Thesis (PhD (Paraclinical Sciences))--University of Pretoria, 2006. / Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 73-86). Also available on the World Wide Web.

Orientador: Fernando Antônio Santos Coelho / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-18T09:19:04Z (GMT). No. of bitstreams: 1 Freire_KristersonReinaldodeLuna_D.pdf: 11850497 bytes, checksum: e314153107dd07d9368b43666918d973 (MD5) Previous issue date: 2011 / Resumo: As glicosidases regulam uma grande variedade de processos biológicos, incluindo a catálise, degradação, e biossíntese de oligossacarídeos e glicoconjugados. Inibidores eficientes dessas enzimas podem ser aplicados para o tratamento de várias doenças ou disfunções metabólicas, tais como doenças do estoque lisossomal, diabetes, cancer, malária e infecções virais, incluindo influenza e HIV. Neste trabalho, descrevemos a primeira síntese total de pirrolizidinonas e pirrolizidinas poli-hidroxiladas, benzillideno- e benzil-pirrolizidinonas e pirrolizidinas a partir de adutos de Morita-Baylis-Hillman (MBH). A estratégia sintética inicia-se com a síntese do aldeído N-Boc-4-hidroxi-D-prolinal, em 3 etapas (82 %), a partir da 4-hidroxi-D-prolina comercial. De posse do aldeído, realizou-se a reação de MBH, produzindo praticamente um único diastereoisômero ( 95% e.e.), que sofreu uma etapa de remoção de um grupo funcional e ciclização, formando uma pirrolizidinona. Esta última foi utilizada em duas sequências distintas: a primeira, envolve uma etapa one pot de ozonólise e redução de carbonila com NaBH4, e outra etapa de redução da carbonila com alana (AlH3), para fornecer a pirrolizidina poli-hidroxilada, com um rendimento global de 24% em 4 etapas; a segunda, envolve a reação de arilação de Mizoroki- Heck, utilizando como catalisador o paladaciclo de Nájera, visando fornecer as benzilideno-pirrolizidinonas. Estas, por sua vez, foram reduzidas com hidrogênio sob paládio, para fornecer as benzil-pirrolizidinonas. Tanto as benzil- quanto as benzilideno-pirrolizidinonas foram reduzidas com AlH3 para fornecer as benzilideno e benzil-pirrolizidinas, em rendimentos globais que variaram de 4 % a 23 %, em 4 ou 5 etapas. Os estudos de cristalografia de raios X permitiram determinar a estereoquímica absoluta e relativa de três pirrolizidinonas. Estudos de 2D-NOESY foram realizados para a confirmação da estereoquímica relativa das pirrolizidinonas e pirrolizidinas / Abstract: Glycosidases regulate a wide variety of biological processes, including catalysis, degradation, and biosynthesis of oligosacharides and glycoconjugates. Efficient inhibitors of these enzymes may therefore be applied to the treatment of several diseases or metabolic dysfunctions, such as lysosomal storage diseases, diabetes, cancers, malaria and viral infections, including influenza and HIV. Here we describe the first approach towards the total synthesis of a polyhydroxylated pyrrolizidinones, pyrrolizidines, benzylidene- and benzyl-pyrrolizidinones and - pyrrolizidines from asymmetric Morita-Baylis-Hillman (MBH) adducts. The synthetic strategy starts with the synthesis of aldehyde N-Boc-4R-Hydroxy-D-prolinal in three steps (82 %), from commercial 4-Hydroxy-D-proline. The MBH reaction between N-Boc-4R-Hydroxy-D-prolinal and methyl acrylate furnished a single isomer ( 95% ee). The MBH adduct was deprotected and cyclized in acid medium to provide the pyrrolizidinone. From this molecule, we evaluated two paths: the first involves a one pot ozonolysis and reduction of the carbonyl group with NaBH4 and reduction of lactam group with alane (AlH3) to provide a poly-hydroxylated pyrrolizidine, in four steps and 24% overall yield; the second involves the Mizoroki-Heck arylation reaction, using the Najera fs palladacycle as catalyst, to provide the benzylidenepyrrolizidinones. These, in turn, were reduced with hydrogen under palladium, providing the benzyl-pyrrolizidinones. Both the benzyl- and benzylidenepyrrolizidinones were reduced with AlH3 to provide the benzylidene and benzylpyrrolizidines, from 4% to 23% overall yields, over 4 or 5 steps. X-ray crystallography studies allowed determining the absolute and relative stereochemistry of three pyrrolizidinones. 2D-NOESY studies were performed to confirm the stereochemistry of pyrrolizidinones and pyrrolizidines / Doutorado / Quimica Organica / Doutor em Ciências

No description available.

Les nitrones peuvent être réduites par le diiodure de samarium et réagir selon une additionconjuguée avec des acrylates-silylés, silylés ou ,disilylés. Ce couplage réducteur,développé avec des aldonitrones simples, a conduit à des dérivés silylés de g-Nhydroxyaminoacides.Ces derniers ont pu être réduits puis cyclisés en g-lactames substituéspar un groupement silylé, dont la position et la configuration dépendent de l’acrylate dedépart. L’oxydation de Tamao-Fleming a ensuite permis la conversion des composés silylésen leurs correspondants hydroxylés avec rétention de configuration. Cet enchaînementréactionnel a alors été appliquée à une nitrone cyclique polyalkoxylée dérivée du L-xylose, cequi a permis les synthèses de la 7-desoxy Uniflorine A et de la (+)-Australine, deuxpyrrolizidines polyhydroxylées inhibiteurs de glucosidases. / Nitrones are reduced by samarium diiodide and react through a conjugated addition with silylacrylates. This cross coupling, developed with simple aldonitrones, allowed the preparation ofsilyl g-N-hydroxyaminoacids derivatives. The latter were reduced and cyclised in g-lactams inwhich the position and the configuration of the silyl group depend of the starting acrylate.Tamao-Fleming oxidation was used for the conversion of silyl group to hydroxyl group withretention of configuration. Then, the reaction was applied to a cyclic polyalkoxy nitronederived from L-xylose and it allowed the synthesis of 7-deoxy Uniflorine A and (+)-Australine, polyhydroxylated pyrrolizidines exhibiting glucosidases inhibition.

La Nature est une source quasi inépuisable de molécules possédant des propriétés biologiques souvent remarquables. Ainsi, les plantes fournissent chaque jour de nouvelles structures dont les chimistes s’inspirent afin de créer de façon synthétique des molécules similaires ou dérivées pouvant avoir de potentielles applications en tant qu’agents thérapeutiques par exemple.L’émergence de la catalyse organométallique a permis d’améliorer considérablement les méthodes de synthèse de molécules complexes. La catalyse homogène à l’or, dont le potentiel n’a été exploité qu’à partir des années 2000, a prouvé son efficacité pour effectuer de nombreuses réactions permettant de créer plusieurs liaisons carbone-carbone ou carbone-hétéroatome en une étape. Les conditions douces et la grande tolérance des catalyseurs d’or vis-à-vis de groupements fonctionnels divers ont naturellement mené à l’application de la catalyse à l’or à la synthèse de produits naturels. Ces études s’inscrivent dans cette dynamique et exploitent la réactivité d’azacycles contraints et d’alcynes en présence d’or(I) pour former des squelettes hétérocycliques couramment rencontrés au sein de produits naturels. La réactivité particulière des groupements sulfonyles protecteurs de l’azote a également été étudiée pour synthétiser différentes molécules azabicycliques. Les méthodes de synthèse mises au point ont finalement été appliquées à la synthèse de molécules cibles. / Nature is a nearly endless source of molecules, often possessing remarkable biological properties. Thus, plants provide new structures every day, inspiring chemists to synthetically create similar molecules or analogs, which are potential therapeutic agents for example. The emergence of organometallic chemistry allowed for considerable improvement of synthetic methods to make complex molecular scaffolds. Homogeneous gold catalysis, whose potential has only been explored starting from 2000, proved its efficiency to make numerous reactions. Most of them can generate several carbon-carbon or carbon-heteroatom bonds in one step. Soft conditions as well as good tolerance of gold catalysts toward multiple functional groups naturally led to the application of gold-catalyzed steps in various total syntheses of natural products.The present study evolves in this context and explores the reactivity of strained azacycles and alkynes in the presence of gold(I) to form heterocyclic skeletons that are commonly found in natural products. The specific reactivity of sulfonyl nitrogen-protecting groups has also been studied to synthesize azabicyclic compounds. The application of those various new methodologies to the synthesis of target molecules has finally been studied.

La synthèse énantiosélective de deux pyrrolizidines naturelles, la (+)-rétronecine et la (+)-hyacinthacine A1, a été effectuée en se basant sur la réaction de cycloaddition [2+2] du dichlorocétène sur un éther d'énol chiral encombré. Ces synthèses sont caractérisées par une séquence très efficace conduisant à un lactame chiral (intermédiaire commun) qui conduit facilement au squelette pyrrolizidine.<br />La synthèse de la (+)-rétronecine est effectuée, notamment, par une oxydation allylique de la double liaison terminale de ce composé et une méthoxycarbonylation catalysée au palladium de manière à introduire un équivalent du groupe hydroxyméthyle. Pour la (+)-hyacinthacine A1, un groupement hydroxyméthyle masqué est introduit par addition d'un cuprate de phényldiméthylsilylméthyle sur un imminium intermédiaire provenant du même lactame. Ce groupement est alors converti en hydroxyméthyle, en fin de synthèse, par une oxydation de Tamao-Fleming.

No description available.

Li, Yanhong. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 192-212). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Li Mi. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 125-136). / Abstracts in English and Chinese. / Abstract --- p.i / 論文摘要 --- p.iv / Publications --- p.vi / Acknowledgement --- p.vii / Abbreviations --- p.viii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Pyrrolizidine alkaloids --- p.1 / Chapter 1.1.1 --- Distribution and plant sources --- p.1 / Chapter 1.1.2 --- Structures and nomenclature --- p.3 / Chapter 1.2 --- PA-containing Chinese medicinal herbs --- p.6 / Chapter 1.3 --- PA-induced toxicity。 --- p.7 / Chapter 1.3.1 --- Acute toxicity and chronic toxicity --- p.7 / Chapter 1.3.2 --- Genotoxicity --- p.8 / Chapter 1.3.3 --- Tumorigenicity --- p.8 / Chapter 1.3.4 --- Hepatotoxicity --- p.8 / Chapter 1.3.5 --- Mechanism of toxic effects --- p.9 / Chapter 1.3.5.1 --- Metabolic pathways --- p.10 / Chapter 1.3.5.2 --- Liver tissue-bound pyrroles --- p.16 / Chapter 1.3.5.3 --- Metabolizing enzymes --- p.17 / Chapter 1.3.5.3.1 --- Phase I metabolizing enzymes --- p.17 / Chapter 1.3.5.3.2 --- Phase II metabolizing enzymes --- p.18 / Chapter 1.3.5.4 --- Species and gender specificity toward toxicity --- p.19 / Chapter 1.3.5.5 --- Structure-activity relationships --- p.20 / Chapter 1.4 --- Prevention of PAs-induced toxicity --- p.23 / Chapter 1.4.1 --- Significance of prevention in humans --- p.23 / Chapter 1.4.2 --- Regulations toward preventing toxicity induced by PAs --- p.24 / Chapter 1.5 --- Aim of the present study --- p.25 / Chapter Chapter 2 --- Qualitative and Quantitative Analysis of PA-containing Chinese Medicinal Herbs --- p.26 / Chapter 2.1 --- Materials and equipments --- p.27 / Chapter 2.1.1 --- Herbal materials --- p.27 / Chapter 2.1.2 --- Chemicals and solvents --- p.27 / Chapter 2.1.3 --- Equipment and instrumentation --- p.27 / Chapter 2.2 --- Preparation of herbal extracts。 --- p.28 / Chapter 2.2.1 --- Crude herbal extract --- p.28 / Chapter 2.2.2 --- Total pyrrolizidine alkaloid extract --- p.28 / Chapter 2.3 --- Qualitative and quantitative analysis of Ligularia hodgsonii --- p.29 / Chapter 2.3.1 --- Methods --- p.29 / Chapter 2.3.1.1 --- HPLC-UV condition --- p.29 / Chapter 2.3.1.2 --- HPLC-MS condition --- p.29 / Chapter 2.3.1.3 --- Calibration curve for clivorine --- p.29 / Chapter 2.3.1.4 --- Recovery test --- p.30 / Chapter 2.3.1.5 --- Sample test --- p.30 / Chapter 2.3.2 --- Results and discussions --- p.30 / Chapter 2.3.2.1 --- Qualitative analysis of PAs in Ligularia hodgsonii --- p.30 / Chapter 2.3.2.2 --- Calibration curve for clivorine --- p.35 / Chapter 2.3.2.3 --- Result of the recovery test --- p.37 / Chapter 2.3.2.4 --- Quantification of PAs in Ligularia hodgsonii --- p.37 / Chapter 2.4 --- Qualitative and quantitative analysis of Tussilago farfara --- p.37 / Chapter 2.4.1 --- Methods --- p.38 / Chapter 2.4.1.1 --- HPLC-UV condition --- p.38 / Chapter 2.4.1.2 --- HPLC-MS condition --- p.39 / Chapter 2.4.1.3 --- Calibration curve for senkirkine --- p.39 / Chapter 2.4.1.4 --- Recovery test --- p.39 / Chapter 2.4.1.5 --- Sample test --- p.39 / Chapter 2.4.2 --- Results and discussions --- p.40 / Chapter 2.4.2.1 --- Qualitative analysis of senkirkine in Tussilago farfara --- p.40 / Chapter 2.4.2.2 --- Calibration curve for senkirkine --- p.42 / Chapter 2.4.2.3 --- Result of the recovery test --- p.42 / Chapter 2.4.2.4 --- Quantification of senkirkine in Tussilago farfara --- p.43 / Chapter 2.5 --- Qualitative and quantitative analysis of Gynura segetum --- p.43 / Chapter 2.5.1 --- Methods --- p.43 / Chapter 2.5.1.1 --- HPLC-UV condition --- p.43 / Chapter 2.5.1.2 --- HPLC-MS condition --- p.44 / Chapter 2.5.1.3 --- Calibration curves for senecionine and seneciphylline --- p.44 / Chapter 2.5.1.4 --- Recovery test… --- p.44 / Chapter 2.5.1.5 --- Sample test --- p.44 / Chapter 2.5.2 --- Results and discussions。 --- p.45 / Chapter 2.5.2.1 --- Qualitative analysis of PAs in Gynura segetum --- p.45 / Chapter 2.5.2.2 --- Calibration curves for senecionine and seneciphylline --- p.49 / Chapter 2.5.2.3 --- Result of the recovery test --- p.49 / Chapter 2.5.2.4 --- Quantification of PAs in Gynura segetum --- p.49 / Chapter 2.6 --- Qualitative and quantitative analysis of Crotalaria sessiliflora --- p.50 / Chapter 2.6.1 --- Methods --- p.50 / Chapter 2.6.1.1 --- HPLC-UV condition --- p.50 / Chapter 2.6.1.2 --- HPLC-MS condition --- p.50 / Chapter 2.6.1.3 --- Calibration curve --- p.51 / Chapter 2.6.1.4 --- Recovery test --- p.51 / Chapter 2.6.1.5 --- Sample test --- p.51 / Chapter 2.6.2 --- Results and discussions --- p.52 / Chapter 2.6.2.1 --- Qualitative analysis of monocrotaline in Crotalaria sessiliflora --- p.52 / Chapter 2.6.2.2 --- Calibration curve for monocrotaline --- p.54 / Chapter 2.6.2.3 --- Result of the recovery test --- p.54 / Chapter 2.6.2.4 --- Quantification of PAs in Crotalaria sessiliflora --- p.55 / Chapter 2.7 --- Qualitative and quantitative analysis of Senecio scandens --- p.55 / Chapter 2.7.1 --- Methods --- p.55 / Chapter 2.7.1.1 --- HPLC-UV condition --- p.55 / Chapter 2.7.1.2 --- HPLC-MS condition --- p.56 / Chapter 2.7.1.3 --- Sample test --- p.56 / Chapter 2.7.2 --- Results and discussions --- p.56 / Chapter 2.7.2.1 --- Qualitative analysis of PAs in Senecio scandens --- p.56 / Chapter 2.7.2.2 --- Quantification of PAs in Senecio scandens --- p.59 / Chapter Chapter 3 --- Hepatotoxicity Induced by PA-containing Chinese Medicinal Herbs --- p.60 / Chapter 3.1 --- Materials and methods --- p.62 / Chapter 3.1.1 --- Reagents --- p.62 / Chapter 3.1.2 --- Animal models --- p.62 / Chapter 3.1.3 --- Determination of the serum ALT activity --- p.64 / Chapter 3.1.4 --- Determination of hepatic GSH level --- p.68 / Chapter 3.1.5 --- Quantitation of liver tissue-bound pyrroles --- p.69 / Chapter 3.1.6 --- Histological assessment of liver morphological changes --- p.70 / Chapter 3.1.7 --- Assessment of hepatocytes apoptosis --- p.71 / Chapter 3.1.8 --- Statistical analysis --- p.72 / Chapter 3.2 --- Results and discussion --- p.72 / Chapter 3.2.1 --- Calibration curves --- p.72 / Chapter 3.2.1.1 --- Calibration curve for the determination of serum ALT activity --- p.72 / Chapter 3.2.1.2 --- Calibration curve of determination of hepatic GSH level --- p.73 / Chapter 3.2.2 --- Hepatotoxicity Study of Crotalaria sessiliflora --- p.74 / Chapter 3.2.2.1 --- Hepatotoxicity at 24 hrs after treatment --- p.74 / Chapter 3.2.2.1.1 --- Correlation between dosage of monocrotaline in Crotalaria sessiliflora and amount of liver tissue-bound pyrroles --- p.74 / Chapter 3.2.2.1.2 --- Effects of Crotalaria sessiliflora on the serum ALT activity --- p.79 / Chapter 3.2.2.1.3 --- The correlation between the elevated level of ALT activity and apoptosis of liver cells --- p.85 / Chapter 3.2.2.1.4 --- Effects of Crotalaria sessiliflora on the hepatic GSH level --- p.86 / Chapter 3.2.2.1.5 --- Histological changes of liver sections --- p.89 / Chapter 3.2.2.2 --- Hepatotoxicity within 4 days after administration --- p.92 / Chapter 3.2.2.3 --- Sub-acute hepatotoxicity within 14 days after administration --- p.93 / Chapter 3.2.2.4 --- Conclusion in hepatotoxicity study of Crotalaria sessiliflora --- p.99 / Chapter 3.2.3 --- Hepatotoxicity Study of Gynura segetum --- p.102 / Chapter 3.2.3.1 --- Correlation between the dosage of PAs present in Gynura segetum and the amount of liver tissue-bound pyrroles --- p.102 / Chapter 3.2.3.2 --- "Effects of Gynura segetum on serum ALT activity, hepatic GSH level and morphological changes of liver" --- p.104 / Chapter 3.2.4 --- Hepatotoxicity Study of Ligularia hodgsonii --- p.108 / Chapter 3.2.4.1 --- Correlation between the dosage of PAs present in Ligularia hodgsonii and the formation of liver tissue-bound pyrroles --- p.108 / Chapter 3.2.4.2 --- Effects of Ligularia hodgsonii on serum ALT activity and hepatic GSH level --- p.111 / Chapter 3.2.5 --- Hepatotoxicity Study of Tussilago farfara --- p.113 / Chapter 3.2.6 --- Hepatotoxicity Study of PA-containing medicinal herbs --- p.115 / Chapter 3.2.6.1 --- Correlation between formation of liver tissue-bound pyrroles and elevated serum ALT level --- p.115 / Chapter 3.2.6.2 --- Correlation between dosage of PAs and amount of liver tissue-bound pyrroles --- p.117 / Chapter 3.2.7 --- Test of Liver Tissue-bound Pyrroles as a biomarker using Senecionis scandentis --- p.118 / Chapter 3.2.8 --- Conclusions --- p.120 / Chapter Chapter 4 --- General Conclusions --- p.121 / Chapter 4.1 --- Qualitative and quantitative analysis of five PA-containing medicinal herbs --- p.121 / Chapter 4.2 --- Hepatotoxicity induced by PA-containing medicinal herbs in rats --- p.122 / Chapter 4.3 --- The correlation between hepatotoxicity induced by PA-containing medicinal herbs and the formation of liver tissue-bound pyrroles --- p.123 / Chapter 4.4 --- Threshold of the amount of liver tissue-bound pyrroles related to the hepatotoxicity induced by PA-containing medicinal herbs --- p.123 / References --- p.125