Novel Variant of the Tricyclooctanone Approach to Cyclopentanoid Natural Products. Synthesis of (±)-Coriolin. Preliminary Communication
✍ Scribed by Martin Demuth; Peter Ritterskamp; Kurt Schaffner
- Publisher
- John Wiley and Sons
- Year
- 1984
- Tongue
- German
- Weight
- 253 KB
- Volume
- 67
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Abstract
A total synthesis of the antitumor sesquiterpene coriolin (9; racemic) in 11 steps from 3,3,6‐trimethylbicyclo[2.2.2]oct‐7‐ene‐2,5‐dione (2a/2b) is described (yield 2a/2b→8: 28%). The sequence is unprecedentedly short and avoids difficult separation problems. The key step in the scheme is a novel facet of oxadi‐π‐methane photochemistry, i.e., the steering by subtle steric effects of the β,γ‐unsaturated ϵ‐diketone to undergo a regioselective photorearrangement involving one β,γ‐enone partial chromophore. Furthermore, the overall phototransformation, which can be carried out at unusually high concentrations (≥20% solutions), involves also a Norrish type I process equilibrating the two epimeric starting enediones 2a and 2b in favour of the desired stereoisomer.