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991.
992.
993.
994.
Three diastereomers of (1S) 3-3′-di-t-butyl-1,1′-spirobi [benz[f] indan] have been prepared. In the 1Bb region all the isomers showed typical c.d. couplets of negative sign, reflecting the identity of configuration at the spiro center irrespective of their different conformations. 相似文献
995.
The structure elucidation of FR-900098 () isolated from a microorganism source and the syntheses of FR-900098 and its N-formyl analogue, FR-31564 (), are described. The latter possesses a superior antimicrobial activity. 相似文献
996.
Thermal decomposition of N(phenylsulfonyl)-benzohydrazonoyl chloride (1) in refluxing toluene generated N-phenylsulfonylbenzonitrilimine (2) which gave 1,3-dipolar cycloadducts with ethyl (4a) and methyl acrylate (4b), acrylonitrile (4c), styrene (4d), norbornene (4e), and norbornadiene (4f). The reactions with 4a–d, 2 afforded regiospecifically 5-R substituted pyrazolines 5a–d in lower yields. The raction of 2 with 4e gave only exo adduct 5e, while the reaction with 4f gave both exo- (5fx) and endo adducts (5fn) as well as their retro-Diels-Alder product 6. 相似文献
997.
Shintaro Sasaki Takao Nakamura Ichitaro Uematsu 《Journal of Polymer Science.Polymer Physics》1979,17(5):825-835
A thermally reversible crystal transition was found for γ-helical poly(γ-n-alkyl L -glutamate)s (alkyl = ethyl, propyl, butyl, and amyl). The transition temperature is higher than that of the side-chain mechanical dispersion, and decreases from 115 to ?5°C, as the alkyl groups become longer. The transition in poly(γ-n-propyl L -glutamate) is clearly first order. The structures were analyzed by x-ray diffraction at various temperatures. It is noteworthy that the pseudohexagonal form observed below the transition temperature is less ordered than the hexagonal form at higher temperatures. The mechanism of this transition is discussed. 相似文献
998.
Hisaaki Kanetsuna Masaki Hasegawa Shigenobu Mitsuhashi Toshio Kurita Kanji Sasaki Katsuhiro Maeda Hiroko Obata Tatsuko Hatakeyama 《Journal of Polymer Science.Polymer Physics》1970,8(7):1027-1037
Poly-2,5-distyrylpyrazine (poly-DSP) was investigated by differential thermal analysis (DTA), thermogravimetric analysis (TGA), and measurements of dynamic viscoelastic and electrical properties. From DTA and TGA studies it was confirmed that poly-DSP melts at 321°C and depolymerizes rapidly to the monomer at temperatures between 335°C and 345°C in helium. The polymer is affected by oxygen above 200°C. The E′ value from dynamic viscoelasticity measurements on amorphous film is 2 × 1011 dyne/cm2 at room temperature. It decrease abruptly in the temperature range 140–150°C; but the net decrease of E′ within this temperature range is relatively small. The electrical properties of amorphous poly-DSP are characterized by a small temperature dependence of the dielectric constant between room temperature and 100°C. The dielectric loss tangent was observed to be small, and the dc conductivity was extremely small. It is concluded that rotation of the phenyl branches in the polymer occurs above ?30°C and the glass transition occurs at about 150°C. These properties are discussed in some detail in relation to the polymer structure. 相似文献
999.
R. Sasaki 《Nuclear Physics B》1978,142(4):463-476
Some new classical solutions of the sourceless SO(4,1) gauge field equations are found by identifying the internal symmetry indices with the space-time indices as in the cases of the instanton or the meron solutions. This identification of the internal and the space-time indices takes the simplest form when the gauge field equation is expressed in (4,1) de Sitter space, which is conformal to the Minkowski space having the de Sitter group SO(4,1) as a group of motions. The form of the solutions is close to the de Sitter ‘plane wave’ solutions found recently, i.e. the solutions of the Klein-Gordon, Dirac and Maxwell-Proca equations in de Sitter space. The group theoretical structure of the new solutions is discussed and their relations to the Iwasawa decomposition of the non-compact semisimple group SO(4,1) are pointed out. 相似文献
1000.
The structures of the oxidation products of 5,6-diphenyl-as-triazine-3(2H)-ones (Ia-b) with organic peracids were chemically and spectroscopically reinvestigated and it was concluded that the products were 1,4-dibenzoyl semicarbazide (IIa) and the 2-methyl analogue (IIb). 相似文献