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71.
It is shown that heating vinylacetylenic piperidols I with phosphorus oxychloride in pyridine solution gives dienynes II, the structure of which is determined, in the case of II (R=H), by means of IR spectra and PMR. Hydration of the dienynes II (R=H, Me) in the presence of mercuric sulfate in methanol solution gives -methoxyketones III (R=H, Me). It is also shown that III and aqueous solutions of ammonia or primary amines give the bicyclic piperid-4-ones IV. In the synthesis of IV (R=H, R1 = i-Pr, Bu) imines V are obtained, which on hydrolysis give piperidones IV (R = H, R1 = i-Pr, Bu). When the ß-methoxyketone III (R = H) is heated with 5% sulfuric acid in the presence of mercuric sulfate, chroman-4-one is formed. 相似文献
72.
M. I. Merlani L. Sh. Amiranashvili K. G. Mulkidzhanyan E. P. Kemertelidze 《Chemistry of Natural Compounds》2006,42(3):322-324
Certain 17β-aminoderivatives of 5α-steroids based on tigogenin were synthesized and their antitumor activity was studied. The structures of the synthesized
compounds were confirmed by NMR and IR spectroscopy and mass spectrometry.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 263–265, May–June, 2006. 相似文献
73.
Manabe K Iimura S Sun XM Kobayashi S 《Journal of the American Chemical Society》2002,124(40):11971-11978
Dehydration reactions in water have been realized by a surfactant-type catalyst, dodecylbenzenesulfonic acid (DBSA). These reactions include dehydrative esterification, etherification, thioetherification, and dithioacetalization. In these reactions, DBSA and substrates form emulsion droplets whose interior is hydrophobic enough to exclude water molecules generated during the reactions. Detailed studies on the esterification revealed that the yields of esters were affected by temperature, amounts of DBSA used, and the substrates. Esters were obtained in high yields for highly hydrophobic substrates. On the basis of the difference in hydrophobicity of the substrates, unique selective esterification and etherification in water were attained. Furthermore, chemospecific, three-component reactions under DBSA-catalyzed conditions were also found to proceed smoothly. This work not only may lead to environmentally benign systems but also will provide a new aspect of organic chemistry in water. 相似文献
74.
The new alkaloid oxytriphine, the parent of natural 2-oxazoline derivatives, has been isolated from the epigeal part ofOxytropis trichophysa; and its structure has been established as (5S)-(+)-2,5-diphenyl-2-oxazoline. (-)-N-Benzoyl-2-phenyl-2-hydroxyethylamine and benzoic acid have been detected in this plant for the first time. A hypothesis of the possible biogenetic interrelationship of the compounds isolated is put forward.Institute of the Chemistry of Plant Substances. Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii. No. 6, pp. 873–876, November–December, 1993. 相似文献
75.
H. Nitsche R. C. Gatti Sh. C. Lee 《Journal of Radioanalytical and Nuclear Chemistry》1992,161(2):401-411
We have developed an analytical method for detection of239Pu in aqueous samples at concentrations as low as 10–10M. This nuclear counting technique utilizes the uranium L X-rays, which follow the alpha-decay of plutonium. Because L X-rays are specific for the element and not for the individual isotope, the isotopic composition of the plutonium sample must be known. The counting efficiency in the 11–23 keV range is determined from a plutonium standard, and the concentration of the sample is then calculated from the L X-ray count and the isotopic composition. The total L X-ray count is corrected for possible contributions from other radionuclides present as impurities by measuring the low-energy gamma-spectrum for each contaminant to establish specific photon/X-ray ratios. The ratios are important when241Pu and242Pu are measured, because the respective decay chain members produce non-U L X-rays. This new method can replace the use of labor-intensive radiochemical separation techniques and elaborate activation methods for analysis of239Pu in aqueous samples. It is also applicable for assaying plutonium in liquid wastes that pose possible hazards to the environment. 相似文献
76.
In the mass spectra of unsubstituted monosides of cardenolide nature are observed the M+ peaks, and also, in each case, three characteristic processes of the fragmentation of the carbohydrate unit. The formation of the ions AglOCH=OH+ is the most universal property of these compounds. The stability of ions of the type under consideration depends on the nature and position of attachment of the sugar residue and on the number of polar groups in the aglycone. The laws of the fragmentation of the carbohydrate unit are extended to the spectra of glycosides of other classes.Deceased.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodynykh Soedinenii, No. 3, pp. 345–354, 1983. 相似文献
77.
Krasnov V. P. Levit G. L. Korolyova M. A. Bukrina I. M. Sadretdinova L. Sh. Andreeva I. N. Charushin V. N. Chupakhin O. N. 《Russian Chemical Bulletin》2004,53(6):1253-1256
The influence of the reaction conditions (solvent, base) on the diastereoselectivity of acylation of (±)-3-methyl-2,3-dihydro-4H-1,4-benzoxazine with (S)-naproxen and N-tosyl-(S)-proline chlorides was studied. The highest diastereoselectivity was observed for the reaction carried out in benzene in the presence of aliphatic tertiary amines. 相似文献
78.
V. A. Mamedov A. A. Kalinin V. V. Yanilkin N. V. Nastapova V. I. Morozov A. A. Balandina A. T. Gubaidullin O. G. Isaikina A. V. Chernova Sh. K. Latypov I. A. Litvinov 《Russian Chemical Bulletin》2007,56(10):2060-2073
The oxidative dehydrocyclization of the 3-(indolizin-2′-yl)-2-oxoquinoxaline monopodand performed either electrochemically
or under the action of molecular iodine affords new redox-active heterocyclophane consisting of the redox-switchable biindolizine
fragment combined with the polyether-bridged π-deficient quinoxaline systems. The single-crystal X-ray diffraction study showed
that the trioxaundecane chain of heterocyclophane adopts an extended conformation, and one of the phenyl substituents of the
molecule closes the pseudocavity formed by the spacer from one of the sides. The cyclic voltammetric study of heterocyclophane
in MeCN and DMF showed the three-step oxidation of the indolizine fragments accompanied by the single-electron transfer in
each step. The first and third steps are reversible, and the second step is irreversible. The oxidation at potentials of the
first peak gives rise to stable radical cations detected by the ESR method (g = 2.0024, a
2N = 0.26 mT).
Dedicated to Professor E. A. Berdnikov on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1991–2003, October, 2007. 相似文献
79.
V. O. Kudyshkin S. Sh. Rashidova A. V. Surdina M. Yu. Zaremski V. B. Golubev 《Polymer Science Series B》2007,49(11-12):297-300
The polymerization of N-vinylpyrrolidone has been studied in the presence of the stable radical 2,2,6,6-tetramethyl-1-piperidinyloxy. It has been shown that at 120°C the polymerization proceeds via the irreversible inhibition mechanism, while, at 60°C, secondary inhibition occurs in the system during the postinduction period. This effect may be used for regulation of the molecular-mass characteristics of polymers. 相似文献
80.
It has been shown by electrophoresis in polyacrylamide gel that different enzymes with similar electrophoretic mobilities may be localized in one and the same zone of water-soluble cottonseed proteins. Some zones not stained by the usual protein dyes also possess enzymatic activity. It has been established that the majority of the electrophoretic fractions consist of a series of polypeptides with different molecular weights, mainly of low-molecular-weight nature. The results are given of an investigation of the peroxidase, α-amylase, lipase, NADH-DCPIP oxidoreductase, and NADPH-DCPIP oxidoreductase activities of the water soluble fraction of the proteins of the seeds of the species mentioned. 相似文献