Beneficial effects of fluorine in the anti-progestin ZK 230211

A novel, highly potent progesterone receptor antagonist, ZK 230211, has been identified. Introduction of a 17α-pentafluoroethyl side chain into the D-ring of the steroidal skeleton resulted in a compound that combines a pure anti-progestagenic endocrinological profile with high potency. Additions of perfluoroalkyl groups to steroidal 17-ketones following modified Prakash and Gassman protocols are described.