Total Synthesis of (±)-Dragmacidin E; Problems Solved and Lessons Learned

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

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