21.Synthetic Study of 1,3-Butadiene-Based IMDA Approach to Construct a [5-7-6] Tricyclic Core and Its Application to the Total Synthesis of C8-epi-Guanacastepene O

C. C. Li, C. H. Wang, B. Liang, X. H. Zhang, L. J. Deng, S. Liang, J. H. Chen*, Y. D. Wu*, Z. Yang*

J. Org. Chem., 2006, 71, 6892.

An efficient intramolecular Diels−Alder (IMDA) strategy for the construction of the [5−7−6] tricyclic core (18) of guanacastepenes has been developed from cis– and trans-1,3-butadiene-tethered 4-oxopent-2-ynoic acid ethyl esters 10 and 11. This method facilitates the synthesis of C8-epi-guanacastepene O (36) in a very efficient manner.