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991.
Ya. S. Kayukov P. M. Lukin O. E. Nasakin V. N. Khrustalev V. N. Nesterov M. Yu. Antipin V. V. Sheverdov 《Chemistry of Heterocyclic Compounds》1997,33(4):423-425
It has been established by x-ray structural analysis that on reacting 4-oxoalkane-1,1,2,2-tetracarbonitriles with aldehydes
6-imino-2,7-dioxabicyclo[3.2.1]octane-4,4,5-tricarbonitriles are formed and not 3-imino-2,6-dioxabicyclo[2,2,2] octane-4,8,8-tricarbonitriles
as has been proposed.
Chuvash State University, Cheboksary 428015. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 497–499,
April, 1997. 相似文献
992.
Nian Yun YANG Shi Hui QIAN Jin Ao DUAN Ping LI Li Juan TIAN Jiangsu Academy of Traditional Chinese Medicine Nanjing China Pharmaceutical University Nanjing Jinling Pharmaceutical Company Limited Nanjing 《中国化学快报》2005,16(9)
Various germacrane sesquiterpenes have been isolated from many species of the Eupatorium.In recent years these compounds have been increasing interest due to their insecticidal,cytotoxic,antitumor-promoting and insect-antifeedant activities1.In our present study,we have investigated the chemical constituents of Eupatorium lindleyanum DC.,which is a geo-authentic medicine of Jiangsu province.It is used as a antipyretic drug.Two novel germacrane sesquiterpenes(Figure1)were found by us from th… 相似文献
993.
Misochko EY Akimov AV Goldschleger IU Tyurin DA Laikov DN 《The Journal of chemical physics》2005,122(3):34503
Xenon fluoride radicals were generated by solid-state chemical reactions of mobile fluorine atoms with xenon atoms trapped in Ar matrix. Highly resolved electron spin resonance spectra of XeF* were obtained in the temperature range of 5-25 K and the anisotropic hyperfine parameters were determined for magnetic nuclei 19F, 129Xe, and 131Xe using naturally occurring and isotopically enriched xenon. Signs of parallel and perpendicular hyperfine components were established from analysis of temperature changes in the spectra and from numerical solutions of the spin Hamiltonian for two nonequivalent magnetic nuclei. Thus, the complete set of components of hyperfine- and g-factor tensors of XeF* were obtained: 19F (Aiso=435, Adip=1249 MHz) and 129Xe (Aiso=-1340, Adip=-485 MHz); g(parallel)=1.9822 and g(perpendicular)=2.0570. Comparison of the measured hyperfine parameters with those predicted by density-functional theory (DFT) calculations indicates, that relativistic DFT gives true electron spin distribution in the 2Sigma+ ground-state, whereas nonrelativistic theory underestimates dramatically the electron-nuclear contact Fermi interaction (Aiso) on the Xe atom. Analysis of the obtained magnetic-dipole interaction constants (Adip) shows that fluorine 2p and xenon 5p atomic orbitals make a major contribution to the spin density distribution in XeF*. Both relativistic and nonrelativistic calculations give close magnetic-dipole interaction constants, which are in agreement with the measured values. The other relativistic feature is considerable anisotropy of g-tensor, which results from spin-orbit interaction. The orbital contribution appears due to mixing of the ionic 2Pi states with the 2Sigma+ ground state, and the spin-orbit interaction plays a significant role in the chemical bonding of XeF*. 相似文献
994.
Xiao‐Yan Chen Peng Cheng Shi‐Ping Yan Dai‐Zheng Liao Zong‐Hui Jiang 《无机化学与普通化学杂志》2005,631(15):3104-3107
A novel two‐dimensional cobalt complex, [Co(btrm)2(dca)]ClO4 ( 1 , btrm = 1,2‐bis(1,2,4‐triazole‐1‐yl)methane, dca = dicyanamide), was synthesized and characterized. X‐ray diffraction analyses reveal that the title complex crystallizes in the monoclinic space group C2/m with a = 29.507(13)Å, b = 17.804(8) Å, c = 14.709(7) Å, β = 119.916(7)°, Z = 12, and R1 = 0.0784, wR2 = 0.2041. The cobalt atom involves a six‐coordinated CoN6 environment, with a distorted octahedral coordination. Two btrm ligands connect the CoII atoms with the exodentate nitrogen atoms on the 4‐position of triazole rings to form a sixteen‐membered rhombic grid. The unprecedented double btrm bridges and μ1,5‐dca bridge connect the cobalt atoms to form a two‐dimensional grid‐like layered structure. The spectroscopic and magnetic properties have also been investigated. 相似文献
995.
Sheiman B. M. Yuzefovich L. Yu. Denisova L. Ya. Filippova T. M. Mairanovskii V. G. Berezovakii V. M. 《Chemistry of Heterocyclic Compounds》1977,13(5):511-515
The constants and thermodynamic parameters of the ring-chain tautomeric equilibrium of p-substituted (benzene ring) 2,3,3-trimethyl-1-aryl-2-hydroxy-5-pyrrolidones in aqueous pyridine solution were determined by PMR spectroscopy. Conversion of the ring tautomer to the open form is accompanied by an increase in the enthalpy and entropy. The AH value decreases by a factor of 2.8 kcal/mole on passing from electron-donor substituents to electron-acceptor substituants, whereas the AS value remains approximately constant and decreases by 2–4 eu only for strong electron acceptors (COOCH3, CN, and NO2). The correlation between the free energies and the a substituent constants in the benzene ring is discussed.See [1] for communication XII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 634–638, May, 1977. 相似文献
996.
997.
O. A. Drozdova S. A. Avilov A. I. Kalinovskii V. A. Stonik Yu. M. Mil'grom Ya. V. Rashkes 《Chemistry of Natural Compounds》1993,29(2):200-205
Four new compounds have been isolated from the fraction of weakly polar triterpene glycosides of the holothurianCucumaria japonica: cucumariosides A1-2 (I), A0-1 (II), A0-2 (III), and A0-3 (IV). The structures of these substances have been established by chemical and physical methods.Deceased.Pacific Ocean Institute of Bioorganic Chemistry, Far-Eastern Scientific Center, Russian Academy of Sciences, Vladivostok. Institute of Chemistry of Plant Substances, Uzbekistan Republic Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 242–248, March–April, 1993. 相似文献
998.
The complete gene coding for human neutrophilactivating protein-1/interleukin-8 was synthesized using a semi-chemical semi-enzymatic method. The synthetic gene was then overexpressed in Escherichia coli under the temperature-regulated control of the P_RP_L tandem promoters. As determined by SDS-PAGE and densitometry, the overexpressed protein comprised up to 18.5% and 10.9% of the total soluble protein in E. coli cells grown in shake flasks and in batch fermentation, respectively. The recombinant NAP-1/IL-8 was then purified to>95% homogeneity by gel filtration and cation exchange chromatography. The purified protein appeared as a single band on the SDS-PAGE gel and possessed potent chemotactic activity in the concentration of <10 ng/ml, as assayed by the agarose plate method. An early skin reactivity was also observed when the pure NAP-1/IL-8 was injected subcutaneously into the rabbits. The N-terminal 36 amino acid sequence of the recombinant NAP1/IL-8 was determined using the Edman method and was sho 相似文献
999.
K. V. Shcherbakov Ya. V. Burgart V. I. Saloutin 《Russian Journal of Organic Chemistry》2006,42(12):1838-1844
5,6,7,8-Tetrafluoro-4-hydroxy-2H-chromen-2-one reacts with methylamine to give methylammonium 5,6,7,8-tetrafluoro-2-oxo-2H-chromen-4-olate, regardless of the solvent. The reaction of 3-acetyl-5,6,7,8-tetrafluoro-4-hydroxy-2H-chromen-2-one with the same amine in ethanol or acetonitrile leads to the formation of methylammonium 3-acetyl-5,6,7,8-tetrafluoro-2-oxo-2H-chromen-4-olate, while in dimethyl sulfoxide 5,6,8-trifluoro-7-methylamino-3-(1-methylaminoethylidene)-3,4-dihydro-2H-chromene-2,4-dione is formed. The latter is also formed in the reaction of 5,6,7,8-tetrafluoro-4-hydroxy-3-(1-iminoethyl)-2H-chromen-2-one with methylamine in DMSO, whereas in ethanol and acetonitrile 5,6,7,8-tetrafluoro-3-(1-methylaminoethylidene)-3,4-dihydro-2H-chromene-2,4-dione is obtained. 5,6,7,8-Tetrafluoro-3-(1-methylaminoethylidene)-3,4-dihydro-2H-chromene-2,4-dione reacts with methylamine, yielding 7-mono-or 5,7-bis(methylamino)-substituted derivatives. 相似文献
1000.
A. A. Loloiko V. I. Grishkovets A. S. Shashkov V. Ya. Chirva 《Chemistry of Natural Compounds》1988,24(3):320-323
Two triterpene glycosides have been isolated from the leaves ofHedera taurica Carr. (Crimean ivy), family Araliaceae — taurosides B and C, for which, on the basis of the results of chemical and physicochemical methods of investigation the following structures are proposed: 3-0--L-arabinopyranosylhederagenin and 3-0-[0--L-rhamnopyranosyl-(1 2)--L-arabinopyranosyl]oleanolic acid.M. V. Frunze Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 379–382, May–June, 1988. 相似文献