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

Ethyl secodione (1) has been enantioselectively reduced by using different biocatalysts for the preparation of ethyl secol (13R, 17S)-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). Recombinant ketoreductase KRED1-Pglu and whole cells of yeasts provide the key chiral precursor for the synthesis of a number of hormonal contraceptives (i.e., desogestrel, norgestrel, gestodene) with excellent stereoselectivity.