Enantioselective total synthesis of dysidavarone A, a novel sesquiterpenoid quinone from the marine sponge Dysidea avara.

Dysidavarone A, a structurally unprecedented sesquiterpenoid quinone, was synthesized in 30 % overall yield in a longest liner sequence of 13 steps from commercially available o-vanillin. A highly strained and bridged eight-membered carbocyclic core was established by the C7-C21 carbon bond formation through a copper enolate mediated Michael addition to the internal quinone ring.