Biomimetic synthesis of xuxuarines Eα and Eβ: Structure revision of Rzedowskia bistriterpenoids Original Research Article

Reaction of pristimerin with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) resulted in a biomimetic-type coupling leading to xuxuarines Eα and Eβ and not the previously reported Rzedowskia bistriterpenoids I and II suggesting that the structures proposed for these natural products need revision. A product obtained in this reaction by an unusual Diels-Alder addition followed by retro-Diels-Alder-type elimination was characterized as pristimerin dicyanophenalenedione. Complete 1H, and 13C NMR spectral assignments of xuxuarines Eα and Eβ have been made by the application of 1D and 2D NMR techniques.