1-[2-(2-Chloro-benzylamino)-pyrido[4,3-d]pyrimidin-5-yl]-piperidine-4-carboxylic acid 14 (50 mg, 0.13 mmol), 2-piperazin-1-yl-ethanol (17.0 mg, 0.13 mmol) and 4-Methylmorpholine (70 μL, 0.64 mmol) were dissolved in DMF (3 mL). To this mixture hydroxybenzotriazole (17.0 mg, 0.13 mmol) and N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide×HCl (24.0 mg, 0.13 mmol) were added and the mixture was stirred for 48 h at room temperature. Water was added to the mixture and the precipitate formed was filtered off and dried in vacuo. The residue was purified by silica chromatography (ethyl acetate/cyclohexane) to yield in a colorless solid (27.8 mg, 0.05 mmol, 43%) characterized as 15.
