D-Ring modification of steroids: synthesis of isoxazole annulated steroids from des D-formyl alkyne via 1,3-dipolar cycloaddition reaction

Abstract

The reaction of 17,17-dichloro-androst-16(E)-chloromethylene with secondary amine base afforded substitution products of exocyclic D-ring ketones, in contrast to the reaction of alkaline base which cleaved steroidal D-ring to des-D formyl alkyne. The des-D formyl alkyne was employed to prepare D-ring annulated isoxazolo steroid via 1,3-dipolar nitrile oxide cycloaddition reaction.