Synthesis of Vinca Alkaloids and Related Compounds. 64. Total Syntheses of (+/-)-Pseudovincadifformine and (+/-)-20-Epipseudovincadifformine

Article abstract of DOI:10.1021/jo00074a039

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 obtained 21-oxopseudotabersonine (30).