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At least 73 records · Page 4Linked to original sources
PubMed1993

Isolation and characterization of (+)-1,1a-dihydroxy-1-hydrofluoren-9-one formed by angular dioxygenation in the bacterial catabolism of fluorene.

Transformation of fluorene by washed cells of fluorene-grown Pseudomonas sp. F274 yielded 1,la-dihydroxy-1-hydrofluoren-9-one (up to 100 mg/l) as the stable product of angular dioxygenation of 9-fluorenone. Structural identity of the angular keto-diol was established by 13C- and 1H-NMR, gas chromatography- and direct probe-mass spectrometry. Definitive assignment of 1,1a-dioxygenation, but not 4,4a-, was based on the isolation and rigorous identification of 1-hydroxyfluoren-9-one as the exclusive product of acidic dehydration. Chiral 1H-NMR analysis and optical rotation of isolated 1,1a-dihydroxy-1-hydrofluoren-9-one ([alpha]D = + 132.1 degrees) are indicative of a single enantiomer with an inferred cis-stereochemistry of the hydroxyl groups. This compound is evidently an intermediate of fluorene catabolism by this strain and not a dead-end product because its formation is transient in washed cell incubations and ultimately it is completely consumed with the formation of acidic metabolites.

Fluorenes↗
PubMed1984

Chromatographic characterization of in vitro metabolites of 5-[2-(N,N-dimethylamino)ethoxy]-7-oxo-7H-benzo[c]fluorene.

Detection reactions and RF values in thin-layer chromatography on silica gel were studied for the antineoplastic drug Ih (benfluron) and related substances. On incubation of Ih with homogenate fractions of mammalian livers the N-oxide Ii and 5-[2-(N,N-dimethylamino)ethoxy]-7-hydroxy-7 H-benzo[c]fluorene (IIh) were established as products, and 5-[2-(N-methylamino)ethoxy]-7-oxo-7 H-benzo[c]fluorene (Ig), 5-[2-(N-methylamino)ethoxy]-7-hydroxy-7 H-benzo[c]fluorene (IIg) and a phenolic product of benfluron (IV) were tentatively identified.

Animals↗
PubMed2002

Influence of surfactants on solubilization and fungal degradation of fluorene.

Eighteen fungal strains were tested in toxicity assays with surfactants in order to select surfactants and strains tolerant to surfactants for degradation assays. Two nonionic surfactants were used, an alkylphenol ethoxylate, Triton X-100, a sorbitan ester, Tween 80 and an anionic surfactant, sodium dodecyl sulfate. Solubilization and biodegradation tests were conducted in liquid medium batch; fluorene was quantified by HPLC. Results showed the enhancement of fluorene solubilization by the three surfactants, good tolerance of nonionic surfactants by the fungal strains and the enhancement of the biodegradation of fluorene by Doratomyces stemonitis (46-62%) and Penicillium chrysogenum (28-61%) in the presence of Tween 80 (0.324 mM) after 2 days.

Biodegradation, Environmental↗
PubMed2000

Synthesis of fluoren-9-ones via palladium-catalyzed cyclocarbonylation of o-halobiaryls.

The synthesis of various substituted fluoren-9-ones has been accomplished by a novel palladium-catalyzed cyclocarbonylation of o-halobiaryls. The cyclocarbonylation of 4'-substituted-2-iodobiphenyls produces very high yields of 2-substituted fluoren-9-ones bearing either electron-donating or electron-withdrawing substituents. 3'-Substituted 2-iodobiphenyls afford in excellent yields with good regioselectivity 3-substituted fluoren-9-ones. This chemistry has been successfully extended to polycyclic and heterocyclic fluorenones.

Biphenyl Compounds↗
PubMedDate not supplied

Conformation of amine-modified DNA: 2-aminofluorene- and 2-(acetylamino)fluorene-modified deoxydinucleoside monophosphates with all possible nearest neighbors. A comparison of search and optimization methods.

Although a significant part of the replication fork exists as single-stranded DNA, little is known about the effect of carcinogens and mutagens on single-strand conformation. Large-scale conformational searches with potential energy minimization, using the torsion angle space molecular mechanics program DUPLEX, were employed to explore the conformation of all 16 deoxydinucleoside monophosphates bearing 2-aminofluorene (AF) or 2-(acetylamino)fluorene (AAF) modification on guanine. We have thus examined the effect of 3' versus 5' modification, the presence or absence of the acetyl group, and the effect of four different neighbors in each case. The principal effect of the acetyl group appeared to be the destabilization of anti (and, to a lesser degree, borderline anti) conformations for modified guanine. This mattered little in the 5'-substituted dimers, where one conformational type predominated in the low-energy structures for the adducts of both AAF and AF: It was right-handed, with syn-guanine, imperfect base-base stacking, and fluorene to 3'-sugar contacts. Greater divergence was seen in the 3'-substituted series. The AAF-substituted 3'-adducts primarily displayed good base-fluorene stacking, with syn-guanine in contact with the 5'-sugar. The AF-substituted 3'-adducts displayed a variety of structures which included base-base and carcinogen-base stacked forms. Two novel forms were encountered [global minima for d(ApG-AF) and d(GpG-AF)], whose unusual structures suggest mutagenic capability. In order to address the multiple minimum problem, we conducted our searches of conformation space using two alternative optimization methods that also employ differing search strategies. We used the Powell algorithm, BOTM, with starting conformations that are selected combinations of rotamers, and the method of simulated annealing (SA), with random or arbitrary starting conformations. While both approaches were effective in defining the most important structures, SA was more successful than BOTM in locating the structures of lowest energy.

2-Acetylaminofluorene↗
PubMed2004

Biotransformation of fluorene, diphenyl ether, dibenzo-p-dioxin and carbazole by Janibacter sp.

Fluorene, diphenyl ether, dibenzo-p-dioxin, and carbazole were used by a dibenzofuran-utilizing Janibacter sp. strain YY-1. Metabolites were identified by GC-MS. Angular dioxygenation was the major pathway for degradation of fluorene, diphenyl ether, and dibenzo-p-dioxin but not for carbazole. Lateral dioxygenation of all tested compounds was indicated by the detection of mono- or di-hydroxylated compounds. The bacterium also catalyzed the monooxygenation of fluorene at the C9 position.

Actinobacteria↗
PubMed1970

Effects of sex hormones on enzymic esterification of 2-(N-hydroxy-acetamido) fluorene by rat liver cytosol.

1. Enzymic esterifications of 2-(N-hydroxyacetamido)fluorene and several other hydroxamic acids by liver cytosol were studied. Determination of 2-acetamido-3-methylthiofluorene was used for the assay. 2. With rat liver cytosol, requirement for ATP, Mg(2+) and SO(4) (2-) suggested formation of phosphate and sulphate esters of 2-(N-hydroxyacetamido)fluorene. 3. Rats showed sex and age differences in their activity. Liver from adult male rat was at least twice as active as liver from adult female rat. No such sex differences were found in mice, hamsters and guinea pigs. 4. Administration of testosterone (300mug/day) subcutaneously for 8 days increased the activity in the female rat by 100%, whereas diethylstilboestrol (100mug/day) had no effect. In the male rat diethylstilboestrol treatment decreased the activity by 60%, whereas testosterone pretreatment was without any effect. 5. Among various endocrine ablations such as adrenalectomy, castration, adrenalectomy-castration and hypophysectomy in the adult male rat, hypophysectomy was found to be the most effective in decreasing the activity of the liver to about 50% of control values. 6. Like 2-(N-hydroxyacetamido)fluorene, various other N-hydroxy derivatives of 2-acetamido-7-fluorofluorene, 2-acetamidophenanthrene, 4-acetamidobiphenyl and 4-acetamidostilbene were also shown to be esterified to different extents by rat liver cytosol.

Adenosine Triphosphate↗
PubMed1993

Biotransformation of fluorene by the fungus Cunninghamella elegans.

The metabolism of fluorene, a tricyclic aromatic hydrocarbon, by Cunninghamella elegans ATCC 36112 was investigated. Approximately 69% of the [9-14C]fluorene added to cultures was metabolized within 120 h. The major ethyl acetate-soluble metabolites were 9-fluorenone (62%), 9-fluorenol, and 2-hydroxy-9-fluorenone (together, 7.0%). Similarly to bacteria, C. elegans oxidized fluorene at the C-9 position of the five-member ring to form an alcohol and the corresponding ketone. In addition, C. elegans produced the novel metabolite 2-hydroxy-9-fluorenone.

Biodegradation, Environmental↗
PubMed2004

Characterization of the upper pathway genes for fluorene metabolism in Terrabacter sp. strain DBF63.

Genes involved in the degradation of fluorene to phthalate were characterized in the fluorene degrader Terrabacter sp. strain DBF63. The initial attack on both fluorene and 9-fluorenone was catalyzed by DbfA to yield 9-fluorenol and 1,1a-dihydroxy-1-hydro-9-fluorenone, respectively. The FlnB protein exhibited activities against both 9-fluorenol and 1,1a-dihydroxy-1-hydro-9-fluorenone to produce 9-fluorenone and 2'-carboxy-2,3-dihydroxybiphenyl, respectively. FlnD is a heteromeric protein encoded by flnD1 and ORF16, being a member of the class III two-subunit extradiol dioxygenase. FlnE was identified as a serine hydrolase for the meta-cleavage products that yield phthalate.

Actinomycetales↗
PubMed2001

[Effect of cyclodextrins on fungal degradation of fluorene].

The purpose of this study was to improve the bioavailability of fluorene (PAH) by the use of complexing agents, cyclodextrins. The biodegradation tests were performed in liquid medium batches; fluorene was quantified by HPLC. Experimental results showed the enhancement of fluorene degradation by Penicillium italicum and Phanerochaete chrysosporium in the presence of branched cyclodextrins.

Biological Availability↗
PubMedDate not supplied

[Improvement of the process of fluorene degradation by Rhodococcus rhodochrous strain 172].

The ability of Rhodococcus rhodochrous strain 172 to consume fluorene as the sole source of carbon and energy in a liquid medium was successfully increased by an addition of polycapramide fiber to the medium and preliminary adaptation of cells on fluorene agar. A combination of these approaches allowed complete degradation of fluorene without an accumulation of intermediates.

Biodegradation, Environmental↗
PubMed2002

Synthesis of fluoren-9-ones by the palladium-catalyzed cyclocarbonylation of o-halobiaryls.

The synthesis of various substituted fluoren-9-ones has been accomplished by the palladium-catalyzed cyclocarbonylation of o-halobiaryls. The cyclocarbonylation of 4'-substituted 2-iodobiphenyls produces very high yields of 2-substituted fluoren-9-ones bearing either electron-donating or electron-withdrawing substituents. 3'-Substituted 2-iodobiphenyls afford 3-substituted fluoren-9-ones in excellent yields with good regioselectivity. This chemistry has been successfully extended to polycyclic fluorenones and fluorenones containing fused isoquinoline, indole, pyrrole, thiophene, benzothiophene, and benzofuran rings.

Journal Article↗
PubMed2003

Cascade radical cyclizations of benzannulated enyne-allenes. Unusual cleavage of a benzene ring leading to twisted 1,1'-dialkyl-9,9'-bifluorenylidenes and spiro[1H-cyclobut[a]indene-1,9'-[9H]fluorenes].

Treatment of the benzannulated enediynyl propargylic alcohol 16 (isomer ratio = 2:1) with thionyl chloride induced a sequence of reactions leading to the twisted 1,1'-dipropyl-9,9'-bifluorenylidene 17, the polycyclic compounds 18 and 19, and the spiro[1H-cyclobut[a]indene-1,9'-[9H]fluorene] 20 (trans/cis = 5:1). The transformation from 16 to the unexpected 17 presumably involved an initial formation of the benzannulated enyne-allene 21 followed by a C(2)-C(6) cyclization reaction and an intramolecular radical-radical coupling reaction, giving rise to the formal Diels-Alder adduct 23. Repeat of this sequence then furnished 24. Cleavage of the bond connecting the two carbons having the propyl substituent afforded 25. A subsequent rotation of the carbon-carbon bond joining the two central five-membered rings then gave the trans isomer 26. Oxidation of 26, presumably by oxygen, followed by hydrolysis then produced 17. Interestingly, the pathway leading to 17 involved an unusual cleavage of a benzene ring. The X-ray crystal structure of 17 reveals that it has a twist angle of 45.2 degrees for the carbon-carbon double bond connecting the two bifluorenylidene fragments. The spiro[1H-cyclobut[a]indene-1,9'-[9H]fluorene] 20 apparently was produced via two intramolecular [2 + 2] cycloaddition reactions of the benzannulated enyne-allene moieties, generated in situ from the benzannulated enediynyl propargylic alcohols. The twisted 1,1'-dimethyl-9,9'-bifluorenylidene 33 and the spiro[1H-cyclobut[a]indene-1,9'-[9H]fluorene] 39 (trans/cis = 3:1) were likewise produced from 32 and 38, respectively.

Journal Article↗
PubMed2000

Synthesis of new two-photon absorbing fluorene derivatives via Cu-mediated Ullmann condensations

The Ullmann amination reaction was utilized to provide access to a number of fluorene analogues from common intermediates, via facile functionalization at positions 2, 7, and 9 of the fluorene ring. Through variation of amine or iodofluorene derivative, analogues bearing substitutents with varying electron-donating and electron-withdrawing ability, e.g., diphenylamino, bis-(4-methoxyphenyl)amine, nitro, and benzothiazole, were synthesized in good yield. The novel fluorene derivatives were fully characterized, including absorption and emission spectra. Didecylation at the 9-position afforded remarkably soluble derivatives. Target compounds 4, 5, and 9 are potentially useful as fluorophores in two-photon fluorescence microscopy. Their UV-vis spectra display desirable absorption in the range of interest suitable for two-photon excitation by near-IR femtosecond lasers. Preliminary measurements of two-photon absorption indicate the derivatives exhibit high two-photon absorptivity, affirming their potential as two-photon fluorophores. For example, using a 1,210 nm femtosecond pump beam, diphenylaminobenzothiazolylfluorene 4 exhibited nondegenerate two-photon absorption, with two-photon absorptivity (delta) of ca. 820 x 10(-50) cm(4) s photon(-1) molecule(-1) at the femtosecond white light continuum probe wavelength of 615 nm.

Journal Article↗
PubMed2006

Phase behavior of poly(9,9-di-n-hexyl-2,7-fluorene).

Here we report the phase behavior of poly(9,9-di-n-hexyl-2,7-fluorene) (PFH), which previously received little attention as compared to its homologues poly(9,9-di-n-octyl-2,7-fluorene) (PFO) and poly(9,9-di-(2'-ethylhexyl)-2,7-fluorene) (PFEH). By means of differential scanning calorimetry, X-ray diffraction, and electron microscopy, we show that there exist four different phases in PFH. The as-cast film is mainly composed of a mesomorphic beta phase with layer spacing of ca. 1.4 nm. This beta phase is inherently metastable and, upon heating above 175 degrees C, transforms into a crystalline (alpha) form that melts into a nematic (N) liquid above 250 degrees C. Upon stepwise cooling, the nematic melt crystallizes into the alpha phase first, followed by solid-solid transformation into another crystalline (alpha') form. Unit cell structure of the alpha form is monoclinic whereas that of the alpha' form is triclinic, but departures from strict orthogonality are slight (by ca. 6 degrees). These observations not only support our previous assignment of two crystalline forms (both orthorhombic in structure) in PFO but also provide insights to the crystalline nature of the polyfluorene series.

Journal Article↗
PubMed2006

Probing charge transport in pi-stacked fluorene-based systems.

The molecular parameters governing charge transport along a pi-stacked fluorene chain in poly(dibenzofulvene) are studied by a joint experimental and theoretical approach involving high-resolution gas-phase photoelectron spectroscopy and quantum-mechanical methods. We specifically investigate the electronic couplings between fluorene moieties as well as the intramolecular reorganization energies, for both holes and electrons. Our results indicate that a pi-stacked fluorene chain favors hole transport over electron transport. The values for electronic couplings and reorganization energies estimated here are compared with those derived recently for pentacene.

Journal Article↗
PubMed1970

Reactive phosphate ester of the carcinogen 2-(N-hydroxy)acetamido-fluorene.

1. Reaction of 2-(N-acetoxy)-acetamidofluorene with orthophosphate buffer at pH7 yielded a large quantity of water-soluble fluorene derivatives, which showed absorption peaks at 303, 290 and 280nm. Tris buffer under similar conditions gave negligible reaction. 2. Hydrolysis of polar material with acid or alkaline phosphatases liberated equimolar amounts of inorganic phosphate and an ether-extractable fluorene derivative. On the basis of its u.v. spectrum, R(F) values after paper chromatography, solubility in alkali and colour with spray reagents, the derivative was characterized tentatively as 2-acetamido-5-hydroxyfluorene. 3. Polar material also contained a reactive fluorene derivative which gave characteristic reaction products with methionine and guanosine. The reactive derivative was characterized as a phosphate ester of 2-(N-hydroxy)-acetamidofluorene. 4. It is suggested that such reactive phosphate esters may also be some of the ultimate carcinogenic metabolites of carcinogenic aromatic hydroxamic acids.

Carcinogens↗
PubMed1986

2-(N-acetoxy-N-acetylamino)fluorene mutagenesis in mammalian cells: sequence-specific hot spot.

Mutations induced by 2-(N-acetoxy-N-acetylamino)fluorene were studied using temperature-sensitive simian virus 40 (SV40) mutants as probe in monkey kidney cells. In vitro treatment of the SV40 virions with 2-(N-acetoxy-N-acetylamino)fluorene increased mutagenesis and decreased survival in the viral progeny. A lethal hit of approximately 85 acetylaminofluorene adducts per SV40 genome was calculated. UV irradiation of cells prior to infection did not modify the results. Molecular analysis of independent SV40 revertants showed that 2-(N-acetoxy-N-acetylamino)fluorene induces base substitutions that are located not opposite putative acetylaminofluorene adducts but next to them. Moreover, a hot spot of mutation restoring a true wild-type genotype was observed in 10 of the 16 revertants analyzed. This hot spot, not targeted opposite a major DNA lesion, was not observed using UV light as damaging agent in the same genetic assay. Two models involving the stabilization, by acetylaminofluorene adducts, of the secondary structure of a specific quasipalindromic SV40 sequence are proposed to explain this sequence-specific hot spot.

2-Acetylaminofluorene↗