Patent ID: 8383809

Claim:
A process for the preparation of 6β,7β,15β,16β-dimethylen-3-oxo-17α-pregn-4-ene-21,17-carbolactone (I) which comprises the following steps: 1) reacting compound 6 with a compound of formula II: wherein X is halogen and R- is a group selected from the group consisting of: a) —CH 2 —OR I , wherein R I is a hydroxyl-protecting group; and wherein R II and R III , independently from one another, are (C 1 -C 3 )alkyl or R II and R III , together with the oxygen atoms they are attached to, form a 1,3-dioxane or 1,3-dioxolane; to obtain compound 8: 2) oxidating compound 8 with removal of protecting groups R I , R II or R III to obtain drospirenone I: