Elaboration of Sterically Hindered δ-Lactones through Ring-Closing Metathesis: Application to the Synthesis of the C1–C27 Fragment of Hemicalide

The synthesis of the C1–C27 fragment of hemicalide, a marine metabolite displaying a unique potent antiproliferative activity, has been accomplished. The synthetic approach highlights a remarkably efficient ring-closing metathesis reaction catalyzed by Nolan ruthenium indenylidene complexes to elaborate the highly substituted δ-lactone framework.