Search results for "Hexane"

Preparation and structure of pyrrolo[2,1-b]- and isoindolo[1,2-b][3,1]epoxyquinazolines

2007

Abstract Various γ-oxocarboxylic acids [aroylpropionic acids, cis-2-(4-methylbenzoyl)cyclohexanecarboxylic acid, diendo-3-benzoylbicyclo[2.2.1] heptane-2-carboxylic acid, formylbenzoic acid, methanobenzenecyclooctencarboxylic acid and the cyclopentadiene adduct of 3-trans-(4-methylbenzoyl)acrylic acid] were reacted with diexo-3-aminomethyl-7-oxabicyclo[2.2.1]hept-5-en-2-ylamine 2 to result in condensed pyrroloepoxyquinazolines 3–10. The starting 2 retained the diexo configuration, but cis → trans isomerization took place when cis-2-(4-methylbenzoyl)cyclohexanecarboxylic acid was applied. The structures, including the ring annelations and the position of the aryl group on the new chiral cent…

PDE4 inhibitors as new anti-inflammatory drugs: effects on cell trafficking and cell adhesion molecules expression.

2004

Phosphodiesterase 4 (PDE4) is a major cyclic AMP-hydrolyzing enzyme in inflammatory and immunomodulatory cells. The wide range of inflammatory mechanisms under control by PDE4 points to this isoenzyme as an attractive target for new anti-inflammatory drugs. Selective inhibitors of PDE4 have demonstrated a broad spectrum of anti-inflammatory activities including the inhibition of cellular trafficking and microvascular leakage, cytokine and chemokine release from inflammatory cells, reactive oxygen species production, and cell adhesion molecule expression in a variety of in vitro and in vivo experimental models. The initially detected side effects, mainly nausea and emesis, appear at least pa…

Novel σ1 antagonists designed for tumor therapy: Structure – activity relationships of aminoethyl substituted cyclohexanes

2021

Abstract Depending on the substitution pattern and stereochemistry, 1,3-dioxanes 1 with an aminoethyl moiety in 4-position represent potent σ1 receptor antagonists. In order to increase the stability, a cyclohexane ring first replaced the acetalic 1, 3-dioxane ring of 1. A large set of aminoethyl substituted cyclohexane derivatives was prepared in a six-step synthesis. All enantiomers and diastereomers were separated by chiral HPLC at the stage of the primary alcohol 7, and their absolute configuration was determined by CD spectroscopy. Neither the relative nor the absolute configuration had a large impact on the σ1 affinity. The highest σ1 affinity was found for cis-configured benzylamines…

η⇌μ exchange bonding mode of bidentate tmeda ligand. Molecular structure of [Y(tmhd)3]2(μ-tmeda)

2003

Abstract The reaction between the yttrium β-diketonate complexes Y(tmhd)3(H2O)x (x=0 or 1) and 0.5 or 1 equivalent of N,N,N′,N′-tetramethylethylenediamine (tmeda=Me2NCH2CH2NMe2) in hexane at room temperature afforded [Y(tmhd)3]2(tmeda) (1) and Y(tmhd)3(tmeda) (2) derivatives, respectively. They have been characterized by FT-IR, 1H NMR spectroscopy and by single crystal X-ray diffraction for 1. Variable temperature 1H NMR experiments indicated an equilibrium between 1 and 2. Their thermal behaviors were characterized by TGA and sublimation experiments. 2 is converted into compound 1 by heating over 100 °C. These precursors were used for the growth of Y2O3 and YBa2Cu3O7 − x films by pulsed in…

Direct determination of benzene in gasoline by flow-injection Fourier transform infrared spectrometry

1993

Abstract A Fourier transform infrared spectrometric procedure for the automated determination of benzene in gasoline was developed, based on the use of flow-injection analysis. The method permits the direct determination of benzene without any pretreatment of samples, with a limit of detection of 0.02% (v/v) and a relative standard deviation of ca. 1% [for five independent analyses of a diluted sample containing a 0.4% (v/v) of benzene]. Results found by direct analysis agreed with those obtained by off-line and on-line standard addition methods. A rapid quality control procedure was developed, based on the on-line injection of gasoline samples (diluted 1 + 9 in hexane) into a carrier strea…

Application of ACC method to synchronous luminiscence: determination of alpha-tocopherol and alpha-tocopheryl acetate in beverages.

2001

A new method based on the Q parameter, that permits the determination of the C(compound A)/C(compound B) ratio without preparing calibration graphs of the two compounds, is proposed. This method has been applied to signals obtained by synchronous luminiscence. Simultaneous determination of alpha-tocopherol and alpha-tocopheryl acetate in beverages using synchronous fluorescence has been carried out. To isolate the compounds from samples, liquid extraction with n-hexane as the organic phase was employed. The presence of interferences was tested using the apparent content curves (ACC) method and the C(alpha-tocopherol)/C(alpha-tocopheryl acetate) ratio was calculated using the Q parameter. Th…

A rapid HPLC assay for zearalenone in laboratory cultures ofFusarium graminearum

1993

A high pressure liquid chromatographic (HPLC) method to determine zearalenone in corn contaminated withFusarium graminearum is described. After extraction with methanol-water and solvent partition, samples were cleaned up by applying the extract to a disposable silica cartridge and by eluting the toxin with a mixture of hexane/dry ethyl ether (5/5). Separation was achieved by a reverse phase μBondapak C18 column followed by fluorescence detection using an excitation wavelength at 274 nm and an emission wavelength at 440 nm. Detection limit was about 5 ng. Recoveries ranging from 85.37 to 100.97%, in standard solutions range 30–0.5 µg/ml, were found.

Simultaneous clean up of fish fat containing low levels of residues and separation of PCB from chlorinated pesticides by thin-layer chromatography

1974

Selective guest inclusion of linear C6 hydrocarbons in a Zn(ii) 1D coordination polymer

2021

Trapping of volatile unbranched C6 hydrocarbons (hexane, 1-hexene, and 1-hexyne) in a 1D coordination polymer is reported. The guest inclusion was studied quantitatively by 1H-NMR analysis and thermogravimetric measurements, while synchrotron single-crystal diffraction data allowed advancing the view of their confinement into linear CP channels. Adsorption experiments performed through solid/vapour processes on microcrystals of CP 1 showed a certain degree of selectivity for 1-hexyne, which could be rationalized by its larger dipole moment.

Theoretical and structural studies of lithium cyclic amide conformations. Monomers and aggregates

2000

High level ab initio calculations on the conformations of unsolvated and solvated lithium piperidide, 1, and lithium morpholide, 2, were carried out. It was found that both monomers exhibit a global minimum for a chair structure with a planar nitrogen, and 2 shows an additional stable pseudo boat conformation. Dimers and amine–lithium amide mixed aggregates were also calculated including discrete solvation; the role of aggregation is clearly shown both by the changes in geometries and in the stabilization energies. Semiempirical calculations carried out on a recently synthesized tetrameric mixed aggregate give a geometry very similar to the structure determined by X-ray diffraction. The pre…