BROMINATED TRIMETREXATE ANALOGS AS INHIBITORS OF PNEUMOCYSTIS-CARINIIAND TOXOPLASMA-GONDII DIHYDROFOLATE-REDUCTASE

Five previously undescribed trimetrexate analogues with bulky 2'-bromo substitution on the phenyl ring were synthesized in order to assess t he effect of this structure modification on dihydrofolate reductase in hibition. Condensation of o-3,4,5-trimethoxyphenyl)ethyl]-1,1-dicyanop ropene with sulfur in the presence of N,N-diethylamine afforded trimet hoxybenzyl)-4-methylthiophene-3-carbonitrile (15) and imethoxyphenyl)e thyl]thiophene-3-carbonitrile(16). Further reaction with chloroformami dine hydrochloride converted 15 and 16 into -diamino-5-(2'-bromo-3',4' ,5'-trimethoxybenzyl)-4- methylthieno[2,3-d]pyrimidine (8a) and [2-(2' -bromo-3',4',5'-trimethoxyphenyl)ethylthieno [2,3-d]pyrimidine (12) re spectively. Other analogues, obtained by reductive coupling of the app ropriate 2,4-diaminoquinazoline-6 (or 5)-carbonitriles with 2-bromo-3, 4,5-trimethoxyaniline, were o-6-(2'-bromo-3',4',5'-trimethoxyanilinome thyl)-5- chloroquinazoline (9a), mino-5-(2'-bromo-3',4',5'-trimethoxya nilinomethyl) quinazoline (10), and mino-6-(2'-bromo-3',4',5'-trimetho xyanilinomethyl) quinazoline (11). Enzyme inhibition assays revealed t hat space-filling 2'-bromo substitution in this limited series of dicy clic 2,4-diaminopyrimidines with a 3',4',5'-trimethoxyphenyl side chai n and a CH2, CH2CH2, or CH2NH bridge failed to improve species selecti vity against either P. carinii or T. gondii dihydrofolate reductase re lative to rat liver dihydrofolate reductase.