28.3 g of 7α-[11-(dimethyl-tert-butylsilyloxy)-undecyl]-4-estrene-3,17-dione is stirred in 141 ml of tetrahydrofuran with 156 ml of glacial acetic acid and 78 ml of water for 2 hours at 50°. Then the mixture is concentrated to dryness under vacuum. The crude 7α-(11-hydroxyundecyl)-4-estrene-3,17-dione obtained in this way is agitated with 140 ml of pyridine and 70 ml of acetic anhydride for 15 hours at 25°. For working up the mixture, the latter is cooled to 0°, combined diluted with diethyl ether, washed with sodium bicarbonate and sodium chloride solution, dried over sodium sulfate, concentrated to dryness under vacuum, and chromatographed on silica gel with dichloromethane/ethyl acetate, yielding 22.4 g of 7α-(11-acetoxyundecyl)-4-estrene-3,17-dione, [α]D =62.4°, as an oil.
