Improvements in corticosteroid 21-acetoxy-17α-hydroxy-16α-methyl-pregna-1,4,9(11)-triene-3,20-dione synthesis and its use as common intermediate in the synthesis of some impurities related to dexamethasone and mometasone.

There are quite substantial number of impurities related to dexamethasone or mometasone which cannot be made from respective Active Pharmaceutical Ingredients but from common intermediate 21-acetoxy-17α-hydroxy-16α-methyl-pregna-1,4,9(11)-triene-3,20-dione (12). As such, a robust and economical synthesis of this key intermediate is important for delivering a resilient and economically viable supply chain for these impurities. Therefore, it is critical to have a robust and economically viable process to synthesize the intermediate 12 in good yield and quality. We report here an improved synthesis of 12 and eight impurities related to dexamethasone and mometasone from this common intermediate.