Efficient synthesis of six-membered ring D analogues of the pentacyclic alkaloid cephalotaxine by two palladium-catalyzed reactions

D-homo-Cephalotaxine analogues 19 and 23 have been prepared by intramolecul ar Heck reactions of 12 and 22. The substrates 12 and 22 were obtained by a lkylation and acylation, respectively, of the spirocyclic amines 17, which in turn, were generated by intramolecular palladium-catalyzed allylic amina tion.