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排序方式: 共有362条查询结果,搜索用时 62 毫秒
101.
The first method for cyano-phosphorylation of aldehydes with diethyl cyanophosphonate in the presence of N-heterocyclic carbene prepared from 1,3-bis(2,4,6-trimethylphenyl)imidazolium chloride and KOt-Bu, as a nucleophilic catalyst, is described. 相似文献
102.
Motomasa Kobayashi Byeng Wha Son Takaji Fujiwara Yoshimasa Kyogoku Isao Kitagawa 《Tetrahedron letters》1984,25(48):5543-5546
A new diterpene named neodolabelline (5), having a methyl migrated dolabellane-type skeleton, was isolated from the stoloniferan soft coral Clavularia koellikeri, together with clavukerins (trinor-sesquiterpenes) and bicyclo-germacrene, and the absolute configuration was determined. 相似文献
103.
A bridged triptycene was obtained by intramolecular cycloaddition reaction of 16,19-dimethoxy[2](9,10)anthraceno[2]paracyclophane followed by acid-catalyzed elimination of methanol. Internal strain in this molecule was disclosed by X-ray crystallographic analysis. 相似文献
104.
Motomasa Kobayashi Yutaka Kiyota Satomi Orito Yoshimasa Kyogoku Isao Kitagawa 《Tetrahedron letters》1984,25(34):3731-3734
Five new pregnene-type steroidal glycosides, named pregnedioside -a (), 4′-O-acetyl-pregnedioside-a (), 3′-O-acetyl-pregnedioside-a (), pregnedioside-b (), and 4′-O-acetyl-pregnedioside-b (), were isolated from an Okinawan soft coral of Alcyonium sp. and their structures were elucidated. These are rare examples of steroidal gylcosides from soft coral. 相似文献
105.
Tetsuaki Nishida Yoshimasa Takashima Yusuke Nakayama 《Journal of solid state chemistry》1980,33(2):141-144
Potassium borate glasses denoted by the formula xK2O · (100 ? x)B2O3 · 7Fe2O3 were irradiated with 60Co-γ-rays at room temperature. Mössbauer parameters for the irradiated glasses containing alkali equal to or higher than 20 mole% showed that the s-electron density at the iron nucleus increased without any change of the steric configuration of oxygen atoms around the iron nucleus. The increase of s-electron density was ascribed to electron transfer from the nonbridging oxygen to the iron nucleus. The presence of the nonbridging oxygen was also confirmed by the irradiation effect of the borate glass (x = 30) prepared using the enriched isotope of 57Fe2O3. Mössbauer parameters for the irradiated glass suggest that the newly observed Fe2+ ions are in tetrahedral symmetry. 相似文献
106.
Toshitami Ooi Koji Mimura Yoshimasa Hama Kenichi Shinohara 《Journal of polymer science. Part A, Polymer chemistry》1976,14(4):813-824
Paramagnetic species produced in a series of linear aliphatic oligoesters $ [\bond;{\rm O}\bond;({\rm CH}_{\rm 2} {\rm )}_m\bond;{\rm O}\bond;{\rm CO}\bond;({\rm CH}_{\rm 2} {\rm )}_n\bond;{\rm CO\rlap{--} ]}_P $ by γ-irradiation at 77°K was investigated by an ESR method. A predominant doublet observed immediately after γ-irradiation, which has hyperfine splitting of 20–23 gauss, is attributed to a radical anion III. Slight decay of this radical anion is observed by illuminating the sample with visible light at 77°K. A small amount of the radical anion is converted to double triplet, which is assigned to ? (ES)? CH? CH2? (where ES denotes the ester group), from the result of heat treatment. The conformational angles for the two β-protons in the (6,2) oligoester are determined to be θ1 = θ2 = 30°. 相似文献
107.
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
108.
Nano-matrix structure formed by graft-copolymerization of styrene onto natural rubber 总被引:1,自引:0,他引:1
Nanthaporn Pukkate Yoshimasa Yamamoto Jitladda Sakdapipanich 《European Polymer Journal》2007,43(8):3208-3214
Nano-matrix structure was formed by graft-copolymerization of styrene onto urea-deproteinized natural rubber (U-DPNR) latex. The grafted U-DPNR was characterized by FT-IR spectroscopy, 1H NMR spectroscopy and transmission electron microscopy. Conversion and grafting efficiency of styrene were more than 90% under the best condition of the graft-copolymerization. In transmission electron micrograph of film specimen stained by OsO4, it was found that natural rubber particle of about 0.5 μm in diameter was dispersed in polystyrene matrix of about 15 nm in thickness. The conversion and grafting efficiency for the grafted U-DPNR were compared with those for a control sample prepared from enzymatic deproteinized natural rubber (E-DPNR) with styrene. 相似文献
109.
Mikio Hoshino Hiroshi Seki Minoru Yamaji Yoshimasa Hama 《Photochemistry and photobiology》1993,57(4):728-731
Abstract— Photochemistry of superoxide adducts of cobalt(II) and zinc(II) porphyrins has been studied by laser photolysis. It was found that the former in dimethlformamide photodissociates the superoxide anion radical, O2 - , with the quantum yield of 0.5 ± 0.05 at the excitation wavelenths 355 and 532 nm, and the latter gives flurescence and the triple state without giving rise to the photodissociation of O2 - 相似文献
110.
Fukuji Higashi Yoshimasa Nakano Mitsuyoshi Goto Hideo Kakinoki 《Journal of polymer science. Part A, Polymer chemistry》1980,18(3):1099-1104
Polyterephthalamides of high molecular weight (ηinh up to 1.9) were obtained by the direct polycondensation reaction of terephthalic acid and aromatic diamines in the presence of poly(ethylene oxide) (PEO) with triphenyl phosphite in a N-methylpyrrolidone (NMP)–pyridine solution that contained lithium chloride. The molecular weights of the polymers produced varied with the amount and molecular weight of PEO, which showed maximum values when PEO with a molecular weight of 2.0 × 104?5.0 × 105 was used in a concentration of about 0.5 wt % in the solvent. The polycondensation reaction was significantly affected by the level of pyridine in a mixed solvent of NMP and pyridine and by the concentration of the lithium chloride added. 相似文献