A mixture of 10.0 g (29.7 mmol) 4-(3,4-dimethyl-phenyl)-3,3-bis-ethoxycarbonyl-butanoic acid, 10.5 g (32.7 mmol) TBTU, 4.2 g (30.5 mmol) HOBt, 5.8 mL (32.4 mmol) ethyldiisopropylamine, 270 mL THF and 30 mL water was stirred for 15 min at RT and then combined with 7.6 g (32.9 mmol) 3-piperidin-4-yl-3,4-dihydro-1H-quinazolin-2-one. The reaction mixture was stirred for 5 h at RT and evaporated down under reduced pressure. The residue was stirred with 150 mL saturated NaHCO3 solution, suction filtered, washed with water and dried in the circulating air dryer.
