Megastigma‐5,8‐dien‐4‐on, ein Aromastoff der gelben Passionsfrucht und des Virginia‐Tabaks

Megastigma‐5,8‐dien‐4‐one, an aroma constituent of the yellow passion fruit and Virginia tobacco Preparative gas chromatography allowed isolation of megastigma‐5, 8 (E)‐dien‐4‐one (3) from small subfractions of both yellow passion fruit and Virginia tobacco condensates. Along with 3, the Z‐isomer 4 occurs in the aroma of the yellow passion fruit. Both these novel flavor compounds were synthesized by a two‐step, non‐biomimetic route starting from 2, 6, 6‐trimethylcyclohex‐2‐en‐1‐one. The E‐isomer 3 was also formed by acid‐catalyzed dehydration/rearrangements of ionol‐ and damascol monoepoxides 5, 6, 7, 8 and hydroxy‐ionols and ‐damascol 9, 10 and 11. Such a biomimetic conversion indirectly supports the assumption that 3 and 4 might originate from the oxidative degradation of carotenoid precursors possibly related to canthaxanthine.