To a solution of 33 mg of (2R)-2-amino-N-[5-{3-[(2-chloropyridin-4-yl)methyl]-4,4-dimethyl-2,5-dioxoimidazolidin-1-yl}-2-(trifluoromethoxy)phenyl]-2-phenylacetamide obtained in stage d) below in 1 mL of dioxane are successively added, under argon, 7 mg of 3-aminopyridine, 3 mg of (9,9-dimethyl-9H-xanthene-3,6-diyl)bis(diphenylphosphine) (Xantphos), 1.1 mg of palladium acetate and 61 mg of caesium carbonate. The reaction mixture is heated at 110° C. for 1 hour, filtered and washed with twice 10 mL of dioxane, and the filtrate is then concentrated under reduced pressure. The residue is taken up in 1 mL of dioxane, 1 mL of a 4N solution of hydrogen chloride in dioxane is then added and the reaction mixture is stirred at 40° C. for 2 hours. The reaction mixture is then treated with 30 mL of saturated sodium hydrogen carbonate solution and extracted with three times 30 mL of ethyl acetate. The combined organic phases are then washed with water, dried over magnesium sulphate, filtered and concentrated under reduced pressure. The residue is purified by HPLC (gradient: water/acetonitrile containing 0.1% formic acid) to give 12 mg of (2R)-2-amino-N-[5-(4,4-dimethyl-2,5-dioxo-3-{[2-(pyridin-3-ylamino)pyridin-4-yl]methyl}imidazolidin-1-yl)-2-(trifluoromethoxy)phenyl]-2-phenylacetamide, the characteristics of which are as follows:
