[CH3:1][Li].[CH3:3][C@:4]12[CH2:20][CH2:19][C:18]3[C@@H:9]([CH2:10][CH2:11][C:12]4[C:17]=3[CH2:16][CH2:15][C:14](=[O:21])[CH:13]=4)[C@@H:8]1[CH:7]=[CH:6][C:5]2=[O:22]>C(OCC)C.O1CCCC1.N.[Cu]I.[Cu](I)I>[CH3:1][C@H:7]1[C@H:8]2[C@H:9]3[C:18]([CH2:19][CH2:20][C@:4]2([CH3:3])[C:5](=[O:22])[CH2:6]1)=[C:17]1[C:12](=[CH:13][C:14](=[O:21])[CH2:15][CH2:16]1)[CH2:11][CH2:10]35.2 ml of a 5% solution of methyllithium in diethyl ether are mixed with 570 mg of copper(I) iodide by portions at -5° C. Stirring is performed at a temperature between -5° and 0° C. until the copper iodide is fully dissolved. Then it is cooled to -20° C. and a solution of 1.1 g of 4,9,15-estratriene-3,17-dione in 15 ml of absolute tetrahydrofuran is slowly added drop by drop. It is stirred for 20 minutes at -20° C., then poured in concentrated aqueous ammonia solution and extracted with ethyl acetate. After chromatography with silica gel with hexane/ethyl acetate and crystallization of the main fraction from ethyl acetate/diisopropyl ether, 720 mg of 15β-methyl-4,9-estradiene-3,17-dione with a melting point of 125° to 126° C. are obtained.
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