Synthesis of Fused Tricyclic Amines from Enolizable Acyclic Aldehydes by Cyclization then Dipolar Cycloaddition Cascade: Synthesis of Myrioxazine A

A tandem one-pot reaction involving a condensation, then cyclization (N-alkylation), followed by an azomethine ylide or nitrone dipolar cycloaddition allows a synthesis of tricyclic amines from acyclic enolizable aldehydes. The reaction was unsuccessful using amino acids or esters but was successful with (tributylstannyl)methylamine or hydroxylamine. One of the products was converted in two steps to the alkaloid (+/-)-myrioxazine A. The chemistry also provides a formal synthesis of the antimalarial alkaloids myrionidine and schoberine.