Reaction Steps
1,8-Diazabicyclo[5,4,0]-undec-7-ene (2.6 g, 16.8 mmol) was added to a stirred solution of 3-(4-aminomethyl-1-oxo-1,3-dihydro-isoindol-2-yl)-piperidine-2,6 dione hydrochloride (2.0 g, 6.5 mmol) in DMF (100 mL). After stirring for 10 minutes, 1-hydrocybenztriazole (1.1 g, 7.8 mmol) and N—BOC-β-alanine (1.4 g, 7.1 mmol) were added. The reaction was initiated by addition of 1-[3-(dimethylamino0propyl]-3-ethylcarbodiimide hydrochloride (1.9 g, 9.7 mmol). The mixture was stirred at room temperature overnight. The mixture was concentrated, and the residue was stirred with H2O (40 mL) and CH2Cl2 (120 mL). The solid was collected to give (2-{[2-(2,6-dioxo-piperidin-3-yl)-1-oxo-2,3-dihydro-1H-isoindol-4-ylmethyl]-carbamoyl}-ethyl)-carbamic acid t-butyl ester (2.1 g, 73%) as a white solid: mp 203-205° C.; 1H NMR (DMSO-d6) δ 1.36 (s, 9H, 3CH3), 1.99-2.04 (m, 1H), 2.27-2.64 (m, 2H), 2.85-2.98 (m, 1H), 3.00-3.18 (m, 2H), 4.31 (d, J=5.3 Hz, 2H, CH2), 4.33-4.53 (dd, J=17.3 and 37.3 Hz, 2H, CH2), 5.10-5.17 (dd, J=4.8 and 13.1 Hz, 1H, CH), 6.79 (t, 1H, NH), 7.47-7.52 (m, 2H, Ar), 7.61-7.64 (m, 1H, Ar), 8.43 (t, J=5.3 Hz, 1H, NH), 11.01 (s, 1H, NH); 13C NMR (DMSO-d6) δ 22.54, 28.19, 31.17, 35.60, 36.67, 46.15, 51.55, 77.77, 121.60, 128.24, 130.56, 131.61, 134.56, 140.04, 155.43, 168.02, 170.43, 170.95, 172.80; Anal. calcd. for C22H28N4O6: C, 59.45; H, 6.35; N, 12.60. Found: C, 59.16; H, 6.31; N, 12.50.
