Total Synthesis of the Prenylated Indole Alkaloid (±)-Notoamide N via an Electrochemically Mediated Vilsmeier–Haack Formylation of a Chlorinated Indole

Abstract A total synthesis of the racemic modification of the prenylated indole alkaloid notoamide N has been realised. A crucial step involved the electrochemically mediated Vilsmeier–Haack formylation of a chlorinated 1,7-dihydropyrano[2,3-g]indole. The product aldehyde was engaged in biomimetic and tandem aldol condensation/intramolecular Diels–Alder reactions with a diketopiperazine derivative to give a diazabicyclo[2.2.2]octane-containing adduct. Epoxidation of this adduct led, via an in situ semi-pinacolic rearrangement of the initially formed oxirane, to the targeted spiro-oxindole notoamide N.