6 documents found, page 1 of 1
The Chemistry of the Sesquiterpene Alkaloids
Brocksom,Timothy J.; Oliveira,Kleber T. de; Desiderá,André L.We present the occurrence, structures, biological activities, biosynthesis, and syntheses of the sesquiterpene alkaloids.
Anticonvulsant activity of thymoquinone and its structural analogues
Sousa,Damião P. de; Nóbrega,Franklin F. F.; Santos,Camila C. M. P.; Benedito,Rubens B.; Vieira,Ygor W.; Uliana,Marciana P.; Brocksom,Timothy J.It has been widely reported that the crude oil of Nigella sativa L., Ranunculaceae, seeds and its major chemical component thymoquinone present anticonvulsant activity. These facts led us to verify the pharmacological potential of five structurally related para-benzoquinones on the pentylenotetrazol-induced seizures model, and establish the structural characteristics that influence the anticonvulsant activity o...
Oxidation of mono-phenols to para-benzoquinones: a comparative study
Uliana,Marciana P.; Vieira,Ygor W.; Donatoni,Maria Carolina; Corrêa,Arlene G.; Brocksom,Ursula; Brocksom,Timothy J.The oxidation of mono-phenols to para-benzoquinones is of continuing interest due to the existence of numerous natural products containing this structural unit. The chemical reactivity of para-benzoquinones is also noteworthy, as oxidants and dienophiles in the Diels-Alder reaction. We have used for quite some time now, molecular oxygen and catalysis with [CoII(salen)] as the oxidation procedure, but felt the n...
The enantioselective synthesis of (R)-(+)-6-isopropenyl-3-methyl-2-cycloheptenone
Brocksom,Timothy J.; Brocksom,Ursula; Barbosa,Fernanda P.(R)-(+)-6-isopropenyl-3-methyl-2-cycloheptenone is synthesized from (R)-(-)-carvone by reduction and trialkylsilyl-enolether formation, cyclopropanation with methylene iodide and diethylzinc, followed by a Saegusa type oxidation with ferric chloride and finally dehydrochlorination with base. The title compound is obtained in five steps and 38% overall yield, being a useful chiron for guaiane sesquiterpene natur...
A novel dihydroxy nor-guaiane sesquiterpene: synthesis and crystal structure an...
Zukerman-Schpector,Julio; Caracelli,Ignez; Carvalho,Cristina C.; Faria,Mary L. de; Silva,Fernando C.; Matias,Luiz G. de O.; Brocksom,Timothy J.The epoxidation (H2O2, NaOH) of an acetonyl-cycloheptenone derived from (R)-(-)-carvone gives a dihydroxy-nor-guaiane sesquiterpene by way of an interesting sequence of reactions promoted by the basic reaction conditions. Although the major product could be identified spectroscopically with respect to functional groups, its complete three dimensional structure was determined by X-ray mono-crystal diffraction st...
A síntese de um furano-guiano
Brocksom,Timothy J.; Canevarolo,Elisabete T.A síntese de lactonas sesquiterpênicas do tipo guaiano é de interesse devido as atividades biológicas associadas às estruturas complexas deste grupo de produtos naturais. Planejou-se a sua síntese a partir de monoterpenos abundantes isolados de óleos essenciais brasileiros. Assim p-ment-l-eno foi transformado em 2-bromo-6-isopropil-3-metil-ciclohept-2-enona por adição de dibromocarbeno, expansão de anel com rea...