To a stirred suspension of [4,6-bis-dimethylamino-2-(4-aminobenzyl)pyrimidin-5-yl]acetic acid methyl ester (100 g, obtained according to step C) in 700 mL of methanol in a 1500 mL double jacketed vessel at 20±5° C. is added diisopropylethylamin (41.4 g) over a period of 30 minutes while heating the reaction mixture to 50±5° C. 4-Trifluoromethylbenzoic acid chloride (63.8 g) is added during further 30 minutes. The reaction mixture is stirred for 15 minutes at 50±5° C. and subsequently heated to 65±5° C. (reflux conditions) and stirred for another 30 minutes. The resulting suspension is gradually cooled to 5±5° C. over a period of 2 hours and stirred at this temperature for 1 hour. The solid is filtered off, washed with 200 mL of isopropanol and dried in vacuo at 50° C. to yield [4,6-bis-dimethylamino-2-[4-(4-trifluoromethylbenzoylamino)benzyl]pyrimidin-5-yl]acetic acid methyl ester in an amount of 135.8 g (yield: 90%; HPLC-purity: 99.5%).
