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排序方式: 共有311条查询结果,搜索用时 187 毫秒
11.
As the glycosyl constituents of Ficus pumila L. fruits (Moraceae), three new sesquiterpenoid glucosides, pumilasides A, B and C were isolated together with benzyl beta-D-glucopyranoside, (E)-2-methyl-2-butenyl beta-D-glucopyranoside and rutin. Their structures were characterized as (1S,4S,5R,6R,7S,10S)-1,4,6-trihydroxyeudesmane 6-O-beta-D-glucopyranoside, (1S,4S,5S,6R,7R,10S)-1,4-dihydroxymaaliane 1-O-beta-D-glucopyranoside and 10 alpha, 11-dihydroxycadin-4-ene 11-O-beta-D-glucopyranoside by spectral and chemical methods. 相似文献
12.
Mariko Kitajima Minako Anbe Noriyuki Kogure Sumphan Wongseripipatana Hiromitsu Takayama 《Tetrahedron》2014
Seven new indole alkaloids (aspidofractinine type 1–3, kopsine type 5, strychnos type 6, and vincamine type 7, 8) were isolated from Kopsia jasminiflora (Apocynaceae) collected in Thailand. 5-Oxokopsinic acid (4) was isolated from nature for the first time. The structures of the new alkaloids were determined by spectroscopic analyses and chemical transformation of a known alkaloid. 5,6-Secokopsinine (1) possesses a dialdehyde function that is formed by oxidative cleavage of the C-5–C-6 bond of kopsinine (9). New vincamine-type alkaloid 8 showed potent inhibitory activity toward human cancer cell lines (A549, HT29, HCT116). 相似文献
13.
O. V. Misochko R. Lu M. Hase M. Kitajima 《Journal of Experimental and Theoretical Physics》2007,104(2):245-253
The relative contributions of the anharmonicity of the lattice potential and the nonequilibrium concentration of charge carriers to the time dependence of the coherent A 1g phonon frequency in bismuth excited by high-energy ultrashort laser pulses are studied by the coherent control method. The contributions are separated by the pump-probe method in which excitation is performed by two pulses with a controlled time delay. It is shown that, depending on the relative delay between the pump pulses, both correlation and anticorrelation between the amplitude and the initial frequency of oscillations are observed while the chirp and the initial frequency of the coherent phonon are anticorrelated. In addition, it has been found that the contributions of the lattice and the electronic subsystem are always anticorrelated. Therefore, a certain phase can be assigned to an electronic excitation and it may be suggested that the time dependence of the phonon frequency is determined not only by instantaneous values of the lattice and electronic response but also by the phase relations between them. 相似文献
14.
Yuji Kikukawa Kensuke Seto Daiki Watanabe Hiromasa Kitajima Misaki Katayama Shohei Yamashita Yasuhiro Inada Yoshihito Hayashi 《Angewandte Chemie (International ed. in English)》2020,59(34):14399-14403
Dodecavanadate, [V12O32]4? (V12), possesses a 4.4 Å cavity entrance, and the cavity shows unique electrophilicity. Owing to the high polarizability, Br2 was inserted into V12, inducing the inversion of one of the VO5 square pyramids to form [V12O32(Br2)]4? (V12(Br2)). The inserted Br2 molecule was polarized and showed a peak at 185 cm?1 in the IR spectrum. The reaction of V12(Br2) and toluene yielded bromination of toluene at the ring, showing the electrophilicity of the inserted Br2 molecule. Compound V12(Br2) also reacted with propane, n‐butane, and n‐pentane to give brominated alkanes. Bromination with V12(Br2) showed high selectivity for 3‐bromopentane (64 %) among the monobromopentane products and preferred threo isomer among 2‐,3‐dibromobutane and 2,3‐dibromopenane. The unique inorganic cavity traps Br2 leading the polarization of the diatomic molecule. Owing to its new reaction field, the trapped Br2 shows selective functionalization of alkanes. 相似文献
15.
Water-soluble constituents of dill 总被引:1,自引:0,他引:1
From the water-soluble portion of the methanol extract of dill (fruit of Anethum graveolens L.), which has been used as a spice and medicine, thirty-three compounds, including a new monoterpenoid, six new monoterpenoid glycosides, a new aromatic compound glucoside and a new alkyl glucoside were obtained. Their structures were clarified by spectral investigation. 相似文献
16.
Kitajima M Hashimoto K Yokoya M Takayama H Aimi N Sakai SI 《Chemical & pharmaceutical bulletin》2000,48(10):1410-1412
A new gluco indole alkaloid, 3,4-dehydro-5-carboxystrictosidine, was obtained from Peruvian U?a de Gato (Cat's Claw, original plant: Uncaria tomentosa) together with two known gluco indole alkaloids. This compound was the first example of isolation of a gluco monoterpenoid indole alkaloid having a 3,4-dihydro-beta-carboline ring system from nature. A characteristic feature of the compound was the quick replacement of the methylene hydrogens on C-14 with deuterium that was observed when it was dissolved in CD3OD. We demonstrated a similar proton-deuterium exchange on a model compound, 1-methyl-3,4-dihydro-gamma-carboline, in CD3OD solution. 相似文献
17.
Nakayama M Goto S Uchimoto Y Wakihara M Kitajima Y Miyanaga T Watanabe I 《The journal of physical chemistry. B》2005,109(22):11197-11203
Changes in the electronic structure of olivine Li(1-x)CoPO(4), 4.8 V positive electrode material for lithium ion batteries, were investigated using the X-ray absorption spectroscopy (XAS) technique. The threshold energy in the Co K-edge increased with electrochemical Li removal, indicating the oxidation of cobalt ions due to charge compensation. Moreover, P and O K-edge XAS showed a slight shift in threshold energy with Li removal. Although it is generally believed that the electrons of PO(4) polyanion do not contribute to the oxidation process, present experimental results indicate changes in the electronic structure around PO(4) units. Such results would be interpreted by the idea of the hybridization effect between the Co 3d and O 2p orbitals and of the polarization effect introduced by Li ions. 相似文献
18.
We calculate scattering functions S(q-->,omega) of neutron Compton scattering (NCS) for a proton (deuteron) pair in the entangled state caused by the indistinguishability of particles. From the calculation, it is concluded that the effect of entanglement on the scattering intensity is undetectable in NCS experiments because of their high energy transfer and broad energy resolution. 相似文献
19.
Taniguchi J Yamaguchi A Ishimoto H Ikegami H Matsushita T Wada N Gatica SM Cole MW Ancilotto F Inagaki S Fukushima Y 《Physical review letters》2005,94(6):065301
Heat capacity measurements have been made down to 5 mK for 3He fluid films adsorbed in one-dimensional (1D) nanometer-scale pores, 28 A in diameter, preplated with 4He of 1.47 atomic layers. At low 3He density, the heat capacity shows a density-dependent, Schottky-like peak near 150 mK asymptoting to the value corresponding to a 2D Boltzmann gas at high temperatures. The peak behavior is attributed to the crossover from a 2D gas to a 1D state at low temperatures. The degenerate state of the 1D 3He fluid is indicated by a predominantly linear temperature dependence below about 30 mK. 相似文献
20.
Kitajima M Hashimoto K Sandoval M Aimi N Takayama H 《Chemical & pharmaceutical bulletin》2004,52(10):1258-1261
A new oleanan-type triterpene and three new cincholic acid glycosides were isolated from Peruvian "Una de Gato" (Cat's claw, plant of origin: Uncaria tomentosa), a traditional herbal medicine in Peru. Their structures were determined by spectroscopic analysis. 相似文献