Concise Synthesis of the Tricyclic Core of Salimabromide.

A concise synthesis of the tricyclic core 2 of the structurally unique marine myxobacterial natural product salimabromide has been developed. Compound 2 contains the tetraline subunit including the two quaternary centers and the eight-membered ring of salimabromide. Major features for its synthesis include a Lewis base catalyzed Denmark-crotylation for stereoselective construction of the highly hindered quaternary stereocenter, an innovative iodine/selectfluor induced endo-carbocylization, and a unique chemoselective carbonylative lactonization of the eight-membered ring.