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981.
The high sensitivity that can be attained using an enzymatic system and mediated by 4-tert-butylcatechol (4-TBC) has been verified by on-line interfacing of a rotating biosensor and continuous flow/stopped-flow/continuous-flow processing. Horseradish peroxidase, HRP, [EC 1.11.1.7], immobilized on a rotating disk, in presence of hydrogen peroxide catalyzed the oxidation of 4-TBC, whose back electrochemical reduction was detected on glassy carbon electrode surface at −150 mV. Thus, when penicillamine (PA) was added to the solution, these thiol-containing compounds participate in Michael type addition reactions with 4-TBC to form the corresponding thioquinone derivatives, decreasing the peak current obtained proportionally to the increase of its concentration. The highest response for PA was obtained around pH 7. This method could be used to determine PA concentration in the range 0.02-80 μM (r = 0.998). The determination of PA was possible with a limit of detection of 7 nM, in the processing of as many as 50 samples per hour. The HRP-rotating biosensor was successfully applied to the determination of PA in pharmaceutical formulations. 相似文献
982.
An operationally simple oxidative methyl esterification of primary alcohols in good yields using an iodine‐mediated poly[4‐(diacetoxyiodo)styrene] in methanol at room temperature is described. The polymeric reagent can be regenerated and reused as an environmentally benign reagent. 相似文献
983.
O. B. Ryabova E. Yu. Khmel’nitskaya V. A. Makarov L. M. Alekseeva N. B. Grigor’ev V. G. Granik 《Russian Chemical Bulletin》2005,54(12):2873-2879
On heating at pH 6.86, 4-(N,N-dialkylthiocarbamoylthio)-5-nitropyrimidines are transformed into dithiolopyrimidines, which are either oxidized to bis(4-dialkylthiocarbamoylpyrimidin-5-yl)
disulfides or converted into 4,6-diamino-5-nitropyrimidine derivatives with carbon disulfide elimination. The direction of
the reaction is determined by the nature of a substituent in position 2 of pyrimidine and the bulk of the thiocarbamate substituent.
Mechanistic schemes for these processes were proposed.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2777–2783, December, 2005. 相似文献
984.
Qian-Feng Zhang Richard D. Adams Dieter Fenske 《Journal of inclusion phenomena and macrocyclic chemistry》2005,53(3):275-279
The self-assemblies of two pyrogallol[4]arenes held together by 48 intermolecular hydrogen bonds stably associate in the form of spherical hexameric capsules. The molecular structures of two hexameric capsules with large interior space were analyzed by single crystal X-ray crystallography. 相似文献
985.
《Tetrahedron》2004,60(4):885-891
threo and erythro diastereoisomers of the constrained amino acid (βMe)Phe can be obtained separately on a multigram scale through a three-step synthesis from the corresponding Z and E isomers of 2-phenyl-4(α-phenylethylidene)-5(4H)-oxazolone. The 5(4H)-oxazolones are readily available from acetophenone and hippuric acid. The four enantiomerically pure isomers of β-methylphenylalanine, (2R,3R)-(βMe)Phe, (2S,3S)-(βMe)Phe, (2R,3S)-(βMe)Phe and (2S,3R)-(βMe)Phe, have been prepared by HPLC resolution of the racemic precursors methyl threo (or erythro)-2-benzamide-3-phenylbutanoates. 相似文献
986.
Wolfgang Stadlbauer Rita Laschober Thomas Kappe 《Monatshefte für Chemie / Chemical Monthly》1991,122(10):853-861
Summary 4-Chloro-3-aryl-coumarins and quinolones2 a–e undergo thermolytic ring closure by reaction with sodium azide in refluxing dimethyl formamide to yield indolo[3,2-c]coumarins and indolo[3,2-c]quinolin-6(5H)-ones6 a–e. In the case of the coumarin2 a the azido coumarin5 can be isolated. The mono- and diazacoumestrol-dimethylethers6 a–c are converted into the coumestrol analogues7 a–c and their diacetyl derivatives8 a–c.
Potentielle nichtsteroidale Östrogene und Antiöstrogene, 4. Mitt.: Organische Azide in der Heterocyclensynthese, Teil 13: Synthese von Aza- und Diazacumöstrolen über Azidzwischenstufen
Zusammenfassung 4-Chlor-3-arylcumarine und-chinolone2 a–e reagieren thermolytisch mit Natriumazid in siedendem Dimethylfomamid unter Ringschluß zu Indolo[3,2-c]cumarinen und Indolo[3,2-c]chinolin-6(5H)-onen6 a–e. Nur aus dem Cumarinderivat2 a kann das zwischenzeitlich gebildete Azidocumarin5 isoliert werden. Die so erhaltenen Mono- und Diazacumöstroldimethylether6 a–c werden in die entsprechenden Cumöstrole7 a–c und ihre Diacetylderivate8 a–c umgewandelt.相似文献
987.
R. D. Apostolova I. V. Kirsanova E. M. Shembel 《Russian Journal of Electrochemistry》2006,42(2):173-182
Electrolytic (e) cobalt oxide of a spinel structure, e-Co3O4, is obtained from the sulfate and nitrate (aqueous, water-alcohol) solutions containing Co2+ with the aim of using it in thin-layer anodes of lithium-ion batteries. The physicochemical and structural properties of the synthesized compounds are examined using thermal and x-ray diffraction analyses, absorption IR spectroscopy, and atomic force microscopy. The electrochemical characteristics of e-Co3O4 are determined in breadboards of lithium power sources and in the lithiumion system LiCoO2/e-Co3O4. 相似文献
988.
3-Arylsydnone-4-carbonitrile oxides may undergo 1,3-dipolar cycloadditions with alkenes to produce the corresponding 3-aryl-4-(5-substituted-isoxazolin-3-yl)sydnones. The direct reaction of 3-arylsydone-4-carbohydroximic acid chlorides with alkenes may also give the same products, and with higher yield. 相似文献
989.
G. Bruno P. Capezzuto G. Cicala F. Cramarossa 《Plasma Chemistry and Plasma Processing》1986,6(2):109-125
Plasma-chemical reduction of SiCl4 in mixtures with H2 and Ar has been studied by optical emission spectroscopy (OES) and laser interferometry techniques. It has been found that the Ar:H2 ratio strongly affects the plasma composition as well as the deposition (r
D) and etch (r
E) rates of Si: H, Cl films and that the electron impact dissociation is the most important channel for the production of SiClx species, which are the precursors of the film growth. Chemisorption of SiClx and the reactive surface reaction SiClx+H–SiCl(x–1)0+HCl are important steps in the deposition process. The suggested deposition model givesr
D [SiClx][H], in agreement with the experimental data. Etching of Si: H, Cl films occurs at high Ar: H2 ratio when Cl atoms in the gas phase become appreciable and increases with increasing Cl concentration. The etch rate is controlled by the Cl atom chemisorption step. 相似文献
990.
In this study, the determination of 4-Bromoaniline (4-BA) in green algae Chlamydomonas reinhardtii (C. reinhardtii) was investigated by applying continuous-flow microextraction (CFME) combined with high-performance liquid chromatography
(HPLC). Continuous-flow microextraction was conducted in a homemade glass chamber, i.e. the sample solution flowed through
a constant volume drop of solvent in the chamber at a constant flow rate. The effects of different factors on extraction efficiencies
were also investigated and these factors included the kind of extraction solvent, solvent drop volume, sample flow rate, extraction
time and addition amount of salt. Under the optimum extraction conditions (extraction solvent, carbon tetrachloride; solvent
drop volume, 3.5 μL; sample flow rate, 1.0 mL min−1; extraction time, 10 min; no addition of salt), the calibration plot was set up by plotting peak area against a series of
4-Bromoaniline concentrations (0.01–10 μg mL−1) in aqueous solution. The correlation coefficient (r) was 0.9990. The limit of detection (LOD) was 0.6 ng mL−1. The precision of this method was obtained by successive five time analyses of 100-ng mL−1 standard solution of 4-Bromoaniline, and the relative standard deviation (RSD) was 3.5%. The concentration factor was calculated
by the ratio of peak area of the analyte obtained after and before extraction and found to be 10.6. 4-Bromoaniline residues
in Chlamydomonas. reinhardtii cells and tap water samples were satisfactorily analyzed according to the method described above. 相似文献