Synthesis of Polyamine Alkaloids by the Condensation of a Chiral β-Lactam with a Cyclic Imino Ether. (S)-Dihydroperiphylline and Its Derivatives

The synthesis of 13-membered polyamine alkaloid, (S)-dihydroperiphylline, was achieved by the condensation of a chiral β-lactam, (S)-4-phenyl-2-azetidinone, with a cyclic imino ether of a 9-membered lactam, followed by reductive ring expansion. Both of these reactions proceeded with retention of configuration around the chiral center to give the optical pure 13-membered alkaloids.