Isolation and Biomimetic Synthesis of (±)-Guajadial B, a Novel Meroterpenoid from Psidium guajava

(+/-)-Guajadial B (1), an unusual humulene-based meroterpenoid, was isolated as a racemate from the leaves of Psidium guajava, collected from Vietnam. The structure of this novel secondary metabolite was established on the basis of extensive analysis of NMR spectra and confirmed by biomimetic synthesis in a domino three-component coupling reaction.