No description available.

No description available.

München, Techn. Univ., Diss., 2008.

Experimental studies showed the feasibility of adding metallic catalysts and tetralin for the upgrade and increased recovery of heavy oil during the in situ combustion process. Further experimental studies also showed the applicability of in situ combustion as a viable method of upgrading and improving recovery of intermediate oils. Three successful experimental runs were performed with heavy oil from Mexico (10.1 degrees API gravity). The first run was the control run without the addition of tetralin or metallic catalysts; the second run used heavy oil premixed with 3 wt% tetralin and 500ppm nickel catalyst; and the third run was with heavy oil premixed with 3 wt% tetralin and 500ppm iron catalyst. For the three runs, the cell production pressure was kept constant at 300 psig. The combustion cell was placed in a vacuum jacket and set to a temperature of 60 degrees C. For the only successful run with the intermediate Texas oil (22.0 degrees API gravity), the production pressure was also kept constant at 300 psig but the vacuum jacket temperature was set to a reservoir temperature of 40oC. During the runs for both oils, samples of produced oils and combustion flue gases were collected at regular intervals for analysis. These analyses included determination of oil viscosity and density, oil recovery, combustion front velocity, and apparent H/C ratio. Experimental results for the intermediate oil run, the oil gravity increased by 6 points showing the upgrading effects of in situ combustion on intermediate oils. Also, the high average combustion temperatures observed during the run indicated that in situ combustion may be applicable to reservoirs of similar characteristics to the intermediate Texas oil reservoir. Heavy oil experimental run results indicated that the use of tetralin and metallic catalysts increase the average combustion front temperature from 484 degrees C to 501 degrees C for the run with nickel catalysts, and from 484 degrees C to 492 degrees C for the run with iron catalysts. These results also show an increase in produced oil recovery from 83% to 90% of oil initially in place for the nickel catalyst run, and 83% to 86% of oil initially in place for the iron catalyst run.

No description available.

No description available.

<p>Delivery of drugs to the brain requires passage across the blood-brain barrier (BBB). Both for drugs already on the market and for new drugs under development, it is important to know to what extent a drug enters the CNS. Many drugs used clinically are racemic mixtures, <i>i.e.</i> equal parts of the (<i>S</i>)- and (<i>R</i>)-enantiomers. </p><p>The present studies focus on the enantiomers and racemates of a number of 5-HT_1A receptor agonists and antagonists (pindolol, propranolol, 8-OH-DPAT and other 8-substituted-2-(di-<i>n</i>-propylamino)tetralin derivatives) and BBB transport <i>in vitro</i> and distribution to the brain <i>in vivo.</i> Assays (HPLC-based) were set up or developed for determination of the racemates and the pure enantiomers (chiral column) of drugs in plasma and brain tissue. BBB transport was assessed <i>in vitro</i> using bovine brain endothelial cells cocultured with rat astrocytes. The physicochemical constants (log P, pKa) and plasma protein binding were determined. Pindolol, propranolol and several tetralines accumulated over time in brain tissue. For pindolol and propranolol, but not for most tetralins, the distribution to the brain was stereoselective, (<i>S</i>)>(<i>R</i>). Pretreatment with verapamil, an inhibitor of drug efflux <i>via</i> P-glycoprotein, differentially decreased the brain/plasma ratios of the enantiomers of pindolol and propranolol, indicating that verapamil may also inhibit an influx transport mechanism. <i>In vitro</i> results with racemic pindolol, propranolol and tetralins showed no differences in BBB transport between the enantiomers. A more rapid apical to basolateral transport (influx) <i>vs</i>. the basolateral to apical (efflux) transport of propranolol (not pindolol) and most tetralins <i>in vitro</i> indicated active transport across the BBB. </p><p>In conclusion, the combined <i>in vivo</i> and <i>in vitro</i> results are consistent with active transport of the studied compounds across the BBB rather than passive diffusion due to their lipophilicity. Some, but not all, chiral drugs are stereoselectively distributed to the brain. Stereoselective plasma protein binding or stereoselective transport across brain endothelial cells does not seem to explain the stereoselective accumulation of pindolol and propranolol. The stereochemical configuration of compounds contributes to their pharmacokinetic as well as their pharmacodynamic uniqueness. The characteristics of the enantiomers of chiral compounds need to be determined empirically rather than based on generalizations from structural or physicochemical information.</p>

Delivery of drugs to the brain requires passage across the blood-brain barrier (BBB). Both for drugs already on the market and for new drugs under development, it is important to know to what extent a drug enters the CNS. Many drugs used clinically are racemic mixtures, i.e. equal parts of the (S)- and (R)-enantiomers. The present studies focus on the enantiomers and racemates of a number of 5-HT1A receptor agonists and antagonists (pindolol, propranolol, 8-OH-DPAT and other 8-substituted-2-(di-n-propylamino)tetralin derivatives) and BBB transport in vitro and distribution to the brain in vivo. Assays (HPLC-based) were set up or developed for determination of the racemates and the pure enantiomers (chiral column) of drugs in plasma and brain tissue. BBB transport was assessed in vitro using bovine brain endothelial cells cocultured with rat astrocytes. The physicochemical constants (log P, pKa) and plasma protein binding were determined. Pindolol, propranolol and several tetralines accumulated over time in brain tissue. For pindolol and propranolol, but not for most tetralins, the distribution to the brain was stereoselective, (S)&gt;(R). Pretreatment with verapamil, an inhibitor of drug efflux via P-glycoprotein, differentially decreased the brain/plasma ratios of the enantiomers of pindolol and propranolol, indicating that verapamil may also inhibit an influx transport mechanism. In vitro results with racemic pindolol, propranolol and tetralins showed no differences in BBB transport between the enantiomers. A more rapid apical to basolateral transport (influx) vs. the basolateral to apical (efflux) transport of propranolol (not pindolol) and most tetralins in vitro indicated active transport across the BBB. In conclusion, the combined in vivo and in vitro results are consistent with active transport of the studied compounds across the BBB rather than passive diffusion due to their lipophilicity. Some, but not all, chiral drugs are stereoselectively distributed to the brain. Stereoselective plasma protein binding or stereoselective transport across brain endothelial cells does not seem to explain the stereoselective accumulation of pindolol and propranolol. The stereochemical configuration of compounds contributes to their pharmacokinetic as well as their pharmacodynamic uniqueness. The characteristics of the enantiomers of chiral compounds need to be determined empirically rather than based on generalizations from structural or physicochemical information.

L'objectif de ce travail était double : obtenir des informations sur le lien structure/réactivité dans les nanoalliages et évaluer l'impact de l'addition d'or sur les propriétés catalytiques de métaux actifs en hydrogénation. Des nanoparticules bimétalliques Au-Pd et Au-Rh ont été synthétisées et supportées principalement sur des nanobâtonnets TiO2 rutile, caractérisées par différentes techniques d'analyse (DLS, UV-Vis, HR-(S)TEM, XRD, XPS et CO-FTIR), et évaluées dans deux réactions d'hydrogénation. Les catalyseurs modèles ont été principalement préparés par voie colloïdale suivie d'une immobilisation sur le support et d'un post-traitement consistant à éliminer le surfactant sans détruire la structure des nanoparticules. Les particules Au-Pd (3-5 nm) possèdent une structure alliée de type solution solide. La structure des particules Au-Rh (3-5 nm), système immiscible en volume, est plus hétérogène, avec différentes configurations en fonction du post-traitement effectué : coeur-coquille, ségrégation de phases de type « Janus » et alliage à l'échelle atomique en faible proportion. Les catalyseurs bimétalliques ont été testés en hydrogénation de la tétraline en présence de soufre et en hydrogénation sélective du cinnamaldéhyde, dans les deux cas sous haute pression d'hydrogène, et comparés à leurs homologues monométalliques. En hydrogénation du cinnamaldéhyde, un effet considérable du traitement post-synthèse sur l'activité et sélectivité est mis en évidence. Les catalyseurs fraichement synthétisés montrent une sélectivité élevée en hydrocinnamaldéhyde alors que les traitements de réduction et de calcination-réduction diminuent l'activité pour les échantillons AuRh les plus riches en Rh. En hydrogénation de la tétraline, l'alliage avec l'or a pour effet de diminuer l'activité mais d'améliorer la stabilité des systèmes à base de Pd et Rh en présence de soufre, en augmentant, par effet électronique, la barrière de chimisorption du soufre ou de sulfuration / The objectives of this work were to gain an insight into the structure-selectivity relationships in nanoalloys and to evaluate the impact of gold addition on the catalytic properties of active metals in hydrogenation reactions. For this purpose, bimetallic Au-Pd and Au-Rh nanoparticles were synthesized and supported (mostly) on rutile TiO2 nanorods before being structurally characterized by various techniques (DLS, UV-Vis, HR-(S)TEM, XRD, XPS, and CO-FTIR) and evaluated in two hydrogenation reactions. The model catalysts were mainly prepared using a colloidal method and immobilized on the support. Post-treatments were carried out in order to eliminate the surfactant used during the synthesis, with minimal impact on the nanoparticle structure. The influence of the synthesis parameters on the nanoparticle structure and catalytic properties was evaluated. The Au-Pd particles (3-5 nm) exhibit an alloyed solid solution structure. The structure of the bulk-immiscible Au-Rh particles (3-5 nm) is more heterogeneous, with several structural configurations depending on the post-treatment: core-shell, Janus-type phase segregation, and atomic-scale alloyed structure to a small extent. The catalysts were tested for tetralin hydrogenation in the presence of sulfur (0-100 ppm H2S) and for the selective hydrogenation of cinnamaldehyde, both under high hydrogen pressure. The bimetallic systems were compared to their monometallic counterparts. The post-synthesis treatments have a dramatic impact on activity and selectivity in cinnamaldehyde hydrogenation. The fresh catalysts exhibit a high selectivity toward hydrocinnamaldehyde, whereas reduction and calcination-reduction mainly decrease the activity of Rh-rich Au-Rh samples. For tetralin hydrogenation, gold decreases the activity but improves the stability of Pd and Rh-based systems in the presence of sulfur through electronic effects increasing sulfur chemisorption or sulfidation barriers

Furo[3,4-c] pyranone is a unique bicyclic molecular structure found in bioactive sesquiterpene isobolivianine and in artificial cytotoxic stilbene derivatives. The structure of furo[3,4-c] pyranone is analogous to cyclopenta[c] pyran structure found in potent cytotoxic iridoids like catapol. Chiral substrates for intramolecular hetero-Diels-Alder (IHDA) reaction have been synthesized in yields ranging from 39% to 81%. These compounds undergo [4+2] cycloaddition via ambimodal/ bispericyclic process to give a mixture of furo[3,4-c] pyranone in yields ranging 40-70% and aryl tetralin lactone derivatives. Density functional theory (DFT) calculations have been performed to gain insight into the mechanism leading to the formation of these compounds. Podophyllotoxins are aryl tetralin lignans with great potential as lead compounds for anti-cancer and antibiotic agents. The bioactivity of these compounds is attributed to their unique stereochemistry that is not easy to synthesize. Chiral substrates for intramolecular dehydro-Diels-Alder (IDDA) reaction have been synthesized in moderate yields. These novel compounds have been used to synthesize aryl tetralin lactone cores by IDDA reaction. This work demonstrates the potential utility of asymmetric IHDA and IDDA reactions in the total synthesis of bioactive compounds featuring furo[3,4-c] pyranone core and aryl tetralin lactones found in anticancer podophyllotoxins.