[C:1]([O:4][C@H:5]1[CH2:10][CH2:9][C@H:8]2[C@H:11]3[C@H:21]([CH2:22][CH2:23][C@:6]12[CH3:7])[C@:19]1([CH3:20])[C:14](=[CH:15][C:16](=[O:26])[CH:17](I)[C@@H:18]1[CH3:24])[CH2:13][CH2:12]3)(=[O:3])[CH3:2].C(=O)([O-])[O-].[Li+].[Li+].O>CN(C)C=O>[C:1]([O:4][C@H:5]1[CH2:10][CH2:9][C@H:8]2[C@H:11]3[C@H:21]([CH2:22][CH2:23][C@:6]12[CH3:7])[C@:19]1([CH3:20])[C:14](=[CH:15][C:16](=[O:26])[CH:17]=[C:18]1[CH3:24])[CH2:13][CH2:12]3)(=[O:3])[CH3:2]1.4 g (3 mmol) of 17α-acetoxy-2-iodo-1α-methyl-androst-4-en-3-one of example 11 and 0.443 g (6 mmol) of anhydrous lithium carbonate are stirred in 6 ml of dimethylformamide for 1 hour at 120° C. under nitrogen atmosphere. After cooling, it is added to water and extracted with ethyl acetate. The ethyl acetate solution is dried on sodium sulfate and then concentrated by evaporation. The residue is chromatographed on silica gel with ethyl acetate/hexane as mobile solvent. After concentration by evaporation of the fractions, 0.95 g (92% of theory) of 17β-acetoxy-1-methyl-androsta-1,4-dien-3-one of melting point 173° C. is obtained.
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