The First Regiospecific, Enantiospecific Total Synthesis of 6-Oxoalstophylline and an Improved Total Synthesis of Alstonerine and Alstophylline as Well as the Bisindole Alkaloid Macralstonine

A Wacker sequence has been modified to rapidly generate ring E of (-)-alstonerine, (+)-6-oxoalstophylline, and (-)-alstophylline via a domino process. This one-pot sequence provides facile entry into the dihydropyranyl enone unit of many Alstonia alkaloids. [structure: see text]