Synthesis of the Norjatrophane Diterpene (−)-15-Acetyl-3-propionyl- 17-norcharaciol

A scalable enantioselective synthesis of the nonnatural 17-norjatrophane diterpene 3-propionyl-15-acetyl-17-norcharaciol is described. Key C/C-connecting transformations are an Evans aldol reaction, an intramolecular carbonyl ene reaction, a Horner−Wadsworth−Emmons olefination, and a ring-closing metathesis for the formation of a 12-membered carbacycle.