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961.
A novel ring C aromatic diterpene (4) has been prepared in three steps from natural (+)-manool (1). The structure and anticancer activity data for 4 has been investigated. This key intermediate (4) was easily transformed into 7-deoxo nimbidiol dimethyl ether (8). The present work represents the first formal synthesis of (+)-nimbidiol (10). 相似文献
962.
Jorge Manzur 《Transition Metal Chemistry》1986,11(6):220-223
Summary 2,2-Dipyridylmethane reacts with iron(II), cobalt(II), nickel(II) and copper(II) salts to form complexes of a varied stereochemistry depending upon the metal and the anion involved,Pseudo-tetrahedral, octahedral and square-planar complexes containing this ligand have been prepared and characterized by elemental analysis, conductivity data, room temperature magnetic moments and electronic spectra. 相似文献
963.
Gomes JR Sousa EA Gonçalves JM Monte MJ Gomes P Pandey S Acree WE Ribeiro da Silva MD 《The journal of physical chemistry. B》2005,109(33):16188-16195
The standard enthalpy of formation and the enthalpy of sublimation of crystalline 2-hydroxyphenazine-di-N-oxide, at T = 298.15 K, were determined from isoperibol static bomb combustion calorimetry and from Knudsen effusion experiments, as -76.7 +/- 4.2 kJ.mol(-1) and 197 +/- 5 kJ.mol(-1), respectively. The sum of these two quantities gives the standard enthalpy of formation in the gas-phase for this compound, delta(f)H(m)degrees(g) = 120 +/- 6 kJ.mol(-1). This value was combined with the gas-phase standard enthalpy of formation for 2-hydroxyphenazine retrieved from a group estimative method yielding the mean (N-O) bond dissociation enthalpy, in the gas-phase, for 2-hydroxyphenazine-di-N-oxide. The result obtained with this strategy is (DH(m)degrees (N - O)) = 263 +/- 4 kJ.mol(-1), which is in excellent agreement with the B3LYP/6-311+G(2d,2p)//B3LYP/6-31G(d) computed value, 265 kJ.mol(-1). 相似文献
964.
Ana María García Jorge Manzur Andrs Vega 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(7):m335-m337
The title compund, [Cu2(OH)2(C22H25N3)2](ClO4)2, is a copper(II) dimer, with two [CuL]2+ units [L is bis(6‐methyl‐2‐pyridylmethyl)(2‐phenylethyl)amine] bridged by hydroxide groups to define the {[CuL](μ‐OH)2[CuL]}2+ cation. Charge balance is provided by perchlorate counter‐anions. The cation has a crystallographic inversion centre halfway between the CuII ions, which are separated by 3.0161 (8) Å. The central core of the cation is an almost regular Cu2O2 parallelogram of sides 1.931 (2) and 1.935 (2) Å, with a Cu—O—Cu angle of 102.55 (11)°. The coordination geometry around each CuII centre can be best described as a square‐based pyramid, with three N atoms from L ligands and two hydroxide O atoms completing the coordination environment. Each cationic unit is hydrogen bonded to two perchlorate anions by means of hydroxide–perchlorate O—H...O interactions. 相似文献
965.
A new reversed-phase high-performance liquid chromatography approach to the production of analytical peptide maps by pre-column derivatization using phenylisothiocyanate is described. Tryptic peptide digests were derivatized with phenyl isothiocyanate to form the phenylthiocarbamyl peptides followed by reversed-phase high-performance liquid chromatographic analysis. The phenylthiocarbamyl peptides were separated by reversed-phase high-performance liquid chromatography with the conventional gradient elution system of water-acetonitrile containing trifluoroacetic acid. The sensitivity of detection of these peptide derivatives was within the range 5-10 pmol with a constant baseline at 254-260 nm. The isolated phenylthiocarbamyl peptides can be subjected to automatic Edman degradation. The effectiveness of this method was exemplified by microsequencing of phenylthiocarbamyl peptides isolated from tryptic digests of three different proteins: alpha-lactalbumin, beta-lactoglobulin and a lambda light-chain immunoglobulin. 相似文献
966.
Single noble metal permanent modifiers such as, Rh, Ir, and Ru, as well as mixed tungsten plus noble metal (W-Rh, W-Ru, W-Ir) permanent modifiers thermally deposited on the integrated platform of transversally heated graphite atomizer were employed for the determination of arsenic in sludges, soils, sediments, coals, ashes and waters by electrothermal atomic absorption spectrometry. Microwave digests of solid samples and water samples were employed for obtaining the analytical characteristics of the methods with different permanent modifiers. The performance of the modifiers for arsenic determination in the real samples depended strongly on the type of permanent modifier chosen. The single noble metal (Rh, Ir and Ru) permanent modifiers were suitable for the analyte determinations in simpler matrices such as waters (recoveries of certified values 95-105%), but the analyte recoveries of certified values in sludges, soils, sediments, coals, and ashes were always lower than 90%. On the other hand, for the determination of arsenic, using W-Rh, W-Ru, and W-Ir permanent modifiers presented recoveries of certified values within 95-105% for all the samples. Long-term stability curves obtained for the determination of arsenic in environmental samples with different permanent modifiers (Rh, Ir, Ru, W-Rh, W-Ir, W-Ru) showed that the improvement in the tube lifetime depends on the tungsten deposit onto the platform. The tungsten plus noble metal permanent modifier presents a tube lifetime of at least 35% longer when compared with single permanent modifier. The results for the determination of As employing different permanent modifiers in the samples were in agreement with the certified reference materials, since no statistical differences were found after applying the paired t-test at the 95% confidence level. 相似文献
967.
968.
Cámpora J Palma P del Río D López JA Valerga P 《Chemical communications (Cambridge, England)》2004,(13):1490-1491
Whereas the reaction of the anionic palladium metallacycle [K[Pd(CH2CMe2-o-C6H4)(kappa2-Tp)]] with CH2Cl2 leads to the isolation of the stable Pd(IV) chloromethyl complex [Pd(CH2CMe2-o-C6H4)(kappa3-Tp)(CH2Cl)], the analogous reactions with CH2Br2 and CH2I2 give rise to the six membered metallacycles [Pd(CH2CMe2-o-C6H4(CH2))(kappa3-Tp)X](X = Br or I), as a result of the formal insertion of CH2 into the Pd-C(aryl) bond. 相似文献
969.
Ilton L Alcantara Paulo S Roldan Gustavo R Castro Fabrício V Moraes Fábio A Silva Cilene C F Padilha Jorge D Oliveira Pedro M Padilha 《Analytical sciences》2004,20(7):1029-1032
A rapid and sensitive method was developed to determine trace levels of Cd2+ ions in an aqueous medium by flame atomic absorption spectrometry, using on-line preconcentration in a mini-column packed with 100 mg of 2-aminothiazol modified silica gel (SiAT). The Cd2+ ions were sorbed at pH 5.0. The preconcentrated Cd2+ ions were directly eluted from the column to the spectrometer's nebulizer-burner system using 100 microL of 2 mol L(-1) hydrochloric acid. A retention efficiency of over 95% was achieved. The enrichment factor (calculated as the ratio of slopes of the calibration graphs) obtained with preconcentrations in a mini-column packed with SiAT (A = -1.3 x 10(-3) + 1.8 x 10(-3)[Cd2+]) and without preconcentrations (A = 4 x 10(-5) + 3.5 x 10(-5)[Cd2+]), was 51 and the detection limit calculated was 0.38 microg L(-1). The preconcentration procedure was applied to determine trace levels of Cd in river water samples. The optimum preconcentration conditions are discussed herein. 相似文献
970.
Molecular dynamics simulations of monoclinic (P21/b) hydroxy- and chlorapatite were undertaken in the range 498 K < T < 1298 K, and for pressures up to 7.5 GPa. The all-atom Born–Huggins–Mayer force field, that had been previously used to successfully describe the room temperature isotherms of both compounds, was also used in this work. The isothermal sets of p–V data generated by simulation were each fitted to the three-parameter form of the isothermal Parsafar and Mason equation of state (EoS) with an accuracy better than 0.07%. Taking the temperature dependence of the coefficients into account, it was found that the MD data are satisfactorily reproduced by the universal EoS. The isothermal compressibility coefficient dependence with pressure can be described by a linear relation. 相似文献