Total Synthesis of (±)-Dragmacidin E

The bis indole sponge alkaloid dragmacidin E was synthesized in racemic form over 25 steps starting from 7-benzhydroxyindole. Key steps include (a) a Witkop cyclization to facilitate construction of the indole-spanning seven-membered ring and (b) a cyclodehydrative pyrazinone synthesis that unites the two indole-containing sectors.