Search results for "Polycyclic Compounds"
showing 10 items of 373 documents
Preparation of 2,3-seco-5α-cholestane-2,3-diol and 4α-methyl-2,3-seco-5α-cholestane-2,3-diol and its reactions with o-nitrophenyl selenocyanate
1984
The reaction of 2,3-seco-5 alpha-cholestane-2,3-diol and 4 alpha-methyl-2,3-seco-5 alpha-cholestane-2,3-diol with o-nitrophenyl selenocyanate was studied. The diols were synthesized from cholesterol.
Influence of radiation defects on tritium release parameters from Li2O
1998
Abstract The study of the influence of radiation defects on tritium release behavior from polycrystalline Li2O was performed by simultaneous measurements of the luminescence emission and tritium release. It was found that the radiation defects in Li2O introduced by electron irradiation cause the retention of tritium. It is thought that the tritium recovery is affected by the formation of a Li–T bond, which is tolerant of high temperatures. The retardation of tritium decreases with increasing absorbed dose in the dose range from 50 to 140 MGy. The aggregation of radiation defects at high irradiation doses is considered to be responsible for the decrease of the interaction of tritium with rad…
Oxidation of aminodiols mediated by homogeneous and heterogeneous TEMPO
2004
The conversion of amino diols to aminohy- droxy acids by oxidation of the primary hydroxy group mediated by homogeneous and heterogeneous TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl radi- cal) is reported. The synthesis uses NaOCl as primary oxidant and TEMPO, either dissolved in the homoge- neous phase or entrapped in a sol-gel matrix, as cata- lytic mediator. Homogeneous TEMPO is suitable for the oxidation of aliphatic methylamino diols, while the hybrid organic-inorganic silica sol-gel catalysts are more selective mediators for the oxidation of ben- zylic amino diols like the potent antibiotic chloram- phenicol which, under homogeneous conditions, are unselectively oxidized to benzoic ac…
Synthesis of 2,4,6-trisubstituted tetrahydropyrans via 6-exo selenoetherification of unsaturated alcohols
2001
Stereoselectivity, regioselectivity and yields in the 6-exo selenoetherification of four unsaturated diols were found to depend on the stereochemistry of the diols and on the presence of an oxygen atom close to the intermediate seleniranium ring. Silica gel was useful in order to obtain good yields. Reactions performed both under kinetic and thermodynamic control led to the same products. Stereoselectivity, regioselectivity and yields in the 6-exo selenoetherification of four unsaturated diols were found to depend on several factors such as the stereochemistry of the diols, the nature of the R group, the nature of the counter anion of the PhSe+ species and the presence of silica gel.
Coordination-Induced Spin-State Switching with Nickel Chlorin and Nickel Isobacteriochlorin
2015
We present the first coordination-induced spin-state switching with nickel chlorin and nickel isobacteriochlorin. The spin-state switching was monitored by UV-vis spectroscopy and NMR titration experiments. The association constants (K1 and K2) and thermodynamic parameters (ΔH and ΔS) of the coordination of pyridine were determined. The first X-ray analyses of a paramagnetic nickel chlorin and a nickel isobacteriochlorin provide further information about the structure of the octahedral complexes. Nickel chlorin and even more pronounced nickel isobacteriochlorin exhibit stronger coordination of axial ligands compared to the corresponding nickel porphyrin and thus provide the basis for more e…
Novel method for determination of tritium depth profiles in metallic samples
2019
Tritium accumulation in fusion reactor materials is considered a serious radiological issue, therefore a lot of effort has been concentrated on the development of radiometric techniques. A novel method, based on gradual dissolution, for the determination of the total tritium content and its depth profiles in metallic samples is demonstrated. This method allows for the measurement of tritium in metallic samples after their exposure to a hydrogen and tritium mixture, tritium containing plasma or after irradiation with neutrons resulting in tritium formation. In this method, successive layers of metal are removed using an appropriate etching agent in the controlled regime and the amount of evo…
Synthese mehrerer polymerhomologer reihen von diol-oligo-urethanen. Synthese von makromolekeln einheitlicher größe. V. Mitt.
1961
Mit Hilfe des Duplikationsverfahrens und durch schrittweise Synthese werden mehrere polymerhomologe Reihen von Diol-oligo-urethanen synthetisiert. Die Anwendbarkeit dieser Methode wird eingehend diskutiert. Die Diol-oligo-urethane werden durch Endgruppenanalyse charakterisiert. Several homologous polymeric series of diol-oligo-urethanes are prepared by the method of duplication and by synthesis step by step. The application of these methods is discussed thoroughly. The diol-oligo-urethanes are characterized by end-group analysis.
Dietary cholic acid lowers plasma levels of mouse and human apolipoprotein A-I primarily via a transcriptional mechanism
2000
To induce dietary atherosclerosis in mice, high-fat/high-cholesterol (HF) diets are frequently supplemented with cholic acid (CA). This diet produces low plasma levels of high-density lipoprotein (HDL) and high levels of low-density lipoprotein (LDL). However, HF diets without any added CA, which more closely resemble human diets, increase levels of both HDL and LDL, suggesting that CA may be responsible for the lowering of HDL. Our aim was to examine the potential mechanism responsible for the lowering of HDL. Nontransgenic (NTg) C57BL mice and apoA-I-transgenic (apoAI-Tg) mice, with greatly increased basal apoA-I and HDL levels, were used. Mice were fed the following four diets: control (…
Free and sulfoconjugated dehydroepiandrosterone, cyclic adenosine-3′,5′-monophosphate, and free estriol in maternal and cord blood
1976
When free DHEA, its sulfatide, and sulfate were assayed in maternal plasma as well as in umbilical cord arterial and venous plasma, rather high concentrations were found in either fraction from cord arterial plasma, reflecting the fetal contribution not only of free DHEA and DHEA sulfate, but also of the lipophile steroid sulfatide. Since high DHEA levels were associated with elevated c-AMP concentrations, a certain interrelationship of both parameters is indicated. In the course of delivery, a rapid decrease of free estriol in maternal plasma was observed. Higher concentration of free estriol in umbilical venous plasma pointed at its placental biosynthesis from fetal precursors.
Digoxin-related leukocytoclastic vasculitis in a very elderly woman: A case report
2016
International audience; Even though digoxin causes many side effects, few cases of skin involvement are recorded in the French Pharmacovigilance Database. We report a case of leukocytoclastic vasculitis (LV) very probably due to digoxin. A 91-year-old woman, hospitalized following a fall, presented cardiac decompensation in a context of rapid atrial fibrillation requiring treatment with digoxin. Eight days later, a rash appeared on her back and trunk. It was neither itchy, nor painful and persisted despite local treatment. There were no other clinical anomalies. After a few days, the rash spread with appearance of bullous lesions, ulcerations and a necrosis on lymphedema of the two legs. Am…