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41.
Sbin-Ichi Nagai Taisei Ueda Akito Nagatsu Keiko Nakaoka Nobutoshi Murakami Jinsaku Sakakibara Michiko Fujita Yoshihiro Hotta 《Journal of heterocyclic chemistry》1998,35(2):329-332
5,8-Methanoquinazolines fused with imidazoles 4a-4b , thiadiazoles 5–6 , pyrimidines 7, 9, 11 and 12 , and 1,3,5-triazine 13 were prepared starting from (5R,8S)-2-amino-8,9,9-trimethyl-5,6,7,8-tetrahydro-5,8-methanoquinazoline 3 . Most compounds possessed central nervous system stimulant activities. 相似文献
42.
Monodisperse, cationic polymer particles bearing quaternary ammonium groups effectively self-organized on hydrophobic solid substrates such as alkylated glass plates and polymer films to form particle monolayers. With an increase of the particle surface charge density, the surface coverage decreased and the morphology of particle monolayers changed from aggregated type to dispersed type. The dispersed type of particle monolayers having a relatively regular particle distance was formed at higher temperature. The self-organization behaviors on alkylated glass plates were different from those on unmodified glass plates through electrostatic interaction. The formation of particle monolayers on alkylated glass plates occurred only over a certain latex concentration range in contrast with that on unmodified glass plate. The adhesive strength of particle monolayers was enhanced by annealing at temperatures above the glass transition temperature (T
g) of the particles. Lens-shaped particle monolayers were fabricated by annealing the dispersed type of particle monolayers. 相似文献
43.
Noncatalytic reaction pathways and rates of dimethyl ether (DME) in supercritical water are determined in a tube reactor made of quartz according to liquid- and gas-phase 1H and 13C NMR observations. The reaction is studied at two concentrations (0.1 and 0.5 M) in supercritical water at 400 degrees C and over a water-density range of 0.1-0.6 g/cm3. The supercritical water reaction is compared with the neat one (in the absence of solvent) at 0.1 M and 400 degrees C. DME is found to decompose through (i) the proton-transferred fragmentation to methane and formaldehyde and (ii) the hydrolysis to methanol. Formaldehyde from reaction (i) is consecutively subjected to four types of redox reactions. Two of them proceed even without solvent: (iii) the unimolecular proton-transferred decarbonylation forming hydrogen and carbon monoxide and (iv) the bimolecular self-disproportionation generating methanol and carbon monoxide. When the solvent water is present, two additional paths are open: (v) the bimolecular self-disproportionation of formaldehyde with reactant water, producing methanol and formic acid, and (vi) the bimolecular cross-disproportionation between formaldehyde and formic acid, yielding methanol and carbonic acid. Methanol is produced through the three types of disproportionations (iv)-(vi) as well as the hydrolysis (ii). The presence of solvent water decelerates the proton-transferred fragmentation of DME; the rate constant is reduced by 40% at 0.5 g/cm3. This is caused by the suppression of low-frequency concerted motion corresponding to the reaction coordinate for the simultaneous C-O bond scission and proton transfer from one methyl carbon to the other. In contrast to the proton-transferred fragmentation, the hydrolysis of DME is markedly accelerated by increasing the water density. The latter becomes more important than the former in supercritical water at densities greater than 0.5 g/cm3. 相似文献
44.
Hamao Watanabe Jun Inose Tsutomu Muraoka Masayuki Saito Yoichiro Nagai 《Journal of organometallic chemistry》1983,244(4):329-341
The reaction of 1,2-dimethoxytetramethyldisilane with styrene and α-methylstyrene in the presence of NaOMe catalyst in tetrahydrofuran (THF) gave the new silacyclopentanes 1,1-dimethyl-2,4-diphenyl-1-silacyclopentane (IIIa) and 1,1,2,4-tetramethyl-2,4-diphenyl-1-silacyclopentane (IIIb), respectively. These silacyclopentanes were found to exist as cis-trans mixtures. The use of sodium metal in place of NaOMe afforded similar results. Reactions of a polysilane mixture, MeO-(SiMe2)nOMe (n ≧ 3), with the styrenes also gave similar results. In some cases, polysilacycloalkanes such as 1,2,3-trisilacyclopentanes (IV) and 1,2,3,4-tetrasilacyclohexanes (V) were obtained as by-products. A mechanism for the formation of the silacyclopentanes and polysilacycloalkanes is presented. It was found that electron impact decomposition of silacyclopentanes IIIa and IIIb, trisilacycloalkane IV and tetrasilacycloalkane V gave molecular ions corresponding to the silacyclopropane, cyclotrisilane and cyclotetrasilane systems. 相似文献
45.
Tatsuya Oshima Kaoru Oishi Keisuke Ohto Katsutoshi Inoue 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(1-2):79-85
Extraction behaviors of catecholamines with a series of calixarene carboxylic acid derivatives were investigated. Relatively large calix[6]arene and calix[8]arene extract catecholamines into the organic solution, while smaller calix[4]arene and the monomer analog do not. The calix[6]arene, which has a cavity that fits a protonated amino group well, selectively extracts a primary amino compound dopamine over other catecholamines. Slope analysis and Job’s method confirmed formation of a 1:1 complex between the calix[6]arene and dopamine. On the other hand, the calix[8]arene extracts both dopamine and adrenaline, due to the large cavity for induced-fit recognition. Dopamine extracted with the calixarene is quantitatively stripped by contacting the organic solution with a fresh acidic solution. 相似文献
46.
N Otsuka M Fukunaga K Morita S Ono K Nagai T Furukawa S Yanagimoto T Tomomitsu H Kawahara H Tanaka 《Radioisotopes》1988,37(6):330-335
In order to detect the varicocele, scrotal scintigraphies by using 99mTc-HSA-D were performed in 14 patients with male infertile or palpable mass in left scrotum on physical examinations. Abnormal pooling of 99mTc-HSA-D, indicative of varicocele lesion, could be found in left scrotum in 9 cases, confirmed surgically or clinically. Compared with 99mTc-HSA, 99mTc-HSA-D was superior in high uptake ratio of varicocele to soft tissue and in nonvisualization of bladder. Thus, 99mTc-HSA-D scrotal scintigraphy seemed to be of a great use to detect the varicocele. 相似文献
47.
T. Nagai K. Sakai T. Asaka A. Yamazaki Y. Matsui 《Journal of solid state chemistry》2006,179(6):1898-1903
The crystal structure of our newly discovered Sr-Co-O phase is investigated in detail through high-resolution electron microscopy (HREM) techniques. Electron diffraction (ED) measurement together with energy dispersive X-ray spectroscopy (EDS) analysis show that an ampoule-synthesized sample contains an unknown Sr-Co-O ternary phase with monoclinic symmetry and the cation ratio of Sr/Co=1. From HREM images a layered structure with a regular stacking of a CdI2-type CoO2 sheet and a rock-salt-type Sr2O2 double-layered block is observed, which confirms that the phase is the parent of the more complex “misfit-layered (ML)” cobalt oxides of [MmA2Om+2]qCoO2 with the formula of [Sr2O2]qCoO2, i.e. m=0. It is revealed that the misfit parameter q is 0.5, i.e. the two sublattices of the CoO2 sheet and the Sr2O2 block coexist to form a commensurate composite structure. We propose a structural model with monoclinic P21/m symmetry, which is supported by simulations of ED patterns and HREM images based on dynamical diffraction theory. 相似文献
48.
Yuka Wakata Mika Tokumoto Ryo Horiguchi Katsutoshi Ishikawa Yoshitaka Nagahama Toshinobu Tokumoto 《BMC biochemistry》2004,5(1):18
Background
The 26S proteasome is the proteolytic machinery of the ubiquitin-dependent proteolytic system responsible for most of the regulated intracellular protein degradation in eukaryotic cells. Previously, we demonstrated meiotic cell cycle dependent phosphorylation of α4 subunit of the 26S proteasome. In this study, we analyzed the changes in the spotting pattern separated by 2-D gel electrophoresis of α subunits during Xenopus oocyte maturation. 相似文献49.
Living cationic ring-opening polymerization under air and water was achieved using a well-defined water-resistant cationic initiator in dichloromethane without purification at ambient temperature. 相似文献
50.
Fukui K Naito Y Akiyama Y Takahashi K 《European journal of mass spectrometry (Chichester, England)》2004,10(5):639-647
In this study, the fragmentation of gas-phase protonated Angiotensin II is investigated using electrospray ionization (ESI), Fourier-transform ion cyclotron resonance (FT-ICR), and mass spectrometry (MS) with a laser cleavage infrared multiphoton dissociation (IRMPD) technique. The experimental results show that the spectra peaks for the photoproducts are y2/b6- and y7-type ions, corresponding to the cleavage of His-Pro and Asp-Arg in the parent amino acid sequence. The fragmentation of the peptide under collision-free vacuum conditions is modeled using molecular dynamics simulations (MD). The binding energy for the peptide bonds (C'-N bond) of Angiotensin II is estimated from ab initio calculations. The calculations are directed at predicting experimental measurements of the product ions from the photodissociation of the peptide. The product distributions simulated by the MD dissociation trajectories include predominantly y7/b1 and y2/b6 pair ions. 相似文献