An efficient two stage synthesis of the steroid anti-inflammatory agent mometasone 17- furoate (Sch 32088) 4 from 17α, 21-dihydroxy-16α-methyl-9β, 11β-oxidopregna-1, 4-diene- 3, 20-dione 6 is described and the structures of unusual δ-hydroxy-γ-sultone byproducts of 4- dimethylamino-pyridine catalyzed methanesulfonylation of 21-hydroxy-20-ketosteroids are deduced.
