Topolyn ,I.S.F.,Italy,1979
To a stirred solution of 9α-fluoro-11β,17,21-trihydroxy-16α-methyl-pregna1,4-diene-3,20-dione (10g, 25.5 mmol) in 20 ml pyridine and 12 ml acetone
at -10°C, a cold solution of methanesulfonyl chloride (3 ml, 38.5 mmol) in 8
ml acetone was added dropwise. The addition was completed within about 3
hours and the mixture was then left standing in the cold for a further 1?
hours after which 200 ml cold water were added. The resulting precipitate was
separated by filtration and washed with water to give 11.5 g (96% of
theoretical yield) of dexamethasone 21-mesylate, melting point 208°C to
210°C (decomposition).
The dexamethasone 21-mesylate (11.5 g, 24.5 mmol) prepared as described
was added in a nitrogen atmosphere to a stirred slurry of potassium octadecacis-9, cis-12-dienoate (7.81 g, 24.5 mmol) in 70 ml DMF. After stirring for 1?
hours at 50°C and evaporating the solvent in vacuo at the same temperature,
the residue was washed by slurrying it into water and was then redissolved in
methylene chloride, dried and the solvent evaporated. The residue was
purified by chromatography on an inactivated (10% water) silica gel column
(470 g) by using an ethyl acetate/hexane mixture (7:3) to give a very good
yield of an oily product.
