A series of previously undescribed 2, 4-diamino-5-[2-methoxy-5-alkoxybenzyl] pyrimidines (3a-e) and 2, 4-diamino-5-[2-methoxy-5-(ω-carboxyalkyloxy) benzyl] pyrimidines (3f-k) with up to eight CH2 groups in the alkoxy or ω-carboxyalkyloxy side chain were synthesized and tested for the ability to inhibit partially purified dihydrofolate reductase (DHFR) from Pneumocystis carinii (Pc), Toxoplasma gondii (Tg), Mycobacterium avium (Ma), and rat ...