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https://www.readbyqxmd.com/read/28817776/electrophilic-cyclization-of-phenylalkynediols-to-naphthyl-aryl-iodonium-triflates-with-chelating-hydroxyls-preparation-and-x-ray-analyses
#1
Robert James Hinkle, Sarah E Bredenkamp, Robert David Pike, Seong Ik Cheon
Alkynediols containing one propargylic alcohol as well as a second alcohol, which is propargylic or homopropargylic, react with PhI(+)CN(-)OTf (Stang's reagent) or 3,5-(CF3)2C6H3I(+)CN(-)OTf to afford naphthyl(aryl)iodonium triflates. The reaction occurs at room temperature over the course of 6-12 hours and provides 36-82% yields of microcrystalline solids. Slow diffusion of Et2O into CH3CN solutions of the salts afforded X-ray quality crystals of five compounds with hydroxyl groups forming five- and six-membered chelation complexes with the iodine atom...
August 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28817258/synthesis-of-complex-glycolates-by-enantioconvergent-addition-reactions
#2
Samuel L Bartlett, Jeffrey S Johnson
The unique role that stereochemistry plays in molecular recognition events continues to provide a driving force for synthesizing organic compounds in enantioenriched form. The tendency of enantioenriched organic compounds to revert to an entropically favored racemic state in the presence of viable racemization pathways (e.g., the enolization of stereogenic carbonyl derivatives) can sometimes interfere with this objective; however, beginning with Noyori's foundational disclosure of a dynamic kinetic transfer hydrogenation, the ability to channel racemic, configurationally labile starting materials through stereoconvergent reaction pathways has been recognized as a powerful strategy in asymmetric synthesis...
August 17, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28817208/regio-and-stereoselective-chlorocyanation-of-alkynes
#3
Manuel Alcarazo, Alejandro G Barrado, Richard Goddard, Adam Zielinski
The regio- and stereoselective conversion of alkynes into (Z)-3-chloroacrylonitriles was achieved by treatment of a variety of terminal as well as internal alkynes with BCl3 in the presence of stoichiometric amounts of imidazolium thiocyanates. These products can be easily functionalized into useful building blocks, demonstrating the synthetic value of the method. Preliminary mechanistic studies suggest initial activation of the cationic thiocyanate by the Lewis acid followed by electrophilic attack of the alkyne...
August 17, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28816447/sequential-functionalizations-of-carbohydrates-enabled-by-boronic-esters-as-switchable-protective-activating-groups
#4
Ross S Mancini, Jessica B Lee, Mark S Taylor
Processes for site-selective, sequential functionalizations of carbohydrate derivatives are described. In these processes, a tricoordinate boronic ester initially serves as a protective group for a sugar-derived 1,2- or 1,3-diol motif, permitting functionalization of free OH groups. In a second step, addition of a Lewis base generates a tetracoordinate adduct, which serves as an activating group, enabling functionalization of one of the boron-bound oxygen atoms by a second electrophile. By combining an initial acylation, alkylation, or glycosylation step with an amine-mediated glycosylation of the boronic ester, a variety of selectively protected di- and trisaccharide derivatives can be accessed in an operationally simple fashion without purification of intermediates...
August 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28814509/chemoproteomics-reveals-chemical-diversity-and-dynamics-of-4-oxo-2-nonenal-modifications-in-cells
#5
Rui Sun, Ling Fu, Ke-Ke Liu, Cai-Ping Tian, Yong Yang, Keri A Tallman, Ned A Porter, Daniel C Liebler, Jing Yang
4-Oxo-2-nonenal (ONE) derived from lipid peroxidation modifies nucleophiles and transduces redox signaling by its reactions with proteins. However, the molecular interactions between ONE and complex proteomes and their dynamics in situ remain largely unknown. Here we describe a quantitative chemoproteomic analysis of protein adduction by ONE in cells, in which the cellular target profile of ONE is mimicked by its alkynyl surrogate. The analyses reveal four types of ONE-derived modifications in cells, including ketoamide and Schiff-base adducts to lysine, Michael adducts to cysteine, and a novel pyrrole adducts to cysteine...
August 16, 2017: Molecular & Cellular Proteomics: MCP
https://www.readbyqxmd.com/read/28812897/selective-formation-of-functionalized-%C3%AE-quaternary-malononitriles-toward-5-5-disubstituted-pyrrolopyrimidinones
#6
Alan Whitehead, Yong Zhang, Jamie McCabe Dunn, Edward C Sherer, Yu-Hong Lam, John Stelmach, Aaron Sun, Melisa Shiroda, Robert K Orr, Sherman T Waddell, Subharekha Raghavan
A modular, selective approach to complex α-tertiary substituted malononitriles is reported. The method takes advantage of β-ester-substituted α,α-dinitrile alkenes as highly reactive, chemoselective electrophiles for 1,4-additions with organometallic nucleophiles to produce functionally and sterically dense all-carbon quaternary centers. In the presence of a chiral ester auxiliary bearing an aromatic ring, the 1,4-addition occurs with good to excellent selectivity due to favorable cation-π interactions...
August 16, 2017: Organic Letters
https://www.readbyqxmd.com/read/28812331/a-synthesis-of-crocagin-a
#7
Filip Bihelovic, Desiree Stichnoth, Rolf Müller, Dirk Trauner, Frank Surup
Crocagin A (1) combines an attractive molecular structure with an unusual biosynthesis and bioactivity. Here, we present an efficient synthesis of crocagin A that hinges on an early formation of its heterotricyclic core, an electrophilic amination, and a stereoselective hydrogenation of a tetrasubstituted double bond. Our synthesis confirms the absolute configuration of crocagin A and provides access to the natural product and derivatives thereof for further biological testing.
August 15, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28810137/time-gated-luminescence-imaging-of-singlet-oxygen-photoinduced-by-fluoroquinolones-and-functionalized-graphenes-in-daphnia-magna
#8
Tianlie Luo, Jingwen Chen, Bo Song, Hua Ma, Zhiqiang Fu, Willie J G M Peijnenburg
Singlet oxygen ((1)O2) can be photogenerated by photoactive xenobiotics and is capable of causing adverse effects due to its electrophilicity and its high reactivity with biological molecules. Detection of the production and distribution of (1)O2 in living organisms is therefore of great importance. In this study, a luminescent probe ATTA-Eu(3+) combined with time-gated luminescence imaging was adopted to detect the distribution and temporal variation of (1)O2 photoinduced by fluoroquinolone antibiotics and carboxylated/aminated graphenes in Daphnia magna...
July 29, 2017: Aquatic Toxicology
https://www.readbyqxmd.com/read/28809976/2-2-diiododimedone-a-mild-electrophilic-iodinating-agent-for-the-selective-synthesis-of-%C3%AE-iodoketones-from-allylic-alcohols
#9
Samuel Martinez-Erro, Antonio Bermejo Gómez, Ana Vázquez-Romero, Elis Erbing, Belén Martín-Matute
2,2-Diiodo-5,5-dimethylcyclohexane-1,3-dione is reported as a new electrophilic iodinating agent that selectively iodinates electron-rich aromatics. In contrast to other common electrophilic iodinating reagents, its mild nature allows it to be used for the selective synthesis of α-iodinated carbonyl compounds from allylic alcohols through a 1,3-hydrogen shift/iodination process catalyzed by iridium(iii) complexes.
August 15, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28809580/temperature-dependent-enantio-and-diastereodivergent-synthesis-of-amino-acids-with-one-or-multiple-chiral-centers
#10
Shiming Fan, Shouxin Liu, Sufang Zhu, Juan Feng, Zhiwei Zhang, Jing Huang
A general and facile methodology for temperature-dependent enantiodivergent and diastereodivergent synthesis of amino acids with one or multiple chiral centers was developed. Camphor-based tricyclic iminolactones attack electrophiles from the endo face at low temperature (-78 to -40 °C) and from the exo face at high temperature (-10 to 25 °C).
August 15, 2017: Organic Letters
https://www.readbyqxmd.com/read/28809490/electrophilic-zinc-homoenolates-synthesis-of-cyclopropylamines-from-cyclopropanols-and-amines
#11
L Reginald Mills, Luis Miguel Barrera Arbelaez, Sophie A L Rousseaux
Metal homoenolates, produced via C-C bond cleavage of cyclopropanols, have been extensively investigated as nucleophiles for the synthesis of β-substituted carbonyl derivatives. Herein, we demonstrate that zinc homoenolates can react as carbonyl-electrophiles in the presence of nucleophilic amines to yield highly valuable trans-cyclopropylamines in good yields and high diastereoselectivities. GSK2879552, a lysine demethylase 1 inhibitor currently in clinical trials for the treatment of small cell lung carcinoma, was synthesized using this strategy...
August 15, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28809110/deprotonative-silylation-of-aromatic-c-h-bonds-mediated-by-a-combination-of-trifluoromethyltrialkylsilane-and-fluoride
#12
Kanako Nozawa-Kumada, Sayuri Osawa, Midori Sasaki, Isabelle Chataigner, Masanori Shigeno, Yoshinori Kondo
A method for the deprotonative silylation of aromatic C-H bonds has been developed using trifluoromethyltrimethylsilane (CF3SiMe3, Ruppert-Prakash reagent) and a catalytic amount of fluoride. In this reaction, CF3SiMe3 is considered to act as a base and a silicon electrophile. This process is highly tolerant to various functional groups on heteroarenes and benzenes. Furthermore, this method can be applied to the synthesis of trimethylsilyl group-containing analogs of TAC-101, which is a bioactive synthetic retinoid with selective affinity for RAR-α binding...
August 15, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28807817/assessment-of-glutathione-glutathione-disulphide-ratio-and-s-glutathionylated-proteins-in-human-blood-solid-tissues-and-cultured-cells
#13
REVIEW
Daniela Giustarini, Graziano Colombo, Maria Lisa Garavaglia, Emanuela Astori, Nicola Marcello Portinaro, Francesco Reggiani, Salvatore Badalamenti, Anna Maria Aloisi, Annalisa Santucci, Ranieri Rossi, Aldo Milzani, Isabella Dalle-Donne
Glutathione (GSH) is the major non-protein thiol in humans and other mammals, which is present in millimolar concentrations within cells, but at much lower concentrations in the blood plasma. GSH and GSH-related enzymes act both to prevent oxidative damage and to detoxify electrophiles. Under oxidative stress, two GSH molecules become linked by a disulphide bridge to form glutathione disulphide (GSSG). Therefore, assessment of the GSH/GSSG ratio may provide an estimation of cellular redox metabolism. Current evidence resulting from studies in human blood, solid tissues, and cultured cells suggests that GSH also plays a prominent role in protein redox regulation via S-glutathionylation, i...
August 11, 2017: Free Radical Biology & Medicine
https://www.readbyqxmd.com/read/28806081/chlorination-kinetics-of-11-nor-9-carboxy-%C3%AE-9-tetrahydrocannabinol-effects-of-ph-and-humic-acid
#14
Allison L Mackie, Yuri Park, Graham A Gagnon
The main psychoactive compound in marijuana, Δ9-tetrahydrocannabinol (THC), and its metabolites are emerging organic contaminants that have been detected in waste and surface waters. As legalization of marijuana for medical and recreational use continues, the effects of increased use and potency of marijuana on water and wastewater treatment processes and the environment should be considered. This study examined degradation kinetics of the main urinary metabolite of THC, 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH) with chlorine...
August 14, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28805726/chemical-identity-of-interaction-of-protein-with-reactive-metabolite-of-diosbulbin-b-in-vitro-and-in-vivo
#15
Kai Wang, Dongju Lin, Xiucai Guo, Wenlin Huang, Ying Peng, Jiang Zheng
Diosbulbin B (DIOB), a hepatotoxic furan-containing compound, is a primary ingredient in Dioscorea bulbifera L., a common herbal medicine. Metabolic activation is required for DIOB-induced liver injury. Protein covalent binding of an electrophilic reactive intermediate of DIOB is considered to be one of the key mechanisms of cytotoxicity. A bromine-based analytical technique was developed to characterize the chemical identity of interaction of protein with reactive intermediate of DIOB. Cysteine (Cys) and lysine (Lys) residues were found to react with the reactive intermediate to form three types of protein modification, including Cys adduction, Schiff's base, and Cys/Lys crosslink...
August 14, 2017: Toxins
https://www.readbyqxmd.com/read/28804677/haloselective-cross-coupling-via-ni-photoredox-dual-catalysis
#16
Kingson Lin, Rebecca J Wiles, Christopher B Kelly, Geraint H M Davies, Gary A Molander
The chemoselective functionalization of polyfunctional aryl linchpins is crucial for rapid diversification. Although well-explored for Csp(2) and Csp nucleophiles, the chemoselective introduction of Csp(3) groups remains notoriously difficult and is virtually undocumented using Ni catalysts. To fill this methodological gap, a "haloselective" cross-coupling process of arenes bearing two halogens, I and Br, using ammonium alkylbis(catecholato)silicates, has been developed. Utilizing Ni/photoredox dual catalysis, Csp(3) -Csp(2) bonds can be forged selectively at the iodine-bearing carbon of bromo(iodo)arenes...
August 4, 2017: ACS Catalysis
https://www.readbyqxmd.com/read/28803474/bioinspired-indole-prenylation-reactions-in-water
#17
Satomi Tanaka, Shinya Shiomi, Hayato Ishikawa
Isoprene units derived from dimethylallyl diphosphate (DMAPP) are an important motif in many natural products including terpenoids, carotenoids, steroids, and natural rubber. Understanding the chemical characteristics of DMAPP is an important topic in natural products chemistry, organic chemistry, and biochemistry. We have developed a direct bioinspired indole prenylation reaction using DMAPP or its equivalents as the electrophile in homogeneous aqueous acidic media in the absence of enzyme to provide prenylated indole products...
August 13, 2017: Journal of Natural Products
https://www.readbyqxmd.com/read/28802072/fifty-years-of-benz-oxaphospholene-chemistry
#18
Jan Berton, Thomas Heugebaert, David Virieux, Chris Victor Stevens
The first synthesis of benzoxaphospholenes dates back to the 60s. Since then, the structural variety of reported (benz)oxaphospholenes has steadily increased. Organophosphorus compounds have caught the interest of synthetic chemists for a couple of decades now because of their interesting biological properties. Oxaphospholenes, in particular, could serve as carbohydrate mimetics, while benzoxaphospholenes have been reported to possess bactericidal, insecticidal, herbicidal and fungistatical properties. Transesterification reactions and addition of phosphorus nucleophiles to carbonyl compounds were reaction types that led to the production of the first (benz)oxaphospholenes...
August 12, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28801573/a-structural-and-mechanistic-study-of-%C3%AF-clamp-mediated-cysteine-perfluoroarylation
#19
Peng Dai, Jonathan K Williams, Chi Zhang, Matthew Welborn, James J Shepherd, Tianyu Zhu, Troy Van Voorhis, Mei Hong, Bradley L Pentelute
Natural enzymes use local environments to tune the reactivity of amino acid side chains. In searching for small peptides with similar properties, we discovered a four-residue π-clamp motif (Phe-Cys-Pro-Phe) for regio- and chemoselective arylation of cysteine in ribosomally produced proteins. Here we report mutational, computational, and structural findings directed toward elucidating the molecular factors that drive π-clamp-mediated arylation. We show the significance of a trans conformation prolyl amide bond for the π-clamp reactivity...
August 11, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28793787/the-roles-of-nrf2-in-modulating-cellular-iron-homeostasis
#20
Michael John Kerins, Aikseng Ooi
SIGNIFICANCE: Iron and oxygen are intimately linked: iron is an essential nutrient utilized as a cofactor in enzymes for oxygen transport, oxidative phosphorylation, and metabolite oxidation. However, excess labile iron facilitates the formation of oxygen-derived free radicals capable of damaging biomolecules. Therefore, biological utilization of iron is a tightly regulated process. The nuclear factor (erythroid-derived 2)-like 2 (NRF2) transcription factor, which can respond to oxidative and electrophilic stress, regulates several genes involved in iron metabolism...
August 10, 2017: Antioxidants & Redox Signaling
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