Polymere, die Benzimidazol- und Chinazolindion-Einheiten in der Hauptkette enthalten

Ohne Zusammenfassung     

Syntheses of (±)-aklavinones : Application of the stereocontrolled “zipper” bicyclo cyclization reaction

Efficient syntheses of(1+-)-aklavinones; (±)-aklavinone (1), (±)-auramycinone (2), and (±)-13-methylaklavinone (3), are described. A key process of the tetracyclic ring construction in these syntheses is ia stereocontrolled “zipper” bicyclo-cyclization using a KH-Kryptofix 222 (4,7,13,16,21,24-hexaoxa-1.10-diazabicyclo [8.8.8]hexacosane) cryptate as a base. The reaction mechanism is discussed, too     

Analysis of active chemical species generated by electrolysis using non-aqueous capillary electrophoresis. Detection of the anion radical and the divalent anion of tetracyanoquinodimethane

We have investigated detection of the anion radical and the divalent anion of tetracyanoquinodimethane (TCNQ) by acetonitrile-CE under anaerobic conditions. With electrolysis at a potential of 0.0 V (vs. Ag/AgCl), an acetonitrile solution of TCNQ turned green, characteristic of the TCNQ anion radical (TCNQ-). Only one peak of the anionic compound was observed in CE of the electrolysis solution and it should be that of TCNQ-. Then, the electrolysis potential was shifted to -0.8 V expected to be sufficient potential for the further reduction of TCNQ-, and the solution turned almost colourless. In CE analysis of the latter solution, another anionic component possessing a larger electrophoretic mobility than that of TCNQ- was detected, and it was decomposed immediately under aerobic conditions. This product was strongly suggested to be the divalent anion of TCNQ, and the present method would contribute notably to detection of the unstable species.     

Evaluation of a new reagent: anthraquinone-2-sulfonyl chloride for the determination of phenol in water by liquid chromatography using precolumn phase-transfer catalyzed derivatization

A new reagent, anthraquinone-2-sulfonyl chloride, is used for the derivatizaton of phenols. Several compounds with different polarities are selected to evaluate the new reagent and derivatives of these phenols that are prepared via a facile pathway. The optimal conditions for analytical derivatization and mechanism of the derivatization reaction are discussed. The derivatization procedure involves an ion-pair extraction of the deprotonated phenols with a tetrabutylammonium counter ion in the organic phase. At the interface of two phases, the derivatization reaction occurs quantitatively at room temperature within 3 min. The derivatives are stable and readily amenable to analysis by normal-phase (NP) and reversed-phase (RP) high-performance liquid chromatography (HPLC). Excellent linearity response was demonstrated over the concentration range of 0.2-200 micromol/L at 320 nm for NP-HPLC and at 256 nm for RP-HPLC. Combined with preconcentration using a Waters Sep-Pak Plus C(18) cartridge, detection limits of phenols for water-sample analysis are as low as 1 x 10(-9) mol/L (approximately 0.1 microg/mL).     

Mesomorphic properties of 2-acyloxy5-(4-alkoxyphenylazo)tropones, 2-acyloxy-5-(4-alkylphenylazo)tropones, and 2-acyloxy-5-(4-alkoxycarbonylphenylazo)tropones

Three series of mesomorphic 2-acyloxy-5-phenylazotropones with alkoxy, alkyl, and alkoxycarbonyl groups at C-4 on the phenyl ring were prepared. It was known that the corresponding 5-phenylazotropolone derivatives and their methyl ethers were not mesomorphic. 2-Acetyl-5-(4-hexyloxyphenylazo)tropone, however, shows a monotropic smectic A phase. Even an acetyl group is therefore able to induce a mesophase. The effects of terminal substitution of the tropone ring by groups such as alkoxy, alkoxycarbonyl, and alkyl on the clearing points are discussed.     

Attachment of anthraquinone derivatives to glassy carbon and the electrocatalytic behavior of the modified electrodes toward oxygen reduction

The electrochemical reduction of oxygen on glassy carbon (GC) electrodes modified with anthraquinones was studied using cyclic voltammetry (CV) and the rotating disk electrode (RDE) technique. Two methods were used in surface modification. The first method comprised immersion of the polished or anodically pretreated GC electrode in a solution containing 9,10-anthraquinone-2-carboxylic acid (AQ-2-COOH) or its anion (AQ-2-COO⁻) in dimethylsulfoxide (DMSO) or 9,10-anthraquinone-2-ethanoic acid (AQ-2-CH₂COOH) or its anion (AQ-2-CH₂COO⁻) in N,N-dimethylformamide (DMF). Alternatively, the surface of the GC disk was modified by anodic oxidation of AQ-2-COOH or AQ-2-COO⁻ in DMSO or AQ-2-CH₂COOH in DMSO or DMF or AQ-2-CH₂COO⁻ in DMF. The modified electrodes showed electrocatalytic activity toward oxygen reduction in 0.1 M acetate buffer pH (4.8), 0.1 M phosphate buffer (pH 8) and 0.1 M NaOH. Atomic force microscopy (AFM) examination of the modified electrodes was carried out and the differences in surface morphology of various modifications were in evidence.     

Synthesis of antimicrobial agents. II. Syntheses and antibacterial activities of optically active 7-(3-hydroxypyrrolidin-1-yl)quinolones

Two optically active isomers of 1-ethyl-6,8-difluoro-1,4-dihydro-7-(3-hydroxypyrrolidin-1-yl)-4-oxoquinoline-3-carboxylic acid ( 10 ) were prepared. One of the isomer, 7-[(3S)-hydroxypyrrolidin-1-yl] derivative 8 , was about 4 times more potent in vitro than the other, 7-[(3R)-hydroxypyrrolidin-1-yl] derivative 4 , and approximately two times more active than the racemate, 7-[(3RS)-hydroxypyrrolidine-1-yl] derivative 10. Optical active 8 was the most active in in vivo, followed by 10 , and 4 was the least active compound. But, they were more potent than CI-934 12 and norfloxacin. From the results, (3S)-hydroxypyrrolidinyl group was found to be one of the beneficial group for PCA-anti-bacterial agent.     

Studies on imidazole derivatives as chelating agents-V Investigations of the applicabilities of the azoimidazoles as metallochromic indicators

Applicabilities of several azoimidazoles as metallochromic indicators were investigated in the light of the general equations expressing the colour change of the visual chelatometric titrations. By using the stability constants of the nickel(II), copper(II), zinc(II) and cadmium(II) chelates, the useful pH ranges, titration errors and sharpness of colour changes were predicted theoretically and the usefulness of these reagents as indicators was established experimentally. The Cu(II)-EDTA-indicator system was also examined experimentally. The OH-containing azoimidazoles could be applied to the direct titration of copper, nickel, zinc, cadmium, lead and bismuth and to the titration of calcium and cobalt in the presence of Cu(II)-EDTA. Attempts were made to construct diagrams for the estimation of titration errors and sharpness of colour changes.