Novel ether-ring transformation via a phenonium ion

Abstract

Upon treatment with CF3COOH at 70°C, trisubstituted-tetrahydropyrans, which were stereoselectively prepared from δ-lactones, were found to be converted into the corresponding 2,5-disubstituted-tetrahydrofurans stereospecifically via a phenonium ion. Furthermore, the stereocontrolled formal synthesis of pamamycin 607 was achieved based on the ether-ring transformation. © 2002 Elsevier Science Ltd. All rights reserved.