediated through oxidative and glutathione (GSH) conjugation metabolites. The conjugation of PERC by glutathione-s-transferase to generate S-(1,2,2-trichlorovinyl) glutathione (TCVG), which is subsequently metabolized to form S-(1,2,2-trichlorovinyl)-L-cysteine (TCVC) is of special importance to human health. Specifically, TCVC may be metabolized to N-acetyl-S-(1,2,2-trichlorovinyl)-L-cysteine (NAcTCVC) which is excreted through urine, or to electrophilic metabolites that are nephrotoxic and mutagenic...
July 11, 2017: Journal of Toxicology and Environmental Health. Part A
https://www.readbyqxmd.com/read/28694766/flavoenzyme-mediated-reduction-reactions-and-antitumor-activity-of-nitrogen-containing-tetracyclic-ortho-quinone-compounds-and-their-nitrated-derivatives
#18
Milda Peciukaityte-Alksne, Jonas Šarlauskas, Lina Miseviciene, Audrone Maroziene, Narimantas Cenas, Kastis Krikštopaitis, Zita Staniulyte, Žilvinas Anusevicius
Nitrogen-based tetracyclic ortho-quinones (naphtho[1'2':4.5]imidazo[1,2-a]pyridine-5,6-diones, NPDOs) and their nitro-substituted derivatives (nitro-(P)NPDOs) were obtained by condensation of substituted 2,3-dichloro-1,4-naphthoquinones with 2-amino-pyridine and -pyrimidine and nitration at an elevated temperature. The structural features of the compounds as well as their global and regional electrophilic potency were characterized by means of DFT computation. The compounds were highly reactive substrates of single- and two-electron (hydride) - transferring P-450R (CPR; EC 1...
2017: EXCLI journal
https://www.readbyqxmd.com/read/28688915/targeted-proteome-analysis-with-isotope-coded-protein-labels-for-monitoring-the-influence-of-dietary-phytochemicals-on-the-expression-of-cytoprotective-proteins-in-primary-human-colon-cells
#19
Christiane Östreicher, Sven Bartenbacher, Monika Pischetsrieder
Cytoprotective effects by upregulating cellular expression levels of antioxidant proteins are attributed to a significant number of food ingredients. Evaluation of those cytoprotective effects and identification of the most active components requires reliable and comprehensive proteomic strategies. Thus, promising potential bioactive ingredients could be determined for the prevention of various diseases, including colon cancer formation. We established a multiplexed nanoLC-MS/MS targeted proteomic method, operated in scheduled selected reaction monitoring mode (sSRM), to record modulation of the expression levels of six major antioxidant proteins induced by dietary phytochemicals...
July 6, 2017: Journal of Proteomics
https://www.readbyqxmd.com/read/28688163/direct-monofluoromethylthiolation-with-s-fluoromethyl-benzenesulfonothioate
#20
Qunchao Zhao, Long Lu, Qilong Shen
An electrophilic shelf-stable monofluoromethylthiolating reagent S-(fluoromethyl)benezene sulfonothioate 1 was developed. In the presence of a copper catalyst, reagent 1 coupled with a variety of aryl boronic acids to give the corresponding monofluoromethylthiolated arenes in high yields. In addition, addition of reagent 1 to alkyl alkenes in the presence of a silver catalyst gave alkyl monofluoromethylthioethers in high yields.
July 7, 2017: Angewandte Chemie
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