The synthesis of ZK-91587 has been described: The reaction of 15beta,16beta-methylene-3-oxo-17alpha-pregna-4,6-diene-21,17-carbonolactone (I) with diethylaluminum cyanide in THF or with KCN and NH4Cl in DMF - water gives 7alpha-cyano-15beta,16beta-methylene-3-oxo-17alpha-pregn-21,17-carbonolactone (II), which by partial reduction with diisobutylaluminum hydride in toluene is converted into the corresponding aldehyde (III). The oxidation of (III) with Jones' reagent (CrO3) affords the carboxylic acid (IV), which is finally methylated with diazomethane in dichloromethane.