0.27 ml (1.67 mmol) of diethyl cyanophosphonate is added dropwise at 20° C. under argon to a solution of 0.4 g (1.39 mmol) of 5-fluoro-1-(3-fluorobenzyl)-1H-indole-2-carboxylic acid (obtained in step 1.1) and 0.216 g (1.67 mmol) of 3-amino-6-(methylamino)pyridine (WO2005/028452) in 10 ml of dry dimethylformamide. The mixture is stirred for 10 minutes and then 0.43 ml (3.08 mmol) of triethylamine is added dropwise. The mixture is stirred at ambient temperature for 18 hours and concentrated under reduced pressure, and then the residue is taken up in 50 ml of ethyl acetate. This solution is then successively washed with three times 20 ml of a saturated sodium hydrogencarbonate solution, 50 ml of water and 20 ml of a saturated sodium chloride solution and then dried over sodium sulfate, filtered and concentrated under reduced pressure. The solid obtained is triturated from hot isopropyl ether. 0.471 g of a solid is obtained, which solid is dried under reduced pressure.
