Reaction Steps
To a stirred suspension of 4-aminomethyl-2-(2,6-dioxo-piperidin-3-yl)-isoindole-1,3-dione hydrochloride (1.8 g, 5.7 mmol) in DMF (20 ml), was added 1,8-diazabicyclo[5.4.0]undec-7-ene (0.9 g, 6.8 mmol). After stirring for 10 minutes, 1-hydroxybenzenetriazole (0.9 g, 6.8 mmol) and benzo[c]isoxazole-3-carboxylic acid (1.0 g, 6.3 mmol) were added, followed by 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (1.6 g, 8.5 mmol). The mixture was stirred at room temperature overnight and was concentrated in vacuo. The residue was dissolved in CH2Cl2 (50 mL), washed with water (2×30 mL) and brine (30 mL), and dried over MgSO4. Solvent was removed in vacuo, and the resulting oil was purified by ISCO silica gel flash chromatography (eluent: 3% MeOH in CH2Cl2) to afford benzo[c]isoxazole-3-carboxylic acid [2-(2,6-dioxo-piperidin-3-yl)-1,3-dioxo-2,3-dihydro-1H-isoindol-4-ylmethyl]-amide as a yellow solid (1.93 g, 78%): mp, 253-255° C.; HPLC: Waters Symmetry C-18, 3.9×150 mm, 5 micro, 1 mL/min, 240 nm, gradient from 10/90 (CH3CN/H2O) to 95/5(CH3CN/H2O) in 10 minutes: tR=6.6 min (96%); 1H NMR (DMSO-d6): δ 2.08-2.13 (m, 1H), 2.53-2.65 (m, 2H), 2.86-2.94 (m, 1H), 5.02 (d, J=6.0 Hz, 2H), 5.19 (dd, J=6, 12 Hz, 1H), 7.27-7.97 (m, 5H), 9.90 (t, J=6 Hz, 1H), 11.16 (s, 1H). 13C NMR (DMSO-d6) δ: 21.98, 30.93, 40.33, 48.89, 115.15, 118.27, 120.74, 122.07, 127.24, 131.54, 131.96, 133.20, 134.88, 138.13, 156.43, 156.52, 156.97, 160.91, 166.93, 167.49, 169.82, 172.75. Anal Calcd for C22H16N4O6+0.2H2O: C, 60.61; H, 3.79; N, 12.85. Found: C, 60.38; H, 3.50; N, 12.80.
