Total syntheses of (-)-fructigenine A and (-)-5-N-acetylardeemin.

The first total synthesis of (-)-fructigenine A and a novel approach to (-)-5-N-acetylardeemin through a common imine intermediate (+)-3 are described. The key steps include highly enantioselective preparation of (+)-3 via domino olefination/isomerization/Claisen rearrangement (OIC) of 5, reductive cyclization (RC), and regioselective oxidation of (-)-4 and a novel assembly of the pyrazino ring of these alkaloids via Ugi three-component reaction/cyclization of (+)-3 with the corresponding amino acid and isonitrile.