New syntheses of 19,21-dihydroxypregn-4-ene-3,20-dione, 21-hydroxy-19-norpregn-4-ene-3,20-dione, and 11β,19,21-trihydroxypregn-4-ene-3,20-dione

Abstract

19,21-Dihydroxypregn-4-ene-3,20-dione has been synthesized from 3β-acetoxypregn-5-en-20-one via the ‘hypoiodite reaction’[treatment of the 5α-bromo-6β-hydroxy derivative with Pb(OAc)₄ and I₂, with irradiation], and Henbest acetoxylation at C-21; oxidation of the intermediate 21-monoacetate to the 19-oxo derivative and alkaline cleavage gave 21-hydroxy-19-norpregn-4-ene-3,20-dione. A similar synthesis of 11β,19,21-trihydroxypreg-4-ene-3,20-dione from 3β-acetoxypregn-5-ene-11,20-dione proceeded through intermediates with the 11β-hydroxy function protected as its acetate. Unusual features mainly of conformational origin were observed in the presence of the 11β-acetoxy substituent; some were helpful to the synthesis, while others led to undesirable side reactions.