Preparation and optimization of a series of 3-carboxamido-5-phenacylaminopyrazole bradykinin B1 receptor antagonists

The B1 receptor is an attractive target for the treatment of pain and inflammation. A series of 3-carboxamido5-phenacylamino pyrazole B1 receptor antagonists are described that exhibit good potency against B1 and high selectivity over B2. Initially, N-unsubstituted pyrazoles were studied, but these compounds suffered from extensive glucuronidation in primates. This difficulty could be surmounted by the use of N-substituted pyrazoles. Optimization efforts culminated in compound 41, which has high receptor potency and metabolic stability.