Regiospecific syntheses of modified steroid hormones. Part IV. 4-Bromo-oestrone and -17β-oestradiol

Abstract

Dehydrative aromatization of 4-bromo-10β-hydroxyoestr-4-ene-3,17-dione (3a), obtained regiospecifically from 4β,5β-epoxy-10β-hydroxyoestrane-3,17-dione (1) by α-mode oxiran opening to 4-bromo-oestrone (5), was accomplished by treatment with trifluoroacetic anhydride in dioxan at ambient temperature. The stability of the 17β-hydroxy-group to trifluoroacetic anhydride was established, and the synthesis of 4-bromo-17β-oestradiol (6) by the analogous 19-norsteroid route was accomplished.