Intramolecular [4+1] pyrroline annulation approach to pyrrolizidine alkaloids. Formal total synthesis of (±)-supinidine

Article abstract of DOI:10.1016/S0040-4039(00)89181-9

Dienic azide was found to yield two dehydropyrrolizidines on thermolysis. The synthesis of these compounds is described and the mechanistic implications as well as synthetic utility of this new annulation sequence is discussed.