摘要:

AbstractA potent thromboxane antagonist, 1‐[2‐(2‐carboxyethyl)benzyl)]‐2‐benzenesulfonamidobicyclo‐[2.2.1]heptane was synthesized from norcamphor in 8 steps. It was shown to be a very potent thromboxane antagonist by inhibition of platelet aggregation induced by U46,619 at nanomolar concentration. The key intermediate 3‐[2‐bromomethylphenyl]propyl tetrahydropyran ether may be useful for the synthesis of other interphenylene containing prosta

ISSN:0009-4536    

DOI:10.1002/jccs.199800107

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractAffinity capillary electrophoresis is a new procedure for receptor‐ligand binding studies. Since its introduction in the early 1990s, this method has proved valuable in chiral separation of racemates, the measurement of binding constants, the estimation of kinetic rate constants, the determination of stoichiometries, the investigation of electrostatic interactions, the estimation of effective charges and molecular weights of biomolecules, the characterization of enzymatic catalysis, and, most recently, combinatorial library screening in solutions. This technique demands small amounts of samples, involves no radiolabeled materials or chemically immobilized ligands, and does not require changes in spectroscopic characteristics upon binding. This paper reviews the most recent applications of affinity capillary electrophoresis in binding measurement and combinatorial library screenin

ISSN:0009-4536    

DOI:10.1002/jccs.199800108

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe laser ablation technique has been employed to study silver colloidal formation. Laser intensities, irradiation wavelengths (1064 nm and 532 nm), and solvents (water, methanol, and isopropanol) were all considered. Changes of the maximum UV‐Visible absorbance of the solutions with laser intensities exhibited nonlinear behavior for 1064 nm and 532 nm and displayed better ablation efficiency at 532 nm. Larger mean sizes were observed at 532 nm or at higher pulse energy. For solvent effect, the bigger particle sizes were generated in H2O. As to colloidal stability, isopropanol, which has a lower dielectric constant than water, was found to stabilize Ag nanoparticles without protecting reagents over six months. Preliminary results in 2‐butanol suggested that the viscosity of solvent may need to be considered in addition to the dielectric const

ISSN:0009-4536    

DOI:10.1002/jccs.199800109

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractA series of Ti‐promoted (6 wt%) Co/SiO2catalysts with titania content of 0 to 10 wt% were sequentially prepared by incipient wetness impregnation, and characterized with X‐ray diffraction, thermogravimetric analysis, chemisorption, temperature‐programmed desorption and infrared spectroscopy. The influences of Ti addition and reduction temperature (400–700 °C) on the adsorptive behavior and the catalytic properties for CO hydrogenation were investigated. The presence of Ti decreases the adsorption capacity of the cobalt surface for H2, but enhances activity per gram cobalt. In addition, the turnover frequency increases 2–4 times upon Ti addition at reduction temperatures of 400–700 °C. The promotion in activity is accompanied by an enhanced selectivity for higher hydrocarbons and olefins. These modifications can be rationalized by the creation of active sites for CO dissociation. The desorption of CO2at 100 °C during temperature‐programmed desorption of CO indicates the formation of active sites for CO disproportionation. Infrared spectroscopy indicates an increase in the relative absorbance of 2060–2075 cm−1bands upon Ti addition, which are attributed to CO adsorbed on the defect sites of the cobalt surface. Therefore, the promotion effect of Ti may be directly related to the formation of defect sites on the cobalt surface induced by the decora

ISSN:0009-4536    

DOI:10.1002/jccs.199800110

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe syntheses and thermal stability properties of a series of amino and nitro substituted copperporphyrins are described. The thermal decomposition temperatures of the porphyrins were determined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). The on‐set thermal decomposition temperatures of the unsymmetrical porphyrins were found to be high in the range of 350 – 405 °C (DSC), 374 – 441 (TGA in air), 395 – 411 °C (TGA under nitrogen atmosphere), and 410 – 424 °C (DTA in air). Substituent dependent thermal stability trends were also studied. The trend is variable depending on the thermal analysis technique utilized. Possible reasons for such variation are discussed. These porphyrins are thermally robust even in the melamine‐based sol‐gel matrix. Containing 20% by weight of the substituted unsymmetrical copperporphyrin, melamine‐based sol‐gel showed no indication of decompo

ISSN:0009-4536    

DOI:10.1002/jccs.199800111

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe isomerization of the complex trans‐meso‐CH3Co(H2O)L2+(L = 5,7,7,12,14,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradeca‐4,11‐diene) to trans‐primary, rac‐CH3Co(H2O)L2+has been investigated from pH range 7.11 to 8.09 in aqueous solution. The reaction rate law has been determined as: ‐d[meso‐CH3Co(H2O)L2+]/dt = kOH[OH−][meso‐CH3Co(H2O)L2+], where kOH= 600 ± 10 M−1s−1at 25 °C and μ = 0.5 M. The activation parameters of the reaction were also studied with ΔH±= 19.1 ± 0.9 Kcal mol−1and ΔS±= 18.0 ± 0.8 cal K−1mol−1. A mechanism that i

ISSN:0009-4536    

DOI:10.1002/jccs.199800112

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractA number of terminal N‐alkylated linear tetraaza and pentaaza ligands were prepared. Their ligand protonation constants and some transition and post‐transition metal (Ni2+, Cu2+, Zn2+, and Cd2+) complex stability constants were determined by potentiometric titration methods. In general, methylation and ethylation at the terminal nitrogen atoms caused the corresponding ligand nitrogen basicity to increase; however, the corresponding metal complex stabilities were decreased compared to the non‐alkylated structural analogs, presumably due to a steric e

ISSN:0009-4536    

DOI:10.1002/jccs.199800113

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe reaction of Mo2(O3CCF3)4with (CH3)3SiI and PPh3gave the title complex [Mo3(O2CCF3)2I4]‐(HPPh3)2which was characterized by X‐ray crystallography. Crystal data for [Mo2(O2CCF3)2I4](HPPh3)2: space group\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm P}\bar 1 $\end{document}, a = 10.953(4) Å, b = 12.784(3) Å, c = 19.829(4) Å, α = 100.68(2)°, β = 91.16(2)°, γ = 112.98(2)°, V = 2498.6(10) Å3, Z = 2, with final residuals R = 0.0887 and Rw = 0.0965. There are two independent molecules in each asymmetric unit. The molybdenum, oxygen, and fluoride atoms in one of the two independent molecules are disordered, such that the primary set is 53% occupied, and the seco

ISSN:0009-4536    

DOI:10.1002/jccs.199800114

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractTwo selected benzoylhydrazones I and II were subjected to thermolysis by reflux at 200 °C. Benzil, benzoic acid, biphenyl, benzanilide together with the corresponding ketones, nitriles and imines were isolated. Similar treatment of the third hydrazone III at 250 °C afforded, in addition to the previous products, bibenzyl, stilbene, and 2‐phenylindole. Photolysis of the same hydrazones I‐III in acetonitrile gave the previously reported products but in different ratios along with azine derivatives and substituted methanes. A free radical mechanism involving homolysis of the N‐N and C‐N bonds is suggested, substantiated by trapping of phenyl radical with isoquinoline, to account for the formation of the identified

ISSN:0009-4536    

DOI:10.1002/jccs.199800115

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractEighteen compounds including fourteen lignans, one coumarin, and three alkaloids were isolated from the leaves ofMagnolia coco.Their structures were established by comparison of spectral data with literature values. Among them,N‐acetylanolobine was elucidated as a new compoun

ISSN:0009-4536    

DOI:10.1002/jccs.199800116

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY