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At least 163 records · Page 9Linked to original sources
PubMed2000

Annulation strategies for benzo[b]fluorene synthesis: efficient routes to the kinafluorenone and WS-5995 antibiotics.

Intramolecular palladium-mediated arylation approaches to benzo[b]fluorenes have been investigated. The methodology has been applied in a short synthesis of tri-O-methylkinafluorenone, providing an effective alternative to Friedel-Crafts-based approaches. During the course of this work, an acid-promoted quinolactonization of naphthoquinones was also developed, providing direct access to either ortho or para isomers as desired. Application of this methodology in syntheses of the antibiotics WS-5995A, WS-5995C, and functional analogues was demonstrated, and antitumoral activity of this class was determined.

Antibiotics, Antineoplastic↗
PubMed2002

Synthesis of suspected carcinogenic metabolites of 7H-benzo[c]fluorene, a coal tar component implicated in causation of lung tumors.

High incidences of lung tumors were observed in mice fed coal tar in their diet. The principal component of tar that gives rise to DNA-bound adducts in mouse lung was identified as 7H-benzo[c]fluorene (BcF). We now report the synthesis of suspected active metabolites of BcF, specifically the trans-3,4-dihydrodiol of BcF (2), its likely proximate carcinogenic metabolite, and the corresponding anti- and syn-diol epoxides of BcF (3 and 4) in which the epoxide ring resides in the pseudobay region. The diol epoxide derivatives (3 and 4) are postulated to be ultimate carcinogenic metabolites of BcF that bind to DNA in mouse lung.

Animals↗
PubMed2006

Photofragmentation of the fluorene cation: II. Determination of the H-loss energy-dependent rate constant.

The hydrogen-loss channel, induced by sequential multiphoton absorption, of the vapor-phase fluorene cation was investigated using a pulsed supersonic molecular beam, a time-of-flight mass spectrometer, and pulsed nanosecond lasers. Our new method leads to the determination of the absolute absorption cross section. Its attenuation with the number of absorbed photons has been approximated by means of statistical models. A model-free determination of the evolution of the dissociation rate constant in a relatively large energy range was obtained by solving the set of coupled differential kinetic equations numerically. Particular attention was focused on the data analysis techniques. The free fit of these rate constants is close to the photothermodissociation statistical model, but shows a discrepancy with the Rice and Ramsperger and Kassel model mainly at high energy. The resulting activation energy is in agreement with both that deduced from the ab initio calculations and that from the tight-binding energy potential surface model.

Cations↗
PubMed2006

Theoretical studies of symmetric five-membered heterocycle derivatives of carbazole and fluorene: precursors of conducting polymers.

Structures, electron ionization and excitation energies, and electron density distribution are studied for carbazole and fluorene derivatives substituted symmetrically by thiophene, ethylenodioxythiophene, furane, or pyrrole. The calculated properties of the molecules directly or indirectly mimic molecular parameters that are important for the design of processes of polymerization or for modeling the final polymer. The studies have been focused on the variation in the properties as a function of the chemical composition of the central fragment and the external rings. The calculated properties of consecutive oligomers indicate their fast convergence to values characterizing polymers.

Carbazoles↗
PubMed2004

Resonant enhancement of two-photon absorption in substituted fluorene molecules.

The degenerate and nondegenerate two-photon absorption (2PA) spectra for a symmetric and an asymmetric fluorene derivative were experimentally measured in order to determine the effect of intermediate state resonance enhancement (ISRE) on the 2PA cross section delta. The ability to tune the individual photon energies in the nondegenerate 2PA (ND-2PA) process afforded a quantitative study of the ISRE without modifying the chemical structure of the investigated chromophores. Both molecules exhibited resonant enhancement of the nonlinearity with the asymmetric compound showing as much as a twentyfold increase in delta. Furthermore, the possibility of achieving over a one order of magnitude enhancement of the nonlinearity reveals the potential benefits of utilizing ND-2PA for certain applications. To model ISRE, we have used correlated quantum-chemical methods together with the perturbative sum-over-states (SOS) expression. We find strong qualitative and quantitative correlation between the experimental and theoretical results. Finally, using a simplified three-level model for the SOS expression, we provide intuitive insight into the process of ISRE for ND-2PA.

Fluorenes↗
PubMed1987

Methylated derivatives of pyrene and fluorene: evaluation of genotoxicity in the hepatocyte/DNA repair test and tumorigenic activity in newborn mice.

The genotoxicity of 1-methylpyrene, 1,6-dimethylpyrene, 1-methylfluorene, 9-methylfluorene, and 1,9-dimethylfluorene was evaluated in the hepatocyte primary culture/DNA repair test, and the tumorigenic potency of these compounds was tested by bioassay in newborn mice. With the exception of 1-methylfluorene, all of these methylated polycyclic aromatic hydrocarbons are known mutagens in Salmonella typhimurium. Both 1-methylpyrene and 1,6-dimethylpyrene induced unscheduled DNA synthesis in rat hepatocytes. However, only 1-methylpyrene was tumorigenic when administered to newborn male mice. None of the methylated fluorenes assayed in the hepatocyte primary culture/DNA repair test induced unscheduled DNA synthesis. While 1,9-dimethylfluorene exhibited weak tumorigenic activity when administered by subcutaneous injection to newborn mice, 1-methylfluorene and 9-methylfluorene were inactive.

Animals↗
PubMed2005

The fluorene catabolic linear plasmid in Terrabacter sp. strain DBF63 carries the beta-ketoadipate pathway genes, pcaRHGBDCFIJ, also found in proteobacteria.

Terrabacter sp. strain DBF63 is capable of degrading fluorene (FN) to tricarboxylic acid cycle intermediates via phthalate and protocatechuate. Genes were identified for the protocatechuate branch of the beta-ketoadipate pathway (pcaR, pcaHGBDCFIJ) by sequence analysis of a 70 kb DNA region of the FN-catabolic linear plasmid pDBF1. RT-PCR analysis of RNA from DBF63 cells grown with FN, dibenzofuran, and protocatechuate indicated that the pcaHGBDCFIJ operon was expressed during both FN and protocatechuate degradation in strain DBF63. The gene encoding beta-ketoadipate enol-lactone hydrolase (pcaD) was not fused to the next gene, which encodes gamma-carboxymuconolactone decarboxylase (pcaC), in strain DBF63, even though the presence of the pcaL gene (the fusion of pcaD and pcaC) within a pca gene cluster has been thought to be a Gram-positive trait. Quantitative RT-PCR analysis revealed that pcaD mRNA levels increased sharply in response to protocatechuate, and a biotransformation experiment with cis,cis-muconate using Escherichia coli carrying both catBC and pcaD indicated that PcaD exhibited beta-ketoadipate enol-lactone hydrolase activity. The location of the pca gene cluster on the linear plasmid, and the insertion sequences around the pca gene cluster suggest that the ecologically important beta-ketoadipate pathway genes, usually located chromosomally, may be spread widely among bacterial species via horizontal transfer or transposition events.

Actinomycetales↗
PubMed1996

Two P21/n monoclinic phases of fluorene-4-carboxylic acid at 296 K.

The structures of two phases of fluorene-4-carboxylic acid, C14H10O2, from room-temperature growths have been determined. In the alpha phase, O-H...O hydrogen bonding occurs via cyclic dimers about a center of symmetry; in the beta phase, cyclic dimers with O-H...O hydrogen bonds are formed between two crystallographically inequivalent molecules and do not involve a center of symmetry, though centers of symmetry are present in the crystal. The present evidence strongly suggests that the beta phase is metastable with respect to the alpha phase at room temperature, but the regions of stability have not been determined.

Crystallization↗
PubMed1998

9-Hydroxy-9-(3-methylbut-3-en-1-ynyl)-9H-fluorene-1-carbonitrile.

The N atom in the title compound, C19H13NO, lies -0.0365 (14) A from the plane formed by the fluorene system, and the C [symbol: see text] N distance is 1.143 (2) A. The C [symbol: see text] C distance is 1.191 (2) A, and the ethynyl group deviates slightly from linearity, with C-C [symbol: see text] C-C bond angles of 172.0 (1) and 176.1 (2) degrees. Terminal CH2 and CH3 groups are 50:50 disordered, with equal C-C distances of 1.408 (3) and 1.406 (3) A.

Crystallography, X-Ray↗
PubMed1989

Transverse location of new fluorene based depth dependent fluorescent probes in membranes--quenching studies with 9,10-dibromostearic acid.

Fluorescence quenching technique has been used to determine the transverse location of the fluorescent fluorenyl fatty acids in single bilayer vesicles prepared from phosphatidylcholine. The fluorenyl fatty acids used here are 2-fluorenyl acetic, butyric, hexanoic and octanoic acid. In addition a new type of fluorescent probe, 7-n-butyl-fluorene-2-butyric acid, wherein a hydrophobic tail is attached to 2-fluorenyl-butyric acid has also been used to study its effect on alignment of these probes in the membrane. The association properties of the quencher 9,10-dibromostearic acid have been analysed. It is observed that the quencher association involves partitioning into the vesicles and does not involve any binding to the vesicles. The absolute partition coefficient of the 9,10-dibromostearic acid which partitions between the aqueous and the lipid phases of the phospholipid dispersion has been evaluated. Using this information the corrected Stern-Volmer plots were drawn and the bimolecular quenching constant evaluated.

Fatty Acids↗
PubMed1993

Microbial degradation of dibenzofuran, fluorene, and dibenzo-p-dioxin by Staphylococcus auriculans DBF63.

Staphylococcus auriculans DBF63, which can grow on dibenzofuran (DBF) or fluorene (FN) as the sole source of carbon and energy, was isolated. Salicylic acid and gentisic acid accumulated in the culture broth of this strain when DBF was supplied as a growth substrate. Also, the formation of 9-fluorenol, 9-fluorenone, 4-hydroxy-9-fluorenone, and 1-hydroxy-9-fluorenone was demonstrated, and accumulation of 1,1a-dihydroxy-1-hydro-9-fluorenone was observed when this strain grew on FN. On the basis of these results, the degradation pathways of DBF and FN were proposed. The analogous oxidation products of dibenzo-p-dioxin were obtained by incubation with DBF-grown S. auriculans DBF63 cells.

Benzofurans↗
PubMed1995

Competitive metabolism of naphthalene, methylnaphthalenes, and fluorene by phenanthrene-degrading pseudomonads.

Polynuclear aromatic hydrocarbons (PAHs) typically exist as complex mixtures in contaminated soils, yet little is known about the biodegradation of PAHs in mixtures. We have isolated two physiologically diverse bacteria, Pseudomonas stutzeri P-16 and P. saccharophila P-15, from a creosote-contaminated soil by enrichment on phenanthrene as the sole carbon source and studied their ability to metabolize several other two- and three-ring PAHs. Naphthalene, 1-methylnaphthalene, and 2-methylnaphthalene served as growth substrates for both organisms, while fluorene was only cometabolized. We also studied the effects of these compounds on initial rates of phenanthrene uptake in binary mixtures. Lineweaver-Burk analysis of kinetic measurements was used to demonstrate competitive inhibition of phenanthrene uptake by all four compounds, suggesting that multiple PAHs are being transformed by a common enzyme pathway in whole cells. Estimates of the inhibition coefficient, Ki, are reported for each compound. The occurrence of competitive metabolic processes in physiologically diverse organisms suggests that competitive metabolism may be a common phenomenon among PAH-degrading organisms.

Binding, Competitive↗
PubMed1975

Drug-induced foam cell reactions in rats, II. Chemical analysis of lipids stored in lungs and foam cells after treatment with chlorphentermine, 5-[p-(fluoren-9-ylidenemethyl)phenyl]-2-piperidineethanol (RMI 10.393) and 1-chloramitriptyline.

Lipidosis and foam cell reaction was induced in rat lungs by repeated administration of chlorphentermine, RMI 10.393 (=5-[p-(fluoren-9-ylidenemethyl)phenyl]-2-piperidineethanol), and 1-chloramitriptyline. Foam cell and lung lipids were extracted and separated in classes by thin-layer chromatography. Phospholipids were determined by phosphorus analysis, while neutral lipids were measured densitometrically. In lungs of drug-treated rats lecithin, phosphatidyl glycerol, phosphatidic acid, phosphatidyl inositol and free fatty acids accumulated in varying amounts. All other lipids were present in normal or reduced concentrations. Foam cells of chlorphentermine- and RMI 10.393-treated rats contained mainly phospholipids, i.e. lecithin and only small amounts of neutral lipids, i.e. cholesterol. Foam cells induced by 1-chloramitriptyline contained besides phospholipids also large amounts of neutral lipids, i.e. cholesterol, free fatty acids and cholesterol esters. This study and recent reports of others show that certain drugs produce a generalized metabolic disturbance characterized by accumulation of various lipids in several tissues. The distribution patterns of lipids induced by various drugs may differ considerably. This indicates that several biochemical mechanisms may be involved in the pathogenesis of drug-induced lipidosis.

Amitriptyline↗
PubMed1991

Influence of 5-[2-(N,N-dimethylamino)ethoxy]-7-oxo-7H-benzo(C)fluorene hydrochloride (benflurone) on the activity of rat liver aspartate and alanine aminotransferases.

The influence of repeated s.c. administration of the cytostatic 5-[2-(N,N-dimethylamino)ethoxy]-7-oxo-7H-benzo(c)fluorene hydrochloride (benflurone, 25 mg/kg body weight daily) on the activities of aspartate and alanine aminotransferases (AST, ALT) per g of tissue, and protein concentration in the liver of adult male rats was studied. During the first week of benflurone administration, the activities of ALT and AST decreased by 2/3 and 1/3, respectively, in comparison with controls while the protein concentration did not show any substantial change. No in vitro influence of benflurone on AST and ALT was found even at the highest concentration tested (10(-4) M). The significance of the aminotransferase decrease after treatment with benflurone and possible participation of these changes in the side- or cytostatic effects of the compound are considered.

Alanine Transaminase↗
PubMedDate not supplied

Enantioselective disposition and protein binding of [(5,6-dichloro-9a-propyl-3-oxo-2,3,9,9a-tetrahydro-1-H-fluoren-7 -yl)-oxy] acetic acid, a new cerebral antiedemic agent, in rats.

[(5,6-Dichloro-9a-propyl-3-oxo-2,3,9,9a-tetrahydro-1-H-fluoren-7-y l)-oxy] acetic acid (DPOFA) is an agent capable of reducing the swelling of astroglial cells in brain tissues. In vitro studies have demonstrated that the (R)-(+)-form of DPOFA is more effective than its (S)-(-)-form in inhibiting tissue swelling. The purpose of this study is to compare the elimination kinetics of the enantiomers. A new stereoselective HPLC procedure was developed for the simultaneous quantitation of (R)-(+)- and (S)-(-)-enantiomers in plasma and bile samples. After iv administration of the racemic mixture (40 mg/kg), rats cleared the (R)-(+)-enantiomer more rapidly than the (S)-(-)-isomer; time-averaged total plasma clearances were 8.88 +/- 0.55 and 4.20 +/- 0.70 ml/min/kg (mean +/- SD), respectively. Similar results were observed when the individual isomers were administered (20 mg/kg iv). Both (R)-(+)- and (S)-(-)-enantiomers were highly bound to plasma protein. The (R)-(+)-isomer had a higher unbound fraction (2%) than did the (S)-(-)-enantiomer (0.8%). The intrinsic clearance of unbound drug for (R)-(+)- and (S)-(-)-enantiomers were 434 +/- 27 and 490 +/- 84 ml/min/kg, respectively, suggesting that the differences in the elimination of the enantiomers in rats were attributable to stereoselectivity in plasma protein binding rather than to enzyme activity. In vitro studies with isolated hepatocytes supported the hypothesis that there was no stereoselectivity in metabolism of the enantiomers.

Animals↗