Enol etherification of 17(alpha)-acetoxy-19-norprogesterone (I) by methyl orthoformate and p-toluene sulfonic acid in dioxan, followed by Vilsmeier's reaction with dimethylformamide and phosphorus oxychloride. After reduction and dehydration with strong acid, the 6-methylene group is isomerized by metallic catalyst to obtain 17(alpha)-acetoxy-19-norpregna-4,6-diene-3,20-dione.