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排序方式: 共有674条查询结果,搜索用时 15 毫秒
101.
Hirofumi Yamamoto Yuichi Takagi Naoto Yamasaki Tadashi Mitsuyama Yusuke Kasai Hiroshi Imagawa Yutaro Kinoshita Naohiro Oka Masanori Hiraoka 《Tetrahedron》2018,74(50):7173-7178
Thallusin is the only known natural product that induces cell differentiation followed by formation of a thallus during the growth of green macroalgae such as Monostroma and Ulva. Herein, various thallusin analogues based on the terpen skeleton were synthesized to study the structure?activity relationships of thallusin. The potency of the synthetic analogues was investigated in an experimental assay, which demonstrated that the 19-methyl group in thallusin is essential for potent morphogenesis-inducing activity. 相似文献
102.
103.
Murakami T Kawasaki T Takemura A Fukutsu N Kishi N Kusu F 《Journal of chromatography. A》2008,1208(1-2):164-174
Rapid and unambiguous identification of three degradation products (DP-1, DP-2 and DP-3) found in heat-stressed loxoprofen sodium adhesive tapes (Loxonin tapes) was achieved by LC-MS and dynamic pressurized liquid extraction (PLE)-solid-phase extraction (SPE) coupled to LC-NMR without complicated isolation or purification processes. The molecular formulae of the degradation products were determined by accurate mass measurements and product ion analyses and on-line hydrogen/deuterium (H/D) exchange experiments provided information about changes in the degradation of loxoprofen. To compensate for the low sensitivity of NMR, on-line dynamic PLE-SPE was employed and higher concentrations of degradation products trapped on the SPE column were afforded in a shorter time than they would be in such time-consuming sample preparations as pre-concentration after extraction. The loop-storage procedure was used in the LC-NMR analysis to allow the acquisition of the (1)H spectra of the three degradation products in one chromatographic run without affecting the peak separation and to avoid the carry-over of previously eluted DP-1 of high concentration by washing the NMR detection cell prior to the measurement of the DP-2 spectrum. Based on the resulting (1)H NMR spectra in combination with the MS results, DP-1 was successfully identified as an oxidation product having an oxodicarboxylic acid structure formed by the cleavage of the cyclopentanone ring of loxoprofen, DP-2 as a cyclopentanone ring-hydroxylated loxoprofen and DP-3 as a loxoprofen l-menthol ester. 相似文献
104.
Population study of sizes and components of self-reproducing giant multilamellar vesicles 总被引:1,自引:0,他引:1
Toyota T Takakura K Kageyama Y Kurihara K Maru N Ohnuma K Kaneko K Sugawara T 《Langmuir : the ACS journal of surfaces and colloids》2008,24(7):3037-3044
Population analysis of a system of self-reproducing giant multilamellar vesicles (GMVs) was carried out by means of flow cytometry. The multidimensional distribution of forward light scattering (FS), side light scattering (SS), and fluorescence (FL) intensities originating from each GMV provided information about changes in a population composed of 104 vesicles. FS-FL dot plots indicated that, after the addition of the membrane precursor, the size distribution of the newly generated vesicles was nearly the same as that of the original, but the catalyst content was reduced. This result can be interpreted as evidence for the occurrence of the self-reproduction of GMVs. Moreover, the new GMVs recovered the amount of catalyst to the initial value, keeping their size distribution constant, when a solution of the catalyst was added to the new GMVs. These results are the first experimental evidence for a novel phenomenon on GMV size distribution during their self-reproducing cycle. 相似文献
105.
Naoto Ueda Takahiro Gunji Yoshimoto Abe 《Journal of Sol-Gel Science and Technology》2008,48(1-2):163-167
Linear ethoxysiloxanes were synthesized by the oxidative condensation of hydrosilane. Triethoxysilane was subjected to oxidation to form triethoxysilanol, and pentaethoxydisiloxane was formed by the condensation reaction of triethoxysilane with triethoxysilanol. Pentaethoxydisiloxane was also subjected to oxidative condensation to form a mixture of nona- and decaethoxytetrasiloxanes. In contrast, pentaethoxydisiloxane, heptaethoxytrisiloxane, and nonaethoxytetrasiloxanes were subjected to the reaction with ethanol in the presence of zinc to isolate hexaethoxydisiloxane, octaethoxytrisiloxane, and decaethoxytetrasiloxane, respectively. 相似文献
106.
A rhodium-catalyzed silylation reaction of carbon-cyano bonds using disilane has been developed. Under these catalytic conditions, carbon-cyano bonds in aryl, alkenyl, allyl, and benzyl cyanides bearing a variety of functional groups can be silylated. The observation of an enamine side product in the silylation of benzyl cyanides and related stoichiometric studies indicate that the carbon-cyano bond cleavage proceeds through the deinsertion of silyl isocyanide from eta(2)-iminoacyl complex B. Knowledge gained from these studies has led to the development of a new intramolecular biaryl coupling reaction in which aryl cyanides and aryl chlorides are cross-coupled. 相似文献
107.
Zhang H Mitsumori S Utsumi N Imai M Garcia-Delgado N Mifsud M Albertshofer K Cheong PH Houk KN Tanaka F Barbas CF 《Journal of the American Chemical Society》2008,130(3):875-886
The development of enantioselective anti-selective Mannich-type reactions of aldehydes and ketones with imines catalyzed by 3-pyrrolidinecarboxylic acid and related pyrrolidine derivatives is reported in detail. Both (3R,5R)-5-methyl-3-pyrrolidinecarboxylic acid and (R)-3-pyrrolidinecarboxylic acid efficiently catalyzed the reactions of aldehydes with alpha-imino esters under mild conditions and afforded anti-Mannich products with high diastereo- and enantioselectivities (anti/syn up to 99:1, up to >99% ee). For the reactions of ketones with alpha-imino esters, (R)-3-pyrrolidinecarboxylic acid was an efficient catalyst (anti/syn up to >99:1, up to 99% ee). Evaluation of a series of pyrrolidine-based catalysts indicated that the acid group at the beta-position of the pyrrolidine ring of the catalyst played an important role in forwarding the carbon-carbon bond formation and in directing anti-selectivity and enantioselectivity. 相似文献
108.
Umezawa N 《The Journal of chemical physics》2008,128(4):044105
A simple approximation to the functional derivative of Perdew-Zunger-type self-interaction-corrected local-spin density functional is suggested. In this approach, the orbital density |phi(isigma)(r)|(2) is regarded as a functional of the local electron density |phi(isigma)(r)|(2)=n(isigma)(n(sigma)(r)) so as to enable a functional derivative of n(isigma)(n(sigma)(r)) with respect to n(sigma)(r). Our computational results show that this approximation gives fairly good estimates of the total energy, the ionization potential, and the electron affinity for atoms. Comparative studies of this method with the averaged-density approximation and the global averaging method for the self-interaction correction are made. 相似文献
109.
One outstanding feature of the polymer-stabilised blue phase (PSBP) is that it is unnecessary to form an alignment film, which requires a high-temperature baking process. Therefore, PSBPs may enable flexible liquid crystal displays (LCDs) on plastic substrates. In this study, polymer stabilisation of a blue phase (BP) on a single substrate was performed without using a conventional sandwich-type cell, and the electro-optical properties are demonstrated to be similar to those of a sandwich-type PSBP LCD cell. It was experimentally shown that the oxygen which inhibits radical polymerisation is required to be excluded in order to complete the polymer stabilisation in blue phase. 相似文献
110.