Search results for "Heterocyclic compound"
showing 10 items of 382 documents
Studies on the structure of coumarin-modified dextran nanoparticles by fluorescence spectroscopy.
2012
The photophysical and photochemical characteristics of nano-scaled particles obtained via solvent displacement from coumarin-modified dextrans were studied by means of absorption- and fluorescence-spectroscopy. The environment-dependent fluorescence emission of the pendant 4-methyl-7-alkoxy coumarin groups was exploited as a probe to gain information about the inner structure of the polysaccharide based nanoparticles. Time-resolved fluorescence measurements showed that the particles had two domains of different polarity and it could be confirmed that the core of the nano-assemblies contained water. Moreover, preliminary experiments were carried out demonstrating the possibility to control t…
Catalytic one-handed helix-induction and memory of amphiphilic poly(biphenylylacetylene)s in water
2020
Abstract A series of amphiphilic biphenylylacetylene-based homo- and copolymers (PBPAs) carrying chiral and/or achiral oligo(ethylene glycol) pendants at the 4’-position of the biphenyl units were synthesized and the amplification of the macromolecular helicity through noncovalent and/or covalent chiral interactions followed by the memory of the helicity were investigated in both water and organic solvents. The macromolecular helicity was efficiently induced in the homopolymers of achiral monomers through specific encapsulation of a catalytic amount of hydrophobic chiral guests in water and their induced helicities were stably memorized in water after complete removal of the optically-activ…
The comparative spreading behavior of enantiomeric and racemic tyrosine amphiphiles
1985
Several derivatives of tyrosine or its methyl ester have been synthesized in which the para hydroxyl group on the aromatic side chain has been converted to a long chain alkyl ether or urethane. The surface behavior of these compounds is discussed. Enantiomeric discrimination, the ability of a chiral molecule to distinguish between mirror-image stereoisomers, has been investigated for the urethane derivates by comparing the surface pressure-area isotherms of the enantiomer with that of the racemic compound. Enantiomeric discrimination was demonstrated for the methyl ester analog, but was not conclusively observed for the zwitterionic compounds. Possible structural requirements for enantiomer…
Levofloxacin effect on erlotinib absorption. Evaluation of the interaction in undernutrition situations through population pharmacokinetic analysis i…
2017
The main objective of this study was to develop a pharmacokinetic model in order to describe the intestinal absorption of erlotinib in rat and to quantify the interaction of levofloxacin on this process in well- and under-nourished rats. Absorption studies were performed in male Wistar rats. Concentration-time profiles in proximal and distal intestine were analysed through non-linear mixed effect modelling using the NONMEM software version 7.3. Simulations were performed in order to explore the influence of covariates on the apparent absorption rate constant. A passive absorption and an active secretion process best-described erlotinib absorption from lumen to enterocyte. The developed mode…
Cercospora beticola toxins. Part XVII. The role of the beticolin/Mg2+ complexes in their biological activity Study of plasma membrane H+-ATPase, vacu…
1996
Beticolin-1 and beticolin-2, yellow toxins produced by the phytopathogenic fungus Cercospora beticola, inhibit the plasma membrane H(+)-ATPase. Firstly, since beticolins are able to form complexes with Mg2+, the role of the beticolin/Mg2+ complexes in the inhibition of the plasma membrane proton pump has been investigated. Calculations indicate that beticolins could exist under several forms, in the H(+)-ATPase assay mixture, both free or complexed with Mg2+. However, the percentage inhibition of the H(+)-ATPase activity is correlated to the concentration of one single form of beticolin, the dimeric neutral complex Mg2H2B2, which appears to be the active form involved in the H(+)-ATPase inh…
Is the repair of oxidative DNA base modifications inducible by a preceding DNA damage induction?
2007
In mammalian cells, 7,8-dihydro-8-oxoguanine (8-oxoG) and some other oxidative guanine modifications are removed from the DNA by base excision repair, which is initiated by OGG1 protein. We have tested whether this repair is inducible in mouse embryonic fibroblasts (MEFs), MCF-7 breast cancer cells and primary human fibroblasts by a pretreatment with the photosensitizer Ro19-8022 plus light, which generates predominantly 8-oxoG, or with methyl methanesulfonate (MMS), which generates alkylated bases and abasic sites (AP sites). The results indicate that the repair rate of the oxidative guanine modifications induced by the photosensitizer was not increased if a priming dose of the oxidative o…
ChemInform Abstract: Selective Formal Transesterification of Fluorinated 2-(Trimethylsilyl)ethyl α-Imino Esters Mediated by TBAF.
2008
The scope of the transesterification reaction between β-fluorinated α-imino esters and various electrophiles in the presence of TBAF as fluorine source is described. The reaction is highly selective for alkyl iodides, bromides, and mesylates, while alkyl chlorides react at a significantly slower rate and tosylates do not react under the reaction conditions. This methodology represents a simple and useful alternative for the preparation of a wide variety of fluorinated α-imino esters.
Synthesis of [18F]-Fluoroethylfenoterol for imaging β2 receptor status in lung in vivo
2001
5-(-{2-[4-(2-[18F]Fluoroethoxy)-phenyl]-l-methyl-ethylamino}-l-hydroxy-ethyl)-benzene-1, 3-diol ([18F]fluoroethylfenoterol) was synthesised from 4-(2-{benzyl-[2-(3,5-bis-benzyloxy-phenyl)-2-hydroxy-ethyl]-amino}-propyl)-phenol using 2-[18F]fluoroethyltosylate (92% RCY) followed by reductive cleavage of the benzyl protecting groups. Preliminary in vitro tests showed [19F]fluoroethylfenoterol to be as potent in relaxation of lung tissue as fenoterol itself.
Palladium-Catalyzed Alkoxy- and Aminocarbonylation of α-Halomethyl Oxime Ethers: Synthesis of 1,3-Alkoxyimino Esters and 1,3-Alkoxyimino Amides
2014
The three component reactions of α-bromomethyl oxime ethers, carbon monoxide, and alcohols or aromatic amines give imino esters and amides, respectively.
Degradation of heterocyclic aromatic amines in oil under storage and frying conditions and reduction of their mutagenic potential.
2007
Heterocyclic aromatic amines (HAA) were systematically studied concerning their partition behavior in water/oil-systems and their thermostability in different animal derived fats and vegetable oils. Partitioning of IQx-compounds and PhIP in water/oil systems was found to depend on the polarity defined by the molecular structure and on the pH-value of the aqueous phase. In particular, beta-carbolines norharman and harman showed a significant strong lipophilic character at alkaline pH. After heating in frying fats at 130 degrees C, contents of IQx compounds and PhIP were reduced by more than 40% and after heating at 180 degrees C less than 10% of the HAA initial concentration was recovered. B…