Abstract Based on a computer-assisted analysis of the three-dimensional structure of the binary complex of E. coli dihydrofolate reductase (DHFR) with methotrexate, 5-(N- arylnortropan-3-yl)-and 5-(N-arylpiperidin-4-yl)-2, 4-diaminopyrimidines 2 and 4 were designed as inhibitors of DHFR. Syntheses of the designed compounds have been carried out. The most potent compound 2a inhibited E. coli DHFR with K i= 0.49. 10− 9 M. The ...