Abstract
(±)-Dragmacidin E was synthesized in 25 steps from commercially available 7-(benzyloxy)indole.
Key transformations in the preparation of this sponge metabolite include (a) a Witkop
cyclization to establish the bridging indole core, (b) cyclo-dehydrative pyrazinone
formation to unite the two indole-bearing components, and (c) late-stage guanidine
installation through chemoselective carbonyl activation.
1 Introduction
2 Results and Discussion
2.1 Model System Synthesis
2.2 (±)-Dragmacidin E Synthesis
3 Conclusions
Key words
total synthesis - alkaloids - marine natural products - Witkop cyclization - pyrazinone