title: Selective Pneumocystis carinii dihydrofolate reductase inhibitors: design, synthesis, and biological evaluation of new 2,4-diamino-5-substituted-furo[2,3-d]pyrimidines.
abstract: Nonclassical antifolates, 2,4-diamino-5-substituted-furo[2, 3-d]pyrimidines 3-12 with bridge region variations of C8-S9, C8-N9, and C8-O9 and 1-naphthyl, 2-naphthyl, 2-phenoxyphenyl, 4-phenoxyphenyl, and 2-biphenyl side chains were synthesized as phenyl ring appended analogues of previously reported 2, 4-diamino-5-(anilinomethyl)furo[2,3-d]pyrimidines. The phenyl ring appended analogues were designed to specifically interact with Phe69 of dihydrofolate reductase (DHFR) from Pneumocystis carinii (pc) to afford selective inhibitors of pcDHFR. Additional substituted phenyl side chains which include 2,5-dichloro, 3,4-dichloro, 3,4,5-trichloro, 3-methoxy, and 2,5-dimethoxy analogues 13-17 were also synthesized. The compounds were prepared by nucleophilic displacement of 2,4-diamino-5-(chloromethyl)furo[2,3-d]pyrimidine(2) with the appropriate thiol, amine, or naphthol. Compound 2 was obtained from 2,4-diamino-6-hydroxypyrimidine and 1, 3-dichloroacetone. The compounds were evaluated as inhibitors against DHFR from P. carinii, Toxoplasma gondii, and rat liver. Two analogues, 2,4-diamino-5-[(2'-naphthylthio)methyl]furo[2, 3-d]pyrimidine (5) and 2,4-diamino-5-[(2'-phenylanilino)methyl]furo[2,3-d]pyrimidine (11) showed significant selectivity and potency for pcDHFR compared to trimethoprim. The X-ray crystal structure of 5 with pcDHFR was also carried out, which corroborated the design rationale and indicated a hydrophobic interaction of the naphthalene ring of 5 and Phe69 of pcDHFR which is responsible, in part, for the more than 18-fold selectivity of 5 for pcDHFR as compared with rat liver DHFR.
authors.affiliation: Division of Medicinal Chemistry, Graduate School of Pharmaceutical Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282, USA.
authors.forename: A
authors.initials: A
authors.lastname: Gangjee
authors.forename: X
authors.initials: X
authors.lastname: Guo
authors.forename: S F
authors.initials: SF
authors.lastname: Queener
authors.forename: V
authors.initials: V
authors.lastname: Cody
authors.forename: N
authors.initials: N
authors.lastname: Galitsky
authors.forename: J R
authors.initials: JR
authors.lastname: Luft
authors.forename: W
authors.initials: W
authors.lastname: Pangborn
mesh_terms: D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D015195:Drug Design; D005493:Folic Acid Antagonists / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000201:enzymology; D008958:Models, Molecular; D009243:NAD / Q000378:metabolism; D009281:Naphthalenes / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D010649:Phenylalanine / Q000378:metabolism; D011010:Pneumocystis / Q000187:drug effects* / Q000201:enzymology; D011743:Pyrimidines / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D013329:Structure-Activity Relationship; D013762:Tetrahydrofolate Dehydrogenase / Q000096:biosynthesis* / Q000378:metabolism; D014122:Toxoplasma / Q000187:drug effects / Q000201:enzymology
chemical_list: C111643:2,4-diamino-5-((2-naphthylthio)methyl)furo(2,3-d)pyrimidine; D005493:Folic Acid Antagonists; D009281:Naphthalenes; D011743:Pyrimidines; D009243:NAD; D010649:Phenylalanine; D013762:Tetrahydrofolate Dehydrogenase