[C:1]([CH:4](C)[C:5](=O)[CH2:6][CH2:7][C:8]([O:10][CH2:11][CH3:12])=[O:9])(=O)C.Cl.[NH2:16][CH:17]([C:23](O)=O)[C:18]([O:20][CH2:21][CH3:22])=[O:19].[C:26]([O-])(=O)C.[Na+].C(=O)=O>C(O)(=O)C>[CH2:21]([O:20][C:18]([C:17]1[NH:16][C:4]([CH3:1])=[C:5]([CH2:6][CH2:7][C:8]([O:10][CH2:11][CH3:12])=[O:9])[C:23]=1[CH3:26])=[O:19])[CH3:22]To a 5 L three-neck flask equipped with a thermometer and a mechanical stirrer and heated on a steam bath was added 350 g ethyl 5-acetyl-4-oxohexanoate, 329 g ethyl aminomalonate hydrochloride, 133 g sodium acetate and 1.2 L acetic acid. The mixture was heated to 99° C. over 37 minutes. By 62° C., carbon dioxide evolution was already rapid. After a total of 35 minutes at 99° C. gas, CO2 evolution had greatly slowed. After another hour, the mixture was cooled, sodium chloride removed by vacuum filtration, and the solvent evaporated. The residue was mixed with 1 L of cold water. The precipitate was collected by vacuum filtration, washed with 400 mL water, and dissolved in 1 L of hot 95% ethanol. The solution was treated with 20 g of Darco G-60, hot-filtered, and cooled to room temperature. The crystalline solid was collected by vacuum filtration, washed twice on the filter with 200 mL of 50% ethanol and dried under vacuum at 70° C. to give 285 g (64% yield) of 2-ethoxycarbonyl-4-(2-ethoxycarbonylethyl)-3,5-dimethylpyrrole. The filtrate was refrigerated overnight to give another 53.1 g (11.9% yield) of product for a total yield of 75.9%).
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