Stereoselective Microbial Hydroxylation of Progestin, Norethisterone by Using Aspergillus niger and Penicillium citrinum

Microbial transformation of a potent progestin, norethisterone (17 beta-hydroxy-19-nor-17 alpha-pregn-4-en20-yn-3-one) (1) was carried out by using two filamentous fungi Aspergillus niger and Penicillium citrinum. Biotransformation of 1 with A. niger yielded a hydroxylated transformed product 10 beta,17 beta-diydroxy-19-nor-17 alpha-pregn-4-en-20-yn-3-one (2) whereas 11 beta,17 beta-diydroxy-19-nor-17 alpha-pregn-4-en-20-yn-3-one (3) was obtained through microbial transformation of 1 by P. citrinum. It is the first report of their production from 1 by using A. niger and P. citrinum with complete H-1- and C-13-NMR assignment. The structures of both metabolites were characterized by various spectroscopic techniques and reported data.