Read by QxMD icon Read


Virve Sihvola, Anna-Liisa Levonen
Reactive oxygen species (ROS) and products of their reactions with cellular macromolecules such as unsaturated fatty acids have been implicated to be important regulators of signalling processes via oxidation or alkylation of redox active thiol residues in target proteins. One of key redox-sensitive signalling proteins mediating the response to oxidant stress is Keap1 (Kelch-like erythroid cell-derived protein with CNC homology [ECH]-associated protein 1), which is a negative regulator of transcription factor Nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) and the central hub for sensing endogenous and environmental oxidative and electrophilic stress...
October 18, 2016: Archives of Biochemistry and Biophysics
Huihui Li, Lingmei Guan, Xiaojie Zhang, Huan Yu, Dejian Huang, Mingtai Sun, Suhua Wang
Hypochlorous acid (HOCl) is a kind of reactive oxygen species which plays an important role in biological process. HOCl detection is of great importance in disease prevention and treatment. Herein, a cyanine-based near-infrared (NIR) fluorescent probe for HOCl has been designed and synthesized. This probe can react with HOCl in a dose-response manner along with the fluorescence of the probe quenched, the reaction through an electrophilic addition to the double bond and subsequent oxidation reaction. Experiments indicate that the probe can be acted as a selective and sensitive indicator for HOCl and the limit of detection for HOCl is estimated to be 22nM...
December 1, 2016: Talanta
Wenyan Xu, Daniel Kool, Derek K O'Flaherty, Ashley Keating, Lauralicia Sacre, Martin Egli, Anne Marietta Noronha, Christopher James Wilds, Linlin Zhao
DNA interstrand cross-links (ICLs) are cytotoxic DNA lesions derived from reactions of DNA with a number of anti-cancer reagents as well as endogenous bifunctional electrophiles. Deciphering the DNA repair mechanisms of ICLs is important for understanding the toxicity of DNA cross-linking agents and for the development of effective chemotherapies. Previous research has focused on ICLs cross-linked with the N7 and N2 atoms of guanine as well as those formed at the N6 atom of adenine; however, little is known about the mutagenicity of O6-dG-derived ICLs...
October 21, 2016: Chemical Research in Toxicology
Ruhuai Mei, Cuiju Zhu, Lutz Ackermann
C-H arylations of weakly coordinating benzoic acids were achieved by versatile ruthenium(ii) catalysis with ample substrate scope. Thus, user-friendly ruthenium(ii) biscarboxylate complexes modified with tricyclohexylphosphine enabled C-H functionalizations with aryl electrophiles. The unique versatility of the ruthenium(ii) catalysis manifold was reflected by facilitating effective C-H activations with aryl, alkenyl and alkynyl halides.
October 21, 2016: Chemical Communications: Chem Comm
Susanne Bähr, Martin Oestreich
Electrophilic substitution of arenes is a fundamental reaction in synthetic chemistry. It converts C-H bonds of sufficiently nucleophilic arenes into C-X and C-C bonds using either stoichiometrically added or catalytically generated electrophiles. These reactions proceed through Wheland complexes, that is cationic intermediates that rearomatize by proton release. Hence, these high-energy intermediates are nothing but protonated arenes and are as such strong Bronsted acids. The formation of protons is an issue in those rare cases when the electrophilic aromatic substitution is reversible...
October 20, 2016: Angewandte Chemie
Renata Kurtyka, Wojciech Pokora, Zbigniew Tukaj, Waldemar Karcz
Naphthoquinones are secondary metabolites widely distributed in nature and produced by bacteria, fungi and higher plants. Their biological activity may result from induction of oxidative stress, caused by redox cycling, or direct interaction with cellular macromolecules, in which quinones act as electrophiles. The redox homeostasis is known as one of factors involved in auxin-mediated plant growth regulation. To date, however, little is known about the crosstalk between reactive oxygen species (ROS) produced by quinones and the plant growth hormone auxin (IAA)...
October 19, 2016: AoB Plants
Stefano Menichetti, Riccardo Amorati, Valentina Meoni, Lorenzo Tofani, Gabriella Caminati, Caterina Viglianisi
Noncovalent sulfur···oxygen interactions can increase the stability of chalcogen ortho-substituted phenoxyl radicals. This effect contributes to transforming the 7-hydroxybenzo[b]thiophene moiety in a privileged structural motif to enhance the activity of phenolic antioxidants. A cascade of five consecutive electrophilic reactions occurring in one pot afforded potent and biocompatible α-tocopherol-like antioxidants.
October 18, 2016: Organic Letters
Sean M Maddox, Andrew N Dinh, Felipe Armenta, Joann Um, Jeffrey L Gustafson
Different catalysts are demonstrated to overcome or augment a substrate's innate regioselectivity. Nagasawa's bis-thiourea catalyst was found to overcome the innate para-selectivity of electrophilic phenol chlorination, yielding ortho-chlorinated phenols that are not readily obtainable via canonical electrophilic chlorinations. Conversely, a phosphine sulfide derived from 2,2'-Bis(diphenylphosphino)-1,1'-binaphthyl (BINAP) was found to enhance the innate para-preference of phenol chlorination.
October 18, 2016: Organic Letters
Jérôme Paul, Marc Presset, Frédéric Cantagrel, Erwan Le Gall, Eric Léonel
The cobalt-catalyzed multicomponent reaction between sp2-hybridized organic halides, Michael acceptors and unsaturated electrophiles is described. The reaction proceeds via a formal conjugate addition/aldol or aza-aldol (Mannich) tandem reaction initiated by the in situ metalation of the organic halide by cobalt-catalysis. The essentially new reaction conditions that have been developed are very mild and atom-economic. Under these conditions, a broad range of β-hydroxy- and β-aminocarbonyl compounds are obtained in good to high yields...
October 18, 2016: Chemistry: a European Journal
Luis R Domingo, Mar Ríos-Gutiérrez, Patricia Pérez
The molecular mechanism of the carbenoid-type [3 + 2] cycloaddition (32CA) reactions of a nitrile ylide (NY) with a non-chiral and a chiral oxazolidinone has been studied within Molecular Electron Density Theory (MEDT) at the MPWB1K/6-31G(d) computational level. Topological analysis of the Electron Localisation Function (ELF) of the NY shows that it presents a carbenoid structure. The high nucleophilic character of the NY together with the electrophilic character of the non-chiral oxazolidinone favour a polar 32CA reaction with a very low activation energy, the reaction being completely meta/endo selective...
October 18, 2016: Organic & Biomolecular Chemistry
Tamiris B Grimaldi, Guilherme Lutz, Davi F Back, Gilson Zeni
In this paper, we report our results on the cyclization of (biphenyl-2-alkyne) derivatives to give two different types of phenanthrene derivatives, 9-iodo-10-organochalcogen-phenanthrenes and 9-organochalcogen-phenanthrenes. The strategy for the synthesis was based on the use of electrophilic cyclization for the preparation of 9-iodo-10-organochalcogen-phenanthrenes and iron(iii) chloride/diorganyl diselenide-mediated intramolecular cyclization to prepare 9-organochalcogen-phenanthrenes. The effects of solvent, temperature, reaction time and stoichiometry on the efficiency of cyclization reactions were investigated...
October 18, 2016: Organic & Biomolecular Chemistry
Amin Hossein Bagi, Yousef Khaledi, Hossein Ghari, Sebastian Arndt, A Stephen K Hashmi, Brian F Yates, Alireza Ariafard
The gold-catalyzed direct functionalization of aromatic C-H bonds has attracted interest for constructing organic compounds which have application in pharmaceuticals, agrochemicals, and other important fields. In the literature, two major mechanisms have been proposed for these catalytic reactions: inner-sphere syn-addition and outer-sphere anti-addition (Friedel-Crafts-type mechanism). In the current article, the AuCl3-catalyzed hydrofurylation of allenyl ketone, vinyl ketone, ketone and alcohol substrates is investigated with the aid of density functional theory calculations and it is found that the corresponding functionalizations are best rationalized in terms of a novel mechanism called "concerted electrophilic ipso-substitution" (CEIS) in which the gold(III)-furyl σ-bond produced by furan auration acts as a nucleophile and attacks the protonated substrate via an outer-sphere mechanism...
October 17, 2016: Journal of the American Chemical Society
Jone Corrales, Lauren A Kristofco, W Baylor Steele, Gavin N Saari, Jakub Kostal, Edward Spencer Williams, Margaret Mills, Evan P Gallagher, Terrance J Kavanagh, Nancy Simcox, Longzhu Q Shen, Fjodor Melnikov, Julie B Zimmerman, Adelina M Voutchkova-Kostal, Paul T Anastas, Bryan W Brooks
Sustainable molecular design of less hazardous chemicals presents a potentially transformative approach to protect public health and the environment. Relationships between molecular descriptors and toxicity thresholds previously identified the octanol-water distribution coefficient, log D, and the HOMO-LUMO energy gap, ∆E, as two useful properties in the identification of reduced aquatic toxicity. To determine whether these two property-based guidelines are applicable to sublethal oxidative stress (OS) responses, two common aquatic in vivo models, the fathead minnow (Pimephales promelas) and zebrafish (Danio rerio), were employed to examine traditional biochemical biomarkers (lipid peroxidation, DNA damage, total glutathione) and antioxidant gene activation following exposure to eight structurally diverse industrial chemicals (bisphenol A, cumene hydroperoxide, dinoseb, hydroquinone, indene, perfluorooctanoic acid, R-(-)-carvone, tert-butyl hydroperoxide)...
October 17, 2016: Chemical Research in Toxicology
Marino Börjesson, Toni Moragas, Daniel Gallego, Ruben Martin
The recent years have witnessed the development of metal-catalyzed reductive carboxylation of organic (pseudo)halides with CO2 as C1 source, representing potential powerful alternatives to existing methodologies for preparing carboxylic acids, privileged motifs in a myriad of pharmaceuticals and molecules displaying significant biological properties. While originally visualized as exotic cross-coupling reactions, a close look into the literature data indicates that these processes have become a fertile ground, allowing for the utilization of a variety of coupling partners, even with particularly challenging substrate combinations...
October 7, 2016: ACS Catalysis
Weichao Xue, Zheng-Wang Qu, Stefan Grimme, Martin Oestreich
A copper-catalyzed C(sp3)-Si cross-coupling of aliphatic C(sp3)-I electrophiles using an Si-B reagent as the silicon pronucleophile is reported. The reaction involves an alkyl radical intermediate that also engages in 5-exo-trig ring closures onto pendant alkenes prior to the terminating C(sp3)-Si bond formation. Several Ueno-Stork-type precursors cyclized with excellent diastereocontrol in good yields. The base-mediated release of the silicon nucleophile and the copper-catalyzed radical process are analyzed by quantum-chemical calculations, leading to a full mechanistic picture...
October 16, 2016: Journal of the American Chemical Society
José Gomes, Christophe Daeppen, Raphael Liffert, Joel Roesslein, Elias Kaufmann, Annakaisa Heikinheimo, Markus Neuburger, Karl Gademann
Synthetic studies towards highly oxygenated seco-prezizaane sesquiterpenes are reported, which culminated in a formal total synthesis of the neurotrophic agent (-)-jiadifenolide. For the construction of the tricyclic core structure, an unusual intramolecular and diastereoselective Nozaki-Hiyama-Kishi reaction involving a ketone as electrophilic coupling partner was developed. In addition, synthetic approaches towards the related natural product (2R)-hydroxynorneomajucin, featuring a Mn-mediated radical cyclization for the tricycle assembly and a regioselective OH-directed C-H activation are presented...
October 14, 2016: Journal of Organic Chemistry
Guoyin Yin, Xin Mu, Guosheng Liu
Difunctionalization of alkenes to incorporate two functional groups across a double bond has emerged as a powerful transformation to greatly increase molecular complexity in organic synthesis with improved efficiency. Historically, palladium-catalyzed difunctionalization of alkenes has suffered from difficulties with introducing a second functional group through reductive elimination of a Pd(II) intermediate and competing β-hydride elimination reactions. To overcome these challenges, one strategy involves utilizing a steric bulky ligand to promote the reductive elimination steps from the Pd(II) center and impeding the β-hydride elimination reactions, which are beyond the scope of this Account...
October 14, 2016: Accounts of Chemical Research
Bernhard Stenger, Tanja Popp, Harald John, Markus Siegert, Amelie Tsoutsoulopoulos, Annette Schmidt, Harald Mückter, Thomas Gudermann, Horst Thiermann, Dirk Steinritz
Transient receptor potential family channels (TRPs) have been identified as relevant targets in many pharmacological as well as toxicological studies. TRP channels are ubiquitously expressed in different tissues and act among others as sensors for different external stimuli, such as mechanical stress or noxious impacts. Recent studies suggest that one member of this family, the transient receptor potential ankyrin 1 cation channel (TRPA1), is involved in pain, itch, and various diseases, suggesting TRPA1 as a potential therapeutic target...
October 13, 2016: Archives of Toxicology
Liangbin Huang, Daniel J Weix
Ruthenium ligated to tricyclohexylphosphine or di-tert-butylbipyridine catalyzes the arylation of carboxylic acids with diverse aryl halides (iodide, bromide, and triflate; aryl and heteroaryl). In addition, arylations with 2-iodophenol formed benzochromenones, carboxylate was shown to be a stronger donor than an amide, and the arylation of a pyridine carboxylate was demonstrated. Stoichiometric studies demonstrated that the added ligand is required for reaction with the electrophile but not the C-H bond.
October 13, 2016: Organic Letters
Patrick J Moon, Shengkang Yin, Rylan J Lundgren
We report decarboxylative carbonyl α-arylation by coupling arylboron nucleophiles with malonic acid derivatives. This process is enabled by the merger of aerobic oxidative Cu-catalysis with decarboxylative enolate interception reminiscent of malonyl-CoA reactivity in polyketide biosynthesis. This method allows for the synthesis of monoaryl acetate derivatives containing electrophilic functional groups that are incompatible with existing α-arylation reactivity paradigms. The utility of the reaction is demonstrated in drug intermediate synthesis and late-stage functionalization...
October 13, 2016: Journal of the American Chemical Society
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"