A new approach to the synthesis of the 17β-butenolide fragment of cardenolides
摘要:
new, efficient synthesis of the 17 beta-butenolide fragment characteristic of cardenolides is effected by [2 + 2]-cycloaddition of dichloroketene to 3 beta-acetoxypregna-5,20-diene, as a key step. (C) 1999 Elsevier Science Ltd. All rights reserved.
thermal cycloaddition of dichloroketene to steroid olefins, were selectively dehalogenated and further transformed to α-chlorocyclobutanone oximes. In contrast to the Beckmann rearrangement of the α-unsubstituted oximes, α-chlorocyclobutanone oximes, on treatment with thionylchloride in benzene, gave normal and abnormal reaction products. In all reactions studied, the Beckmann fragmentation–substitution