Acylation of diethyl L-glutamate (I) with 5-bromo-4-methylthiophene-2-carboxylic acid (II) using EDC as the coupling reagent provided amide (III). Subsequent palladium-catalyzed coupling between bromothiophene (III) and ethynyl pyridopyrimidinone (IV) furnished the disubstituted acetylene (V), which was further hydrogenated to (VI) in the presence of Pd/C in trifluoroacetic acid. Finally, basic hydrolysis of the ethyl ester and pivaloyl groups of (VI) led to the title compound.