RESUMO
From the leaves of Xylopia vielana (Annonaceae) the three dimeric guaianes vielanin A-C were isolated and structurally elucidated by mass and NMR spectroscopy as 1-3. The structure of 1 contains a bridged ring system formed probably via a Diels-Alder reaction of two different guaiane monomers. Compounds 2 and 3 represent symmetric cyclobutanes formally generated from two equal guaiane moieties by [2 + 2] cycloaddition.
Assuntos
Cicloeptanos/isolamento & purificação , Plantas Medicinais/química , Sesquiterpenos de Guaiano , Catequina/química , Catequina/isolamento & purificação , Cicloeptanos/química , Espectroscopia de Ressonância Magnética , Folhas de Planta/química , Quercetina/análogos & derivados , Quercetina/química , Quercetina/isolamento & purificação , Espectrometria de Massas por Ionização por Electrospray , VietnãRESUMO
Two new beta-carboline alkaloids, hedyocapitelline and hedyocapitine, were isolated from Hedyotis capitellata var. mollis (Rubiaceae). Their structures were elucidated by spectroscopic data (1)H- and (13)C-NMR, MS, IR, UV).
RESUMO
The major constituent of the alkaloid fraction of leaves of PARAVALLARIS MACROPHYLLA Pierre was found to be the new paravallarine-type steroidal alkaloid, 20-epi-kibataline. The molecular and crystal structure of this steroidal alkaloid were determined by X-ray analysis.
