Isolation and Structure Determination of the Precursors of a-and y-Irone and Homologous Compounds from Iris pallida and Iris florentina

Rhizomes of Iris pallida and Iris florentina contain - increasing on storage - violet-like smelling C14-ketones (irones 1 a-c) which develop by oxidative degradation of C31-triterpenoids. The structure of these precursors is reported as well as the structure of respective C30-homologues. The unusual C31-structures may derive biogenetically from the respective C30 compounds by a methylation which initiates the formation of the ring-closed irone-moiety