2,4-DIAMINOTHIENO[2,3-D]PYRIMIDINE ANALOGS OF TRIMETREXATE AND PIRITREXIM AS POTENTIAL INHIBITORS OF PNEUMOCYSTIS-CARINII AND TOXOPLASMA-GONDII DIHYDROFOLATE-REDUCTASE

A series of eight previously undescribed 2,4-diaminothieno[2,3-d]pyrim idine analogues of the potent dihydrofolate reductase (DHFR) inhibitor s trimetrexate (TMQ) and piritrexim (PTX) were synthesized as potentia l drugs against Pneumocystis carinii and Toxoplasma gondii, which are major causes of severe opportunistic infections in AIDS patients. -5-m ethyl-6-(aryl/aralkyl)thieno[2,3-d]pyrimidines with 3,4,5-trimethoxy o r 2,5-dimethoxy substitution in the aryl/aralkyl moiety and 4-diamino- 5-(aryl/aralkyl)thieno[2,3-d]pyrimidines with 2,5-dimethoxy substituti on in the aryl/aralkyl moiety were obtained by reaction of the corresp onding 2-amino-3-cyanothiophenes with chloroformamidine hydrochloride. The aryl group in the 5,6-disubstituted analogues was either attached directly to the hetero ring or was separated from it by one or two ca rbons, whereas the aryl group in the 5-monosubstituted analogues was s eparated from the hetero ring by two or three carbons. 2-Amino-3-cyano -5-methyl-6-(aryl/alkyl)thiophene intermediates for the preparation of the 5,6-disubstituted analogues were prepared from omega-aryl-2-alkyl idene-malononitriles and sulfur in the presence of a secondary amine, and 2-amino-3-cyano-4-(aryl/aralkyl)thiophene intermediates for the pr eparation of the 5-monosubstituted analogues were obtained from omega- aryl-1-chloro-2-alkylidenemalononitriles and sodium hydrosulfide. Synt hetic routes to the heretofore unknown ylidenemalononitriles, and the ketone precursors thereof, were developed. The final products were tes ted in vitro as inhibitors of DHFR from Pneumocystis carinii, Toxoplas ma gondii, rat liver, beef liver, and Lactobacillus casei. A selected number of previously known 2,4-diaminothieno[2,3-d]pyrimidines lacking the 3,4,5-trimethoxyphenyl and 2,5-dimethoxyphenyl substitution patte rn of TMQ and PTX, respectively, were also tested for comparison. None of the compounds was as potent as TMQ or PTX, and while some of them showed some selectivity in their binding to Pneumocystis cariniii and Toxoplasma gondii versus rat liver DHFR, this effect was not deemed la rge enough to warrant further preclinical evaluation.