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941.
942.
The cyclocondensation of 3-amino-2-iminonaphtho[1,2-d]thiazole ( 1 ) with a series of α-keto mono- and dicarboxylic acid derivatives 5a-i under different conditions was investigated. When the experiments were performed by refluxing in glacial acetic acid, the corresponding cyclized products, 2-substituted 3-oxo-3H-naphtho[1′,2′:4,5]thiazolo[3,2-b][1,2,4]triazines 4 were obtained in fair to good yields. On the other hand, when the reaction was conducted in boiling ethanol, it gave only the open chain condensates 6 , or in rare cases, together with minor amount of 4 . Since the intermediates 6 exist as mixture of both E- and Z-isomers, cyclization through heating was found insufficient. In any event representative compounds 4b,g,i have been evaluated for anti-HIV activity, but none of them were active. 相似文献
943.
Two natural products databases, the marine natural products database (MNPD) and the traditional Chinese medicines database (TCMD), were used to find novel structures of potent SARS-CoV protease inhibitors through virtual screening. Before the procedure, the databases were filtered by Lipinski's ROF and Xu's extension rules. The results were analyzed by statistic methods to eliminate the bias in target-based database screening toward higher molecular weight compounds for enhancing the hit rate. Eighteen lead compounds were recommended by the screening procedure. They were useful for experimental scientists in prioritizing drug candidates and studying the interaction mechanism. The binding mechanism was also analyzed between the best screening compound and the SARS protein. 相似文献
944.
Chen CH Liu KY Sudhakar S Lim TS Fann W Hsu CP Luh TY 《The journal of physical chemistry. B》2005,109(38):17887-17891
Thin films of silica hybrid materials consisting of two to three covalently bound organic chromophores at different ratios were conveniently synthesized and fabricated. The photophysical properties of these materials have been studied. The fluorescence spectra reveal complete fluorescence resonance energy transfer (FRET) from donor to acceptor, and the light-harvesting ability of these hybrid materials increases with increasing the molar fraction of donor chromophore. In a three-chromophore system, the energy is transferred from 300 to 530 nm successfully. Time-resolved fluorescence experiments are employed to elucidate the average rates and efficiencies (84-97%) of energy transfer in these organic/inorganic hybrid systems. The hybrid materials have been shown to provide antenna effect to facilitate energy transfer and light harvesting. 相似文献
945.
Aza-Morita-Baylis-Hillman reactions of N-(benzylidene)polyfluoroanilines 1 with methyl acrylate or acrylonitrile were studied. It was found that Lewis base, solvent and reaction temperature can significantly affect the reaction. Using 3-hydroxyquinuclidine (3-HQD) as a Lewis base in the reactions of 1 with methyl acrylate in DMF, the normal aza-Morita-Baylis-Hillman adducts 3 were formed in moderate to excellent yields. For the reactions of 1 with acrylonitrile, 1,4-diazabicyclo[2.2.2]octane (DABCO) is the best Lewis base giving the corresponding aza-Morita-Baylis-Hillman adducts 4 as the sole product in good to moderate yield. However, upon treatment of 1 with acrolein 2c, the corresponding reaction did not occur even in the presence of a variety of catalysts. 相似文献
946.
James V. Beitz C.W. Williams K.-S. Hong G.K. Liu 《Journal of solid state chemistry》2005,178(2):511-520
We have assessed the feasibility of carrying out time- and wavelength-resolved laser-induced fluorescence measurements of radiation damage in glassy silica. The consequences of alpha decay of Es-253 in LaPO4 nanophases embedded in silica were probed based on excitation of 5f states of Cm3+, Bk3+, and Es3+ ions. The recorded emission spectra and luminescence decays showed that alpha decay of Es-253 ejected Bk-249 decay daughter ions into the surrounding silica and created radiation damage within the LaPO4 nanophases. This conclusion is consistent with predictions of an ion transport code commonly used to model ion implantation. Luminescence from the 6D7/2 state of Cm3+was used as an internal standard. Ion-ion energy transfer dominated the dynamics of the observed emitting 5f states and strongly influenced the intensity of observed spectra. In appropriate sample materials, laser-induced fluorescence provides a powerful method for fundamental investigation of alpha-induced radiation damage in silica. 相似文献
947.
Liu Q Fang D Zheng J 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(7):1453-1457
Infrared spectroscopy studies of methyl 4-hydroxybenzoate (MHB) in 17 different organic solvents and in ethanol/CCl4 binary solvent were undertaken to investigate the solvent-solute interactions. The frequencies of carbonyl stretching vibration nu(C=O) of MHB in single solvents were correlated with the solvent acceptor number (AN) and the linear solvation energy relationships (LSER). The assignments of the two bands of nu(C=O) of MHB in alcohols and the single one of that in non-alcoholic solvents were discussed. The shifts of nu(C=O) of MHB in ethanol/CCl4 binary solvents showed that several kinds of solute-solvent hydrogen bonding interactions coexisted in the mixture solvents, with a change in the mole fraction of ethanol in the binary solvents. 相似文献
948.
To increase the solubility and film forming ability of polybenzimidazole (PBI), poly(N‐methylbenzimidazole) (PNMBI) with different degrees of methylation was synthesized. Chemical structure, degree of substitution, and solubility of PNMBI was studied. PNMBI is easier to be doped with acid than PBI. The basicity of PNMBI was improved with the introduction of methyl groups on the imidazole moiety. Effects of methylation degree, H3PO4 content and temperature on proton conductivity of PNMBI doped H3PO4 was studied. Proton conductivity of H3PO4 doped PNMBI‐1.2 membranes increases with increasing doping level. Temperature dependence of proton conductivity of H3PO4 doped PNMBI‐1.2 membranes follows the Arrhenius law. With an increase in the degree of substitution, proton conductivity of H3PO4 doped PNMBI decreases dramatically. The proton transport mechanism was also discussed. The proton conductivity of PNMBI/H3PO4 is mainly contributed by proton hopping or Grotthuss mechanism. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
949.
William H. Watson Satish G. Bodige Jie Liu Michael G. Richmond 《Structural chemistry》2003,14(4):369-375
The reactivity of the bidentate ligand 2,3-bis(diphenylphosphino)-N-phenylmaleimide (bppm) with the tetrahedrane cluster PhCCo3(CO)9 under thermolysis and ETC conditions has been studied and found to ultimately give Co3(CO)6[μ2,η2,η1-C(Ph) ${\text{C}}{\text{ = }}{\text{ = }}{\text{C(PPh}}_{\text{2}} {\text{)C(O)NPhC}}$ (O)](μ2-PPh2) as the final product. The intermediate cluster compound PhCCo3(CO)7(bppm), which was observed by IR and 31P NMR spectroscopies, readily and rapidly transforms into the product cluster under the reactions conditions. The solid-state structure of Co3(CO)6[μ2,η2,η1-C(Ph)fptt(O)](μ2-PPh$_{2})$ was unequivocally determined by X-ray crystallography. Co3(CO)6[μ2, η2, η1-C(Ph)Õ(O)](μ2-PPh2) crystallizes in the monoclinic space group P2(1)/n, a = 11.825(5) Å, b = 31.20(1) Å, c = 11.831(5) Å, β = 108.720(7)°, V = 4134(7) Å3, Z = 4, d calc = 1.567 Mg/m3; R = 0.0350, R w = 0.0817 for 4747 observed reflections with I > 2σ(I). The X-ray structure confirms the coupling of the benzylidyne ligand with the bppm ligand in Co3(CO)6[μ2,η2,η1-C(Ph)Õ(O)](μ2-PPh2). The course of the thermolysis reaction is identical to those reactions carried out with the related diphosphine ligands bma and bpcd. The utility of electron-transfer catalysis (ETC) in the preparation of PhCCo3(CO)7(bppm) is discussed relative to the reduction potential of the bppm ligand and the tricobalt cluster PhCCo3(CO)9. 相似文献
950.
共合成了13个未见文献报道的三烃基锡肟衍生物,测定了它们的^1h,(^13C,^119Sn)NMR,IR和MS。结果表明此类化合物为四配位锡单体结构,生物活性测定结果表明部分化合物同时兼有杀菌、杀螨、除草多种活性。 相似文献