Desogestrel EP Impurity A

3-Ethyl-11-methylidene-18,19-dinor-5α,17α-pregn-3-en-20-yn-17-ol (as per EP); 
13-Ethyl-11-methylene-18,19-dinor-5α,17α-pregn-3-en-20-yn-17-ol (as per USP); Desogestrel USP Related Compound A ; Desogestrel Δ3-Isomer