An Improved Total Synthesis of (+)-Macroline and Alstonerine as Well as the Formal Total Synthesis of (−)-Talcarpine and (−)-Anhydromacrosalhine−methine

An intramolecular Pd-catalyzed alpha-vinylation process is described. This cyclization has been employed for the enantiospecific total synthesis of gram quantities of both (+)-macroline 3 and the macroline equivalent 4. This sequence is compared to the enolate-driven cross-coupling process. The intermediate 4 was also converted into (-)-alstonerine 1 via modification of an intramolecular Tsuji-Wacker oxidation. This sequence resulted in an improved total synthesis of (-)-talcarpine 5 and (-)-anhydromacrosalhine-methine 6 as well.