A solution of tert-butyl 4-(1-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl)-2-(3-methoxy-4-(4-methyl-1H-imidazol-1-yl)phenylamino)-7,8-dihydropyrido[4,3-d]pyrimidine-6(5H)-carboxylate (397 mg, 0.71 mmol) and TFA (0.547 mL, 7.10 mmol) in DCM was stirred for one hour at 40° C. The reaction mixture was cooled and sat aqu NaHCO3 was added until the mixture was neutralized. The organic phase was separated and the water phase was washed repeatedly with DCM yielding 4-(1-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl)-N-(3-methoxy-4-(4-methyl-1H-imidazol-1-yl)phenyl)-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidin-2-amine (250 mg, 77%)
