To a solution of 260 mg (0.81 mmol) of 8-anilino-1-methyl-4,5-dihydro-1H-pyrazolo[4,3-h]quinazoline-3-carboxylic acid in 50 mL of anhydrous dimethylformamide 111 mg of N-hydroxybenzotriazole (0.81 mmol), 0.16 mL of N-methylmorpholine, 205 mg (1.07 mmol) of N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride and 585 mg (2.13 mmol) of triphenylmethylhydroxylamine were added consecutively. After 48 hours at room temperature the solvent was removed under reduced pressure and the residue taken up with dichloromethane and washed with water. The organic layer was then dried over sodium sulfate and evaporated. The crude was treated with 10 mL of a mixture dichloromethane-trifluoroacetic acid and after 4 hours the volatiles were removed in vacuo. The residue was redissolved with dichloromethane and washed with aqueous NaHCO3 and the product purified by chromatography on a silica gel column, eluted with CH2Cl2—CH3COCH3 4/1, to give 180 mg (66% yield) of the title compound.
