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PubMed1995

[Alkyl derivatives of benzene, indene, naphthalene, diphenyl and fluorene as a potential source of occupational and environmental exposure].

Mixtures of organic solvents are used extensively in industry. The aim of this study was to develop a method for the determination of components of commercial multi-component solvent mixtures, and to perform qualitative and quantitative analyses of the mixtures. Farbasol, Solvesso and Shellsol mixtures were analysed by gas chromatography with a mass spectrometry detector (GC/MS). The composition of mixtures was determined using the mass spectrum computer analysis. Fractions of alkyl benzene, naphthalene and diphenyl derivatives were isolated. The proportions of the individual fractions in the mixtures differed. A predominant fraction was present in each mixture. Solvents (trimethylbenzene, tetramethylbenzene, ethyltoluene, diethylbenzene, isopropylotoulene) which significantly increase health risk due to their suspected neurotoxicity, were identified in each mixture.

Benzene Derivatives↗
PubMedDate not supplied

Neoglycopeptide synthesis and purification in multi-gram scale: preparation of O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-N alpha-fluoren-9-yl-methoxycarbonyl-hydroxyproline and its use in the pilot-scale synthesis of the potent analgesic glycopeptide O1.5-beta-D-galactopyranosyl [DMet2, Hyp5]enkephalinamide.

The preparation of a beta-galactosylated hydroxyproline derivative and its use in the multi-gram solid-phase synthesis of the potent analgesic neoglycopeptide O1.5-beta-D-galactopyranosyl [D-Met2, Hyp5]enkephalinamide is described in this paper. The most closely related impurities have been identified, isolated and characterized. Significant aspects of the synthesis and purification affecting yields and purity of both the building block and the target neoglycopeptide are discussed.

Analgesics, Opioid↗
PubMed2006

Tunable fluorene-based dynamers through constitutional dynamic chemistry.

Dynamic covalent iminofluorene-based oligomers and polymers have been generated. They undergo constitutional recomposition under the effect of two parameters, acidity and ZnII metal ions. As a result, marked changes in physical properties take place. The results illustrate the response of such a dynamic system to chemical effectors (H+ nd ZnII), thus demonstrating the adaptive behavior of the system under the pressure of external factors. They also point to the possibility of modulating optical properties (UV-visible absorption and fluorescence) by constitutional recomposition in response to a specific trigger. Such features allow the development of dynamic materials, the functional properties of which may respond to external stimuli.

Journal Article↗
PubMed2006

Spontaneous resolution of 2,3-bis-fluoren-9-ylidenesuccinic acid induced by achiral guest inclusion.

The racemic title host compound (1) formed homochiral inclusion crystals (conglomerate) of 1 with acetone, while heterochiral inclusion crystals (racemate) were obtained when complexed with ethyl acetate. Upon treatment of the homochiral inclusion crystals of 1 with gaseous acetyl chloride in the solid state, optically active 2,3-bis(fluorenylidene)succinic anhydride (3) was obtained in high optical purity.

Journal Article↗
PubMed1983

Enzymatic methylation of chicken erythrocyte DNA modified by two carcinogens, 2-(N-acetoxyacetylamino) fluorene and methylnitrosourea.

Both DNA-AAF and MNU-alkylated DNA are methylated less than nonmodified DNA by rat brain nuclei cytosine 5-methyltransferase purified either by chromatography on DEAE cellulose or by Dyematrex. The inhibition of methylation is proportional to the modification of the DNA, and DNA having a given percentage of bases modified with MNU is less methylated than DNA modified to the same extent with AAF. Moreover, DNA-AAF irreversibly inhibits the methylation of native DNA, whereas MNU-alkylated DNA does not inhibit the methylation of native DNA. The AAF-substituted DNA has a higher affinity for the enzyme than native DNA. However, this is probably not due to the AAF-induced local destabilization of the DNA helix, since heat-denatured DNA shows a lower affinity for the enzyme than double-stranded DNA. Addition of DNA-AAF to the enzyme preincubated with native DNA inhibits methylation, but only after a lag period. This agrees with the model in which the methylase walks along the strand to methylate cytosine residues before being detached from the DNA. AAF bound to guanine residues may block the movement of the enzyme along the helix. The in vitro hypomethylation of DNA, caused by carcinogens, could explain the in vivo observations made by several authors and could have significance in gene activity, cellular differentiation, and oncogenesis.

2-Acetylaminofluorene↗
PubMed1982

Non-random binding of N-acetoxy-N-2-acetylamino-fluorene to chromatin subunits as visualized by immunoelectron microscopy.

The influence of chromatin structure on the accessibility of DNA to the model ultimate carcinogen N-acetoxy-N-2-acetylaminofluorene (N-Aco-AAF) was investigated by means of an immunoelectron microscopic technique developed recently. An homogeneous population of core particles or trinucleosomes from chicken erythrocytes, was submitted to electrophilic attack by N-Aco-AAF. After DNA isolation, N-2-acetylaminofluorene (AAF) binding sites were mapped upon the DNA fragments using specific antibodies as a probe. Our results indicate a non-random binding of AAF along the DNA. Our data support the results of previous studies showing a preferential binding on the linker region.

2-Acetylaminofluorene↗
PubMed1980

New 9-stubstituted 3-N,O-diacetylhydroxylaminofluorenes: enhanced electrophilicity and mutagenicity. Derivatives of fluorene. 38.

The compound 2-acetamidofluorene is a potent hepatocarcinogen; its N-acetoxy derivative (2-NOAc-AAF), a model ultimate form of the carcinogen, is strongly mutagenic and is chemically reactive with nucleophiles. The isomeric 3-acetamidofluorene is a mammary carcinogen, but is not hepatocarinogenic; its N-acetoxy derivative (3-NOAc-AAF) is not reactive with nucleophiles. Derivatives of 3-NOAc-AAF containing electron-donating groups in positions conjugated with the 3-position have been synthesized. These show increased electrophilicity and mutagenicity. Thus, by electronic manipulation of the leaving-group capacity of the -OAc group of 3-NOAc-AAF, we have obtained compounds with increased biological activity, as well as increased chemical reactivity. Future experiments could show whether in vivo effects of these derivatives of 3-NOAc-AAF are more like the effects of 2-NOAc-AAF or of 3-NOAc-AAF.

2-Acetylaminofluorene↗
PubMed2004

[Action mechanism of anticonvulsant and anti-immobility (forced swim) effects of 3', 4'-dihydro-N, N-dimethylspiro-[9H-fluorene-9, 2' (5'H) furane]-3'-methanamine (AE37F)].

AE37F, a new aminotetrahydrofuranic derivative, exhibited, at 10-30 mg/Kg (po) or 1-10 mg/Kg (ip), antagonism of tonic convulsions, induced by pentetrazole (130 mg/Kg, ip), and of forced swin immobility, in mice. At these doses AE37F induced a considerable (100-250%) increase of serotonin (5-HT) and its main metabolite, 5-hydroxyindolacetic acid (5-HIAA), in the rat nucleus reticularis pontis oralis (NRPO), antagonized by amantadine, which also increased 5-HT and 5-HIAA levels in the NRPO. It is suggested: a) that the anti-immobility effect of AE37F is related to its antimuscarinic properties, b) that the rate of 5-HT release in the NRPO, calculated here by a new approach (from the 5-HT and 5-HIAA brain levels) is increased by AE37F and decreased by amantadine, in the NRPO, c) that the anti-convulsant action, observed with AE37F, could be related to a NMDA-sigma mediated stimulation of serotoninergic, GABAergic and glycinergic brain neurones, antagonized by the NMDA-sigma inhibition induced by amantadine.

Amantadine↗
PubMed2002

Characterization of an insoluble poly(9,9-diphenyl-2,7-fluorene) by solvent-free sample preparation for MALDI-TOF mass spectrometry.

The application of solvent-free sample preparation for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) allowed the characterization of an insoluble fraction of poly(9,9-diphenylfluorene) that was previously hindered by the lack of suitable characterization methods. The MALDI mass spectrometric analysis gives valuable mechanistic information about the heterogeneous polymerization process of the insoluble high molecular weight fraction of the polymer. The fragmentation appearing even under moderate desorption and ionization conditions of this rigid backbone analyte is identified as a multiple loss of the bulky phenyl side groups and can be avoided by applying the new MALDI matrix 7,7,8,8-tetracyanoquinodimethane. A specialized fragmentation study by postsource decay MALDI-TOF MS reveals a molecular weight dependent change in fragmentation mechanism from an exclusive cleavage of side groups from long polymer chains to an additional cleavage of the polymer backbone of short polymer chains.

Journal Article↗
PubMed2000

Electron acceptors of the fluorene series. 10.(1) novel acceptors containing butylsulfanyl, butylsulfinyl, and butylsulfonyl substituents: synthesis, cyclic voltammetry, charge-transfer complexation with anthracene in solution, and X-ray crystal structures of two tetrathiafulvalene complexes

2,4,5,7-Tetranitro-9-fluorenone (1b) reacts readily with n-butanethiol in dipolar aprotic solvents with selective substitution of nitro groups by butylsulfanyl groups in positions 2 and 7 (2, 3); the 2,5-isomer 4 was formed only as a minor product (<1%). Condensation of fluorenones 2-4 with malononitrile yielded 9-dicyanomethylene derivatives 5-7, which showed strong intramolecular charge transfer (lambda approximately 510-560 nm) and were found to sensitize the photoconductivity of carbazole-containing polymer films. Oxidation of sulfides 2-4 gave sulfoxide 8 or sulfones 9-11, which then were converted into their corresponding dicyanomethylene derivatives 12-15. All these novel acceptors showed three reversible single-electron reduction waves (cyclic voltammetry) yielding radical anion, dianion, and radical trianion; moreover, acceptors 13-15 showed also a fourth reduction wave, representing reversible tetraanion formation. Substitution of the oxygen of the carbonyl group in the fluorenones by a dicyanomethylene group increased the thermodynamic stability (K(SEM) growth) of the radical anion; K(SEM) ranged from 3 x 10(5) to 3 x 10(9) M(-1). CV measurements characterize compounds 3, 4 (EA = 1. 86-1.89 eV) as poor acceptors, 2, 6-11 (EA = 2.13-2.31 eV) as moderate acceptors, and 5, 12-15 (EA = 2.53-2.66 eV) as strong electron acceptors. Charge-transfer complex (CTC) formation between acceptors 9, 10, 13, 14, and anthracene as a donor was monitored by the appearance of additional low-energy bands in the visible region (CTC bands) of their electron absorption spectra. Increasing the EA of the acceptors from 9-fluorenones to the corresponding 9-dicyanomethylenefluorenes increases the complexation constants K(CTC) by 2.5-3 times, while sulfonyl substituents present substantial steric hindrance for complexation (as compared to the nitro group), decreasing K(CTC) values. Two CTCs for acceptors 14 and 17 with tetrathiafulvalene (TTF) were obtained, and their structures were solved by single-crystal X-ray diffractometry, giving the stoichometries 14:TTF, 2:3, and 17:TTF:PhCl, 1:1:0.5. In the former complex the packing motif is a mixed.DDAD'A. stack; in the latter complex the D and A moieties form unusually close CT pairs, which pack in a herringbone motif.

Journal Article↗
PubMed2006

Synthesis and functional properties of end-dendronized oligo(9,9-diphenyl)fluorenes.

[structure: see text] A facile approach for the synthesis of a family of dendrimers OFn-EG with hole-transporting ability moieties by copper-catalyzed Buchwald's double-amination as a key reaction has been developed. These novel dendrimers exhibit good energy transfer efficiencies and very high thermal and electrochemical stabilities and have potential applications as hole transfer and emitting layers in the field of organic emitting diodes (OLEDs) or as host materials for electrophosphorescent applications.

Journal Article↗
PubMed2006

Highly luminescent network films from electrochemical deposition of peripheral carbazole functionalized fluorene oligomer and their applications for light-emitting diodes.

Highly luminescent network films on flat indium tin oxide (ITO) substrates are prepared by electropolymerization using an electroactive and fluorescent compound as precursor; the LEDs prepared using these films as a light emitting layer achieve the maximum luminance and external quantum efficiency of 4224 cd/m(2) and 0.72%, respectively, which demonstrates that electrochemical synthesis can be a new route to construct the highly luminescent films.

Journal Article↗
PubMed2005

Wire-like charge transport at near constant bridge energy through fluorene oligomers.

The study of photoinitiated electron transfer in donor-bridge-acceptor molecules has helped elucidate the distance dependence of electron transfer rates and behavior of various electron transfer mechanisms. In all reported cases, the energies of the bridge electronic states involved in the electron transfer change dramatically as the length of the bridge is varied. We report here, in contrast, an instance in which the length of the bridge, and therefore the distance over which the electron is transferred, can be varied without significantly changing the energies of the relevant bridge states. A series of donor-bridge-acceptor molecules having phenothiazine (PTZ) donors, 2,7-oligofluorene (FL(n)) bridges, and perylene-3,4:9,10-bis(dicarboximide) (PDI) acceptors was studied. Photoexcitation of PDI to its lowest excited singlet state results in oxidation of PTZ via the FL(n) bridge. In toluene, the rate constants for both charge separation and recombination as well as the energy levels of the relevant FL(n)(+.) bridge states for n = 1-4 are only weakly distance dependent. After the initial photo-generation of (1)(PTZ(+.)-FL(n)-PDI(-.)), radical pair intersystem crossing results in formation of (3)(PTZ(+.)-FL(n)-PDI(-.)) that recombines to give (3.)PDI. The dependence of the (3.)PDI yield on an applied magnetic field shows a resonance, which gives the singlet-triplet splitting, 2J, of the radical ion pair. The magnitude of 2J directly monitors the contribution of coherent charge transfer (superexchange) to the overall electron transfer rate. These data show that charge recombination through FL(n) is dominated by incoherent hopping at long distances.

Electron Transport↗