Formal Syntheses of (±)-Stemonamine and (±)-Cephalotaxine

A short and efficient approach to aza-quaternary pyrrolo[1,2-a]azepine 8 and aza-quaternary indolizine 23, as the crucial intermediates for syntheses of stemonamine (1a) and cephalotaxine (1b), has been developed on the basis of the key intramolecular Schmidt reaction of symmetric azidodiones 5 and 18, respectively.