Síntese e avaliação da fitotoxicidade de novas lactonas sesquiterpênicas

• Autor(a) principal: Arantes, Francisco Frederico Pelinson
• Data de Publicação: 2007
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2167
• topic: α-santonina; Herbicida; Lactonas sesquiterpênicas; α-santonine; Herbicide; Sesquiterpe lactones; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ORGANICA

Sesquiterpene lactones represent an important group of secondary metabolites of the Asteraceae family. As the availability of natural sesquiterpene lactones is very limited, being many times insufficient for detailed studies of their bioactivity, the present investigation had as objective the synthesis of sesquiterpene lactones derivatives from α-santonin, aiming studies about the biological structure-activity relationship and the discovery of new compounds with potential herbicide activity. In this present work eleven compounds were synthesized [20]-[30], five among them are unknown. These compounds were prepared by different types of reactions including photochemistry, reduction, oxidation and esterification reactions. When α-santonin [9] was irradiated with high pressure mercury lamp, using anhydrous acetic acid as solvent in borosilicate reactor, 10α- acetoxy-3-oxo-1,7αH,6,11βH-guai-4-en-6,12-olide [20] was obtained, in 26% yield. Using acetic acid/water mixture 1:1 v/v, keeping the other conditions, the iso-foto-santonic acid [21] and the 10α-hydroxy-3-oxo-1,7αH,6,11βH-guai-4-en-6,12-olide [22] were obtained in 44% and 32% yields, respectively. When the α-santonine was submitted to the photochemistry reaction in a quartz reactor, using low pressure mercury lamp as source of ultraviolet radiation and acetonitrile as solvent, the lumisantonin [23] was produced in 83% yield. The compounds [20] and [22] were submitted to the reduction reaction with sodium borohydride, obtaining 10α-acetoxy-3β-hidroxy-1,7αH,6,11βH-guai-4-en-6,12-olide [28] and the 3β,10α-hydroxy-1,7αH,6,11βH-guai-4-en-6,12-olide [30] in 86% and 72% yields, respectively. To obtain 10α-acetoxy-3β-crotonoil-1,7αH,6,11βH-guai-4-en-6,12-olide [29] (63%), the compound [28] reacted with crotonoil chloride, in the presence of pyridine. The 3-oxo-7αH,6βH-eudesma-1,4,11-trien-6,12-olide [25] was obtained in 72% yield and, it was prepared by the initial reaction of the α-santonine with phenyl selenium chloride (PhSeCl) and subsequent oxidation with hydrogen peroxide (H2O2). Then, the lactone [25] was submitted to the photochemistry reaction in a quartz reactor, using anhydrous acetic acid as solvent, and the compounds 10α-acetoxy-3-oxo-1,7αH,6βH-guai-4,11-dien-6,12-olide [26] and 11,13 deidrolumisantonin [27] were obtained in 4,5% and 18% yields, respectively. The compounds [20] and [30] were submitted to biological assays to evaluate their activities on the germination and on the radicular growth of cucumber (Cucumis sativus) and sorghum plants (Sorghum bicolor x Sorghum sudanensis). Amongst all evaluated compounds, the compound [20] was the one that presented higher activity on the radicular growth of the cucumber and sorghum plantules, being inhibitions of 53,5% and 66,7% observed, respectively. Low or no significant inhibitory activity was observed on the germination of the cucumber and sorghum seeds.