In order to study the potency of the 5-aminopyrimidine skeleton as an aromatase inhibitor, we synthesized various N, N-disubstituted-5-aminopyrimidine derivatives and evaluated their aromatase-inhibitory activity (in vitro) and their inhibitory activity on pregnant mare serum gonadotropin (PMSG)-induced estrogen synthesis (in vivo). Compounds with the fluoro-substituted benzyl group showed potent aromatase inhibition. Among them, 5-[(4- ...