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181.
Choji Kashima Yohei Miwa Saori Shibata Hiroyuki Nakazono 《Journal of heterocyclic chemistry》2003,40(4):681-688
N‐Acylpyrazoles ( 1 ) were promising as good dienophiles, which were easily converted into the desired carboxylic derivatives. Bis(pyrazolyl)methanes, which were derived from chiral pyrazoles, showed the activity of chiral catalyst. Particularly 10 mol% of bis(isomenthopyrazol‐1,1′‐yl)methane ( 8a ) catalyzed enantioselectively the Diels Alder reaction up to 40 % ee by the formation of complex with Mg(ClO4)2. 相似文献
182.
A molecular probe with l-phenylalanine p-nitroanilide and l-lysin 4-methylcoumaryl-7-amide, in which these amino acid derivatives are connected through a succinic-acid spacer, was prepared. Trypsin and papain were detected by blue-fluorescence emission of generated 7-amino-4-methylcoumarin (AMC). α-Chymotrypsin and nattokinase were detected from both the blue-fluorescence emission of AMC and the UV absorbance of p-nitroaniline. In addition, different time courses of p-nitroaniline and AMC were observed between the reaction of P1 with α-chymotrypsin and that with nattokinase. In the case of nattokinase, both the fluorescence emission and UV absorbance slowly increased. In contrast, the increasing UV absorbance was saturated at the early stage of the reaction of the present probe with chymotrypsin, whereas the fluorescence emission continuously increased in the following stages. 相似文献
183.
Kishikawa K Nakahara S Nishikawa Y Kohmoto S Yamamoto M 《Journal of the American Chemical Society》2005,127(8):2565-2571
Novel columnar liquid crystalline compounds N,N'-bis(3,4,5-trialkoxylphenyl)ureas 1a-c (R = n-C(8)H(17), n-C(12)H(25), and n-C(16)H(33)) were synthesized, and their phase transitions were measured by differential scanning calorimetery. The superstructures were investigated by X-ray diffraction, polarized light optical microscopy, and IR spectroscopy. The compounds exhibited both rectangular and hexagonal columnar phases in which the urea molecules in each column were stacked in one direction with strong hydrogen bonds. To confirm the ferroelectric switching, optoelectronic experiments were carried out, and the hexagonal columnar phases of 1b and 1c gave a sharp peak of spontaneous polarization in response to an applied triangular wave electric field (0.1-18 Hz). This is the first example of ferroelectrically switchable columnar liquid crystal phases generated by achiral molecules. 相似文献
184.
Choji Kashima Yohei Miwa Saori Shibata Hiroyuki Nakazono 《Journal of heterocyclic chemistry》2002,39(6):1235-1240
New chiral pyrazoles, (4R,7R)‐4‐methyl‐7‐isopropyl‐3‐phenyl‐ (3‐phenyliso menthopyrazole cis‐1), (4R,7S)‐4‐methyl‐7‐isopropyl‐ (1‐menthopyrazole; trans‐2), (4R,7R)‐4‐isopropyl‐7‐methyl‐ (iso carvomen‐thopyrazole, cis‐3) and (4R,7S)‐4‐isopropyl‐7‐methyl‐4,5,6,7‐tetrahydro‐1H‐indazole (carvomenthopyra‐zole, trans‐3) were prepared. The diastereomeric pairs of these 1–3 were structurally characterized by NMR spectroscopy. The subtle differences of structures of 1–3 should induce the useful effects for a chiral auxiliary or a chiral catalyst. 相似文献
185.
We propose a simple method for the measurement of the absorption ellipsoid of luminescent nanoparticles. The method is based on a combination of far-field and near-field polarized excitation in a wide-field fluorescence microscope and provides the orientation and axes ratio r of a rotationally symmetric ellipsoid. Potential applications of the method including the study of conjugated polymer conformations are discussed. 相似文献
186.
Biotransformation of (+)-(1R,2S)-fenchol by the larvae of Spodoptera litura was carried out. Substrate was converted to three new terpenoids, (+)-(1R,2S)-10-hydroxyfenchol, (+)-(1R,2R,3S)-8-hydroxyfenchol and (−)-(1S,2S,6S)-6-exo-hydroxyfenchol, and one known terpenoid, (−)-(1R,2R,3R)-9-hydroxyfenchol. These structures were established by NMR, IR, specific rotation and mass spectral studies. 相似文献
187.
Masami Terauchi Yohei Sato Atsushi Oguri Kaoru Kimura 《Journal of solid state chemistry》2004,177(8):2916-2919
Electronic structures of Cu and Mg-Si-doped β-rhombohedral boron (β-r-B) crystals were studied by using a high-energy-resolution electron energy-loss spectroscopy microscope. Boron 1s electron excitation spectra, which show the density of states of the conduction bands, of the crystals were obtained from single crystalline areas of 100 nm in diameter. The spectrum of Cu-doped β-r-B showed a chemical shift to a lower binding energy side. It means an electron transfers from the doped Cu atoms to B atoms. The intensity distributions of the spectrum was almost the same as that of the non-doped β-r-B, which suggests that all of the doped electrons occupy the intrinsic acceptor level just above the valence bands. The spectrum of Mg-Si-doped β-r-B showed not only a chemical shift to a lower binding energy side but also a sharp intensity increase at the onset with a width of an energy resolution of the experiment. The sharp onset may be assigned to a Fermi edge. It indicates that the doped electrons fill up the acceptor level and occupy the conduction bands forming the Fermi edge, a metallization of β-r-B by the Mg-Si-doping. 相似文献
188.
Ayako Fujimoto Noriko Fujinaga Ryo Nishimura Eri Hatano Luna Kono Akira Nagai Akiko Sekine Yohei Hattori Yuko Kojima Nobuhiro Yasuda Masakazu Morimoto Satoshi Yokojima Shinichiro Nakamura Ben L. Feringa Kingo Uchida 《Chemical science》2020,11(45):12307
We report a swinging motion of photochromic thin broad sword shaped crystals upon continuous irradiation with UV light. By contrast in thick crystals, photosalient phenomena were observed. The bending and swinging mechanisms are in fact due to molecular size changes as well as phase transitions. The first slight bending away from the light source is due to photocyclization-induced surface expansion, and the second dramatic bending toward UV incidence is due to single-crystal-to-single-crystal (SCSC) phase transition from the original phase I to phase IIUV. Upon visible light irradiation, the crystal returned to phase I. A similar SCSC phase transition with a similar volume decrease occurred by lowering the temperature (phase IIItemp). For both photoinduced and thermal SCSC phase transitions, the symmetry of the unit cell is lowered; in phase IIUV the twisting angle of disordered phenyl groups is different between two adjacent molecules, while in phase IIItemp, the population of the phenyl rotamer is different between adjacent molecules. In the case of phase IIUV, we found thickness dependent photosalient phenomena. The thin broad sword shaped crystals with a 3 μm thickness showed no photosalient phenomena, whereas photoinduced SCSC phase transition occurred. In contrast, large crystals of several tens of μm thickness showed photosalient phenomena on the irradiated surface where SCSC phase transition occurred. The results indicated that the accumulated strain, between isomerized and non-isomerized layers, gave rise to the photosalient phenomenon.We report a swinging motion of photochromic thin broad sword shaped crystals upon continuous irradiation with UV light. 相似文献
189.
Jun Ishihara Yohei IkumaSusumi Hatakeyama Takanori SuzukiAkio Murai 《Tetrahedron》2003,59(51):10287-10294
Azadirachtin is a C-seco limonoid, derived from the neem tree. Previously, we reported the synthesis of the right and left segments of azadirachtin, in addition to the coupling reaction of the modeled ester utilizing Claisen rearrangement. Herein we report the transformation of the modeled rearrangement product into a tricyclic dihydrofuran, which would be expected to have bioactivity against insects. 相似文献
190.
Yohei Tsutsui 《Mathematische Nachrichten》2016,289(2-3):360-376
In R 3, a div‐curl lemma with critical exponents in terms of Hardy spaces associated to Herz spaces is given. 相似文献