6-Aryl-1,4-dihydro-benzo[d][1,3]oxazin- 2-ones:  A Novel Class of Potent, Selective, and Orally Active Nonsteroidal Progesterone Receptor Antagonists

Novel 6-aryl-1,4-dihydro-benzo[d][1,3]oxazin-2-ones were synthesized and tested as progesterone receptor (PR) antagonists. These compounds were potent and showed good selectivity for PR over other steroid receptors such as the glucocorticoid and androgen receptors (e.g., greater than 80-fold selectivity at PR for 4h). Numerous 6-aryl benzoxazinones (e.g., 4h−j) were active orally in the uterine decidualization and component C3 assays in the rats. In these in vivo models, 4h had potencies comparable to mifepristone (1).