3,3-(Ethylenedioxy)-5β,10β-epoxyestra-9(11)-en-17-one is an intermediate and a byproduct from the synthesis of 4,5-Dihydro-5α-hydroxy-Mifepristone 3-ethylene Ketal (D450130), which is an impurity of Mifepristone (M343975) which is a progesterone receptor antagonist with partial agonist activity.