Total Synthesis of Luotonin A and Rutaecarpine from an Aldimine via
the Designed Cyclization
ABSTRACT: The total synthesis of rutaecarpine (1) and
luotonin A (2) is described through controlled cyclization of a
common aldimine intermediate 5 derived from ethyl-2-
aminocinnamate and quinazolinone-2-carbaldehyde. The cyanide-mediated
imino-Stetter reaction of aldimine 5 provided
the corresponding indole derivative 3, from which the total
synthesis of rutaecarpine (1) was completed via the formation
of a 6-membered C-ring. On the other hand, microwaveassisted
thermal 6π-electrocyclization of the common intermediate
5, followed by the formation of a 5-membered C′-ring, allowed the completion of the total synthesis of luotonin A (2).