EGIS-9933 was synthesized by S-alkylation of 4,6-diamino-2-mercapto-5-(2-methoxybenzyl)pyrimidine (I) with 1-(2-chloroethyl)-4-[3-(trifluoromethyl)benzyl]piperazine (II) in the presence of potassium carbonate and a catalytic amount of potassium iodide in refluxing methanol. The product was recrystallized from aqueous ethanol, and converted to the hydrochloride.