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171.
In the presence of DABCO (30 mol%), the addition of various selenosulfonates to alpha,beta-unsaturated ketones proceeded smoothly to give the corresponding adducts in good yields under mild conditions. 相似文献
172.
Three modified procedures for the separation of cardiac myosin light chains are carefully compared. Ion-exchange chromatography gives a purified cardiac myosin light chain 1, whereas light chain 2 is always contaminated by light chain 1. Reversed-phase high-performance liquid chromatography gives the best resolution of these light chains and needs only 20 min for each run. However, it requires pure preparation of myosin light chains before separation. Isoelectric precipitation is the simplest procedure and suitable for large quantities of material. Although it gives the highest yield the separation is not adequate. A modified and rapid procedure for the isolation of cardiac and skeletal total myosin light chains is also presented. 相似文献
173.
174.
A novel and practical procedure was developed for the abnormal Beckmann rearrangement of steroid 17-oximes. Treatment of the 17-oximes with TFA/CH(OMe)(3) in boiling THF for 2 h gives the corresponding 13,17-seco alkene nitrile products in unprecedented high yields (70-92%). Since the alkene nitriles can be subsequently converted into 18-norsteroids, this general method provides a highly efficient route to these biologically important compounds and, by extension, to other structurally related natural products. 相似文献
175.
Intramolecular proton transfer equilibria of acetamide and methyl carbamate have been studied by AMI MO calculations, and the results are compared with those of the MNDO method. It was found that the two semi- empirical methods predict essentially the same proton transfer mechanism, but MNDO tends to overestimate the activation barriers. Participation of one solvate vater in the proton transfer led to a considerable lovering of the activation barrier, by nearly the same amount, in both methods. One notable conflict between the two methods was that the methoxy-O-protonated form of methyl carbamate, in the gas phase, can be a local energy minimum with MNDO, whereas it leads to dissociation into two species Instead of an optimized structure with AM1. It was concluded that the MNDO method can be useful for this type of process, especially when one is interested in the relative activation barriers only. 相似文献
176.
Zhan‐Xin Zhang Wei‐Dong Xie Ping‐Lin Li Yan‐Ping Shi Zhong‐Jian Jia 《Helvetica chimica acta》2006,89(12):2927-2933
Six new compounds were isolated from the whole plant of Sonchus uliginosus, including three eudesmane‐type sesquiterpenoids (1β,6α)‐1,6,14‐trihydroxyeudesm‐3‐en‐12‐oic acid γ‐lactone ( 1 ), (1β,6α)‐1,6,14‐trihydroxyeudesma‐3,11(13)‐dien‐12‐oic acid γ‐lactone ( 2 ), and (1β,6α)‐1,6‐dihydroxy‐14‐O‐[(4‐hydroxyphenyl)acetyl]eudesma‐3,11(13)‐dien‐12‐oic acid γ‐lactone ( 3 ), and three phenylpropane derivatives, 4‐hydroxy‐γ,3,5‐trimethoxybenzenepropanol ( 6 ), γ,3,4,5‐tetramethoxybenzenepropanol ( 7 ), and γ,3,4,5‐tetramethoxybenzenepropanol acetate ( 8 ), together with the two known compounds 4 and 5 . The new structures were elucidated by means of spectroscopic methods, such as IR, EI‐MS, HR‐ESI‐MS, 1D‐ and 2D‐NMR, and by comparison of the spectroscopic data with those reported for structurally related compounds. 相似文献
177.
掺杂阴离子对电化学合成的聚邻甲苯胺性质的影响 总被引:3,自引:0,他引:3
邻甲苯胺在酸性介质中的聚合速率与酸的种类有关,聚合速率影响了各种掺杂阴离子聚合物膜的形态,聚合物的电导率、循环伏安曲线形状受掺杂阴离子的影响,其电容量与掺杂阴离子的种类及形态有关,阴离子的种类对电极电位和紫外-可见光谱无影响。 相似文献
178.
Yao‐Cheng Shi Bei‐Bei Zhu Xiao‐Bi Jing 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(11):m559-m562
The molecules of N,N′‐bis(2‐pyridylmethyl)ferrocene‐1,1′‐diyldicarboxamide, [Fe(C12H11N2O)2], contain intramolecular N—H⋯N hydrogen bonds and are linked into sheets by three independent C—H⋯O hydrogen bonds. The molecules of the isomeric compound N,N′‐bis(3‐pyridylmethyl)ferrocene‐1,1′‐diyldicarboxamide lie across inversion centres, and the molecules are linked into sheets by a combination of N—H⋯N hydrogen bonds and π–π stacking interactions between pyridyl groups. 相似文献
179.
Ya-Guang Chen Fan-Xia Meng Hai-Jun Pang Dong-Mei Shi Yu Sun 《Journal of Cluster Science》2007,18(2):396-405
A novel uranyl complex with dimeric lacunary polyoxoanion like open-mouthed clam, Na5[(A-α-SiW9O33H3)2K{UO2(H2O)}2], was prepared and characterized by elemental analysis, infrared and ultraviolet–visible spectroscopy and single crystal
X-ray diffraction. In the anion, two A-α-SiW9O3410− groups share two terminal oxygen atoms Od′ derived from removal of three corner-shared W atoms from saturated α-Keggin anion, forming a dimeric anion with an open
mouth in which potassium ion and uranyl ions are coordinated. Uranium atom adopts a pentagonal bipyramidal geometry. The coordinating
anions are linked by sodium ions via coordination of terminal or bridging oxygen atoms, forming two-dimensional layer arrangement.
Between the layers are the hydrogen bonds from which a supramolecular architecture is created. UV–VIS spectrum gives W–O and
U–O charge transfer transitions at 230–265 and 432 nm, showing the change of geometry of the polyanion and weakening of the
U–O bonds of the uranyl cation.
Electronic supplementary material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
180.
生物检材中乌头类生物碱的检验 总被引:2,自引:1,他引:2
用薄层 (TLC)、高效液相 光电二极管阵列检测器 (HPLC/DAD)、动物实验等方法对生物检材中乌头生物碱进行检验 ,并对这些方法进行比较。结果发现 ,TLC法为此类药物检验筛选的首选方法 ,最小检出量为 0 3μg。在进行HPLC检测时 ,以乌头生物碱的特征紫外吸收光谱和动物实验结果为重要的定性手段 ,其特征吸收波长为 (2 2 8± 2 )nm和 (2 75± 2 )nm。乌头生物碱在 2mg/L~ 5 0mg/L时其峰面积与质量浓度有很好的线性 ,相关系数为 0 9996。经实际案件证明 ,方法准确、灵敏 ,可用于生物检材中乌头类生物碱的检验。 相似文献