Acetonitrile → 5-[2-(2-acetylamino-ethylcarbamoyl)-ethyl]-3-methyl-1H-pyrrole-2,4-dicarboxylic acid 2-tert-butyl ester 4-ethyl ester

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Reaction Steps

5-(2-Carboxy-ethyl)-3-methyl-1H-pyrrole-2,4-dicarboxylic acid 2-tert-butyl ester 4-ethyl ester 1e (9.85 g, 30.3 mmol) obtained from step 4 of Example 1 was dissolved in acetonitrile (50 ml) under stirring, and added with 1-hydroxy-1H-benzotriazole (8.2 g, 60.6 mmol) and N-ethyl-N′-(3-dimethylaminopropyl)carbodiimide (11.6 g, 60.6 mmol) to the solution at room temperature. Upon completion of the addition, the reaction mixture was stirred at room temperature overnight. After thin lay chromatography showed the disappearance of starting materials, the reaction mixture was concentrated under reduced pressure, added with water (200 ml), and exacted with ethyl acetate (200 ml×4). The combined organic extracts were washed with saturated brine (100 ml), dried over anhydrous magnesium sulfate, filtered to remove the drying agent and concentrated under reduced pressure. The residue was purified by silica gel column chromatography to obtain the title compound 5-[2-(2-acetylamino-ethylcarbamoyl)-ethyl]-3-methyl-1H-pyrrole-2,4-dicarboxylic acid 2-tert-butyl ester 4-ethyl ester 62a (8 g, yield 65%) as a white solid.

Provenance & Evidence