A DFT Guided/Experimental Approach to Asymmetric Allylation and Phase-Transfer Catalysis

The Dudding group is interested in the application of Density Functional Theory (DFT) in developing asymmetric methodologies, and thus the focus of this dissertation will be on the integration of these approaches. Several interrelated subsets of computer aided design and implementation in catalysis have been addressed during the course of these studies. The first of the aims rested upon the advancement of methodologies for the synthesis of biological active C(1)-chiral 3-methylene-indan-1-ols, which in practice lead to the use of a sequential asymmetric Yamamoto-Sakurai-Hosomi allylation/Mizoroki Heck reaction sequence. An important aspect of this work was the utilization of ortho-substituted arylaldehyde reagents which are known to be a problematic class of substrates for existing asymmetric allylation approaches. The second phase of my research program lead to the further development of asymmetric allylation methods using o-arylaldehyde substrates for synthesis of chiral C(3)-substituted phthalides. Apart from the de novo design of these chemistries in silico, which notably utilized water-tolerant, inexpensive, and relatively environmental benign indium metal, this work represented the first computational study of a stereoselective indium-mediated process. Following from these discoveries was the advent of a related, yet catalytic, Ag(I)-catalyzed approach for preparing C(3)-substituted phthalides that from a practical standpoint was complementary in many ways. Not only did this new methodology build upon my earlier work with the integrated (experimental/computational) use of the Ag(I)-catalyzed asymmetric methods in synthesis, it provided fundamental insight arrived at through DFT calculations, regarding the Yamamoto-Sakurai-Hosomi allylation. The development of ligands for unprecedented asymmetric Lewis base catalysis, especially asymmetric allylations using silver and indium metals, followed as a natural extension from these earlier discoveries. To this end, forthcoming as well was the advancement of a family of disubstituted (N-cyclopropenium guanidine/N-imidazoliumyl substituted cyclopropenylimine) nitrogen adducts that has provided fundamental insight into chemical bonding and offered an unprecedented class of phase transfer catalysts (PTC) having far-reaching potential. Salient features of these disubstituted nitrogen species is unprecedented finding of a cyclopropenium based C-H•••πaryl interaction, as well, the presence of a highly dissociated anion projected them to serve as a catalyst promoting fluorination reactions. Attracted by the timely development of these disubstituted nitrogen adducts my last studies as a PhD scholar has addressed the utility of one of the synthesized disubstituted nitrogen adducts as a valuable catalyst for benzylation of the Schiff base N-diphenyl methylene glycine ethyl ester. Additionally, the catalyst was applied for benzylic fluorination, emerging from this exploration was successful fluorination of benzyl bromide and its derivatives in high yields. A notable feature of this protocol is column-free purification of the product and recovery of the catalyst to use in a further reaction sequence.

Antidiabetic activity of Vaccinium vitis-idaea, a medicinal plant from the traditional pharmacopeia of the James Bay Cree

L’incidence du diabète chez les premières nations du Canada est plus de trois fois celle du reste du pays, dû, en partie, aux traitements culturellement inappropriés. Notre projet vise à traiter le diabète chez ces populations à partir de leur pharmacopée de médicine traditionnelle afin d’améliorer l’acceptation des traitements. En utilisant une approche ethnobotanique, notre équipe a identifié 17 plantes médicinales utilisées pour traiter des symptômes du diabète par les Cris d'Eeyou Istchee (Baie James, Québec). Parmi eux, l'extrait éthanolique de baies de Vaccinium vitis-idaea a montré un effet stimulateur sur le transport du glucose dans les cellules musculaires squelettiques et les adipocytes en culture. Le but de cette thèse était d’élucider les mécanismes par lesquels cet extrait exerce ses effets anti-hyperglycémiants, d’identifier ses principes actifs et de confirmer in vivo, son efficacité. Les résultats démontrent que V.vitis a augmenté le transport du glucose dans les cellules musculaires en cultures, C2C12 et L6 et a stimulé la translocation des transporteurs GLUT4 dans les cellules L6. L'extrait a également inhibé la respiration dans les mitochondries isolées du foie du rat. Cet effet est semblable à celui de la metformine et en lien avec la production du stress métabolique et l'activation de l'AMPK. De plus, la voie de signalisation de l’insuline ne semble pas être impliquée dans le mécanisme d’action de V. vitis. Le fractionnement guidé par la stimulation du transport du glucose a mené à l'isolation des principes actifs; la quercétine, la quercétine-3-O-galactoside, et la quercétine-3-O-glucoside. Comparable à l'extrait brut, ses composés ont stimulé la voie AMPK. Cependant, la quércetine était la seule à inhiber la respiration mitochondriale. Pour valider l'effet de V.vitis in vivo, l'extrait (1% dans l'eau de boisson) a été administré aux souris KKAy pendant 10 jours. La glycémie et le poids corporel ont été significativement réduits par V.vitis. Ces effets ont été associés à une diminution de la prise alimentaire, ce qui suggère que V.vitis diminue l'appétit. L'étude pair-fed a confirmé que les effets de V.vitis sont, majoritairement, dû à la réduction de l’appétit. De plus, V.vitis a augmenté la teneur en GLUT4 dans le muscle squelettique, a stimulé la iv phosphorylation de l'ACC et a augmenté les niveaux de PPAR-α dans le foie des souris KKAy. Ces effets se voient être additifs à l’effet anorexigène de V. vitis. Au cours du fractionnement bioguidé de l’extrait, l’ester méthylique de l'acide caféique (CAME), un produit formé lors de la procédure du fractionnement, a démontré un effet stimulateur puissant sur le transport du glucose dans les celules C2C12 et donc un potentiel anti-diabétique. Pour identifier d'autres acides caféique active (AC) et pour élucider leurs relations structure-activité et structure-toxicité, vingt dérivés AC ont été testés. Outre CAME, quatre composés ont stimulé le transport du glucose et ont activé l'AMPK suite au stress métabolique résultant d'un découplage de la phosphorylation oxydative mitochondriale. L’activité nécessite une fonction d’AC intacte dépourvu de groupements fortement ionisés et ceci était bien corrélée avec la lipophilicite et la toxicité. Les résultats de cette thèse soutiennent le potentiel thérapeutique de V. vitis, ses composés actifs ainsi que de la famille de l’AC et pour la prévention et le traitement du diabète.

Efficacité et toxicité de l'eugénol administré à des doses anesthésiantes chez des grenouilles Xenopus laevis.

L’eugénol permet d’induire une anesthésie chirurgicale chez la grenouille africaine à griffes (Xenopus laevis) sans causer de lésions chez des grosses grenouilles (90-140g). Le premier objectif de la présente étude était de déterminer la durée de l’anesthésie et d’évaluer la dépression du système nerveux central ainsi que les changements de saturation en oxygène et de fréquence cardiaque chez des petites (7.5 ± 2.1 g) et moyennes (29.2 ± 7.4 g) grenouilles Xenopus laevis en fonction du temps d’exposition à un bain d’eugénol de 350 µL/L. Suite à une immersion de 5 ou 10 minutes, la réponse au test à l’acide acétique, au réflexe de retrait et au réflexe de retournement était absente pendant 1 heure (petites grenouilles) et 0,5 heure (moyennes) et l’anesthésie chirurgicale durait au maximum 15 et 30 minutes chez les petites et moyennes grenouilles respectivement. La saturation en oxygène n’était pas affectée de façon significative, mais la fréquence cardiaque était diminuée jusqu’à 1 heure post-immersion dans les deux groupes. Le deuxième objectif était de déterminer la toxicité de l’eugénol chez des grenouilles de taille moyenne après une ou trois administrations à une dose anesthésique, avec ou sans période de récupération d’une semaine. Histologiquement, il y avait de l’apoptose tubulaire rénale et des membranes hyalines pulmonaires après une administration, et de la nécrose hépatique et des hémorragies dans les tissus adipeux après trois administrations. Ces résultats suggèrent que le poids corporel est un paramètre important à considérer lors de l’anesthésie de grenouilles Xenopus laevis par immersion dans l’eugénol.

Acute insult of ammonia leads to calcium-dependent glutamate release from cultured astrocytes, an effect of pH.

Hyperammonemia is a key factor in the pathogenesis of hepatic encephalopathy (HE) as well as other metabolic encephalopathies, such as those associated with inherited disorders of urea cycle enzymes and in Reye's syndrome. Acute HE results in increased brain ammonia (up to 5 mM), astrocytic swelling, and altered glutamatergic function. In the present study, using fluorescence imaging techniques, acute exposure (10 min) of ammonia (NH4+/NH3) to cultured astrocytes resulted in a concentration-dependent, transient increase in [Ca2+]i. This calcium transient was due to release from intracellular calcium stores, since the response was thapsigargin-sensitive and was still observed in calcium-free buffer. Using an enzyme-linked fluorescence assay, glutamate release was measured indirectly via the production of NADH (a naturally fluorescent product when excited with UV light). NH4+/NH3 (5 mM) stimulated a calcium-dependent glutamate release from cultured astrocytes, which was inhibited after preincubation with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester but unaffected after preincubation with glutamate transport inhibitors dihydrokainate and DL-threo-beta-benzyloxyaspartate. NH4+/NH3 (5 mM) also induced a transient intracellular alkaline shift. To investigate whether the effects of NH4+/NH3 were mediated by an increase in pH(i), we applied trimethylamine (TMA+/TMA) as another weak base. TMA+/TMA (5 mM) induced a similar transient increase in both pH(i) and [Ca2+]i (mobilization from intracellular calcium stores) and resulted in calcium-dependent release of glutamate. These results indicate that an acute exposure to ammonia, resulting in cytosolic alkalinization, leads to calcium-dependent glutamate release from astrocytes. A deregulation of glutamate release from astrocytes by ammonia could contribute to glutamate dysfunction consistently observed in acute HE.

Polyunsaturated Fatty Acids (PUFA) Regulate Neurotransmitter Contents in Rat Brain

The effects of feeding of 6-propyllhiouracil (6-I'fU) and potyunsaturatcd fatty acids (I'UFA) independently and ill combination and administration (ip) of a single close of Iriiodothyronine (I',) (2.51ig/IOOg body wl) along with feeding of 6- PTU and PUFA were studied in cal brain. Dopamine (DA), 5-hydroxytryplophan (5-IIl'I'), serolouin (5-Ill), 5-hydioxy indole acetic acid (5-111AA), norepinephrine (NF) :uul ceinephrinn (I?I'l) contenls were assayed in the hypothalannls and ccrc bral cortex regions. It was found that 6-P"l'U Iccding resulted in decrease in dopamine, 5-III', 5 II I I' and 5 IIiAA in both regions. In animals fed wills PUFA followed by adnliuislralion of T,. the I)A level was found normal.

Surface acidity and catalytic activity of sulphated samaria

We have investigated the changes in surface acidity/basicity and catalytic pro~erties of samarium oxide due to surface modification by SO42- ion. The acidity/basicity of the catalysts is determined by titration method using Hammett indicators. Esterification of acetic acid by n-butanol is chosen as a test reaction. Sm203, owing to its high basicity and low acidity, does not catalyze the reaction. But sulphated Sm20J catalyzes the esterification reaction effectively. Activation temperature does not have much effect on the acidity of sulphated samaria.

Surface electron properties and catalytic activity of cerium-zirconium mixed oxides

The electron donating properties, surface acidity/ basicity and catalytic activity of cerium - zirconium mixed oxides at various compositions have been reported at an activation temperature of 500 degree C. The catalytic activity for the esterification of acetic acid with n-butanol has heen correlated with electron donating properties and surface acidity/basicity of the oxides.

Acidity/basicity, electron donor properties and catalytic activity of sulphate modified stannic oxide

The surface electron donor properties of sulphate modified stannic oxide have been determined from the adsorption of electron acceptors of various electron affinities on the oxide surface. The acid base properties of stannic oxide have been determined by titration method using Hammett indicators. Catalytic activities of the oxide for esterification of acetic acid using n-butanol.reduction of cyclohexanone in 2-propanol and oxidation of cyclohexanol with benzophenone have been studied. The data have been correlated with the surface electron donor properties of these oxides. The activity for reduction and oxidation decreases and that for esterification reaction increases on modification with sulphate ion. It has heen found that electron donating capacity decreased when stannic oxide was modified with sulphate ion.

Acidity / basicity and electron donor properties and catalytic activity of sulphated titania

The surface acidity/ basicity of TiO2 (rutile) and its sulphate modified form have been determined by titration method using Hammett indicators after activation at different temperatures. The electron donating properties of these oxides are also studied from the adsorption of electron acceptors of different electron affinity values. The data have been correlated with the catalytic activity of these oxides towards esterification of acetic acid using n-butanol, reduction of cyclohexanone in isopropanol and oxidation of cyclohexanol in benzophenone. Catalytic activity for esterification and oxidation reaction parallels the acidity while that for reduction reaction parallels the basicity of these oxides.

Acidity/basicity, electron donor properties and catalytic activity of sulphate modified ceria

The changes in surface acidity/basicity and catalytic activity of cerium oxide due to surface modification by sulphate ion have been investigated. Electron donor properties of both the modified and unmodified oxides have been studied using electron acceptors of various electron affinity values, viz. 7,7,8,8-tetracyanoquinodimethane, 2,3,5,6-tetrachloro--l, 4-benzoquinone. p-dinitrobenzene and m-dinitrobenzene in order to find out whether the increase in acidity on suphation is due to the generation of new acidic sites or they are formed at the expense of some of the basic sites. The surface acidity/basicity has been determined using a set of Hammett indicators. The data have been correlated with the catalytic activity of the oxides for esterification of acetic acid using l-butanol, reduction of cyclohexanone with 2- propanol and oxidation of cyclohexanol using benzophenone.

Lewis acidity of rare earth exchanged zeolites

The Lewis acidity of yttrium and dysprosium exchanged zeolite Y and ZSM-5 has been determined by titration method using Hammett indicators. The acidity of the Y form increases with increase in concentration of the rare earth cation in the Y zeolite. It is independent of the amount of the rare earth ion for ZSM-5. The data have been correlated with the activity of these zeolites for the esterification of butanol using acetic acid.

Biobutanol from lignocellulosic biomass by a novel Clostridium sporogenes BE01

In the current study, a novel non-acetone forming butanol and ethanol producer Was isolated and identified. Based on the 16s rDNA sequence BLAST and phylogenetic analyses, it was found to have high similarity with the reported hydrogen producing strains of Clostridium sporogenes. Biochemical studies revealed that it is lipase and protease positive. The lipolytic and proteolytic properties are the very important characteristics of Clostridium sporogenes. Sugar utilization profile studies were positive for glucose, saccharose, cellobiose and weakly positive result to xylose. This study demonstrated C. sporogenes BE01, an isolate from NIIST is having potential to compete with existing, well known butanol producers with the advantage of no acetone in the final solvent mixture. Rice straw hydrolysate is a potent source of substrate for butanol production by C. sporogenes BE01. Additional supplementation of vitamins and minerals were avoided by using rice straw hydrolysate as substrate. Its less growth, due to the inhibitors present in the hydrolysate and also inhibition by products resulted in less efficient conversion of sugars to butanol. Calcium carbonate played an important role in improving the butanol production, by providing the buffering action during fermentation and stimulating the electron transport mediators and redox reactions favoring butanol production. Its capability to produce acetic acid, butyric acid and hydrogen in significant quantities during butanol production adds value to the conversion process of lignocellulosic biomass to butanol. High cell density fermentation by immobilizing the cells on to ceramic particles improved the solvents and VFA production. Reduced sugar utilization from the concentrated hydrolysate could be due to accumulation of inhibitors in the hydrolysate during concentration. Two-stage fermentation was very efficient with immobilized cells and high conversions of sugars to solvents and VFAs were achieved. The information obtained from the study would be useful to develop a feasible technology for conversion of lignocellulosic biomass to biobutanol.

Preliminary Characterisation of Low-Temperature Bonded Copper Interconnects for 3-D Integrated Circuits

Three dimensional (3-D) integrated circuits can be fabricated by bonding previously processed device layers using metal-metal bonds that also serve as layer-to-layer interconnects. Bonded copper interconnects test structures were created by thermocompression bonding and the bond toughness was measured using the four-point test. The effects of bonding temperature, physical bonding and failure mechanisms were investigated. The surface effects on copper surface due to pre-bond clean (with glacial acetic acid) were also looked into. A maximum average bond toughness of approximately 35 J/m² was obtained bonding temperature 300 C.

Caracterización citogenética de lucilia sericata (Meigen, 1826) (Diptera: calliphoridae), Cepa Bogotá, Colombia

Introducción: Lucilia sericata es una especie de importancia médica y forense, utilizada en terapialarval para curar heridas crónicas y en estudios médico-legales empleada en la estimacióndel intervalo post mórtem y el traslado de cadáveres. No existen registros de las característicascitogenéticas de esta mosca en el neotrópico. El objetivo principal de este trabajo fue identificarlas características morfométricas cromosómicas y las estructuras primarias del cariotipo, a partirde especímenes de L. sericata de la cepa Bogotá, Colombia. Materiales y métodos: Se tomaronhuevos embrionados, que fueron previamente esterilizados en su superficie, se maceraron y luegofueron sembrados en el medio de cultivo L-15, suplementado con 20% de sfb, e incubados auna temperatura de 28 ºC, sin atmosfera de C02. La preparación de los cromosomas se obtuvo demonocapas celulares semiconfluentes, empleando diversas soluciones: antimitótica (Colchicina),hipotónica (KCl 0,075 M) y fijadora (Carnoy: metanol y ácido acético; 3:1). Se llevó a cabo la técnicade bandeo C para la identificación de regiones cromosómicas de heterocromatina constitutiva.Resultados: Se obtuvieron parámetros morfométricos de cada par cromosómico. El número diploidedel cariotipo obtenido de los cultivos celulares fue 2n = 12; éstos se clasificaron morfológicamente,de acuerdo con patrones previamente establecidos, así: los pares I, II, IV y V fueronmetacéntricos, y el par III fue submetacéntrico. A su vez, el par sexual fue heteromórfico, siendoel cromosoma X metacéntrico y el cromosoma Y submetacéntrico. El bandeo C fue positivo paratodos los pares cromosómicos. Conclusiones: Se establecieron las características citogenéticas deL. sericata, cepa Bogotá, Colombia, relacionadas con número, forma, tamaño, posición del centrómeroy regiones heterocromáticas de los cromosomas.

Caracterización de las reacciones adversas a medicamentos como causa de ingreso a una unidad de cuidado intermedio en un hospital de tercer nivel de atención

Objetivo: Determinar la ocurrencia de reacciones adversas a medicamentos (RAM) como causa de ingreso a una unidad de cuidado intermedio de un hospital universitario. Materiales y Métodos: Se revisaron las historias clínicas de los pacientes admitidos a la Sala de Emergencias – Cuidado Intermedio (SALEM) entre septiembre y diciembre de 2012 que cumplieron los criterios de inclusión y se detectaron los casos sospechosos de reacción adversa a medicamento (RAM) que posteriormente fueron evaluados por cuatro investigadores respecto a la causalidad a través del Algoritmo de Naranjo, prevenibilidad usando los criterios de Shumock y Thornton y la clasificación clínica mediante el empleo del sistema DoTS. Resultados: Se encontraron 96 pacientes que presentaron 108 casos de RAM. Las RAM más frecuentes fueron las arritmias y la hemorragia de vías digestivas altas (12.04%), 20.3% de los casos correspondieron a fallos terapéuticos, y, los medicamentos mayormente asociados fueron el ácido acetil salicílico (15.74%) y el losartán (10.19%). 46 casos fueron catalogados como posibles y uno solo como definitivo. Usando la clasificación DoTS se estableció que en el 82.4% de los casos la dosis era colateral (dentro del rango de dosis terapéutica), 89.8% fueron independientes del tiempo, y entre los factores mayormente asociados a susceptibilidad a la RAM estuvieron las comorbilidades (41.7%) y la edad (49%). 44% de las RAM fueron prevenibles. Conclusión: Las RAM son una causa de ingreso no despreciable en una unidad de cuidado intermedio para las cuales existen diferentes sistemas de evaluación, y una cantidad significativa de ellas es prevenible. Se requieren más estudios a nivel nacional para evaluar la incidencia de estas y establecer estándares de clasificación y medidas para mitigar su efecto.