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751.
<正>Two new terpenes,wilfornine H(1) and triptobenzene Q(2) were isolated from Tripterygium wilfordii,as well as 11 terpenes. Their structures were elucidated by spectroscopic methods.Compounds 5,9-13 showed significant immunosuppressive activities. 相似文献
752.
753.
Tian Jin Lu Zhao Maolin Huang Yan Yue Zhe-Bin Zheng Won-Hun Ham 《Tetrahedron: Asymmetry》2017,28(5):725-729
Concise stereoselective syntheses of (?)-clavaminol A and deacetyl (+)-clavaminol H have been achieved from simple starting materials. Highlights of the synthesis for (?)-clavaminol A include a highly diastereoselective chelation-controlled hydride reduction of an amino ketone to give the anti amino alcohol directly, and NaBH4-mediated dehalogenation. The main synthetic approach for deacetyl (+)-clavaminol H features a highly diastereoselective chelation-controlled hydride reduction of the amino ketone to construct the anti amino alcohol and a palladium catalyzed hydrogenation reaction at the final step. 相似文献
754.
In this paper, plasma concentration, plasma protein binding rate, body distribution, and excretion of both oral and intravenous administration of rats were determined by high performance liquid chromatography (HPLC) combining with UV detector. The blood drug concentration of oral and intravenous administration was summarized. The bioavailability of T1/2 was approximately 0.75?hr. At the meanwhile, the bioavailability was about 18.84?±?2.21%. The plasma protein binding rate of 1-methyl hydantoin was about 24.36?±?0.93%, belonging to low protein binding drug. The result shows that 1-methyl hydantoin can be rapidly distributed in various organs and tissues and quickly eliminated within 6?hr without accumulation in the organs. Its discharge from the urine and feces was 16.58?±?4.48% and 3.37?±?0.71%, respectively. All of the results showed that the recovery rate, liner relationship, specificity, stability, and precision of the method were good. The study also proved that 1-methyl hydantoin has been eliminated quite faster in rats. 相似文献
755.
756.
对于单位球面中的扎维子流形,本文构造一类抽象的W_((n,F))-Willmore型泛函,此泛函推广经典的Willmore泛函到相当一般的情形,它的临界点称为W_((n,F))-Willmore型子流形,本文计算泛函的变分公式,推导泛函临界点的Simons型不等式,针对特殊的函数F,构造W_((n,F))-Willmore型子流形的例子,最后给出泛函临界点间隙现象的刻画. 相似文献
757.
Han Joong Koh Suk Jin Kang Dennis N. Kevill 《Phosphorus, sulfur, and silicon and the related elements》2013,188(7):1404-1415
Kinetic and product studies of the solvolyses of acyclic phosphorochloridates are extended to two cyclic diesters, 2-chloro-1,3,2-dioxaphospholane-2-oxide (1) and 2-chloro-5,5-dimethyl-1,3,2-dioxaphosphorinane-2-oxide (2). Slightly faster solvolyses are observed for 1 than for the acyclic dimethyl phosphorochloridate (3), and 2 solvolyzes somewhat slower than 3. An extended Grunwald–Winstein equation treatment shows similar sensitivities to changes in solvent nucleophilicity and solvent ionizing power for 1, 2, and 3, and a concerted SN2 attack is proposed in each case. Product studies for the solvolyses of 2 in aqueous alcohols are presented. 相似文献
758.
Clifford H. Champness Jin Pan 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):399-407
Abstract Evaporation of thallium on a crystallized layer of selenium results in an excellent Schottky diode, exhibiting a forward-to-reverse current ratio at 1 volt of some four to five orders of magnitude and a forward ideality factor close to unity. However, with the passage of time, there is a degradation in these electrical characteristics, if the thallium is exposed to the atmosphere, even at room temperature. The observed changes are a progressive increase in series resistance and a decrease in parallel capacitance. However, the changes with time can be greatly reduced if the thallium is covered with an evaporated film of Wood's metal. X-ray diffraction analysis of films of thallium deposited on glass substrates, shows that after prolonged exposure to air, the film is progressively transformed into Tl2CO3 . Oxide formation is only apparent after storage in oxygen, rather than air. The electrical degradation in the diodes is thus the result of atmospheric conversion of metallic thallium into the less conducting carbonate. 相似文献
759.
Huilu Wu Jin Kong Yanhui Zhang Furong Shi Yuchen Bai Xiaoli Wang 《Phosphorus, sulfur, and silicon and the related elements》2013,188(4):519-529
Abstract A six-coordinate picrate nickel(II) complex based on the V-shaped ligand 1,3-bis(1-benzylbenzimidazol-2-yl)-2-thiapropane (L), with the composition [Ni(L)2](pic)2, has been synthesized and characterized systematically. The crystal structure of the Ni(II) complex is a six-coordinated octahedron, which is considerably close to ideal octahedral geometry with N4S2 donors of the two ligands. Biological activities of compounds were investigated using electronic absorption spectroscopy, fluorescence spectroscopy, and viscosity measurements. The results suggested that both ligand L and Ni(II) complex bind to DNA in an intercalative binding mode, and DNA-binding affinity of the Ni(II) complex is stronger than that of ligand L. [Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental files: Additional figures.] 相似文献
760.
Jin Luo Shu Li Qiongwen Kang Yi Sun 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):1180-1186
AbstractSixteen novel 3-methylthio-5-substituted benzamido-6-arylamino-1-phenyl-1H-pyrazolo[3,4-d]pyrimidin-4 (5H)-one derivatives (4a–p) were successfully synthesized from iminophosphoranes, aryl isocyanate, and substituted benzoylhydrazine. The structures of the title compounds were elucidated by FT-IR, 1H NMR, 13C NMR, and HRMS. Herbicidal activity of the compounds 4a–p against Brassica napus (rape), Echinochloa crusgalli (barnyard grass), Cucumis sativus (cucumber), and Triticum aestivum (wheat) were determined. The results showed that 5-(2-chlorobenzamido)-6-phenylamino-3-methylthio-1-phenyl-1H-pyrazolo[3,4-d]pyrimidin-4 (5H)-one (4c) displayed remarkable inhibition activity against the stalk and root of rape with 100% inhibition rate at the dosages of 10?mg/L and 100?mg/L, and 5-(4-nitrobenzamido)-6-phenylamino-3-methylthio-1-phenyl-1H-pyrazolo[3,4-d]pyrimidin-4 (5H) -one (4d) exhibited excellent activity against the stalk and root of barnyard grass with 100% inhibition rate at the same dosages. 相似文献