To a solution of N—Ac-Ser-OH (0.2 mmol) in DMF (5 mL) was added HOBt (0.4 mmol) and EDCI (0.22 mmol) and stirred for 5 min. To the solution was added benzyl amine 11 (0.2 mmol) and TEA (0.3 mmol). The reaction mixture was stirred for 2 h at room temperature. The crude products were purified from preparatory HPLC to afford the desired product II-20 as a white solid. 1HNMR (CD3OD) 8.5 (br, 1H), 7.6 (s, 1H), 7.5 (m, 1H), 7.4 (s, 1H), 7.2-7.3 (m, 3H), 7.1 (t, 1H), 6.8-6.9 (m, 2H), 5.0 (t, 1H), 4.2-4.4 (m, 3H), 3.6-3.7 (m, 4H), 1.9 (s, 3H).
