Unified Approach to ent-Eudesmane-type Terpenoid Synthesis: Total Synthesis of Sinupol and Eutyscoparin A

ent-Eudesmane-type terpenoids constitute a large class of natural products derived from plants, animals, and bacteria. We describe a synthetic approach to two ent-eudesmane-type terpenoids, sinupol, and eutyscoparin A, that relies on a key π-facial- and endo/exo-selective intramolecular Diels–Alder reaction to set the C-5–C-10 stereotriads. Further key transformations of trans-fused decalin include conversion to methyl ketone via a versatile thioester intermediate and appropriate functionalization toward target compounds.