Efforts toward the Total Synthesis of Elisabethin A.

We describe our efforts toward the total synthesis of the natural product elisabethin A. The first route was guided by the proposed biosynthesis, assembling the 6,6-ring system before forming the five-membered ring including the quaternary carbon. The second approach includes a high yielding cyclization under Mitsunobu conditions as a key step. It allowed the preparation of an unusual and highly functionalized bicyclic 6,5-spiro compound. Both routes share a common advanced precursor obtained from an "underdeveloped" Claisen rearrangement of an aryl dienyl ether.