To a solution of 2-({4-[(carboxymethyl)amino]-3-nitrophenyl}carbonyl)benzoic acid (0.26 g, 0.76 mmol) in N,N-dimethyl formamide (5.0 mL), potassium carbonate (0.52 g, 3.80 mmol) was added, followed by the addition of benzyl bromide (0.22 mL, 1.82 mmol). The reaction mixture was stirred for 15 hours at room temperature. It was poured into ice water and diluted with ethyl acetate (50 mL). The organic layer was separated and it was washed with water, 2M aqueous hydrochloric acid and brine. It was dried over anhydrous sodium sulfate. Evaporating the solvent, followed by purification of the crude product by silica gel flash chromatography (hexane:ethyl acetate 4:1 to 3:2 eluent) resulted in phenylmethyl 2-{[3-nitro-4-({2-oxo-2-[(phenylmethyl)oxy]ethyl}amino)phenyl]carbonyl}benzoate (0.33 g, 82% yield) as an amorphous residue. MS (EI) for C30H24N2O7: 524 (MH+).
