Asymmetric Total Synthesis of (–)-Crotonine G and (–)-Crotonolide D

The first enantioselective total syntheses of crotonine G and crotonolide D are disclosed. The synthetic approach employs a SmI2 mediated ketyl radical cyclization to form the highly congested quaternary carbon at the center of these complex molecules. Following the furan introduction, the core structure of the natural product is con-structed via oxidative olefin cleavage to install the unusual C-19 and C-20 oxidation. Finally, palladium catalyzed carbonylation, furan oxidation and acid mediated condensation/epimerization completes the synthesis.