Structures of Zeylenol and Zeylena, Constituents of Uvaria zeylanica (Annonaceae)

From the methanol extract of the roots of Uvaria zeylanica (Annonaceae), two new crystalline compounds, named zeylenol and zeylena, have been isolated. Evidence is presented that zeylenol, C₂₁H₂₀O₇, a minor constituent, has structure la and that zeylena, C₂₃H₂₀O₅, a major constituent, has structure 3a. Benzene oxide 6 is an apparent biogenetic precursor for these two and many other substances found in Uvaria species; its conversion to zeylena (3a) involves addition of (E)-cinnamic acid followed by an intramolecular Diels-Alder reaction.