The invention relates to inhibitors of dihydrofolate reductase and pharmaceutical preparations thereof. The invention further relates to methods of treatment of parasitic infections, such asT. gondii,T. cruzi,P. falciparum,T. brucei, orL. majorinfections, using the novel inhibitors of the invention.本發明係關於二氫葉酸還原酶之抑制劑及其醫藥製劑。本發明進一步關於使用本發明之新穎抑制劑治療寄生感染(諸如弓蟲(T. gondii)、克氏錐蟲(T. cruzi)、惡性瘧原蟲(P. falciparum)、布氏錐蟲(T. brucei)或主要利什曼原蟲(L. major)感染)之方法。