摘要:
The synthesis of the spirocyclic sesquiterpenes (-)-gleenol and (-)-axenol in enantiomerically pure form has been achieved starting from R-(-)-carvone. The key step is the silicon guided acid-promoted rearrangement of a 9-trimethylsilyl-5,6-epoxy-noreudesmane prepared from 3-tiimethylsilyldihydrocarvone in several steps involving Robinson annulation, enone deconjugation and epoxidation. Acid treatment of the epoxy-noreudesmane gave a norspiroaxane as the main product, which was used as intermediate for the synthesis of two naturally occurring sesquiterpenes gleenol and axenol. (c) 2005 Elsevier Ltd. All rights reserved.