Trifluoroacetic acid 4.0 ml (54 mmol) was added to a solution of 2-(3-chloro-benzoylamino)-7,8-dihydro-5H-pyrido[4,3-d]pyrimidine-6-carboxylic acid tert-butyl ester 307 mg (0.789 mmol) in CH2Cl2 (8 ml) under nitrogen as inert gas and stirring was performed for 2 h at RT. After removal of the solvent, the intermediate (3-chloro-N-(5,6,7,8-tetrahydro-pyrido[4,3-d]pyrimidin-2-yl)-benzamide trifluoroacetate) was dissolved in CH2Cl2 (10 ml) and DIPEA 380 μl and 2-methylbenzoic acid 118 mg (0.868 mmol) were added. After cooling the reaction mixture to 0° C., EDCI 166 mg (0.868 mmol) and HOAt 16 mg (0.12 mmol) were added. The reaction mixture was stirred for 1 h at 0° C. and then overnight at RT. After removal of the solvent, purification was performed by means of column chromatography and the product 3-chloro-N-[6-(2-methyl-benzoyl)-5,6,7,8-tetrahydro-pyrido[4,3-d]pyrimidin-2-yl]-benzamide 260 mg (0.64 mmol, 81% of theoretical) was obtained.
