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201.
Stephen L. De Wall Eric S. Meadows Clare L. Murray Hossein Shabany George W. Gokel 《Supramolecular chemistry》2013,25(1):13-22
Abstract A family of tris(macrocyclic) compounds of the form sidearm<N18N>Cn<N18N>Cn<N18N>sidearm, has been prepared, characterized chemically, and assayed by dynamic 23Na-NMR for the ability to transport sodium cations in a mixed phosphatidylglycerol/phosphatidylcholine vesicle system. A number of control experiments have been conducted that reinforce the hypothesis that cation transport occurs by a channel mechanism. The tris(macrocycle) channels proved to be functional at a level of 25–50% of that found for the natural pentadecapeptide channel gramicidin. Fluorescence data confirm the expected position of the channel within the bilayer. 相似文献
202.
PaulW. Finn Morwena Bandara Chris Butcher Angela Finn Ruth Hollinshead Nagma Khan Norman Law Sreenivasa Murthy Rosario Romero Clare Watkins Victor Andrianov RasmaM. Bokaldere Klara Dikovska Vija Gailite Einars Loza Irina Piskunova Igor Starchenkov Maxim Vorona Ivars Kalvinsh 《Helvetica chimica acta》2005,88(7):1630-1657
Inhibition of the enzyme histone deacetylase (HDAC) is emerging as a novel approach to the treatment of cancer. A series of novel sulfonamide derivatives were synthesized and evaluated for their ability to inhibit human HDAC. Compounds were identified which are potent enzyme inhibitors, with IC50 values in the low nanomolar range against enzyme obtained from HeLa cell extracts, and with antiproliferative effects in cell culture. Extensive characterization of the structure–activity relationships of this series identified key requirements for activity. These include the direction of the sulfonamide bond and substitution patterns on the central phenyl ring. The alkyl spacer between the aromatic head group and the sulfonamide functionality also influenced the HDAC inhibitory activity. One of these compounds, m 11.1 , also designated PXD101, has entered clinical trials for solid tumors and haematological malignancies. 相似文献
203.
Aline de Souza Ramos Joyce Benzaquem Ribeiro Leonardo Vazquez Selma Gomes Ferreira Leite Francisco Radler de Aquino Neto 《Tetrahedron letters》2009,50(52):7362-6129
The enantioselective reduction of ethyl benzoylacetate (EBA) into ethyl (S)-3-hydroxy-3-phenylpropanoate (S-HPPE) by nine yeast strains and three filamentous fungi strains is described. The conversion obtained was in the range 0-89% and the enantiomeric excess was 100% in many cases. Conversion levels were higher when the reduction was performed with microorganisms immobilized in calcium alginate and enantioselectivity remained excellent. Some reaction’s conditions of bioreduction by immobilized cells of Rhodotorula rubra were studied using a 25-2 fractional factorial design. 相似文献
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205.
Maycow Marcos L. de Azevedo Márcia M. Cascaes Eloisa Helena A. Andrade Maria das Graças B. Zoghbi Joyce Kelly R. da Silva 《Natural product research》2019,33(4):506-515
Chemical composition of the methanol extract of Myrciaria floribunda leaves was investigated. The nor-lupane triterpenoids platanic acid and messagenic I acid were identified, along with other known triterpenoids (betulinic aldehyde, ursolic acid acetate and betulinic acid), a new lupane triterpenoid (2α,6α,30-trihydroxybetulinic acid) and the flavonoids catechin, quercetrin and mirycitrin. The structures were determined by spectroscopic methods (NMR, LC-MS, GC-MS). The major isolated compound was betulinic acid. The methanol extract and 2α,6α,30-trihydroxybetulinic acid were evaluated for their DPPH scavenging potential. The tested triterpenoid was one hundred times more active than betulinic acid, but less active than the extract. Screening for antimicrobial activity showed that the methanol extract was active against Staphylococcus aureus and Escherichia coli, but inactive against Candida albicans and Candida krusei, while 2α,6α,30-trihydroxybetulinic acid was inactive to all tested microorganisms. 相似文献
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208.
A compound with a linear trinuclear copper(II) cation, [Cu3(μ-protan)2](ClO4)2·H2O (protanH2 = 3,7-bis(3-hydroxypropyl)-1,3,5,7-tetraazabicyclo[3,3,1]-nonane) is formed by reaction of copper(II) perchlorate, 3-aminopropanol, ammonia and methanal. The cation is approximately centrosymmetrical with Cu?Cu = 2.9870(5) and 2.9485(5) Å. The terminal copper(II) ions are coordinated by nitrogen atoms 3 and 7 of the tetraazabicycle (Cu–Nmean = 2.021(5) Å) and the two oxygen atoms of the 3,7-bis(3-olatopropyl) substituents (Cu–Omean = 1.911(3) Å), which also act as bridging groups to the central copper(II) ion (Cu–Omean = 1.926(4) Å). The cation is both helically twisted (dihedral angle N3?N7?N3′?N7′ = 20(1)°) and bent (angle Cu?Cu?Cu = 171(1)°). The copper(II) ions have tetrahedrally twisted square planar primary coordination, with perchlorate ion oxygen atoms weakly coordinated axially to the two terminal copper(II) ions, on opposite sides of the “plane” of the molecule, while the central copper(II) ion is weakly coordinated axially by a water molecule, with all axial Cu–O distances ca. 2.9 Å. One N·CH2·CH2·CH2·O chelate ring for each protan2− ligand shows conformational disorder and the perchlorate ions show rotational disorder. Partial hydrolysis of the protan2− compound gave a compound [{Cu(μ-protan)}Cu(OH)2](ClO4)2·0.5(EtOH) which has a dinuclear cation, with one copper(II) ion in square-planar coordination by tetradentate protan2− and the other in square-planar coordination by the two bridging oxygen atoms of the protan2− ligand and by two hydroxide ions, with Cu?Cu = 3.045(1) Å. With differing mole ratios of the same reactants compounds of the dinuclear cation [{Cu(μ-pta)}2]2+ (ptaH = 3(3-hydroxypropyl)-1,3,5,7-tetraazabicyclo[3,3,1]nonane) are formed. 相似文献
209.
Reaction of diamine-bis(phenol) ligands containing a mixture of N-methyl and N,N′-dimethyl-N,N-bis(2-hydroxy-3,5-dimethylbenzyl)ethylenediamine, H2L1 and H2L3, with [Ti(OCHMe2)4 in absolute ethanol under reflux without exclusion of air and moisture gives [(L1)Ti (OEt–O–Ti(OEt)(L1)] (1). [(L3)Ti(OEt)–O–Ti(OEt)(L3)] (2) forms when the remaining solution containing [(L3)Ti(OEt)2] (3) (characterised by X-ray crystallography) is hydrolysed with H2O. For the N-methyl and N,N′-dimethyl ligand mixture H2L2 and H2L4, which contain tert-butyl groups on the ortho-positions of the aryl rings, [(L2)Ti(OEt)–O–Ti(OEt)(L2)] (4) forms much more slowly and [(L4)Ti(OEt)2] (5) does not hydrolyse when H2O is added. When the N-protonated ligand N,N-bis(2-hydroxy-3-methyl-5-tert-butylbenzyl)ethylenediamine, H2L5, is used, rapid hydrolysis to two isomers of [(L5)Ti(OEt–O–Ti(OEt)(L5)] (6) occurs without addition of water. For N,N-bis(2-hydroxy-3,5-di-tert-butylbenzyl)ethylenediamine, H2L6, hydrolysis to [(L6)Ti(OEt)–O–Ti(OEt)(L6)] (7) occurs slowly when H2O is added. For pendant NMe2 ligand N,N-dimethyl-N′,N′-bis(2-hydroxy-3-methyl-5-tert-butylbenzyl)ethylenediamine, H2L7, the hydrolysis reaction readily gives [(L7)Ti(OEt)–O–Ti(OEt)(L7)] (8) for which an X-ray crystal structure was obtained. The ortho-tert-butyl ligand derivative H2L8 formed a complex analysing as [(L8)Ti(OEt)–O–Ti(OEt)(L8)] (9) which could not be studied further due to insolubility. Pendant pyridine ligand N-(2-pyridylmethyl)-N,N-bis(2′-hydroxy-3′-methyl-5′-tert-butylbenzyl)amine, H2L9, apparently forms isomers of [(L9)Ti(OEt)–O–Ti(OEt)(L9)] and possibly [{(L9)Ti(O)}2] from [(L9)Ti(OEt)2] (10). The ortho-tert-butyl ligand derivative H2L10 formed [(L10)Ti(OEt)–O–Ti(OEt)(L10)] (11) for which an X-ray crystal structure was obtained. 相似文献
210.
Andrew G. Tennyson Dr. Robert J. Ono Todd W. Hudnall Dr. Dimitri M. Khramov Dr. Joyce A. V. Er Justin W. Kamplain Dr. Vincent M. Lynch Dr. Jonathan L. Sessler Prof. Christopher W. Bielawski Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(1):304-315
Reaction of bromanil with N,N′‐dimesitylformamidine followed by deprotonation with NaN(SiMe3)2 afforded 1,1′,3,3′‐tetramesitylquinobis(imidazolylidene) ( 1 ), a bis(N‐heterocyclic carbene) (NHC) with two NHC moieties connected by a redox active p‐quinone residue, in 72 % yield of isolated compound. Bimetallic complexes of 1 were prepared by coupling to FcN3 ( 2 ) or FcNCS ( 3 ; Fc=ferrocenyl) or coordination to [M(cod)Cl] ( 4 a or 4 b , where M=Rh or Ir, respectively; cod=1,5‐cyclooctadiene). Treatment of 4 a and 4 b with excess CO(g) afforded the corresponding [M(CO)2Cl] complexes 5 a and 5 b , respectively. Analysis of 2 – 5 by NMR spectroscopy and X‐ray diffraction indicated that the electron‐deficient quinone did not significantly affect the inherent spectral properties or coordination chemistry of the flanking imidazolylidene units, as compared to analogous NHCs. Infrared spectroscopy and cyclic voltammetry revealed that decreasing the electron density at MLn afforded an increase in the stretching energy and a decrease in the reduction potential of the quinone, indicative of metal–quinone electronic interaction. Differential pulse voltammetry and chronoamperometry of the metal‐centered oxidations in 2 – 4 revealed two single, one‐electron peaks. Thus, the metal atoms bound to 1 are oxidized at indistinguishable potentials and do not appear electronically coupled. However, the metal–quinone interaction was used to increase the electron density at coordinated metal atoms. Infrared spectroelectrochemistry revealed that the average νCO values for 5 a and 5 b decreased by 14 and 15 cm?1, respectively, upon reduction of the quinone embedded within 1 . These shifts correspond to 10 and 12 cm?1 decreases in the Tolman electronic parameter of this ditopic ligand. 相似文献