To a solution of (S)-2-(2-amino-4-methoxy-benzoylamino)-hexanoic acid methyl ester (1.0 g, 3.50 mmol) in THF (30 mL) is added trichloromethyl chloroformate (325 mg, 1.64 mmol). The mixture is stirred at 90° C. for 4 hours. The reaction mixture is allowed to cool to room temperature, diluted with EtOAc (100 mL) and washed with H2O (50 mL×3). The organic layer is dried over sodium sulfate and concentrated to give (S)-2-(7-methoxy-2,4-dioxo-1,4-dihydro-2H-quinazolin-3-yl)-hexanoic acid methyl ester (1.1 g, 98%).
