Experiments Directed toward the Total Synthesis of Terpenes. IX. The Total Synthesis of (±)-Hibaene and the Oxygenation of Some Tetracyclic Diterpenes

Abstract

Conversion of the keto acetal 19 to the hydroxy olefin 26, a model for the C/D ring system of steviol 18, is delineated. Acid-catalyzed rearrangement of this hydroxy olefin 26 provides entry to the hibaene-stachene system, and the synthesis of racemic hibaene 28 is described. Photosensitized oxygenation of (±)-isokaurene 12 and the analogous olefin 15 provides a pathway for the introduction of hydroxyl functions into these molecules and the synthesis of the C/D ring system of the diterpenoid alkaloids. Show more