Concise Total Synthesis of Isospongian Diterpenoid (±)-Polyrhaphin D

The first total synthesis of isospongian diterpenoid (+/-)-polyrhaphin D has been accomplished in 9 steps with 19% overall yield starting from the Wieland-Miescher ketone derivative. The key features of our synthesis include a sequential reduc-tion/Michael addition/aldol condenzation to assemble the A ring and an intramolecular dehydrative cyclization/olefin isomerization reaction to install the gamma-butenolide D ring.