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https://www.readbyqxmd.com/read/29352068/maternal-fetal-disposition-and-metabolism-of-retrorsine-in-pregnant-rats
#1
Xia Li, Xiaojing Yang, E Xiang, Jinyuan Luo, Shuaikai Qiu, Yan Fang, Li Zhang, Yu Guo, Jiang Zheng, Hui Wang
Pyrrolizidine alkaloids (PAs) are extensively synthesized by plants and are commonly present in herbs and foodstuffs, which exhibit hepatotoxicity requiring metabolic activation by cytochrome P450 (CYP) 3A to form the electrophilic metabolites-pyrrolic ester. PAs also cause embryo toxicity, but the metabolic profiles of PAs in fetus and placenta have been far from clear. In this study, we determined the basal metabolic activation of retrorsine (RTS) in rat maternal liver, placenta and fetal liver in vitro, and examined the fetal toxicity and bioactivation of RTS in vivo...
January 19, 2018: Drug Metabolism and Disposition: the Biological Fate of Chemicals
https://www.readbyqxmd.com/read/29350934/a-molecular-electron-density-theory-study-of-the-reactivity-and-selectivities-in-3-2-cycloaddition-reactions-of-c-n-dialkyl-nitrones-with-ethylene-derivatives
#2
Luis R Domingo, Mar Ríos-Gutiérrez, Patricia Pérez
The zw-type [3+2] cycloaddition (32CA) reactions of C,N-dialkyl nitrones with a series of ethylenes of increased electrophilic character have been studied within the Molecular Electron Density Theory (MEDT) at the MPWB1K/6-311G(d,p) computational level. Both, reactivity and selectivities are rationalised depending on the polar character of the reaction. Due to the strong nucleophilic character of C,N-dialkyl nitrones, the corresponding zw-type 32CA reactions are accelerated with the increased electrophilic character of the ethylene, which also plays a crucial role in the reaction mechanism, thus determining the regio- and stereoselectivities experimentally observed...
January 19, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29349898/helenalin-analogues-targeting-nf-%C3%AE%C2%BAb-p65-thiol-reactivity-and-cellular-potency-studies-of-varied-electrophiles
#3
John C Widen, Aaron M Kempema, Jordan W Baur, Hannah M Skopec, Jacob T Edwards, Tenley J Brown, Dennis A Brown, Frederick A Meece, Daniel A Harki
Helenalin is a pseudoguaianolide natural product that targets Cys38 within the DNA binding domain of NF-κB transcription factor p65 (RelA). Helenalin contains two Michael acceptors that covalently modify cysteines: a α-methylene-γ-butyrolactone and a cyclopentenone. We recently reported two simplified helenalin analogues that mimic the biological activity of helenalin and contain both electrophilic moieties. To determine the individual contributions of the Michael acceptors toward NF-κB inhibition, we synthesized a small library of helenalin-based analogues containing various combinations of α-methylene-γ-butyrolactones and cyclopentenones...
January 19, 2018: ChemMedChem
https://www.readbyqxmd.com/read/29348462/piperlongumine-and-p53-reactivator-apr-246-selectively-induce-cell-death-in-hnscc-by-targeting-gstp1
#4
Wei Hang, Zhi-Xian Yin, Gang Liu, Qinghua Zeng, Xiang-Feng Shen, Qian-Hui Sun, Dong-Dong Li, Yong-Ping Jian, Yang-He Zhang, Yi-Shu Wang, Cheng-Shi Quan, Rui-Xun Zhao, Yu-Lin Li, Zhi-Xiang Xu
TP53 mutations frequently occur in head and neck squamous cell carcinoma (HNSCC) patients without human papillomavirus infection. The recurrence rate for these patients is distinctly high. It has been actively explored to identify agents that target TP53 mutations and restore wild-type (WT) TP53 activities in HNSCC. PRIMA-1 (p53-reactivation and induction of massive apoptosis-1) and its methylated analogue PRIMA-1Met (also called APR-246) were found to be able to reestablish the DNA-binding activity of p53 mutants and reinstate the functions of WT p53...
January 18, 2018: Oncogene
https://www.readbyqxmd.com/read/29346729/electronic-interactions-in-iminophosphorane-superbase-complexes-with-carbon-dioxide
#5
Francesca Ingrosso, Manuel F Ruiz-Lopez
Iminophosphoranes or phosphazenes are an important class of compounds with increasing use in synthetic organic chemistry as neutral organic superbases exhibiting low nucleophilicity. Their electronic structure and therefore their properties strongly depend on substitution but there have been very few theoretical studies devoted to this topic, and more specifically to the formation of electron donor-acceptor complexes of iminophosphoranes with electrophiles. In this work, we have investigated the interaction with carbon dioxide at different ab initio levels...
January 18, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29346322/regioselective-synthesis-of-procyanidin-b6-a-4-6-condensed-catechin-dimer-by-intramolecular-condensation
#6
Yusuke Higashino, Taisuke Okamoto, Kazuki Mori, Takashi Kawasaki, Masahiro Hamada, Noriyuki Nakajima, Akiko Saito
Proanthocyanidins, also known as condensed tannins or oligomeric flavonoids, are found in many edible plants and exhibit interesting biological activities. Herein, we report a new, simple method for the stereoselective synthesis of procyanidin B6, a (+)-catechin-(4-6)-(+)-catechin dimer, by Lewis acid-catalyzed intramolecular condensation. The 5-O-t-butyldimethylsilyl (TBDMS) group of 5,7,3'4'-tetra-O-TBDMS-(+)-catechin was regioselectively removed using trifluoroacetic acid, leading to the "regio-controlled" synthesis of procyanidin B6...
January 18, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/29345706/tuning-the-nucleophilicity-of-electron-rich-diborane-4-compounds-with-bridging-guanidinate-substituents-by-substitution
#7
Julian Horn, Anna Widera, Sebastian Litters, Elisabeth Kaifer, Hans-Jörg Himmel
Diborane(4) compounds are versatile reagents in synthetic chemistry. Generally, diboranes(4) with sp2-hybridized boron atoms react as electrophiles. By contrast, the chemistry of nucleophilic diborane(4) compounds with two sp3-hybridized boron atoms is very much underdeveloped. In this work, we systematically vary the substituents of electron-rich diborane(4) compounds with bridging guanidinate substituents. In this way, five new diboranes are synthesized and fully characterized. Using quantum chemical computations, we show that the electronic properties and reactivity of these compounds can be rationally varied by the choice of substituents...
January 18, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/29344594/lithiation-of-palladated-dihydropentacene-a-new-route-for-the-introduction-of-substituents-from-both-of-electrophiles-and-nucleophiles-to-pentacene
#8
Yanqing Wang, Kiyohiko Nakajima, Zhiyi Song, Tamotsu Takahashi
Dibromodihydropentacene compound 1 was palladated and then lithiated to give a lithiated-palladated intermediate. Both of the lithium moiety and the palladium complex moiety on dihydropentacene unexpectedly survived in the solution. The Li and Pd moieties reacted with electrophiles and nucleophiles respectively to give the substituted dihydropentacene products. Aromatization of these dihydropentacenes gave substituted pentacene derivatives.
January 18, 2018: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/29342849/comparative-response-of-the-hepatic-transcriptomes-of-domesticated-and-wild-turkey-to-aflatoxin-b%C3%A2
#9
Kent M Reed, Kristelle M Mendoza, Juan E Abrahante, Roger A Coulombe
The food-borne mycotoxin aflatoxin B₁ (AFB₁) poses a significant risk to poultry, which are highly susceptible to its hepatotoxic effects. Domesticated turkeys (Meleagris gallopavo) are especially sensitive, whereas wild turkeys (M. g. silvestris) are more resistant. AFB₁ toxicity entails bioactivation by hepatic cytochrome P450s to the electrophilic exo-AFB₁-8,9-epoxide (AFBO). Domesticated turkeys lack functional hepatic GST-mediated detoxification of AFBO, and this is largely responsible for the differences in resistance between turkey types...
January 13, 2018: Toxins
https://www.readbyqxmd.com/read/29341599/a-ni-catalyzed-carbon-carbon-bond-forming-reductive-amination
#10
Christoph Heinz, J Patrick Lutz, Eric M Simmons, Michael M Miller, William R Ewing, Abigail G Doyle
This report describes a three-component, Ni-catalyzed reductive coupling that enables the convergent synthesis of tertiary benzhydryl amines, which are challenging to access by traditional reductive amination methodologies. The reaction makes use of iminium ions generated in situ from the condensation of secondary N-trimethylsilyl amines with benzaldehydes, and these species undergo reaction with several distinct classes of organic electrophiles. The synthetic value of this process is demonstrated by a single-step synthesis of antimigraine drug flunarizine (Sibelium®) and high yielding derivatization of paroxetine (Paxil®) and metoprolol (Lopressor®)...
January 17, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29341333/br%C3%A3-nsted-base-catalyzed-umpolung-intramolecular-cyclization-of-alkynyl-imines
#11
Azusa Kondoh, Masahiro Terada
A novel "umpolung" intramolecular cyclization of alkynyl imines, in which the electrophilic imine sp2-carbon formally serves as a nucleophilic site, was developed under Brønsted base catalysis. The reaction involves the unprecedented catalytic generation of α-aminoester enolates from α-iminoesters via the 1,2-addition of the anion of a secondary phosphite to an imine moiety followed by the [1,2]-rearrangement of a dialkoxyphosphoryl moiety from carbon to nitrogen, which is a formal umpolung process, and the intramolecular addition to an alkyne...
January 17, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29339426/gut-microbial-glycerol-metabolism-as-an-endogenous-acrolein-source
#12
Jianbo Zhang, Shana Sturla, Christophe Lacroix, Clarissa Schwab
Acrolein is a highly reactive electrophile causing toxic effects, such as DNA and protein adduction, oxidative stress, endoplasmic reticulum stress, immune dysfunction, and membrane damage. This Opinion/Hypothesis provides an overview of endogenous and exogenous acrolein sources, acrolein's mode of action, and its metabolic fate. Recent reports underpin the finding that gut microbial glycerol metabolism leading to the formation of reuterin is an additional source of endogenous acrolein. Reuterin is an antimicrobial multicomponent system consisting of 3-hydroxypropionaldehyde, its dimer and hydrate, and also acrolein...
January 16, 2018: MBio
https://www.readbyqxmd.com/read/29338212/catalytic-dehydrogenative-stannylation-of-c-sp-h-bonds-involving-cooperative-sn-h-bond-activation-of-hydrostannanes
#13
Francis Forster, Victoria M Rendón López, Martin Oestreich
The catalytic generation of a stannylium-ion-like tin electrophile by heterolytic cleavage of the Sn-H bond in hydrostannes at the Ru-S bond of Ohki-Tatsumi complexes is reported. Reacting these activated hydrostannanes with terminal acetylenes does not lead to hydrostannylation of the C-C triple bond but to dehydrogenative stannylation of the alkyne terminus. The scope of this rare direct C(sp)-H bond stannylation with hydrostannanes is broad, and a mechanism involving a beta-tin-stabilized vinyl cation having a bridged structure is presented...
January 17, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29335845/carnosic-acid-as-a-promising-agent-in-protecting-mitochondria-of-brain-cells
#14
REVIEW
Marcos Roberto de Oliveira
Carnosic acid (CA; C20H28O4), a phenolic diterpene characterized as an ortho-dihydroquinone-type molecule, is a pro-electrophile agent that becomes an electrophile after reacting with free radicals. The electrophile generated from CA interacts with and activates the nuclear factor erythroid 2-related factor 2 (Nrf2) transcription factor, which is a major modulator of redox biology in mammalian cells. CA induces antioxidant and anti-inflammatory effects in several cell types, as observed in both in vitro and in vivo experimental models...
January 15, 2018: Molecular Neurobiology
https://www.readbyqxmd.com/read/29335701/a-mononuclear-manganese-iii-hydroperoxo-complex-synthesis-by-activating-dioxygen-and-reactivity-in-electrophilic-and-nucleophilic-reactions
#15
Muniyandi Sankaralingam, Yong-Min Lee, So Hyun Jeon, Mi Sook Seo, Kyung-Bin Cho, Wonwoo Nam
We report the synthesis of manganese(iii)-peroxo (MnIII(O2)) and manganese(iii)-hydroperoxo (MnIII(O2H)) complexes by activating dioxygen (O2) and the amphoteric reactivity of the Mn(iii)-hydroperoxo complex in electrophilic and nucleophilic reactions.
January 16, 2018: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/29334462/pot-economy-autooxidative-condensation-of-2-aryl-2-lithio-1-3-dithianes
#16
João R Vale, Tatu Rimpiläinen, Elina Sievanen, Kari Rissanen, Carlos A M Afonso, Nuno R Candeias
The autooxidative condensation of 2-aryl-2-lithio-1,3-dithianes is here reported. Treatment of 2-aryl-1,3-dithianes with n-BuLi in the absence of any electrophile leads to condensation of three molecules of 1,3-dithianes and formation of highly functionalized α-thioether ketones orthothioesters in 51-89% yields upon air exposure. The method was further expanded to benzaldehyde dithioacetals, affording corresponding orthothioesters and α-thioether ketones in 48-97% yields. The experimental results combined with density functional theory studies support a mechanism triggered by the autooxidation of 2-aryl-2-lithio-1,3-dithianes to yield a highly reactive thioester that undergoes condensation with two other molecules of 2-aryl-2-lithio-1,3-dithiane...
January 15, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29334103/unexpected-cleavage-of-upper-rim-bridged-calix-4-arenes-leading-to-linear-oligophenolic-derivatives
#17
P Slavík, H Dvořáková, M Krupička, P Lhoták
Regioselective meta-mercuration followed by Pd-catalysed intramolecular bridging gave birth to a novel type of calixarene bearing a single bond bridge between the meta positions of the neighboring aromatic subunits. These bridged derivatives possess extremely distorted cavities that imply possible amended properties over common calix[4]arenes. This new type of calixarene reactivity can be documented by acid-/electrophile-mediated cleavage of the basic macrocyclic skeleton leading to open oligomeric structures-the behavior of which has never been observed before in classic calix[4]arenes bearing alkoxy groups on the lower rim...
January 15, 2018: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29332395/structure-and-reactivity-of-half-sandwich-rh-3-and-ir-3-carbene-complexes-catalytic-metathesis-of-azobenzene-derivatives
#18
Daniel J Tindall, Christophe Werlé, Richard Goddard, Petra Philipps, Christophe Farès, Alois Fürstner
Traditional rhodium carbene chemistry relies on the controlled decomposition of diazo derivatives with [Rh2(OAc)4] or related dinuclear Rh(+2) complexes, whereas the use of other rhodium sources is much less developed. It is now shown that half-sandwich carbene species derived from [Cp*MX2]2 (M = Rh, Ir; X = Cl, Br, I, Cp* = pentamethylcyclopentadienyl) also exhibit favorable application profiles. Interestingly, the anionic ligand X proved to be a critical determinant of reactivity in the case of cyclopropanation, epoxide formation and the previously unknown catalytic metathesis of azobenzene derivatives, whereas the nature of X does not play any significant role in -OH insertion reactions...
January 14, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29330904/testing-a-chemical-series-inspired-by-plant-stress-oxylipin-signaling-agents-for-herbicide-safening-activity
#19
Melissa Brazier-Hicks, Kathryn M Knight, Jonathan D Sellars, Patrick G Steel, Robert Edwards
BACKGROUND: Herbicide safening in cereals is linked to a rapid xenobiotic response (XR), involving the induction of glutathione transferases (GSTs). The XR is also invoked by oxidized fatty acids (oxylipins) released during plant stress, suggesting a link between these signaling agents and safening. To examine this relationship, a series of compounds modelled on the oxylipins 12-oxophytodienoic acid and phytoprostane 1, varying in lipophilicity and electrophilicity were synthesized. Compounds were then tested for their ability to invoke the XR in Arabidopsis and protect rice seedlings exposed to the herbicide pretilachlor, as compared with the safener fenclorim...
January 13, 2018: Pest Management Science
https://www.readbyqxmd.com/read/29328667/enhancing-reactivity-and-site-selectivity-in-hydrogen-atom-transfer-from-amino-acid-c-h-bonds-via-deprotonation
#20
Luca Maria Pipitone, Giulia Carboni, Daniela Sorrentino, Marco Galeotti, Michela Salamone, Massimo Bietti
A kinetic study on the reactions of the cumyloxyl radical (CumO•) with N-Boc-protected amino acids in the presence of the strong organic base DBU has been carried out. CO2H deprotonation increases the electron density at the α-C-H bonds activating these bonds toward HAT to the electrophilic CumO• strongly influencing the intramolecular selectivity. The implications of these results are discussed in the framework of HAT-based aliphatic C-H bond functionalization of amino acids and peptides.
January 12, 2018: Organic Letters
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