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951.
Mycothiazole isolated from marine sponges has been efficiently synthesized in a convergent manner. The key reactions involve the thiazole synthesis by dehydrogenation of the thiazolidine with chemical manganese dioxide (CMD), the Stille coupling, and the Nagao asymmetric acetate aldol reaction using the chiral 1,3-thiazolidine-2-thione. This synthesis clearly established the absolute configuration of natural mycothiazole to be (R). 相似文献
952.
Kasajima N Ito H Hatano T Yoshida T Kaneda M 《Chemical & pharmaceutical bulletin》2005,53(10):1345-1347
Three new acylated flavonol glycosides, cypellogins A (1), B (2) and C (3), along with eight known phenolic compounds, were isolated from the dried leaves of Eucalyptus cypellocarpa, and their structures were elucidated using spectroscopic methods, including 2D NMR experiments and chemical evidence. 相似文献
953.
Hirohisa Yoshida 《Journal of Thermal Analysis and Calorimetry》1997,49(1):101-105
Conformational formation and crystallization dynamics of miscible PVDF/at-PMMA and PVDF/iso-PMMA polymer blends from the molten state were studied by the simultaneous DSC/FT-IR measurement. Formation of TGTG' conformation occurred before starting crystallization exothermic peak in the PMMA content (PMMA) range from 0 to 0.4 for both blends. The formation rate of TGTG' conformation, crystal growth rate and surface free energy of PVDF crystal in blends depended linearly on PMMA for PVDF/at-PMMA, however, those rates for PVDF/iso-PMMA slightly influenced by PMMA. These results suggested that the former was miscible blend in molecular level, however, the latter was a miscible blend with large concentration fluctuation or a partially segregated system. 相似文献
954.
955.
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957.
T.G. Appleton M.A. Bennett A. Singh T. Yoshida 《Journal of organometallic chemistry》1978,154(3):369-385
The reactions of various alkyne-platinum(0) complexes with methyl iodide and with iodine have been studied. The 3-hexyne complex Pt(C2H5C2C2H5)(PPh3)2 gives alkyne-free oxidative addition products PtI(CH3) (PPh3)2 and PtI2 (PPh3)2 exclusively. In contrast, the strained cyclic alkyne complexes Pt(C6H8)(PPh3)2, Pt(C7H10)(PPh3)2, Pt(C6H8) (dppe) and Pt(C7H10) (dppe)1 react with methyl iodide to give mainly 2-methylcycloalkenyiplatinum(II) complexes, e.g. PtI(C6H8CH3) (PPh3)2, formed by electrophilic attack on the metal-alkyne bond. Iodine reacts similarly with Pt(C6H8) (PPh3)2 and Pt(C7H10) (PPh3)2 to give 2-iodocycloalkenylplatinum(II) complexes but, in the case of the corresponding dppe complexes, PtI2(dppe) is the main product. The insertion reaction of methyl iodide with Pt(C6H8)(PPh3)2 proceeds via an oxidative addition intermediate PtI(CH3) (C6H8) (PPh3)2 which can be isolated. Trifluoromethyl iodide reacts with Pt(C6H8)(PPh3)2 to give a 2-iodocyclohexenyl complex Pt(CF3) (C6H8I) (PPh3)2 and with Pt(C7H10) (PPh3)2 to give PtI(CF3) (PPh3)2. 31P NMR data are given and discussed. 相似文献
958.
Theoretical study of the structure and optical properties of carbon-doped rutile and anatase titanium oxides 总被引:1,自引:0,他引:1
The structure and optical properties of carbon-doped titanium oxides, TiO2, in the rutile and anatase forms have been investigated theoretically from first principles. Two possible doping sites were studied, carbon at an oxygen site (anion doping) and carbon at a titanium site (cation doping). The calculated structures suggest that cation-doped carbon atoms form a carbonate-type structure, whereas anion-doped carbon atoms do not invoke any significant structural change. A density-of-states analysis revealed three in-gap impurity states for anion doping. The optical properties of anion-doped cells qualitatively agree with the experimentally reported visible-light absorbance values. We ascribe part of the absorption to transitions from the valence band to one of the impurity states. These transitions should be able to promote photocatalytic reactions, because electron holes in the valence band are considered to be crucial for this process. Neither in-gap impurity states nor visible-light absorbance were observed in the case of cation doping. The effect of oxygen vacancies was also investigated. Introduction of oxygen vacancies into anion-doped TiO2 populates the impurity states and thus suppresses photocatalysis. The interaction of a doped carbon atom with an oxygen vacancy at a finite spatial separation was also carried out. The possibility of either a carbon-oxygen vacancy pair or higher carbon-oxygen vacancy complex existing is discussed. 相似文献
959.
T. Kitagawa M. Abe Y. Kyogoku H. Ogoshi H. Sugimoto Z. Yoshida 《Chemical physics letters》1977,48(1):55-58
Resonance Raman spectra of 15N enriched metallooctaethylporphyrins [M(OEP) ? 15N4] [M = Ni2+, Fe3+ (high spin), and Fe3+ (low spin)] were observed. Polarized Raman lines corresponding to the oxidation state marker band of hemoproteins were observed at 1377 (Ni), 1369 (Fe high spin) and 1372?1 (Fe low spin) which were shifted to lower frequency from those of the 14N compounds by 6, 5, and 6 cm?1, respectively. The vibrational mode for this band was shown to include an appreciable contribution of the CαN symmetric stretching vibration and to be associated with ca. 0.01 Å of in-phase displacement of the four pyrrole nitrogens toward the metal ion. 相似文献
960.
Jinhua Chen Yasunari Maekawa Masaru Yoshida Norio Tsubokawa 《Journal of Polymer Science.Polymer Physics》2002,40(1):134-141
A series of thermoresponsive polymer gel electrolytes (PGEs) based on poly(N‐isopropylacrylamide) in aqueous potassium chloride was synthesized by radiation‐induced polymerization and gelation using γ rays from a 60Co source. The electric conductivity and swelling properties of the PGE were determined as a function of temperature. It was found that the electric conductivity of the PGE depended strongly on the swelling ratio; most notably, it changed drastically near the volume phase‐transition temperature of the PGE. The temperature/conductivity profile of the PGE exhibits a maximum peak at a certain temperature that is defined as the maximum conductivity temperature (Tmax). The Tmax of all of the PGEs prepared by low‐dose irradiation agreed with the temperature, near the end of the volume phase transition, where the PGE was completely shrunken. Consequently, the conductivity of gels should provide a good method with which the totally shrunken temperature of the thermoresponsive gels can be monitored with good temperature precision. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 134–141, 2002 相似文献