Using our previously reported convergent synthetic strategy, secondary amine 6 and aldehyde 9 reacted to give tetracyclic esters 10 and 11, which readily led to pentacyclic lactams 14–16. Selective reduction of these products gave (±)-pseudovincadifformine (4), (±)-20-epipseudovincadifformine (5), and (±)-14-epipseudovincadifformine (20). Aldehyde 23 was also prepared and could be directly used for synthesizing (±)-20-epipseudovincadifformine (5). The introduction of the double bond into ring D of the pseudoaspidospermane skeleton was successfully achieved to obtain 21-oxopseudotabersonine (30).
ASJC Scopus subject areas
- Organic Chemistry