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 epoxides SummaryThe synthesis of Diels-Alder compounds of type 2 with a 17-nor-l3(14)-atisbne skeleton is described (cf. Schemes 2-3). 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-y-lactones of (13R*, 14S*)-configuration (e.g. 50) resulting from the opening of the epoxide ring with retention of configuration were obtained.Les adduits de Diels-Alder prkparks h partir du lkvopimarate de mkthyle (1) ou des rksinates de mkthyle avec divers ditnophiles tthylkniques ont la formule gknkrale 2 (squelette et numkrotation de l'atisane). La double liaison de ces adduits est peu rkactive A cause de facteurs stkriques: ainsi, elle n'est pas hydrogknable par les mk- Partie XIII: [l].

Reduction of Diene Adducts ofLaevopimaric Acid

“…The reaction of 1 with NaBH 4 in dioxane has been described by Maciejewski et al [4]. A lactone as product has been reported; however, the structure given indicates that carbonyl group 23 was reduced by the hydride.…”