Expedient route to the tigliane-daphnane skeleton via oxonium ylide [1,2]-shift
Craig Stewart1, Robert McDonald, F G West
1Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Centre, Edmonton, AB T6G 2G2, Canada.
Abstract:
A short, stereoselective approach to the fused tricyclic carbon skeleton found in the tigliane and daphnane classes of diterpene natural products is described. Convergent coupling of the A- and C-rings, followed by diastereoselective cerium enolate addition and formation of a double acetal set the stage for generation of an oxonium ylide via a transient metallocarbene. An efficient Stevens [1,2]-shift furnished the 7-membered B-ring, possessing the bridgehead oxygenation pattern found in the natural systems.
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