Anti-Pneumocystis carinii pneumonia activity of dicationic 2,4-diarylpyrimidines

A synthesis of 2,4-bis-(4-amidinophenyl)pyrimidine 6, 2,4-bis-[(4-imidazolin-2-yl)phenyl)]pyrimidine 7, 2,4-bis [(4-tetrahydropyrimidinyl-2-yl)phenyl]pyrimidine 8, 2,4-bis[(4-N-n-propylamidino)phenyl]pyrimidine 9, 2,4-bis[(4-N-isopropylamidino)-phenyl]pyrimidine 10 and 2,4-bis[(4-N-isobutylamidino)phenyl]pyrimidine 11 starting from 4-bromobenzamidine and 4-bromoaceto-phenone is reported. A synthesis of 2-(4-amidinopnenyl)-4-(2-methoxy-4-amidinophenyl)pyrimidine 20, 2-[4-(imidazolin2-yl)-phenyl]-4-[2-me thoxy-4-(imidazolin-2-yl)phenyl]pyrimidine 21, and 2-[4-(N-iso-propylamidino)phenyl]-4-[2-methoxy-4-(N-isopro-pylamidino)phenyl]pyrimidine 22 beginning with 4-bromobenzamidine and 2-methoxy-4-bromoacetophenone is described. Compounds 6-11 and 20-22 all bind strongly to DNA. Compounds 6, 9-11, and 20 given at 5 mg/kg are more active and less toxic than pentamidine at its effective dose when evaluated against Pneumocystis carinii pneumonia (PCP) in the immunosuppressed rat model. Several compounds in this series are being evaluated further as potential new anti-PCP agents.