Reaction Steps
A mixture of 1-methyl-1H-pyrrole-2-carboxylic acid (0.3 g, 2.6 mmol) and carbonyl diimidazole (0.5 g, 3.0 mmol) in DMF (30 mL) was stirred for 2 hours. Triethylamine (0.8 g, 6.0 mmol) was added, followed by 4-aminomethyl-2-(2,6-dioxo-piperidin-3-yl)-isoindole-1,3-dione hydrochloride (0.7 g, 2.0 mmol). The mixture was stirred at 75° C. (oil bath) overnight. The mixture was cooled to room temperature and concentrated. The residue was stirred with EtOAc (80 mL) and water (30 mL). The EtOAc solution was washed with water (2×40 mL) and brine (40 mL), and dried (MgSO4). Solvent was removed, and the residue was purified by chromatography (SiO2, CH2Cl2: CH3OH 97.5:2.5) to give 1-methyl-1H-pyrrole-2-carboxylic acid [2-(2,6-dioxo-piperidin-3-yl)-1,3-dioxo-2,3-dihydro-1H-isoindol-4-ylmethyl]-amide (0.2 g, 25%) as a white solid: mp>260° C.; 1H NMR (DMSO-d6) δ 2.06-2.10 (m, 1H), 2.50-2.65 (m, 2H), 2.84-2.97 (m, 1H), 3.83 (s, 3H), 4.86 (d, J=5.8 Hz, 2H), 5.13-5.20 (dd, J=5.5 and 12.7 Hz, 1H), 6.04 (t, J=3.4 Hz, 1H), 6.88-6.93 (m, 2H), 7.70-7.86 (m, 3H), 8.63 (t, J=5.8 Hz, 1H), 11.13 (s, 1H); 13C NMR (DMSO-d6) δ 21.98, 30.93, 36.19, 37.47, 48.86, 106.75, 112.63, 121.73, 124.98, 126.95, 128.07, 131.49, 132.96, 134.76, 140.06, 161.56, 166.98, 167.58, 169.82, 172.74; Anal. calcd. for C20H18N4O5+0.18H2O+0.1 ether: C, 60.49; H, 4.82; N, 13.83. Found: C, 60.54; H, 4.74; N, 13.50.
