title: Structural studies on bioactive compounds. 28. Selective activity of triazenyl-substituted pyrimethamine derivatives against Pneumocystis carinii dihydrofolate reductase.
abstract: Triazenyl-substituted pyrimethamine derivatives 10a-s have been prepared by coupling diazotized 2,4-diamino-5-(3-amino-4-chlorophenyl)-6-ethyl pyrimidine (1c) with a series of secondary amines in aqueous sodium carbonate solution. The triazenes which are stable and poorly soluble as free bases form more soluble, but unstable, salts with alkanesulfonic acids. The lead dimethyltriazene 2,4-diamino-5[4-chloro-3-(3,3-dimethyltriazen-1-yl)phenyl]-6-et hylpyrimidine (4a) forms a crystalline ethanesulfonic acid salt (solvated with 2-propanol), which is protonated at the pyrimidine N-1 position, as determined by X-ray crystallography. The ability of these new triazenes to inhibit Pneumocystis carinii dihydrofolate reductase in vitro has been compared to that of triazene 4a. The most potent and selective compound, 2,4-diamino-5-[3-[3-[2-(acetyloxy)ethyl]-3-benzyltriazen-1-y l]-4- chlorophenyl]-6-ethylpyrimidine (14a), has an IC50 value of 0.17 microM against the microbial enzyme and potentially useful selectivity (rat liver IC50/P. carinii IC50 = 114).
authors.affiliation: Department of Pharmaceutical Sciences, University of Nottingham, U.K.
authors.forename: M F
authors.initials: MF
authors.lastname: Stevens
authors.forename: K S
authors.initials: KS
authors.lastname: Phillip
authors.forename: D L
authors.initials: DL
authors.lastname: Rathbone
authors.forename: D M
authors.initials: DM
authors.lastname: O'Shea
authors.forename: S F
authors.initials: SF
authors.lastname: Queener
authors.forename: C H
authors.initials: CH
authors.lastname: Schwalbe
authors.forename: P A
authors.initials: PA
authors.lastname: Lambert
mesh_terms: D000818:Animals; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003460:Crystallization; D018360:Crystallography, X-Ray; D005493:Folic Acid Antagonists / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D008099:Liver / Q000201:enzymology; D008958:Models, Molecular; D015394:Molecular Structure; D011010:Pneumocystis / Q000201:enzymology*; D011743:Pyrimidines / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D051381:Rats; D012995:Solubility; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism*; D014226:Triazenes / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology
chemical_list: C106596:2,4-diamino-5-(3-(3-(2-(acetyloxy)ethyl)-3-benzyltriazen-1-yl)-4-chlorophenyl)-6-ethylpyrimidine; D005493:Folic Acid Antagonists; D011743:Pyrimidines; D014226:Triazenes; D013762:Tetrahydrofolate Dehydrogenase