To a stirred solution of 3β-hydroxyandrost-5-en-17-one (0.81 g) in CH2Cl2 (7.4 mL) cooled at 0° C., a solution of mCPBA (0.77 mg) in CH2Cl2 (14 mL) was added dropwise. After 0.5 h at 0° C. and 0.5 h at room temperature, a 10% Na2SO3 aqueous solution was added. The mixture was neutralized by addition of 5% aqueous NaHCO3 solution and extracted with CH2Cl2 (3×100 mL). The combined organic extracts were washed with H2O, dried over Na2SO4, and evaporated to dryness to give 5α,6α-epoxyandrostan-17-one and 5β,6β-epoxyandrostan-17-one as a white foam (1/1 mixture; 1.24 g, 97%). 1H-NMR (300 MHz, acetone-d6, ppm from TMS): 3β-hydroxy-5α,6α-epoxyandrostan-17-one δ 3.26 (1H, d), 2.96 (1H, d), 2.70-1.12 (18H, m), 1.36 (3H, s), 0.83 (3H, s); 3β-hydroxy-5α,6β-epoxyandrostan-17-one: δ 2.98 (1H, d), 2.93 (1H, d), 2.71-1.13 (18H, m), 1.06 (3H, s), 0.84 (3H, s).
