1. Concise Total Synthesis of (-)-Mersicarpine
Yusuke Iwama, Kentaro Okano, Kenji Sugimoto,† and Hidetoshi Tokuyama*
Org. Lett. 2012

2. Indole alkaloids isolated from Kopsia species.

3. Isolation and Biological activity
Mersicarpine (1), isolated from the Kopsia species of plants by Kam and co-workers in 2004.

4. Past Synthesis
Organic Letters 2008,10,1437

5. Past Synthesis
Organic Letters 2009,11,2800

6. Past Synthesis
J.A.C.S 2010,132,1236

7. Retrosynthesis Analysis

8. Preparation of Tricyclic Oxime 6

9. DIBAL-H-Mediated Construction of Azepinoindole

10. Reductive Ring-Expansion Rection Followed by Protection of Azepine 11 with Cbz Group

11. One-Pot Procedure of Reductive Ring-Expansion Reaction and Protection with a Cbz Group

12. Reductive ring-expansion V.S Beckmann rearrangement

13. Stepwise Mechanism Proceeding through a Three-Centered Transition State Proposed by the Aid of B3LYP Method

14. Total Synthesis of (-)-Mersicarpine

15. Conclusion
we have achieved a concise total synthesis of (-)-mersicarpine (1) from known keto-ester 9 in a nine step, six-pot process in 30% overall yield.
Key step: The azepinoindole core was constructed by a DIBAL-H-mediated reductive ring-expansion reaction of oxime.

16. Summary