Trifluoroacetic anhydride → Isopregnanolone

Participants

Reaction Steps

20-Amino-3β-hydroxy-5α-pregnane was first concentrated from dry pyridine. Trifluoroacetic anhydride (3.0 mL) was then carefully added to 3.04 mmol of crude 20-amino-3β-hydroxy-5α-pregnane resuspended in 5.0 mL dry pyridine. After stirring the reaction mixture at room temperature for 3.5 h, the reaction mixture was partitioned between diethyl ether and 1N aqueous HCl, shaken and separated. The organic layer was successively washed with 1N aqueous HCl, water, saturated aqueous sodium bicarbonate, dried over sodium sulfate, filtered, and concentrated under reduced pressure. The residue was refluxed in 15.0 mL methanol for 26 h and then concentrated. The residue was purified by flash chromatography on a 25 mm column using first one column volume of methylene chloride, then one column volume of 5% ethyl acetate in methylene chloride, and then 10% ethyl acetate in methylene chloride as eluants. Isolation and concentration of the product afforded 668 mg (52.9% yield over three steps, from 3β-hydroxy-5α-pregnan-20-one) of product.

Provenance & Evidence