Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “DIOXANES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed2005

Dioxane contributes to the altered conformation and oligomerization state of a designed engrailed homeodomain variant.

Our goal was to compute a stable, full-sequence design of the Drosophila melanogaster engrailed homeodomain. Thermal and chemical denaturation data indicated the design was significantly more stable than was the wild-type protein. The data were also nearly identical to those for a similar, later full-sequence design, which was shown by NMR to adopt the homeodomain fold: a three-helix, globular monomer. However, a 1.65 A crystal structure of the design described here turned out to be of a completely different fold: a four-helix, rodlike tetramer. The crystallization conditions included approximately 25% dioxane, and subsequent experiments by circular dichroism and sedimentation velocity analytical ultracentrifugation indicated that dioxane increases the helicity and oligomerization state of the designed protein. We attribute at least part of the discrepancy between the target fold and the crystal structure to the presence of a high concentration of dioxane.

Animals↗
PubMed1990

Improved synthetic routes to the novel thromboxane receptor antagonist ICI 192605: activity of synthetic 1,3-dioxane intermediates.

A study of the synthetic routes to the thromboxane receptor antagonist ICI 192605 4(Z)-6-(2-o-chlorophenyl-4-o-hydroxyphenyl-1,3-dioxan-cis-5-yl) hexenoic acid is described which led to an improvement in overall synthetic yield from 20 to 55%. Invitro thromboxane receptor antagonist data are reported for the novel 1,3-dioxane synthetic intermediates. These data indicated that shortening of the side chain in an appropriately substituted 2,2-dimethyl-1,3-dioxane (e.g. ICI 180080) from a heptenoic acid, to a hexenoic acid, had little effect on thromboxane receptor antagonist potency (pA2 = 7.5 rabbit thoracic aorta for the heptenoic acid ICI 180080 and pA2 = 6.9 for the corresponding hexenoic acid. Human platelet aggregation pA2 values were 6.7 and 7.0, respectively).

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed2003

Synthesis and antihepatotoxic activity of some heterocyclic compounds containing the 1,4-dioxane ring system.

Silymarin isolated from Silybum marianum is a mixture of three isomers, silybin (1), silydianin (2) and silychristin (3). Silybin is the most active antihepatotoxic agent, and contains a 1,4-dioxane ring in addition to a flavonoid moiety. Based on the skeleton of silybin, we prepared some flavones and coumarins containing the 1,4-dioxane ring system and evaluated them for antihepatotoxic activity against carbon tetrachloride induced hepatotoxicity in albino rats. The degree of protection was determined by measuring biochemical parameters such as serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvate transaminase (SGPT), alkaline phosphatase (ALKP), total protein (TP) and total albumin (TA). The compounds namely 3',4'(1",4"-dioxino) flavone (4f), and 3',4'(2-hydroxy methyl, 1",4"-dioxino) flavone (4g) were found to exhibit a significant activity comparable to standard drug silymarin (silybon-70). Other compounds also exhibited good activity. The structure activity relationship (SAR) was also studied, and where the flavonoid analogues containing a hydroxy methyl group at position-2" in the dioxane ring exhibited superior antihepatotoxic activity in comparison to coumarin derivatives.

Animals↗
PubMed1989

Thermodynamics of water-induced precipitation of cholesterol and its acetate, benzoate and stearate derivatives dissolved in 1,4-dioxane and 2-propanol.

The energetics of the precipitation process depended on the solute-solvent combination and the enthalpy and entropy of precipitation compensated each other. The partial molal volumes of the lipids in both the solvents were greater than the anhydrous molar volumes, except for cholesterol in 1,4-dioxane and cholesteryl acetate in 2-propanol where the order was reverse. While the partial molal compressibilities of all the solutes studied were negative in 1,4-dioxane, those of cholesterol and cholesteryl acetate in 2-propanol were, respectively, negative and positive. The negative values were supported by considerable solvation of the solutes, particularly in 1,4-dioxane.

1-Propanol↗
PubMed1997

Synthesis of novel dioxane nucleosides having two bases, physico-chemical properties, and their biological activities.

Novel dioxane nucleosides having two bases, 2(R)-(5-fluorouracil-1-yl)-5(R)-hydroxymethyl-3(R)-(uracil-1-yl)-1,4-dioxane (7a) and 2(S)-(5-fluorouracil-1-yl)-5(R)-hydroxymethyl-3(R)-(uracil-1-yl)-1,4-dioxane (7b) were synthesized from uridine to develop a new category of nucleoside for therapeutic use. Some derivative of precursors of the nucleoside were also synthesized and several compounds synthesized were tested antitumor activity using human gastric cancer cell lines in culture.

Antimetabolites, Antineoplastic↗
PubMed2002

Thermodynamic analysis of surface formation of {1,4-dioxane + 1-alkanol} mixtures.

Surface tensions (sigma) for {1,4-dioxane + methanol, ethanol, or 1-propanol} at the temperature 298.15 K and normal atmospheric pressure have been determined as a function of mole fractions. The experimental results have been analyzed using the ideal and Langmuir models and in the light of the well-documented bulk properties of these systems, which reflect hydrogen bonding between the alcohol and 1,4-dioxane molecules. For {1,4-dioxane + ethanol} surface tensions were also measured at other temperatures between 288.15 and 308.15 K, and these data were used to calculate the surface entropy and enthalpy per unit area.

Journal Article↗
PubMed2006

Effect of TiO2 powder addition on sonochemical destruction of 1,4-dioxane in aqueous systems.

Effects of TiO(2) powder addition on sonochemical destruction of 1,4-dioxane in water were investigated through comparison of a SiO(2) powder that had similar specific surface area. Results show that addition of TiO(2) is more effective for decomposition of 1,4-dioxane in water than addition of SiO(2). The contribution of photocatalytic destruction through sonoluminescence is not a dominant mechanism for acceleration of sonochemical reactions by adding TiO(2). Sonication of TiO(2)-added water generated thermally excited holes in this case. Moreover, intrinsic oxygen vacancies in TiO(2) surface play an important role in achieving high decomposition efficiency by producing cavitation. The addition of reduced TiO(2) powder increases both the ultrasonication energy that is consumed in water and the destruction efficiency of 1,4-dioxane.

Journal Article↗
PubMed2006

Novel example of a chain structure formed by 1,4-dioxane and cobalt(II) links. Chain [Co3(mu-OOCCF3)4(mu-H2O)2(OOCCF3)2(H2O)2(C4H8O2)].2C4H8O2.

The trimer [Co3(mu-OOCCF3)4(mu-H2O)2(OOCCF3)2(H2O)2(C4H8O2)].2C4H8O2. (1) is composed of three tetragonally distorted Co(II) centers bridged by four trifluoroacetates and two bridging water molecules. 1,4-Dioxane is coordinated at a distance of 2.120(3) A from the terminal cobalt Co2; the remaining oxygen of this 1,4-dioxane links the terminal cobalt to a neighbor trimer, forming a one-dimensional chain. The crystal structure displays a network of hydrogen bonds between four noncoordinated 1,4-dioxane molecules and the coordinated terminal water molecules. The magnetic properties of 1 were analyzed with the use of the Hamiltonian including isotropic exchange interactions between real spins of a high-spin Co(II), spin-orbit coupling and a low-symmetry crystal field acting within the (4)T(1g) ground manifold of each cobalt ion. A weak antiferromagnetic exchange interaction between cobalt ions in 1 was found. The results of the magnetic model are in good agreement with the experimental observations.

Journal Article↗
PubMed1999

Synthesis, Equilibration, and Coupling of 4-Lithio-1,3-dioxanes: Synthons for syn- and anti-1,3-Diols.

Configurationally defined alpha-alkoxylithium reagents were prepared by reductive lithiation of 4-(phenylthio)-1,3-dioxanes. A new and more general synthesis of 4-(phenylthio)-1,3-dioxanes has been developed on the basis of the reduction and in situ acetylation of 1,3-dioxan-4-ones. For each of the substitution patterns examined (23a-d), reductive lithiation gave the axial alkyllithium (24a-d) with 99:1 stereoselectivity. Equilibrations of these alkyllithium reagents were possible with unhindered substrates to give the equatorial alkyllithiums 26a and 26b with excellent stereoselectivities. The more hindered axial alkyllithium reagents (24c, 24d) did not equilibrate efficiently. The equilibrium between alkyllithium reagents 24c and 26c strongly favors the equatorial isomer 26c. The inefficient equilibration with this hindered substrate is attributed to a slow rate of equilibration rather than insufficient driving force. These alkyllithium reagents could be coupled with a variety of electrophiles with retention of configuration by direct addition, copper-mediated coupling, or transmetalation to the corresponding alkylzinc reagent followed by copper-mediated coupling.

Journal Article↗
PubMed2006

Photoreactions in the gas-phase complexes of Mg(*+)-dioxanes.

Photoreactions in the gas-phase complexes Mg(*+)(1,4-dioxane) (1) and Mg(*+)(1,3-dioxane) (1M) have been examined in the wavelength region of 230-440 nm. Photoproduct assignments are facilitated with the help of deuterium substitution experiments. The main energy relaxation channel for both photoexcited complexes is the evaporation of Mg(*+). Also observed from 1 are rich photoproducts with m/z 28, 41, 54-58, 67, 69, and 88; the most abundant one at m/z 54 is designated to Mg(*+)(O=CH(2)). In marked contrast, the photolysis of 1M yields only Mg(*+)(O=CH(2)) other than Mg(*+). Density functional calculations are performed to obtain optimized geometries and potential energy surfaces of 1 and 1M. Although Mg(*+)(chair-1,4-C(4)H(8)O(2)) (1a) and Mg(*+)(boat-1,4-C(4)H(8)O(2)) (1b) are comparable in energy, the much better agreement of the experimental action spectrum of Mg(*+)(1,4-C(4)H(8)O(2)) with the calculated absorption spectrum of 1a than with that of 1b indicates the predominance of 1a in the source due to the stability of the chair-1,4-dioxane. For photoreactions, the C-O bond is found to be much more prone to rupture than the C-C bond due to the coordination of O to Mg(+) in the parent complexes. Photoreaction mechanisms are discussed in terms of two key insertion complexes, which rationalize all of the observed photoproducts.

Journal Article↗
PubMed2004

Rubidium bis(trifluoromethanesulfonyl)imidate dioxane disolvate.

The bis(trifluoromethanesulfonyl)imidate anion crystallizes with Rb as the title dioxane 1:2 solvate, Rb(+).CF(3)SO(2)NSO(2)CF(3)(-).2C(4)H(8)O(2), with the anion in a transoid conformation, as opposed to the cisoid form typically seen when there are significant cation-anion interactions. The Rb(I) cation is eight-coordinate, interacting with one anion in a chelating fashion and with two other anions through the remaining sulfonyl O atoms. The latter interactions link ion pairs through the formation of Rb(2)O(2) dimers about inversion centers at (0, 1/2, 0) and (1/2, 1/2, 0), forming extended columns which run parallel to the a axis of the unit cell. Rb-dioxane bridges crosslink these salt columns in the (010), (001) and (011) directions, resulting in a three-dimensional network solid. One dioxane solvent molecule is disordered over two half-occupancy sites.

Journal Article↗
PubMed1999

Stereoselective synthesis and receptor binding of conformationally restricted and flexible 2,4-disubstituted 1,3-dioxanes derived from benzomorphans.

The key steps in the stereoselective synthesis of the tricyclic aminomethyl derivatives 19 and 20 and the aminoethyl substituted 1,3-dioxanes 24 and 25 are nucleophilic addition of aryllithium intermediates to the nitroalkene 13, intramolecular transacetalization of the addition products 15 and 16 (only for the tricyclic derivatives 19 and 20) and subsequent reduction of the nitro group. The affinities of the secondary and tertiary amines 19c,d, 20c,d, 24c,d, and 25c,d for the ion channel binding site of the NMDA receptor, for mu-, kappa-, and sigma-receptors have been investigated. In the group of tricyclic compounds only 19d shows remarkable sigma-receptor affinity (Ki = 21.6/1.10 microM). In the 1,3-dioxane series the moderate mu- (Ki = 27.8 microM) and kappa-receptor affinity (Ki = 36 microM) as well as the high sigma-receptor affinity (Ki = 3.3 microM) of the (S,S,S)-configurated methylamine 24c should be emphasized. The pentan-1-ol 26, the side product isolated during the synthesis of 24c, is of particular interest because of its considerable affinity to mu- (Ki = 16.0 microM), kappa- (Ki = 2.8 microM), and sigma-receptors (Ki = 14.5/1.26 microM). The biphasic competition curves obtained during sigma-receptor binding studies of 19d and 26 (two Ki values) may be explained by different interaction with sigma-receptor subtypes.

Amines↗
PubMed2002

Fourier transform IR study of aggregational behavior of N-acetyl-L- and N-butyloxycarbonyl-L-glutamic acid oligomeric benzyl esters in dioxane and benzene: beta-turn --> antiparallel beta-sheet transition.

Oligomeric N-acetyl-L-glutamic acid benzyl esters (AN(p)Z) with exact residue numbers (N(p) = 2, 3, 4, and 5) and N-butyloxycarbonyl-L-glutamic acid benzyl esters (BOCN(p)Z) with exact residue numbers (N(p) = 4, 5, 6, and 8) are synthesized by a stepwise procedure in a liquid phase. The aggregational behavior of these oligomeric molecules in dioxane and benzene is examined by Fourier transform IR spectra. In particular, the concentration dependence of the IR spectra for the AN(p)Z solutions with N(p) values of 4 (A4Z) and 5 (A5Z) shows that the predominant antiparallel beta-sheet structure is stabilized above the critical aggregation concentration (cac), while other conformations including beta-turns may coexist below the cac. This fact provides evidence that aggregation induces the conformational transition from other conformers (probably beta-turns) to an antiparallel beta-sheet form. The IR results for the A3Z and A2Z solutions indicate that specific conformers (beta-turns), which are different from the beta-sheet structure, may be preferentially stabilized upon aggregation. Thus, the critical residue number of the AN(p)Z oligopeptides, which is essential for formation of a rodlike aggregate in dioxane and benzene, is 4 or 5.

Amino Acid Sequence↗
PubMed1988

In vitro BALB/3T3 cell transformation assay of nonoxynol-9 and 1,4-dioxane.

The spermicidal surfactant nonoxynol-9 (Igepal CO-630, GAF Corp.) and a potential impurity, 1,4-dioxane, were tested in the in vitro cell transformation assay using BALB/3T3 cells. Two treatment periods, 48 hr and 13 days, were used. Nonoxynol-9, tested at levels up to 10 micrograms/ml, did not induce transformation, whereas dioxane was very active in the induction of type III foci in the cultured BALB/3T3 cells.

Animals↗
PubMed1976

Substitued 5-nitro-1, 3-dioxanes: correlation of chemical structure and antimicrobial activity.

Various derivatives of 5-nitro-1, 3-dioxane were synthesized to determine the relative effect of chemical substitution in the 2-and 5-positions on broad spectrum antimicrobial activity. Each compound was evaluated quantitatively by calculation of a microbiocidal index, which measured the time to kill several different microorganisms. This test system indicated that 5-bromo-5-nitro substitution was essential for significant activity. Optimal activity was effected by 2-methyl substitution in the alkyl series and 2-hydroxy-phenyl substitution in the aryl series. The antimicrobial activity of the substituted dioxanes was not related directly to water solubility or hydrolysis to microbiocidal diols or aldehydes.

Anti-Infective Agents, Local↗
PubMed1980

Extended Hildebrand approach: solubility of caffeine in dioxane-water mixtures.

The solubility of caffeine in various dioxane-water mixtures was analyzed in terms of solute-solvent interactions using a modified version of the Hildebrand treatment for regular solutions. The solubility equation employs a term (W) to replace the geometric mean (c1c2)1/2, where c1 and c2 are the cohesive energy densities for the solvent and solute, respectively. The new equation provides an accurate prediction of solubility once the interaction energy, W, is obtained. In this case, the energy term is regressed against a polynomial in delta 1 of the binary mixture. A quartic expression of W in terms of the solvent solubility parameter was found for predicting the solubility of caffeine in dioxane-water mixtures. The expression yields an error in mole fraction solubility of less than 3%, a value approximating that of the experimentally determined solubility. The one exception to a good fit is near the maximum solubility, where a depression or valley occurs between the two peaks in solubility data; at this point, the theoretical equation predicts the solubility within approximately 9%. The new model also may be used to estimate the solubility of drug molecules employing the volume fraction of water in the solvent mixture instead of the composite solubility parameter, delta 1. The method has potential usefulness in preformulation and formulation studies during which solubility determination is important for drug design.

Caffeine↗
PubMed1983

Extended Hildebrand solubility approach: p-hydroxybenzoic acid in mixtures of dioxane and water.

The extended Hildebrand solubility approach was used to reproduce the solubilities of p-hydroxybenzoic acid in a dioxane-water system. The solubility parameter of p-hydroxybenzoic acid was determined and found to be approximately 15 (cal/cm3)1/2. Residual plots (scattergrams) were used in conjunction with R2, F, and standard deviation values to determine whether a quadratic, cubic, quartic, or higher degree polynomial was required in the calculations. The earlier iteration method for back-calculations of solubilities was replaced by the more reliable root-finder method. The solubility profile of p-hydroxybenzoic acid in dioxane-water mixtures did not follow a log linear relationship even in the ranges where the solubility parameters of the water-cosolvent mixture might be expected to produce a straight-line function, as observed in other studies.

Chemical Phenomena↗
PubMed1997

Hydrophobic properties of NAD glycohydrolase from neurospora crassa conidia and interaction with dioxane.

NAD glycohydrolase (NADase, EC 3.2.2.5) from Neurospora crassa conidia shows marked hydrophobic properties which are related to the self inhibition of the enzyme. Both aliphatic amines and carboxylic acids are able to inhibit noncompetitively the catalytic activity of the enzyme and the inhibition depends on the non-polar moiety of the substances. Also dioxane is an inhibitor of NAD glycohydrolase even though it apparently increases the specific activity of the enzyme. This effect can be explained by the fact that NADase is present as a dimer when the enzyme is concentrated or at high temperature, and dioxane binds the enzyme breaking the hydrophobic bonds in the dimeric enzyme and yielding the most active monomeric form which is only slightly inhibited by the organic solvent.

Amines↗