In considering approaches to the total synthesis product. Such a general scheme has not only of polycyclic natural products, such as the di-and been successful in our hands4v5 but has also led to triterpenes, we adopted a~ lan3-~ that would the syntheses of cy- onocerin,'olean-1 1, 12; 13) 18-construct first the A/B ring system, which could diene,'and pentacyclosqualene8 by other workers. then be elaborated further to the desired end ...
