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PubMed2004

29/28, 30/28Silicon, 34/32sulfur and 80/77selenium isotope-induced fluorine chemical shifts through two bonds.

Isotope effects on fluorine chemical shifts induced by heteroatoms bonded covalently to a carbon atom bearing fluorine atoms were studied. For each compound, the isotope-induced chemical shifts 2delta19F(X) through two bonds were measured for the heteroatom (X = 29/28Si, 30/28Si, 34/32S and 80/77Se). The 1delta19F(13/12C) values for the carbon bonded to the fluorine atoms were also recorded. Examination of the 19F NMR data showed homogeneity of the isotope-induced chemical shifts along the rows of the periodic table and regularity down the columns (from 10 to 15 ppb per mass unit for the second row to 0.4 ppb for the fourth row). It became negligible for atoms of the fifth row.

Journal Article↗
PubMed2002

Structural concept for fluorinated Y-enynes with solvatochromic properties.

An approach to the development of fluorescent probes to follow polymerizations in situ using fluorinated cross-conjugated enediynes (Y-enynes) is reported. Different substitution patterns in the Y-enynes result in distinct solvatochromic behavior. beta,beta-Bis(phenylethynyl)pentafluorostyrene 7, which bears no donor substituents and only fluorine at the styrene moiety, shows no solvatochromism. Donor substituted beta,beta-bis(3,4,5-trimethoxyphenylethynyl)pentafluorostyrene 8 and beta,beta-bis(4-butyl-2,3,5,6-tetrafluorophenylethynyl)-3,4,5-trimethoxystyrene 9 exhibit solvatochromism upon change of solvent polarity. Y-enyne 8 showed the largest solvatochromic shift (94 nm bathochromic shift) upon changing solvent from cyclohexane to acetonitrile. A smaller solvatochromic response (44 nm bathochromic shift) was observed for 9. Lippert-Mataga treatment of 8 and 9 yields slopes of -10,800 and -6,400 cm(-1), respectively. This corresponds to a change in dipole moment of 9.6 and 6.9 D, respectively. The solvatochromic behavior in 8 and 9 supports the formation of an intramolecular charge transfer (ICT) state. The low fluorescence quantum yields are caused by competitive double bond rotation. The fluorescence decay time of 9 decreases in methyltetrahydrofuran from 2.1 ns at 77 K to 0.11 ns at 200 K. Efficient single bond rotation in 9 was frozen at -50 degrees C in a configuration in which the trimethoxyphenyl ring is perpendicular to the fluorinated rings. 7-9 are photostable compounds. The X-ray structure of 7 shows it is not planar and that its conjugation is distorted. Y-enyne 7 stacks in the solid state showing coulombic, actetylene-arene, and fluorine-pi interactions.

Journal Article↗
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↗
PubMed1998

Iodinated and fluorinated steroid 2'-aryl-[3,2-c] pyrazoles as potential glucocorticoid receptor imaging agents.

We have synthesized several halogenated steroids as potential glucocorticoid receptor mediated imaging agents. These compounds are analogs of aryl-pyrazolo steroids, similar to the potent glucocorticoid, cortivazol. Compounds containing the halogens, iodine, bromine, and fluorine, as well as the E- and Z-iodovinyl side chain at the para position of 2'-phenyl-11 beta,17,21-trihydroxy-16 alpha-methyl-20-oxo-pregn-4-eno[3,2-c] pyrazole were prepared. They were tested as ligands for the glucocorticoid receptor by competition for the binding of [3H]dexamethasone and for glucocorticoid potency by the induction of alkaline phosphatase in HeLa cells. None of the iodinated steroids were good ligands for the glucocorticoid receptor or potent glucocorticoids. The bromo analog was only slightly better than the iodinated steroids as a ligand, and it had a potency in the HeLa cell assay about half that of dexamethasone. The fluoro analog good binding to the glucocorticoid receptor and was a very potent glucocorticoid, approximately seven times that of dexamethasone. Consequently, it appears that the fluoro steroid, 2'-(4-fluorophenyl)-11 beta,17,21-trihydroxy-16 alpha-methyl-20-oxo-pregn-4-eno[3,2-c] pyrazole, when labeled with 18F, would make an excellent glucocorticoid receptor-mediated imaging agent for positron emission tomography.

Animals↗
PubMed1993

Synthesis and in vivo distribution in the rat of several fluorine-18 labeled 5-hydroxy-2-aminotetralin derivatives.

A method is described for the rapid production and purification of new potential dopamine agonists. Via thermal heating (refluxing in an oil bath) and microwave exposure 2-[N-n-3-fluoropropyl-N-(4-methylphenyl)ethylamino]-5-hydroxyte tralin (12), 2-[N-n-3-fluoropropyl-N-(4-fluorophenyl)ethylamino]-5-hydroxyte tralin (13), and their isotopic fluorine-18 derivatives were synthesized, respectively. The fluorine-18 label was introduced via N-fluoroalkylation with no-carrier-added (n.c.a.) 18FCH2CH2CH2I. In 115 min, radiochemical yields of 11% (corrected for decay) were achieved for both compounds. The specific activity ranged from 15-75 GBq/mumol. After i.v. injection in rats, the fluorine-18 labeled compounds were evaluated for their in vivo binding to the D2-receptors. The radioactivity levels in the striatum, nucleus accumbens and tuberculum olfactorius were not significantly higher than in the cerebellum and frontal cortex at 15, 30 and 60 min after administration of the tetralin derivatives. Dopamine depletion with reserpine did not affect the uptake in the dopamine D2-receptor rich area. Remarkable high uptakes were found in the adrenal for both compounds.

Animals↗
PubMed2000

[Anti-carcinogenic structural modification by fluorine-substitution in aza-polycyclic aromatic hydrocarbons].

One of the major goals of a series of our studies is to explore the availability of a method for anti-genotoxic modification of carcinogens by fluorine-substitution. Quinoline, a hepatocarcinogen, mutates bacterial tester strains in the presence of rat liver microsomal enzymes and induces GST-P (placental glutathione S-transferase)-positive foci in a medium-term bioassay system for hepatocarcinogenesis. On the other hand, 3-fluorinated quinoline (3-FQ) was neither mutagenic nor carcinogenic in the same assay system, whereas 5-fluoroquinoline (5-FQ) was mutagenic and carcinogenic. Quinoline, 3-FQ, and 5-FQ were also tested in an in vivo mutagenicity assay system using a lacZ-transgenic mouse (Muta Mouse). Mutation was induced by quinoline and 5-FQ only in the liver, the target organ of carcinogenesis by quinoline, but not in the other organs examined. 3-FQ was non-mutagenic in all of the organs. The results strongly indicate that fluorine-substitution at the position-3 of quinoline could be an anti-genotoxic structural modification of quinoline in a wide range of its genotoxic end-points. Additionally, seventeen mono- and di-fluorinated derivatives of 1,7-phenanthroline, 1,10-phenanthroline, benzo[h]quinoline, and benzo[f]quinoline were subjected to analysis of their structure-mutagenicity relationship. The results support that the enamine epoxide structure of the pyridine moiety, as well as the bay-region epoxide structure, is responsible for mutagenicity. These results suggest that the introduction of a fluorine atom to the molecule in question may be a useful tool to modify their mutagenic potency and to better understand the mechanism of mutation.

Animals↗
PubMed2006

Characterisation of fluorine containing glasses by 19F, 27Al, 29Si and 31P MAS-NMR spectroscopy.

OBJECTIVE: The aim of this study is to characterise a range of model and commercially available glasses used to form glass (ionomer) polyalkenoate cements. METHODS: A range of model fluoro-alumino-silicate glasses that form the basis of glass (ionomer) polyalkenoate cements and five commercial glasses have been characterised by 29Si, 27Al, 31P and 19F Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR). RESULTS: The 29Si spectra indicate a predominantly Q33Al and Q44Al structure where the Q33Al species represents a silicon with one non-bridging oxygen and three Si-O-Al linkages and the Q44Al species a silicon with four Si-O-Al bonds. Aluminium was found in predominantly four coordinate sites, but glasses with high fluorine contents showed an increasing proportion of five and six coordinate aluminium. In phosphate containing glasses the phosphorus was present as Al-O-PO3(2-) type species indicating local charge compensation of Al3+ and P5+ in the glass structure. 19F MAS-NMR indicated the presence of F-Ca(n), Al-F-Ca(n), F-Sr(n), Al-F-Sr(n) and Al-F-Na(n) species where F-M(n) indicates a fluorine surrounded by n next nearest neighbour cations and Al-F-M(n) represents a fluorine bonded to aluminium with the metal, M in close proximity charge balancing the tetrahedral AlO3F species. The proportion of Al-F-M(n) species increased with increasing fluorine content of the glass and lower non-bridging oxygen contents. There was no evidence of Si-F bonds in any of the glasses. CONCLUSIONS: The local structure of the phosphate containing glasses with regard to fluorine, calcium, strontium and phosphate is similar to that of fluorapatite the mineral phase of tooth. This may explain the ease with which these glasses crystallize to fluorapatites and the recently observed mineralization of glass polyalkenoate cements found in vivo.

Aluminum↗
PubMed1988

Cyclotrons and radiopharmaceuticals in positron emission tomography. Council on Scientific Affairs. Report of the Positron Emission Tomography Panel.

Positron emission tomography (PET) can probe biochemical pathways in vivo and can provide quantitative data; for that purpose, tracers labeled with positron-emitting radioisotopes are essential. This report describes the tracers that are being used or that may have future use, their production by cyclotrons, and other needed resources for PET imaging. Current routine and automated methods for convenient production of labeled compounds, coupled with simple computer-controlled accelerators, can support the creation of clinical PET centers in any large medical institution, obviating the need for in-depth research teams. An alternate approach involves the development of regional centers that provide in-house service and that supply fluorine 18- and carbon 11-labeled compounds to nearby hospitals with PET machines.

Brain↗
PubMed1996

[Occupational hygiene in production and use of multicomponent metal compounds].

The article deals with results obtained in hygienic evaluation of production and application of new monocrystalline compounds based on cesium, sodium, iodine, lead, scandium, fluorine. The evaluation covered work conditions and health state of those engaged into production of monocrystalline compounds, revealed the main occupational hazards. The experiments determined fundamental toxicometric parameters, studied characteristics of general toxic and specific effects induced by lead fluoride and cesium iodine. The results formed basis for sanitary measures, establishment of MACs for 4 monocrystalline compounds in the air of workplace.

Adult↗
PubMed1979

[Solubility and absorption of magnesium fluoride in the intestinal tract].

The solubility rate of various substances was determined via solubility experiments using magnesium fluoride on various specific surfaces. This rate controls the resorption of fluorine ions from MgF2 during its passage through the intestinal tract. The solubility rate for MgF2, as for other hard-to-dissolve substances, is proportional to the specific surface and the mass of the substance. In light of this information, resorption tests with magnesium fluoride showed that this compound is "biodisposable". The amount of fluorine which will be resorbed from MgF2 can be estimated.

Adult↗
PubMed1990

Modulation of the picrotoxin receptor by fluorinated ethyl, methyl-butyrolactones.

A number of investigators have shown that gamma-butyrolactones bind to the picrotoxin site on the gamma-aminobutyric acid (GABA) receptor. We examined the effects of three fluorinated gamma-butyrolactone derivatives on GABA currents and synaptic currents in cultured hippocampal neurons. alpha-(2,2,2-trifluoroethyl)-alpha-methyl-gamma-butyrolactone was a partial picrotoxin agonist, meaning that like picrotoxin, it blocked GABA currents, but not completely. This action is in marked contrast to that of its parent compound, alpha-ethyl-alpha-methyl-gamma-butyrolactone, which is a mixed inverse agonist/antagonist, enhancing GABA currents at low GABA concentration (less than or equal to 1 microM) and antagonizing picrotoxin block of GABA currents at higher GABA concentrations (approximately 30 microM). The properties of two difluorinated derivatives were found to be very different from the trifluorinated compound. Both alpha-(1,1-difluoroethyl)-alpha-methyl-gamma-butyrolactone and alpha-(1,1-difluoroethyl)-alpha-methyl-gamma-thiobutyrolactone+ ++ dramatically increased the current produced by low concentrations of GABA. The former had less marked inverse agonist effects at higher GABA concentrations but behaved instead like a picrotoxin antagonist. In addition, alpha-(1,1-difluoroethyl)-alpha-methyl-gamma-butyrolactone reduced both excitatory and inhibitory synaptic currents suggesting a separate effect on presynaptic transmitter release through an unknown mechanism. These experiments support the hypothesis that gamma-butyrolactones can have a variety of effects at the picrotoxin receptor and indicate that specific properties of these compounds can be altered drastically by fluorination.

4-Butyrolactone↗
PubMed1999

Dimethacrylate monomers with varied fluorine contents and distributions.

OBJECTIVES: There are many unique properties associated with fluorinated polymers that make these materials attractive for use in the challenging oral environment. This study was devised to better define the influence of fluorine content and its structural distribution on properties of fluorinated resins and composites, especially with regard to their water-related and mechanical properties. METHODS: A series of fluorinated dimethacrylate monomers was prepared by reaction of aromatic diepoxides with fluoroalcohols and subsequent conversion of the resulting diols to the methacrylates. Composites based on monomer systems comprised of the fluorinated monomers with 1,10-decamethylene dimethacrylate and reinforced with silanized quartz filler were evaluated for conversion, water contact angle, water sorption and diametral tensile strength. RESULTS: By selection of reactants, fluorine was introduced as trifluoromethyl groups, extended fluoroalkyl pendant chains, or combinations of the two. Photopolymerization conversion among the experimental composites was generally equal to or greater than that of a conventional Bis-GMA/TEGDMA composite. While the water contact angles generally increased with fluorine content, no correlation was obtained between fluorine content and water sorption of the composites. The mechanical strength of the fluorinated composites showed a general decline with increasing fluorine content and consistent variations due to specific structural features. SIGNIFICANCE: A versatile route to fluorinated dimethacrylates with diverse structural and fluorine distribution patterns is presented. Composites from these monomers are very hydrophobic but have relatively low mechanical strength. The monomers described can be considered as useful additives to moderate the water sorption of conventional resins. However, the results of this study point to specific fluorinated resin structures that are expected to provide a more optimal balance between hydrophobicity and mechanical strength that will improve the long-term performance of dental composites.

Alcohols↗
PubMed1978

The synthesis and activity in vitro of 25-masked 1alpha-hydroxylated vitamin D3 analogs.

1alphaHydroxylated-25-masked-vitamin D3 and analogs were synthesized as probes to help evaluate the role of 25-hydroxyl group in hormone-receptor interactions of 1alpha,25-dihydroxyvitamin D3 (13a). Synthetic work on model systems showed that the steroidal 25-hydroxyl group could be easily fluorinated in high yield with diethylaminosulfur trifluoride. Treatment of 25-fluoro compound with acetic acid resulted in both elimination and displacement of fluorine by acetate. The desired 1alpha-hydroxy-25-fluoro-vitamin D3 (14b) was obtained efficiently by fluorination and subsequent deacetylation of 1alpha,25-dihydroxyvitamin D3 1,3-diacetate (13b). Also obtained was a mixture of 1alpha-hydroxyvitamin D3-24- and 25-enes (15b). Both 14b and 15b were 300-400 times less active than 13a in the chick intestinal cytosol protein binding assay, making these analogs similar in potency to 1alpha-hydroxyvitamin D3 in vitro. The essentially equivalent activity of 14b and 15b with 1alpha-hydroxyvitamin D3 indicates that in the absence of a 25-hydroxyl group some alterations to the side chain carbons of 13a may be tolerated without further weakening analog-protein interactions. The fluoroanalog 14b was also about 250 times less potent than 13a in stimulating bone resorption in vitro. These compounds should prove to be valuable tools in aiding understanding of the salient structural features of the vitamin D3 metabolites.

Animals↗
PubMed1997

Baralyme dehydration increases and soda lime dehydration decreases the concentration of compound A resulting from sevoflurane degradation in a standard anesthetic circuit.

UNLABELLED: Soda lime and Baralyme brand carbon dioxide absorbents degrade sevoflurane to CF2 = C(CF3)OCH2F, a potentially nephrotoxic vinyl ether called Compound A. Dehydration of these absorbents increases both the degradation of sevoflurane to Compound A and the degradation of Compound A. The balance between sevoflurane degradation and Compound A degradation determines the concentration of Compound A issuing from the absorbent (the net production of Compound A). We studied the effect of dehydration on the net production of Compound A in a simulated anesthetic circuit. Mimicking continuing oxygen delivery for 1, 2, or 3 days after completion of an anesthetic, we directed a "conditioning" fresh gas flow of 5 L/min or 10 L/min retrograde through fresh absorbent in situ in a standard absorbent system for 16, 40, and/or 64 h. The conditioned absorbent was subsequently used (without mixing of the granules) in a standard anesthetic circuit in which a 3-L rebreathing bag substituted for the lung. Metabolism was mimicked by introducing 250 mL/min carbon dioxide into the "lung," and the lung was ventilated with a minute ventilation of 10 L/ min. At the same time, we introduced sevoflurane in a fresh gas inflow of 2 L/min at a concentration sufficient to produce an inspired concentration of 3.2%. Because of increased sevoflurane destruction by the absorbent, progressively longer periods of conditioning (dehydration) and/or higher inflow rates increased the delivered (vaporizer) concentration of sevoflurane required to sustain a 3.2% concentration. Dehydration of Baralyme increased the inspired concentration of Compound A by up to sevenfold, whereas dehydration of soda lime markedly decreased the inspired concentration of Compound A. IMPLICATIONS: Economical delivery of modern inhaled anesthetics requires rebreathing of exhaled gases after removal of carbon dioxide. However, carbon dioxide absorbents (Baralyme/soda lime) may degrade anesthetics to toxic substances. Baralyme dehydration increases, and soda lime dehydration decreases, degradation of the inhaled anesthetic sevoflurane to the toxic substance, Compound A.

Anesthetics, Inhalation↗
PubMed2005

Isolation of two seven-membered ring C58 fullerene derivatives: C58F17CF3 and C58F18.

Fluorination of C60 at 550 degrees C leads to milligram quantities of two stable fullerene derivatives with 58-carbon cage structures: C58F18 and C58F17CF3. The compounds were characterized by mass spectrometry and fluorine nuclear magnetic resonance spectroscopy, and the data support a heptagonal ring in the framework. The resulting strain, which has hindered past attempts to prepare these smaller quasi-fullerenes, is mitigated here by hybridization change of some of the carbons in the pentagons from sp2 to sp3 because of fluorine addition. The loss of carbon from C60 is believed to occur via sequential fluorine addition to a CC single bond and an adjacent CC bond, followed by loss of a:CF2 carbene.

Journal Article↗