QSAR, voltametria cíclica e cálculo de potenciais de redução de 4-aril-3-bromo-5-arilidenofuran-2(5H)-onas análogas aos rubrolídeos

• Ano de defesa: 2011
• Autor(a) principal: Lage, Mateus Ribeiro
• Orientador(a): Maltha, Célia Regina álvares
• Banca de defesa: Reis, Efraim Lázaro , Alcântara, Antônio Flávio de Carvalho
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Agroquímica
• Departamento: Agroquímica analítica; Agroquímica inorgânica e Físico-química; Agroquímica orgânica
• País: BR
• Palavras-chave em Português: Voltametria; Rubrolídeos; Fitotoxicidade
• Palavras-chave em Inglês: Voltammetry; Rubrolides; Phytotoxicity
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ORGANICA
• Link de acesso: http://locus.ufv.br/handle/123456789/2108

The γ-alquilidenobutenolides are organic compounds isolated from natural sources that have important biological activities. Among these compounds the rubrolides, which consist of a five-member substituted lactone ring, are of high relevance. The rubrolides have structural similarity to the nostoclides, which have a well-recognized herbicidal activity. In this work we analyze structural, electronic and thermodynamic properties of a set of rubrolides that were previously synthesized in the Agrochemicals’ Analysis and Synthesis Laboratory (LASA) of the Chemistry Department of UFV, which are known by their phytotoxic activities. Starting with the assumption that the herbicidal activity of the rubrolide’s analogues arises from the same activity of inhibiting the Hill reaction, which occurs in photosystem II of the photosynthesis, in the present study the structural and electronic properties of these compounds were analysed in order to extract relevant information to the understanding of the mechanism of action of this class of substances. QSAR analysis was performed using the phytotoxic activity as the dependent variable and various molecular descriptors as independent variables. The QSAR studies indicated the existence of correlations between biological activity and the FNSA3 molecular descriptor and also with the energies of the frontier orbitals (HOMO, LUMO and LUMO+1). Larger fractions of negative surface area or more negative energy values for the frontier orbitals result in compounds with higher activity. This is achieved with electron-attractor substituents, as experimentally observed. Besides the QSAR study DFT calculations were performed for the determination of the reduction potentials, which were also experimentally determined by cyclic voltammetry. The B3LYP/6-31g(d,p) method reproduced the best results as compared to experimental data.