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91.
Four new aromatic compounds have been isolated from the fruits of Cordia latifolia (Boreginaceae) bearing a common basic skeleton but differing in the side chain. Their structures were elucidated using spectrometric methods including 1D- (1H and 13C) and 2D-NMR experiments, (1H, 1H-COSY, NOESY, HMQC and HMBC) and chemical transformations. 相似文献
92.
The extraction of In(III) from HCl, H2SO4, and HNO3 media using a 0.20 mol l−1 Cyanex 923 solution in toluene is investigated. In(III) is quantitatively extracted over a fairly wide range of HCl molarity while from H2SO4 and HNO3 media the extraction is quantitative at low acid concentration. The extracted metal ion has been recovered by stripping with 1.0 mol l−1 H2SO4. The stoichiometry of the In(III): Cyanex 923 complex is observed to be 1:2. The extraction of In(III) is insignificantly changed in diluents namely toluene, n-hexane, kerosene (160-200 °C), cyclohexane, and xylene having more or less the same dielectric constants, whereas, it decreases with increasing polarity of diluents such as cyclohexanone and chloroform. The extractant is stable towards prolonged acid contact and there is a negligible loss in its extraction efficiency even after recycling for 20 times. The extraction behavior of some commonly associated metal ions namely V(IV), Ti(IV), Al(III), Cr(III), Fe(III), Ga(III), Sb(III), Tl(III), Mn(II), Fe(II), Cu(II), Zn(II), Cd(II), Pb(II), and Tl(I) has also been investigated. Based on the partition data the conditions have been identified for attaining some binary separations of In(III). These conditions are extended for the recovery of pure indium from zinc blend, zinc plating mud, and galena. The recovery of the metal ions is around 95% with purity approximately 99%. 相似文献
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Tetracyclic triterpenoids from the leaves of Azadirachta indica and their insecticidal activities 总被引:1,自引:0,他引:1
Siddiqui BS Afshan F Gulzar T Sultana R Naqvi SN Tariq RM 《Chemical & pharmaceutical bulletin》2003,51(4):415-417
A new tetranortriterpenoid, meliatetraolenone [24,25,26,27-tetranor-apotirucalla-(apoeupha)-6alpha-O-methyl, 7alpha-senecioyl(7-deacetyl)-11alpha,12alpha,21,23-tetrahydroxy-21,23-epoxy-2,14,20(22)-trien-1,16-dione] (1) was isolated from the methanolic extract of fresh leaves of Azadirachta indica along with the known compound odoratone (3) which was hitherto unreported from this source. Their structures have been elucidated by spectral studies including 2D NMR. The insecticidal activities of 1 as well as those of odoratone (3) are reported. 1 and odoratone both showed mortality on fourth instar larvae of mosquitoes (Anopheles stephensi) with LC(50) values of 16 and 154 ppm, respectively. 相似文献
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Studies undertaken on the fresh leaves of Carissa carandas have led to the isolation of four pentacyclic triterpenoids (1-4) including one new constituent carissin (1) and two hitherto unreported compounds 2 and 3. The structure of the new triterpenoid has been elucidated as 3beta-hydroxy-27-E-feruloyloxyurs-12-en-28-oic acid. Compelete assignment of the protons of 2 has also been made based on 2D NMR studies. 相似文献
96.
Studies on the chemical constituents of the aerial parts of Ocimum basilicum have led to the isolation of three new compounds, basilol (1), ocimol (2), and basilimoside (3), along with two known constituents betulinic acid and oleanolic acid. The structures of the new constituents have been elucidated through spectral studies including 2D-NMR experiments (HMQC, HMBC, COSY, NOESY, and J-resolved) and chemical transformation, as p-formylphenyl 3beta-hydroxyolean-12-en-28-oate (1), 2-methoxy-4-carbomethoxyphenyl 3beta-hydroxy-lup-20(29)-en-28-oate (2), and (22E)-24xi-ethyl-25-methylcholesta-5,22-diene-3beta-ol-3-O-D-glucopyranoside (3). 相似文献
97.
There has been great progress in the development of potential energy surfaces (PESs) for reaction dynamics that are fits to ab initio energies. The fitting techniques described here explicitly represent the invariance of the PES with respect to all permutations of like atoms. A review of a subset of dynamics calculations using such PESs (currently 16 such PESs exist) is then given. Bimolecular reactions of current interest to the community, namely, H + CH(4) and F + CH(4), are focused on. Unimolecular reactions are then reviewed, with a focus on the photodissociation dynamics of H(2)CO and CH(3)CHO, where so-called "roaming" pathways have been discovered. The challenges for electronically non-adiabatic reactions, and associated PESs, are presented with a focus on the OH* + H(2) reaction. Finally, some thoughts on future directions and challenges are given. 相似文献
98.
Xiao Xie Bina Choi Dr. Eric Largy Dr. Régis Guillot Dr. Anton Granzhan Dr. Marie‐Paule Teulade‐Fichou 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(4):1214-1226
The interactions of three cationic distyryl dyes, namely 2,4‐bis(4‐dimethylaminostyryl)‐1‐methylpyridinium ( 1 a ), its derivative with a quaternary aminoalkyl chain ( 1 b ), and the symmetric 2,6‐bis(4‐dimethylaminostyryl)‐1‐methylpyridinium ( 2 a ), with several quadruplex and duplex nucleic acids were studied with the aim to establish the influence of the geometry of the dyes on their DNA‐binding and DNA‐probing properties. The results from spectrofluorimetric titrations and thermal denaturation experiments provide evidence that asymmetric (2,4‐disubstituted) dyes 1 a and 1 b bind to quadruplex DNA structures with a near‐micromolar affinity and a fair selectivity with respect to double‐stranded (ds) DNA [Ka(G4)/Ka(ds)=2.5–8.4]. At the same time, the fluorescence of both dyes is selectively increased in the presence of quadruplex DNAs (more than 80–100‐fold in the case of human telomeric quadruplex), even in the presence of an excess of competing double‐stranded DNA. This optical selectivity allows these dyes to be used as quadruplex‐DNA‐selective probes in solution and stains in polyacrylamide gels. In contrast, the symmetric analogue 2 a displays a strong binding preference for double‐stranded DNA [Ka(ds)/Ka(G4)=40–100), presumably due to binding in the minor groove. In addition, 2 a is not able to discriminate between quadruplex and duplex DNA, as its fluorescence is increased equally well (20–50‐fold) in the presence of both structures. This study emphasizes and rationalizes the strong impact of subtle structural variations on both DNA‐recognition properties and fluorimetric response of organic dyes. 相似文献
99.
The first mild, efficient, solvent‐free Friedel–Crafts acylation of reserpine has been developed, which resulted in the synthesis of 10‐ and 12‐acylated homologues in high overall yields. 相似文献
100.