A CONCISE ROUTE TO TWO DISTINCT E-RING STRUCTURES OF CIGUATOXINS

摘要

Ciguatoxins,the causative toxins of ciguatera seafood poisoning,are large ladder-like polycyclic ethers,and known to have more than 20 structurally distinct congeners.In this paper,we describe a new concise synthesis of the two E-ring structures,of different ring sizes,found in ciguatoxins.From the common oxepane intermediate,the seven-membered E-ring was prepared in three steps,and the eight-membered E-ring was synthesized in seven steps using ring expansion and olefin isomerization as key reactions.