13β-Ethyl-11-methyliden-18.19-dinor-3-ethynyl-pregna-2,4-diene-17-one is an impurity in the synthesis of 13b-Ethyl-11-methyliden-18.19-dinor-3-hydroxy-3-ethynyl-pregna-4-ene-17-one (E933655), which is an impurity of Desogestrel (D296875) a progestogen with low androgenic potency.