C[O:2][C:3]1[CH2:21][CH2:20][C@@:19]2(C)[C:5](=[CH:6][CH2:7][C@@H:8]3[C@@H:18]2[CH2:17][CH2:16][C@@:15]2([CH3:23])[C@H:9]3[CH2:10][CH2:11][C@@H:12]2C=C)[CH:4]=1.O.O.C(O)(=O)C(O)=O>CC(C)=O>[CH3:23][C@:15]12[CH2:16][CH2:17][C@H:18]3[C@@H:8]([CH2:7][CH2:6][C:5]4[CH2:4][C:3](=[O:2])[CH2:21][CH2:20][C:19]=43)[C@@H:9]1[CH2:10][CH:11]=[CH:12]2Estra-2,5(10), 16-triene-3-methyl ether (2) (646.3 mg, 2.390 mmole), dissolved in 50 ml of acetone was hydrolyzed for 6 h at room temperature using oxalic acid dihydrate (0.84 g, 6.7 mmole). The reaction mixture was quenched with 25 ml of saturated sodium bicarbonate and then extracted twice with 25 ml portions of ethyl acetate. The combined organic extracts were washed twice with 25 ml of brine, dried over magnesium sulfate, filtered, and concentrated under reduced pressure. The residue was recrystallized from hexane to give product (462.5 mg, 1.804 mmole, 75%), m.p. 112-116 C.
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