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At least 523 records · Page 29Linked to original sources
PubMed2000

Dentin bonding and sealing ability of a new root canal resin sealer.

The aims of this study were to find a dentin bonding system suitable for root canal treatment using a newly developed root canal resin sealer, and to examine its sealing ability. The sealer was composed of vinylidene fluoride/hexafluoropropylene copolymer, methyl methacrylate, zirconia, and tributylborane catalyst. The effects of dentin conditioners and primers on dentin bonding were studied by tensile bond strength testing and scanning electron microscopy. Apical and coronal leakage were evaluated at 1-, 4-, and 12-wk intervals by a dye penetration test using a methylene blue solution. Pulp Canal Sealer EWT and Sealapex were used as controls. Significantly high bond strength was obtained by treating dentin with EDTA, followed by application of a glutaraldehyde/2-hydroxyethyl methacrylate primer. The experimental resin sealer produced a significantly superior coronal seal at 12 wk when compared with the two control sealers (p < 0.05). Scanning electron microscopic examination revealed few gaps at the resin sealer-dentin interface.

Alkenes↗
PubMed1988

Evaluation of the side arm of (naphthylvinyl)pyridinium inhibitors of choline acetyltransferase.

A number of quaternary salts of trans-4-(beta-1-naphthylvinyl)pyridine (NVP) were synthesized and evaluated as inhibitors of the enzymes choline acetyltransferase (ChAT) and acetylcholinesterase (AChE). Structural variations in the side arm attached to the pyridine nitrogen atom demonstrate that an inductive effect is small but significant for activity. Inhibition of ChAT by alkylated derivatives decreases when electron-withdrawing groups are placed in the side chain. Substitution of a methyl group on the pyridine ring only slightly affects activities toward ChAT and AChE. When the pyridinium moiety is replaced by an imidazolium ring, no ChAT inhibition was observed. The imidazolium compound, however, was a weak inhibitor of AChE. For design of affinity columns for purification of ChAT, the data also supports the use of long chain alkylated amide derivatives of NVP.

Animals↗
PubMed2002

Halo-enediynes: probing the electronic and stereoelectronic contributions to the Bergman cycloaromatization.

A series of halogen-substituted cyclic enediynes were prepared with use of carbenoid coupling strategy. DFT analysis, initially used to identify synthesis candidates, was also employed to rationalize the propensity for cycloaromatization of the compounds. In all cases studied the halogen atom had a strongly retardative effect on the thermal Bergman cycloaromatization reaction. The isolation of the first C-9 monochloroenediyne is noteworthy, and may find application in prodrug design.

Alkynes↗
PubMed1999

Rational inhibitor design, synthesis and NMR spectroscopic study by transferred nuclear overhauser spectroscopy of novel inhibitors of cinnamyl alcohol dehydrogenase, a critical enzyme in lignification.

Cinnamyl alcohol dehydrogenase is one of the enzymes controlling the first two committed steps of lignification. Using a 3-dimensional similarity model of this enzyme, a series of novel phosphonates (1-5) was designed as potential inhibitors. Phosphonates 1-5 were synthesized in good yield by reaction of the corresponding cinnamaldehydes with tetraethylmethylene diphosphonate. Monophosphonic acids 6 and 7 were obtained by basic hydrolysis of the corresponding phosphonates while phosphonamidate 8 was synthesized by reacting benzylamine with the iminium salt intermediate of the monophosphonic acid. Using recombinant cinnamyl alcohol dehydrogenase (CAD, EC 1.1.1.195) the inhibitory activity of these compounds was evaluated and compared with that of the carbonyl analogues. Inhibition kinetic studies showed compounds 2 and 3 to be mixed type linear inhibitors while compound 4 was uncompetitive. 1H NMR studies of inhibitor 2, for which Ki and Ki' were 20 and 86 microM, respectively, in the presence of CAD based on selective line-broadening showed an increased interaction of the 3-OMe group of the aromatic ring of the inhibitor with the active site of the CAD. A transferred nuclear overhauser effect spectroscopy (TRNOESY) experiment for inhibitor 2 with CAD was used to determine the conformation of this compound bound to CAD. These results were found to be consistent with the 3-dimensional structural model of the enzyme.

Alcohol Oxidoreductases↗
PubMed2005

Physical stability of the amorphous state of loperamide and two fragment molecules in solid dispersions with the polymers PVP-K30 and PVP-VA64.

The purpose of the present study was to investigate the impact of intermolecular forces on the stability of the amorphous state of loperamide and two of its fragment molecules (4-dimethylamino-N,N-dimethyl-2,2-diphenyl-butyramide (F1) and 4-(4-chlorophenyl)-4-piperidinol (F2)) in solid dispersions with PVP-K30 and PVP-VA64. The stability of originally homogeneous and amorphous dispersions was investigated under different storage conditions. The chemical stability of the compounds was evaluated with HPLC. TGA-analysis was used in order to assess the amount of water in the samples, whereas MT-DSC-measurements were performed to investigate changes in the physical state of the compounds caused by the storage procedure. TGA-analysis reveals a higher uptake of water in humid conditions of the dispersions with PVP-K30 in comparison to those with PVP-VA64, hereby reflecting the more hydrophilic nature of the former polymer. This water acts as a plasticizing agent resulting in an increased mobility and decreased glass transition temperature. Since the degree of supersaturation and the molecular mobility have an influence on the stability of the amourphous state, both parameters were assessed. With respect to the degree of supersaturation of the compounds in the dispersions, the materials seem to be very much alike. Therefore it was postulated that the induction of crystallization in the F1/polymer dispersions stored at high RH (52%) is due to higher molecular mobility of this compound in the dispersions in comparison to F2. The hydrogen bonds that are being formed between F2 and the polymers reduce its mobility and secure this compound from crystallization upon storage, thus indicating the importance of specific interactions with respect to stability issues of solid dispersions. No hydrogen bonds are formed between F1 and the polymers. As a result, the stability of the amorphous state of the compound is being compromised and crystallization takes place. Loperamide, that also does not form hydrogen bonds with the polymers, is less susceptible to crystallization due to its intrinsic good glass forming properties.

Calorimetry, Differential Scanning↗
PubMed2006

Tandem nucleophilic addition/fragmentation reactions and synthetic versatility of vinylogous acyl triflates.

A thorough analysis of the chemistry of vinylogous acyl triflates provides insight into important chemical processes and opens new directions in synthetic technology. Tandem nucleophilic addition/C-C bond cleaving fragmentation reactions of cyclic vinylogous acyl triflates 1 yield a variety of acyclic acetylenic compounds. Full details are disclosed herein. A wide array of nucleophiles, such as organolithium and Grignard reagents, lithium enolates and their analogues, hydride reagents, and lithium amides, are applied. The respective reactions produce ketones 2, 1,3-diketones and their analogues 3, alcohols 4, and amides 5. The present reactions are proposed to proceed through a 1,2-addition of the nucleophile to the carbonyl group of starting triflates 1 to form tetrahedral alkoxide intermediates C, followed by Grob-type fragmentation, which effects C-C bond cleavage to yield acyclic acetylenic compounds 2-5 and 7. The potent nucleofugacity of the triflate moiety is channeled through the sigma-bond framework of 1, providing direct access to the fragmentation pathway without denying other typical reactions of cyclic vinylogous esters. The synthetic versatility of vinylogous acyl triflates, including functionalization reactions of the cyclic enone core (1 --> 6 or 8), is also illustrated.

Chemistry, Organic↗
PubMed1992

A study of tobacco carcinogenesis. XLVII. Bioassays of vinylpyridines for genotoxicity and for tumorigenicity in A/J mice.

3-Vinylpyridine is formed from nicotine during the smoking of tobacco products. Consequently it is found in mainstream and side-stream smoke of cigarettes and cigars and in environmental tobacco smoke. In this study, 3-vinylpyridine and its isomers 2- and 4-vinylpyridine as well as styrene (vinylbenzene) were bioassayed for mutagenicity in Salmonella typhimurium strains TA 1535, TA 1538, TA 98 and TA 100 and for their genotoxicity in the rat hepatocyte DNA-repair test. In both in vitro assays-all three vinylpyridines and styrene were inactive. In a test for tumorigenicity in which the test compounds were injected intraperitoneally into A/J mice (total dose 200 mumol/animal) there was no significant incidence of lung adenoma nor of any other type of tumors.

Animals↗
PubMed1976

(Vinylaryloxy)acetic acids. A new class of diuretic agents. 2. (4-(3-Oxo-1-alkenyl)phenoxy)acetic acids.

A series of (E)-[4-(3-oxo-1-alkenyl)phenoxy]acetic acids was synthesized and tested in dogs for saluretic and diuretic properties. Several compounds exhibited noteworthy activity, e.g., (E)-[2,3-dichloro-4-(3-oxo-1-butenyl)phenoxy]acetic acid (3a). While possessing only half of the dose potency of ethacrynic acid (2), the active compounds act similarly to this diuretic in causing a prompt increase in the excretion of water and in the excretion of sodium and chloride ions in approximately equimolar amounts. Potassium ion excretion is increased but less markedly than sodium excretion.

Acetates↗
PubMed2004

Application of HS-SPME and GC-MS to characterization of volatile compounds emitted from Osmanthus flowers.

Headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) was developed for characterization of volatile compounds emitted from two varieties Osmanthus flowers of O. fragrans var. latifolius and O. fragrans var. thunbergii. The SPME parameters were studied, the optimum conditions of a 65 microm carbowax/divinylbenzene (CW/DVB), extraction temperature of 22 degrees C and extraction time of 10 min were obtained and applied to extraction of the volatile emissions. Fourteen compounds released from both varieties of Osmanthus flowers were separated and identified by GC-MS, which mainly included alpha-linalool, beta-linalool, trans-linalool oxide, cis-linalool oxide, alpha-lonone, beta-lonone, capraldehyde and decalactone. By comparing their peak areas, we found that the sums of the fourteen compounds from the two Osmanthus flowers were very close, while the relative contents of individual volatile compounds in the two emissions were very different. The relative content of alpha-linalool and beta-linalool in O. fragrans var. latifolius were 39.46% and 0.51%, while in O. fragrans var. thunbergii were 9.53% and 27.71%. Due to their different relative contents, the two varieties of flower have different fragrances.

Aldehydes↗
PubMed2005

Sesquiterpenes from the New Zealand Liverwort Lepidolaena hodgsoniae.

NMR studies have shown that seven new sesquiterpenoids, 3, 4, 5a, and 7-10, isolated from dried samples of the New Zealand liverwort Lepidolaena hodgsoniae have the same substituted cyclopentapyran ring system as the previously described insecticidal sesquiterpene diene hodgsonox (1), which has been reported only from this plant. In all but one compound, 10, the 1,1-disubstituted double bond of hodgsonox has migrated into an endocyclic position, but only two, 5a and 9, have the double bonds in conjugation. These seven new compounds represent a variety of different oxidation levels. Two of the new derivatives, 9 and 10, were isolated only from an aged sample and are presumably artifacts. The only other terpenoid isolated in significant quantity was (7R,10R)-calamenene (2).

Hepatophyta↗
PubMed1981

Inhalation pharmacokinetics based on gas uptake studies. I. Improvement of kinetic models.

An improve pharmacokinetic model is described for inhalation of volatile xenobiotics from a closed gas phase system. This model is based on steady-state kinetics and covers metabolic elimination processes of either first-order, zero-order, or Michaelis-Menten characteristics. It is emphasized that the distribution of a volatile compound between gas phase and organism under steady-state conditions may be much different from a static equilibrium obtained in absence of metabolism, as it is observed after application of a metabolic inhibitor. A re-analysis or previous experimental data on dose-dependent pharmacokinetics of different haloethylenes reveals that, in general, the metabolic elimination processes of the rapidly equilibrating mono-haloethylenes (and vinylidene fluoride) can be resolved with excellent accuracy into sections of first-order and zero-order kinetics. Other compounds show a more smooth transition from first-order elimination (at lower atmospheric concentrations) into conditions of saturation (dichloroethylenes, trichloroethylene). The analyses are consistent with a recent concept of Andersen (1980) that metabolic elimination of inhaled xenobiotics is limited by either the capacity of metabolic enzymes or factors of transport to the metabolic sites.

Animals↗
PubMed1976

(Vinylaryloxy)acetic acids. A new class of diuretic agents. 1. (Diacylvinylaryloxy)acetic acids.

A series of (diacylvinylaryloxy)acetic acids was synthesized and tested in dogs for saluretic and diuretic activity. Several compounds exhibit a high order of activity, the most active being [2,3-dichloro-4-(2,2-diacetylvinyl)-phenoxy]acetic acid (3). This compound is about three times as potent as [2,3-dichloro-4-(2-methylenebutyryl)-phenoxy]acetic acid (ethacrynic acid) but is qualitatively similar in causing a prompt increase in the excretion of water and in the excretion of sodium and chloride ions in approximately equimolar amounts. Saturation of the double bond of 3 virtually abolishes activity lending support to the hypothesis that the saluresis induced by these compounds, like that of ethacrynic acid, is related at least in part to a chemical reaction with protein-bound sulfhydryl groups. Four mercaptan adducts of 3 were prepared; these probably function as prodrugs in producing saluresis. The adduct with mercaptoacetic acid is as active as 3 itself.

Acetates↗
PubMed1982

Effect of chlorinated ethanes and ethylenes on electron transport in rat liver mitochondria.

For all members of the chlorinated ethane and ethylene series except monochloroethylene, the effects on the oxygen consumption of isolated rat mitochondria were studied. All the tested compounds inhibited glutamate and malate oxidation, and their inhibitory potency increased in the order of the number of contained chlorines. The eight compounds of greatest potency were also investigated for their inhibition of succinate oxidation in mitochondria and inhibition of NADH oxidation in sonicated submitochondrial particles. The data obtained suggested that the inhibition of substrate oxidation was due to blockade of electron transport and the most susceptible portion was located from NADH to CoQ.

Animals↗
PubMed1996

"Vinylogs" and "acetylenylogs" of beta-adrenergic agents.

Vinylogous (Groups III and V) and acetylenologous (Group IV) analogs of the classical beta-adrenergic agents--stimulants and blockers--were prepared in order to evaluate the effect of degree of saturation, position of unsaturation and rigidity of the chain linking the aromatic ring and the amino containing functional group on biological activity. Derivatives from Group III, which represent 4-aryl-3-butenyl-2-ol-amine analogs of Group II, retained beta 1-adrenoceptor antagonist activity albeit substantially less potent (50-200-fold) than that possessed by their aryloxy counterparts. Consistent with the SAR for Group II compounds, substitution at position 2 of the aromatic ring yielded the most potent antagonists (5a, 5d, 5g), with KB's ranging from 73-93 nM while 3,4-dichloro substitution (5e) markedly reduced antagonist potency (KB = 2,400 nM). Agonist activity was also noted for 5b and 5d, suggesting that these compounds may be best classified as partial agonists. Representatives from Groups IV and V were inactive as antagonists at the beta 1-adrenoceptor confirming the importance of the spatial relationship between the hydroxyl and the amino nitrogen.

Acetylene↗
PubMed1975

Polynucleotide analogs: acrylic acid and maleic acid copolymers of 1-vinyluracil and 9-vinyladenine.

Radical-induced copolymerization of 1-vinyluracil and maleic anhydride gave, after hydrolysis, a polymer containing a 1:1 monomer ratio of 1-vinyluracil-maleic acid. Gamma-Ray-induced copolymerization of 1-vinyluracil with acrylic acid gave a polymer with a ratio of 1:1.7. Similar treatment of 9-vinlyadenine and acrylic acid resulted in a polymer with a 1:3.2 ratio. These three compounds are potent stimulants of poly (uridylic acid) coded polyphenylalanine synthesis in an in vitro cell free system purified from Escherichia coli MRE 600. The double-stranded polymer, poly(inosinic acid)-poly(cytidylic acid), also stimulates polyphenylalanine synthesis in this assay.

Adenine↗
PubMed1979

[Antibacterial and antiviral activity of the polychloroethyl- and beta,beta-dichlorovinylamides of carboxylic acids].

A number of compounds having antiviral and antibacterial (antistaphylococcal) activity was found in the beta,beta-dichlorvinyl- and alpha-chlor(alpha-oxy)-beta,beta,beta-trichlorethylamide series of carboxylic acids. The antistaphylococcal activity of the compounds under study was found to depend, to a certain extent, ontheir chemical structure, whereas no such dependence was established in respect of their antiviral activity. In the treatment of combined influenza-staphylococcal infection a decrease in antistaphylococcal effect was observed, while antiviral activity remained stable.

Amides↗
PubMed2004

Solid-phase extraction of polar compounds with a hydrophilic copolymeric sorbent.

A new synthesized copolymer based on N-vinylimidazole-divinylbenzene (VIm-DVB) was tested as a sorbent for the solid-phase extraction (SPE) of polar analytes. In the on-line SPE, this synthesized sorbent enabled 100 ml of sample to be preconcentrated with recoveries as high as 80% for oxamyl, phenol (Ph) and derivates, bentazone and (4-chloro-2-methylphenoxy)acetic acid (MCPA). For the off-line SPE, 1000 ml of sample was extracted and recoveries were higher than 92% for all compounds with the exception of oxamyl (83%) and methomyl (78%). The VIm-DVB sorbent gives better recoveries than the previously synthesized 4-vinylpyridine-divinylbenzene (VP-DVB) resin and similar to such highly crosslinked commercial sorbents as LiChrolut EN or Oasis HLB. Real water samples were used to validate the on-line SPE method. Linearity was good and detection limits were between 0.1 and 0.2 microg l(-1).

Imidazoles↗
PubMed2001

(E)-1-(2'-deoxy-beta-D-ribofuranosyl)-2,4-difluoro-5-(2-iodovinyl)benzene.

This analysis of the title compound, C13H13F2IO3, establishes the orientation of (E)-5-(CH=CH-I) as antiperiplanar (ap) to the C-C bond (5-6 position) of the 2,4-difluorophenyl ring system, with the (E)-5-(CH=CH-I) H atom located in close proximity (2.17 A) to the F4 atom of the 2,4-difluorophenyl moiety.

Antiviral Agents↗