Synthesis of the allylic gonadal steroids, 3α-hydroxy-4-pregnen-20-one and 3α-hydroxy-4-androsten-17-one, and of 3α-hydroxy-5α-pregnan-20-one

Article abstract of DOI:10.1016/0039-128X(85)90064-9

A method for the convenient synthesis of the recently isolated allylic gonadal steroids, 3α-hydroxy-4-pregnen-20-one (3α-dihydroprogesterone; 3α-DHP) and 3α-hydroxy-4-androsten-17-one (3α-HA), was developed using 4-pregnene-3,20-dione (progesterone) and 4-androstene-3,17-dione as substrates and potassium trisiamylborohydride (KS-Selectride) as reducing agent. Similar reactions were also used for the reduction of 5α-pregnane-3,20-dione to 3α-hydroxy-5α-pregnan-20-one (3α-HP). The yields were about 15%, 50%, and >90% for 3α-DHP, 3α-HA and 3α-HP, respectively. Structures of the products, including the 3β-isomers and the 17α-epimer, formed in these reactions were determined by NMR and mass spectroscopic methods.