A mixture of 3-/N,N-bis(2-chloroethyl)amino/-4-methylbenzoic acid (27.6 g) and trifluoroacetic anhydride (21.0 g) is heated under stirring at 60° C. for 15 min. To the mixture 17α-hydroxypregn-4-ene-3,20-dione (16.5 g) is added and the mixture is heated under stirring at 80° C. for 5 h. Toluene (150 ml) is added, the solution is filtered, and to the filtrate chloroform (200 ml) is added. After washing with H2O and aq. NaHCO3, drying, and evaporation an oil is obtained, to which a mixture of methanol (300 ml) and conc. HCl (3 ml) is added. After 16 h at room temperature the solution is evaporated and the residue chromatographed on a silica gel column using toluene/ethyl acetate (2:1) as eluent. The eluate fraction having Rf =0.40 gives 17α-/3-(N,N-bis(2-chloroethyl)amino)-4-methylbenzoyloxy/pregn-4-ene-3,20-dione (1, 6.8 g, m.p. 170°-1° C.).
