A mixture of 21-hydroxyprogesterone (200 mg, 0.605 mmol), 1,5-dibromopentane (1.65 mL, 12.1 mmol), 40% KOH (300 μL), and tetrabutylammonium hydroxide (60 μL) was stirred for 16 h at room temperature. The reaction mixture was diluted in dichloromethane and washed with water three times. The organic layer was dried over sodium sulfate and concentrated by rotary evaporation. The crude residue was purified by flash chromatography with hexanes/ethyl acetate (2:1) as the eluent to afford 7 as a colorless oil (125 mg, 43%). 1H NMR (500 MHz, CDCl3) δ 5.67 (s, 1H), 3.96 (q, J=17.2 Hz, 2H), 3.41 (t, J=6.4 Hz, 2H), 3.38-3.31 (m, 2H), 2.56 (t, J=9.1 Hz, 1H), 2.40-2.09 (m, 6H), 1.96 (m, 1H), 1.90-1.74 (m, 5H), 1.72-1.16 (m, 14H), 1.12 (s, 3H), 1.05-0.86 (m, 2H), 0.65-0.58 (m, 3H). 13C NMR (125 MHz, CDCl3) δ 207.55, 198.50, 169.94, 122.92, 75.79, 70.34, 61.56, 57.43, 55.12, 52.51, 43.53, 37.54, 34.61, 32.85, 31.74, 31.47, 30.82, 28.69, 27.74, 23.77, 23.47, 21.81, 19.97, 16.34, 12.55. ESI-MS m/z [M+H]+ observed: 481.1, calculated: 481.2.
