Potent nonsteroidal progesterone receptor agonists: Synthesis and SAR study of 6-aryl benzoxazines

Abstract

Novel 6-aryl benzoxazines were prepared and examined as progesterone receptor (PR) modulators. In contrast to the structurally related 6-aryl dihydroquinoline PR antagonists, the 6-aryl benzoxazines were potent PR agonists. Compounds 4e, 5b, and 6a with the 2,4,4-trimethyl-1,4-dihydro-2 H-benzo[ d][1,3]oxazine core were the most potent PR agonists in the series with sub-nanomolar activities (EC 50 0.20–0.35 nM). Compound 6a was more potent than progesterone ( P4) in the in vivo decidualization assay in an ovariectomized female rat model by subcutaneous administration with an ED 50 of 1.5 mg/kg (vs 5.62 mg/kg for P4).