Abstract: N-oxides of benyzlpyrimidines of the formula ##STR1## wherein R.sup.1, R.sup.2 and R.sup.3 are as set forth hereinafter, ARE DESCRIBED. The 2,4-diamino-5-(4-bromo-3,5-dimethoxybenzyl)-pyrimidine is also described. The compounds referred to above are useful as potentiators of the antibacterial activity of sulfonamides.

Abstract: Benzylpyrimidines of the formula ##STR1## wherein R.sup.1 and R.sup.2 each, independently, is amino, optionally C.sub.1.sub.-3 -alkyl-substituted pyrrolo, pyrrolidino, piperidino, -NHR.sup.3, -N(R.sup.3).sub.2, -NHR.sup.4, -N(R.sup.3)(R.sup.4),-NR.sup.3 COOR.sup.3, -NHCOOR.sup.3, -NHCONHR.sup.3, -NHCONH.sub.2 or -N(NO)R.sup.3 or wherein R.sup.3 is C.sub.1.sub.-4 -alkyl or C.sub.2.sub.-4 -alkenyl, R.sup.4 is acyl; Z is hydrogen, chlorine, bromine, pyrrolo, pyrrolidino, piperidino or morpholino or R.sup.3, OR.sup.3 or -N(R.sup.3).sub.2 ; A is an oxygen atom bonded to one of the cyclic nitrogen atoms; and n is 0 or 1 are prepared. The benzylpyrimidines are useful as potentiators of the activity of the sulfonamides.

Abstract: N-oxides of benzylpyrimidines of the formula ##STR1## wherein R.sup.1, R.sup.2 and R.sup.3 are as set forth hereinafter, are described. The 2,4-diamino-5-(4-bromo-3,5-dimethoxybenzyl)-pyrimidine is also described. The compounds referred to above are useful as potentiators of the antibacterial activity of sulfonamides.

Abstract: 2,4-Diamino-5-benzylpyrimidines characterized by the formula ##SPC1##Wherein R.sup.1, R.sup.2, A.sup.1, Z and n are as hereinafter set forth, are described. The 2,4-diamino-5-benzylpyrimidines of the invention have useful antibacterial activity. More particularly, they block bacterial dihydrofolate reductase and potentiate the antibacterial activity of sulfonamides.