Síntese e fitotoxicidade de ozonídeos substituídos derivados de 8-oxabiciclo[3.2.1]oct-6-en-3-onas

• Autor(a) principal: Cusati, Raphael Campos
• Data de Publicação: 2008
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2070
• topic: Cátion oxialílico; Cicloadição [4+3]; Ozonídeos; Fitotoxicidade; Oxyallyl carbocations; [4+3] cycloadition; Ozonides; Phytotoxicity; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ANALITICA

Artemisinin is a sesquiterpene lactone isolated from the leaves of Artemisia annua L. It has been demonstrated that this lactone exhibits phytotoxic activity against various monocotyledonous and dicotyledonous species. The observed biological activity has been associated with the presence of the endoperoxide moiety in the structure of this compound. In the present investigation, a series of ozonides, possessing the endoperoxide moiety, was synthesized and evaluate in terms of their phytotoxic activities. The ozonides were prepared from substitutes 8-oxabicyclo[3.2.1]oct-6-en-3-ones, which were obtained via [4+3] cycloaddition between oxyallyl carbocations and pertinent furans. The carbocations, in turns, were generated in situ from the 2,7-dibromocycloheptanone, 2,4-dibromopentan-3-one e 3,5-dibromoheptan-4-one. Eigth ozonides were synthesizes namely ozonide of (1α,6α,2β,5β)- 12-oxatricyclo-[4.4.1.12,5]-dodec-3-en-11-one (50%), ozonide of 2-methyl-(1α,6α,2β,5β)-12-oxatricyclo- [4.4.1.12,5]-dodec-3-en-11-one (37%), ozonide of 2-ethyl- (1α,6α,2β,5β)-12-oxatricyclo-[4.4.1.12,5]-dodec-3-en-11- one (42%), ozonide of 2,3-dimethyl-(1α,6α,2β,5β)-12- oxatricyclo-[4.4.1.12,5]-dodec-3-en-11-one (28%), ozonide of 2,5-dimethyl-(1α,6α,2β,5β)-12-oxatricyclo-[4.4.1.12,5]- dodec-3-en-11-one (55%), ozonide of 2-acetyl-(1α, 6α, 2β, 5β)-12-oxatricyclo-[4.4.1.12,5]-dodec-3-en-11-one (24%), ozonide of 2,6,9 α,11 α-tetramethyl-12-oxatricyclo[6.3.1.03,8] dodec-2-en-10-one (92%) and ozonide of 9 α,11 α-diethyl-2,6-dimethyl-12-oxatricyclo[6.3.1.03,8]dodec-2- en-10-one (76%). The phytotoxic activity of the synthesized ozonides as well as the cycloadduct precursors, was evaluated against sorghum (Sorghum bicolor L.) and cucumber (Cucumis sativus L.), at 5.0 x 10-4 mol L-1. Among the oxabicyclos, the most phytotoxic substance was 2-acetyl- (1α, 6α, 2β, 5β)-12-oxatricyclo-[4.4.1.12,5]-dodec-3-en- 11-one, inhibiting the root growth of cucumber and sorghum by 82.1% and88.5%, respectively. Concerning the ozonides, the best result was achieved with compound ozonide of 2,3- dimethyl-(1α, 6α, 2β, 5β)-12-oxatricyclo-[4.4.1.12,5]-dodec- 3-en-11-one which inhibited root growth of cucumber and sorghum by 84.2% and 80.2%, respectively.