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61.
Ella Zafrir-Ilan 《Tetrahedron letters》2010,51(50):6602-6604
Two new thiazole-containing cyclic hexapeptides, microcyclamides MZ602 and MZ568, were isolated from the hydrophilic extract of the cyanobacterium Microcystis sp. The structures of the pure natural products were elucidated using spectroscopic methods including UV, 1D and 2D NMR, and MS techniques. The absolute configuration of the chiral centres of the modified cyclic peptides was determined using Marfey’s method for HPLC. The microcyclamides have been evaluated for their cytotoxicity against leukemia cell lines and inhibition of serine proteases. 相似文献
62.
Conductivity detection, which is universal in capillary electrophoresis (CE), has received considerable attention, since the introduction of the axial capacitively coupled contactless detector C4D in 1998. This detector is made of two electrodes which are placed cylindrically around the CE capillary and connected to the AC oscillator. The distance between the electrodes is the detection gap. In this review, applications of CE and MCE with C4D in pharmaceutical and biological analysis are presented. 相似文献
63.
A spectrodensitometric method is described for the determination of the components of two analgesic mixtures. For the first mixture (paracetamol-ascorbic acid-caffeine-phenylephrine), the pharmaceutically active components were separated from each other and closely related degradation products and impurities on high-performance thin-layer chromatography (F254) plates using methylene chloride-ethyl acetate-ethanol-formic acid (3.5 + 2 + 4 + 0.5) and methylene chloride-ethyl acetate-ethanol (5 + 5 + 1) as the developing systems. The other mixture (phenazone-phenacetin-caffeine) was separated efficiently from the degradation products using the same plates and acetonitrile-chloroform (1 + 1) as the mobile phase. The proposed method was used to determine these mixtures in commercial tablets. 相似文献
64.
The IR- and RAMAN spectra are reported for the above mentionned compounds. All valence force-constants are calculated. The substitution of oxygen by sulfur causes a decrease of all force-constants. 18% for f P? OCH3 and f P? SCH3, 10% for f O?P and f S?P and 2% for f O? CH3 and f S? CH3. 相似文献
65.
Sameh M. Aboul‐Fotouh 《中国化学会会志》2003,50(6):1151-1158
The reactivity of cyclohexene (CHE) over catalysts containing 0.3 wt% Pt, 0.3 wt% Re or 0.3 wt% Pt + 0.3 wt% Re supported on Na‐ and H‐mordenite has been studied in an atmospheric flow‐type reactor at a temperature range of 100–400 °C, using a flow of hydrogen (20 cm3/min). The catalysts were characterized for acid sites strength‐distribution, using desorption of ammonia in DSC. The acidity of H‐mordenite (HM) is attributed to strong acid sites, whereas the acidity of Na‐mordenite (NaM) is due to weak acid sites which are not involved in the catalytic reaction under study. The catalysts containing HM enhance the reactivity of CHE for isomorization reactions. However, the reactivity of CHE on NaM catalysts enhances only the hydrogenation and dehydrogenation reactions. Pt/HM is the most selective catalyst for isomerization of CHE, whereas Pt/NaM and PtRe/NaM catalysts are the most selective for hydrogenation and dehydrogenation reactions, respectively. The hydroisomorization of CHE seems to depend only on the acidity of the catalysts, whereas both hydrogenation and dehydrogenation reactions were controlled by metallic function of the catalysts. 相似文献
66.
Winfried Wendelin Edith Gößnitzer Dalal Abou El Ella 《Monatshefte für Chemie / Chemical Monthly》2000,131(4):353-374
Summary. The cyclization reactions of trans-3a-hexahydro-2-benzimidazolamine with 2-alkylidene- and 2-benzylidenecyclohexanones and α-tetralones, respectively, yield
mixtures of two isomeric condensates each. Thorough high resolution NMR analyses (1H and 13C NMR, HH-COSY, gs-HSQC, gs-HMBC, 1D TOCSY, and 1D NOE difference spectra) revealed that the corresponding isomers are in all cases linearly fused diastereomeric
12α- and 12β-substituted trans-6aα-dodecahydrobenzimidazo[2,1-b]quinazolines and 7α-substituted trans-8aβ- and trans-8aα-decahydrobenzimidazo[2,1-b]benzo[h]quinazolines, respectively. The formation of corresponding angularly fused regioisomers was not observed so far. The stereochemistry
and the tautomerism of some bases and their hydrochlorides as well as the regiospecific course of the cyclization reactions
are discussed. Biological tests showed that the novel compounds don’t exert remarkable antibacterial and antimycotic effects.
Received November 3, 1999. Accepted November 30, 1999 相似文献
67.
Gorla Rama Subba Reddy Mansour M. A. Hassanien I. A. Bakier A. Y. 《Transport in Porous Media》1999,36(2):245-254
In the present work, the effect of mixed convection about vertical surfaces on the phenomenon of melting process in a fluid-saturated porous medium is analyzed on the basis of boundary layer approximations. Similarity solutions are obtained for aiding external flow. The final similarity equations are integrated numerically by use of the fourth-order Runge–Kutta method. Results are reported for the flow and thermal fields in the melt region. The melting phenomenon decreases the local Nusselt number at the solid–liquid interface. 相似文献
68.
Arwa Alrooqi Zahra M. Al-Amshany Laila M. Al-Harbi Tariq A. Altalhi Moamen S. Refat A. M. Hassanien A. A. Atta 《Molecules (Basel, Switzerland)》2022,27(6)
The impact of the charge transfer complex on the dielectric relaxation processes in free poly(methyl methacrylate) (PMMA) polymer sheets was investigated. The frequency dependence of dielectric properties was obtained over the frequency range 0.1 Hz–1 MHz at temperatures ranging between 303 K and 373 K for perylene dye and acceptors (picric acid (PA) and chloranilic acid (CLA)) in an in situ PMMA polymer. The TG/dTG technique was used to investigate the thermal degradation of the synthesized polymeric sheets. Additionally, the kinetic parameters have been assessed using the Coats–Redfern relation. The dielectric relaxation spectroscopy of the synthesized polymeric sheets was analyzed in terms of complex dielectric constant, dielectric loss, electrical modulus, electrical conductivity, and Cole–Cole impedance spectroscopy. α- and β-relaxation processes were detected and discussed. The σ(ω) dispersion curves of the synthesized polymeric sheets show two distinct regions with increasing frequency. The impedance data of the synthesized polymeric sheets can be represented by the equivalent circuit (parallel RC). 相似文献
69.
Ella M. Moroz Ella M. Moroz Kristina I. Shefer Kristina I. Shefer Dmitry A. Zyuzin Dmitry A. Zyuzin Aleksandra S. Ivanova Aleksandra S. Ivanova Eugenia V. Kulko Eugenia V. Kulko Vasily V. Goidin Vasily V. Goidin Viktor V. Molchanov Viktor V. Molchanov 《Reaction Kinetics and Catalysis Letters》2006,87(2):367-375
Summary The structure of pseudoboehmite was studied by the method of wide-angle X-ray scattering (WAXS). The samples of pseudoboehmite
with various characteristics produced by different methods were examined in order to obtain the most complete information
about their structure. In contrast to reference data, it was found that modifications in the structure of pseudoboehmite layers
occur viathe insertion of additional water molecules. 相似文献
70.
The synthesis of three fluorophore-appended derivatives of dioscin and polyphyllin D is reported herein. Starting from trillin, dansyl derivatives A-C were prepared in overall yields of 7-12% over 7-10 steps. A study of their behavior in a variety of polar solvents suggests that dansyl derivatives A-C are capable of micellar self-assembly and can maintain cytotoxicities (IC50 = 15-18 muM) against the HeLa carcinoma cell line evaluated by standard MTT assay. [structure: see text] 相似文献