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PubMed2000

Synthesis and antifungal activities of R-102557 and related dioxane-triazole derivatives.

Novel triazole compounds with a dioxane ring were synthesized. Condensation of the diol precursor 10 with various aromatic aldehydes 11-13 under acidic conditions afforded a series of dioxane-triazole compounds 14-16. The antifungal activities of the compounds 14-16 were evaluated in vivo in mice infection models against Candida and Aspergillus species. High activities were seen for the derivatives with one or two double bond(s) and an aromatic ring substituted with an electron-withdrawing group in the side chain. Among the derivatives, R-102557 (16R: Ar=4-(2,2,3,3-tetrafluoropropoxy)phenyl) showed excellent in vivo activities against Candida, Aspergillus and Cryptococcus species. It also showed high tolerance in a preliminary toxicity study in rats.

Animals↗
PubMed1978

Metabolism of the antimicrobial agent nibroxane, 5-bromo-2-methyl-5-nitro-m-dioxane, in the rat.

1. The metabolism of nibroxane, a topically effective antimicrobial agent has been studied in the rat after oral and dermal administrations. 2. Plasma level studies in vitro and in vivo showed nibroxane to be rapidly debrominated to 2-methyl-5-nitro-m-dioxane. 3. Nibroxane is rapidly absorbed and extensively metabolized in the rat regardless of the route of administration. 4. Enzymic hydrolysis of the m-dioxane ring was of major importance in the biotransformation of nibroxane. The major eliminated metabolite in the rat was 2-nitropropan-1,3-diol.

Administration, Oral↗
PubMed2000

Conformational features of reduced and disulfide intact forms of hen egg white lysozyme in aqueous solution in presence of 3-chloro-1, 2-propanediol and dioxane: implications for protein folding intermediates.

Conformational features of reduced and disulfide intact hen egg white lysozyme in aqueous 1,4-dioxane and 3-chloro-1, 2-propanediol solutions have been examined using circular dichroism and fluorescence spectroscopy. We find that in presence of 1, 4-dioxane, reduced lysozyme assumes a relatively compact conformational form with secondary structure closer to native state and no tertiary structure as judged by peptide and aromatic CD spectra and ANS binding studies monitored by fluorescence. Further, in presence of 40% (v/v) 3-chloro-1, 2-propanediol, disulfide intact lysozyme (DI-lysozyme) assumes a conformational form with native like secondary structure and no tertiary structure akin to a molten globule state. We correlate our results to kinetic hydrogen- deuterium exchange NMR results of the refolding of lysozyme available in literature and suggest that the conformational forms observed in our study could be models for kinetic intermediates in the refolding of lysozyme.

Animals↗
PubMed1998

[Determination of dioxane in alkyl alcohol polyoxyethylene ether].

In this paper, dioxane in alkyl alcohol polyoxyethylene ether has been determined by headspace gas chromatography. The standard curve and headspace detection conditions are given. Correlation coefficient is 0.9989. The recoveries of dioxane ranged from 91.6% to 97.6%. The relative standard deviations were less than 2.5%. The limit of determination was 20 micrograms/L. The method is simple, fast and accurate with higher sensitivity, less interference and better reproducibility.

Chromatography, Gas↗
PubMed1992

[Structure of macrocyclic K+, Rb+-complexon of meso-valinomycin monohydrate, cyclo[-(D-Val-Hyi-Val-D-Hyi)3-].H2O, in a crystalline complex with dioxane by x-ray structural data].

The crystal structure of a valinomycin analogue, cyclo[-(D-Val-Hyi-Val-D-Hyi)3-]x(C60H102N6O18) crystallized with dioxane and water molecules, has been solved by X-ray direct methods. The conformation found is analogous to one established for free meso-valinomycin crystallized from other organic solvents. It is characterized by a centrosymmetric bracelet form, stabilized by six intramolecular 4----1 type hydrogen bonds between amide N-H and C = O groups. One water molecule is fixed asymmetrically by hydrogen bonds in the internal negatively charged cavity of the complexon. The meso-valinomycin molecule "bracelets" in the crystal form stacks alternatively with dioxane molecules.

Cations, Monovalent↗
PubMed1991

Assay of 1,4-dioxane in commercial cosmetic products by HPLC.

The HPLC assay of 1,4-dioxane in a wide range of commercially available cosmetics containing polyethoxylated surfactants is described. After solid-phase extraction using Bakerbond CN- and Bakerbond C18-cartridges, samples were directly analysed on a LiChrospher CH-8 column with an acetonitrile water eluent and UV detection at 200 nm. Of the total cosmetic products investigated, 48% were found to contain 7.3-85.9 ppm of 1,4-dioxane.

Chromatography, High Pressure Liquid↗
PubMed1975

Synthesis of potential adrenergic blocking agents: 2-substituted aminomethylnaphthol(2,3-b)-1,4-dioxans.

Eleven 2-substituted aminomethylnaphtho(2,3-b)-1,4-dioxans were synthesized. The nucleophilic displacement of 2-tosyloxymethylnaphtho(2,3-b)-1,4-dioxan by appropriate amines was carried out using dimethyl sulfoxide as the solvent. Preliminary pharmacological evaluation revealed a potentiation of norepinephrine at low doses and a noncompetitive antagonism at high doses in the rat vas deferens and a dose-related hypotensive action of short duration in the anesthetized rat.

Adrenergic beta-Antagonists↗
PubMedDate not supplied

The disposition of l-3-[(dimethylamino)-(m-dioxan-5-yl)methyl]pyridine in man.

l-3-[(Dimethylamino)-(m-dioxan-5-yl)methyl]pyridine hydrochloride (LY 108380) is being evaluated in man as a potentially useful, nonaddicting analgesic agent. This substituted dioxane is structurally different from any currently known analgesic. Following im administration of the 14C-labeled compound to healthy volunteers, the drug was absorbed rapidly (t1/2(abs) = 2--20 min). Pharmacokinetic analyses suggested that LY 108380 was widely distributed and extensively bound in tissues. The drug was not bound to plasma proteins in vitro or in vivo. In the blood, radioactivity was distributed in both red cells and plasma; a cell/plasma radioactivity ratio of 0.5 was maintained for about 1 hr. The t1/2 for elimination of LY 108380-14C from plasma was about 1.3 hr, although radioactivity persisted in plasma for over 100 hr. At the time of peak radioactivity, the parent compound was the major constituent in plasma; quaternary N-glucuronide and N-desmethylated metabolites were also detected in plasma. Levels of radioactivity in saliva were 2--5 times higher than those in plasma shortly after drug administration. About 82% of the radioactivity was eliminated in the urine, 6% in expired air (as 14CO2), and 1% in feces. The major metabolite of LY 108380 (55% of the dose) was a quaternary amine formed by glucuronidation at the pyridine nitrogen. Less than 10% of the dose was N-demethylated to secondary and primary amines, and about 2% was excreted unchanged.

Adult↗
PubMed1978

Mortality follow-up of workers exposed to 1,4-dioxane.

As a result of recent interest in the carcinogenic effect of dioxane, a mortality study was conducted on employees exposed to this compound at a major chemical company plant. Standard follow-up techniques were used to ascertain the vital status of a total of 165 employees ever exposed to dioxane since 1954. Observed deaths from overall cancer were not significantly different from the expected number of deaths. The observations were based on small numbers of deaths of employees who were apparently exposed at low levels and for relatively short exposures.

Adult↗
PubMed1990

Acrylated phosphonate esters containing 1,3-dioxane and 1,3-dioxolane moieties as adhesion-promoting agents for dentin and hard tissues, I.

Novel acrylated phosphonate esters containing 1,3-dioxane and 1,3-dioxolane moieties derived from polyols such as glycerol, D-mannitol, D-sorbitol, pentaerythritol, and dipentaerythritol have been evaluated in vitro for their role as adhesion-promoting agents in composites employed for restorative dentistry. Some of the acrylated phosphonate esters have been found to promote strong bonding to dentin; the dipentaerythritol derivative exhibits a bond strength of approximately 960 psi (7 MPa) which compares favorably to commercial dentin adhesive systems. The bonding agents appear to act in multifunctional ways: the phosphonate group of the monomer chelates the calcium ions of hydroxyapatite at the dentin surface, ethereal oxygen atoms of 1,3-dioxolane or 1,3-dioxane moieties interact with the proteinaceous content of collagen, and the methacrylic fragment copolymerizes concomitantly with the other comonomers of the restorative composite material. Methods of preparing radiopaque adhesion-promoting acrylated phosphonates are also discussed.

Acrylates↗
PubMed2006

Hybrid density functional theory study of fragment ions generated during mass spectrometry of 1,3-dioxane derivatives.

It was recently reported that the cis,cis and trans,trans diastereoisomers of four 2(r)-R-2,4(R),6(S)-trimethyl-1,3-dioxane derivatives show distinct electron ionization mass spectra. As a possible explanation for this finding, the authors suggested that the ions generated during the mass spectrometry of these compounds could follow different fragmentation patterns that initiate from different ion conformations. In this report, hybrid density functional theory methods have been used to investigate the conformational preference of three ions involved in the mass spectrometry of some 1,3-dioxane derivatives. We found that there is indeed more than one stable ion conformation for each of the investigated ions. Energy profiles along the torsional coordinates connecting the conformers are presented, and factors influencing the relative stability of ion conformations are discussed.

Journal Article↗
PubMed1987

Synthesis and neuroleptic activity of a series of 1-[1-(benzo-1,4-dioxan-2-ylmethyl)-4-piperidinyl]benzim idazolone derivatives.

A series of 1-[1-(benzo-1,4-dioxan-2-ylmethyl)-4-piperidinyl]benzimid azolones with various substituents in both aromatic rings have been synthesized and tested for neuroleptic activity (antiapomorphine effects and [3H]spiroperidol binding) as well as extrapyramidal effects (cataleptogenic effect). A strong dependence of activity on the 5-substituent in the benzimidazolone moiety could be demonstrated. Some compounds show a large split between the desired antiapomorphine and the undesired extrapyramidal effect. From these, 1-[1-(benzo-1,4-dioxan-2-ylmethyl)-4-piperidinyl]-5-chlor obenzimidazol-2-one hydrochloride (HR 723), 12, has been selected for further preclinical and toxicological profiling.

Animals↗
PubMed1996

Elucidating the Origin of Conformational Energy Differences in Substituted 1,3-Dioxanes: A Combined Theoretical and Experimental Study.

13C NMR spectroscopy, ab initio quantum mechanics, and molecular mechanics have been used to investigate the trans-4-(trifluoromethyl)-2,2,6-trimethyl-1,3-dioxane chair/twist-boat equilibrium. The molecular mechanics calculations were based upon the MM3 and AMBER force fields. A 6-31G basis set was used for the ab initio calculations, and MP2 correlation corrections were applied. Both the ab initio and AMBER molecular mechanics calculations are consistent with the (13)C NMR chemical shift differences for the trans-4-(trifluoromethyl)-2,2,6-trimethyl-1,3-dioxane conformers. The predicted chair to twist-boat equilibrium suggested by the MM3 calculations is not consistent with the experimental data. These results support the suggestion by Howard et al. (Howard, A. E.; Cieplak, P.; Kollman, P. A. J. Comput.Chem. 1995, 16, 243-261) on the critical role of electrostatic interactions in determining the chair/twist-boat equilibrium.

Journal Article↗
PubMed1999

The Effect of a Para Substituent on the Conformational Preference of 2,2-Diphenyl-1,3-dioxanes: Evidence for the Anomeric Effect from X-ray Crystal Structure Analysis(1).

The molecular structures of 2,2-di(para-substituted phenyl)-1,3-dioxanes were elucidated for the first time by X-ray crystallographic analysis, which revealed two important structural features: (1) These compounds have the chair conformation in which electron-withdrawing aryl groups [viz. p-nitro- or p-(trifluormethyl)phenyl] are always axial and electron-donating aryl groups (viz. p-methoxyphenyl) are always equatorial. (2) In these compounds as well as in symmetrically substituted 2,2-diphenyl-1,3-dioxane the axial C(2)-aryl bond is longer than the equatorial C(2)-aryl bond. The axial preference of the electron-withdrawing aryl group was also demonstrated in solution by (1)H and (13)C NMR spectroscopy. The anomeric carbon substituted with an electron-withdrawing aryl group resonates at an unusually high field, as does the aromatic carbon bearing the electron-withdrawing substituent. The observed (13)C NMR data clearly indicate enhanced electron density at these carbons due to the anomeric effect. Semiempirical molecular orbital calculations by the MOPAK PM3 method reproduced the bond lengthening for axial C(2)-aryl, while the heat of formation derived from this calculation failed to support the axial preference of electron-withdrawing aryl groups. The X-ray crystallographic data on the conformational preference and bond lengths at the anomeric carbon, as well as the solution NMR spectroscopic data, clearly indicate the anomeric effect that is best rationalized in terms of stabilizing interaction between the lone-pair electrons on the ring oxygens and the antibonding orbital of the axial C(2)-aryl bond.

Journal Article↗
PubMed2000

Stereoelectronic interactions in cyclohexane, 1,3-dioxane, 1, 3-oxathiane, and 1,3-dithiane: W-effect, sigma(C)(-)(X) <--> sigma(C)(-)(H) interactions, anomeric effect-what is really important?

Stereoelectronic effects proposed for C-H bonds in cyclohexane, 1, 3-dioxane, 1,3-oxathiane, and 1,3-dithiane were studied computationally. The balance of three effects, namely, sigma(C)(-)(X) --> sigma(C)(-)(H)()eq, sigma(C)(-)(H)()eq --> sigma(C)(-)(X), and n(p)(X) --> sigma(C)(-)(H)()eq interactions, was necessary to explain the relative elongation of equatorial C(5)-H bonds. The role of homoanomeric n(p) --> sigma(C(5))(-)(H)()eq interaction is especially important in dioxane. In dithiane, distortion of the ring by long C-S bonds dramatically increases overlap of sigma(C(5))(-)(H)()eq and sigma(C)(-)(S) orbitals and energy of the corresponding hyperconjugative interaction. Anomeric n(p)(X) --> sigma(C)(-)(H)()ax interactions with participation of axial C-H bonds dominate at C(2), C(4), and C(6). The balance of hyperconjugative interactions involving C-H(ax) and C-H(eq) bonds agrees well with the relative bond lengths for all C-H(ax)/C-H(eq) pairs in all studied compounds. At the same time, the order of one-bond spin-spin coupling constants does not correlate with the balance of stereoelectronic effects in dithiane and oxathiane displaying genuine reverse Perlin effect.

Journal Article↗
PubMed2005

Orbital interactions and their effects on 13C NMR chemical shifts for 4,6-disubstituted-2,2-dimethyl-1,3-dioxanes. A theoretical study.

A theoretical study is employed to describe the orbital interactions involved in the conformers' stability, the energies for the stereoelectronic interactions, and the corresponding effects of these interactions on the molecular structure (bond lengths) for cis- and trans-4,6-disubstituted-2,2-dimethyl-1,3-dioxanes. For cis-4,6-disubstituted-2,2-dimethyl-1,3-dioxanes, two LPO --> sigma*C(2)-Me(8) interactions are extremely important and the energies involved in these interactions are in the range 6.81-7.58 kcal mol(-1) for the LP(O)(1) --> sigma*C(2)-Me(8) and 7.58-7.71 kcal mol(-1) for the LP(O)(3) --> sigma*C(2)-Me(8) interaction. These two LP(O) --> sigma*C(2)-Me(8) interactions cause an upfield shift, indicating an increased shielding (increased electron density) of the ketal carbon C(2) as well as the axial Me(8) group in the chair conformation. These LP(O) --> sigma*C(2)-Me(8) hyperconjugative anomeric type interactions can explain the 13C NMR chemical shifts at 19 ppm for the axial methyl group "Me(8)" and 98.5 ppm for the ketal carbon "C(2)". The observed results for the trans derivatives showed that for compounds 2a-c (R = -CN, -C[triple bond]CH, and -CHO, respectively) the chair conformation is predominant, whereas for 2d,f-h [-CH3, -Ph, -C6H4(p-NO2), -C6H4(p-OCH3), respectively] the twist-boat is the most stable compound and for 2e [-C(CH3)3] is the only form.

Journal Article↗
PubMed2005

G3(MP2) study of the C3H6O+* isomers fragmented from 1,4-dioxane+*.

The fragmentation process of ionized 1,4-dioxane and the reactions between the C3H6O+* ions, one of the major fragments, and various reactants (including acetonitrile, formaldehyde, ethylene, and propene) have been studied experimentally with mass spectrometry. In the present work, G3(MP2) calculations were carried out to investigate these processes theoretically. In agreement with experiment, isomers CH3OCHCH2+* (1) and *CH2CH2OCH2+ (2) were found to be the C3H6O+* ions fragmented from ionized 1,4-dioxane, with 2 being the major product. The mechanisms of the formation of 1 and 2 were successfully established. In addition, the characteristic reactivities, as well as the corresponding reaction mechanisms, of both isomers were rationalized with the aid of calculations. Finally, a minor reaction between isomer 2 and propene was identified, and the presence of the product of this reaction was found to be useful in explaining the aforementioned mass spectrometric data.

Journal Article↗
PubMed2001

Optimization of palladium-catalyzed polyene cyclizations: suppression of competing hydride transfer from tertiary amines with Dabco and an unexpected hydride transfer from 1,4-dioxane.

[figure: see text] This paper demonstrates that both 1,2,2,6,6-pentamethylpiperidine (PMP) and 1,4-dioxane can act as hydride donors in palladium-catalyzed polyene cyclizations of 2 and 3. Studies using PMP-d3 and dioxane-d8 either incorporate a deuterium atom into the monosubstituted product or completely inhibit the hydride transfer so that the second ring closure occurs in high yield. Dabco is the best substitute for PMP.

Journal Article↗