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31.
Kiyoshi Tanemura Yoko Nishida Tsuneo Suzuki Koko Satsumabayashi Takaaki Horaguchi 《Journal of heterocyclic chemistry》1997,34(2):457-460
1,3-Dithianes 1 , 1,3-dithiolanes 2 , and diphenyl dithioacetals 3 derived from cinnamaldehydes reacted with 2,3-dichloro-5,6-dicyano-p-benzoquinone in aqueous solvents to give benzaldehydes 4 . Hydride transfer from 1–3 to 2,3-dichloro-5,6-dicyano-p-benzoquinone followed by hydrolysis and oxidative carbon-carbon bond cleavage would produce benzaldehydes 4 . 相似文献
32.
Potentiometric stripping determination of Cd, Cu and Zn using a vibrating electrode (VE) is presented. A simple VE was constructed
by using a piezoelectric bimorph oscillator and an inexpensive graphite-reinforcement carbon (GRC) rod (a mechanical pencil).
Experimental results obtained with the simple VE follow the equation valid for quantitative application of potentiometric
stripping analysis (PSA) in large solutions. It was found that the GRC vibrating electrode is suitable for multielement trace
analysis of small samples of 0.05 mL. The relative standard deviations for divalent metals are better than 2%.
Received: 3 February 1997 / Revised: 2 June 1997 / Accepted: 7 June 1997 相似文献
33.
The synthesis and properties of novel anthracene-bridged porphyrin dimers having an oxomolybdenum(V) porphyrin unit, H(2)(DPA)[Mo(V)O(OMe)] (1) and (DPA)[Mo(V)O(OMe)][Zn(II)(MeOH)] (2), and the relevant monomer porphyrin complexes Mo(V)O(MPP)OMe (3) and Zn(II)(MPP) (4) are presented. An oxomolybdenum(V) unit was introduced into one of the two porphyrins in DPA to give 1, which has a free-base porphyrin unit. By introducing a zinc(II) ion to the free-base part, a mixed-metal complex of 2 was prepared and isolated. The structure of 2 was analyzed by X-ray crystallography (2.(7)/(6)CH(2)Cl(2), triclinic, P(-)1 (no. 2), a = 15.2854(12) A, b = 19.9640(15) A, c = 13.6915(12) A, alpha = 90.968(3), beta = 113.108(4), gamma = 96.501(4), Z = 2, R1 = 9.9, wR2 = 19.2). The structure of 2 demonstrated that a methanol is stably coordinated to the Zn(II) ion with the aid of a hydrogen bond to the methoxo ligand on the Mo(V) ion in the binding pocket of DPA. The electrochemical measurements of 2 suggested that the methanol was kept in the pocket of DPA in solution even at the reduced state of the molybdenum ion. 相似文献
34.
Arakawa M Hasegawa K Funatsu K 《Journal of chemical information and computer sciences》2003,43(5):1390-1395
Molecular alignment is an important step in three-dimensional quantitative structure-activity relationship (3D-QSAR) such as comparative molecular field analysis (CoMFA). A reasonable molecular alignment is necessary for building a 3D-QSAR model. In this paper, a novel method for molecular alignment using the Hopfield Neural Network (HNN) is introduced. Four kinds of chemical properties are assigned to each atom of a molecule. Then, those properties between two molecules correspond to each other using HNN. To validate our method, HNN was applied to 12 pairs of enzyme inhibitors cited from the Protein Data Bank (PDB). As a result, our method could successfully reproduce the real molecular alignments obtained from X-ray crystallography. 相似文献
35.
A simple, accurate and reproducible reversed-phase high-performance liquid chromatography (HPLC) method was developed for the separation and characterisation of alkylphenols (APs) and alkylphenol polyethoxylates (APEOs), using a C18 octadecyl silica (ODS) column. APs and each APEO oligomer were separated successfully within a reasonable time without gradient elution. An excellent resolution was obtained, even for mixtures of APs and low EO number APEOs, which are otherwise difficult to separate using conventional normal-phase HPLC methods. This method, combined with solid-phase extraction, was highly applicable for the simultaneous determination of alkylphenols and alkylphenol ethoxylates in real samples. 相似文献
36.
Masakazu Uramoto Kimie Kobinata Kiyoshi Isono Tsutomu Higashijima Tatsuo Miyazawa Ellen E. Jenkins James A. McCloskey 《Tetrahedron》1982,38(11):1599-1608
New chitin synthetase inhibitors, neopolyoxins A, B, and C were isolated from the culture filtrate of Streptomyces cacaoi subsp. asoensis. Their absolute structures have been established on the basis of chemical and spectroscopic evidence. They are structural analogs of the polyoxins. As a nucleobase, neopolyoxin C possesses uracil, while neopolyoxins A and B contain the imidazoline moiety. A ring contraction reaction of pyrimidine nucleoside into imidazoline nucleoside played a key role in the structure determination of the nucleoside moiety. A similar transformation was suggested for the biosynthesis of neopolyoxins A and B. 相似文献
37.
Carbazoledioxazines with an angular type structure (5,15-dialkyl-7,17-dialkyloxy-9,19-dichloro-5,15-dihydrodiindolo[2,3-c:2′,3′-n]triphenodioxazines) were selectively synthesized by electrochemical oxidative ring closure of precursors (2,5-bis(9-alkyl-2-alkyloxy-3-carbazolylamino)-3,6-dichloro-1,4-benzoquinones). The structure was confirmed by 1H-nmr and other instrumental analyses. Their thermal properties and solubilities were investigated and were compared with those of carbazoledioxazines with a linear type structure. 相似文献
38.
Yasuhide Yukawa Hisao Morisaki Kiyoshi Tsuji Seung-Geon Kim Takashi Ando 《Tetrahedron letters》1981,22(51):5187-5190
The behavior of ion pairs in the trifluoroacetolysis of 2-arylethyl arenesulfonates was studied by means of tracer techniques with deuterium and oxygen-18. 相似文献
39.
Kyoichiro Shibatani Yuzuru Fujiwara Kiyoshi Fujii 《Journal of polymer science. Part A, Polymer chemistry》1970,8(7):1693-1703
High-resolution proton magnetic resonance and infrared spectra of poly(vinyl formal) were studied in comparison with those of the model formals obtained from stereoisomers of pentane-2,4-diol and heptane-2,4,6-triol in order to learn spectral changes due to differences of the steric structures of the polymer. In the NMR spectrum of transformal obtained from dl diol or dl,dl (syndiotactic) triol, all proton signals were well interpreted by assuming a rapid chair-chair inversion of the formal ring. On the other hand, no such inversion was observed spectroscopically in cis-formal obtained from the meso diol or meso,meso (isotactic) triol, and the cis-formal ring was supposed to take a diequatorial form preferentially. Consequently, dioxymethylene protons gave a single peak (equivalent) in trans-formal and an AB quartet (nonequivalent) in cis-formal. In the spectra of poly(vinyl formal), the dioxymethylene signal was an overlap of the singlet and quartet in dimethylsulfoxide solution. Observations of the spectra of various poly(vinyl formals) obtained from poly(vinyl alcohols) of different tacticities and study of temperature dependence of the signal have shown that the singlet and quartet are attributed to trans- and cis- formals, respectively, in the polymer spectrum also. In the infrared spectra of poly(vinyl formals), the 800 and 785 cm-1 bands were found to be related to cis- and trans-formal rings respectively. A linear relationship was confirmed between D785/D800 and trans/cis ratios determined from the peak intensities of the dioxymethylene proton signals. 相似文献
40.
Hiroyuki Koshino Hiroyuki Osada Tatsuya Yano Jun Uzawa Kiyoshi Isono 《Tetrahedron letters》1991,32(52):7707-7710
The structures of enopeptins A and B, novel depsipeptide antibiotics with 1,3,5,7,9-decapentaene-1,10-dicarboxylic acid and 2-amino-3-hydroxycyclopent-2-enone in a side chain, were determined by chemical and spectroscopic means. 相似文献