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851.
852.
The aromatic segment of rifamycin S () was synthesized from the cyclohexadienone or in high overall yield. 相似文献
853.
Ion heating and high-energy-particle production by ion-cyclotron heating in the large helical device
Mutoh T Kumazawa R Seki T Watari T Saito K Torii Y Hartmann DA Zhao Y Sasao M Isobe M Osakabe M Krasilnikov AV Ozaki T Narihara K Nagayama Y Inagaki S Shimpo F Nomura G Yokota M Akaishi K Ashikawa N de Vries P Emoto M Funaba H Fukuyama A Goto M 《Physical review letters》2000,85(21):4530-4533
Ion-cyclotron heating was applied to the Large Helical Device. When the proton-cyclotron resonance was near the saddle point of the magnetic field-strength plane, strong ion-cyclotron damping occurred. Under these conditions efficient plasma heating was achieved for more than one minute. A high-energy ion tail was observed, and the effective tail temperature was determined by a balance between the wave acceleration and the electron-drag relaxation. There was no apparent sign of particle orbit loss effect in the investigated density range of 0.8-1.3x10(19) m(-3). 相似文献
854.
Hiroto Sagara Masaki Kanakogi Yuki Tara Hitoshi Ouchi Junko Kimura Yukiko Kaneko Makoto Inai Tomohiro Asakawa Tomohisa Ishikawa Toshiyuki Kan 《Tetrahedron letters》2018,59(19):1816-1818
We accomplished a divergent synthesis of sudachitin (2), a polymethoxyflavone isolated from citrus fruits, and six derivatives from acetophenone 9, which was an intermediate in our previous synthesis of nobiletin (1). Compound 2 enhanced glucose-induced insulin secretion in INS-1D cells, but was less potent than 1. Compared with 1, compound 2 and two derivatives were more potent inhibitors of cAMP-specific phosphodiesterase. 相似文献
855.
Tomoko Haraga Hiroto Tsujimura Saori Miyauchi Takuya Kamimura Masami Shibukawa Shingo Saito 《Electrophoresis》2020,41(13-14):1152-1159
A novel combination of CE-based separation techniques was used for the precise fractionation of ionic compounds from impurities. The combination of on-capillary concentration and separation using transient isotachophoresis, with multiple injections and a two-point detection system provided higher efficiency, and accuracy at a microliter-scale injection volume, than when CE was individually used for purification. In this paper, we present successful applications of the CE fractionation techniques for the purification of fluorescein, fluorescein-4-isothiocyanate, two fluorescent metal ion probes, and a fluorescein-modified DNA aptamer. The purity of the isolated fluorescent probes ranged from 95 to 99%. Such high purity could not be achieved using chromatographic purification techniques. With relatively low dilution factors of 6–9, the purified probe solutions were practical for use as purified stock solutions. In addition, the fluorescein-modified DNA aptamer purified by our method was successfully used in a thrombin binding assay. The method developed was useful for the purification of anionic fluorescent reagents to be of ultratrace analytical grade for use with CE-LIF. 相似文献
856.
Thanyada Sukmanee Dr. Kanet Wongravee Dr. Yasutaka Kitahama Prof. Dr. Sanong Ekgasit Dr. Tamitake Itoh Dr. Prompong Pienpinijtham Prof. Dr. Yukihiro Ozaki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(34):14672-14677
Discrimination between enantiomers is achieved by tip-enhanced Raman scattering (TERS) using a silver tip that is chemically modified by an achiral para-mercaptopyridine (pMPY) probe molecule. Differences in the relative intensities of the pMPY spectra were monitored for three pairs of enantiomers containing hydroxy (−OH) and/or amino (−NH2) groups. The N: or N+−H functionality of the pMPY-modified tip participates in hydrogen-bond interactions with a particular molecular orientation of each chiral isomer. The asymmetric arrangement of silver atoms at the apex of the tip induces an asymmetric electric field, which causes the tip to become a chiral center. Differences in the charge-transfer (CT) states of the metal-achiral probe system in conjunction with the asymmetric electric field produce different enhancements in the Raman signals of the two enantiomers. The near-field effect of the asymmetric electric field, which depends on the number of analyte functional groups capable of hydrogen-bond formation, improves the degree of discrimination. 相似文献
857.
C-Hydroxylated carboranes, carboranols, have interesting properties resulting from their hydroxyl protons being highly acidic because of the electron-deficient nature of the carborane cage. We described here an efficient synthesis of C-hydroxycarboranes 2 and C,C'-dihydroxycarboranes 3 by the reaction of carboranyl lithium and trimethylborate, followed by oxidation with hydrogen peroxide in the presence of acetic acid, to afford the corresponding o-, m-, and p-hydroxycarboranes 2 and o-, m-, and p-dihydroxycarboranes 3 selectively in high yields through a one-pot procedure. The m- and p-carborane isomers of 2 and 3 were obtained in especially good yields (2b, 85%; 2c, 85%; 3b, 95%; 3c, 96%). DFT calculations were performed on the dihydroxycarboranes 3 to compare the geometrical features of the isomers at the same level of theory and to characterize their electronic and NMR spectroscopic (13C chemical shift) properties. 相似文献
858.
Kasarin is an antibacterial marine alkaloid that was isolated from the microorganism Hyphomycetes sp. Its structure was previously reported to be an azetinone compound 1. However, detailed spectroscopic analysis of the natural compound and its related synthetic analogs revealed that the structure of kasarin should be revised to be a novel 5-malonyloxy-1-methoxy-pyrazin-2(1H)-one derivative 2. 相似文献
859.
We fabricate reflection color filters for three primary colors using silicon two-dimensional triangular-lattice subwavelength gratings on the same quartz substrate. The grating periods are 480, 390, and 300 nm for red, green, and blue filters, respectively. All of the color filters have the same thickness of 100 nm, which enables the simple fabrication of a color filter array. Maximum reflectances of 75 and 46% are obtained at wavelengths of 647.1 and 522.1 nm for the red and green filters, respectively. The blue filter has a double-peaked spectrum with a reflectance of 30% at the peak wavelengths of 450.0 and 502.7 nm. By rigorous coupled-wave analysis, the dimensions of each color filter are designed, and the calculated theoretical reflectance is compared with the measured one. 相似文献
860.
The high-resolution infrared spectrum of N212C18O2 has been observed in the ν3 band (2314 cm?1) region of 12C18O2 with diode laser absorption spectroscopy of pulsed molecular beam. The geometry of N212C18O2 is similar to N212C16O2, a T-shaped structure with the nitrogen molecular axis pointing towards the carbon atom. The geometrical parameters of the T-shaped ground-state structure are determined as RNcmC = 3.7285(5) Å and (90?ΘNcmCO) = 6.85(3)°. The vibrational band origin of N212C18O2 corresponding to the ν3 mode of 12C18O2 shows a shift of 0.52499(10) cm?1 with respect to that of 12C18O2. 相似文献