To a solution, stirred at 20° C., of 0.28 g (0.97 mmol) of 5-fluoro-1-(3-fluorobenzyl)-1H-indole-2-carboxylic acid prepared in step 1.1, 186 mg (0.97 mmol) of N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDAC) and 131 mg (0.97 mmol) of 1-hydroxybenzotriazole (HOBT) in 15 mL of DMF are added 206 mg (1.17 mmol) of 1-acetyl-5-amino-2,3-dihydro-1H-pyrrolo[2,3-b]pyridine, prepared in step 1.2. The reaction mixture is stirred for 14 hours at 20° C. and then concentrated under reduced pressure. The resulting product is taken up in 100 mL of water. The suspension is then extracted with three times 30 mL of ethyl acetate. The combined organic phases are washed twice with 20 mL of water, dried over sodium sulfate and then concentrated under reduced pressure. The product obtained is purified by chromatography on a column of silica, eluting with a mixture of dichloromethane and methanol. 290 mg of the expected product are thus isolated.
