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71.
In the oxidation of alkyl sulfides bearing acidic α-hydrogens eiher with phenobarbital induced rabbit liver microsomal cytochrome P-450, or with the Udenfriend's model system (ferous perchlorate/ascorbic acid/oxygen system), both S-dealkylation and S-monoxygenation took place concurrently. Meanwhile, in the oxidation of simple alkyl sulfides, steeoselective S-monooxygenation was found of occur predominantly. 相似文献
72.
Koji Kano Keisuke Takuma Tsuyoshi Ikeda Daisuke Nakajima Yashuhiro Tsutsui Taku Matsuo 《Photochemistry and photobiology》1978,27(6):695-701
Abstract— Zn-tetraphenylporphyrin (ZnTPP), solubilized in non-ionic surfactant micelles, was found to sensitize photoreductions of some sodium anthraquinonesulfonatesz in the presence of ascorbic acid under anaerobic conditions. The reaction rate was increased by the addition of an anionic surfactant, while retardation was observed with a cationic surfactant. The pH-reaction rate profiles showed maxima located in the order corresponding to pKa-values for the semiquinone of each anthraquinone-sulfonate. A reaction scheme involving the formation of ZnTPP+ at the primary step, followed by back-reduction with ascorbic acid, is proposed. The reaction scheme is in good agreement with the results of flash photolysis. The surfactant micelles are suggested to aid the charge-separation between the ionic species just after the redox reaction involving the photoexcited ZnTPP and anthraquinonesulfonates. 相似文献
73.
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
74.
The Ag electrode surface of a solid electrolyte in its working state has been studied by X-ray photoelectron spectroscopy. The nature of the AgO system on the electrode is dependent on the temperature. There are three types of AgO systems at 400°C. Type 1 with an O is binding energy of 532.6 eV only appeared at 325°C. However, when the temperature was raised to 400°C, types II and III (with BEs 531.1 and 529.2 eV) appeared. These O is signals are discussed in detail. 相似文献
75.
Liquid-liquid extraction and spectrophotometric determination of palladium with 2-mercaptobenz-amide
2-Mercaptobenzamide (MBA) was investigated as a reagent for the extraction of palladium. The palladium complex of MBA was extracted into tributyl phosphate (TBP). The pKa of the ligand was 5.45 with the stability constant of the palladium complex β2=107.1. The composition of the complex in TBP was Pd:MBA:TBP=1:2:2. Addition of sodium chloride accelerated the rate of extraction. Various interfering ions could be masked with EDTA; Ag(I), Au(III), Os(VIII), Se(IV), Te(IV) etc. interfered. The molar absorptivity was 1.59×104 l mol?1 cm?1; 1–35 μg Pd could be determined at pH 6.0. 相似文献
76.
Makoto Ojika Hideo Kigoshi Kiyotake Suenaga Yoshifumi Imamura Kohji Yoshikawa Takeshi Ishigaki Akira Sakakura Tsuyoshi Mutou Kiyoyuki Yamada 《Tetrahedron》2012,68(4):982-987
Five cytotoxic macrolides, aplyronines D–H (4–8), were isolated from the Japanese sea hare Aplysia kurodai. They are new congeners of the antitumor compound aplyronine A (1), which was previously isolated from the same organism. Their structures were determined by spectroscopic analysis (NMR and MS). The cytotoxicity of these new compounds was evaluated in comparison with that of aplyronines A–C (1–3), suggesting the importance of the 7-O-seryl ester group for mediating the potent cytotoxicity of aplyronines. 相似文献
77.
78.
The reduction of iodine with azide, catalyzed by polythionates (tri-, tetra-, penta- and hexathionate) and thiosulfate, has been utilized as a postcolumn reaction for chromatographic determination of these sulfur oxyanions. The method is based on the separation of polythionates and thiosulfate on an octadecylsilica column with an acetonitrile–water (20:80, v/v) mobile phase (pH 5.0) containing 3 mM tetrapropylammonium hydroxide and 6 mM acetic acid, followed by photometric measurement of the residual iodine (as triiodide) from the catalytic postcolumn azide–iodine reaction after mixing a reaction solution containing azide and iodine with the column effluent. Chromatograms obtained for the sulfur oxyanions showed negative peaks as a result of the decrease in absorbance of background. The conditions for the catalytic postcolumn reaction of the sulfur oxyanions in the column effluents were established by varying the concentrations of azide, iodine, iodide and acetic acid in the reaction solution, and varying the flow-rate, reaction temperature and length of the reaction tube. The detection limits (defined as S/N=3) were 4.3 μM for trithionate, 0.10 μM for tetrathionate, 2.7 nM for pentathionate, 5.0 nM for hexathionate and 1.1 nM for thiosulfate. When compared with earlier methods, the proposed method gave a much higher sensitivity for the determination of two polythionates (penta- and hexathionate) and thiosulfate. This method was applied successfully to the analysis of polythionates and thiosulfate added to hot-spring water samples. 相似文献
79.
Banana-shaped molecules, e.g. 1,3-phenylene bis[4-(4-n-alkoxyphenyliminomethyl)benzoates] and 1,3-phenylene bis[4-(4-n-alkylphenyliminomethyl)benzoates], form ferroelectric and chiral smectic phases without a chiral carbon. 13C NMR measurement suggested that 1,3-benzenediol dibenzoate (BD) moiety assumes asymmetrically twisted conformation which may be ascribed to the chirality of the phases. In this study, conformational analysis was carried out for BD by using the density functional theory (DFT) calculation. The results indicated that the asymmetrical twist conformation of the BD moiety is most stable. 相似文献
80.
Kimura T Yao S Watanabe K Kondo S Ho IK Yamamoto I 《Chemical & pharmaceutical bulletin》2001,49(1):111-113
Methyl (2), ethyl (3), propyl (4), butyl (5), allyl (6), benzyl (7), o-, m-, p-xylyl (8-10), and alpha-phenylethyl (11) derivatives of arabinofuranosyluracil (1) were synthesized and their pharmacological effects in mice were examined by using hypnotic activity and synergism with pentobarbital as indices for the CNS depressant effects. At a dose of 2.0 micromol/mouse by intracerebroventricular injection, the values of mean sleeping time induced by 7-11 were 144, 154, 117, 33, and 34 min, respectively, whereas the alkyl (2-6) derivatives did not cause any hypnotic activity. N3-o-Xylylarabinofuranosyluracil (8) displayed the most potent hypnotic activity among the derivatives tested. Certain derivatives (6-11) significantly prolonged the pentobarbital-induced sleeping time compared to control. The present study indicated that substitution with benzyl and/or related groups on the N3-position of arabinofuranosyluracil produced CNS depressant effects. 相似文献