1. Divergent Total Syntheses of (-)-Aspidospermine and (+)-Spegazzinine
Org. Lett., 2012, 14,
James P. Lajiness, Wanlong Jiang, and Dale L. Boger*
Speaker : 王湘閔

2. Motivation
Spegazzinine has not yet been prepared by total synthesis, aspidospermine continues to be an attractive synthetic target.
All reported syntheses of aspidospermine proceed through 3, relying on a late-stage Fischer indole originally disclosed by Stork and Dolfini nearly 50 years ago.

3. Isolation and Biological activities
Spegazzinine was first isolated in 1956 from
Aspidosperma chakensis Spegazzini by Djerassi.
Aspidospermine, first isolated from the bark of Aspidosperma quebrancho in the late 1800s.
Biological activities : Diuretic,
vasoconstriction, hypertensive,
and respiratory stimulant properties.

4. Past work

5. Retrosynthesis

6. Synthesis of intermediate 4

7. Synthesis of the skeleton of nature product

8. Synthesis of spegazzinine

9. Synthesis of (-)-aspidospermine, 2

10. Synthesis of C19-epi-aspidospermine

12. Conclusion
The first total synthesis of (+)-spegazzinine and the first reported total synthesis of (-)- aspidospermine that does not rely on a late-stage Fischer indole synthesis.
(+)-spegazzinine : 12 steps, total yield 1.8 %.
(-)-aspidospermine : 14 steps, total yield 5.8 %.
Powerful intramolecular [4 + 2]/[3 + 2] cycloaddition cascade

13. Thanks for your attention