Structural studies on bioactive compounds. 39. Biological consequences of the structural modification of DHFR-inhibitory 2,4-diamino-6-(4-substituted benzylamino-3-nitrophenyl)-6-ethylpyrimidines ('benzoprims').

Benzimidazole-N-oxide modifications of potent lipophilic dihydrofolate reductase (DHFR) inhibitors (e.g., methylbenzoprim 1 and dichlorobenzoprim 2) have been prepared by base-promoted cyclization of the nitrophenylbenzylamino groups to explore the possibility that abrogation of DHFR-inhibitory activity might reveal clues to an alternative anti-ras mechanism. Examples of the new series had only low growth inhibitory activities (GI(50) generally >50 microM) against colon HCT116 and lung HT29 cell lines but, unlike methylbenzoprim, this activity was unaffected by hypoxanthine/thymidine rescue.