We report a novel
reductive interrupted Fischer indolization process
for the concise assembly of the 20-oxoaspidospermidine framework.
This rapid complexity generating route paves the way toward various
dihydroindole
Aspidosperma
alkaloids with different
C-5 side chain redox patterns. The end-game redox modulations were
accomplished by modified Wolff–Kishner reaction and photo-Wolff
rearrangement, enabling the total synthesis of (−)-aspidospermidine,
(−)-limaspermidine, and (+)-17-demethoxy-
N
-acetylcylindrocarine and the formal total synthesis of (−)-1-acetylaspidoalbidine.