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[摘要]：Aiming at the assembly of marine-derived diterpenoids, the synthesis and cyclization of alpha-geranylated carvones was investigated. 3-Hydroxyalkylation of side-chain hydrogenated carvone with geraniol-derived aldehydes gave access to diterpenoid allyl phosphates. It was shown that retro-aldol fragmentation of ring-hydrogenated 3-hydroxyalkylcarvones is surprisingly facile, because the preferred conformation resembles a Zimmerman-Traxler type transition-state. The hitherto unknown rearranged eunicellane skeleton can be obtained in one step by treatment of an alpha,beta-unsaturated diterpenoid with samarium diiodide generated in situ in THF. NOESY-based structure analysis revealed the presence of an ansa bridge across a twist-boat six-membered ring. |
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