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General procedure for the synthesis of 2,4-dimethyl-3-pyrrolepropionic acid from ethyl 4-(3-methoxy-3-oxopropyl)-3,5-dimethyl-1H-pyrrole-2-carboxylate: ethyl 4-(2-methoxycarbonylethyl)-3,5-dimethyl-1H-pyrrole-2-carboxylate (Aldrich, 228 g, 0.9 mol) was reacted with 720 mL of 5 N sodium hydroxide solution were mixed and reacted at reflux for 1 hour. The progress of the reaction was monitored by thin layer chromatography (TLC) to confirm the completion of the hydrolysis reaction. The reaction mixture was cooled to 50 °C with stirring, and the pH was adjusted to 2-3 by slowly adding 10 N hydrochloric acid (390 mL). after solidification of the oil was observed, stirring was continued and the mixture was cooled to 4 °C. The reaction was then purified by vacuum filtration. The solid product was collected by vacuum filtration, washed well with water and subsequently dried under vacuum at 40 °C to afford 65.7 g (49% yield) of 3-(2,4-dimethyl-1H-pyrrol-3-yl)propionic acid as a slightly red solid.

[1] Journal of Organic Chemistry, 1988, vol. 53, # 12, p. 2796 - 2802
[2] Patent: US2004/204407, 2004, A1. Location in patent: Page/Page column 16-17
[3] Patent: US2004/266843, 2004, A1. Location in patent: Page 12