A solution of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) (18 mg, 1.1 eq) in chloroform (1 ml) and a solution of 1-hydroxybenzotriazole (HOBt) (13 mg, 1.1 eq) in tetrahydrofuran (1 ml) are successively added to 4-[(6-{[bis(3-methylbutyl)amino]carbonyl}-1-{3-[(tert-butoxycarbonyl)amino]propyl}-1H-benzimidazol-2-yl)amino]benzoic acid (50 mg, 1 eq) in anhydrous tetrahydrofuran (1 ml). The mixture is stirred for 1 hour at a temperature of approximately 20° C. then the methylamine is added (2M in THF; 0.86 ml, 2 eq). After stirring for 17 hours at a temperature of approximately 20° C., the mixture is diluted with dichloromethane (3 ml) followed by the addition of aminomethylpolystyrene resin (2 eq), TBD-methyl polystyrene resin (2 eq) and methylisothiocyanate-polystyrene resin (4 eq). After stirring for 6 hours at approximately 20° C., the mixture is filtered and the filtrate is concentrated under reduced pressure at 40° C. The residue obtained is dissolved in dichloromethane (3 ml) and washed with a saturated aqueous solution of sodium hydrogen carbonate. The organic phase is dried over sodium sulphate and concentrated at a temperature of approximately 40° C. The residue obtained is dissolved in ethyl acetate (0.5 ml) and a solution of hydrochloric acid (4N in dioxane, 2 ml) is added. After stirring for 1 hour a temperature of approximately 20° C., the precipitate obtained is filtered and dried in order to produce the expected compound (29 mg; 60% yield).
