Total Synthesis of (+)-Strongylophorines 2 and 9.

The first enantioselective total syntheses of highly complex hexacyclic meroterpenoids STR-2 and -9 (strongylophorine (STR)) are reported. Key elements of the synthetic route include the use of Robinson-type annulation reaction to construct the tricyclic terpenoid building block and a highly efficient PIDA-mediated 1,3-diaxial sp3 C-H activation to incorporate the requisite δ-lactone moiety. This route also enables the determination of absolute configuration of the synthesized natural products.