Model Studies Directed Towards Microalga Polyether Toxins

✍ Scribed by Eleuterio Alvarez; Maria Teresa Díaz; Dácil Zurita; Miguel Zárraga; Julio D. Martín

• Book ID: 102774385
• Publisher: Wiley (John Wiley & Sons)
• Year: 2010
• Weight: 589 KB
• Volume: 99
• Category: Article
• ISSN: 0037-9646
• DOI: 10.1002/bscb.19900990904

✦ Synopsis

In view of the described results in acid-induced polyepoxide cyclizations, the biosynthesis of fused polyether toxins may be better explained by a stepwise mechanism through oxonium ion intermediates acting on the enzyme-bonded polyepoxide precursor. A new synthetic strategy for the regio-and stereospecific synthesis of heterosubstituted oxolane and oxane rings involving intramolecular iodoetherification of 2,3-epoxy-cycloalken-l-01s was studied.

Cyclization/solvolysis of 2,3-epoxy-cycloalk-5-en-l-ols proceed with complete regio-and stereoselectivity to yield cis-2,6-dialkyl-3,5-oxygenated oxane rings and thus assemble in two steps the key structural units present in marine syn-trans fused polyether toxins. A highly efficient cyclization reaction of 2,3-epoxycyclonon-6-en-l-one leading to the oxepane system is described. The silver(1)-induced solvolysis occurs in high yield under mild conditions and the resulting cyclic system may be manipulated via oxidative carbon-carbon bond cleavage leading to a functionalized a, a'-dialkyl B,p'oxygenated oxepane ring with defined cis-syn-cis stereochemistry.