[Cl:1][C@H:2]1[CH2:19][C@@:17]2([CH3:18])[C@@H:13]([CH2:14][CH2:15][C:16]2=[O:20])[C@H:12]2[C@H:3]1[C@@H:4]1[C:9]([CH2:10][C@H:11]2[CH3:21])=[CH:8][C:7](=[O:22])[CH2:6][CH2:5]1.C(O)C.O.[BH4-].[Na+]>O1CCCC1>[Cl:1][C@H:2]1[CH2:19][C@@:17]2([CH3:18])[C@@H:13]([CH2:14][CH2:15][C@@H:16]2[OH:20])[C@H:12]2[C@H:3]1[C@@H:4]1[C:9]([CH2:10][C@H:11]2[CH3:21])=[CH:8][C:7](=[O:22])[CH2:6][CH2:5]1A solution of 380 mg of 11β-chloro-7α-methyl-estr-4-ene-3,17-dione (F′) in 7.6 ml of tetrahydrofuran, 4.4 ml of ethanol and 1.15 ml of water was mixed at −55° C. in portions with 596 mg of sodium borohydride and stirred for 7 hours at −55° C. Then, the mixture was added to ice water, extracted three times with ethyl acetate, washed neutral, dried on sodium sulfate, concentrated by evaporation in a vacuum and chromatographed on silica gel with hexane/ethyl acetate. 130 mg of pure 11β-chloro-17β-hydroxy-7α-methyl-estr-4-en-3-one (I) was obtained ([α]D20=+136.9° (in chloroform), FD183.2° C.).
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