Novel process for preparation of corticosteroids

A novel process for the preparation of pregnadiene derivatives of formula I, their stereoisomer and intermediate thereof.

• wherein
• R1 and R2 is independently hydrogen or C1-C8 straight, branched alkyl chain, saturated or unsaturated cycloalkyl;
• R3 is hydrogen or
• R5 represents C1-C8 straight, branched alkyl chain or cycloalkyl;
• R4 and R6 is independently hydrogen or halogen;
• comprising the steps of:
• i. epoxidation of compound of formula II to obtain 9,11-oxido derivative of compound of formula III;
• ii. dihydroxylation and optional fluorination of compound of formula III to obtain compound of formula IV with a proviso when R6 is F.
• iii. epoxide ring opening of compound of formula IV followed by acetalisation to obtain compound of formula V and optionally, debromination of compound of formula V with a proviso R4 is Br to obtain compound of formula V when R4 is H
• iv. deacetylation of compound of Formula V to obtain compound of formula I