Acetic Acid → Allopregnan-3alpha-ol-20-one acetate

Participants

Reaction Steps

To a stirred solution of 3β-hydroxy-5α-pregnan-20-one (4.5 g, 318.5 g/m, 14 mmol) in 150 mL of freshly distilled THF, triphenylphosphine (5.58 g, 262.3 g/m, 21 mmol), and acetic acid (1.22 mL) were added. To this stirred reaction mixture at room temperature was added a solution of diisopropylazidodicarboxylate (DIAD) (4.18 mL, 1.027 g/ml, 202.2 g/m, 21 mmol) in 75 mL of tetrahydrofuran dropwise over a period of 10 minutes. After 30 min., the reaction mixture was concentrated under reduced pressure and redissolved in 100 mL of chloroform and extracted twice with water. The chloroform extract was dried over magnesium sulfate and evaporated. The product residue was purified by flash chromatography on silica gel with a mixture of hexane/ethyl acetate (9:1). Fractions corresponding to the title compound were concentrated to give 4.95 g (97.5%) of 3α-acetoxy-5α-pregnan-20-one as a white solid.

Provenance & Evidence