Stereoselective Total Synthesis of Sesquiterpenoids: (-)-Ylangocamphor, (-)-Ylangoborneol and (-)-Ylangoisoborneol

Abstract

The tricyclic sesquiterpenoids (-)-ylangocamphor (1), (-)-ylango-borneol (2), and (-)-ylangoisoborneol (3) are structurally, and presumably, biogenetically very closely related to (+)-copacamphor (4), (+)-copaborneol (5), and (+)-copaisoborneol (6), respectively. Of these six compounds, only one [(+)-copaborneol (5)] has been isolated from natural sources (Pinus silvestris L.).³ We have previously reported⁴ the preparation of the above three “copa” sesquiterpenoids (4, 5, 6) and report here the stereoselective total synthesis of the three “ylango” sesquiterpenoids (1, 2, 3).⁵