To a solution of (L) BocNH-Glu-OMe (9.67 g; 37 mmol) in dry DMF (100 mL) was added EDCI (8.65 g; 41.1 mmol), HOBt (6.91 g; 45.14 mmol), and the reaction mixture was stirred at room temperature for 1 h (solution A). In the meantime, to a solution of compound 7 (5.05 g: 37 mmol) in dry DMF (50 mL) kept at 0° C. was added DIEA (23.9 g; 185 mmol) and stirred for 30 min (solution B). Solution B was added to solution A and the reaction mixture was stirred overnight at room temperature. The solvent was removed on the rotary evaporator and the residue was taken up in DCM (400 mL) and washed sequentially with 10% citric acid (100 mL) and brine (100 mL). The organic layer was dried over anhydrous sodium sulfate, filtered, and concentrated, yielding a crude product was purified by flash chromatography (silica gel; hexane/ethyl acetate 70:30) to give 1 as a white solid (8.6 g; 67% yield). 1H NMR (CDCl3) δ 7.8 (s, 1H), 7.4 (s, 1H), 4.6 (m, 1H), 3.7 (s, 3H), 3.3 (t, 1H), 2.2 (m, 2H), 2.1 (m, 2H), 1.9 (m, 2H), 1.7 (m, 2H), 1.4 (s, 9H).
