(9β,11β,16α,17α)-17-(2,2-Dioxido-5H-1,2-oxathiol-4-yl)-9,11-epoxy-17-[(2-furanylcarbonyl)oxy]-16-methyl-androsta-1,4-dien-3-one is an intermediate used in the synthesis of (11β,16α,17α)-9-Chloro-17-(2,2-dioxido-5H-1,2-oxathiol-4-yl)-17-[(2-furanylcarbonyl)oxy]-11-hydroxy-16-methyl-androsta-1,4-dien-3-oneMometasone Furoate Impurity B (C366515), which is an impurity of Mometasone Furoate, a topical corticosteroid used as an anti-inflammatory.