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221.
A highly useful method for the synthesis of optically active alpha,gamma-substituted gamma-butyrolactones has been developed. The SmI(2)-induced reductive coupling of chiral 2-alkyl acrylates derived from isosorbide with ketones in the presence of (1S)-(-)-2,10-camphorsultam as a proton source give the chiral alpha,gamma-substituted gamma-butyrolactones in good yields and high enantiomeric purities (up to >99% ee for trans and 75% ee for cis). The reaction system has been investigated with various ketones, and it is demonstrated that this system is very effective for trans-alpha,gamma-substituted gamma-butyrolactones. Both the chiral auxiliary and the hindered proton source in this system are necessary for the observed excellent ee values of the products. The absolute configuration of the trans products is assigned on the basis of the X-ray crystal structure. 相似文献
222.
在甲烷氧化偶联制C2烃的研究中,人们发现碱土金属与稀土金属组成的复合氧化物催化剂具有高的催化活性[1,2].稀土化合物作为有希望的工业催化剂之一,已受到广泛的关注.一般认为,它们含有的氧空位对活化甲烷的有效氧物种有利.Debey等在1%Sr/La2O... 相似文献
223.
Facile fabrication of AgCl@polypyrrole-chitosan core-shell nanoparticles and polymeric hollow nanospheres 总被引:1,自引:0,他引:1
A one-step sequential method for preparing AgCl@polypyrrole-chitosan core-shell nanoparticles and subsequently the formation of polypyrrole-chitosan hollow nanospheres is reported. The formation of the core and the shell is performed in one reaction medium almost simultaneously. Transmission electron microscopy (TEM) images show the presence of core-shell nanoparticles and hollow nanospheres. Ultraviolet-visible (UV-vis) studies reveal that AgCl was formed first followed by polypyrrole. X-ray diffration (XRD) and UV-vis studies show that AgCl was present in the core-shell nanoparticles and could be removed completely from the core. 相似文献
224.
Amperometric glucose biosensor based on electrodeposition of platinum nanoparticles onto covalently immobilized carbon nanotube electrode 总被引:6,自引:0,他引:6
A new amperometric biosensor for glucose was developed based on adsorption of glucose oxidase (GOx) at the gold and platinum nanoparticles-modified carbon nanotube (CNT) electrode. CNTs were covalently immobilized on gold electrode via carbodiimide chemistry by forming amide linkages between carboxylic acid groups on the CNTs and amine residues of cysteamine self-assembled monolayer (SAM). The fabricated GOx/Aunano/Ptnano/CNT electrode was covered with a thin layer of Nafion to avoid the loss of GOx in determination and to improve the anti-interferent ability. The immobilization of CNTs on the gold electrode was characterized by quartz crystal microbalance technique. The morphologies of the CNT/gold and Ptnano/CNT/gold electrodes have been investigated by scanning electron microscopy (SEM), and the electrochemical performance of the gold, CNT/gold, Ptnano/gold and Ptnano/CNT/gold electrodes has also been studied by amperometric method. In addition, effects of electrodeposition time of Pt nanoparticles, pH value, applied potential and electroactive interferents on the amperometric response of the sensor were discussed.
The enzyme electrode exhibited excellent electrocatalytic activity and rapid response for glucose in the absence of a mediator. The linear range was from 0.5 to 17.5 mM with correction coefficient of 0.996. The biosensor had good reproducibility and stability for the determination of glucose. 相似文献
225.
A new compound (5R, 10R)-3,8-dihydroxy-5,10-diethoxy-5,10-dihydrochromeno[5,4,3-cde]chromene monohydrate was obtained from 3,4-dihydroxybenzaldehyde in aerobic basic aqueous ethanol solution in the presence
of manganese chloride and triethylamine and crystallized in orthorhombic P212121 space group (denoted as 1). When 1 was recrystallized from aqueous methanol, it was transformed to another crystal (2) with the same composition but in P21/n space group. The drastic difference in the extensive hydrogen bond network makes 1 a 3D and 2 a 2D infinite supramolecular structure, respectively. 相似文献
226.
Geney R Sun L Pera P Bernacki RJ Xia S Horwitz SB Simmerling CL Ojima I 《Chemistry & biology》2005,12(3):339-348
A new computational docking protocol has been developed and used in combination with conformational information inferred from REDOR-NMR experiments on microtubule bound 2-(p-fluorobenzoyl)paclitaxel to delineate a unique tubulin binding structure of paclitaxel. A conformationally constrained macrocyclic taxoid bearing a linker between the C-14 and C-3'N positions has been designed and synthesized to enforce this "REDOR-taxol" conformation. The novel taxoid SB-T-2053 inhibits the growth of MCF-7 and LCC-6 human breast cancer cells (wild-type and drug resistant) on the same order of magnitude as paclitaxel. Moreover, SB-T-2053 induces in vitro tubulin polymerization at least as well as paclitaxel, which directly validates our drug design process. These results open a new avenue for drug design of next generation taxoids and other microtubule-stabilizing agents based on the refined structural information of drug-tubulin complexes, in accordance with typical enzyme-inhibitor medicinal chemistry precepts. 相似文献
227.
亮菌甲素的荧光光度法测定 总被引:1,自引:0,他引:1
对亮菌甲素的荧光特性进行了研究 ,发现该物质在四硼酸钠缓冲溶液 (pH 8.8± 0 .0 2 )介质中有很强的荧光性质 ,其激发波长为 2 81nm ,发射波长为 4 62nm ,亮菌甲素浓度在 0 .1~ 4 .5 μg·ml- 1范围内与荧光强度呈线性关系 (F =79.4C +3.4 6,r =0 .9994 )。用荧光法测定片剂中亮菌甲素的含量 ,方法简单、快捷、灵敏度高。 相似文献
228.
钴(II)-联吡啶-α-氨基酸的热力学和动力学研究 总被引:3,自引:0,他引:3
关于联吡啶为第一配体的二元、三元配合物的热力学和动力学性质的研究,以铜(Ⅱ)作为中心离子最为多见,而以钴(Ⅱ)作为中心离子的报导较少.实验表明,过渡金属钻(Ⅱ)能与大多数的生物配体、大π共轭体系形成相当稳定的二元、三元配合物,是生物功能模拟的一个具有应用价值的中心离子·钴(Ⅱ)卟啉可以代替铁(Ⅱ)卟啉,模拟血红蛋白、肌红蛋白[1],在生物体内起到输送氧的作用.为了充分了解钴(Ⅱ)与生物配体的配伍能力、配位方式以及其配位过程的动态行为,为推动钴(Ⅱ)配合物及其生物功能的模拟研究,本文分别采用PH电位法… 相似文献
229.
230.
Two cobalt(II) coordination polymers formed from bte (bte = 1,2-bis(1,2,4-triazol-1-yl)ethane), namely [Co(bte)2(dca)2]n (1) and {[Co(bte)(dca)2] · H2O}n (2), have been synthesized and characterized by elementary analyses, IR, thermogravimetric analyses, X-ray diffraction analyses and magnetic measurements. Compound 1 is a double-chain with Co(II) centers bridged by bte, containing metallocycles of [Co2(bte)2] and trans dca as termination ligands. In 2, each Co(II) center is bonded by two bridging bte ligands and four dca as μ-1,5-dca in different orientations in the 3D network. 相似文献