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71.
The capillary gas chromatographic behaviour of diethylhydrogensilyl (DEHS) ethers and/or diethylsilylene (DES) derivatives of fifty bile acids including 4- and 6-hydroxylated compounds is described. The methylene unit (MU) values of methyl and pentafluorobenzyl esters of bile acids were determined as their trimethylsilyl (TMS), dimethylethylsilyl (DMES) ethers and DEHS-DES derivatives. The differences in methylene unit values between the corresponding TMS ethers and DMES ethers or DEHS-DES derivatives were used for estimating the number and stereochemistry of hydroxyl groups on the steroid nucleus. On treatment with the silylating agent N,O-bis (diethylhydrogensilyl)trifluoroacetamide, bile acids possessing isolated hydroxyl in addition to diaxial trans-glycol groups were easily converted into the DEHS ehters, whereas those having a vicinal glycol group except for the diaxial group were converted into cyclic DES derivatives. The mass spectrometric properties obtained with negative-ion chemical ionization detection are discussed. 相似文献
72.
Y. Hatsukawa Y. Miyamoto Y. Toh M. Oshima M. Hosein Mahmudy Gharaie K. Goto K. Toyoda 《Journal of Radioanalytical and Nuclear Chemistry》2007,272(2):273-276
In this study, using neutron activation analysis with multi-parameter coincidence method which was developed at Japan Atomic
Energy Agency (JAEA), a non-destructive, ultra-high sensitive multi-elemental determination has been realized. The multi-parameter
coincidence method is carried out with an array of 19 germanium detectors, GEMINI-II. Using this system, very weak γ-rays
emitted from trace amounts of elements can be detected. The iridium concentration has been determined by means of neutron
activation analysis with multi-parameter coincidence method for Cuban sediment samples across the K/T boundary strata. 相似文献
73.
74.
The mechanisms of nitrosation of acetone through sodium enolate [CH3CO1CH2]-Na+ (1) or naked enolate [CH3CO1CH2]- (2) with methyl nitrite CH3O3NO2 (3), and the reactivity of the syn-form of 3 (syn-3) during the C-N bond formation process were investigated using ab initio molecular orbital (MO) methods. Our results have demonstrated the predominant formation of E-1-hydroxyimino-2-oxo-propane CH3COCH=NOH (4E) when the complex [CH3CO1CH2NO2(O3CH3)]-Na+ was produced kinetically via a metal-chelated pericyclic transition state (TS(CHELATED)), in which the O3 atom of syn-3 was coordinated to the Na+ atom of 1. 相似文献
75.
T. Hondoh H. Anzai A. Goto S. Mae A. Higashi C. C. Langway Jr. 《Journal of inclusion phenomena and macrocyclic chemistry》1990,8(1-2):17-24
We have carried out X-ray diffraction studies on single crystals of natural air-hydrate in deep ice cores recovered at Dye-3 Greenland. Integrated intensities for 470 diffracting planes were measured by an automated four-circle diffractometer. The space group determined is cubicFd3m and the lattice constant is 17.21(3) Å. These results indicate that the crystallographic structure is the Stackelberg's structure II, in contrast to the previously anticipated structure. This finding agrees with the recent results on the synthetic air-hydrate by Davidsonet al. It was also found by difference Fourier synthesis for guest molecules that electron density in a 16-hedral cage has multiple maxima displaced from the center of the cage while that in the 12-hedron was approximately spherical.Dedicated to Dr D. W. Davidson in honor of his great contributions to the sciences of inclusion phenomena. 相似文献
76.
Yoshihisa Kurasawa Ho Sik Kim Keiko Yonekura Atsushi Takada Yoshihisa Okamoto 《Journal of heterocyclic chemistry》1989,26(3):857-859
3-(Pyrazolylhydrazonomethyl)-2-oxo-1, 2-dihydroquinoxalines were synthesized, and their tautomer ratios between hydrazone imine and diazenyl enamine forms were specified by pmr spectral data. 相似文献
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