Concise stereoselective synthesis of marine sesterterpene, 16-deacetoxy-12-epi-scalarafuran acetate and its 14-epimer via intramolecular Diels-Alder addition

The stereoselective synthesis of C12 oxygenated marine scalaranic sesterterpene 16-deacetoxy-12-epi-scalarafuran acetate and its 14-epimer were described. A highly stereoselective intramolecular Diels-Alder addition was designed as the key step to construct the ring D, and the absolute configurations of natural 16-deacetoxy-12-epi-scalarafuran acetate was supported by the X-ray diffraction analysis of single crystal of corresponding 16-deacetoxy-12-epi-scalarafuran.