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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Synthèse et évaluation biologique d’hétérocycles à cinq chaînons, inhibiteurs de la protéine farnésyltransférase / Synthesis and biological evaluation of five-membered heterocycles, inhibitors of protein farnesyltransferase

Bosc, Damien 14 October 2011 (has links)
La protéine farnésyltransférase (FTase) est une métalloenzyme à zinc catalysant le transfert d’une chaîne farnésyle provenant du pyrophosphate de farnésyle (FPP) sur le résidu cystéine de certaines protéines possédant un motif CaaX C-terminal où C est la cystéine farnésylée, a est un acide aminé aliphatique et X est Ser, Ala, Gln ou Met. Une fois additionné, le groupement farnésyle fait office de point d’ancrage rendant possible la fixation des protéines à la membrane cellulaire et de guide moléculaire facilitant la liaison de ces protéines prénylées à d’autres protéines. D’abord étudiée en oncologie, la FTase constitue aujourd’hui une cible potentielle pour la thérapie antiparasitaire qui manque cruellement de médicaments suite à l’apparition de phénomènes de résistance. La nécessité d’améliorer les thérapies existantes ouvre la voie de recherches innovantes pour trouver de nouvelles molécules bioactives.Lors de ces travaux de thèse, les deux stratégies de recherche pratiquées en chimie médicinale ont été utilisées.La première approche a consisté à synthétiser des analogues bisubstrats 1,2,3-triazoles pouvant se lier à la fois sur le site de liaison de la protéine et sur celui du FPP. Cette approche rationnelle a aussi permis d’ébaucher une synthèse monotope de triazoles 1,5-disubstitués à partir d’amines primaires. L’approche par criblage constitue la deuxième méthode de recherche de nouveaux inhibiteurs. Dans ce contexte, la chimiothèque de l’ICSN a été criblée et deux composés de type 3-arylthiophène ont révélé de bonnes activités et une structure originale dans l’inhibition de la FTase. Ainsi, des travaux de relations structure-activité ont été réalisés pour moduler les différentes positions du thiophène et la nature de l’hétérocycle central.Ce travail nous a permis d’élaborer une librairie de plus d’une centaine de composés. L’évaluation biologique de ces analogues sur FTases isolées humaine et de T. brucei et sur parasites T. brucei et P. falciparum a révélé des molécules particulièrement intéressantes et prometteuses. / Protein farnesyltransferase (FTase) is a zinc metalloenzyme which catalyzes the transfer of a farnesyl chain from farnesyl pyrophosphate (FPP) to the cysteine residue of some proteins possessing a C-terminal CaaX moiety where C is the farnesylated cysteine, a is an aliphatic amino-acid and X is Ser, Ala, Gln or Met. Once attached, the farnesyl group serves as anchors for fixing proteins to cell membrane and as molecular handles for facilitating binding of these prenylated proteins to other proteins.First studied in oncology, FTase constitutes nowadays a potential target for antiparasitic therapies, where drugs are missing due to the appearance of resistance phenomena. The necessity to improve the existing therapies paves the way of innovating researches to find new bioactive molecules.During this Ph.D work, two strategies of research used in medicinal chemistry were performed.The first approach consisted in the synthesis of bisubstrate analogues with a 1,2,3-triazole core deviced to tie up both to the protein and the FPP binding sites. This rational approach also allowed to draft a one-pot synthesis of 1,5-disubstituted triazoles from primary amines.The screening approach was the second strategy to search for new inhibitors. For this purpose, ICSN chemical library was screened and two 3-arylthiophene compounds disclosed good activities and an original scaffold for FTase inhibition. Therefore, a structure-activity relationship study was carried out to modulate the different positions of the thiophene and the nature of the central heterocycle.This work allowed us to create a above-hundred-molecule library. The biological evaluation of these analogues on human and T. brucei isolated FTase and on T. brucei and P. falciparum parasites revealed particularly interesting and promising molecules.
52

Two-dimensional (2D) Monolayer Materials: Exfoliation, Characterization, and Application

Qu, Jiang 17 January 2023 (has links)
Monolayer two-dimensional (2D) materials have been regarded as a hot topic in the fields of condensed matter physics, materials science, and chemistry due to their unique physical, chemical, and electronic properties. However, the research on the preparation method and properties understanding of the 2D monolayer are inadequate. In this dissertation, taking 2D nickel-iron layered double hydroxides (NiFe LDHs) and molybdenum disulfide (MoS2) as examples, the practicability of the direct synthesis of NiFe LDHs monolayer and the thermal enhancement catalytic performance of 2D MoS2 monolayer (MoS2 ML) are discussed. First, a one-pot synthetic strategy (bottom-up method) is presented to synthesize 2D NiFe-based LDHs monolayers, including NiFe, Co-, Ru-, doped, and Au-modified NiFe LDHs. The prerequisite and universality of this strategy are investigated and confirmed. The features of LDHs are characterized by advanced technologies. The obtained LDH bulks own a large interlayer spacing up to 8.2 Å, which can be facilely exfoliated into monolayers in water by hand-shaking within 10 s. As a result, the as-prepared NiFe-based LDH monolayers display a good electrocatalytic oxygen evolution reaction (OER) performance. This facile strategy paves the way for designing easily exfoliated LDHs for highly active catalysts and energy conversion devices based on other monolayer LDHs. Second, with gold-modified tape, 2D MoS2 ML is exfoliated from the bulk crystal through a micromechanical exfoliation method (top-down strategy). The thermal effects of MoS2 ML are confirmed by Raman and photoluminescence (PL) spectra. Moreover, an on-chip MoS2 ML hydrogen evolution reaction (HER) reactor is designed and fabricated. The thermal effects generate efficient electron transfer in the MoS2 ML and at the electrolyte-catalyst (MoS2 ML) interface, leading to an enhanced HER performance. Compared to the results obtained at room temperature, the MoS2 ML shows a direct thermal enhanced HER performance at higher temperatures. In summary, the findings and understandings, the direct synthesis and direct thermal enhancement catalytic performance, of 2D monolayers offer a guideline for synthesizing and catalyst application of other 2D monolayers.
53

Revêtement en LiAlO2 sur des particules d’un matériau d’électrode positive LiNi0,6Mn0,2Co0,2O2 pour batterie aux ions lithium

Touag, Ouardia 05 1900 (has links)
Des progrès dans les batteries aux ions lithium sont en cours de développement afin de répondre, entre autres, à la demande croissante des hautes densités d'énergie et de puissance pour le réseau électrique et en particulier pour l'application dans les véhicules électriques. Ces derniers remplacent écologiquement les véhicules à moteur à combustion interne et leurs succès est principalement dû à leur efficacité énergétique supérieure, à leurs faibles coûts d'exploitation et à leur profil respectueux de l'environnement par rapport aux véhicules à essence. Parmi les différents matériaux de cathode, les composés d'intercalation LiNixMnyCo1-x-yO2 (NMC) sont les meilleurs candidats pour des applications dans les batteries aux ions lithium à hautes performances. Des efforts sont en cours pour mettre en oeuvre des matériaux cathodiques à base de NMC riches en nickel pour répondre aux besoins environnementaux et énergétiques. Aussi séduisants soient-ils, ces matériaux de cathode présentent certains inconvénients liés à une forte réactivité, notamment à l'interface avec l'électrolyte. Pour contourner ces problèmes, des modifications de surface sont étudiées comme des solutions accessibles pour protéger le matériau actif et améliorer ses performances. Bien que diverses chimies et stratégies de revêtement soient publiées dans la littérature, notre approche consistant à combiner la synthèse et la modification de surface du matériau actif en une étape est aussi simple qu'efficace. Le présent manuscrit porte sur l’étude de ce composé. Deux méthodes de revêtement de surface ont été étudiées et leur matériau revêtu résultant a été comparé au matériau non revêtu. Après une caractérisation détaillée de ces matériaux, des études électrochimiques ont été menées afin d’évaluer leurs performances. Enfin, notre NMC622 revêtu de LiAlO2 en une seule étape s'est avéré efficace pour contrer la dégradation de la capacité du NMC et pour améliorer la stabilité structurelle des particules, améliorant ainsi leur cycle de vie. / Advances in lithium-ion batteries are being developed in order to meet, among other things, the increasing demand for high energy and power densities for the electric power grid and especially for application in electric vehicles. The latter are a green replacement for internal combustion engine vehicles, and their success is mostly due to their higher energy efficiency, low operating costs and eco-friendliness compared to gasoline-powered vehicles. Among various cathode materials, LiNixMnyCo1-x-yO2 (NMC) intercalation compounds are the best candidates for applications in high performance lithium-ion batteries. Efforts are underway to implement nickel-rich NMC-based cathode materials to meet environmental and energy needs. As appealing as they are, these cathode materials present certain drawbacks associated with high reactivity, especially at the interface with the electrolyte. To circumvent these issues, surface modifications are investigated as accessible solutions to protect the active material and enhance its performance. Although various coating chemistries and strategies are published in the literature, our approach of combining synthesis and surface modification of the active material in a single pot is as simple as it is efficient. The following manuscript will be covering the study of this material. Two methods of surface coating were studied, and their resulting coated material was compared to the uncoated material. After a detailed characterization of these materials, electrochemical studies were carried out to evaluate their performance. Finally, our resulting one pot LiAlO2- coated NMC622 has shown to be effective in counteracting NMC capacity degradation and improving the structural stability of the particles, thereby improving their cycle- life.
54

Metal catalysed alkylation of carbonyl compounds with formaldehyde

Lorusso, Patrizia January 2015 (has links)
Formaldehyde is a chemical used widely in the manufacture of building materials. A remarkable example is represented by the Lucite two-step Alpha technology for the large scale production of methyl methacrylate (MMA), the essential building block of all acrylic-based products. Esters and ketones are important intermediates in the manufacture of acrylate esters therefore α-hydroxymethylenation of carbonyl compounds using formaldehyde as a one carbon alkylating agent and subsequent dehydration to the corresponding methylenated derivatives has been explored in the current work. We report a novel catalytic approach for the synthesis of methyl methacrylate (MMA) via one-pot α-methylenation of methyl propanoate (a chemical intermediate of the ALPHA process) with formaldehyde, generated in situ by Ru-catalysed dehydrogenation of methanol. Elucidation of the mechanism involved in the catalytic dehydrogenation of methanol along with the collateral alcohol decarbonylation reaction was gained through a combined experimental and DFT study. The development of an alternative process where anhydrous formaldehyde is produced in situ would provide a simplification over the current second step of the ALPHA technology where the formaldehyde is initially produced as formalin, subsequently dehydrated to afford anhydrous formaldehyde in order to ensure high selectivity to MMA. As an alternative approach, ketones, in particular 3-pentanone and 2-butanone, were targeted as potential substrates in order to overcome some of the problems related to competing reactions that occur at the ester group. Hydroxymethylenation, followed by dehydration and Baeyer-Villager oxidation, possibly catalysed by enzymes to reverse the normal selectivity, leads to the formation of acrylate esters. The catalytic reaction is enabled by a gold carbene hydroxide complex in such a way that the substrate undergoes C-H activation and the nascent metal alkyl acts as a nucleophile towards the electrophilic formaldehyde, supplied in the form of alcoform* (solution of paraformaldehyde in methanol).

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