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91.
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93.
The palladium-catalyzed hydrostannolysis of α-disubstituted allyl β-keto esters yields the corresponding tributyltin β-keto carboxylates which loose carbon dioxide at very moderate temperature, thus leading to the regiospecific formation of tributyltin tetrasubstituted enolates. 相似文献
94.
Zhen‐Ting Du Guo‐Ren Yue An‐Pai Li Jun‐Ying Ma Tong‐Xing Wu Xue‐Gong She Xin‐Fu Pan 《中国化学会会志》2004,51(3):505-508
A facile total synthesis of (±)‐nimbiol 1 has been achieved. In order to decrease the dioxo byproduct 2a , an improved oxidation system of CrO3/H2O/HOAc/NaOAc was used. 相似文献
95.
Three novel supramolecular arrays of zigzag polyaromatic salts are reported. Both the conformation and disposition of the dications are subjected to various noncovalent interactions. Thus, the presence or absence of the π‐π interacting enclathrated molecules, the efficient packing and the involved hydrogen bonding interactions of anions, as well as the increased hydrophobic property of the dications themselves exert influence. 相似文献
96.
手性毛细管色谱法测定人尿中美芬妥英对映体的含量及其在代谢分型中的应用 总被引:2,自引:0,他引:2
采用手性毛细管色谱柱和FID检测器建立了人尿中美芬妥英(MP)对映体的定量分析方法。尿样用二氯乙烷提取,用酸、碱洗涤得以纯化,测得各对映体的最低检测限为60μg/L。在115~690μg/L浓度范围内,标准曲线呈良好的线性关系,r>0.99,日内、日间精密度RSD<6.5%,S-MP的平均回收率为74.41%,R-MP的平均回收率为73.78%。并以MP为探针药物,对32名志愿者的尿样进行了MP氧化代谢分型研究。 相似文献
97.
Reciprocal derivative constant-current stripping analysis (RD-CCSA) is based on the measurement of dt/dE converted from a derivative signal, dE/dt, vs. electrode potential (E) during the stripping of analyte under galvanostatic conditions from a mercury-film electrode after preconcentration. The potential transient signal (E-t) in normal chronopotentiometric stripping analysis (CPSA) is converted in RD-CCSA into a stripping peak (dT/dE)(p) the height of which is proportional to the bulk concentration of analyte in solution. The theory of RD-CCSA has been derived, and validated by the good correlation obtained between the theory and experimental data. Compared with normal CPSA, RD-CCSA is more sensitive and has higher resolution. The detection limit for cadmium is 6 x 10(-10)M. Simultaneous determination of Cd(2+), In(3+), and Tl(+) (for which the differences between the stripping peak potentials are 58 and 50 mV, respectively) which is impossible for normal CPSA, voltammetry or differential pulse polarography, has become possible with RD-CCSA. 相似文献
98.
Shen R Lin CT Bowman EJ Bowman BJ Porco JA 《Journal of the American Chemical Society》2003,125(26):7889-7901
The total synthesis and stereochemical assignment of the potent antitumor macrolide lobatamide C, as well as synthesis of simplified lobatamide analogues, is reported. Cu(I)-mediated enamide formation methodology has been developed to prepare the highly unsaturated enamide side chain of the natural product and analogues. A key fragment coupling employs base-mediated esterification of a beta-hydroxy acid and a salicylate cyanomethyl ester. Three additional stereoisomers of lobatamide C have been prepared using related synthetic routes. The stereochemistry at C8, C11, and C15 of lobatamide C was assigned by comparison of stereoisomers and X-ray analysis of a crystalline derivative. Synthetic lobatamide C, stereoisomers, and simplified analogues have been evaluated for inhibition of bovine chromaffin granule membrane V-ATPase. The salicylate phenol, enamide NH, and ortho-substitution of the salicylate ester have been shown to be important for V-ATPase inhibitory activity. 相似文献
99.
The kinetics of dehydroxylation of synthetic aluminous goethite was studied using isothermal and non-isothermal thermogravimetry. The complete isothermal dehydroxylation can be described by the Johnson-Mehl equation with up to three linear regions in plots of lnln [1/(1–y)]vs. Int Kinetics for the initial stage of dehydroxylation changed from diffusion to first-order through the temperature range 190 to 260°C. The rate of dehydroxylation was reduced by Al-substitution and increased with temperature. Activation energy for dehydroxylation, calculated from the time to achieve a given dehydroxylation extent, varied depending on the extent of dehydroxylation and Al-substitution. Non-stoichiometric OH existed in goethite and some remained in hematite after the complete crystallographic transition. 相似文献
100.
用停流FIA-分光光度法研究了铬(Ⅵ)-碘化钾动力学反应体系中铁(Ⅱ)和钒(Ⅳ)的协同诱导效应,以协同系数(D)表示二者相互作用程度的大小,在此基础上提出了一种新的动力学双组份同时测定的方法,本法可扩大前述方法的线性范围,并降低检测限,测定了模拟水样品中铁和钒的含量,结果满意。 相似文献