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PubMed2001

Electroytic partial fluorination of organic compounds. 52. Regio- and diastereoselective anodic fluorination of thiazolidines.

Anodic fluorination of N-benzoyl, N-acethyl-, and N-formylthiazolidine derived from L-cysteine was carried out in dimethoxyethane (DME) and acetonitrile containing various supporting fluoride salts using an undivided cell. Highly regioselective fluorination proceeded to provide the corresponding 5-monofluorinated thiazolidine derivatives in good yields in DME, and the diastereoselectivitiy was moderate to high regardless of the supporting fluoride salts. The diastereoselectivitiy of the fluorination was greatly affected by the bulkyness of the subsitituent on the nitrogen atom, and N-benzoylthiazolidine gave much higher diastereoselectivity compared with N-formyl derivative. The fluorination of the thiazolidines was not achieved by commercially available fluorinating reagents such as N-fluoropyridinium salts.

Electrochemistry↗

PubMed1999

Electrolytic Partial Fluorination of Organic Compounds. 31.(1) Regioselective Anodic Fluorination of 2-Quinolyl and 4-(7-Trifluoromethyl)quinolyl Sulfides and the Factors Affecting Its Optimization.

Electrochemical fluorination of 2-quinolyl and 4-(7-trifluoromethyl)quinolyl sulfides bearing an electron-withdrawing group at the position alpha to the sulfur atom was studied. Fluorination was successfully carried out using Et(4)NF.nHF (n = 3, 4) and Et(3)N.3HF as a supporting electrolyte and a fluoride ion source in dimethoxyethane in a divided cell to provide the corresponding alpha-fluorinated sulfides in good yields. A trifluoromethyl group positioned on the quinoline ring significantly enhanced anodic alpha-fluorination. 4-(Methylthio)-7-(trifluoromethyl)quinoline was also found to undergo anodic fluorination efficiently. Solvent effects of various donor numbers were also established.

Journal Article↗

PubMed1983

Noninvasive observations of fluorinated anesthetics in rabbit brain by fluorine-19 nuclear magnetic resonance.

Fluorinated anesthetics were observed noninvasively in the brain of intact rabbits with fluorine-19 nuclear magnetic resonance spectroscopy. High-resolution fluorine-19 spectra of halothane, methoxyflurane, and isoflurane were obtained with a surface coil centered over the calvarium. Elimination of halothane from the brain was also monitored by this technique. Residual fluorine-19 signals from halothane (or a metabolite) could be detected as long as 98 hours after termination of anesthesia. These observations demonstrate the feasibility of using this technique to study the fate of fluorinated anesthetics in live mammals.

Animals↗

PubMed1983

Fluorine magnetic resonance studies of fluorine-substituted benzoyl chymotrypsins.

The fluorine magnetic resonance spectra of 4-fluorobenzoyl and 3,5-di(trifluoromethyl)benzoyl-alpha-chymotrypsins and the corresponding methyl esters were determined. An unusually large downfield displacement of the chemical shift (-10 ppm) was observed for the 4-fluorobenzoyl-alpha-chymotrypsin compared to the free acid in water. The shift of the ethyl ester was displaced upfield on going from a partly aqueous solvent to dioxane or methanol. The line broadening of the fluorine resonance of the 3,5-di(trifluoromethyl)benzoyl-alpha-chymotrypsin was minimal and there was no evidence of two peaks in the spectrum. The resonance was displaced only slightly downfield from the corresponding acid in water. Unusual chemical shifts for fluorinated acylchymotrypsins have been reported for other acyl groups and they appear to be unrelated to the anomalous deacylation rates observed for some fluorine substituted acylenzymes.

Binding Sites↗

PubMed2003

Determination of fluorinated surfactants and their metabolites in sewage sludge samples by liquid chromatography with mass spectrometry and tandem mass spectrometry after pressurised liquid extraction and separation on fluorine-modified reversed-phase sorbents.

An analytical method was elaborated for simultaneous extraction and determination of fluorinated anionic and non-ionic surfactants in sewage sludge. Surfactant compounds were determined by liquid chromatography-mass spectrometry (LC-MS) after Soxhlet extraction, hot steam extraction and pressurised liquid extraction (PLE) using spiked sludge samples. PLE in a multiple-step procedure consisting of sequential use of ethyl acetate-dimethylformamide and methanol-phosphoric acid resulted in the most efficient extraction procedure. Quantitative analyses of the fluorinated anionic perfluorooctanesulfonate (PFOS) and the partly fluorinated non-ionic alkylpolyglycol ether (FAEO) surfactants were performed by selected ion monitoring LC-MS. Electrospray ionisation or atmospheric pressure chemical ionisation in negative or positive mode was performed. Recoveries between 105 and 120% could be reached. No PFOS and non-ionic FAEO surfactants in concentrations higher than 6 or 10 mg kg(-1) dry matter were observed in real environmental samples. Therefore aerobic and anaerobic biodegradation was performed to investigate the fate of fluorinated surfactants reaching wastewaters. Biological wastewater treatment in laboratory scale under aerobic or anaerobic conditions led to an elimination by biodegradation.

Chromatography, Gas↗

PubMedDate not supplied

Fluorine-fluorine spin-spin coupling constants in aromatic compounds: correlations with the delocalization index and with the internuclear separation.

This paper describes a new empirical approach for the evaluation of fluorine-fluorine spin-spin coupling constants (J(FF)) in aromatic compounds. The correlations between J(FF) and the delocalization index calculated within the framework of the theory of atoms in molecules (AIM) and with the fluorine-fluorine internuclear separation are investigated. Both the internuclear separation and the delocalization index are found to be highly correlated with J(FF). A regression model in which the experimental J(FF) coupling constant is fitted exponentially to the internuclear separation and linearly to the delocalization index yields a squared correlation coefficient as high as 0.96 for a data set consisting of 33 coupling constants spread over a range of 85 Hz.

Fluorine↗

PubMed2002

The beta-fluorine effect. Electronic versus steric effects in radical deoxygenations of fluorine-containing pentofuranose nucleosides.

Stereoselective pyramidalization of free radicals by a vicinal fluorine substituent, the beta-fluorine effect, was invoked to rationalize a 77:23 anti/syn ratio of 2-deuterio-1-fluorocyclopentanes obtained by radical reduction of trans-2-fluoro-1-bromocyclopentane with tributyltin deuteride (Dolbier, W. R., Jr.; Bartberger, M. D. J. Org. Chem. 1995, 60, 4984-4985). We have evaluated analogous reductions of the four possible stereoisomers of some adenine 2'(3')-fluoro-3'(2')-O-phenoxythiocarbonyl nucleoside derivatives. In all cases, the steric effect of adenine on the beta face directs deuterium transfer from the stannane to C2'(C3') on the alpha face of the furanose ring. However, the beta-fluorine effect enhances ratios of deuterium transfer anti to the vicinal fluorine substituent.

Adenine↗

PubMed2004

CYP 17 and CYP 19 inhibitors. Evaluation of fluorine effects on the inhibiting activity of regioselectively fluorinated 1-(Naphthalen-2-ylmethyl)imidazoles.

Regioselectively fluorinated 1-(naphth-2-ylmethyl)imidazoles 1a-h have been synthesized starting from the corresponding (naphth-2-yl)methanols (2). 2a-d have been obtained by LiAlH4-promoted reduction of fluorinated 1-methyl-2-naphthaldehydes. The latter were easily prepared in fairly good overall yields by ceric ammonium nitrate (CAN)-promoted oxidative addition of the suitable 3-(fluoroaryl)-1-trimethylsilyloxy-1-butenes to ethyl vinyl ether in methanol followed by cyclization of the resulting acetals in strongly acidic medium in the presence of DDQ. 2e-h were prepared by LiAlH4-promoted reduction of the corresponding fluorinated methyl 2-naphthoates. The latter were more profitably obtained by reacting the suitable benzyl bromide with the sodium salt of dimethyl 2-(2,2-dimethoxyethyl)malonate in DMF followed by demethoxycarbonylation and acid catalysed cyclization of the resulting acetals. Compared with the nonfluorinated parent compounds 1i-1, fluorinated 1-(naphth-2-yl)methylimidazoles 1a-h turned out to be potent inhibitors of CYP17 and CYP19 enzymes. The most active inhibitor of CYP17 is 1c, whereas CYP19 is strongly inhibited by 1b, 1e, and 1g. Interestingly, 1g is a potent dual inhibitor also being very active towards CYP19.

Aromatase↗

PubMed1992

Fluorine-18-labeled androgens: radiochemical synthesis and tissue distribution studies on six fluorine-substituted androgens, potential imaging agents for prostatic cancer.

We have synthesized six androgens labeled with 18F as potential imaging agents for prostatic cancer. These include 16 beta-fluorine-substituted testosterone, dihydrotestosterone and mibolerone, 16 alpha- and 16 beta-fluorine substituted 7 alpha-methyl-19-nortestosterone, and 20-fluoro-R1881 (metribolone). All of the radiochemical preparations proceeded in satisfactory yield, giving material with adequately high effective specific activity for the in vivo studies. In the tissue distribution studies in diethylstilbestrol-treated male rats, high selective uptake by the prostate was observed that ranged from 0.39% to 1.21% injected dose (ID)/g at 1 hr and 0.20 to 0.47 at 4 hr, with prostate-to-blood and prostate-to-muscle ratios ranging from 3.28 to 9.45, respectively, at 1 hr and 4.06 to 35.0, respectively, at 4 hr. Those compounds that are likely to be metabolized rapidly showed lower prostate uptake but higher uptake selectivity at 4 hr; at earlier times, uptake selectivities were more comparable. Compounds with a 16 beta-fluorine substituent showed extensive metabolic defluorination, resulting in ca. 50% of the dose being deposited in bone at 4 hr. This is consistent with a 16 alpha-hydroxylation process that may proceed rapidly with these compounds, but would be retarded by a 17 alpha-methylation, blocked by inversion of stereochemistry at C-16, and would not affect fluorine at the C-20 position. These fluoroandrogens, together with 20-fluoromibolerone described previously, are the first positron-emitting androgens to show high affinity and selective uptake by androgen target tissues in vivo, and they may be useful as in vivo prostate imaging agents in man.

Animals↗

PubMed2005

How good is fluorine as a hydrogen-bond acceptor in fluorinated single-walled carbon nanotubes?

Ab initio (RI-MP2/TZVPP) computations were employed to investigate the interaction between hydrogen-bond donors H2O and CH3OH and covalently bound fluorine in organofluorine compounds. While the CFHO interaction energy is around 3 kcal mol(-1) for unstrained systems, the linear correlation between pyramidalization angle at the carbon atom and the interaction energy suggests that increased binding can be obtained in strained systems. This is confirmed for the dihydrodifluoropyrene-methanol pair, but a large portion of the binding energy is due to the interaction of the pi system with the oxygen atom. Density functional periodic boundary condition computations (PBC-PBE/6-31G*) of the structures of (5,5) and (10,10) armchair (C2F)n fluorinated SWNTs (F-SWNTs) indicate that the pyramidalization at the fluorine-binding carbon atoms are too similar to that of CH3F to enhance the hydrogen-bond acceptor properties of fluorine significantly. The solubility of F-SWNTs in alcohols therefore could be due to a combination of hydrogen bonds and van der Waals interactions with the pi systems.

Journal Article↗

PubMed2005

Self-assembly of heteroleptic [Cu(dipyrrinato)(hfacac)] complexes directed by fluorine-fluorine interactions.

Heteroleptic copper(II) complexes were synthesized from three different meso-substituted pyridyl- and quinoline-dipyrrinato ligands (3-pyrdpm, 3-quindpm, and 4-quindpm). Metal complexes were prepared with both acetylacetonate (acac) and hexafluoroacetylactonate (hfacac) ancillary ligands. The complexes undergo a self-complementary self-assembly process upon crystallization to generate a range of solid-state topologies including one-dimensional coordination polymers and discrete hexameric rings. The self-assembly of these molecular aggregates is driven by metal-ligand bonding, but is also modulated by fluorine-fluorine interactions. Perfluorination of the spectator ligand tends to generate more compact structures, which is attributed to aggregation of the perfluoromethyl groups. The results presented here demonstrate that fluorine-fluorine contacts can be used to modulate supramolecular structures in the solid state.

Journal Article↗

PubMed2002

Electrophilic fluorinating reagent mediated synthesis of fluorinated alpha-keto Ethers, benzil, and 6,6'-dialkoxy-2,2'-bipyridines.

Interactions of various fluorinated and nonfluorinated alcohols with trans-stilbene in the presence of electrophilic reagents were studied. Under neat conditions, reactions of trans-stilbene (1) with fluorinated alcohols, R(f)OH (R(f) = CF3CH2-, CFH2CH2-, CF3CF2CH2-, CF2H(CF2)3CH2-, (CF3)2CH-, (CF3)3C- (2a-f) in the presence of an electrophilic reagent, 1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor) or N,N-difluoro-2,2'-bipyridinium bis(tetrafluoroborate) (MEC-31), gave alpha-keto ethers (3a-f) and benzil (4) in good to moderate yields. alpha-Keto ether and benzil formation was very much dependent on the reaction time, the degree of fluorination of the alcohols, and whether a solvent such as CH3CN, DMF or DMA was utilized. In solution, alpha-keto ethers and benzil did not form. Interestingly, under neat conditions, nonfluorinated alcohols, ROH (R = CH3-, CH3CH2-, CH3CH2CH2-, CH3CH2CH2CH2-, CH3CH2CH2CH2CH2CH2-) (5g-k) did not react with trans-stilbene in the presence of MEC-31 but gave 6,6'-dialkoxy-2,2'-bipyridines (6g-k), regioselectively, in excellent isolated yields. On the other hand, fluorinated alcohols did not react with MEC-31. Reaction of MEC-31 with an excess of diethylene glycol (7) gave the bipyridine derivative (8) in 88% isolated yield. Reaction of 8 either with diethylaminosulfur trifluoride (DAST) or bis(2-methoxyethyl)aminosulfur trifluoride (Deoxofluor) readily produced the corresponding difluoro derivative (9) in 85% isolated yield. All new compounds have been characterized by spectroscopic and elemental analysis.

Journal Article↗

PubMed2004

Electrolytic partial fluorination of organic compounds.71. Highly diastereoselective anodic fluorination of sulfides having oxygen-containing heterocyclic groups.

Diastereoselective anodic fluorination of sulfides having various oxygen-containing heterocyclic substituents such as 2-furanyl, 1,3-dioxolanyl, 2,2-dimethyl-1,3-dioxolanyl, 2-spirocyclohexyl-1,3-dioxolanyl, 2-spiroadamantyl-1,3-dixolanyl, and 1,3-dioxolanonyl groups at the beta-position was comparatively studied. Among the oxygen-containing heterocyclic substituents, the 2-spirocyclohexyl-1,3-dioxolanyl group gave the best diastereoselectivity (80% de). The diastereoselectivity was also affected by supporting fluoride salts and solvents. Chemical fluorination using selectfluor resulted in much lower diastereoselectivity and extremely poor yield. The fluorinated products were readily converted into the corresponding fluorinated diol in good yields by acidic hydrolysis.

Journal Article↗

PubMed2004

Photochemistry of fluorinated heterocyclic compounds. An expedient route for the synthesis of fluorinated 1,3,4-oxadiazoles and 1,2,4-triazoles.

The photochemistry of some 3-N-alkylamino-5-perfluoroalkyl-1,2,4-oxadiazoles in the presence of nitrogen nucleophiles such as ammonia and primary and secondary aliphatic amines has been investigated. The primary photolytic intermediate from the cleavage of the ring O-N bond follows two distinct and competing pathways leading to (i). 5-perfluoroalkyl-1,3,4-oxadiazoles, through the ring contraction-ring expansion photoisomerization route favored by the presence of the base or (ii). 5-perfluoroalkyl-1,2,4-triazoles, through the intervention, as an internal nucleophile, of the exocyclic N-alkylamino moiety of the oxadiazole followed by the attack of the external nitrogen nucleophile and subsequent heterocyclization. Some comments on the photoreactivity of fluorinated oxadiazoles and on the applications of these photoprocesses in the synthesis of target fluorinated structures are emphasized. In this context, irradiations of 3-perfluoroalkanoylamino-4-phenylfurazan in the presence of primary aliphatic amines are reconsidered as feasible one-pot synthetic methodologies toward fluorinated heterocycles. X-ray analysis of two representative products 1-methyl-3-methylamino-5-perfluoroheptyl-1,2,4-triazole and 2-methylamino-5-trifluoromethyl-1,3,4-oxadiazole confirmed the proposed structures and furnished interesting information on the crystal packing of these fluorinated five-membered heterocycles.

Journal Article↗

PubMed1994

[Effects of high iodine and high fluorine on children's intelligence and the metabolism of iodine and fluorine].

An investigation on children's intelligence and the metabolism of iodine and fluorine in high iodine and fluorine regions was carried out. The results were as follows. In high iodine and high fluorine areas, the thyroid enlargement prevalence rate among inhabitants and that among children were 3.8% and 29.8%, respectively. The dental fluorosis prevalence rate among inhabitants and that among children was 35.48% and 72.9%, respectively. The pupils' average intelligence quotient (IQ) was 76.67 +/- 7.75, slightly lower than the control point, but that of low intelligent pupils was 16.7%. The urinary iodine and urinary fluoride were 816.25 +/- 1.80 micrograms/L and 2.08 +/- 1.03 mg/L, respectively, markedly higher than the control point. The thyroid iodine-131 (131I) uptake rate was markedly lower than the control point. The values at 3 h and 24 h were 9.36 +/- 1.55% and 9.26 +/- 4.63%, respectively. The serum TSH was obviously higher than the control point. These results indicate that high iodine and high fluorine exert severe damage to human body.

Adolescent↗

PubMed2005

Fluorine-19 or phosphorus-31 NMR spectroscopy: a suitable analytical technique for quantitative in vitro metabolic studies of fluorinated or phosphorylated drugs.

Fluorine-19 or phosphorus-31 NMR (19F NMR or 31P NMR) spectroscopy provides a highly specific tool for identification of fluorine- or phosphorus-containing drugs and their metabolites in biological media as well as a suitable analytical technique for their absolute quantification. This article focuses on the application of in vitro 19F or 31P NMR to the quantitative metabolic studies of some fluoropyrimidine or oxazaphosphorine drugs in clinical use. The first part presents an overview of the advantages (non-destructive and non-selective direct quantitative study of the biological matrices) and limitations (expensive cost of the spectrometers, limited mass or concentration sensitivity) of NMR spectroscopy. The second part deals with the criteria to be considered for successful quantification by NMR (uniform excitation over the entire spectral width of the spectrum, resonance signals properly characterised by taking into account T1 values and avoiding NOE enhancements, optimisation of the data processing, choice of a suitable standard reference). The third and fourth parts report some examples of quantification of 5-fluorouracil, its prodrug capecitabine, 5-fluorocytosine and their metabolites in bulk solutions (biofluids, tissue extracts, perfusates and culture media) and heterogeneous media (excised tissues and packed intact cells) as well as cyclophosphamide and ifosfamide in biofluids. These two parts emphasise the high potential of in vitro 19F or 31P NMR for absolute quantification, in a single run, of all the fluorine- or phosphorus-containing species in the matrices analysed. The limit of quantification in bulk solutions is 1-3 microM for 19F NMR and approximately 10 microM for 31P NMR. In heterogeneous media analysed with 19F NMR, it is 2-5 nmol in excised tissues and cell pellets.

Animals↗

PubMed1977

Fluorine-18-labeled diethylaminosulfur trifluoride (DAST): an F-for-OH fluorinating agent.

A new fluorinating agent was developed by incorporation of 18F into diethylaminosulfur trifluoride (DAST), a reagent capable of replacing hydroxyl and carbonyl oxygen with fluorine. The DAST was synthesized using sulfur tetrafluoride and trimethylsilyldiethylamine in a freon-11 solvent at -78 degrees C and purified by reduced-pressure distillation. Labeling was then accomplished by exchange with anhydrous 18F-hydrofluoric acid, which caused more than 80% of the available activity to be incorporated into the DAST. Fluorine-18-labeled methyl fluoride, ethyl fluoride, and 2-fluoroethanol were prepared from methanol, ethanol, and ethylene glycol, with yields of 20%, 25%, and 12%, respectively.

Ethanol↗

PubMed1986

Fluorinated psychopharmacological agents: noninvasive observation by fluorine-19 nuclear magnetic resonance.

Fluorinated psychopharmacological agents were measured with fluorine-19 nuclear magnetic resonance spectroscopy in the brain of intact rats that had been treated with fluphenazine. These in vivo experiments were compared to in vitro measurements of fluphenazine-treated rats. A high-field shift was observed in both in vivo and in vitro measurements. On the basis of the in vitro measurements, fluphenazine concentration in the brains of treated rats was estimated. Our observations demonstrate the feasibility of this technique for determining fluorinated neuroleptics in live mammals.

Animals↗