Total syntheses of shizukaols A and E

Shizukaols possess a common heptacyclic framework containing more than ten contiguous stereocenters and potential biological activities. Here we report that the total syntheses of shizukaols A (1) and E (2), two lindenane-type dimers from the Chloranthaceae family, are achieved via a modified biomimetic Diels-Alder reaction. The common crucial biomimetic diene 23 and ethylene species (6, 17) are obtained through either a highly Z-selective olefination of alpha-siloxy ketone with ynolate anions or an intramolecular Horner-Wadsworth-Emmons olefination from commercially available Wieland-Miescher ketone (7). This synthetic approach here opens up practical avenues for the total syntheses of the intriguing Chloranthaceae family members, as well as the understanding of their relevant biological action in nature.