Evolution of a Polyene Cyclization Cascade for the Total Synthesis of (-)-Cyclosmenospongine
1Department of Chemistry and Pharmacy, Ludwig Maximillians University Munich, Butenandtstrasse 5-13, 81377, Munich, Germany.
Abstract:
We report a full account on the development of a unique cationic polyene cyclization for the total synthesis of the tetracyclic meroterpenoid (-)-cyclosmenospongine. A highly convergent three-component coupling strategy enabled rapid access to individual cyclization precursors that were tested for their reactivity. The successful transformation generates three rings and sets four consecutive stereocenters in a single operation proceeding in a highly efficient manner to give exclusively the trans-decalin framework. In addition, we found that the enol ether geometry and the relative configuration of C3 and C8 are crucial for the success of the polyene cyclization.
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