Stereoselective Enzymatic Reduction of Ethyl Secodione: Preparation of a Key Intermediate for the Total Synthesis of Steroids

Abstract Ethyl secodione ( 1 ) has been enantioselectively reduced by using different biocatalysts for the preparation of ethyl secol (13 R , 17 S )‐ 2a . The recombinant ketoreductase KRED1‐Pglu converted the substrate with the highest reaction rate and stereoselectivity ( ee > 98 %), whereas whole cells of Pichia minuta CBS 1708 showed the highest productivity. Stereoselective reduction of 1 provides the key chiral precursor for the synthesis of a number of hormonal contraceptives (i.e., desogestrel, norgestrel, gestodene).