2,4-Diaminothieno[2,3-d]pyrimidine lipophilic antifolates as inhibitors of Pneumocystis carinii and Toxoplasma gondii dihydrofolate reductase

Andre Rosowsky, Andrew T. Papoulis, Sherry F. Queener

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Ten previously unreported 2,4-diaminothieno[2,3-d]pyrimidine lipophilic dihydrofolate reductase inhibitors were synthesized as potential inhibitors of Pneumocystis carinii and Toxoplasma gondii dihydrofolate reductase. Pivaloylation of 2,4-diamino-5-methylthieno[2,3-d]pyrimidine followed by dibromination with N-bromosuccinimide in the presence of benzoyl peroxide gave 2,4-bis(pivaloylamino)-6-bromo-5-(bromomethyl)thieno[2,3-d]pyrimidine, which after condensation with substituted anilines or N-methylanilines and deprotection with base yielded 2,4-diamino-6-bromo-5-[(substituted anilino)methyl]thieno[2,3-d]pyrimidines. Removal of the 6-bromo substituent was accomplished with sodium borohydride and palladium chloride. The reaction yields were generally good to excellent. The products were tested as inhibitors of dihydrofolate reductase (DHFR) from P. carinii, T. gondii, and rat liver. Although the IC50 could not be reached for the 6-unsubstituted compounds because of their extremely poor solubility, three of the five 6- bromo derivatives were soluble enough to allow the IC50 to be determined against all three enzymes. 2,4-Diamino-5-[3,5-dichloro-4-(1- pyrrolo)anilino]methyl]-6-bromothieno[2,3-d]pyrimidine was the most active of the 6-bromo derivatives, with an IC50 of 7.5 μM against P. carinii DHFR, but showed no selectivity for either P. carinii or T. gondii DHFR relative to the enzyme from rat liver.

Original languageEnglish (US)
Pages (from-to)3694-3699
Number of pages6
JournalJournal of Medicinal Chemistry
Issue number22
StatePublished - Nov 11 1997


ASJC Scopus subject areas

  • Molecular Medicine
  • Drug Discovery

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