Condensation of 2,6-diamino-4-hydroxypyrimidine (I) with chloroacetone (II) produced a mixture of pyrrolopyrimidine (III) and furopyrimidine (IV). After treatment of this mixture with pivalic anhydride, the insoluble pivaloyl amide of pyrrolopyrimidine (V) was separated from the soluble dipivaloyl furopyrimidine with boiling EtOAc. Subsequent Mannich reaction of (V) with dimethylamine and formaldehyde afforded the (dimethylamino)methyl derivative (VI). The dimethylamino group of (VI) was then displaced with 4-mercaptopyridine (VII) to give thioether (VIII). Finally, the pivaloyl amide group of (VIII) was hydrolyzed with NaOH to yield the target compound.