No description available.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2004. / Bibliography: leaves 349-350.

This study has focussed on the application of synthetic, kinetic and exploratory theoretical methods in elucidating the reaction mechanisms of four Morita-Baylis-Hillman (MBH) type reactions, viz, i) the reactions of the disulfide 2,2'-dithiodibenzaldehyde with various activated alkenes in the presence of DBU and Ph₃P, ii) the reactions of chromone-3-carbaldehydes with MVK, iii) the reactions of chromone-2-carbaldehydes with acrylonitrile and iv) with methyl acrylate. Attention has also been given to the origin of the observed regioselectivity in Michaelis-Arbuzov reactions of 3-(halomethyl)coumarins. Cleavage of the sulfur-sulfur bond of aryl and heteroaryl disulfides by the nitrogen nucleophile DBU has been demonstrated, and a dramatic increase in the rate of tandem MBH and disulfide cleavage reactions of 2,2'-dithiodibenzaldehyde with the activated alkenes, MVK, EVK, acrylonitrile, methyl acrylate and tert-butyl acrylate has been achieved through the use of the dual organo-catalyst system, DBU-Ph₃P – an improvement accompanied by an increase in the yields of the isolated products. Detailed NMR-based kinetic studies have been conducted on the DBU-catalysed reactions of 2,2'-dithiodibenzaldehyde with MVK and methyl acrylate, and a theoretical kinetic model has been developed and complementary computational studies using Gaussian 03, at the DFT-B3LYP/6-31G(d) level of theory have provided valuable insights into the mechanism of these complex transformations. Reactions of chromone-3-carbaldehydes with MVK to afford chromone dimers and tricyclic products have been repeated, and a novel, intermediate MBH adduct has been isolated. The mechanisms of the competing pathways have been elucidated by DFT calculations and the development of a detailed theoretical kinetic model has ensued. Unusual transformations in MBH-type reactions of chromone-2-carbaldehydes with acrylonitrile and methyl acrylate have been explored and the structures of the unexpected products have been established using 1- and 2-D NMR, HRMS and X-ray crystallographic techniques. Attention has also been given to the synthesis of 3-(halomethyl)coumarins via the MBH reaction, and their subsequent Michaelis-Arbuzov reactions with triethyl phosphite. An exploratory study of the kinetics of the phosphonation reaction has been undertaken and the regio-selectivity of nucleophilic attack at the 4- and 1'-positions in the 3-chloro- and 3-(iodomethyl)coumarins has been investigated by calculating Mulliken charges, LUMO surfaces and Fukui condensed local softness functions.

Orientador: Ana Maria Soares Pereira / Coorientador: Bianca Waléria Bertoni / Banca: Giuseppina Pace Pereira Lima / Banca: Silvia Helena Taleb Contini / Resumo: A espécie Justicia pectoralis (Acanthaceae) é uma planta herbácea encontrada em uma ampla distribuição geográfica entre os trópicos de Câncer e Capricórnio. No Brasil, a principal denominação popular é chambá, sendo a espécie prioritariamente utilizada em afecções do sistema respiratório. O presente trabalho visou avaliar o comprimento e diâmetro de parte aérea, massa fresca e seca de parte aérea e raiz, além dos teores de cumarina e umbeliferona utilizando dois genótipos de J. pectoralis cultivados em duas localidades, além do cultivo frente a cinco níveis de saturação por base de solo que variou de 17, 40, 60, 80 e 100%, cinco doses de esterco bovino entre os intervalos de 0, 20, 40, 60 e 80 t.ha-1 e três condições de sombreamento sendo a pleno sol, 50 e 80% de sombreamento. Quanto ao acúmulo de cumarina, as doses de esterco e os níveis de saturação por base de solo apresentaram efeito negativo. Considerando a produtividade de massa seca, a adubação com esterco promoveu aumento de biomassa. Os dois genótipos avaliados, independente do local, não apresentaram diferenças, entre si, quanto ao crescimento e acúmulos de massa fresca e seca. Na avaliação entre os genótipos, o Jp2, cultivado em Loc2, produziu maior teor de cumarina (40,20 µg.mg-1 de extrato), enquanto que o Jp1, cultivado em Loc1, apresentou maior acúmulo de umbeliferona (4,33 µg.mg-1 de extrato). Plantas cultivadas a pleno sol apresentaram maior teor de cumarina (57,90 µg.mg-1 de extrato) e acúmulo de massa seca... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: usticia pectoralis (Acanthaceae) is an herbaceous species found in a wide geographic distribution between the Cancer and Capricorn tropics. The mainly folk name In Brazil is chambá, and it is used specially for respiratory system affections. The present work aimed to evaluate the length and diameter of aerial part, fresh and dry mass of aerial part and roots, besides the coumarin and umbelliferone accumulation by using two genotypes of J. pectoralis cultivated in Loc1 and Loc2 cities. In addition, we evaluated the influence of five soil saturation levels (17, 40, 60, 80 and 100%), five doses of cattle manure (0, 20, 40, 60 and 80 t.ha-1) and three luminosity conditions (full sun, 50 and 80% of artificial shading). Both the cattle manure and the soil-based saturation levels showed a negative effect in the coumarin accumulation. Moreover, the cattle manure promoted biomass increase. Related to location, we showed that there are no differences between the growth aspects of the both two genotypes. The Jp2 genotype cultured in Loc2 produced a higher coumarin content (40.20 µg.mg-1 of extract), while the Jp1 cultured in Loc1 accumulated more umbelliferone (4.33 µg.mg-1 of extract). Plants grown in full sun showed higher coumarin content (57.90 µg.mg-1 extract) and dry mass accumulation (14.93 g) when compared to shade levels. We concluded that the best conditions to obtain greater development of J. pectoralis were ... / Mestre

A new method for the synthesis of naphthalenes has been recently discovered. The Atom Transfer Radical Cyclisation (ATRC) of diverse 2-allylphenyl2',2',2'-trichloroacetates in the presence of a Cu complex afford schloronaphthalenes in good yields using either microwave or thermolytic methods of activation. A mechanism for the benzannulation reaction is proposed and experiments presented in order to validate this hypothesis. The use of 1,3-bis(2,6-diisopropylphenyl)imidazolium copper(I) chloride [(IPr)CuCl)] along with other metal carbenes is compared to the already reported CuCl/ligand system. Since the scope and synthetic utility of this new benzannulation reaction is restricted due to the use of the MW reactor, a solvent in which the thermal reaction can take place is reported, proving its efficiency in the synthesis of a range of substituted naphthalenes. The potential and versatility of the benzannulation reaction has been investigated. Studies towards the synthesis of gilvocarcin M which contains a tetracyclicaromatic core are presented. Gilvocarcins have potential use as anti-cancer agents and represent a member of the C-aryl glycosides found in natural products. Gilvocarcin M is a challenging target because there are a sparse number of total syntheses reported in the literature. The ATRC reaction of (vinyl)phenyl trichloroacetate has also been investigated, affording the synthesis of functionalised coumarins. The mechanism of this reaction has also been investigated, establishing that, in some cases, aretro-Kharasch reaction is observed.

No description available.

No description available.

No description available.

O tratamento da ceratite por Acanthamoeba é longo, inespecífico e de baixa adesão do paciente. Assim, a busca por novas estratégias de tratamento é necessária. Extratos não aquosos de algumas espécies de Pterocaulon exibem efeito antimicótico e antiparasitário, sendo esta atividade correntemente relacionada à presença de cumarinas. Neste contexto, o presente estudo teve por objetivo o desenvolvimento de nanoemulsões contendo extrato hexânico de Pterocaulon balansae Chodat (rico em cumarinas) visando à obtenção de um produto de uso ocular com atividade amebicida. Em uma primeira etapa, o extrato hexânico foi caracterizado por cromatografia líquida de alta eficiência com detector de arranjo de diodos, detectando-se a presença de quatro cumarinas majoritárias, entre elas, a 5-metoxi-6,7-metileno dioxicumarina (5MMDC), selecionada como marcador químico do extrato vegetal. O extrato foi na sequência incorporado em nanoemulsões constituídas de um núcleo de triglicerídeos de cadeia média estabilizado por lecitina de gema de ovo, preparadas por emulsificação espontânea. Tal procedimento conduziu à obtenção de nanoemulsões monodispersas com diâmetro médio de gotícula de aproximadamente 200-300 nm, independente da quantidade de extrato adicionado à formulação (1,0 a 5,0 mg/mL). A atividade amebicida das formulções contra Acanthamoeba castellanii foi dependente da dose e do tempo de incubação, sendo 24 horas e a concentração de 1,25 mg/mL de extrato considerada como ótima (~5% de viabilidade), com efeito similar ao controle clorexidina. Enfim, os estudos de citotoxicidade in vitro demonstraram que as células de epitélio de córnea humana (HCE) não foram afetadas com a incubação com as nanoemulsões através do ensaio de MTT. Esses resultados sugerem o potencial do extrato hexânico, rico em cumarinas de Pterocaulon balansae, associado a nanoemulsões como uma nova estratégia para o tratamento da ceratite ocular causada por Acanthamoeba. / Treatment for keratitis caused by Acanthamoeba is unspecific, long term and with low patient compliance, being the search of new treatment strategies a need. Non-aqueous extracts of some species of Pterocaulon exhibit antimycotic and anti-parasitic activity, usually attributed to the presence of coumarins. In this scenario, the aim of this work is the development of nanoemulsion to associate the coumarin-rich n-hexane extract of Pterocaulon balansae. Previously, the extract was prepared and characterized by high performance liquid chromatography with photodiode array detector. The presence of 4 major coumarins was detected, where 5-methoxy-6,7-methylene dioxycoumarin (5MMDC) was selected as chemical marker. This extract was associated to nanoemulsions composed of egg lecithin and medium chain triglycerides, prepared by spontaneous emulsification. The physicochemical characterization showed the formation of monodisperse nanoemulsions with 200-300 nm diameter, regardless the amount of extract incorporated (1.0-5.0 mg/mL). The amoebicidal activity of the formulations against Acanthamoeba castellanii was both dose-dependent and incubation time-dependent, being 24h of incubation and concentration of 1.25 mg/mL of the extract the optimal (~5% viability), with effect similar to chlorexidine control. Finally, in vitro cytotoxicity studies showed that human corneal epithelial cells were unaffected after incubation with nanoemulsions by MTT assay. These results suggest a potential of the coumarin-rich n-hexane extracts of Pterocaulon balansae associated to nanoemulsion as a new strategy for the treatment of ocular keratitis caused by Acanthamoeba.

Cumarinas são metabólitos secundários de plantas encontrados majoritariamente nas espécies das famílias Asteraceae, Rutaceae e Umbeliferae. Quimicamente, são compostos fenólicos, formados pela fusão de um benzeno e de um anel α-pirona, chamados de benzopironas. Elas apresentam diversas propriedades farmacológicas, associadas com baixa toxicidade. Nosso grupo de pesquisa sintetiza cumarinas pela reação de Pechmann, que ocorre através da condensação de um fenol com um β-cetoéster, na presença de um ácido de Bronsted ou Lewis. Um dos trabalhos mais recentes foi a síntese de 6-metil-4-clorometilcumarinas com um IC50 menor do que 1,6 μM para atividade antitripanocida. Em outro trabalho, um grupo de compostos de híbridos cumarina-triazol foi sintetizado e apresentou potencial atividade como agente antitumoral. Baseado nesses trabalhos, foi planejado a síntese de análogos da 6-metil-4-clorometilcumarina via condensação de Pechmann, com diferentes substituintes na posição 6, obtidos através das reações de click chemistry, no intuito de aumentar a atividade antioxidante desses compostos. Assim, para obter esses compostos, foi realizada uma condensação de Pechmann com hidroquinona e 4-cloroacetoacetato de etila. Após, uma eterificação de Williamson com brometo de propargila foi feita. Finalmente, a reação de click chemistry foi realizada sob irradiação de micro-ondas com diversas azidas previamente sintetizadas no laboratório, conduzindo à obtenção de diversos análogos da 6-metil-clorometilcumarina que foram avaliados quanto a viabilidade celular através ensaio do MTT (brometo de 3-(4,5-dimetiltiazol-2-il)-2,5-difeniltetrazólio). Também foi testada a sua capacidade antioxidante pelo método do DCFH-DA (diacetato de 2’,7’ –diidroclorofluoresceína). Dessa maneira, sob as condições reacionais utilizadas neste trabalho, foi possível sintetizar 12 compostos inéditos com rendimentos entre 9 e 61%. Os ensaios biológicos preliminares indicaram que os compostos sintetizados apresentam potencial atividade antioxidante e algumas moléculas tiveram potencialidade como agente citotóxico. / Coumarins are secondary plant metabolites typically found in species of the Asteraceae, Rutaceae and Umbeliferae families that demonstrate diverse pharmacological properties associated with low toxicity to humans. Chemically, they are phenolic compounds characterized by the fusion of benzene with an α-pyrone ring, yielding the benzopyrone nucleus. Our research group usually synthesizes coumarins by the Pechmann reaction, through the condensation of phenols with β-ketoesters catalyzed by Bronsted or Lewis acids. One of the most recent works performed at our laboratory describes the synthesis of 6-methyl-4-chloromethylcoumarins with an IC50 of 1.6 μM concerning the anti-trypanocidal activity. Another work described the syntheses of coumarin-triazole hybrids with potential activity as anticancer agents. Based on the previous works, it was designed the synthesis of 4-chloromethylcoumarins via Pechmann condensation with several substituents at the position 6 of the coumarin ring through click chemistry reactions to improve their antioxidant activities. The synthesis of the coumarins started with Pechmann condensation using hydroquinone and ethyl 4-chloroaceacetate followed by functionalization of the phenolic hydroxyl with propargyl bromide via Williamsom ether synthesis. Subsequently, the click chemistry reactions were performed under microwave irradiation using different organic azides previously synthesized at our laboratory, yielding several 6-substituted-4-chloromethylcoumarin analogues which were evaluated for cell viability through MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Their antioxidant capacity was also tested by the DCFH-DA (2’,7’–diihydrochlorofluorescin diacetate) method. Therefore, under the reaction conditions used in this study, it was possible to synthesize 12 novel compounds with yields between 9 and 61%. Preliminary biological assays indicated that the compounds synthesized have potential antioxidant activity and some molecules had potential as an antitumor agent.