A Highly Efficient Enzymatic Method for the Sustainable and Stereoselective Production of 5α‐H Key Intermediates for Steroidal Pharmaceuticals

A 5α‐reductase (5αRed‐9) from a Prevotellaceae bacterium was identified to catalyze the quantitative reduction of androstenedione with >99% de and exhibit a broad substrate scope. In the preparative‐scale reaction, 5α‐AD was isolated in 90% yield and 99% purity, with 13.3 gL −1 d −1 space‐time yield. This biocatalytic process overcomes the selectivity limitations of chemical methods, offering an efficient and sustainable strategy for industrial‐scale production.