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 constructed
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 complete the synthesis.