PREPARATION OF FLUMETHASONE AND ITS 17-CARBOXYL ANDROSTEN ANALOGUE

Process for preparing flumethasone (6.alpha.,9.alpha.-difluoro-11(3,17.alpha.,21-trihydroxy-16.alpha.-methyl-pregna-1,4-diene-3,20-dione), flumethasone 21-acetate or its 17-carboxyl androsten analogue of the formula: which process comprises (a) reacting a compound of formula (II) 18 with benzoyl chloride to form a 3-enolic ester of the formula (IIIa): b) reacting the enol benzoate (IIIa) with an electrophilic fluorination agent to introduce fluorine in the C6- position to form a compound of formula (IIIb): 19 (c) deprotecting the compound (IIIb) at C3 to form a compound of formula (IV): (d) fluorinating the 9,11-epoxy group of compound IV by reacting it with hydrofluoric acid to yield flumethasone 21-acetate; and optionally (e) hydrolysing the flumethasone 21-acetate, in the presence or absence of an oxidising agent, to yield compound (I) or flumethasone, respectively. L'invention concerne un procédé destiné à préparer du fluméthasone (6a, 9a-difluoro-11 beta , 17a, 21-trihydroxy-16a-méthyl-pregna-1,4-diène-3,20-dione), du fluméthasone 21-acétate ou son analogue 17-carboxyle androstène. Ce procédé consiste à faire réagir un composé de formule (IIIa) avec un agent de fluoration électrophile.