{1-[(5-Chloro-2,4-dimethoxy-phenylcarbamoyl)-methyl]-2,4-dioxo-1,4-dihydro-2H-pyrido[3,4-d]pyrimidin-3-yl}-acetic acid tert-butyl ester → {1-[(5-Chloro-2,4-dimethoxy-phenylcarbamoyl)-methyl]-2,4-dioxo-1,4-dihydro-2H-pyrido[3,4-d]pyrimidin-3-yl}-acetic acid

To a vial containing a solution of {1-[(5-Chloro-2,4-dimethoxy-phenylcarbamoyl)-methyl]-2,4-dioxo-1,4-dihydro-2H-pyrido[3,4-d]pyrimidin-3-yl}-acetic acid tert-butyl ester (Intermediate V) (15 mg, 0.029 mmol) in DCM (1 ml), TFA (1 ml) is added. The mixture is stirred at RT overnight. The reaction mixture is then transferred to a 10 ml round bottomed flask, diluted with a minimal amount of DCM and concentrated in vacuo. This process is repeated once with DCM, twice with EtOAc, and once with MeOH, the solvent being concentrated in vacuo each time, finally giving the title, [M+H]+ 448.93.