- Synthesis and physicochemical properties of chelating sorbents containing functional groups of N-aryl-3-aminopropionic acids
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Two types of chelating sorbents with different types of addition of iminodipropionate groups to a polymeric matrix were synthesized: carboxyethylated aminopolystyrene (sorbent 1) based on linear polystyrene and carboxyethylaminomethylpolystyrene (sorbent 2) based on the copolymer of styrene and divinylbenzene. The ionization constants and concentrations of functional groups of the sorbents (exchange capacity for hydrogen ions) were determined. The sorbents exhibit high selectivity for copper(II) ions with the maximum of sorption from ammonia-acetate buffer solutions lying in a range of pH 5.0-7.5. The time needed for a solution of copper(II)-sorbent system with continuous stirring to reach exchange equilibrium is 3.5 and 2 h for sorbents 1 and 2, respectively. The exchange capacity for copper(II) ions is 2.54 and 0.10 mmol g-1, respectively. Springer Science+Business Media, Inc. 2006.
- Neudachina,Yatluk,Baranova,Pestov,Vshivkov,Plekhanova,Zorina
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- Amido Complexes of Iridium with a PNP Pincer Ligand: Reactivity toward Alkynes and Hydroamination Catalysis
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The pincer ligand HN(CH2CH2PPh2)2 (1; PNHP) reacted with [{Ir(μ-X)(cod)}2] (X = Cl, OMe), affording complexes [fac-(PNHP)Ir(cod)]Cl (2) and [fac-(PNP)Ir(cod)] (3), respectively. The X-ray molecular structure of 2 showed that the PNP ligand coordinates in a facial fashion, with the N atom in an axial site and both P atoms coordinated in the equatorial plane. Compound 1 is able to protonate the hydroxo bridges in the complex [{Ir(μ-OH)(coe)2}2] forming the new amido complex [mer-(PNP)Ir(coe)] (4). Complex 4 is an extremely air sensitive compound, as confirmed by the isolation of the oxo complex [mer-(PNP)Ir(σ2-O2)] (8) from its interaction with air. Protonation of 4 with HBF4 afforded the corresponding amino complex [mer-(PNHP)Ir(coe)]BF4 (5), whose molecular structure enlightened by X-ray crystallography confirmed the PNP ligand to be coordinated in a meridional fashion. The coe ligand in 4 is tightly bonded to iridium; however, under an atmosphere of ethylene at 60 °C or with acrylonitrile at 70 °C complex 4 exchanges the olefin, affording compounds [mer-(PNP)Ir(σ2-C2H4)] (6) and [mer-(PNP)Ir(σ2-C2H3CN)] (7), respectively. Interaction of 4 with alkynes depends on the nature of the substrate; therefore, methyl phenylpropiolate reacted with 4, affording the adduct [mer-(PNP)Ir(σ2-PhCCC(O)OMe)] (9), while the parent acetylene undergoes a double C-H activation, affording the Ir(III) complex [fac-(PNHP)IrH(Ca‰?CH)2] (10). A DFT theoretical analysis of this transformation supports a metal-ligand cooperation mechanism. The reaction starts by deprotonation of an alkyne moiety by the PNP ligand followed by oxidative addition of the C-H bond to the metal of a second alkyne molecule. Additionally, we have tested complex 4 as a catalyst for the addition of gaseous ammonia to activated unsaturated substrates. A DFT theoretical analysis disclosed the operative mechanism on these organic transformations, which starts with a nucleophilic attack of ammonia to the bound alkyne, hydrogen migration to the metal, and reductive elimination steps.
- Hermosilla, Pablo,López, Pablo,García-Ordunìa, Pilar,Lahoz, Fernando J.,Polo, Víctor,Casado, Miguel A.
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- Palladium nanocatalysts in glycerol: Tuning the reactivity by effect of the stabilizer
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Palladium nanoparticles (PdNPs) prepared in neat glycerol containing TPPTS (tris(3-sulfophenyl)phosphine trisodium salt) or cinchona-based alkaloids (cinchonidine, quinidine) as capping agents, were applied as catalysts in fluoride-free Hiyama couplings and conjugate additions with the aim of evaluating the influence of the stabilizer in the catalytic reactivity. Therefore, PdNPs stabilized by phosphine favored C–C cross-couplings, whereas those containing alkaloids showed enhanced suitability for C–C homo-couplings and conjugate additions. The metal/stabilizer coordination mode, i.e. Pd–P dative bond and π-π interaction between quinoline moiety and palladium surface, is certainly key for the stabilization of different active metallic species and then promoting distinctive catalytic pathways.
- Reina, Antonio,Serrano-Maldonado, Alejandro,Teuma, Emmanuelle,Martin, Erika,Gómez, Montserrat
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- Parent-amido (NH2) palladium(II) complexes: Synthesis, reactions, and catalytic hydroamination
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The treatment of [PdL3(NH3)](OTf)n (n = 1; L3 = (PEt3)2(Ph), (2,6-(Cy2PCH2)2C6H3), n = 2; L3 = (dppe)(NH3)) with NaNH2 in tetrahydrofuran at ambient temperature or -78 °C afforded the dimeric and monomeric parent-amido palladium(II) complexes anti-[Pd(PEt3)(Ph)(μ-NH2)]2 (1), [Pd(dppe)(μ-NH2)]2(OTf)2 (2), and Pd(2,6-(Cy2PCH2)2C6H3)(NH2) (3), respectively. The molecular structures of the amido-bridged (μ-NH2) dimeric complexes 1 and 2 were determined by single-crystal X-ray crystallography. The monomeric amido complex 3 reacted with trace amounts of water to give a hydroxo complex, Pd(2,6-(Cy2PCH2)2C6H3)(OH) (4). Exposing complex 3 to an excess of water resulted in the complete conversion of the complex into two species [Pd(2,6-(Cy2PCH2)2C6H3)(OH2)]+ and [Pd(2,6-(Cy2PCH2)2C6H3)(NH3)]+. Complex 3 reacted with diphenyliodonium triflate ([Ph2I]OTf) to give the aniline complex [Pd(2,6-(Cy2PCH2)2C6H3)(NH2Ph)]OTf. The reaction of 3 with phenylacetylene (HCCPh) yielded a palladium(II) acetylenide Pd(2,6-(Cy2PCH2)2C6H3)(CCPh) (5), quantitatively, along with the liberation of ammonia. The reaction of 3 with dialkyl acetylenedicarboxylate yielded diastereospecific palladium(II) vinyl derivatives (Z)-Pd(2,6-(Cy2PCH2)2C6H3)(CRCR(NH2)) (R = CO2Me (6a), CO2Et (6b)). The reaction of complexes 6a and 6b with p-nitrophenol produced Pd(2,6-(Cy2PCH2)2C6H3)(OC6H4-p-NO2) (7) and cis-CHRCR(NH2), exclusively. Reactions of 3 with either dialkyl maleate (cis-(CO2R)CHCH(CO2R)) (R = CH3, CH2CH3) or cis-stilbene (cis-CHPhCHPh) did not result in any addition product. Instead, isomerization of the cis-isomers to the trans-isomers occurred in the presence of catalytic amounts of 3. Complex 3 reacted with a stoichiometric amount of acrylonitrile (CH2CHCN) to generate a metastable insertion product, Pd(2,6-(Cy2PCH2)2C6H3)(CH(CN)CH2NH2). On the other hand, the reaction of 3 with an excess of acrylonitrile slowly produced polymeric species of acrylonitrile. The catalytic hydroamination of olefins with NH3 was examined in the presence of Pd(2,6-(Cy2PCH2)2C6H3)(OTf), producing a range of hydroaminated products of primary, secondary, and tertiary amines with different molar ratios of more than 99% overall yield. A mechanistic feature for the observed catalytic hydroamination is described with regard to the aminated derivatives of palladium(II).
- Kim, Youngwon,Park, Soonheum
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p. 614 - 629
(2016/06/01)
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- Synthesis and structure-activity relationship studies of CD4 down-modulating cyclotriazadisulfonamide (CADA) analogues
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HIV attachment via the CD4 receptor is an important target for developing novel approaches to HIV chemotherapy. Cyclotriazadisulfonamide (CADA) inhibits HIV at submicromolar levels by specifically down-modulating cell-surface and intracellular CD4. An effective five-step synthesis of CADA in 30% overall yield is reported. This synthesis has also been modified to produce more than 50 analogues. Many tail-group analogues have been made by removing the benzyl tail of CADA and replacing it with various alkyl, acyl, alkoxycarbonyl and aminocarbonyl substituents. A series of sidearm analogues, including two unsymmetrical compounds, have also been prepared by modifying the CADA synthesis, replacing the toluenesulfonyl sidearms with other sulfonyl groups. Testing 30 of these compounds in MT-4 cells shows a wide range of CD4 down-modulation potency, which correlates with ability to inhibit HIV-1. Three-dimensional quantitative structure-activity relationship (3D-QSAR) models were constructed using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) approaches. The X-ray crystal structures of four compounds, including CADA, show the same major conformation of the central 12-membered ring. The solid-state structure of CADA was energy minimized and used to generate the remaining 29 structures, which were similarly minimized and aligned to produce the 3D-QSAR models. Both models indicate that steric bulk of the tail group, and, to a lesser extent, the sidearms mainly determine CD4 down-modulation potency in this series of compounds.
- Bell, Thomas W.,Anugu, Sreenivasa,Bailey, Patrick,Catalano, Vincent J.,Dey, Kaka,Drew, Michael G. B.,Duffy, Noah H.,Jin, Qi,Samala, Meinrado F.,Sodoma, Andrej,Welch, William H.,Schols, Dominique,Vermeire, Kurt
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p. 1291 - 1312
(2007/10/03)
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- Polynuclear branched tetrazole systems. 2*. New 2-(5-tetrazolyl) ethyl podands and their NH-acidity
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Nine new polynuclear 2-(5-tetrazolyl)ethyl podands have been obtained by the azidation of the corresponding nitriles. Using Bjerrum distribution functions, the values of pKa1, pKa 2, pKa3, and pKa4 have been determined by a potentiometric method for 14 polynuclear tetrazoles in aqueous and aqueous methanolic solution. The found values lie in the range from 3.5 to 7.5 pH units. The overall rules and the sequence of the ionization of the spatially separated tetrazole fragments in these podand systems are discussed.
- Zubarev,Bezklubnaya,Pyartman,Trifonov,Ostrovskii
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p. 1317 - 1325
(2007/10/03)
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- Syntheses, conformations, and basicities of bicyclic triamines
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The multistep syntheses of several bicyclic triamines are described, all of which have an imbedded 1,5,9-triazacyclododecane ring. In 1,5,9-triazabicyclo[7.3.3]pentadecanes 12, 13, 15, and 16, two nitrogens are bridged by three carbons. The monoprotonated forms of these triamines are highly stabilized by a hydrogen-bonded network involving the bridge and both bridgehead nitrogens, producing a difference of more than 8 pKa units in acidities of their monoprotonated and diprotonated forms. The one- and zero-carbon bridges in 1,5,9-triazabicyclo[9.1.1]tridecane (23) and 7-methyl-1,5,9-triazabicyclo[5.5.0]dodecane (39) do not enhance the stabilities of their monoprotonated forms. X-ray crystal structures and computational studies of 12·HI and 16·HI reveal similar, but somewhat weaker, hydrogen-bonded networks, relative to 15·HI. The activation free energies for conformational inversion of 13·HI (14.4 ± 0.2 kcal/mol), 16·HI (15.0 ± 0.1 kcal/mol) and 16 (8.8 ± 0.3 kcal/mol) were measured by variable-temperature 1H and 13C NMR spectroscopy. These experimental barriers give an estimate of 6.2 kcal/mol for the strength of the bifurcated hydrogen bond between the bridge nitrogen and cavity proton in 16·HI. Computational studies support the hypothesis that N-inversion occurs in an open conformation, leading to an estimate of 10.32 kcal/mol for the enthalpy of the bifurcated hydrogen bond in 16·HI in the gas phase.
- Bell, Thomas W.,Choi, Heung-Jin,Harte, William,Drew, Michael G. B.
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p. 12196 - 12210
(2007/10/03)
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- Anti-viral triaza compounds and compositions
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The invention relates to a family of new synthetic triamine compounds which can be used in antiviral pharmaceutical compositions.
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Page column 6 - 7
(2010/01/30)
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- Scavenger assisted combinatorial process for preparing libraries of amides, carbamates and sulfonamides
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This invention relates to a novel solution phase process for the preparation of amide, carbamate, and sulfonamide combinatorial libraries. These libraries have utility for drug discovery and are used to form wellplate components of novel assay kits.
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- Irreducible Analogues of Mevaldic Acid Coenzyme A Hemithioacetal as Potential Inhibitors of HMG-CoA Reductase. Synthesis of a Carbon-Sulfur Interchanged Analogue of Mevaldic Acid Pantetheine Hemithioacetal
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Synthesis of (3,5)-threo- and (3,5)-erythro-6-propanamido>methyl>thio>-3,5-dihydroxy-3-methylhexanoic acid, threo- and erythro-7d, as well as the corresponding δ-lactones, cis- and trans-13a, is described.The key step in the syntheses is the selective amidomethylation of the sulfhydryl in cis- or trans-4-hydroxy-6-(mercaptomethyl)-4-methyl-3,4,5,6-tetrahydro-2H-pyran-2-one, cis- or trans-13d, with N-(hydroxymethyl)pantothenamide, 23.The target compounds are the first in a class being explored as potential inhibitors of HMG-CoA reductase, the key regulated enzyme in cholesterol biosynthesis.They are structurally identical with mevaldic acid pantetheine hemithioacetal, 2b (a known substrate for the enzyme and an analogue of the enzyme-bound intermediate 2a), but they are unable to be reduced by the enzyme because the labile C-S bond in 2b has been replaced with a stable C-C bond in 7d by interchanging a carbon and a sulfur atom.
- Fischer, Gordon C.,Turakhia, Rajesh H.,Morrow, Cary J.
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p. 2011 - 2019
(2007/10/02)
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- Studies on the effect of the neurolathyrogenic substance beta,beta'-iminodipropionitrile on the branchiopode Artemia salina (author's transl)
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beta,beta'-Iminodipropionitrile (IDPN) is a neurotoxic substance, which induces choreiform movements for life in rats and mice. As for the phenotype this seems to be a suitable animal model for the comparison with Huntington's chorea in man. In our experiments we have tested the effect of IDPN on different developmental stages of the branchiopode artermia salina. One-day old nauplii show the strongest reaction to the substance. As little as 10(-5) g IDPN/l culture medium induces in one-day old nauplii a characteristically altered swimming behavior. This behavioral response of the one-day old nauplii may possibly serve as a basis for a simple qualitative biological assay for the detection of IDPN or its effective metabolite, respectively.
- Schneider,Ruether,Klapproth,Schott
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p. 592 - 593
(2007/10/02)
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