Manufacturing Process
METHOD I (Patent U.S. 4,472,393)
A. 21-Chloro-9β,11β-epoxy-17α-hydroxy-16α-methyl-1,4-pregnadiene-3,20-
dione
Prepare a solution of 5.0 g. of 9β,11β-epoxy-17α,21-dihydroxy-16α-methyl-
1,4-pregnadiene-3,20-dione in 20 ml of dry pyridine. Cool on an ice bath; to
the stirred solution under nitrogen, add dropwise 1.1 ml of mesyl chloride.
Remove the ice bath and continue stirring at room temperature for 30 min.
Add 2.0 g of lithium chloride and continue stirring for a further 150 min. Add
to a mixture of 150 ml ethyl acetate and 100 ml distilled water. Wash the
organic phase with dilute 3% aqueous hydrochloric acid, then saturated
aqueous sodium chloride solution and finally saturated sodium bicarbonate
solution. Dry the organic phase over magnesium sulfate, filter and remove the
solvent to give 4.62 g of 21-chloro-9β,11β-epoxy-17α-hydroxy-16α-methyl-
1,4-pregnadiene-3,20-dione.
B. 21-Chloro-9β,11β-epoxy-17α-hydroxy-16α-methyl-1,4-pregnadiene-3,20-
dione 17-(2'-furoate)
Prepare under argon a solution of 8 g of 4-dimethylaminopyridine in 250 ml of
dry methylene chloride. Cool on an ice bath and add to the stirred solution 6.0
ml of 2-furoyl chloride. Remove from the ice bath, allow the temperature to
rise to room temperature and then add 11.5 g of the 21-chloro-9β,11β-epoxy-
17α-hydroxy-16α-methyl-1,4-pregnadiene-3,20-dione. After 24 hours add 500
ml of ethyl acetate saturated with water. Filter off the precipitate and then
evaporate off the solvent to give the crude 21-chloro-9β,11β-epoxy-17α-
hydroxy-16α-methyl-1,4-pregnadiene-3,20-dione 17-(2'-furoate).
C. 9α,21-Dichloro-11β,17α-hydroxy-16α-methyl-1,4-pregnadiene-3,20-dione
17-(2'-furoate)
To the crude 21-chloro-9β,11β-epoxy-17α-hydroxy-16α-methyl-1,4-
pregnadiene-3,20-dione 17-(2'-furoate) add 50 ml of glacial acetic acid, then add a solution of 3.5 g of anhydrous hydrogen chloride in 125 ml of glacial
acetic acid. Stir for 15 minutes and then quench with 500 ml of distilled water.
Filter off the solids, recrystallise from methanol:water, dry for 24 hours under
vacuum to give 12.6 g 9α,21-dichloro-11β,17α-hydroxy-16α-methyl-1,4-
pregnadiene-3,20-dione 17-(2'-furoate) (yield 83% of theory).
Prepare under nitrogen a solution of 1.80 g of 21-chloro-17α-hydroxy-16α-
methyl-1,4,9(11)-pregnatriene-3,20-dione 17-(2'-furoate). Add, with stirring,
a solution of 1.15 ml of 70% perchloric acid in 2.53 ml of distilled water, and
immediately thereafter 604 mg of 1,3-dichloro-5,5-dimethylhydantoin. Stir the
reaction mixture for twenty minutes and then raise the temperature to
ambient temperature. Monitor the consumption of starting material by thin
layer chromatography of aliquots using chloroform:1,3-dichloro-5,5-
dimethylhydantoinyl acetate (9:1) and hexane:ethyl acetate (1:1). When the
starting material is consumed, pour the reaction mixture into 500 ml of
distilled water containing the 1,3-dichloro-5,5-dimethylhydantoin and 7 g of
sodium bisulphite. Add sodium chloride until the solution is saturated. Filter
the precipitated solid, wash and dry at 50°C under vacuum. Purify the
resulting crude product by preparative chromatography on 1000 micron silica
gel plates using chloroform: ethyl acetate (19:1). Elute the desired band with
ethyl acetate, filter the eluate and evaporate at room temperature to give
crude product (1.3 g). Recrystallize the product by dissolving in refluxing
methylene chloride, filtering and then replacing the methylene chloride at
reflux with methanol and then the methanol with distilled water. Cool the
suspension to room temperature, filter and dry under vacuum at 50°C to give
the pure pregna-1,4-diene-3,20-dione, 9,21-dichloro-17-((2-
furanylcarbonyl)oxy)-11-hydroxy-16-methyl-, (11β-,16α)-.
METHOD II
The present invention (Patent U.S. 6,177,560) refers to a new process for the
preparation of mometasone furoate carried out by esterifiication of the 17
hydroxy group of mometasone without prior protection of the 11 hydroxy
group. Mometasone (30 g) was suspended in methylene chloride (300 ml) and
the resulting suspension was cooled to 0-5°C. At this temperature
triethylamine (57 ml) was added. 2-Furoyl chloride (24 ml) was then added
slowly. The mixture was then stirred at 8-12°C until the level of mometasone
present was lower than 0.2% by HPLC. The reaction solution was then cooled
to between -5-5°C and water (120 ml) was added with stirring. After stirring
for 1 hour at 10-15°C the mixture was cooled to between 0-5°C and
concentrated hydrochloric acid was added to adjust the pH of the aqueous
layer between 1 and 2.
The phases were separated and the aqueous layer was extracted with
methylene chloride (60 ml). To the combined organic layers concentrated
hydrochloric acid (90 ml) and acetic acid (30 ml) was added at a temperature
15-25°C. Then the two phase reaction mixture was stirred until less than
0.1% of the side products remained as monitored by HPLC. The reaction
mixture was cooled to 0-5°C and water (120 ml) was added. The lower
organic layer was separated, water (120 ml) and 8 N aqueous sodium
hydroxide solution (about 30 ml) were added to adjust the pH to between 5
and 6. After stirring for 2 hours the organic layer was separated and washed
with water (120 ml). The organic solution [containing the mometasone 17-(2-
furoate)] was concentrated by distillation to a volume of 120 ml. Further methanol (120 ml) was added and the mixture was concentrated to 120 ml.
This procedure was repeated twice more. The reaction mixture was slowly
cooled to 0-5°C and stirred for 2 hours. The crude mometasone 17-(2-
furoate) was then filtered off and washed with cold methanol.
Purification of mometasone 17-(2-furoate)
The wet cake was dissolved in acetone (395 ml) and charcoal (3 g) was
added. After 24 hours, the charcoal was filtered off and washed with acetone
(90 ml). Charcoal (3 g) was added to the solution and the solution stirred for
at least 24 hours at between 15-25°C. The charcoal was then filtered off and
washed with acetone (75 ml). The solution was concentrated by distillation to
a volume of 120 ml. During this concentration the mometasone 17-(2-furoate)
started to crystallise. Methanol (120 ml) was added and the solution was
again concentrated to 120 ml. This procedure was repeated twice. The
suspension was cooled slowly to 0-5°C and stirred for about 2 hours at this
temperature. The pure mometasone 17-(2-furoate) was then filtered off and
washed with cold methanol. The product was dried at 60-70°C. A yield of
29.92 g was obtained.
