C(N(CC)CC)C.C(O[C@@H:12]1[C@H:18]2[C@H:19]3[C@H:28]([CH2:29][CH2:30][C@:15]2([CH2:16][CH3:17])[C:14](=[O:34])[CH2:13]1)[C@@H:27]1[C:22]([CH:23]=[C:24]([O:31][CH2:32][CH3:33])[CH2:25][CH2:26]1)=[CH:21][CH2:20]3)(=O)C.O>CN(C=O)C>[CH2:32]([O:31][C:24]1[CH2:25][CH2:26][C@H:27]2[C:22](=[CH:21][CH2:20][C@@H:19]3[C@@H:28]2[CH2:29][CH2:30][C@@:15]2([CH2:16][CH3:17])[C@H:18]3[CH:12]=[CH:13][C:14]2=[O:34])[CH:23]=1)[CH3:33]Triethylamine (2 ml, 14.4 mmol) was added to a suspension of 15α-acetoxy-3-ethoxy-18-methyl-estr-3,5-dien-17-one (2 g, 5.4 mmol) in DMF (20 ml). The mixture was stirred at 40° C. for 3 days, cooled to 10° C. and water (15 ml) was then added. The precipitate was filtered and washed with water. The crude product was purified by flash chromatography, eluting with heptane and ethyl acetate (7:3), crystallized from heptane, and dried under vacuum to afford 3-ethoxy-18-methyl-estra-3,5,15-trien-17-one (1.2 g, yield: 66%).
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