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https://www.readbyqxmd.com/read/28538738/solid-phase-synthesis-cyclization-and-site-specific-functionalization-of-aziridine-containing-tetrapeptides
#1
Benjamin K W Chung, Christopher J White, Andrei K Yudin
Cyclic tetrapeptides comprise a potent and selective class of molecules with a wide range of biological activities, including the phytotoxic activity of tentoxin and the histone deacetylase (HDAC) inhibitory effects of chlamydocin. The incorporation of a functional aziridine group within cyclic peptides enables their conformational control and allows for late-stage and site-selective functionalization of these molecules, thereby creating the potential for covalent protein labeling. This protocol describes the solid-phase synthesis, cyclization, and site-specific structural modification of aziridine-containing tetrapeptides...
June 2017: Nature Protocols
https://www.readbyqxmd.com/read/28534914/covalent-inhibition-of-protein-tyrosine-phosphatases
#2
REVIEW
Kasi Viswanatharaju Ruddraraju, Zhong-Yin Zhang
Protein tyrosine phosphatases (PTPs) are a large family of 107 signaling enzymes that catalyze the hydrolytic removal of phosphate groups from tyrosine residues in a target protein. The phosphorylation status of tyrosine residues on proteins serve as a ubiquitous mechanism for cellular signal transduction. Aberrant function of PTPs can lead to many human diseases, such as diabetes, obesity, cancer, and autoimmune diseases. As the number of disease relevant PTPs increases, there is urgency in developing highly potent inhibitors that are selective towards specific PTPs...
May 23, 2017: Molecular BioSystems
https://www.readbyqxmd.com/read/28534838/electrophilic-trifluoromethylselenolation-of-boronic-acids
#3
Clément Ghiazza, Anis Tlili, Thierry Billard
Trifluoromethylselenylated compounds are emergent compounds with interesting physicochemical properties that still suffer from a lack of efficient synthetic methods. We recently developed an efficient one-pot strategy to generate in situ CF₃SeCl and use it in various reactions. Herein, we continue our study of the reactivity scope of this preformed reagent. Cross-coupling reactions with aromatic and heteroaromatic boronic acids have been investigated. The expected products have been obtained, using a stoichiometric amount of copper, with moderate yields...
May 19, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28534837/electrophilic-selenium-catalysis-with-electrophilic-n-f-reagents-as-the-oxidants
#4
REVIEW
Ruizhi Guo, Lihao Liao, Xiaodan Zhao
A suitable oxidative system is crucial to electrophilic selenium catalysis (ESC). This short review offers the overview of recent development in ESC with electrophilic N-F reagents as the oxidants. Several highly selective transformations of alkenes such as allylic or vinylic imidation, pyridination, syn-dichlorination, oxidative cyclization and asymmetric cyclization have been described.
May 19, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28534638/diastereoselective-3-2-vs-4-2-cycloadditions-of-nitroprolinates-with-%C3%AE-%C3%AE-unsaturated-aldehydes-and-electrophilic-alkenes-an-example-of-total-periselectivity
#5
Verónica Selva, Olatz Larrañaga, Luis M Castelló, Carmen Nájera, José M Sansano, Abel de Cozar
Diastereoselective multicomponent reaction of enantioenriched 4-nitroprolinates, obtained by enantiocatalyzed 1,3-dipolar cycloaddition (1,3-DC) of imino esters and nitroalkenes, with α,β-unsaturated aldehydes and electrophilic alkenes proceed with total periselectivity depending on the structure of the aldehyde employed. This process evolves through a [3+2] 1,3-DC when cinnamaldehyde is used in the presence of an azomethine ylide giving the corresponding highly substituted pyrrolizidines with endo-selectivity...
May 23, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28534631/photochemical-formation-of-anthracene-quinone-methide-derivatives
#6
Djani Skalamera, Kata Mlinarić-Majerski, Irena Martin Kleiner, Marijeta Kralj, Jessy Oake, Peter Wan, Cornelia Bohne, Nikola Basaric
Anthrols 2-7 were synthesized and their photochemical reactivity investigated by irradiations in aq. CH3OH. Upon excitation with visible light (λ > 400 nm) in methanolic solutions they undergo photodehydration or photodeamination and deliver methyl ethers, most probably via quinone methides (QMs), with methanolysis quantum efficiencies ΦR = 0.02-0.3. Photophysical properties of 2-7 were determined by steady-state fluorescence and time-correlated single photon counting. Generally, anthrols 2-7 are highly fluorescent in aprotic solvents (ΦF = 0...
May 23, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28531327/interstrand-cross-links-arising-from-strand-breaks-at-true-abasic-sites-in-duplex-dna
#7
Zhiyu Yang, Nathan E Price, Kevin M Johnson, Yinsheng Wang, Kent S Gates
Interstrand cross-links are exceptionally bioactive DNA lesions. Endogenous generation of interstrand cross-links in genomic DNA may contribute to aging, neurodegeneration, and cancer. Abasic (Ap) sites are common lesions in genomic DNA that readily undergo spontaneous and amine-catalyzed strand cleavage reactions that generate a 2,3-didehydro-2,3-dideoxyribose sugar remnant (3'ddR5p) at the 3'-terminus of the strand break. Interestingly, this strand scission process leaves an electrophilic α,β-unsaturated aldehyde residue embedded within the resulting nicked duplex...
May 22, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28530721/palladium-catalysed-atom-economical-synthesis-of-conjugated-dienals-from-terminal-acetylenes-and-acrolein
#8
Zoë Hearne, Chao-Jun Li
Conjugated (E,E)-dienals are versatile synthetic intermediates owing to their trifunctional, electrophilic nature and the prevalence of the (E,E)-diene in a wide range of functional molecules. It is shown herein that (E,E)-dienals can be readily prepared in two palladium-catalysed steps from simple, unactivated starting materials; terminal acetylenes and acrolein can be coupled via conjugate addition, followed by alkyne isomerisation. This procedure provides a highly atom-economical, redox-neutral and practical method to prepare a range of conjugated (E,E)-dienals in good yields and diastereoselectivities...
May 22, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28528876/modeling-covalent-modifier-drugs
#9
REVIEW
Ernest Awoonor-Williams, Andrew G Walsh, Christopher N Rowley
In this review, we present a summary of how computer modeling has been used in the development of covalent modifier drugs. Covalent modifier drugs bind by forming a chemical bond with their target. This covalent binding can improve the selectivity of the drug for a target with complementary reactivity and result in increased binding affinities due to the strength of the covalent bond formed. In some cases, this results in irreversible inhibition of the target, but some targeted covalent inhibitor (TCI) drugs bind covalently but reversibly...
May 18, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28528297/biogenic-aldehydes-as-therapeutic-targets-for-cardiovascular-disease
#10
REVIEW
Margaret-Ann M Nelson, Shahid P Baba, Ethan J Andersonc
Aldehydes are continuously formed in biological systems through enzyme-dependent and spontaneous oxidation of lipids, glucose, and primary amines. These highly reactive, biogenic electrophiles can become toxic via covalent modification of proteins, lipids and DNA. Thus, agents that scavenge aldehydes through conjugation have therapeutic value for a number of major cardiovascular diseases. Several commonly-prescribed drugs (e.g., hydralazine) have been shown to have potent aldehyde-conjugating properties which may contribute to their beneficial effects...
May 18, 2017: Current Opinion in Pharmacology
https://www.readbyqxmd.com/read/28527906/fluorescent-probes-for-imaging-formaldehyde-in-biological-systems
#11
REVIEW
Kevin J Bruemmer, Thomas F Brewer, Christopher J Chang
Formaldehyde (FA) is a common environmental toxin but is also endogenously produced through a diverse array of essential biological processes, including mitochondrial one-carbon metabolism, metabolite oxidation, and nuclear epigenetic modifications. Its high electrophilicity enables reactivity with a wide variety of biological nucleophiles, which can be beneficial or detrimental to cellular function depending on the context. New methods that enable detection of FA in living systems can help disentangle the signal/stress dichotomy of this simplest reactive carbonyl species (RCS), and fluorescent probes for FA with high selectivity and sensitivity have emerged as promising chemical tools in this regard...
May 18, 2017: Current Opinion in Chemical Biology
https://www.readbyqxmd.com/read/28525871/different-binding-mechanisms-of-neutral-and-anionic-poly-perfluorinated-chemicals-to-human-transthyretin-revealed-by-in-silico-models
#12
Xianhai Yang, Felichesmi Lyakurwa, Hongbin Xie, Jingwen Chen, Xuehua Li, Xianliang Qiao, Xiyun Cai
Chemical forms-dependent binding interactions between phenolic compounds and human transthyretin (hTTR) have been elaborated previously. However, it is not known whether the binding interactions between ionizable halogenated alphatic compounds and hTTR also have the same manner. In this study, poly-/perfluorinated chemicals (PFCs) were selected as model compounds and molecular dynamic simulation was performed to investigate the binding mechanisms between PFCs and hTTR. Results show the binding interactions between the halogenated aliphatic compounds and hTTR are related to the chemical forms...
May 5, 2017: Chemosphere
https://www.readbyqxmd.com/read/28525863/optical-nonlinearity-and-charge-transfer-analysis-of-pyrene-adsorbed-on-silver-computational-and-experimental-investigations
#13
U Reeta Felscia, Beulah J M Rajkumar, Pranitha Sankar, Reji Philip, M Briget Mary
The interaction of pyrene on silver has been investigated using both experimental and computational methods. Hyperpolarizabilities computed theoretically together with experimental nonlinear absorption from open aperture Z-scan measurements, point towards a possible use of pyrene adsorbed on silver in the rational design of NLO devices. Presence of a red shift in both simulated and experimental UV-Vis spectra confirms the adsorption on silver, which is due to the electrostatic interaction between silver and pyrene, inducing variations in the structural parameters of pyrene...
May 10, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28521104/predicting-chemical-reactivity-from-the-charge-density-through-gradient-bundle-analysis-moving-beyond-fukui-functions
#14
Amanda Morgenstern, Timothy R Wilson, Mark E Eberhart
Predicting chemical reactivity is a major goal of chemistry. Toward this end, atom condensed Fukui functions of conceptual density functional theory have been used to predict which atom is most likely to undergo electrophilic or nucleophilic attack, providing regioselectivity information. We show that the most probable regions for electrophilic attack can be predicted through analysis of gradient bundle volumes---a property that depends only on the charge density of the neutral molecules. We also introduce gradient bundle condensed Fukui functions in order to compare the results from gradient bundle volume analysis...
May 18, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28520986/chemical-ligation-of-oligonucleotides-using-an-electrophilic-phosphorothioester
#15
Hideto Maruyama, Ryota Oikawa, Mayu Hayakawa, Shono Takamori, Yasuaki Kimura, Naoko Abe, Genichiro Tsuji, Akira Matsuda, Satoshi Shuto, Yoshihiro Ito, Hiroshi Abe
We developed a new approach for chemical ligation of oligonucleotides using the electrophilic phosphorothioester (EPT) group. A nucleophilic phosphorothioate group on oligonucleotides was converted into the EPT group by treatment with Sanger's reagent (1-fluoro-2,4-dinitrobenzene). EPT oligonucleotides can be isolated, stored frozen, and used for the ligation reaction. The reaction of the EPT oligonucleotide and an amino-modified oligonucleotide took place without any extra reagents at pH 7.0-8.0 at room temperature, and resulted in a ligation product with a phosphoramidate bond with a 39-85% yield...
May 18, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28520424/insights-on-the-reactivity-of-terminal-phosphanido-metal-complexes-toward-activated-alkynes-from-theoretical-computations
#16
Daniel Álvarez, Raúl Mera-Adasme, Lucía Riera, Gloria I Cárdenas-Jirón, Julio Pérez, Jesús Díaz, M Isabel Menéndez, Ramón López
Herein we present a theoretical study on the reaction of [Re(PPh2) (CO)3(phen)] (phen = 1,10-phenanthroline) and [Re(PPh2) (CO)3(bipy)] (bipy = 2,2'-bipyridine) toward methyl propiolate. In agreement with experimental results for the phen ligand, the coupling of the substituted acetylenic carbon with the nonsubstituted ortho carbon of the phen ligand is the preferred route from both kinetic and thermodynamic viewpoints with a Gibbs energy barrier of 18.8 kcal/mol and an exoergicity of 11.1 kcal/mol. There are other two routes, the insertion of the acetylenic fragment into the P-Re bond and the coupling between the substituted acetylenic carbon and a carbonyl ligand in cis disposition, which are kinetically less favorable than the preferred route (by 2...
May 18, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28516258/-biomarkers-of-internal-exposure-to-toxicologically-relevant-contaminants-in-food
#17
REVIEW
Klaus Abraham, Bernhard Monien, Alfonso Lampen
The assessment of health risks resulting from the intake of genotoxic carcinogens in food depends essentially on a valid exposure assessment. The reliability of the external exposure estimation is restricted by various factors, e. g. inaccurate data from dietary protocols and variations of food contaminant contents. As an alternative, the individual internal exposure to genotoxic substances may be described by specific biomarkers in different matrices. For example, mercapturic acids formed after glutathione conjugation of electrophilic metabolites can be detected in the urine...
May 17, 2017: Bundesgesundheitsblatt, Gesundheitsforschung, Gesundheitsschutz
https://www.readbyqxmd.com/read/28516179/%C3%AE-diazo-oxime-ethers-for-n-heterocycle-synthesis
#18
Subin Choi, Sujin Ha, Cheol-Min Park
This Feature Article introduces the preparation and synthetic utility of α-diazo oxime ethers. α-Oximino carbenes are useful synthons for N-heterocycles, and can be easily prepared from α-diazo oxime ethers as precursors. We begin with the preparation of α-diazo oxime ethers and their application in [3+2] cycloaddition. It turns out that the nature of metals bound to carbenes plays a crucial role in modulating the reactivity of α-oximino carbenes, in which copper carbenes smoothly react with enamines, whereas the less reactive enol ethers and nitriles require gold carbenes...
May 18, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28513162/radical-c-h-fluorination-using-unprotected-amino-acids-as-radical-precursors
#19
Alyssa M Hua, Duy N Mai, Ramon Martinez, Ryan D Baxter
We report a unique example of utilizing unprotected amino acids for benzylic C-H fluorination via a radical process. α-Aminoalkyl radicals are readily generated via oxidative decarboxylation of unprotected amino acids using a simple silver(I) catalyst and Selectfluor, which serves as both a mild oxidant and source of electrophilic fluorine. Mechanistic investigation shows that coordination of the unprotected amino acid plays a crucial role in lowering the oxidation potential of Ag(I), enabling oxidation under mild conditions...
May 17, 2017: Organic Letters
https://www.readbyqxmd.com/read/28512784/evaluation-of-aromatic-radiobromination-by-nucleophilic-substitution-using-diaryliodonium-salt-precursors
#20
Dong Zhou, Sung Hoon Kim, Wenhua Chu, Thomas Voller, John A Katzenellenbogen
Radiobromine labelled compounds can be used for positron emission tomography (PET) imaging (i.e. (76) Br) and for radiation therapy (i.e. (77) Br). However, the commonly used electrophilic substitution reaction using no-carrier-added (NCA) radiobromide does not always afford the desired product due to the high reactivity of the brominating intermediate. A nucleophilic substitution by bromide, such as radiobromination of iodonium precursors, provides an alternative route for the synthesis of bromo-radiopharmaceuticals...
May 17, 2017: Journal of Labelled Compounds & Radiopharmaceuticals
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