No description available.

The intramolecular styryl Diels – Alder (ISDA) reaction is a rare and unique [4+2] cycloaddition with potential in the syntheses of polycycles. Its utility is based on the formation of two rings and one stereocenter in a single step, making it an efficient method for the construction of lignan-type natural product targets. Detailed mechanistic studies with complex esters and the application to natural product synthesis has been limited due to drawbacks including the loss of aromaticity, producing slow reactivity, a potentially problematic thermal [1,3]-hydrogen shift, and electronic mismatch related to the substituents on the aryl functional groups. In this research, we found conditions that led to the successful application of the ISDA reaction on the total synthesis of the anticancer deoxypodophyllotoxin and the antiviral agent F4-4. Deoxypodophyllotoxin was synthesized in seven steps, which is a very concise synthesis for a complex lignan. Density functional theory was used to analyze the two components of the ISDA reaction, the [4+2] cycloaddition and the [1,3]-hydrogen shift. Several pathways were analyzed, and the rate determining step was determined to be the [4+2] cycloaddition. We also found that the [1,3]-hydrogen shift is assisted by di-tert-butylhydroxytoluene and is lower in energy than the [4+2] cycloaddition.The two targets chosen for this research have important biological activities. Deoxypodophyllotoxin is known as a potent anticancer agent related to podophyllotoxin. Podophyllotoxin is a more abundant lignan which is the precursor of the FDA approved drugs etoposide and teniposide, used for the treatment of lung and testicular cancer. Other biological activities of deoxypodophyllotoxin have been found including antibacterial, antiviral, and anti-inflamatory activity. Also, it was recently discovered that F4-4 possesses antiviral activities against Herpes simplex viruses 1 (HSV-1), 2(HSV-2), and H. zoster. Since both deoxypodophyllotoxin and F4-4 are not available in large quantities from natural sources, chemical synthesis is important for continuing research and drug development of these compounds.

No description available.

Further investigations intending illucidate the mechanism of a newly discovered redox-alkylation reaction of azo dyes are presented. Preliminary results indicate that this reaction most probably proceeds via initial N-alkylation of the anion derived from an alpha-ketohydrazone. An investigation is continued to study the synthesis of macrocycle-carbohydrate-dye hybrids. The development of a modular approach to macrocycle assembly has enabled the synthesis of a library of pyridine-based macrocycles possessing multiple donor sites. A central dye scaffold, prepared from the SNAr reaction between halo-substituted azo dye and a disubstituted phenol, was decorated with a representative carbohydrate or macrocycle using Sharpless click chemistry. Also an "S3N-ligand azo-dye" conjugate has been synthesised with a view to the development of a sensor for heavy metal ions. Complexation of this system with Ag(I), Hg(II) and Cu(II) salts has been investigated. Complexation of the dye to metals results in a bathochromic shift in the absorption maximum of the azo dye, an effect which is most pronounced for Cu(II).The Kobayashi fragmentation has transformed the area of benzyne chemistry as it enables its generation from readily available precursors under mild reaction conditions. The controlled generation of benzyne in this manner has been utilised by many groups, allowing readily access to a variety of functionalised aromatic and heteroaromatic from simple precursors. During the course of a synthetic project, which was to utilise the Kobayashi fragmentation in a key intramolecular Diels-Alder reaction, we noticed that alternate modes of fragmentation/rearrangement accompanied the desired elimination reaction leading to benzyne generation. In particular, competing Fries or Smiles rearrangements became the major routes of fragmentation in appropriately functionalised substrates. The results of an investigation into the factors affecting the course of the Kobayashi fragmentation, together with the development of a novel bi-aryl synthesis are presented in this thesis.

Orientador: Luiz Carlos Dias / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-12T11:13:03Z (GMT). No. of bitstreams: 1 Melgar_GliseidaZelayaran_D.pdf: 8992583 bytes, checksum: 4cacbcdc703a19bccdf5bea13368488a (MD5) Previous issue date: 2008 / Resumo: Em 1995 Miao e colaboradores relataram o isolamento da estavamicina (1), um novo produto natural, membro da família dos pirrolocetoindanos, a partir de uma cultura líquida de Streptomyses sp., isolada de uma amostra de terra coletada na Índia. A estavamicina contém uma interessante subestrutura hexahidroindeno de fusão de anel trans com 5 centros estereogênicos, uma cadeia lateral que contém outros 2 centros estereogênicos, um álcool dialílico, três duplas ligações e um resíduo de carboxilato de sódio. Apresenta atividade inibidora moderada contra a ligação do fator de transcrição EBV BZLF1 com o DNA com um valor de IC50 = 50 mM.O fragmento C11-C26 (206), contendo o grupo pirrol e 5 centros estereogênicos da estavamicina, foi preparado a partir do (R)-3-hidroxi-2-metilpropionato de metila, após uma sequência de reações, que envolveu 14 etapas (rota linear mais longa) e um rendimento global de 7%. As principais características incluem a preparação de uma imida a,b-insaturada utilizando a reação de Horner-Wadsworth-Emmons, a reação de olefinação de Takai, o acoplamento cruzado de Stille, seguido da cicloadição intramolecular de Diels-Alder que fornece dois adutos bicíclicos, sendo o majoritário correspondente ao produto desejado (para os casos de R = (R)-Bn e R = H). A última etapa foi a preparação da lactona tricíclica seguida da abertura utilizando o 2-lítio-N-MEM-pirrol.O fragmento C1-C6 (235) foi preparado a partir do 3-hidroxi-pentanodioato de dietila, após uma seqüência de reações, que envolveu 7 etapas e um rendimento global de 11,5%. As principais características incluem a elegante reação de transesterificação por quebra de simetria, redução do ácido com borana seguida por oxidação de swern e olefinação utilizando o procedimento modificado de Stork-Wittig.Em conseqüência, a rota de obtenção dos fragmentos C1-C6 e C11-C26 aqui descrita é, em princípio, prontamente aplicável para a preparação da estavamicina e análogos que eventualmente pudessem apresentar atividade farmacológica destacada. / Abstract: Epstein-Barr virus (EBV) is a human herpes virus that infects lymphocytes and epithelial cells. Is has been estimated that this virus infects a large part of the world¿s population. In 1995, stawamycin (1), a new natural product from the pyrroloketoindane family was isolated by Miao et. al from a liquid culture of Streptomyces sp, and displayed moderate inhibitory activity against the binding of the EBV BZLF1 transcription factor to DNA with IC50 = 50 mM in a DNA binding assay. Stawamycin has a trisubstituted trans-fused bicyclo[4.3.0]nonane substructure containing five stereogenic centres and a side chain that contains two stereogenic centres at C3 and C9 (absolute configuration not determined), a doubly allylic alcohol and a sodium carboxylate residue. To determine the relative configurations between C3 and C9, to establish the absolute configuration of stawamycin, and to provide material for further biological studies as well as access to novel analogues, we initiated a study towards the synthesis of this very interesting compound. We wish to describe here our successful efforts towards the preparation of the C1¿C6 as well as the C11¿C26 carbocyclic fragment of stawamycin. The bicyclo[4.3.0]nonane (C11¿C26) fragment of stawamycin has been prepared by a sequence involving 14 steps (7% overall yield) from methyl (R)-(-)-3-hydroxy-2- methylpropionate. Key steps are a Pd-catalysed Stille coupling reaction between a vinyl iodide and a vinyl stannane followed by an intramolecular Diels¿Alder cycloaddition reaction to give the desired adduct as the major isomer. The best result was obtained with the use of a triene bearing an achiral oxazolidinone in the presence of Et2AlCl to promote the IMDA cycloaddition reaction. The last step was an preparation of the tricyclic lactone followed by the opening by means of the 2-lítio-N-MEM-pirrol.The (C1¿C6) fragment of stawamycin has been prepared from diethyl-3- hydroxypentanedioate by a sequence which involved a symmetry breaking reaction of a cyclic anhydride, followed by the formation of a Z-vinyliodide employing a Stork-Wittig procedure. / Doutorado / Quimica Organica / Doutor em Ciências

Le diabète de type 2 est aujourd’hui une maladie de plus en plus répandu. En ce sens il est nécessaire de mettre au point de nouveau composé permettant d’inhiber la gluconéogenèse. C’est pourquoi nous nous sommes intéressé à la synthèse du FR225654 1, décaline présentant une activité hypoglycémiante in vivo après administration par voie orale et inhibiteur de la néoglucogenèse in vitro (IC50 = 1,1.10-7 M). Ce composé, isolé en 2005 du champignon Phoma sp N°00144 et jamais encore synthétisé à ce jour, possède un mécanisme d’action inconnu. La nécessité d’une synthèse par voie chimique convergente et flexible, permettant l’accès à des analogues, est donc évidente. La stratégie consistait à préparer une trans-décaline par le biais d’une réaction de Diels-Alder intramoléculaire à partir d’un triène précurseur. La combinaison de ces travaux a constitué une avancée importante dans le cadre de la synthèse du FR225654, un hypoglycémiant potentiel. La mise au point d’une synthèse convergente du précurseur de la réaction de Diels-Alder permettra notamment d’effectuer par la suite des modifications aisées en vue de la préparation d’une vaste gamme d’analogues simplifiés. A ce jour, le produit de cyclo-addition a été isolé et caractérisé, validant ainsi l’étape clé de la stratégie de synthèse. Ainsi, l’accès rapide au FR225654 est rendu possible et la synthèse d’analogues est maintenant envisageable. Les produits synthétisés feront l’objet d’une évaluation biologique, l’objectif ultime étant d’accéder à de nouveaux médicaments pour le traitement du diabète de type 2. / Type 2 diabetes mellitus (T2DM) is a growing worldwide health concern that is expected to afflict over 366 million people by 2030. FR225654 is a novel gluconeogenesis (GNG) inhibitor recently isolated from the culture broth of Phoma sp.. This compound selectively inhibits GNG of primary rat hepatocytes and shows highly hypoglycemic effects in several in vivo mouse models (80% decrease of glycemia). However, to date, the mechanism of action and molecular target remain unknown. From a structural point of view, FR225654 exhibits a highly oxygenated trans-decalin ring substituted by a β-keto-enol moiety and a side-chain bearing a conjugated carboxylic acid and a trisubstituted olefin. Project specific objectives were to design an efficient total synthesis which could also permit a straightforward access to diverse analogues. This feature would constitute a crucial step for the further understanding of Structure Activity Relationship of FR225654. The work consists in synthesizing separately a side chain and a trans-decalin core by means of an intramolecular Diels-Alder reaction from a precursor. To date, synthesis of the precursor has been achieved in 13 steps as well as the side chain. The Intramolecular Diels-Alder reaction has also been validated in order to accomplish the first total synthesis of FR225654.

This thesis describes synthetic studies directed towards the total synthesis of the nakafuran and florlide marine natural products. Chapter One provides an overview of the importance of natural products to current medicinal chemistry and describes how the "supply issue" associated with these biologically derived compounds can be resolved through the process of total synthesis. Two families of marine natural products, the nakafurans and the florlides, are introduced as synthetic targets and strategies utilising a type II intramolecular Diels-Alder (IMDA) reaction to achieve their total synthesis are delineated. The efficient preparation of regio- and stereodefined vinyl coupling fragments via hydrostannylation and hydrohalogenation methodology is described in Chapter Two. The palladium-catalysed cross-coupling of these fragments, via Stille or Negishi coupling methodology, yielded dienes which were successfully advanced to IMDA triene precursors. Chapter Three describes investigation of the type II IMDA reaction to give bicyclo[4.3.1]decene carbocyclic skeletons. A facile acid-catalysed 6,7-alkene to 7,8-alkene olefinic isomerisation, via a proposed oxonium intermediate, and the inability to appropriately functionalise the desired adducts impeded progress along the synthetic route. Molecular modelling was conducted to investigate the causes of this unexpected reactivity. Investigations in Chapter Four describe the successful synthesis and cyclisation of homomethyl triene analogues prepared via application of enyne metathesis chemistry. The use of an exo-cyclopropylcarbinyl fragmentation was found to be unsuccessful as a means of installing the desired 6-methyl-bicyclo[4.3.1]decan-2-one core with a competing endo-ring expansion giving rise to a bicyclo[4.4.1]undecane ring system. Chapter 5 summarises the above results and gives a brief discussion of the future potential of this research to provide for a total synthesis of the nakafuran and florlide natural products.

A novel hetero Diels-Alder reaction has been developed to facilitate the synthesis of annelated pyridines as models for pyridoacridine alkaloids. The key reaction is based on an intramolecular Diels-Alder reaction of an aza-1,3-butadiene with an appropriate dienophile, to yield the desired annelated pyridine. An extension of this methodology is to exploit the Eglinton copper (IT) dimerisation of terminal acetylenes. This allows for a unique double intramolecular hetero Diels-Alder reaction, where four new rings are formed in one step. This allows for a facile route to annelated bipyridines. Ultimately this methodology has led to an approach to the total synthesis of the natural product eilatin, a member of the class of compounds known as pyridoacridines.

This thesis describes synthetic studies directed towards the total synthesis of the nakafuran and florlide marine natural products. Chapter One provides an overview of the importance of natural products to current medicinal chemistry and describes how the "supply issue" associated with these biologically derived compounds can be resolved through the process of total synthesis. Two families of marine natural products, the nakafurans and the florlides, are introduced as synthetic targets and strategies utilising a type II intramolecular Diels-Alder (IMDA) reaction to achieve their total synthesis are delineated. The efficient preparation of regio- and stereodefined vinyl coupling fragments via hydrostannylation and hydrohalogenation methodology is described in Chapter Two. The palladium-catalysed cross-coupling of these fragments, via Stille or Negishi coupling methodology, yielded dienes which were successfully advanced to IMDA triene precursors. Chapter Three describes investigation of the type II IMDA reaction to give bicyclo[4.3.1]decene carbocyclic skeletons. A facile acid-catalysed 6,7-alkene to 7,8-alkene olefinic isomerisation, via a proposed oxonium intermediate, and the inability to appropriately functionalise the desired adducts impeded progress along the synthetic route. Molecular modelling was conducted to investigate the causes of this unexpected reactivity. Investigations in Chapter Four describe the successful synthesis and cyclisation of homomethyl triene analogues prepared via application of enyne metathesis chemistry. The use of an exo-cyclopropylcarbinyl fragmentation was found to be unsuccessful as a means of installing the desired 6-methyl-bicyclo[4.3.1]decan-2-one core with a competing endo-ring expansion giving rise to a bicyclo[4.4.1]undecane ring system. Chapter 5 summarises the above results and gives a brief discussion of the future potential of this research to provide for a total synthesis of the nakafuran and florlide natural products.

Les liquides ioniques à base de sels d’imidazolium sont une classe très importante de composés, compatibles avec de nombreuses réactions organiques et largement employés dans la synthèse organique en tant que solvants, catalyseurs ou ligands. En particulier, les liquides ioniques peuvent être récupérés à la fin de la réaction. Les sels d’imidazolium présentent également des propriétés d’organisation intéressantes, aussi bien en phase solide, liquide et en solution. Cependant, les liquides ioniques traditionnels présentent certains désavantages lorsqu’utilisés comme solvant dans des réactions intramoléculaires, surtout dans le cas où le réactif est apolaire. La faible solubilité de ce dernier dans le milieu ionique conduit à la formation des produits intermoléculaires. Les travaux présentés dans cette thèse portent sur l’utilisation des propriétés d’organisation des sels d’imidazolium, tout d’abord pour le développement des nouveaux cristaux liquides ioniques, comme le milieu réactionnel pour la réaction de Diels-Alder intramoléculaire, et ensuite pour la préparation des nanparticules d’or anisotropes. Dans un premier temps, le développement des sels d’imidazolium dicationiques portant des chaînes alkyles flexibles et un cœur rigide, avec des unités imidazolium attachées directement à un noyau naphthalène est rapporté. Par la suite, leurs propriétés thermiques et mésomorphes ont été étudiées. Ces sels sont stables thermiquement et forment une phase cristal liquide de type Smectique T, sur une plage de températures appropriées pour des réactions organiques. En utilisant le milieu cristal liquide comme milieu réactionnel dans la réaction de Diels-Alder, le réactif a été piégé dans la structure organisée de cette phase, ce qui a empêché l’interaction entre deux molecules de réactifs, limitant la formation du produit intermoléculaire. D’ailleurs, le milieu cristal liquide ionique a pu être récupéré et reutilisé à la fin de la réaction. Dans un deuxième temps, l’influence de la structure de la mésophase sur la réaction de Diels-Alder intramoléculaire a été étudiée. Des sels d’imidazolium tricationiques ayant une symétrie C3 ont ete développés dans le but d’obtenir des phases colonnaires. Ces sels possèdent un cœur rigide formé par trois cations imidazolium liés à un noyau benzène et des chaînes alkyles flexibles. Des études thermiques et mésomorphes sur ces composés ont été ensuite réalisées. Ces composés possèdent une haute stabilité thermique et forment une phase colonnaire rectangulaire, stable sur une large gamme de températures. L’influence de cette phase sur la réaction de Diels-Alder a ete étudiée. L’utilisation de la phase colonnaire favorise également la réaction intramoléculaire. En particulier, elle s’est avèree plus efficace que la phase Smectique T, probablement dû à sa structure plus organisée, indiquée par une enthalpie de tranisition cristal liquide – liquide isotrope plus élevée. Dans un dernier temps, nous nous sommes intéressés à l’utilisation des propriétés d’organisation des sels d’imidazolium dans la préparation des nanoparticules d’or anisotropes. Dans cette optique, différents mélanges binaires, composés d’un sel d’imidazolium et le diméthylformamide (DMF), ont été préparés et utilisés comme solvants et stabilisants, dans la synthèse des nanoparticules d’or à température ambiante. L’utilisation de ces milieux nous a permis d’obtenir des particules d’or avec différentes géométries. La forme des nanoparticules d’or obtenus dépend de la structure des sels d’imidazolium utilisés et de la concentration du mélange binaire, à la fois. / Ionic liquids based on imidazolium salts are an important class of compounds, possessing a very good compatibility with various organic reactions, and are widely used as solvents, catalysts and ligands in organic synthesis. Moreover, imidazolium salts possess interesting supramolecular organization in the solid, liquid and solution state. However, ionic liquids present some disadvantages when used as solvents for intramolecular reactions, especially in the case of apolar reactants. The low solubility of ionic compounds in ionic media promote the formation of intermolecular products. The main goal of the research presented in this thesis is to explore the supramolecular organization of imidazolium salts, first in the development of ionic liquid crystals as reaction media for intramolecular Diels-Alder reactions and secondly for the preparation of anisotropic gold nanoparticles. First, the development of dicationic imidazolium salts having a rigid core and flexible alkyl chains is reported. The rigid core is forned by direct attachment of two imidazoliums on a naphthalene moiety. Their thermal and mesomorphic analyses were then carried out. These dicationic salts show a high thermal stability and form a very ordered smectic T phase, over a wide range of temperatures. This mesophase was subsequently used as reaction medium for intramolecular Diels-Alder reactions. In this phase, reactants are trapped in the highly organized structure of the liquid crystal medium, limiting the formation of intermolecular products. Moreover, the ionic liquid crystal, was recoved at the end of reaction by simple extraction. Secondly, the influence of the mesophase’s structure on the Diels-Alder reaction was explored. Tricationic imidazolium satls having a C3 symmetry were developed in order to obtain columnar phases. The rigid core of these salts is composed of three imidazolium units directly attached to the benzene ring. Their thermal stabilities and mesomorphic properties were investigated. The columnar phase formed by these salts was then used as reaction media for Diels-Alder reactions, and it proved to be more efficient than the previously used smectic T phase, due to their more organized structure, as indicated by the higher enthalpy value of the liquid crystal - isotropic liquid transition. iv Finally, the supramolecular organization in solution of two imidazolium salts was explored with the aim to prepare anisotropic gold nanoparticles. Different binary mixtures composed of an imidazolium salt and dimethylformamide (DMF) were prepared and used both as solvent and capping agent in the synthesis of gold nanoparticles, at room temperature. The use of these binary mixture allowed us to synthesize nanoparticles with various geometries. The form of the gold nanoparticles prepared in these binary mixtures was influenced by both, the structre and the concentration of the imidazolium salt used.