Structure Determination of New Iridals from Iris pallida and Iris foetidissima

Article abstract of DOI:10.1002/hlca.19910740838

The four novel iridals 8-10 and 18 were isolated from rhizome extracts of Iris pallida and Iris foetidissima, and their structures were established by spectroscopic methods and oxidative degradation.The compounds 8-10 bearing a conjugated triene moiety are extremly labile and decompose rapidly.Thus, the monocyclic triene 8 was only isolated after its conversion to a Diels-Alder adduct with 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione (14).The tricyclic iridal 18 is a hitherto unknown precursor of α-irone.The possible biogenesis of these unusual triterpenoids is discussed.