The reaction of 21-chloro-9beta-11beta-epoxy-16beta-methyl-17-(propionyloxy)pregn-4-en-3,20-dione (I) with ethyl orthoformate and p-toluenesulfonic acid in ethanol - dioxane gives 21-chloro-9beta-11beta-epoxy-3-ethoxy-16beta-methyl-17-(propionyloxy)pregna-3,5-dien-20-one (II), which is treated with perchloryl fluoride (ClO3F) in THF - water, yielding 21-chloro-9beta,11beta-epoxy-6alpha-fluoro-16beta-methyl-17-(propionyloxy)pregn-4-ene-3,20-dione (III). The addition of HF to the epoxy ring of (III) by means of the complex urea - HF affords 21-chloro-6alpha,9alpha-difluoro-11beta-hydroxy-16beta-methyl-17-(propionyloxy)pregn-4-ene-3,20-dione (IV), which is finally dehydrogenated with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) in refluxing dioxane.