Dissertations / Theses on the topic 'Spiroketals'
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Selvaraj, Peter Rajan. "Exploratory study of ionophoric spiroethers and spiroketals." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1158620953.
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Owen, David Rodney. "Zirconocene mediated co-cyclisation reactions." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313216.
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Selvaraj, Peter Rajan. "Exploratory study of ionophoric spiroethers and spioketals." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1158620953.
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Modolo, Isabelle. "Studies toward completion of the C1-C28 segment of spongistatin 1. Synthesis and photochemistry of 4bH-pyrido[2,1-a]isoindol-6-one." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1236277748.
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Salles, Junior Airton Gonçalves 1977. "Síntese total dos ácidos pterídicos A e B." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248482.
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Orientador: Luiz Carlos DiasTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: Este trabalho relata a síntese total dos ácidos pterídicos A e B. O plano sintético utiliza como etapa-chave a reação aldólica syn com adição anti-Felkin intermediada por enolato de lítio entre a etil cetona a,b-insaturada de geometria Z 5 e o aldeído 4 para obtenção do fragmento C5-C15. Até onde sabemos este é o primeiro exemplo da utilização de um enolato de uma etil cetona a,b-insaturada quiral com geometria Z em uma reação aldólica. Uma eficiente reação de espirocetalização seguida de transformações adicionais conduziu ao ácido pterídico A em 2,9% de rendimento global para 13 etapas e ao ácido pterídico B em 2,8% de rendimento global também para 13 etapas. Em relação às outras sínteses totais, esta rota sintética apresenta um rendimento global comparável, mas chama a atenção pela nova e interessante abordagem na obtenção do fragmento C5-C15 via reação aldólica intermediada por lítio
Abstract: This work describes the convergent stereoselective synthesis of pteridic acids A and B. Our strategy involved a lithium enolate-mediated aldol reaction between ethyl ketone 5 and aldehyde 4 as the key step to set up C5-C15 fragment favoring 1,2-syn anti-Felkin adduct. As far we know, this is the first example of an aldol reaction between a chiral enolate of a (Z) enone and a chiral aldehyde. Efficient spiroketalization followed by additional transformations provided pteridic acids A and B in 2.9% and 2.8% overall yields, respectively. This approach compares very well with previously published routes and attracts attention to the novel and interesting C9-C10 bond construction to obtain C5-C15 fragment
Doutorado
Quimica Organica
Doutor em Ciências
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Oliveira, Luciana Gonzaga de. "Sintese total das (+)-crocacinas C e D : sintese dos fragmentos 6,6-espirocetal das espirofunginas A e B." [s.n.], 2004. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248479.
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Orientador: Luiz Carlos DiasTese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Doutorado
Quimica Organica
Doutor em Quimica
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Borghese, Sophie. "Toward green processes organic synthesis by catalysis with metal-doped solids." Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-01017796.
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Nowadays, the modern chemical industry has to deal with increasing environmental concerns, including the disposal of waste and its economic impact, or the diminution of important worldwide resources such as transition metals. In this Ph.D. thesis, we aimed to bring improvement in this area by the development of green processes, based on the use of recyclable heterogeneous catalysts. By combining the catalytic properties of several metal cations with the properties of solid catalysts such as polyoxometalates or zeolites, we were able to set up new tools for organic synthesis. Silver-doped polyoxometalates proved to be very efficient catalysts in the rearrangement of alkynyloxiranes to furans. Acetals and spiroketals were synthetized by dihydroalkoxylation of alkynediols under catalysis with silver-zeolites. As a perspective, we highlighted the potential applications of such green procedures in the total synthesis of more complex molecules. The first results suggested that these environmental friendly processes should gain increasing interest in the future.
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Lipinski, Radoslaw Michal. "Synthesis of the ABC fragment of pectenotoxin-4." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:123bf4c1-844a-492a-abdb-f7555719d7ff.
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This thesis details the application of two synthetic methodologies, developed by the Donohoe group, to the synthesis of the ABC fragment of pectenotoxin-4, a macrolide marine natural product that consists of 19 stereogenic centres, three tetrahydrofuran rings, one spiroketal and one bicyclic ketal embedded within a 26-membered macrocycle. Pivotal to the developed synthetic route was the utilisation of an unprecedented cascade osmium catalysed oxidative cyclisation for the construction of two THF rings (the BC ring system). After successfully developing a model system for the synthesis of the AB anomeric 6,5 spiroketal, which involved the employment of a hydride shift initiated oxo carbenium ion formation followed by intramolecular spiroketalisation, the developed system was then applied to the fully elaborated synthesis of the ABC fragment. The synthesis of the ABC fragment of pectenotoxin-4 was completed in 20 linear steps, with an overall yield of 3.3%.
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Vuong, Khuong Quoc Chemistry Faculty of Science UNSW. "Metal complex catalysed C-X (X = S, O and N) bond formation." Awarded by:University of New South Wales. Chemistry, 2006. http://handle.unsw.edu.au/1959.4/23015.
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This thesis describes the catalysed addition of X-H bonds (X = S, O and N) to alkynes using a range of novel rhodium(I) and iridium(I) complexes containing hybrid bidentate phosphine-pyrazolyl, phosphine-imidazolyl and phosphine-N heterocyclic carbene (NHC) donor ligands. The synthesis of novel bidentate phosphine-pyrazolyl, phosphine-imidazolyl (P-N) and phosphine-NHC (PC) donor ligands and their cationic and neutral rhodium(I) and iridium(I) complexes [M(P N)(COD)]BPh4, [M(PC)(COD)]BPh4, [Ir(P-N)(CO)2]BPh4 and [M(P-N)(CO)Cl] were successfully performed. An unusual five coordinate iridium complex with phosphine-NHC ligands [Ir(PC)(COD)(CO)]BPh4 was also obtained. Seventeen single crystal X-ray structures of these new complexes were determined. A range of these novel rhodium and iridium complexes were effective as catalysts for the addition of thiophenol to a variety of alkynes. Iridium complexes were more effective than rhodium analogues. Cationic complexes were more effective than neutral complexes. Complexes with hybrid phosphine-nitrogen donor were more effective than complexes containing bidentate nitrogen donor ligands. An atom-economical, efficient method for the synthesis of cyclic acetals and bicyclic O,O-acetals was successfully developed based on the catalysed hydroalkoxylation. Readily prepared terminal and non-terminal alkyne diols were cyclised into bicyclic O,O-acetals in quantitative conversions in most cases. The efficiency of a range of rhodium and iridium complexes containing bidentate P-N and PC donor ligands as catalysts for the cyclisation of 4-pentyn-1-amine to 2-methyl-1-pyrroline varied significantly. The cationic iridium complexes with the bidentate phosphine-pyrazolyl ligands, [Ir(R2PyP)(COD)]BPh4 (2.39-2.42) were extremely efficient as catalysts for this transformation. Increasing the size of the substituent on or adjacent to the donor led to improvement in catalytic activity of the corresponding metal complexes. The mechanism of the catalysed hydroalkoxylation was proposed to proceed by the initial activation of the alkyne via ?? coordination to the metal centre. The ?? binding of both aliphatic and aromatic alkynes to [Ir(PyP)(CO)2]BPh4 (2.44) was observed by low temperature NMR and no reaction between 2.44 and alcohols was observed. In contrast, the facility in which thiol and amine oxidatively added to 2.44 led the proposal that in the hydrothiolation and hydroamination reaction, the catalytic cycle commences with the activation of the X-H bond (X = S, N) by an oxidative addition process.
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Baddeley, Kate. "Ortholactone spiroketal fragment coupling." Thesis, Queen's University Belfast, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.725334.
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A divergent synthesis of spiroketals has been developed via the coupling of ortholactone and allylsilane fragments. This work expands upon earlier efforts into an intramolecular silyl modified sakurai reaction reported by Marko et al. The route provides a simple approach towards the divergent synthesis of complex structures which could be used in the synthesis of natural products and pharmaceutical molecules. The scope of this reaction has been amplified by the development of a novel methodology towards the synthesis of ortholactones via an oxidative catalytic nucleopalladation system which has allowed for the synthesis of a vast range of synthetically useful and highly functionalised ortholactones from readily accessible dihydropyran building blocks. The utility of these highly functionalised ortholactones is also demonstrated in a stereoselective rearrangement to form a substantial number of gamma-lactone structures, which are a common motif in a wide variety of natural products.
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Wonnacott, Anne. "New methods for spiroketal synthesis." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38192.
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Borghèse, Sophie. "Toward green processes organic synthesis by catalysis with metal-doped solids." Thesis, Strasbourg, 2013. http://www.theses.fr/2013STRAF008/document.
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De nos jours, l’industrie chimique est de plus en plus confrontée à la question de son impact environnemental. Dans le même temps, elle doit faire face à la diminution des ressources de matières premières importantes tels que les métaux de transition, tout en respectant des contraintes économiques. Ces travaux de thèse avaient pour but de tenter de répondre à ces exigences, par le développement de méthodologies de synthèse basées sur l’utilisation de catalyseurs hétérogènes recyclables. En combinant les propriétés catalytiques de certains ions métalliques avec les propriétés de catalyseurs solides tels que les polyoxométallates ou les zéolithes, nous avons pu mettre au point de nouveaux outils pour la synthèse organique. Les polyoxométallates dopés à l’argent ont démontré leur efficacité dans le réarrangement d’alcynyloxiranes en furanes. La synthèse de spiroacétals et d’acétals par dihydroalkoxylation d’alcyne diols a été effectuée pour la première fois en catalyse à l’argent, via l’utilisation de zéolithes. En perspective, nous avons mis en évidence les applications potentielles de ces procédés verts dans la synthèse totale de molécules plus complexes. Les premiers résultats suggèrent que de telles synthèses plus respectueuses de l’environnement ont tout intérêt à être davantage utilisées à l’avenirNowadays, the modern chemical industry has to deal with increasing environmental concerns, including the disposal of waste and its economic impact, or the diminution of important worldwide resources such as transition metals. In this Ph.D. thesis, we aimed to bring improvement in this area by the development of green processes, based on the use of recyclable heterogeneous catalysts. By combining the catalytic properties of several metal cations with the properties of solid catalysts such as polyoxometalates or zeolites, we were able to set up new tools for organic synthesis. Silver-doped polyoxometalates proved to be very efficient catalysts in the rearrangement of alkynyloxiranes to furans. Acetals and spiroketals were synthetized by dihydroalkoxylation of alkynediols under catalysis with silver-zeolites. As a perspective, we highlighted the potential applications of such green procedures in the total synthesis of more complex molecules. The first results suggested that these environmental friendly processes should gain increasing interest in the future
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Meyer, Thorsten. "Total syntheses of novel spiroketal natural products." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392071.
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Badham, Neil Francis. "Synthetic studies towards the spiroketal portion of avermectins." Thesis, University of Reading, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357197.
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Brunck, Annette. "Die Hecogenin-Cephalostatin-Route ein Weg aus dem Spiroketal-Dilemma /." [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=957236034.
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Hazelwood, Andrew James. "A new approach of the AB spiroketal of altohyrtin A." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620304.
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Birkbeck, Anthony Alexander. "Novel conformationally restrained glycomimetics : spiroketal mimics of sialyl Lewis X." Thesis, University of Cambridge, 1996. https://www.repository.cam.ac.uk/handle/1810/272030.
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Tanner, Huw Rowland. "New strategies towards the ABCD bis-spiroketal domain of the spongistatins." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613780.
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Robinson, G. C. "An approach to the spiroketal unit of the milbemycins and related compounds." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370298.
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Hook, D. F. "Synthesis of the C(16)-C(28) CD spiroketal fragment of spongistatin 1." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604210.
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This thesis is divided into 7 chapters. Chapter 1 describes the isolation and structure determination of the spongistatins. The biological activity of these molecules is discussed along with the development of pharmacophores. The relevance of the anomeric effect is also outlined. Chapter 2 reviews the published syntheses of the CD spiroketal fragment, highlighting the important steps in each. Chapter 3 details the current strategy within our group towards a total synthesis of spongistatin 1. An existing synthesis of a CD spiroketal-containing fragment is presented along with the need for an improved synthesis, which shall form the basis of the following two chapters. Chapter 4 outlines a first generation approach to the CD spiroketal fragment based on the spiroketalisation of a b-keto-1,3-dithiane. Transformation to reveal functionalised CD spiroketal-based compounds are presented. Chapter 5 describes a second generation synthesis, drawing on the chemistry developed in Chapter 4. Successful elaboration to the desired C(16)-C(28) CD spiroketal fragment is discussed. Chapter 6 reveals a complementary approach to the AB spiroketal fragment along with a coupling to the CD spiroketal unit. Progress towards the C(29)-C(51) fragment is presented, along with the proposed final steps to assemble spongistatin 1. Details of a unified approach to assemble the Northern Fragment is also outlined. Chapter 7 provides a detailed account of the experimental procedures.
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Smith, Aaron C. Crimmins Michael T. "An improved synthesis of the AB spiroketal of spongistatin and synthetic studies toward yokonolide A." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2006. http://dc.lib.unc.edu/u?/etd,594.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2006.Title from electronic title page (viewed Oct. 10, 2007). "... in partial fulfillment of requirements for the degree of Doctor of Philosophy in the Department of Chemistry." Discipline: Chemistry; Department/School: Chemistry.
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Attouche, Angie. "Développement de nouvelles réactions radicalaires sans étain en glycochimie : élaboration de spirocétals et débenzylations régiosélectives." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00923135.
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Ces travaux de thèse ont consisté à développer de nouvelles réactions radicalaires dans le domaine de la glycochimie. Deux cascades radicalaires, n'utilisant aucun dérivé stannylé et impliquant un transfert d'hydrogène intramoléculaire, ont été étudiées. La première permet de synthétiser des motifs spirocétaliques [6.5] nonanomériques et la deuxième consiste à débenzyler régiosélectivement un éther de benzyle par proximité. Les spirocétals [6.5] nonanomériques sont des motifs présents dans de nombreuses structures de produits naturels. Pour obtenir ce squelette, dont la synthèse est généralement difficile, nous avons développé une cascade radicalaire en chaîne impliquant des précurseurs homopropargyliques et des dérivés phosphorés non toxiques. Plusieurs étapes se succèdent dont l'addition du radical phosphoré sur la triple liaison, un transfert 1,5 d'hydrogène permettant de générer un radical anomère de O-glycoside, à l'origine de la diastéréosélectivité du centre spiranique, et une cyclisation 5-exo-trig. Cette stratégie s'est révélée particulièrement efficace puisque de bons rendements et une excellente diastéréosélectivité ont été obtenus notamment en série glucose et glucosamine. La nouvelle réaction de O-débenzylation par proximité, développée dans la deuxième partie, permet de déprotéger sélectivement un éther de benzyle en α d'un groupement hydroxyle préalablement fonctionnalisé sous forme d'éther de silyle xanthate. Cette réaction se déroule en deux étapes successives dans le même ballon. La première est une cascade radicalaire constituée, entre autres, d'un transfert 1,7 d'hydrogène et de l'addition du radical benzylique, ainsi formé, sur le peroxyde de dilauroyle. L'acétal mixte intermédiaire obtenu est alors hydrolysé lors de la deuxième étape. Cette méthodologie a été appliquée avec succès à divers mono- et disaccharides polybenzylés et s'est révélée efficace en présence de nombreuses autres fonctionnalités chimiques (acétal de benzylidène, azido..).
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Fang, Chao. "Synthetic Studies Toward Marine Natural Product Okadaic Acid and Its Analogs." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306336570.
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Brand, Christian [Verfasser]. "Cyclopropyl-modifizierte Kohlenhydrate: Bausteine zum Aufbau von [n.5]-Spiroketalen und zur Einschränkung der konformationellen Flexibilität / Christian Brand." Norderstedt : Books on Demand, 2012. http://d-nb.info/1022785176/34.
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Labarre-Lainé, Jessica. "Approches synthétiques au fragment bis-spirocétal du 13-desméthyle spirolide C." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0268/document.
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Les spirolides sont des phycotoxines marines macrocycliques neurotoxiques qui s’accumulent lors d’efflorescences algales, posant ainsi des problèmes de santé publique.Absorbés puis concentrés par les organismes filtreurs, ils sont ensuite potentiellement transmis,via la chaîne alimentaire, aux animaux marins et à l’Homme. A ce jour, le mode d’action des spirolides n’est pas totalement élucidé et la toxicité vis-à-vis de l’Homme reste encore à étudier. Dans ce but et compte tenu de leur faible biodisponibilité, leur synthèse s’avère indispensable pour disposer de quantités suffisantes à leur étude pharmacologique. Ces travaux de thèse, menés en collaboration avec l’équipe du Dr. Guillou à l’ICSN, visaient la synthèse totale du 13-desméthyle spirolide C, membre le plus toxique de la famille des spirolides (DL50 = 5-8 μg.kg-1i.p.). La stratégie de synthèse envisagée implique une déconnexion de la molécule en deux fragments. Notre cible, le fragment bis-spirocétal, a été obtenue par cyclisation en milieu acide d’une dicétone-1,4 issue d’une réaction de sila-Stetter. Ce manuscrit rapporte, dans un premier temps, l’étude de la réaction clé de type sila-Stetter, et, dans un second temps, les différentes approches ayant mené à la synthèse du fragment bis-spirocétal C10-C24 du 13-desméthyle spirolide C. Pour former les centres stéréogènes présents sur la dicétone-1,4 intermédiaire, des voies de synthèse énantiosélectives puis diastéréosélectives, reposant sur l’emploi de copules chirales, ont initialement été explorées. Finalement, ces centres ont été générés en exploitant le pool chiral et l’alcool tertiaire présent sur le fragment a été formé par régénération de chiralitéSpirolides are marine macrocyclic neurotoxic phycotoxines which concentrateduring algal blooms, causing public health issues. First absorbed and concentrated by seafood,they are then potentially transmitted to marine wildlife and humans through the food chain. To date, the mode of action of spirolides is not fully elucidated and the toxicity toward humans stillneed studies. Considering their low bioavailability, their synthesis proves to be crucial to have enough material for pharmacological studies. These thesis works, performed in collaboration with Dr. Guillou’s team at ICSN, were aiming at the total synthesis of 13-desmethyl spirolide C, the most potent member of the spirolide family (IC50 = 5-8 μg.kg-1 i.p.). The envisioned synthetic strategy implies a disconnection of the molecule into two fragments. Our target, the bisspiroketal fragment, was obtained through acidic cyclisation of a 1,4-diketone formed via a sila-Stetter reaction. This manuscript first reports the methodology for the key sila-Stetter typereaction, and then the different approaches which have led to the synthesis of the C10-C24 bisspiroketalfragment of 13-desmethyl spirolide C. In order to form the stereogenic centers presents on the intermediate 1,4-diketone, enantioselective pathways and then diastereoselective pathways, relying on the use of chiral auxiliaries, were initially explored. Eventually these centers were generated from chiral pool and the tertiary alcohol present on the fragment was formed through self-regeneration of chirality
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Mandel, Jérémie. "Approches synthétiques de tétrahydroisoquinoléines par cyclisation Pallado-Catalysée & synthèse de composés spirocétaliques par RRM." Phd thesis, Université de Haute Alsace - Mulhouse, 2010. http://tel.archives-ouvertes.fr/tel-00717736.
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Après avoir exposé les enjeux de ce travail en présentant dans le chapitre 1 les produits naturels possédant le motif tétrahydroisoquinoléinique, leurs intérêts pharmacologiques et leur unique voie d'accès via la réaction de Pictet Spengler, nous avons présenté la synthèse énantiosélective de tétrahydroisoquinoléine 1,3-disubstituées et différentes tentatives d'obtention des motifs pentacycliques de différents alcaloïdes d'intérêt biologique. La synthèse énantiosélective de tétrahydroisoquinoléines 1,3-disubstituées a été effectuée en 6 étapes utilisant deux étapes clés. Une alkylation catalysée par transfert de phase permet de créer un centre asymétrique et une cyclisation pallado-catalysée permet d'accéder au motif tétrahydroisoquinoléinique. Dans la suite, les différentes voies d'accès testées permettant d'accéder au motif pentacyclique n'ont pas été couronnées de succès. Dans un second temps ont été exposées les différentes sources de composés possédant un motif spirocétalique, leurs propriétés électroniques et conformationnelles. Les différentes voies de synthèse de spirocétals ont été présentées. Les différentes voies de synthèse d'a-hétérofuranes ont été introduites en se concentrant sur les dérivés soufrés, azotés et oxygénés. L'utilisation des a alcoxyfuranes en réaction de cycloaddition a ensuite été présentée ainsi que l'utilisation des adduits. Enfin la réaction de RRM a été étudiée en se focalisant sur les réactifs à forte tension de cycle. Différentes voies de synthèse des a-alcoxyfuranes ont été exposées. Une voie d'accès générale a été développée par réaction d'addition/élimination sur le 2,5-diméthoxy-2,5-dihydro-2-furanoate de méthyle. La séquence cycloaddition [4+2] ou [4+3]1 RRM a été ensuite présentée permettant d'accéder aux spirocétals (5,6) et (6,6). L'application de cette méthodologie à la synthèse des aculéatines et des aculéatols, est étudiée.
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Stevens, Kiri. "Methodology for the synthesis of NP25302 and other bioactive natural products." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:ae18879e-d75e-4280-ba55-1ae08e64034f.
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Total synthesis of the pyrrolizidine alkaloid NP25302: (+)-NP25302 is an unusual vinylogous urea containing pyrrolizidine alkaloid shown to exhibit cell adhesion inhibition. It was envisaged that this natural product could be accessed by a novel 5-endo-dig cyclisation to construct the pyrrolizidine core, and a Curtius rearrangement to install the vinylogous urea motif. This methodology was first tested on a model system, furnishing nor-NP25302 from L-proline in 12 steps and 9% overall yield. The total synthesis of (±)-NP25302 was completed in 9 steps and 26% overall yield from ethyl 2-nitropropionate using similar methodology. Studies into the stereospecificity of the Au(I)-catalysed cyclisation of monoallylic diols: During the synthesis of (+)-isoaltholactone in the Robertson group, the key Au(I)-catalysed cyclisation was observed to occur with some stereospecificity. Further investigations were therefore conducted into the stereochemical outcome of this reaction using stereodefined allylic alcohols, and from the combined results a mnemonic was proposed to predict the stereochemistry of the products of this reaction. Studies into the total synthesis of ascospiroketals A and B: Investigations were conducted into the total synthesis of the recently isolated natural products ascospiroketals A and B. A second generation synthesis was used to construct advanced intermediates 1 and 2.
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Tomas, Loïc. "Synthèse totale du bistramide A, d'analogues et de spirocétals d'intérêt biologique." Thesis, Lyon 1, 2010. http://www.theses.fr/2010LYO10233.
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L'étude des molécules issues du milieu naturel a conduit les chercheurs à s'intéresser à la synthèse d'un motif structural commun à un grand nombre de molécules bioactives, les spirocétals. La mise au point au sein de notre laboratoire, d'une méthodologie de synthèse d'éthers d'énols exo-cycliques, précurseur de spirocétals, nous a conduits à nous intéresser au fragment spirocétal puis à la synthèse totale du bistramide A. Cette molécule naturelle, issue d'un animal marin présente d'importantes propriétés cytotoxiques la plaçant comme un agent anti-tumoral ou inflammatoire potentiel. Notre méthodologie de synthèse d'éthers d'énols consistant au couplage d'une lactone et d'une sulfone selon une réaction de type Julia, nous a permis d'obtenir l'éther d'énol cible qui par spirocyclisation intramoléculaire a conduit au motif spirocétal [6,6] du bistramide A. La molécule naturelle ainsi que deux analogues sont ensuite obtenus par fonctionnalisation des chaînes latérales du spirocétal, et couplage avec les fragments de type aminoacide et tétrahydropyrane fournis respectivement par le groupe du Pr. Yli-Kauhaluoma et celui du Pr. Piva. L'étude biologique des produits montre d'intéressantes propriétés de différenciation cellulaire, de déclenchement de l'apoptose et de blocage de la cytodiérèse. L'application de notre méthodologie, à la synthèse du SPIKET, ainsi qu'à l'obtention du spirocétal [5,6] de l'atténol A, permet d'étendre le domaine d'application de cette synthèse d'éthers d'énols exo-cycliquesSpiroketals are widely occurring substructures in natural products. The ever-increasing range of pharmacological activities displayed by products containing spiroketals has triggered an intense interest in their study, both from a synthetic and biological aspect. The development in our laboratory of an original enol ether synthesis motivated us to prepare the spiroketal fragment of bistramide A and, subsequently, to undertake its total synthesis. Bistramide A is a biologically active molecule isolated from the marine ascidian Lissoclinum bistratum that has emerged as a potential anti-inflammatory and anti-tumoral agent based on its high cytotoxicity and potent antiproliferative effect. The [6,6] spiroketal ring system of the natural product was accessed using a modification of the Julia olefination, extended to the reaction between a lactone and a heteroarylsulfone to prepare an exocyclic enol ether. The lactone and sulfone precursors were synthesized from a common starting material, dicyclohexylidene-D-mannitol. Bistramide A and two of its analogs were prepared by functionalization of the spiroketal side chains, followed by coupling reactions with the amino acid and tetrahydropyran subunits prepared by the groups of Pr. Yli-Kauhaluoma and Pr. Piva, respectively. An alternative approach to the precursor of the tetrahydropyran system from the chiral pool was developed. Biological studies revealed interesting effects on cellular differentiation, apoptosis, and cytokinesis. Application of our methodology to the synthesis of SPIKET and studies towards the [5,6] spiroketal of attenol A, gave us the opportunity to extend the scope of our exocyclic enol ether methodology
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Ollivier, Anthony Gabriel André. "Synthèse asymétrique de spiroacétals : vers la broussonétine H." Thesis, Clermont-Ferrand 2, 2011. http://www.theses.fr/2011CLF22109/document.
Full textAbstract:
Le motif spiroacétal est une structure présente dans le squelette de nombreuses molécules naturelles possédant des activités biologiques variées et pour laquelle il existe de nombreuses voies de synthèse. En revanche, son analogue azoté, le motif spiroaminal a été beaucoup moins étudié. Le premier de nos objectifs a consisté à développer une voie de synthèse énantiosélective, la plus générale possible, de ce motif. La stratégie retenue repose sur une étape clé de spirocyclisation acido-catalysée d’aminohydroxycétones issues de l’alkylation séquentielle de l’acétone N,N-diméthylhydrazone par divers synthons iodés. Si les spiroaminals attendus n’ont pas pu être obtenus, ces cétones polyfonctionnalisées ont permis d’accéder efficacement à des spiroacétals originaux : les 1,6-dioxaspiro [4.6] undécanes et les 1,7-dioxaspiro [5.6] dodécanes. Dans une deuxième partie de notre travail, nous nous sommes intéressés à la synthèse totale de la broussonétine H, spiroacétal naturel possédant une très forte activité inhibitrice vis-à-vis de β-glycosidases. Son élaboration a été envisagée par couplage entre deux fragments clé : le 2-éthynyl-1,7-dioxaspiro [5.5] undécane et un iminocyclitol porteur d’un époxyde. La synthèse de ces deux composés a été réalisée en peu d’étapes et avec d’excellents rendements. Leur couplage a permis l’obtention d’un précurseur directe de la broussonétine H. L’étape finale de déprotection reste à optimiser afin de permettre l’isolement du produit naturelSpiroketal pattern appears in the skeleton of many natural products exhibiting various biological activities, and several synthetic routes to it have been reporting. Contrarily, spiroaminal moiety, its nitrogen analogue, has been less studied. The first of our objectives consisted to develop the most general enantioselective synthetic pathway to this framework. The adopted strategy is based on a key step acid-catalysed spirocyclisation of aminohydroxyketones, resulting from the sequential alkylation of acetone N,N-dimethylhydrazone by various iodide derivatives. If targeted spiroaminals could not be obtained, these polyfunctionalized ketones permit an efficient access to original spiroketals skeletons like 1,6-dioxaspiro [4.6] undecanes and 1,7-dioxaspiro [5.6] dodecanes. In a second part, we focused on the total synthesis of broussonetine H, a natural spiroketal possessing powerful inhibitory activities against β-glycosidases. Its elaboration was envisaged through the coupling between two key fragments : the 2-ethynyl-1,7-dioxaspiro [5.5] undecane and an iminocyclitol substitued by an epoxide. The synthesis of these two compounds was realized in few steps with good overall yelds.Their coupling led to a protected form of broussonetine H. The final deprotection step remains to be optimized to allow the final isolation of the natural product
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Bourdon, Benjamin. "Formation d’éthers d’énol par réaction de type Julia- Kocienski et leur conversion en spirocétals : application à la synthèse de la Broussonetine H et à la synthèse d’analogues du Bistramide A." Thesis, Lyon 1, 2009. http://www.theses.fr/2009LYO10190/document.
Full textAbstract:
Les spirocétals sont des sous-unités présentes dans de nombreuses molécules naturelles d’intérêt biologique. Pour accéder à ces structures, la spirocyclisation d’éthers d’énol en milieu acide est une méthode de choix. L’application de la réaction de Julia-Kocienski à des lactones a permis d’obtenir exo-glycals et éthers d’énol exo-cycliques tri- et tétrasubstitués. Selon l’hétérocycle porté parla sulfone engagée, l’un ou l’autre des diastéréoisomères de l’éther d’énol peut être obtenu préférentiellement. La spirocyclisation des produits formés, si elle est réalisée dans des conditions thermodynamiques, mène au [6.6]-spirocétal le plus stable. Des conditions permettant d’obtenir le diastéréoisomère cinétique ont également été étudiées. Les spirocétals ainsi préparés ont été utilisés en synthèse totale. Par exemple, le fragment spirocétal de la Broussonetine H, ainsi que l’unité iminosucre, ont été obtenus efficacement de façon énantiopure. Enfin, les spirocétals diversement substitués ont permis de préparer plusieurs analogues du Bistramide A. Ce métabolite marin est un agent anticancéreux puissant qui se lie à l’actine pour bloquer la division cellulaire mais des interactions avec PKC-TM, notamment impliquant l’apoptose, sont à l’étudeSpiroketals are often found as structural subunits of many biologically active natural compounds. One of the more powerful methods to access this structure is the acid-catalyzed cyclization of enol ethers. The reaction of Julia-Kocienski reagents with lactones allows us to synthesize various tri- and tetrasubstituted exo-glycals and exo-cyclic enol ethers. It is possible to obtain preferentially either one or the other of the two diastereoisomeric enol ethers by varrying the heterocycle moiety of the sulfone. These enol éthers are cyclized under thermodynamic conditions leading to the more stable [6.6]-spiroketal but other conditions may allow us to obtain the kineticisomer. Thermodynamic spiroketals were used in total synthesis. For example, both fragments ofBroussonetine H (one iminosugar and one spiroketal) have been readily and effectively prepared.Finally, diversely substituted spiroketals have been synthesized to prepare analogues of Bistramide A.This marine metabolite is a powerful antitumor agent that binds to actin and thus blocks cell divisionalthough some interactions involving PKC-TM are actually under study
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kung, Yi-Zhou, and 龔義洲. "Synthesis of Optically Active [4.5] Spiroketals and Polysubstituted Furans Mediated by Ceric Ammonium Nitrate." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/51865818580367568872.
Full textAbstract:
碩士靜宜大學
應用化學系研究所
92
A series of the optically active [4.5] spiroketals 2.6a-h and 2.11a-h have been successfully synthesized, respectively via [3+2] cycloaddition of ��-methylene enol ether sugars 2.5 and 2.10 with various 1,3-dicarbonyls 2.1a-h mediated by ceric ammonium nitrate (CAN). Similarly, [3+2] cycloaddition of cyclic 1,3-dicarbonyls 2.1e-g with phenylacetylene 2.12 also afforded the corresponding polysubstituted furans 2.13e-g; however, for acyclic 1,3-dicarbonyls 2.1a-d and 2.1i, the corresponding 1,4-dioxo-2-enes 2.14a-d and 2.14i were obtained as the major products and the corresponding furans 2.13a-b as the minor products. In addition, the corresponding higher carbon sugars 2.15-2.17 and 2.18-2.20 were also obtained from 2.5 and 2.10, respectively via malonyl radical addition.
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Chu, Jr-Hang, and 朱志航. "Synthesis of Optically Active [4.4] spiroketals and study of Carbon-Nitrogen and Carbon-Iodine Bonds Formation Mediated by Ceric Ammonium Nitrate." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/71570776417009881215.
Full textAbstract:
碩士靜宜大學
應用化學系研究所
92
Methyl 5-deoxy-2,3-O-isopropylidene-β-D-erythro-pent-4-enofuranoside 4 has been readily prepared from D-ribose. Employing cerium ammonium nitrate (CAN) to induce a series of 1,3-dicarbonyl compounds, such as: 2,4- pentanedione, ethyl acetoacetate, 1,3-cyclohexanedione, 5,5-dimethyl-1,3- cyclohexanedione, 1-benzoylacetone, dibenzoylmethane, 1,3-dimethyl barbituric acid and 4-hydroxycoumarin etc..., to generate corresponding the electron-poor radicals, which were proceeding [3+2] cycloaddition with 4 to obtain a series of the corresponding optically active dioxabicyclo[4.4] spiro ketals 5 with high stereoselectivity. In addition, CAN can also induced sodium azide and sodium iodide to produce azido and iodo radicals, which were proceeding the azdiohydroxylation and iodoalkoxylation with 4 in different solvents (CH3CN and small molecule of alcohols). Lactones 19 and 20 were obtained from 4 and 17 respectively by using CAN-sodium nitrite through the oxidative cleavage process.
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Su, Dong. "Synthetic studies toward the total synthesis of azaspiracid-1." Thesis, 2012. http://hdl.handle.net/1957/30887.
Full textAbstract:
Azaspiracid-1, a novel marine toxin that contains 9 rings and 20 stereogenic centers, has drawn considerable attention from synthetic groups worldwide due to its structural complexity, which includes a unique trioxabisspiroketal fused to a tetrahydrofuran ring (ABCD rings), a piperidine-tetrahydrofuran spiroaminal system fused to a 2,9-dioxabicyclo[3.3.1]nonane system (FGHI rings), a connecting six-membered cyclic hemiketal bridge (E ring) and a ��,��-unsaturated terminal carboxylic acid side chain. Our efforts toward the total synthesis of azaspiracid-1 led to the completion of both C1-C26 northern and C27-C40 southern halves of azaspiracid-1.
Herein, our improved and scalable synthetic studies toward the total synthesis of azaspiracid-1 is described. In particular, an improved and scalable synthesis of sulfone 3.6 with a key one-pot ketalization and methylation of ketone 3.22 to methylated hemiketal 3.24 is illustrated. A total 19 mmol of sulfone 3.6 has been prepared by this approach. An improved and scalable synthesis of aldehyde 3.7 utilizing allyl bromide 3.31 to couple with Evans auxiliary 3.33 has been developed. A total of 10 mmol of aldehyde 3.7 has been prepared by this approach. An improved synthesis toward the ABC ring fragment 3.52 with a high yield Julia coupling step is shown.
Large scale improved syntheses of the linkage fragment 3.2, the aldehyde fragment 4.9 and the azide fragment 4.10 of the southern portion of (���)-azaspiracid-1 have been described.
With an abundant material prepared by this scalable improved approach, we are confident that completing the total synthesis of (���)-azaspiracid-1 will occur in the near future.Graduation date: 2013
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Davy, Jason Alan. "Synthesis of the spiroketal moiety of didemnaketal A." Thesis, 2014. http://hdl.handle.net/1828/5761.
Full textAbstract:
The ascidian isolation artifact didemnaketal A is a highly oxygenated polyisoprenoid capable of inhibiting HIV-1 protease through an unusual dissociative mechanism. However, recent synthetic efforts have cast doubt on stereochemical assignments in the originally published structure. In the interest of elucidating the true structure of didemnaketal A through total synthesis, we present a strategy for rapidly accessing the putative spiroketal fragment by exploiting its latent symmetry. In a single step, double Sharpless asymmetric dihydroxylation reactions (SAD) allowed us to simultaneously set all seven stereogenic centers and assemble this complex fragment from non-chiral material. The precursor was obtainable through a racemic synthesis in which the geometric isomers of a nine-membered cyclic enone converged in a ring-opening cross metathesis reaction (ROCM).Graduate
0490
jdavy@uvic.ca
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Brunck, Annette [Verfasser]. "Die Hecogenin-Cephalostatin-Route : ein Weg aus dem Spiroketal-Dilemma / von Annette Brunck, geb. Koch." 1999. http://d-nb.info/957236034/34.
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Jhang, Hong-Wei, and 張宏瑋. "Palladium-mediated copolymerization of cyclic olefins and carbon monoxide : competition between ketone and spiroketal microstructures." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/99684097340450485904.
Full textAbstract:
碩士國立中正大學
化學工程研究所
93
The purpose of this project is to study the copolymerization of carbon monoxide with cyclic olefines by using a cationic palladium catalyst catalyst composition which are prepared from palladium acetate, a suitable amount of 1, 10-phenanthroline, a Bronsted acid ( eg. p-toluenesulfonic acid) and suitable amount of methanol. The polymerization reactions were conducted at a high pressure of carbon monoxide under various reaction conditions. The resulting polymers can be isolated collected after completing the polymerization reaction and after precipitation and collected by filtration. Based on 13C-NMR、 1H-NMR、MALDI-TOF and GC-MS analyses, the microstructure of the resulting copolymer can be identified. Our results clearly reveal that the microstructures of the resulting copolymers are highly depending on the structure of the cyclic olefins. In the second part of this paper , we focus on the influence of polymer structure and physical properties by 1,4-Benzoquinone. Finally , a terpolymerization of ethylene , endo-dicyclopentadiene and carbon monoxide was studied to investingate the convection between cyclization and the 〝Thorpe-Ingold effect〞.
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Keller, Valerie Ann. "Symmetry and synthesis : applications in spiroketal formation and in synthetic efforts towards the C22-C36 subunit of Halichondrin B /." 2004. http://catalog.hathitrust.org/api/volumes/oclc/61696225.html.
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