3-Oxo-4-aza-5α-androst-1-ene-17β-carboxylic Acid Chloride is an intermediate used in the synthesis of Dutasteride β-Dimer (D735020), which is a dimer impurity of Dutasteride (D735000); a dual inhibitor of 5α-reductase isoenzymes type 1 and 2. Dutasteride is structurally related to Finasteride (F342000) and is used in the treatment of benign prostatic hyperplasia.