title: N9-substituted 2,4-diaminoquinazolines: synthesis and biological evaluation of lipophilic inhibitors of pneumocystis carinii and toxoplasma gondii dihydrofolate reductase.
abstract: N9-substituted 2,4-diaminoquinazolines were synthesized and evaluated as inhibitors of Pneumocystis carinii (pc) and Toxoplasma gondii (tg) dihydrofolate reductase (DHFR). Reduction of commercially available 2,4-diamino-6-nitroquinazoline 14 with Raney nickel afforded 2,4,6-triaminoquinazoline 15. Reductive amination of 15 with the appropriate benzaldehydes or naphthaldehydes, followed by N9-alkylation, afforded the target compounds 5- 13. In the 2,5-dimethoxybenzylamino substituted quinazoline analogues, replacement of the N9-CH 3 group of 4 with the N9-C2H5 group of 8 resulted in a 9- and 8-fold increase in potency against pcDHFR and tgDHFR, respectively. The N9-C2H5 substituted compound 8 was highly potent, with IC50 values of 9.9 and 3.7 nM against pcDHFR and tgDHFR, respectively. N9-propyl and N9-cyclopropyl methyl substitutions did not afford further increases in potency. This study indicates that the N9-ethyl substitution is optimum for inhibitory activity against pcDHFR and tgDHFR for the 2,4-diaminoquinazolines. Selectivity was unaffected by N9 substitution.
authors.affiliation: Division of Medicinal Chemistry, Graduate School of Pharmaceutical Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282, USA. gangjee@duq.edu
authors.forename: Aleem
authors.initials: A
authors.lastname: Gangjee
authors.forename: Ona O
authors.initials: OO
authors.lastname: Adair
authors.forename: Michelle
authors.initials: M
authors.lastname: Pagley
authors.forename: Sherry F
authors.initials: SF
authors.lastname: Queener
mesh_terms: D000818:Animals; D001665:Binding Sites; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D008099:Liver / Q000201:enzymology; D015394:Molecular Structure; D045363:Pneumocystis carinii / Q000201:enzymology*; D011799:Quinazolines / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D051381:Rats; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013762:Tetrahydrofolate Dehydrogenase / Q000187:drug effects*; D014122:Toxoplasma / Q000201:enzymology*
chemical_list: D004791:Enzyme Inhibitors; D011799:Quinazolines; C013474:2,4-diaminoquinazoline; D013762:Tetrahydrofolate Dehydrogenase
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