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排序方式: 共有610条查询结果,搜索用时 171 毫秒
561.
Yoshinori Yamanoi Tsukasa Usuki Kenichiro Omoto Masaki Shimada Hikaru Koike Munetaka Iwamura Koichi Nozaki Daisuke Saito Masako Kato Hiroshi Nishihara 《Tetrahedron letters》2019,60(16):1108-1112
Planar chiral dioxacyclophanes were designed and synthesized as a key scaffold for materials with circularly polarized luminescence (CPL). Representative planar chiral 1,12-dioxa[12](1,4)naphthaleneophane-derived organosilane compounds (?)-(R)-1, (+)-(R)-2, and (?)-(R)-3 were prepared by (+)-sparteine-mediated aryl metalation and an electrophilic reaction with chlorosilanes. The absolute configurations of the planar chirality were determined in the R form by single-crystal X-ray analysis. Optically active compound (+)-(R)-2 exhibited blue fluorescence and a CPL signal with a dissymmetry factor (glum value) of 0.001 in solution. The electronic structure was corroborated by DFT and TD-DFT calculations rationalizing the observed spectroscopic properties. 相似文献
562.
Noriyuki Suzuki Taiga Takabe Yoshiko Yamauchi Shun Koyama Rina Koike Masahiro Rikukawa Wei-Ting Liao Wen-Sheng Peng Fu-Yu Tsai 《Tetrahedron》2019,75(10):1351-1358
Palladium-catalyzed Mizoroki-Heck reactions were carried out in water using thermoresponsive polymer micelles. The micelles were generated from thermoresponsive block copolymers consisting of a poly(N-isopropylacrylamide) (PNIPAAm) segment and a hydrophilic segment such as nonionic poly(ethylene glycol) (PEG) (2) and anionic poly(sodium p-styrenesulfonate) (PSSNa) (9). These copolymers exhibited lower critical solution temperature (LCST) behavior at ca. 40–50?°C and showed thermal stimuli-induced formation and dissociation of micelles. The copolymers formed micelles in aqueous solution at higher temperature, where catalytic reactions proceeded. At lower temperature, the micelles dissociated to form a clear solution, enabling efficient extraction of the products from aqueous reaction mixture. In the presence of these copolymers, palladium complexes catalyzed the coupling reactions between aryl iodides and alkene compounds inside the hydrophobic micelle cores in water under relatively milder conditions. Extraction of the products from the aqueous solution of 2 or 9 was found to be efficient enough in comparison with conventional surfactants. 相似文献
563.
Six new acylated triterpenoid saponins, bellisosides A-F (1-6), were isolated from the roots of Bellis perennis (Compositae) together with a known saponin, bellissaponin BS2 (7). These saponins which bear polygalacic acid as sapogenin, are bisdesmosidic glycosides. The structures were elucidated on the basis of chemical and physicochemical evidence. The cytotoxic activities of 1-7 against HL-60 human promyelocytic leukemia cells are also reported. 相似文献
564.
565.
Naoyuki Koike 《Results in Mathematics》2002,42(1-2):81-106
For an equiaffine immersion of general codimension, we recently defined the Lipschitz-Killing curvature, where we fix a transversal bundle and a transversal volume element. The main purpose of this paper is to show that the integration of the absolute value of the Lipschitz-Killing curvature is independent of the choices of a transversal bundle and a transversal volume element. 相似文献
566.
Nonstoichiometry in the perovskite-type compound, HoBa2Cu3O6+x, was determined as a function of oxygen partial pressure (5 × 10−1 1 × 105 Pa) in the temperature range of 8631173 K by coulometric titration using a stabilized zirconia electrolyte. Electromotive force of the cell, EMF, was measured as a function of oxygen content at constant temperature, and as a function of temperature at constant oxygen content. The perovskite-type compound was found to have a tendency to decompose into Ho2O3, BaO, CuO and some double-oxides at low oxygen partial pressures. Defect equilibria are discussed on the basis of the dependence of nonstoichiometry on oxygen partial pressure. Variation of the relative partial molar entropy with composition is explained in terms of a well-known defect model. A new technique which was developed for measuring the electrical conductivity of a non-stoichiometric oxide, in situ, at constant oxygen content as a function of temperature in the coulometric titration cell, is presented. 相似文献
567.
Sohma Y Sasaki M Hayashi Y Kimura T Kiso Y 《Chemical communications (Cambridge, England)》2004,(1):124-125
A novel and efficient method for the synthesis of difficult sequence-containing peptides has been developed based on the synthesis of O-acyl isopeptides followed by an O-N intramolecular acyl migration reaction, resulting in a remarkable improvement of the yields. 相似文献
568.
Two new galloylglucosides from the leaves of Mallotus furetianus 总被引:1,自引:0,他引:1
Wei K Li W Koike K Liu L Fu X Lin L Chen Y Nikaido T 《Chemical & pharmaceutical bulletin》2004,52(6):776-779
Two new galloylglucosides, mallophenols A (1) and B (2), were isolated from the leaves of Mallotus furetianus (Euphorbiaceae), together with seven known compounds, (6S,9R)-roseoside (3), aviculin (4), (+)-lyoniresinol-3alpha-O-alpha-L-rhamnopyranoside (5), (Z)-3-hexenyl-beta-D-glucopyranoside (6), 3,3,8,9,10-pentahydroxydibenzo[b,d]pyran-6-one (7), 3-hydroxy-4,5(R)-dimethyl-2(5H)-furanone (8) and gallic acid (9). The stereostructures of 1 and 2 were elucidated on the basis of spectroscopic analysis and chemical evidence. 相似文献
569.
Akihisa T Tokuda H Ukiya M Suzuki T Enjo F Koike K Nikaido T Nishino H 《Chemical & pharmaceutical bulletin》2004,52(1):153-156
The structure of a triterpenoid isolated from the nonsaponifiable lipid (NSL) of the seed oil of the camellia (Camellia japonica L.; Theaceae) was established to be (20S)-3beta-hydroxy-25,26,27-trisnordammaran-24,20-olide (1; 3-epicabraleahydroxylactone) on the basis of spectroscopic and chemical methods. Six other triterpenoids isolated from the NSL were identified as 3-epicabraleadiol (2), ocotillol II (3), ocotillol I (4), dammarenediol II (5), (20R)-taraxastane-3beta,20-diol (6), and lupane-3beta,20-diol (7). Upon evaluation of the seven triterpenoids (1-7) with respect to their inhibitory effects on the induction of Epstein-Barr virus early antigen (EBV-EA) by 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells, three compounds (5-7) showed potent inhibitory effects against EBV-EA induction (IC(50) values of 277-420 mol ratio/32 pmol TPA). 相似文献
570.
Beer G Bragadireanu AM Cargnelli M Curceanu-Petrascu C Egger JP Fuhrmann H Guaraldo C Iliescu M Ishiwatari T Itahashi K Iwasaki M Kienle P Koike T Lauss B Lucherini V Ludhova L Marton J Mulhauser F Ponta T Schaller LA Seki R Sirghi DL Sirghi F Zmeskal J;DEAR Collaboration 《Physical review letters》2005,94(21):212302
The DEAR (DAPhiNE exotic atom research) experiment measured the energy of x rays emitted in the transitions to the ground state of kaonic hydrogen. The measured values for the shift epsilon and the width Gamma of the 1s state due to the K(-)p strong interaction are epsilon(1s)=-193 +/- 37 (stat) +/- 6 (syst) eV and Gamma(1s)=249 +/- 111 (stat) +/- 30 (syst) eV, the most precise values yet obtained. The pattern of the kaonic hydrogen K-series lines, K(alpha), K(beta), and K(gamma), was disentangled for the first time. 相似文献