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At least 883 records · Page 49Linked to original sources
PubMed2006

1H, 13C and 15N NMR spectral characterization of twenty-seven 1,2-diaryl-(4E)-arylidene-2-imidazolin-5-ones.

1H, 13C and 15N NMR chemical shifts and couplings (n)J(H,C) in DMSO-d(6) at 30 degrees C have been determined for 1,2-diaryl-(4E)-arylidene-2-imidazolin-5-one derivatives 1-27. Their chemical shift assignments are based on PFG DQF 1H,1H COSY, PFG 1H,13C HMQC as well as PFG 1H,13C and 1H,15N HMBC experiments. For compounds 1-10 including aryl fluorine substituent(s) also the couplings (n)J(F,C) (n = 1 - 4) are reported.

Carbon Isotopes↗
PubMed1993

High capacity in vitro micronucleus assay for assessment of chromosome damage: results with quinolone/naphthyridone antibacterials.

A high capacity in vitro micronucleus assay was developed to evaluate the ability of selected 6-fluorinated quinolone and naphthyridone antibacterial compounds to induce micronuclei (MN) in vitro in V79 Chinese hamster lung cells. Log-phase cells in six-well cluster dishes were exposed for 3 h in the absence of S9 to 34 compounds. After treatment, cells were refed with media containing cytochalasin B, incubated for 16 h, and harvested for cell-cycle kinetics (CCK) and MN analyses. The quinolones tested were grouped according to the substituent at the 8-position. All 4 compounds having a halogen substitution at position 8, five of the six 8-trifluoromethyl quinolones, and all eight 8-methoxy-substituted compounds induced a significant increase in MN. Only 5 of the 10 naphthyridone compounds tested, having a variety of substituents at the 7-position, were inducers of MN and the overall magnitude of the response was less than with the quinolones. The minimum clastogenic concentration for the quinolones ranged from 4 to 400 micrograms/ml and for the naphthyridones this range was from 22.5 to 100 micrograms/ml. In the groups examined, napthyridone compounds were less likely than quinolones to induce in vitro MN, particularly when the substituent at the 7-position in the naphthyridone contains some bulk (methyl groups) around the amine side-chain. Most of the quinolones tested induced MN, irrespective of the substituents at positions 7 or 8.

4-Quinolones↗
PubMed2002

Theoretical calculation of heat of formation and heat of combustion for several flammable gases.

Heats of formation have been calculated by the Gaussian-2 (G2) and/or G2MP2 method for a number of flammable gases. As a result, it has been found that the calculated heat of formation for compounds containing, such atoms as fluorine and chlorine tends to deviate from the observed values more than calculations for other molecules do. A simple atom additivity correction (AAC) has been found effective to improve the quality of the heat of formation calculation from the G2 and G2MP2 theories for these molecules. The values of heat of formation thus obtained have been used to calculate the heat of combustion and related constants for evaluating the combustion hazard of flammable gases.

Fires↗
PubMedDate not supplied

Molecular interaction between organophosphorus acid anhydrolase and diisopropylfluorophosphate.

Organophosphorus acid anhydrolases (OPAA; E.C.3.1.8.2) are a class of enzymes that hydrolyze a variety of toxic acetylcholinesterase-inhibiting organophosphorus (OP) compounds, including pesticides and fluorine-containing chemical nerve agents. In this paper, subphase conditions have been optimized to obtain stable OPAA Langmuir films, and the diisopropylfluorophosphate (DFP) hydrolysis reaction catalyzed by OPAA in aqueous solution and at the air-water interface was studied. OPAA-DFP interactions were investigated utilizing different spectroscopic techniques, that is, circular dichroism and fluorescence in aqueous solution and infrared reflection absorption spectroscopies at the air-water interface. The characterization of OPAA and its secondary structure in aqueous solution and as a monolayer at the air-water interface in the absence and in the presence of DFP dissolved in aqueous solution or in the aqueous subphase demonstrated significantly distinctive features. The research described herein demonstrated that OPAA can be used in an enzyme-based biosensor for DFP detection.

Aryldialkylphosphatase↗
PubMed2002

Carbon dioxide as a solubility "switch" for the reversible dissolution of highly fluorinated complexes and reagents in organic solvents: application to crystallization.

Highly fluorinated organic or organometallic solid compounds can be made to dissolve in liquid hydrocarbons by the application of 20-70 bar of CO(2) gas. Subsequently releasing the gas causes the compounds to precipitate or crystallize, giving quantitative recovery of the solid. The resulting crystals can be of sufficient quality for single-crystal X-ray crystallography; the structures of Rh(2)(O(2)CCF(2)CF(2)CF(3))(4)(DMF)(2), Rh(2)(O(2)C(CF(2))(9)F)(4)(MeOH)(2), Cr(hfacac)(3), and P[C(6)H(3)(3,5-CF(3))(2)](3) have been determined from crystals grown in this manner.

Journal Article↗
PubMed1983

Novel fluorinated antifolates. Enzyme inhibition and cytotoxicity studies on 2'- and 3'-fluoroaminopterin.

Two novel analogues of aminopterin with a single fluorine substitution in the 2' (compound 8) or in the 3' (compound 9) position of the p-aminobenzoyl group were synthesized and evaluated as inhibitors of dihydrofolate reductase from two bacterial species and from human HeLa cells. The 2'-fluoro compound was bound essentially the same as aminopterin itself, while the 3'-fluoro derivative bound two- to threefold more tightly in all cases. UV spectral shifts indicated normal binding of the pteridine. Cytotoxicity studies against mouse leukemia L1210 cells and the human stomach cancer line HuTu80 indicated equivalent toxicity of the parent drug with the 2'-fluoro analogue. 3'-Fluoroaminopterin was, however, twice as toxic as aminopterin to both cell lines.

Aminopterin↗
PubMed2005

F-18 stilbenes as PET imaging agents for detecting beta-amyloid plaques in the brain.

Imaging agents targeting beta-amyloid (Abeta) may be useful for diagnosis and treatment of patients with Alzheimer's disease (AD). Compounds 3e and 4e are fluorinated stilbene derivatives displaying high binding affinities for Abeta plaques in AD brain homogenates (Ki = 15 +/- 6 and 5.0 +/- 1.2 nM, respectively). In vivo biodistributions of [18F]3e and [18F]4e in normal mice exhibited excellent brain penetrations (5.55 and 9.75% dose/g at 2 min), and rapid brain washouts were observed, especially for [18F]4e (0.72% dose/g at 60 min). They also showed in vivo plaque labeling in APP/PS1 or Tg2576 transgenic mice, animal models for AD. Autoradiography of postmortem AD brain sections and AD homogenate binding studies confirmed the selective and specific binding properties to Abeta plaques. In conclusion, the preliminary results strongly suggest that these fluorinated stilbene derivatives, [18F]3e and [18F]4e, are suitable candidates as Abeta plaque imaging agents for studying patients with AD.

Alzheimer Disease↗
PubMed2003

Efficient and stereoselective synthesis of beta-trifluoromethyl alpha,beta-unsaturated esters via iron(III) porphyrin-catalyzed olefination of ketones.

beta-Trifluoromethyl alpha,beta-unsaturated esters were efficiently prepared by reactions of fluorine-containing ketones with diazo compounds via metalloporphyrin-catalyzed olefination in the presence of triphenylphosphine. The commercially available Fe(III)(TPP)Cl (TPP: tetraphenylporphyrin) is effective for catalyzing the olefination of a variety of trifluoromethyl ketones with different diazoacetate esters under mild conditions. The reactions proceeded with high yields (up to 95% isolated yield) and high stereoselectivity (up to 99% (E)-selectivity).

Journal Article↗
PubMed2006

Influence of electronic properties of naphthalene compounds on contact angles.

Contact angles of a homologous series of naphthalene compounds on films of a fluorinated acrylate polymer (EGC-1700) deviate from an ideal pattern of contact angles. The deviations increase with the electronegativity of the constituent atoms of the liquid molecules. The results suggest that an uneven distribution of electrostatic charges over the molecules creates strong dipole moments, giving rise to fairly strong dipole-dipole and dipole-induced dipole interactions between liquid molecules and the EGC-1700 chains, which have large dipole moments. In comparison, contact angles of the same probe liquids on the films of Teflon AF 1600, which have small dipole moments, fall on a smooth curve representing the surface tension of the polymer film.

Computer Simulation↗
PubMed2006

The reaction of TiF4 with Li(OC(CF3)2Ph): direct synthetic route to the lithium-titanium heterometallic fluoride bridged complex {Li(THF)2TiF3(OC(CF3)2Ph)2}2 and Ti(OC(CF3)2Ph)4 alkoxide.

Reaction of TiF4 and LiORf (Rf = C(CF3)2Ph) in the donor solvent-THF lead to the isolation of the heterometallic lithium-titanium complex (THF)2Li(mu-F)2Ti(ORf)2(mu-F)2Ti(ORf)(2)(mu-F)2Li(THF)2 (1) and Ti(ORf)4 alkoxide (2). Interaction of TiF4 and LiORf in the non-coordinating and low polar toluene yielded only Ti(ORf)4 (2). Compounds 1 and 2 were characterized by X-ray single-crystal analysis, IR, NMR and mass spectrometry. Compound 1 is a centrosymmetric fluorine bridged dimer and contains the Li(mu-F)2Ti(mu-F)2Ti(mu-F)2Li cage. Complex 2 containing four bulky ligands is monomeric. NMR evidence is presented that the TiF4 and LiORf in THF solution gave lithium-titanium heterometallic complexes containing Li-(mu-F)-Ti and the Ti-(mu-F)-Ti bonds.

Journal Article↗
PubMed2005

Design, synthesis, and anticancer activity of fluorocyclopentenyl-pyrimidines.

Novel pyrimidine nucleosides with fluorocyclopentene ring were synthesized from D-ribose via stereoselective Grignard reaction and electrophilic vinyl fluorination as key steps. Among compounds tested, cytosine derivative 15a was found to show high growth inhibition against a broad range of human tumor cell lines.

Antineoplastic Agents↗
PubMed2002

Beyond EPO.

The objective of this review is to examine newer compounds coming on the market capable of boosting red blood cell concentration and thus improving aerobic activities in particular. Erythropoietin (EPO) has been used extensively in the past by the athletic community in this role. Its main disadvantages are the side effects due to increased viscosity, and the recent development of a blood test for drug testing methods. Two new methods of increasing red blood cell concentration for use in medicine are hemoglobin oxygen carriers and perfluorocarbons, each having a different structure, but which allow oxygen to be delivered to the tissues. Hemoglobin oxygen carriers physically alter the hemoglobin molecule by several methods so that complications such as renal toxicity are obviated. Perfluorocarbons belong to a group of synthetic compounds containing hydrocarbons to which fluorine is added. Evidence is available to suggest that athletes are already adapting these newer molecules for their benefit.

Animals↗
PubMed1989

Structure-activity relationships of tetramethylpiperidine-substituted phenazines against Mycobacterium leprae in vitro.

In a previous study of structure-activity relationships of selected phenazines against Mycobacterium leprae in vitro, compounds containing a 2,2,6,6-tetramethylpiperidine substitution at the imino nitrogen were most active. Therefore, the effect of substitution at the para positions of the phenyl and anilino groups in tetramethylpiperidine-substituted phenazines was assessed. As determined by radiorespirometry, activity in ascending order was observed in compounds substituted with hydrogens or fluorines, ethoxy groups, methyl groups, chlorines, and bromines and correlated with partition coefficients in octanol-water.

Anti-Bacterial Agents↗
PubMed2005

[Falecalcitriol as a new therapeutic agent for secondary hyperparathyroidism].

The 26 and 27 positions of vitamin D molecular structure of calcitriol were fluorinated with 3 atoms of fluorine each and the new compound was named falecalcitriol (F6). This new compound was found to be 10 to 100 times more active compared with calcitriol depending on the target organs. As a mechanism of strong action of F6 it was discovered that F6 is hydroxylated at 23 position which has almost the same activity as the mother compound. It was also demonstrated that the PTH suppressive effect was relatively stronger than the calcium absorption action from the intestine. Thus F6 was authorized to be applied to the treatment of secondary hyperparathyoroidism in hemodialysed patients as well as to the treatment of hypoparathyroidism.

Animals↗
PubMed1984

Novel reactivity of cytochrome P-450-CAM. Methyl hydroxylation of 5,5-difluorocamphor.

The interaction of the camphor hydroxylating P-450 isolated from Pseudomonas putida grown on camphor (P-450-CAM) with 5,5-difluorocamphor, a substrate analog in which the two methylene hydrogens at the normal site of hydroxylation have been replaced with fluorine, has been examined. This compound binds tightly to the enzyme with a dissociation constant and UV-visible absorption spectrum identical to that observed with d-camphor. In the presence of the reconstituted P-450-CAM system, 5,5-difluorocamphor is metabolized at a rate approximately one-third the rate of the physiological substrate, d-camphor, resulting in the formation of a hydroxylated product with a molecular weight of 204 as well as a minor (less than 3%) hydroxylated product of molecular weight 184. Isotopically labeled molecular oxygen (18O2) is incorporated into the major product while labeled oxygen from water (H218O) is not incorporated, clearly indicating that the hydroxyl oxygen originates from dioxygen. Proton NMR characterization (400 MHz) of the major product has led to its assignment as 5,5-difluoro-9-hydroxy-camphor, with supporting structural evidence provided by the mass spectral fragmentation pattern. The formation of 9-hydroxylated product represents the first example of methyl hydroxylation catalyzed by cytochrome P-450-CAM, indicates a change in regio-selectivity when the normal site of reaction is blocked, and supports the hypothesis that the delivery of the oxygen atom occurs from the exo side of the camphor molecule.

Camphor↗
PubMedDate not supplied

Improved in vitro gene transfer mediated by fluorinated lipoplexes in the presence of a bile salt surfactant.

BACKGROUND: Progress in the field of gene transfer with non-viral vectors requires systems that allow efficient gene expression in the presence of biological fluids such as pulmonary surfactants, for gene transfer to the respiratory epithelium for cystic fibrosis gene therapy, or bile salts (which contain powerful anionic detergents), for gene transfer to the biliary epithelium for gene therapy of the hepatobiliary disease associated with cystic fibrosis (CF). We have performed a comparative analysis of the disintegration and DNA accessibility of fluorinated and conventional lipoplexes, and their in vitro transfection potential in the presence of a powerful biliary surfactant. METHODS: The disintegration and DNA accessibility of conventional and fluorinated cationic lipoplexes and their in vitro transfection efficiency of human lung carcinoma epithelial A549 cells were studied in the presence of various concentrations of sodium taurocholate (STC), an anionic bile salt detergent. The conventional and fluorinated lipoplexes were formulated from Transfectam" (or DOGS) and from fluorinated lipospermines, analogs of DOGS, respectively, and a luciferase reporter plasmid. The fluorinated lipids used in the present study were selected for their different degrees of fluorination in order to investigate the impact on stability and transfection. The effects of the detergent on lipoplex integrity were examined by evaluating the ability of the lipospermines to prevent, in the presence of the surfactant, ethidium bromide (BET) intercalation into the plasmid (fluorescence monitoring). RESULTS: Fluorinated cationic lipoplexes exhibited greater stability than DOGS lipoplexes with respect to STC lytic activity. Indeed, while the DOGS lipoplexes were fully disintegrated at a [STC]/[lipid] molar ratio of 1,320, all the DNA intercalation sites of the most fluorinated lipoplexes investigated became accessible to BET for a two-fold higher [STC]/[lipid] molar ratio. A higher transfection potential in the presence of the detergent was also shown for the fluorinated lipoplexes as compared with the DOGS preparation. At a 10 mM concentration of STC and at a [STC]/[lipid] molar ratio of 264, lipofection when mediated by DOGS was fully inhibited while the detergent had no inhibitory effects on the lipofection mediated by the fluorinated DF4C11-GS [spermine-5-carboxyglycine N,N-di-11-(F-butyl)-undecylamide] or DF6E11-GS [spermine-5-carboxyglycine N,N-di-[11-(F-hexyl)-undec-10-enyl]amide] lipospermines. A higher detergent concentration (up to 17.5 mM) and a higher [STC]/[lipid] ratio (up to 462) were necessary to inhibit lipofection by the fluorinated formulations. Overall, the lipoplex stability and transfection potential in the presence of the detergent was found to improve with increasing degrees of fluorination of the lipospermines. CONCLUSIONS: The present work shows improved stability of, and higher lipofection levels with, fluorinated lipoplexes in the presence of surfactants. The results confirm the very promising potential of fluorinated lipoplexes as gene transfer vectors. These compounds constitute a very attractive alternative to their more conventional homologs. The correlation found between the degree of fluorination of the lipoplexes, their stability and their lipofection levels suggests that enhanced lipophobic and hydrophobic properties protect them against disintegration and, consequently, prevents DNA from being degraded and from interacting with lipophilic and hydrophilic biocompounds responsible for lipofection inhibition.

Bile Acids and Salts↗