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61.
Kagetoshi Yamamoto Shoko Yamazaki Yasuji Kohashi Ichiro Murata Yasushi Kai Nobuko Kanehisa Kunio Miki Nobutami Kasai 《Tetrahedron letters》1982,23(31):3195-3198
As an example of a simplest isolable monocyclic thiepin, 2,7-di-tert-butylthiepin (2) has been synthesized from 2,6-di-tert-butylthiopyrylium salt, and the thermal properties together with the X-ray crystal structure of (2) have been examined. 相似文献
62.
An interesting property of Gaussian 1/f noise was found experimentally a few years ago: The amplitude truncation does not change the power spectral density of the noise under rather general conditions. Here we present a brief theoretical derivation of this invariant property of band-limited Gaussian 1/f noise and include 1/f(alpha) noises also with 0=alpha<2. It is shown that when alpha=1, a transformation of keeping only the sign of the zero-mean 1/f(alpha) noise does not alter the shape of the spectral density. The theoretical results are extended to truncation levels differing significantly from the mean value. Numerical simulation results are also presented to draw attention to unsolved problems of amplitude truncation using asymmetric levels. (c) 2001 American Institute of Physics. 相似文献
63.
Masakatsu Matsumoto Naoyuki Hoshiya Ryo Isobe Yukie Watanabe Nobuko Watanabe 《Tetrahedron letters》2004,45(20):3895-3898
2-(Buta-1,3-dienyl)-3-methylpyrazines (5) and 3-(buta-1,3-dienyl)-4-methyl-1,2,5-oxadiazoles (10) were synthesized starting from base-induced reaction of 2,3-dimethylpyrazine or 3,4-dimethyl-1,2,5-oxadiazole with α,β-unsaturated carbonyls. The thus obtained heteroaromatics bearing a butadienyl moiety and a methyl at the adjacent position underwent intramolecular cyclization by the action of LDA to give the corresponding heteroaromatics fused with a seven-membered ring [7 (8)] and [11 (12)] in moderate to high yields. 相似文献
64.
[structure: see text] Polyenyne macrocycles with pi-extended [9]- and [12]radialene frameworks have been synthesized. These radialenes exhibit restricted rotation of the aromatic rings, and the D3- and D4-symmetric structures in solutions have been determined by dynamic NMR. The macrocyclic radialenes bear small to medium inner cavities, and the small cavity of the pi-extended [9]radialene can incorporate a silver cation. 相似文献
65.
New diphenylmethane-type 2,2'-dihydroxybisphenols (5a-d) were prepared regioselectively in good yields. We evaluated the antiviral activity of some bisphenol derivatives synthesized by the plaque reduction assay. Most of the compounds showed significant antiviral activity and the 4,4'-dihydroxybisphenol derivative (10) showed higher activity than 2,2'-bisphenol derivatives. This compound had EC50 value of 1.8 microg/ml. 相似文献
66.
Naokazu Yoshikawa Jun Sakamoto Takeko Matsumura-Inoue Hiroshi Takashima Keiichi Tsukahara Nobuko Kanehisa Yasushi Kai 《Analytical sciences》2004,20(4):711-716
Four useful polypyridine iridium(III) complexes in the form of [IrCl2L2]+ were prepared and their spectroscopic and electrochemical properties as well as X-ray crystallography were investigated. The ligands used were L = 2,2'-bipyridine, 4,4'-dimethyl-2,2'-bipyridine, 4,4'-diphenyl-2,2'-bipyridine, 1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline, and 2,2'-biquinoline. Synthetic methods were developed by a sequential ligand-replacement, which occurred in the reaction vessel using a microwave oven. All complexes showed that LUMOs are based on the pi-system contribution of the polypyridine ligand for [IrCl2(bpy)2]+, [IrCl2(dmbpy)2]+, [IrCl2(dpbpy)2]+, [IrCl2(phen)2]+, [IrCl2(dpphen)2]+ and [IrCl2(bqn)2]+. The HOMOs are also localized on the polypyridine ligand in the iridium complexes. It was found that [IrCl2L2]+ emits intense phosphorescence at room temperature. In particular, the use of dpbpy as ancillary ligands extends the lifetime (660 ns) of the 3(pi-pi*) excited states of Ir(III) polypyridine complexes. The complex [IrCl2(bqn)2]+ with electron acceptor substituents shows a large red-shift to 622 nm. It is noticed that iridium polypyridine complexes show intense emissions at various colors, such as yellow for [IrCl2(dmbpy)2]+ and red for [IrCl2(bqn)2]+ which can be applied to photosensitizers. The spectroscopic and electrochemical details are also reported herein. 相似文献
67.
Recent advances in DNA and protein-sequencing technologies have made an increasing number of primary structures available for theoretical investigations. The prediction of a higher-order protein, and nucleic acid structure in particular, is an area where computational approaches will be able to complement the lack of experimental observations. We review some of the problems related to structure predictions: sequence homology searches, secondary structure prediction in RNAs, and regular structure prediction in proteins. The first two are mathematically well-defined problems, for it is not usually necessary to consider long-range interactions. The solution to a smaller segment is a part of the solution to the entire sequence. Thus, the problem can be solved by dynamic programming algorithms. The prediction of protein structures poses a more complex combinatorial problem, as illustrated in our statistical mechanical treatment. A promising approximation is to calculate locally optimal structures stabilized by relatively short-range interactions, and then to include longer-range effects as interactions between the locally optimal structures. 相似文献
68.
Naokazu Yoshikawa Takeko Matsumura-Inoue Nobuko Kanehisa Yasushi Kai Hiroshi Takashima Keiichi Tsukahara 《Analytical sciences》2004,20(12):1639-1644
Hexafluorophosphate salts of mononuclear complexes [Ru(II)Cl(L)(terpy)]+ (L = dmbpy (1); dpbpy (2), sambpy (3), and dpp (7), and binuclear complexes [Ru(II)2Cl2(dpp)(terpy)2]2+ (8) and [Ir(III)Ru(II)Cl2(dpp)(terpy)2]3+ (9) were prepared and characterized. Abbreviations of the ligands are bpy = 2,2'-bipyridine, dmbpy = 4,4'-dimethyl-2,2'-bipyridine, dpbpy = 4,4'-diphenyl-2,2'-bipyridine, dpp = 2,3-bis(2-pyridyl)pyrazine, sambpy = 4,4'-bis((S)-(+)-alpha-1-phenylethylamido)-2,2'-bipyridine, and terpy = 2,2':6',2'-terpyridine. The absorption spectra of 8 and 9 are dominated by ligand-centered bands in the UV region and by metal-to-ligand charge-transfer bands in the visible region. The details of their spectroscopic and electrochemical properties were investigated. In both binuclear complexes, it has been found that the HOMO is based on the Ru metal, and LUMO is dpp-based. [Ir(III)Ru(II)Cl2(dpp)(terpy)2]3+, indicating intense emission at room temperature, and a lifetime of 154 ns. The long lifetime of this bimetallic chromophore makes it a useful component in the design of supramolecular complexes. 相似文献
69.
Ten carbamate pesticides including four suspected endocrine disruptors, methomyl, benomyl (carbendazim), aldicarb and carbaryl, were simultaneously analyzed by LC/ESI/MS. The influence of the matrix on the variation of the ion signal intensities of (M + H)+ and adduct ions was investigated. Although the intensities of three oxamyl ions changed depending on the matrix, the variation in the concentration calculation of oxamyl was reduced by using the sum total of the area value of two ions. The limits of the quantitation of ten pesticides without a concentration procedure were from 0.4 - 30 microg/l. The solid-phase recovery rates of ten pesticides spiked into tap water and raw water were in the range of 69-111%. Using this method, the concentrations of the pesticides in tap and raw water sampled at 14 monitoring points in Hyogo Prefecture were determined. Carbendazim in three raw water samples and carbofuran in one of these three samples were detected at low concentrations (less than 0.32 microg/l). 相似文献
70.
Masakatsu Matsumoto Yuka Takamido Kana Nomura Tamaki Shiono Nobuko Watanabe Hisako K. Ijuin 《Tetrahedron letters》2008,49(42):6145-6147
Spiro[1,2-dioxetane-3,1′-dihydroisobenzofuran] syn-3 bearing a hydroxy group at the 6-position (as a model syn-rotamer of parent dioxetane 4 bearing a 3-hydroxyphenyl group) and its isomer anti-3 (as a model anti-rotamer of 4) were synthesized. When these spiro-dioxetanes were treated with tetrabutylammonium fluoride (TBAF) in DMSO, anti-3 emitted light with high efficiency (ΦCL = 0.41), while the respective value for syn-3 was only 1/10 for anti-3. This significant difference in ΦCL between syn-3 and anti-3 was attributed to the difference in their singlet-chemiexcitation efficiencies. 相似文献