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131.
A cobalt-diamine complex catalyzes the cross-coupling reactions of primary and secondary alkyl halides with aryl Grignard reagents. It is confirmed that oxidative addition of alkyl halide to cobalt proceeds via a radical process. Optically pure Ueno-Stork halo acetals undergo diastereoselective cross-coupling reactions, the products of which are transformed into optically active THF derivatives. A sequential radical cyclization/arylation reaction under cobalt catalysis provides extremely short access to a synthetic prostaglandin AH13205. 相似文献
132.
Tatsuya Yoshimura Hirohisa Nagatani Toshiyuki Osakai 《Analytical and bioanalytical chemistry》2014,406(14):3407-3414
The fluorescence behavior of anionic membrane-potential-sensitive dyes, bis-(1,3-dibutylbarbituric acid) trimethine oxonol (DiBAC4(3)) and bis-(1,3-diethylthiobarbituric acid)trimethine oxonol (DiSBAC2(3)), at a biomimetic 1,2-dichloroethane (DCE)/water (W) interface was studied by the mean of potential-modulated fluorescence (PMF) spectroscopy. The respective dyes gave a well-defined PMF signal due to the adsorption/desorption at the DCE/W interface. It was also found that the potentials where the two dyes gave the PMF signals were different by about 100 mV. We then attempted a combined use of the two dyes for determination of the Galvani potential difference across the DCE/W interface. When 40 μM DiBAC4(3) and 15 μM DiSBAC2(3) were initially added to the W phase, distinctly different spectra were obtained for different interfacial potentials. The ratio of the PMF signal intensities at 530 and 575 nm (the fluorescence maximum wavelengths for the respective dyes) showed a clear dependence on the interfacial potential. These results suggested the potential utility of the combined use of two dyes for the determination of membrane potentials in vivo. Figure
Combined use of two membrane-potential-sensitive dyes that show different colors of fluorescence emission at their specific adsorption potentials. 相似文献
133.
Takaoki Ishii Ryo Watanabe Toshimitsu Moriya Prof. Dr. Hirohisa Ohmiya Prof. Dr. Seiji Mori Prof. Dr. Masaya Sawamura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(40):13547-13553
Catalyst–substrate hydrogen bonds in artificial catalysts usually occur in aprotic solvents, but not in protic solvents, in contrast to enzymatic catalysis. We report a case in which ligand–substrate hydrogen‐bonding interactions cooperate with a transition‐metal center in alcoholic solvents for enantioselective catalysis. Copper(I) complexes with prolinol‐based hydroxy amino phosphane chiral ligands catalytically promoted the direct alkynylation of aldehydes with terminal alkynes in alcoholic solvents to afford nonracemic secondary propargylic alcohols with high enantioselectivities. Quantum‐mechanical calculations of enantiodiscriminating transition states show the occurrence of a nonclassical sp3‐C? H???O hydrogen bond as a secondary interaction between the ligand and substrate, which results in highly directional catalyst–substrate two‐point hydrogen bonding. 相似文献
134.
Yuki Tanikami Takuma Tagami Mayu Sakamoto Yukihiro Arakawa Hitoshi Mizuguchi Yasushi Imada Toshio Takayanagi 《Electrophoresis》2020,41(15):1316-1325
Acid dissociation constants (pKa) of nine kinds of flavin analogues as molecular catalyst candidates were determined by CZE. Although some of the analogues are instable and degradable under the light exposure or in alkaline aqueous solutions, the effective electrophoretic mobility of the flavin analogue of interest has been measured with the residual substance. The pKa values of the flavin analogues were analyzed through the changes in the effective electrophoretic mobility with varying pH of the separation buffer. One or two steps pKa values were determined by the analysis. One of the degraded species from the flavin analogues, lumichrome, was also detected in the CZE analysis, and its pKa values were also determined. While coexisting impurities generated over the storage conditions were found in some analogues, the pKa values of the target analogues were successfully determined with the help of the CZE separations. A pressure-assisted CZE was utilized for the determination or the estimation of the pKa values of such analogues as possessing carboxylic acid moiety. 相似文献
135.
Nao Kamei-Ishikawa Keiko Tagami Shigeo Uchida 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(3):1763-1768
In this study, we experimentally obtained partitioning ratios of radioiodide (125I?) in the three phases at two different temperatures, 4 and 23 °C, in order to observe the effect of biological activity for upland soil samples. Even at 4 °C, 125I emission was found; its partitioning ratio in the gas phase ranged from 0 to 27 %. As expected, the ratio at 23 °C was higher than that at 4 °C. Additionally, in comparison of the data for upland soil samples obtained in this study and our previous data for paddy soil samples, for the latter, I? was not only sorbed in the soil but also more of it was released into the air than for upland soil samples. The land-use difference for I? partitioning in soil might be attributed to the differences of exchangeable K and stable I concentrations in soil from the statistical analysis. On the other hand, there were good correlations of partitioning ratios in solid, liquid, and gas phases between the two temperatures. The results implied that the biological activity can enhance partitioning in not only the gas phase, but also the solid phase. Indeed, the soil–soil solution distribution coefficient at 23 °C was about three times as high as that at 4 °C. 相似文献
136.
Removal of radiocesium from food by processing is of great concern following the accident of TEPCO’s Fukushima Daiichi Nuclear Power Plant accident. To provide more Cs removal rates, we studied the applicability of K data using edible plant samples. Values were compared for 137Cs and 40K of the food processing retention factors, F r (total activity in processed food/total activity in raw food), and they were found to be close to the 1:1 line and highly correlated (R = 0.96, p < 0.001). Thus, K can be an analogue to estimate radiocesium removal rates by food processing of vegetables. Using the literature K values, we calculated the K removal rates (%), that is, (1 ? F r) × 100, for ten vegetable types to provide potential Cs removal rates. The average percent of K removal were as follows: dried pulses, 33; fresh pulses, 15; leafy vegetables, 52; fruit vegetables, 7; flower vegetables, 44: root crops, 18; tubers, 16; ferns, 93: mushrooms, 32; and others, 30. 相似文献
137.
Naka Koyata Tsuyoshi Miura Yoko Akaiwa Hisashi Sasaki Rie Sato Takuya Nagai Hirohisa Fujimori Takuya Noguchi Masayuki Kirihara Nobuyuki Imai 《Tetrahedron: Asymmetry》2009,20(17):2065-2071
(R)-(+)-Cibenzoline (95% ee) was synthesized in two steps from (+)-2,2-diphenylcyclopropylmethanol 3a (98% ee), which was oxidized with IBX in DMSO, followed by treatment with ethylenediamine in the presence of I2 and K2CO3 in tBuOH. Compound (R)-(+)-3a (98% ee) was prepared by cyclopropanation of 3,3-diphenyl-2-propen-1-ol 1 with Et2Zn and CH2I2 in the presence of a catalytic amount of (S)-2-(methanesulfonyl)amino-1-(p-toluenesulfonyl)amino-3-phenylpropane 2, followed by esterification with 3,5-dinitorobenzoyl chloride, recrystallization, and hydrolysis. 相似文献
138.
Potential-modulation spectroelectrochemical methods at solid/liquid and liquid/liquid interfaces are reviewed. After a brief summary of the basic features and advantages of the methods, practical applications of potential-modulation spectroscopy are demonstrated using our recent studies of solid/liquid and liquid/liquid interfaces, including reflection measurements for a redox protein on a modified gold electrode and fluorescence measurements for various dyes at a polarized water/1,2-dichloroethane interface. For both interfaces, the use of linearly polarized incident light enabled an estimation of the molecular orientation. The use of a potential-modulated transmission-absorption measurement for an optically transparent electrode with immobilized metal nanoparticles is also described. The ability of potential-modulated fluorescence spectroscopy to clearly elucidate the charge transfer and adsorption mechanisms at liquid/liquid interfaces is highlighted. 相似文献
139.
140.
An optical irradiation method for high-speed fiber coupler fabrications without contamination is proposed. In optical fiber
taper fabrications we found an interesting effect that fiber elongation is self-arrested although laser irradiation is continued.
This is a typical effect in the optical irradiation method, but is not seen in the flame method or the thermal heating method.
The “self-controlled fiber taper shape effect” is theoretically explained by considering thermal energy flows, and optical
fiber couplers are fabricated using this effect. From our experiments, we show that optical fiber coupler fabrications at
high-speed without contamination are possible using the optical irradiation method. 相似文献