methyl (8S,9S,10R,11R,13S,14S,17R)-11-((ethylsulfonyl)oxy)-10,13-dimethyl-3,5'-dioxo-1,2,3,4',5',8,9,10,11,12,13,14,15,16-tetradecahydro-3'H-spiro[cyclopenta[a]phenanthrene-17,2'-furan]-7-carboxylate,methyl (8S,9S,10R,11R,13S,14S,17R)-11-((ethylsulfonyl)oxy)-10,13-dimethyl-3,5'-dioxo-1,2,3,4',5',8,9,10,11,12,13,14,15,16-tetradecahydro-3'H-spiro[cyclopenta[a]phenanthrene-17,2'-furan]-7-carboxylate,,Eplerenone Impurity