397864-40-3

(6α,11β,16α,17α)-6,9-Difluoro-17-[(2-furanylcarbonyl)oxy]-11-hydroxy-16-methyl-3-oxoandrosta-1,4-diene-17-carbothioic Acid is a steroid used in the preparation of crystalline forms of the therapeutically useful anti-inflammatory corticosteroid fluticasone furoate (I) and its solvates. A fluticasone furoate (F599510) impurity.

A suspension of 17β-[(N, N-dimethylcarbamoyl)thio]carbonyl-6α,9α-difluoro-17α-[(2-furanylcarbonyl)oxy]-11β-hydroxy-16α-methyl-3-oxoandrosta-1,4-diene (14.2 g, 0.024 mol) and potassium carbonate (6.78 g, 0.0491 mol) in methanol (70 ml) was stirred at ambient temperature for 6 hrs under a blanket of nitrogen. After that, water was added to the reaction mixture, and the clear solution was washed with toluene. The aqueous layer containing the product was charcoalized and then acidified with 2N HCl until pH was 1.5 to 2.0. The precipitated product was filtered, washed with water, and dried to yield 6α,9α-difluoro-17α-(furan-2-yl)carbonyloxy-11β-hydroxy-16α-methyl-3-oxoandrosta-1,4-diene-17β-carbothioic acid as a white solid (11.8 g, 94.8%).