The chemistry of a series of para-hydroquinones substituted in the 2,5-positions with a proton accepting amine group has been investigated. The p-hydroquinones are designed with bis-bidentate coordination pockets allowing for the bridging of two metals and extended multimetallic complexes. Several aspects of the hydroquinones chemistry was examined, including the redox behaviour and properties of the hydroquinones while in their free forms, complexed to palladium and complexed to boron. The redox properties of para-hydroquinones which contain intramolecular hydrogen bonds as indicated by X-ray structural and spectroscopic data were examined. The cyclic voltammograms of some of these hydroquinones indicated they could be oxidized reversibly to give dicationic benzoquinones. The oxidized forms have been chemically isolated and characterized for the first time. Characterization data of the dicationic benzoquinones revealed the OH protons are transferred intramolecularly to the adjacent nitrogen bases. Spectroscopic solution data for the p-benzoquinone dications suggests that the intramolecular hydrogen bonds in the redox related p-hydroquinone are no longer present. A correlation between the oxidation potential of the 2,5-substituted-p-hydroquinone and base strength of the nitrogen substituent was shown to exist. The bis-bidentate p-hydroquinones were coordinated to palladium resulting in dinuclear complexes. The non-innocence of the ligand was preserved upon coordination but the complexes are oxidized at more positive potentials in comparison to the analogous p-benzoquinone species. Two of the palladium complexes were chemically oxidized resulting in the semiquinone radical redox state of the ligand. The EPR and UV-vis spectroscopy of the radical p-semiquinone palladium complexes indicates their properties are similar to o-semiquinone palladium complexes. The bis-bidentate p-hydroquinones and some related ligands were also coordinated to the main group element, boron. Cyclic voltammetry of the boron complexes revealed the redox properties of the bridging p-hydroquinone were perturbed and redox processes occurred at even more positive potentials in comparison to the analogous palladium complexes. The dinuclear boron complexes were highly fluorescent with quantum yields calculated to be in the range of 0.36-0.52. These boron complexes incorporated an uncommon ancillary ligand, acetate. The acetate ligand was found to be advantageous for the solubility and fluorescence properties for one of the boron compounds in comparison to the analogous boron complex incorporating the more commonly used fluorine ancillary ligand. / Graduate / 0490 / 0488 / 0485

As part of our ongoing investigations for anticancer drugs from rainforestflora, five plant extracts were determined to contain interesting bioactivity. These extracts were subjected to various separation techniques, affording a number of bioactive compounds that were then characterized by spectral and degradative methods. A methanol extract of Cestrum latifolium Lam. yielded the known compound parissaponin Pb. Hydrolysis afforded its aglycone, the known spirostanol diosgenin. GCMS analysis characterized the derivatized, hydrolyzed sugars. Previous investigations of Albizia subdimidiata provided two saponins including the new compound albiziatrioside A. The sugar moieties of these two compounds required further characterization. They were characterized by spectral analysis of the partially hydrolyzed products and by GCMS analysis of the hydrolyzed sugars. Pittoviridoside, a saponin from Pittosporum viridiflorum, was isolated in a previous investigation. Further investigation was required to characterize the stereochemical environment of the sugar moiety. The stereochemistries of the pentose sugars were determined by conversion into thiazolidine acetates of known stereochemistries and analysis with standards by GCMS. Two new diterpenes were isolated from Hymenaea courbaril, which in an earlier investigation provided a new diterpene. The absolute configurations of these diterpenes were assigned on the basis of anisotropic NMR studies, X-ray crystallography, circular dichroism analysis and previously reported literature. A previous investigation of Miconia lepidota isolated two benzoquinones, primin and its n-heptyl analog. Fifteen analogs were synthesized for structure-activity relationship determination. It was found that benzoquinones with moderate-length alkyl side chains displayed the strongest activity in our yeast and cancer cell lines. / Ph. D.

Reproduction de : Thèse de doctorat : Pharmacie. Chimie thérapeutique : Nantes : 2008. / Bibliogr.

Made available in DSpace on 2014-10-09T12:35:54Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:26Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:35:54Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:26Z (GMT). No. of bitstreams: 0 / Observações feitas pelo próprio autor sugerem potencial ação do Líquido da Castanha de Caju (LCC) na pigmentação da pele, ação esta semelhante a da hidroquinona. O LCC é um líquido contido na casca da castanha de caju, possui característica de resina líquida, bastante viscosa e de odor forte, sua coloração varia de marrom claro, escuro a preto, dependendo do método de extração utilizado, podendo ser denominado de Natural ou Técnico. Este estudo propôs cultivar melanócitos e queratinócitos em cocultura e posteriormente tratálos com LCC. A L-DOPA, agente estimulador da melanogênese, via da produção de melanina, responsável pela pigmentação da pele, foi utilizada na cocultura para avaliar a ação do LCC. A hidroquinona, conhecido inibidor desta via, foi utilizada na cocultura como controle positivo para o LCC, visto que este poderia apresentar ação semelhante a da hidroquinona. Para a utilização do LCC na cocultura, testes de solubilidade do mesmo para posterior dispersão no meio de cultura, foram necessários, bem como a identificação de seu potencial cito e fototóxico in vitro. Para a realização do teste de fototoxicidade foi construída uma câmara específica, atendendo as normas exigidas pelos guias ©ECVAM DB-ALM: INVITTOX protocol e OECD TG-432, sendo esta qualificada por método validado. Os testes realizados com o LCC (natural e técnico) indicaram potencial ação destes na pigmentação da pele, estimulando a proliferação de melanócitos em cocultura. Este perfil apresentado, pelos extratos de LCC, é contrário ao da hidroquinona, e ao esperado inicialmente, sendo necessário aprofundar estes estudos. No entanto, estes resultados são promissores, sugerindo a descoberta de um novo tratamento para hipocromias. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Thesis (Ph.D. in Toxicology) -- University of Colorado Denver, 2007. / Typescript. Includes bibliographical references (leaves 158-180). Free to UCD affiliates. Online version available via ProQuest Digital Dissertations;

A presente tese apresenta: I - Uma revislo bibliográfica sobre os adutos de Diels-Alder entre benzoquinonas 2-mono-substituídas ou benzoquinona não-substituída e ciclopentadieno; II - Uma visão mecanística, de literatura, sobre as reações de ciclo-adição; III - A síntese, por nós efetuada, de uma série de adutos de Diels-Alder entre ciclopentadieno e benzoquinonas 2-mono-substituídas por cloro, bromo, ou ainda, substituintes contendo nitrogênio, oxigênio, enxofre ou selênio; IV - O estudo que empreendemos sobre a fotociclização dos adutos acima mencionados. Na obtenção dos adutos, foram empregados dois métodos distintos: a reação de Diels-Alder e a substituição do halogênio por nucleófilos, nos adutos halogenados. Nove adutos inéditos foram isolados e caracterizados. A estereoquímica dos treze adutos preparados foi esclarecida por RMN de 13C e de 1H. O estudo da fotociclização dos adutos visava dois aspectos: sintético, para a obtenção de compostos-gaiola, e mecanístico. Foram isolados e caracterizados sete novos compostos-gaiola. Foi sugerido o mecanismo das referidas fotociclizações, através das determinações dos rendimentos quânticos e dos resultados de voltametria cíclica. Foi, também, fornecida uma possível explicação para a falta de reatividade fotoquímica de alguns adutos. / This thesis contains: I - A literature review about cyclopentadiene Diels-Alder adducts of benzoquinone and its 2-mono-substituted derivatives; II - A mechanistic overview of cycloaddition reactions; III - The synthesis of a series of Diels-Alder adducts of cyclopentadiene and 2-mono-substituted (by chloro-, bromo- or groups containing nitrogen, oxigen, sulfur or selenium) benzoquinones; IV - The investigation about the photocyclization of the same adducts. Two different methods were employed for the obtention of these adducts: either the Diels-Alder reaction, or the substituition of the halogen by nucleophiles, in the halo-containing adducts. Nine previously unreported adducts were isolated and characterized. The sterochemistry of the thirteen adducts prepared was determined through 13C and 1H NMR. The investigation about the photocyclization of the adducts had two main objectives: the synthesis of the corresponding cage-compounds and the elucidation of the photocyclization\'s mechanism. Seven new cage-compounds, previously unreported, were obtained and characterized. Quantum yield determinations and cyclic voltammetry data led to the proposition of a mechanism for the photocyclization reactions. An explanation for the lack of photoreactivity presented by some adducts was also furnished.

L'étude de la photoréactivité du couple méthoxy-p-quinone/méthoxyhydroquinone en solution a permis d'appréhender son importance dans la photodégradation des pâtes à papier à haut rendement. Le mécanisme de la photocyclisation de phényl-p-benzoquinones et d'un analogue, la 4,4'-diméthoxybiphényle-2,5,2',5'-diquinone issue du couplage entre la méthoxy-p-quinone et la méthoxyhydroquinone, a été déterminée par irradiation continue et spectroscopie résolue dans le temps.

A presente tese apresenta: I - Uma revislo bibliográfica sobre os adutos de Diels-Alder entre benzoquinonas 2-mono-substituídas ou benzoquinona não-substituída e ciclopentadieno; II - Uma visão mecanística, de literatura, sobre as reações de ciclo-adição; III - A síntese, por nós efetuada, de uma série de adutos de Diels-Alder entre ciclopentadieno e benzoquinonas 2-mono-substituídas por cloro, bromo, ou ainda, substituintes contendo nitrogênio, oxigênio, enxofre ou selênio; IV - O estudo que empreendemos sobre a fotociclização dos adutos acima mencionados. Na obtenção dos adutos, foram empregados dois métodos distintos: a reação de Diels-Alder e a substituição do halogênio por nucleófilos, nos adutos halogenados. Nove adutos inéditos foram isolados e caracterizados. A estereoquímica dos treze adutos preparados foi esclarecida por RMN de 13C e de 1H. O estudo da fotociclização dos adutos visava dois aspectos: sintético, para a obtenção de compostos-gaiola, e mecanístico. Foram isolados e caracterizados sete novos compostos-gaiola. Foi sugerido o mecanismo das referidas fotociclizações, através das determinações dos rendimentos quânticos e dos resultados de voltametria cíclica. Foi, também, fornecida uma possível explicação para a falta de reatividade fotoquímica de alguns adutos. / This thesis contains: I - A literature review about cyclopentadiene Diels-Alder adducts of benzoquinone and its 2-mono-substituted derivatives; II - A mechanistic overview of cycloaddition reactions; III - The synthesis of a series of Diels-Alder adducts of cyclopentadiene and 2-mono-substituted (by chloro-, bromo- or groups containing nitrogen, oxigen, sulfur or selenium) benzoquinones; IV - The investigation about the photocyclization of the same adducts. Two different methods were employed for the obtention of these adducts: either the Diels-Alder reaction, or the substituition of the halogen by nucleophiles, in the halo-containing adducts. Nine previously unreported adducts were isolated and characterized. The sterochemistry of the thirteen adducts prepared was determined through 13C and 1H NMR. The investigation about the photocyclization of the adducts had two main objectives: the synthesis of the corresponding cage-compounds and the elucidation of the photocyclization\'s mechanism. Seven new cage-compounds, previously unreported, were obtained and characterized. Quantum yield determinations and cyclic voltammetry data led to the proposition of a mechanism for the photocyclization reactions. An explanation for the lack of photoreactivity presented by some adducts was also furnished.