<unk>  is a synthetic pregnane corticosteroid and derivative of cortisol (hydrocortisone) and is also known as 1-dehydro-9α-fluoro-16α-methylhydrocortisone or as 9α-fluoro-11β,17α,21-trihydroxy-16α-methylpregna-1,4-diene-3,20-dione. The molecular and crystal structure of<unk>  has been determined by X-ray crystallography. It is a stereoisomer of betamethasone, the two compounds differing only in the spatial configuration of the methyl group at position 16 (see steroid nomenclature). Synthesis To synthesize<unk> , 16β-methylprednisolone acetate is dehydrated to the 9,11-dehydro derivative. This is then reacted with a source of hypobromite, such as basic N-bromosuccinimide, to form the 9α-bromo-11β-hydrin derivative, which is then ring-closed to an epoxide. A ring-opening reaction with hydrogen fluoride in tetrahydrofuran gives<unk> .<unk>  synthesis
Dexamethasone
Betamethasone
Hydrocortisone
Methandriol
Cortisone
Aminoglutethimide
Anticorticotropin
Mifepristone