Construction of the 5,10b-Phenanthridine Skeleton Using [3+2]-Cycloaddition of a Non-Stabilized Azomethine Ylide: Total Synthesis of (±)-Maritidine and (±)-Crinine Alkaloids
✍ Scribed by Ganesh Pandey; Nishant R. Gupta; Smita R. Gadre
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 902 KB
- Volume
- 2011
- Category
- Article
- ISSN
- 1434-193X
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✦ Synopsis
Abstract
Vicinal quaternary and tertiary stereocenters of the 5,10b‐phenanthridine skeleton 1 are constructed simultaneously in one step by the [3+2]‐cycloaddition of non‐stabilized azomethine ylide 9, generated by sequential double desilylation of 10 utilizing silver(I) fluoride as a one‐electron oxidant. The regio‐ as well as stereochemical origin of this cycloaddition reaction is explained through a favorable transition state 9″. The strategy is successfully applied for the total synthesis of the biologically active alkaloids (±)‐maritidine (1a), (±)‐crinine (1b), and their analogues (1d, 1e, and 1f).