Intramolecular radical cyclization - Ring-closing metathesis approach to fused polycyclic ethers. Convergent synthesis and conformational analysis of the (E)FGH ring system of ciguatoxin

Makoto Sasaki, Tetsuji Noguchi, Kazuo Tachibana

Research output: Contribution to journalArticlepeer-review

55 Citations (Scopus)

Abstract

A convergent synthetic route to the (E)FGH ring system 4 of ciguatoxins, the causative toxins for ciguatera fish poisoning, has been developed. The synthesis features convergent coupling to form dioxane acetal, regioselective acetal cleavage by diethylaluminum phenylthiolate or diisobutylaluminum phenylselenolate followed by intramolecular radical cyclization to construct the oxepane ring G, and a ring-closing metathesis reaction to form the hexahydrooxonine ring F. The hexahydrooxonine ring F of tetracyclic model system 4 existed as a 5:1 equilibrium mixture of two conformers (UP and DOWN conformers), with the UP one predominating. This is the first illustration that reproduces the preference for the UP conformer over the DOWN one, which preference was observed for natural ciguatoxins.

Original languageEnglish
Pages (from-to)3301-3310
Number of pages10
JournalJournal of Organic Chemistry
Volume67
Issue number10
DOIs
Publication statusPublished - 2002 May 17

ASJC Scopus subject areas

  • Organic Chemistry

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