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Abhijit Mal, Masthanvali Sayyad, Imtiyaz Ahmad Wani, Manas K Ghorai
A highly enantioselective synthetic route to hexahydropyrrolo[2,3-b]indoles via Lewis acid-catalyzed SN2-type ring opening of activated aziridines with indoles having substitutions at 3- and other positions followed by cyclization in a domino fashion has been developed. Hexahydropyrrolo[2,3-b]indoles have been detosylated in the same pot to afford the corresponding products with free NH group in excellent yields (up to 95%) and enantioselectivity (up to >99%).
October 19, 2016: Journal of Organic Chemistry
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
Manuel A Ortuño, Nasarella A Jasim, Adrian C Whitwood, Agustí Lledós, Robin N Perutz
A computational study of the C(methyl)-O bond activation of fluorinated aryl methyl ethers by a platinum(0) complex Pt(PCyp3)2 (Cyp = cyclopentyl) (N. A. Jasim, R. N. Perutz, B. Procacci and A. C. Whitwood, Chem. Commun., 2014, 50, 3914) demonstrates that the reaction proceeds via an SN2 mechanism. Nucleophilic attack of Pt(0) generates an ion pair consisting of a T-shaped platinum cation with an agostic interaction with a cyclopentyl group and a fluoroaryloxy anion. This ion-pair is converted to a 4-coordinate Pt(ii) product trans-[PtMe(OAr(F))(PCyp3)2]...
October 17, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Starr Dostie, Michel Prévost, Philippe Mochirian, Kashif Tanveer, Nicholas Andrella, Ariana Rostami, Guillaume Tambutet, Yvan Guindon
Nucleoside analogues bearing a fluorine in the C2'-position have been synthesized by SN2-like cyclizations of acyclic thioaminal precursors. This strategy provides access to two scaffolds, D-1',2'-cis thiofuranosides and D-1',2'-trans furanosides, that are difficult to generate using the standard approach for nucleoside synthesis. The addition of silylated nucleobases onto model C2-fluorinated dithioacetal substrates resulted in 1,2-syn diastereoselectivity which is consistent with the C2-F and S-alkyl moiety being in close proximity...
October 13, 2016: Journal of Organic Chemistry
Arantxa Fernandes, David McKay, Scott Sneddon, Daniel M Dawson, Sebastian Lawson, Richard Veazey, Karl R Whittle, Sharon E Ashbrook
An NMR crystallographic approach, involving the combination of (119)Sn NMR spectroscopy, XRD, and DFT calculations, is demonstrated for the characterization of La2Sn2-x Ti x O7 ceramics. A phase change from pyrochlore (La2Sn2O7) to a layered perovskite phase (La2Ti2O7) is predicted (by radius ratio rules) to occur when x ≈ 0.95. However, the sensitivity of NMR spectroscopy to the local environment is able to reveal a significant two-phase region is present, extending from x = 1.8 to ∼0.2, with limited solid solution at the two extremes, in broad agreement with powder XRD measurements...
September 15, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Laura Milena Pedraza-González, Johan Fabian Galindo, Ronald Gonzalez, Andrés Reyes
The solvent effect on the nucleophile and leaving group atoms of the prototypical F(-) + CH3Cl → CH3F + Cl(-) backside bimolecular nucleophilic substitution reaction (SN2) is analyzed employing the reaction force and the atomic contributions methods on the intrinsic reaction coordinate (IRC). Solvent effects were accounted for using the polarizable continuum solvent model. Calculations were performed employing eleven dielectric constants, ε, ranging from 1.0 to 78.5, to cover a wide spectrum of solvents...
October 9, 2016: Journal of Physical Chemistry. A
L Szatkowski, M B Hall
The nickel(i) octaethylisobacteriochlorin anion ([OEiBCh-Ni((I))](-)) is commonly used as a synthetic model of cofactor F430 from Methyl-Coenzyme M Reductase. In this regard, experimental studies show that [OEiBCh-Ni((I))](-) can catalyze dehalogenation of aliphatic halides in DMF solution by a highly efficient SN2 reaction. To better understand this process, we constructed theoretical models of the dehalogenation of chloromethane by a simple nickel(i) isobacteriochlorin anion and compared its reactivity with that of similar Ni((I)) complexes with other porphyrin-derived ligands: porphyrin, chlorin, bactreriochlorin, hexahydroporphyrin and octahydroporphyrin...
September 28, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Emiliano Sorrentino, Stephen J Connon
The first strategy for bringing about highly enantioselective alkylative enolate kinetic resolutions using a simple phase-transfer protocol via SN2 chemistry has been developed. In the presence of a new squaramide-based quaternized cinchona alkaloid-derived catalyst and aqueous base, benzyl, allyl, and propargyl halides react with racemic substituted oxindoles to generate densely functionalized products with the two contiguous stereocenters, one of which is an all-carbon quaternary.
October 4, 2016: Organic Letters
Jeffrey S Cannon, Larry E Overman
Allylic amides, amines, and esters are key synthetic building blocks. Their enantioselective syntheses under mild conditions is a continuing pursuit of organic synthesis methods development. One opportunity for the synthesis of these building blocks is by functionalization of prochiral double bonds using palladium(II) catalysis. In these reactions, nucleopalladation mediated by a chiral palladium(II) catalyst generates a new heteroatom-substituted chiral center. However, reactions where nucleopalladation occurs with antarafacial stereoselectivity are difficult to render enantioselective because of the challenge of transferring chiral ligand information across the square-planar palladium complex to the incoming nucleophile...
October 18, 2016: Accounts of Chemical Research
Zengming Man, Haican Dai, Yinping Shi, Dongdong Yang, Chuan-Ying Li
Sodium iodide is used for the first time as a nucleophile to trap an α-imino rhodium carbene, which triggers a tandem process involving intermolecular nucleophilic attack and intramolecular SN2 reaction. A series of 5-iodo-1,2,3,4-tetrahydropyridines are obtained in high yield, and the synthetic utility of the products is demonstrated in cross-coupling reactions and the construction of biorelated polycyclic compounds.
October 7, 2016: Organic Letters
Martine Gilleron, Marco Lepore, Emilie Layre, Diane Cala-De Paepe, Naila Mebarek, James A Shayman, Stéphane Canaan, Lucia Mori, Frédéric Carrière, Germain Puzo, Gennaro De Libero
Complex antigens require processing within antigen-presenting cells (APCs) to form T cell stimulatory complexes with CD1 antigen-presenting molecules. It remains unknown whether lipids with multi-acylated moieties also necessitate digestion by lipases to become capable of binding CD1 molecules and stimulate T cells. Here, we show that the mycobacterial tetra-acylated glycolipid antigens phosphatidyl-myo-inositol mannosides (PIM) are digested to di-acylated forms by pancreatic lipase-related protein 2 (PLRP2) and lysosomal phospholipase A2 (LPLA2) within APCs...
September 22, 2016: Cell Chemical Biology
Teiichi Murakami, Yukari Sato, Kyoko Yoshioka, Mutsuo Tanaka
A regio- and stereo-controlled, rhodium(II)-catalyzed amidoglycosylation of alcohols has been developed using O-acetylated glycals, trichloroethoxysulfonamide, and iodosobenzene. This one-pot amidoglycosylation was applied to a variety of primary and secondary alcohols to afford the β-O-glycosides with acceptable yields up to 84%. The reaction would proceed via stereoselective intermolecular aziridination of the glycal from the α-face followed by SN2 reaction with alcohol at C-1 from the β-face to give 1,2:2,3-di-trans-substituted isomer only...
September 4, 2016: Carbohydrate Research
Joana Rocha, Félix Cicéron, Daniele de Sanctis, Mickael Lelimousin, Valérie Chazalet, Olivier Lerouxel, Christelle Breton
The plant cell wall is a complex and dynamic network made mostly of cellulose, hemicelluloses and pectins. Xyloglucan, the major hemicellulosic component in Arabidopsis thaliana, is biosynthesized in the Golgi apparatus by a series of glycan synthases and glycosyltransferases before export to the wall. A better understanding of the xyloglucan biosynthetic machinery will give clues toward engineering plants with improved wall properties or designing novel xyloglucan-based biomaterials. The xyloglucan-specific α-2-fucosyltransferase FUT1 catalyzes the transfer of fucose from GDP-fucose to terminal galactosyl residues on xyloglucan side chains...
September 16, 2016: Plant Cell
Michael E Jung, Daniel L Sun, Timothy A Dwight, Peiyuan Yu, Wei Li, K N Houk
The efficient synthesis of trans-2-ethenylcyclopropyl aryl ketones via an intramolecular SN2-like displacement of an allylic ester is reported. A novel 1,5-acyl shift process is also observed that contributes to the product mixture. Theoretical calculations provide a rationale for the observed product ratio.
October 7, 2016: Organic Letters
Lukas Pfeifer, Keary M Engle, George W Pidgeon, Hazel A Sparkes, Amber L Thompson, John M Brown, Véronique Gouverneur
Hydrogen bonding with fluoride is a key interaction encountered when analyzing the mode of action of 5'-fluoro-5'-deoxyadenosine synthase, the only known enzyme capable of catalyzing the formation of a C-F bond from F(-). Further understanding of the effect of hydrogen bonding on the structure and reactivity of complexed fluoride is therefore important for catalysis and numerous other applications, such as anion supramolecular chemistry. Herein we disclose a detailed study examining the structure of 18 novel urea-fluoride complexes in the solid state, by X-ray and neutron diffraction, and in solution phase and explore the reactivity of these complexes as a fluoride source in SN2 chemistry...
October 4, 2016: Journal of the American Chemical Society
Robert J Wilson, Lies Broeckaert, Fabian Spitzer, Florian Weigend, Stefanie Dehnen
Reaction of the binary Zintl anion (Sn2 Sb2 )(2-) with the β-diketiminato complex [LCu(NCMe)] (L=nacnac=[(N(C6 H3 (i) Pr2 -2,6)C(Me))2 CH](-) ) in ethylenediamine or DMF affords the ternary cluster dimer {[CuSn5 Sb3 ](2-) }2 (1) as its [K(crypt-222)](+) salt. The chemical formulation of 1 is supported by energy-dispersive X-ray spectroscopy (EDX) and quantum chemical calculations. Each monomeric part of the dimer represents a trimetallic "[CuSn5 Sb3 ](2-) " cluster, with an architecture in between a tricapped trigonal prism and a capped square antiprism...
September 19, 2016: Angewandte Chemie
Symon Gathiaka, Brittany Boykin, Tamar Cáceres, Joan M Hevel, Orlando Acevedo
Protein arginine methyltransferases (PRMTs) catalyze the post-translational methylation of specific arginyl groups within targeted proteins to regulate fundamental biological responses in eukaryotic cells. The major Type I PRMT enzyme, PRMT1, strictly generates monomethyl arginine (MMA) and asymmetric dimethylarginine (ADMA), but not symmetric dimethylarginine (SDMA). Multiple diseases can arise from the dysregulation of PRMT1, including heart disease and cancer, which underscores the need to elucidate the origin of product specificity...
October 15, 2016: Bioorganic & Medicinal Chemistry
Carlos A Méndez-Cuesta, Miguel Ángel Herrera-Rueda, Sergio Hidalgo-Figueroa, Hugo Tlahuext, Rosa Moo-Puc, Juan Bautista Chale-Dzul, Manuel Chan-Bacab, Benjamín Otto Ortega-Morales, Emanuel Hernández-Núñez, Oscar Méndez-Lucio, José L Medina-Franco, Gabriel Navarrete-Vazquez
BACKGROUND: Propamidine, an antiseptic aromatic diamidine is a toxic compound with potential use as antiprotozoal drug. On the other hand, benzimidazole derivatives have shown excellent antiparasitic effects. We designed hybrid molecules between propamidine and benzimidazole in order to retain the antiprotozoal action, but decreasing the toxic effect of the molecule. Objetive: Design and prepare 12 hybrids from propamidine and benzimidazole for testing their antiparasitic effect over three protozoa: Giardia intestinalis, Trichomonas vaginalis and Leishmania Mexicana, as well as conduct several in silico simulations such as toxicological profile, molecular docking and molecular dynamics in order to understand their potential mode of action...
August 11, 2016: Medicinal Chemistry
Nathália F Carvalho, Josefredo R Pliego
Fluorinated organic molecules are playing an increased role in the area of pharmaceuticals and agrochemicals. This fact demands the development of efficient catalytic fluorination processes. In this paper, we have designed a new crown ether with four hydroxyl groups strategically positioned. The catalytic activity of this basic scaffold was investigated with high levels of electronic structure theory, such as the ONIOM approach combining MP4 and MP2 methods. On the basis of the calculations, this new structure is able to solubilize potassium fluoride in toluene solution much more efficiently than 18-crown-6 (18C6)...
September 16, 2016: Journal of Organic Chemistry
Chengxi Li, Yuanyuan Zhang, Qi Sun, Tongnian Gu, Henian Peng, Wenjun Tang
We herein report a transition-metal-free cross-coupling between secondary alkyl halides/mesylates and aryl/alkenylboronic acid, providing expedited access to a series of nonchiral/chiral coupling products in moderate to good yields. Stereospecific SN2-type coupling is developed for the first time with alkenylboronic acids as pure nucleophiles, offering an attractive alternative to the stereospecific transition-metal-catalyzed C(sp(2))-C(sp(3)) cross-coupling.
August 31, 2016: Journal of the American Chemical Society
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