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991.
H Saji Y Magata Y Yamada K Tajima Y Yonekura J Konishi Y Ohmomo A Yokoyama 《Chemical & pharmaceutical bulletin》1992,40(3):734-736
A nicotine agonist, 11C-labeled (S)-nicotine, was synthesized by N-methylation of (S)-nornicotine with [11C]-methyl iodide in dimethylformamide-dimethylsulfoxide in order to study nicotinic receptors in the human brain by positron emission tomography. The radiochemical yield of this N-methylation reaction was more than 90% within 5 min. After purification by high performance liquid chromatography the radiochemical purity of the product was more than 99% and the specific radioactivity was 7.4-11.1 GBq/mumol. The regional distribution of (S)-[11C]nicotine in the mouse brain after intravenous injection was compared with that of (R)-[11C]nicotine. After injection of (S)-[11C]nicotine, the regional uptake of radioactivity was in the following order: cortex greater than thalamu approximately hippocampus greater than striatum greater than hypothalamus greater than cerebellum. Moreover, (S)-[11C]nicotine was displaced from the brain by unlabeled (S)-nicotine, but unlabeled (R)-nicotine caused no change in uptake. In contrast, (R)-[11C]nicotine showed a lower brain uptake and lesser regional differences in radioactivity. 相似文献
992.
Ichikawa T Kitazaki T Matsushita Y Hosono H Yamada M Mizuno M Itoh K 《Chemical & pharmaceutical bulletin》2000,48(12):1947-1953
New routes for the synthesis of the optically active antifungal triazoles 1-[(1R,2R)-2-(2,4-difluorophenyl)-2-hydroxy-1-methyl-3-(1H-1,2,4-triazol-1-yl)propyl]-3-[4-(1H-1-tetrazolyl)phenyl]-2-imidazolidinone (1b) and the 3-14-(1H-1,2,3-triazol-1-yl)phenyl]-2-imidazolidinone analog (1a) that possess an imidazolidine nucleus were established. The key synthetic intermediates, (2R,3R)-3-(2,2-diethoxvethyl)amino-2-(2,4-difluorophenyl)-1-(1H1,2,4-triazol-1-yl)-2-butanol (8) and (2R,3R)-2-(2,4-difiuorophenyl)-3-(2-h ydroxyethyl)amino-1-(1H-1,2,4-triazol-1-yl)-2-butanol (14), were prepared by the ring-opening reaction of the oxirane (2) with the corresponding 2-substituted ethylamines. The acetal (8) was converted to the imidazolidinones (1a, b) by condensation with the carbamates (10a, b) followed by treatment with hydrochloric acid and subsequent catalytic hydrogenation. The candidate selected for the clinical trials, 1b (TAK-456), was alternatively prepared from the hydroxyethylamino intermediate (14) via two reaction steps: condensation with the carbamate (10b) to the urea (15) and subsequent cyclization to the imidazolidinones. This newly developed synthetic route could be applied to a large scale preparation of 1b. 相似文献
993.
Sato J Saito N Yamada Y Maeda K Takata T Kondo JN Hara M Kobayashi H Domen K Inoue Y 《Journal of the American Chemical Society》2005,127(12):4150-4151
Germanium nitride beta-Ge3N4 dispersed with RuO2 nanoparticles is presented as the first example of a non-oxide photocatalyst for the stoichiometric decomposition of H2O into H2 and O2. All of the successful photocatalysts developed for overall water splitting over the past 30 years have been based on oxides of metals. The discovery of a non-oxide photocatalyst, such as nitrides and oxynitrides, achieving the same function is therefore expected to stimulate research on non-oxide photocatalysts. New opportunities for progress in the development of visible light-driven photocatalysis can thus be expected, as the higher valence band positions of metal nitrides compared to the corresponding metal oxides provide narrower band gaps, which are suitable for visible light activity. 相似文献
994.
Kenzi Hori Yutaka Ikenaga Takanori Takahashi Yoshiyuki Noguchi Hidetoshi Yamamoto 《Tetrahedron》2007,63(5):1264-1269
The mechanisms underlying the hydrolysis of methyl acetate and acetamide under acidic conditions were investigated using the MP2/6-311+G(d,p)//MP2/6-31+G(d,p) level of theory. It was necessary to include two water molecules as reactants to obtain a tetrahedral (TD) intermediate for the AAC2 mechanism that Ingold classified for the hydrolysis of methyl acetate. This mechanism includes two TS structures, one for the formation of the TD intermediate and the other for its decomposition. Since the activation energies were calculated to be 15.7 and 18.3 kcal mol−1, the second step determines the rate of hydrolysis. The calculated value was close to that observed at ∼16 kcal mol−1. It was confirmed that the AAC2 mechanism had a barrier lower by 9.9 kcal mol−1 than the AAL2 mechanism. The AAC2 mechanism is also applicable to the acid-catalyzed hydrolysis of acetamide. It is not the TD intermediate with which the NH3+ moiety forms, but one further step is required to produce the final products, acetic acid and ammonium ion. 相似文献
995.
Masao Kaneko Masahisa Ochiai Kazuhiko Kinosita Akira Yamada 《Journal of polymer science. Part A, Polymer chemistry》1982,20(4):1011-1019
The characteristics of the photoinduced electron transfer reaction from polystyrene pendant tris(2,2′-bipyridyl)ruthenium (II) complex [Ru(bpy)] to methylviologen (MV2+) were studied. The rate constant k1 from the excited state of the complex, Ru(bpy), to MV2+ were determined for both the polymeric and monomeric complexes from the lifetime τ of Ru(bpy) and the quenching rate of Ru(bpy) by MV2+. The polymer pendant Ru(bpy) showed three kinds of τ components ranging from 7 to 474 ns, in contrast to the monomeric complex, which showed one component of 350 ns. The k1 values for both complexes were almost the same, on the order of 108 L/mol s. The photoinduced electron transfer from solid-phase Ru(bpy) to liquid-phase MV2+ was realized by utilizing the polymer complex, and the solid–liquid interphase reaction system is discussed. 相似文献
996.
Md. Ruhul Amin Farhana Yasmin Mohammed Anowar Hosen Sujan Dey Shafi Mahmud Md. Abu Saleh Talha Bin Emran Imtiaj Hasan Yuki Fujii Masao Yamada Yasuhiro Ozeki Sarkar Mohammad Abe Kawsar 《Molecules (Basel, Switzerland)》2021,26(22)
A series of methyl β-D-galactopyranoside (MGP, 1) analogs were selectively acylated with cinnamoyl chloride in anhydrous N,N-dimethylformamide/triethylamine to yield 6-O-substitution products, which was subsequently converted into 2,3,4-tri-O-acyl analogs with different acyl halides. Analysis of the physicochemical, elemental, and spectroscopic data of these analogs revealed their chemical structures. In vitro antimicrobial testing against five bacteria and two fungi and the prediction of activity spectra for substances (PASS) showed promising antifungal functionality comparing to their antibacterial activities. Minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) tests were conducted for four compounds (4, 5, 6, and 9) based on their activity. MTT assay showed low antiproliferative activity of compound 9 against Ehrlich’s ascites carcinoma (EAC) cells with an IC50 value of 2961.06 µg/mL. Density functional theory (DFT) was used to calculate the thermodynamic and physicochemical properties whereas molecular docking identified potential inhibitors of the SARS-CoV-2 main protease (6Y84). A 150-ns molecular dynamics simulation study revealed the stable conformation and binding patterns in a stimulating environment. In-silico ADMET study suggested all the designed molecules to be non-carcinogenic, with low aquatic and non-aquatic toxicity. In summary, all these antimicrobial, anticancer and in silico studies revealed that newly synthesized MGP analogs possess promising antiviral activity, to serve as a therapeutic target for COVID-19. 相似文献
997.
Kazunobu Yamada Tamaki Nakano Yoshio Okamoto 《Journal of polymer science. Part A, Polymer chemistry》1999,37(14):2677-2683
Free-radical polymerization of vinyl esters including vinyl propionate (VPr), vinyl isobutylate (ViBu), vinyl 2,2-dimethylbutylate (VDMB), vinyl 2,2-dimethylvalerate (VDMV), vinyl 2,2-bis(trifluoromethyl)propionate (VF6Pi), and vinyl benzoate (VBz) was carried out using fluoroalcohols as solvents, and the tacticity of the obtained polymers was determined by NMR analysis of the produced poly(vinyl alcohol) (PVA). The polymerization of VPr, ViBu, VDMB, and VDMV, which are bulkier than VAc, in fluoroalcohols afforded polymers rich in heterotacticity (up to mr = 61%) similar to that of vinyl pivalate (VPi) whereas VAc is known to give a syndiotactic polymer under the reaction conditions used here. The polymerization of VF6Pi, which is the bulkiest among the monomers used in this study, gave a polymer rich in syndiotacticity in bulk and in fluoroalcohols regardless of the structure of the solvents. On the other hand, the polymerization of VBz in fluoroalcohols gave polymers with a higher isotacticity (up to mm = 33%) than bulk polymerization. Thus the monomer structure strongly affected the stereochemistry of the free-radical polymerization of vinyl esters in fluoroalcohols. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2677–2683, 1999 相似文献
998.
Nobuyuki Furukawa Yasuharu Yamada Masaya Furukawa Masatoshi Yuasa Yoshiharu Kimura 《Journal of polymer science. Part A, Polymer chemistry》1997,35(11):2239-2251
Two series of polysiloxane-block-polyimides were synthesized by the method of solution imidization of the polyamic acids prepared from the dianhydride/diamine combinations of 3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride (DSDA)/2,2-bis[4-(4-aminophenoxy) phenyl] propane (BAPP) (Series A) and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA)/bis[4-(3-aminophenoxy) phenyl] sulfone (BAPSM) (Series B) with three kinds of w-diamino-poly(dimethylsiloxane) with different number-average molecular weight added as a part of diamine. These polysiloxane-block-polyimides, having various compositions and chain lengths of the polysiloxane segments, were subjected to solution casting to prepare their films, and their surface and interface properties were analyzed by contact angle, XPS, AFM, and SEM. It was found that the surface tension and surface topography were greatly influenced by the composition and molecular weight of the polysiloxane segments because of their surface enrichment, which was affected by the environment and substrate with which the copolyimides had contacted. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2239–2251, 1997 相似文献
999.
Takakazu Yamamoto Yukiko Muramatsu Takahisa Shimizu Wataru Yamada 《Macromolecular rapid communications》1998,19(5):263-266
π-Conjugated polymers bearing nitro substituent(s), e.g., poly(aryleneethynylene) (PAE) type polymers and poly(4,8-dinitroanthraquinone-1,5-diyl) P(4,8-NO2-1,5-AQ), show semiconducting properties with electrical conductivities of an order of 10−7 to 10−6 S · cm−1 at room temperature without special oxidation and reduction of the polymer. P(4,8-NO2-1,5-AQ) shows a large shift of phase in alternating current (ac) measurements and a unique magnetism at low temperature. 相似文献
1000.
Tsuyoshi Okubo Shigeo Kohmoto Makoto Yamamoto Kazutoshi Yamada 《Journal of polymer science. Part A, Polymer chemistry》1998,36(4):603-610
N,N-dimethylacrylamide (DMAA) was graft copolymerized on poly[(trimethylsilyl)propyne] (PTMSP) by single electron reduction of PTMSP with potassium naphthalenide (K-Naph), followed by anion polymerization of DMAA from the carbanion formed in the reduction. A hard and practically non-water-swelling PTMSP-gr-poly(DMAA) was obtained under the conditions using controlled amount of K-Naph and DMAA. The graft copolymer was characterized with regard to structure, number-averaged molecular weight, and the amount of grafting poly(DMAA) determined by the relative absorbance of the IR absorption band assigned to the CO and SiC H functionalities (ACO/ASiC H). The oxygen permeability and water contact angle (θ) of the graft copolymer were evaluated while varying the amount of grafting poly(DMAA). The graft copolymer proved to be highly oxygen permeable (165 Barrers) and hydrophilic (θ = 27°). Its transparency was also elucidated with UV–vis spectra. This graft copolymer was proposed as a promising candidate for use as a hard contact lens material. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 603–610, 1998 相似文献