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PubMed1993

Radiation damage of fluorinated organic compounds measured by parallel electron energy loss spectroscopy.

The sensitivity of fluorinated organic compounds to radiation damage in the electron microscope was measured by electron energy loss spectroscopy (EELS). Five classes of molecules were investigated with fluorine atoms situated on: (1) an aliphatic chain, (2) an aromatic ring, (3) a trifluoromethyl group on an aromatic ring, (4) a trifluoromethyl group on a heterocyclic ring, and (5) a trifluoromethyl group next to a carbonyl group. The damage dose for fluorine loss was found to depend strongly on the position of the fluorine atoms and on specimen temperature. For poly-substituted fluorine on an aliphatic chain, approximately half of the fluorine was retained at doses in excess of 10(7) e/nm2. At room temperature molecules containing trifluoromethyl groups on aromatic or heterocyclic rings were much more sensitive to fluorine loss than compounds having fluorine substituted directly on the rings. This behavior is consistent with the relatively low chemical stability of the trifluoromethyl group in these structures. The rapid loss of fluorine at low electron doses (approximately 10(4) e/nm2) in the trifluoromethyl aromatic compounds was reduced several orders of magnitude by cooling the specimen to liquid-nitrogen temperatures. An understanding of how specific types of fluorinated compounds suffer damage under the electron beam will be important in their potential application as biochemical or pharmacological probes.

Hydrocarbons, Fluorinated↗
PubMed1986

Stimulation of cAMP accumulation in rat aorta and diaphragm by fluorine containing compounds.

Evidence is presented that accumulation of cAMP in isolated rat thoracic aorta and diaphragm is stimulated by several fluorine containing compounds (NaF, Na2PO3F (MFP) and SnF2). Time course experiments with NaF showed that maximal stimulation of cAMP accumulation was observed within 2.5 min. NaF and MFP produced significant increases in cAMP accumulation at concentrations of 0.1 microM and SnF2 produced a significant increase at 0.01 microM. The sensitivity of these tissues to the fluorine compounds is similar to that previously reported (Curro and Mickunas, 1981) for the inhibition of norepinephrine induced contractions by fluorine compounds in isolated thoracic aorta.

Animals↗
PubMed2005

Fluorinated heterocyclic compounds. An effective strategy for the synthesis of fluorinated Z-oximes of 3-perfluoroalkyl-6-phenyl-2h-1,2,4-triazin-5-ones via a ring-enlargement reaction of 3-benzoyl-5-perfluoroalkyl-1,2,4-oxadiazoles and hydrazine.

The reaction of 3-benzoyl-5-perfluoroalkyl-1,2,4-oxadiazoles with hydrazine has been investigated, evidencing the possibility of competitive reaction paths. Nucleophilic addition of the hydrazine to the electrophilic C(5) of the 1,2,4-oxadiazole ring, followed by ring opening and ring closure with enlargement, leads with high yield and in very mild experimental conditions to the formation of Z-oximes of 3-perfluoroalkyl-6-phenyl-2H-1,2,4-triazin-5-ones (11a-c) as major products of the reaction. In turn, the hydrazine can attack the electrophilic carbonyl carbon giving 4-perfluoroacylamino-5-phenyl-2H-1,2,3-triazoles (13a-c) through the well-known Boulton-Katritzky rearrangement of the intermediate hydrazones.

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↗
PubMed2004

Fluorinated organic compounds in an eastern Arctic marine food web.

An eastern Arctic marine food web was analyzed for perfluorooctanesulfonate (PFOS, C8F17SO3-), perfluorooctanoate (PFOA, C7F15COO-), perfluorooctane sulfonamide (PFOSA, C8F17SO2NH2), and N-ethylperfluorooctane sulfonamide (N-EtPFOSA, C8F17SO2NHCH2CH3) to examine the extent of bioaccumulation. PFOS was detected in all species analyzed, and mean concentrations ranged from 0.28 +/- 0.09 ng/g (arithmetic mean +/- 1 standard error, wet wt, whole body) in clams (Mya truncata) to 20.2 +/- 3.9 ng/g (wet wt, liver) in glaucous gulls (Larus hyperboreus). PFOA was detected in approximately 40% of the samples analyzed at concentrations generally smaller than those found for PFOS; the greatest concentrations were observed in zooplankton (2.6 +/- 0.3 ng/g, wet wt). N-EtPFOSA was detected in all species except redfish with mean concentrations ranging from 0.39 +/- 0.07 ng/g (wet wt) in mixed zooplankton to 92.8 +/- 41.9 ng/g (wet wt) in Arctic cod (Boreogadus saida). This is the first report of N-EtPFOSA in Arctic biota. PFOSA was only detected in livers of beluga (Delphinapterus leucas) (20.9 +/- 7.9 ng/g, wet wt) and narwhal (Monodon monoceros) (6.2 +/- 2.3 ng/g, wet wt), suggesting that N-EtPFOSA and other PFOSA-type precursors are likely present but are being biotransformed to PFOSA. A positive linear relationship was found between PFOS concentrations (wet wt) and trophic level (TL), based on delta15N values, (r2 = 0.51, p < 0.0001) resulting in a trophic magnification factor of 3.1. TL-corrected biomagnification factor estimates for PFOS ranged from 0.4 to 9. Both results indicate that PFOS biomagnifies in the Arctic marine food web when liver concentrations of PFOS are used for seabirds and marine mammals. However, transformation of N-EtPFOSA and PFOSA and potential other perfluorinated compounds to PFOS may contribute to PFOS levels in marine mammals and may inflate estimated biomagnification values. None of the other fluorinated compounds (N-EtPFOSA, PFOSA, and PFOA) were found to have a significant relationship with TL, but BMF(TL) values of these compounds were often >1, suggesting potential for these compounds to biomagnify. The presence of perfluorinated compounds in seabirds and mammals provides evidence that trophic transfer is an important exposure route of these chemicals to Arctic biota.

Animals↗
PubMed1996

[Concentration and distribution of fluorine in hen's eggs as an aspect of selected biological parameters].

The actual paper presents the method and results of studies concerning the content and decomposition of fluorine compounds in the component structures of eggs and in the bone system of a domestic hen, as well as its progeny under conditions of increased content of these compounds in the drinking water. The objective of the paper has been: 1) determining the effect of environmental contamination (NaF in drinking water) exerted on the presence of fluorine in eggs, 2) defining the distribution of fluorine in component structures of the egg, 3) studying the fluorine effect on selected physical parameters of eggs, 4) determination of fluorine content in tibial bones of laying hens, after receiving NaF in drinking water, and to compare the tibial bone composition in hens and their progeny with control groups, 5) analyzing the share of fluorine compounds in the construction of skeleton and beaks of chicks. The conceptions of the work were elaborated on the basis of results stemming from an accomplished experimental breeding of domestic hens in a semi-intensive system. The experiment proceeded 4 weeks. A part of eggs obtained by breeding was designed for hatching. Due to the requirements associated with analyzing the skeleton, all the experimental birds, including the chicks, were assigned for further analyses. The material, obtained in this way, (bones of hens, chicks, eggs) was subsequently subjected to detailed studies. According to the conceptions of the paper the selected physical parameters of eggs were studied, therein resistance tests, using specialized apparatuses. Fluoride was determined potentiometrically, by applying fluoride ion selective electrode, while the metallic elements by aid of atomic spectrophotometer (Tab. 1-5, Fig. 1). Finally, the following conclusions were presented, namely: 1. The egg shell in hens plays an essential role in binding fluorine compounds and constitutes one of the means of their fast elimination from the organism. 2. Egg shells may provide an easily accessible bioindicator for the exposure of birds to fluorine compound, particularly with regard to a given species. 3. Moderately increased fluorine content in the shells of eggs fails to influence their thickness and does not cause any changes in their resistance to decay. 4. In conditions of increased exposure of hens to fluorine compounds, no elevation in the accumulation of this element was disclosed in the substance, which is evidence that there is a lack of apparent influence of local contamination by emissions of fluorine compounds exerted on nutritional usefulness of eggs. 5. Comparison of fluorine content in the bones of chicks, stemming from hens being given water with NaF to drink, with control hens points to a significant rise in fluoride accumulation in progeny of hens, exposed to sodium fluoride action. That may have a negative influence on their correct development.

Animals↗
PubMed2000

[New methods of constructing fluorinated organic compounds and their application].

This review summarizes several effective synthetic methods of fluorinated organic compounds developed by our group. Two topics have been described in this review. The first topic describes novel fluorinations using diethylaminosulfur trifluoride (DAST). The treatment of tertiary cyclopropyl silyl ethers with DAST caused ring opening and produced allylic fluorides. The reaction of DAST with a tertiary cyclobutanol provided a fluorocyclobutane, a (fluoromethyl)cyclopropane or a homoallylic fluoride. DAST reacted with cyclic ketoximes bearing substituent(s) that can stabilize a carbocation to cause the fluorinative fragmentation which produces fluorinated carbonitrile. The second topic describes the novel syntheses of organic compounds containing the difluoromethylene moiety using fluorinated building blocks. The indium-mediated coupling of aldehydes with 3-bromo-3,3-difluoropropene gives alpha,alpha-difluorohomoallylic alcohols in high yields. alpha,alpha-Difluorohomopropargylic alcohols were also obtained from the indium-mediated coupling of aldehydes with alpha-bromo-alpha,alpha-difluoropropargyl compounds. In the presence of a palladium(0) catalyst, several nucleophiles regioselectively reacted with 3-bromo-3,3-difluoropropene at its gamma-position, and reacted with 1-substituted-3-bromo-3,3-difluoropropenes at their alpha-position. (+)-(R)-1-Amino-2,2-difluorocyclopropane-1-carboxylic acid was synthesized via the lipase-catalyzed asymmetric acetylation of a pro-chiral diol as a key step.

Chemistry, Organic↗
PubMed1996

Measurement of intratumor pH by pH indicator used in 19F-magnetic resonance spectroscopy. Measurement of extracellular pH decrease caused by hyperthermia combined with hydralazine.

RATIONALE AND OBJECTIVES: Without affect of metabolic changes, the authors measured intratumor pH by using 19F-magnetic resonance spectroscopy (MRS) with a fluorine compound (ZK-150471) on the basis of a calibration curve by pH electrode. METHODS: Using the 4.7-tesla magnetic resonance apparatus, a fluorine compound that had acid-base equilibrial change and was impermeable within cell membranes was used. The fluorine compound was injected intravenously. The signal was obtained from mouse mammary cancer by creating an experimental tumor on the leg of mice. And the tumors, which were heated with and without hydralazine. The pH evaluated from chemical shift of the fluorine compound. The pH data was obtained from an electrode for reference. RESULTS: The pH of nontreated tumors (n = 25) were 6.94 + 0.091. The pH decreased to 6.772 + 0.169 at 20 minutes even after 20 minutes of heating, and decreased to < 6.71 at 40 minutes after every heating time. The pH decreased to 6.456 at 20 minutes after 15 minutes of heating combined with hydralazine, and to 6.416 at 40 minutes after same treatment. CONCLUSIONS: It is possible to measure the extracellular pH by 19F-MRS with the fluorine compound noninvasively in vivo, even after heating.

Animals↗
PubMed2004

A 19F NMR study of fluorobenzoate biodegradation by Sphingomonas sp. HB-1.

While several microorganisms readily degrade 2- and 4-fluorobenzoates, only a very small number appear to catabolise the 3-fluoro isomer, owing to the accumulation of toxic intermediates. Here we describe the isolation of a bacterium capable of using 3-fluorobenzoate as a sole source of carbon and energy, and the experiments conducted to define the steps involved in the biodegradation of this compound. The organism was identified as a strain belonging to the genus Sphingomonas by sequence analysis of its 16S rRNA gene. To date no other organism from this genus is known to degrade this compound. Using fluorine nuclear magnetic resonance spectroscopy (19F NMR) to analyse the culture supernatant it was possible to observe the disappearance of 3-fluorobenzoate and the appearance of fluoride ion and four other fluorinated compounds. These were identified as 3-fluorocatechol, 2-fluoromuconic acid and 3- and 5-fluoro-1,2-dihydro-1,2-dihydroxybenzoates. Thus, the likely catabolic pathway involves dioxygenation of 3-fluorobenzoate yielding fluorocatechol and subsequent intra-diol cleavage to yield fluoromuconic acid. The organism can also use 2- and 4-fluorobenzoates as growth substrates.

Benzoates↗
PubMed2004

Fluorine in medicinal chemistry.

Fluorinated compounds are synthesized in pharmaceutical research on a routine basis and many marketed compounds contain fluorine. The present review summarizes some of the most frequently employed strategies for using fluorine substituents in medicinal chemistry. Quite often, fluorine is introduced to improve the metabolic stability by blocking metabolically labile sites. However, fluorine can also be used to modulate the physicochemical properties, such as lipophilicity or basicity. It may exert a substantial effect on the conformation of a molecule. Increasingly, fluorine is used to enhance the binding affinity to the target protein. Recent 3D-structure determinations of protein complexes with bound fluorinated ligands have led to an improved understanding of the nonbonding protein-ligand interactions that involve fluorine.

Fluorine↗
PubMed2002

Trivalent lanthanide compounds with fluorinated thiolate ligands: Ln-F dative interactions vary with Ln and solvent.

The fluorinated tris-thiolate compounds Ln(SC(6)F(5))(3) can be isolated as THF, pyridine, or DME coordination complexes. In THF, the larger Ce forms dimeric [(THF)(3)Ce(SC(6)F(5))(3)](2) (1) with bridging thiolate ligands, while the smaller lanthanides (Ln = Ho (2), Er (3)) form monometallic (THF)(3)Ln(SC(6)F(5))(3) compounds. There is a tendency for fluoride to coordinate to Ln throughout the lanthanide series (Ce-Er). The cerium compound 1 contains a pair of bridging thiolates connecting two eight-coordinate Ce(III) ions. Of the two terminal thiolates, only one exhibits a distinct Ce-F bond. In contrast, the Ho derivative (THF)(3)Ho(SC(6)F(5))(3) is a molecular compound in the solid state, with two monodentate thiolates and one thiolate that again coordinates through both S and F atoms. Incorporation of a stronger Lewis base reduces but does not necessarily eliminate the tendency to form Ln-F bonds. Structural characterization of the eight-coordinate (pyridine)(4)Sm(SC(6)F(5))(3) (4) reveals a single, clearly defined Ln-F interaction, while in (pyridine)(4)Yb(SC(6)F(5))(3) (5) there are no Yb-F bonds. In the structure of (DME)(2)Er(SC(6)F(5))(3) (6) the DME ligands completely displace F from the Er coordination sphere.

Journal Article↗
PubMed1994

[Health effects of fluorine and its compounds].

Fluoride, the ionic form of fluorine, is a natural component of the biosphere and 13th most abundant element in the crust of the earth. It is, therefore, found in a wide range of concentrations in virtually all inanimate and living things. Many trace elements perform a definite function in human metabolism and the question of the value of fluoride, always found in the body, has been raised. Much evidence suggesting that the inclusion of fluoride in drinking water has beneficial as well as adverse effects on human health was obtained. Either alone or in combination with calcium and/or vitamin D, it is used in high daily doses for the treatment of osteoporosis. Although organic fluorine compounds are used in medicine and commerce, the inorganic fluorine compounds are of greater importance toxicologically because they are more readily available. The major pathway of fluoride elimination from the human body is via the kidney. When renal function deteriorates, the ability to excrete fluoride markedly decreases, possibly resulting in greater retention of fluoride in the body. At this point, more research is needed to evaluate the effects of physiological variables on the fluoride metabolism in humans.

Fluorides↗
PubMed1999

[Fluorinated organic compounds: synthesis and biological applications].

Since the discovery of molecular fluorine by Henri Moissan, fluorinated products have found numerous biological applications. Fluorine substitution can have profound effects on the properties of organic compounds. The very high electronegativity of this small substituent can modify electron distribution in the molecule, affecting its absorption, distribution and metabolism. Fluorination and 18F labeling methods are briefly described. Some examples of enzymatic inhibition by fluorinated products are examined. Nowadays, fluorine-containing medicinals are featuring significantly in such diverse areas as the provision of anti-cancer and anti-inflammatory agents, antibiotics and general anesthetics, anti-parasitic and central nervous system agents, and in cardiac therapy. Fluorocarbon emulsions show promise as blood substitutes. Several medical diagnostic techniques, such as positron emission tomography and the use of X-ray contrast agents, have profited from the use of fluorinated substances.

Animals↗
PubMed2002

[Use of acid enamel biopsy in examinations of enamel mineral content of permanent human teeth with reference to age and environmental conditions].

Human activity during the last decades has led to changes in the circulation of fluorine and other elements in the natural environment. Due to their narrow safety margin, environmental levels of fluorine compounds require careful monitoring. Studies on contamination with fluorine of the natural environment in Szczecin and its surroundings have a long history. Until recently, maximal allowable concentrations of this element in air, water and soil have substantially been exceeded. Markers reflecting adverse effects of fluorine on living organisms and man, among them magnesium deficit, continued to raise concern. The aim of this work was to apply a modified method for enamel sampling, the acid enamel biopsy, to determine the content of fluorine and magnesium in superficial layers of enamel of permanent teeth in 14-year-old children and adults residing in Szczecin or Białystok--two cities differing as to level of contamination of the environment with fluorine compounds. Correlations between age and content of fluorine and magnesium in superficial layers of permanent teeth were studied as well. Altogether, 40 premolars extracted for orthodontic reasons in children and for periodontologic or prosthetic reasons in adults were sampled and the mineral content in three superficial layers of enamel on the buccal surface was determined. Fluorine concentrations were measured with gas chromatography, while calcium and magnesium concentrations were determined with atomic absorption spectrometry. The mineral content was studied before and after removal of calcium fluorine deposits from the surface and pores of the premolars. In addition, the thickness and mass of each layer was calculated (Tables 1 and 2). To sample the layers, perchloric acid was applied three times to the same site and the depth of dissolution after each application was measured (Table 3). Total fluorine, structural fluorine and calcium fluorine content was measured in each layer (Table 4). Magnesium content was determined before and after removal of calcium fluorine deposits (Table 5). The highest content of fluorine and magnesium was found in the outermost layer of enamel (Figs. 1-4). The content decreased with depth demonstrating a logarithmic relationship. The following conclusions were drawn: 1. Increased content of fluorine in the natural environment is associated with accumulation of this element in superficial layers of the enamel of permanent teeth in the form of structural fluorine. This process takes place in children and adults alike. 2. The content of fluorine in enamel decreases with depth, irrespective of age and contamination level of the environment. 3. Increased content of fluorine in enamel of adults, as compared with children, appears to be caused by deposits of calcium fluorine. This process takes places independently of environmental contamination with fluorine. 4. A deficit of magnesium in the enamel was found in children residing in fluorine-contaminated areas. In adults, magnesium content was not related to the place of residence, suggesting a lack of effect of fluorine contamination of the content of magnesium in the enamel. 5. The content of magnesium in superficial layers of the enamel decreases with depth following a logarithmic curve. This finding was independent of the level of contamination with fluorine or age.

Adolescent↗
PubMed1993

Direct observation of a fluorinated anticonvulsant in brain tissue using 19F-NMR techniques.

A fluorinated derivative of an anticonvulsant gamma-butyrolactone [alpha-(1,1-difluoroethyl)-alpha-methyl-gamma-butyrolactone; alpha-DFGBL] was synthesized as a probe for NMR spectroscopic observation of the drug in brain tissue. The fluorinated compound is an efficacious anticonvulsant in mice, and inhibits the specific binding of [35S]t-butylbicyclophosphorothionate ([35S]TBPS) to mouse brain membranes with a concentration dependence similar to that of the non-fluorinated compound alpha-ethyl-alpha-methyl-gamma-butyrolactone. Quantitative 19F-NMR spectroscopic studies, coupled with chromatographic measurements of drug tissue concentration, showed that virtually all of the alpha-DFGBL in brain was NMR-observable and that, following intraperitoneal injection, alpha-DFGBL rapidly achieved millimolar concentrations in brain. The 19F-NMR spectra of a alpha-DFGBL in brain and liver tissue were broad (1-2 ppm) and complex, exhibiting multiple chemical shift features. The major chemical shift features in these spectra were assigned on the basis of differential extraction and comparison of 19F spin-spin relaxation times (T2s) and 19F chemical shifts of alpha-DFGBL in tissue to those in pure solvents. The major feature at 10.4 ppm in the tissue spectra was assigned to a weakly polar, membrane-associated environment for the fluorinated compound, while the feature at 11.2 ppm was assigned to an aqueous environment for alpha-DFGBL. The drug was in slow exchange between these two environments in brain. In addition, the feature at lowest field (9.7-9.8 ppm) was identified as a water-soluble hydroxy-acid metabolite of alpha-DFGBL produced by the liver. These data indicate that gamma-butyrolactone anticonvulsants achieve high concentrations in brain, where they exist in several, largely membrane-associated, environments. These findings are consistent with the purported action of the gamma-butyrolactones as low-affinity modulators of gamma-aminobutyric acid-A channels.

4-Butyrolactone↗