Total Synthesis of Iejimalide B

Metathesis to the rescue: Although counterintuitive at first sight, application of ring-closing metathesis (RCM) to a cyclization precursor containing 10 double bonds has led to the selective and high-yielding formation of the macrocyclic core of iejimalide B, a potent cytotoxic agent of marine origin. In contrast, a macrolactonization approach failed to afford this intricate target.