Synthesis of Vitisins A and D Enabled by a Persistent Radical Equilibrium.

The first total synthesis of the resveratrol tetramers vitisin A and vitisin D is reported. Electrochemical generation and selective dimerization of persistent radicals is followed by thermal isomerization of the symmetric C8b-C8c dimer to the C3c-C8b isomer, providing rapid entry into the vitisin core. Computational results suggest that this synthetic approach mimics Nature's strategy for constructing these complex molecules. Sequential acid-mediated rearrangements consistent with the proposed biogenesis of these compounds afford vitisin A and vitisin D. The rapid synthesis of these complex molecules will enable further study of their pharmacological potential.