2-Amino-3-hydroxypyridine (I) is alkylated with N-(2-chloroethyl)piperidine (II) under phase transfer conditions to provide ether (III). Subsequent cyclization of aminopyridine (III) with bis-trichlorophenyl malonate (IV) in refluxing acetone leads to the pyridopyrimidine (V). This is finally condensed with the N-(bromomethyl)saccharin derivative (VI) to furnish the title compound.