Etudes stéréochimiques XIV. Adduits de Diels‐Alder en série résiniques; action des peracides et ouvertures acido‐catalysées d'époxydes

Abstract

Studies in Stereochemistry XIV. Diels‐Alder adducts in the resin series; action of peracids and acid‐catalysed ring opening of epoxidesThe synthesis of Diels‐Alder compounds of type 2 with a 17‐nor‐13(14)‐atisène skeleton is described (cf. Schemes 1–3). Depending on the nature and configuration of substituents R1 and R2 on the carbon atoms 15 and 16, an epoxide (24–33) or a ketone (35–38) or a mixture of epoxide, ketone and lactone is obtained by the action of p‐nitroperbenzoic acid on the double bond of these adducts (cf. Scheme 4). A simplified reaction scheme is suggested to explain the formation of the various products. In an acid‐catalysed reaction, the epoxides isomerize mainly into ketones. Nevertherless, in some cases, dienes (e.g. 52) or hydroxy‐γ‐lactones of (13R*, 14S*)‐configuration (e.g. 50) resulting from the opening of the epoxide ring with retention of configuration were obtained.