Acyl migration in the Reformatsky reaction of 21-acyloxy-5-pregnen-20-one derivatives with ethyl bromoacetate.

Reformatsky reaction of 3beta, 21-diacyloxy-and 3beta-methoxy-21-acyloxy-5-pregnen-20-one with ethyl bromoacetate yields, through an intramolecular 1,2-acyl migration, 38, 20 XI-acyloxy-14alpha-card-5-enolides were converted into the respective 20 XI-hydroxy-14alpha-card-5-enolides and the 14 alpha-carda-5,20(22)-dienolides. Experimental support to the proposed intramolecular 1,2-acyl migration is provided by the use of labelled compounds.