Progress toward the Total Synthesis of (±)-Havellockate

Havellockate (1) was isolated from the soft coral Sinularia granosa located on the Havellock island in the Indian Ocean. This highly compact and polyoxygenated marine diterpene bears a cis-fused hydrindane core that contains eight stereogenic centers as well as a spiro-lactone. To the best of our knowledge, no syntheses of 1 have been reported yet. Herein, we describe the synthesis of the all-carbon framework of havellockate (1) in 18 chemical operations. Our approach highlights the efficiency and utility of the hydroxy-directed Diels-Alder (HDDA) reaction to quickly access the cis-fused hydrindane core and securing the correct stereochemistry at C6 and C7. Moreover, six of the eight stereogenic centers have been installed in the correct stereochemistry.