35% |
With benzotriazol-1-ol; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride; N-ethyl-N,N-diisopropylamine; In water; N,N-dimethyl-formamide; at 20.0℃; for 24.0h;Inert atmosphere; |
Step 3. Synthesis of rac-2-Acetamido-N-(2,6-dioxopiperidin-3-yi)-6-nitrobenzamide [00302] The starting acid (3.10 g, 13.8 mmol) was mixed with hydroxybenzotriazole (HOBt, 2.12 g of the hydrate, 13.8 mmol) and l-ethyl-3-(3-dimethylaminopropyl)- carbodiimide hydrochloride (EDC, 2.54 g, 13.3 mmol), under a nitrogen atmosphere. N,N- dimethylformamide (DMF, 21.4 mL) was added and the mixture was stirred for 30 minutes at room temperature. rac-3-Aminopiperidine-2,6-dione hydrochloride (5.01 g, 30.4 mmol) was added, followed by Nu,Nu-diisopropylethylamine (DIEA, 9.63 mL, 55.3 mmol). The reaction mixture was stirred at 20C, while monitoring by HPLC. After 24 hours, the reaction mixture showed approximately 40% conversion to the desired product containing some remaining starting acid, but no amine. Then, the reaction mixture was slowly poured into 200 mL water with vigorous stirring. After 20 minutes, a white precipitate began to form. The mixture was placed in the refrigerator for 18 hours. Then, the precipitate was isolated by filtration. The filter cake was washed with 50 mL ether, and air dried to provide the title compound (1.60 g, 4.79 mmol, 35%) as a white powder. XH NMR (300 MHz, DMSO-d6) delta 1 1.16 (s, 1H), 9.40 (s, 1H), 9.34 (d, J = 8.0 Hz, 1H), 8.53 (d, J = 7.5 Hz, 1H), 7.89 (dd, J = 8.2, 0.98 Hz, 1H), 7.66 (t, J = 8.3 Hz, 1H), 4.79 (m, 1H), 2.85(m, 1H), 2.59 (m, 1H), 2.21 (m, 1H), 2.20 (s, 3H), 2.03 (m, 1H). MS (ESI-) calc. for [Ci4H14N406-H]" 333.3, found 333.2. |