Synthesis of Finasteride, 5α-Reductase Inhibitors

The document described the synthesis process of Finasteride, a 5α-reductase inhibitor, from Zaixitongsuan. The process involved several chemical reactions, including amidation, oxidation, cyclization, hydrogenation, and dehydrogenation. Improvements were made to the hydrogenation reactions and the isolation conditions of hydrogenated compounds, successfully controlling the impurity level of the 5 β-isomer to below 2%. The final product met the requirements for pharmaceutical use and was deemed suitable for industrial production.