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The general procedure for the synthesis of 3-(aminocarbonylmethyl)-5-methylhexanoic acid using 4-isobutyldihydro-2H-pyran-2,6(3H)-dione as a starting material was as follows: first, 70 g of the dried product of 3-isobutylglutaric acid was reacted with 70 g of acetic anhydride at 120 °C for 2 h to produce 3-isobutylglutaric anhydride. Subsequently, 75g of 3-isobutylglutaric anhydride solution was slowly added dropwise to 180g of ammonia, and the temperature was controlled at 10°C during the reaction. After the dropwise addition, the reaction was continued for 2 hours. After the completion of the reaction, the pH of the solution was adjusted to 2~3 with hydrochloric acid, and a white powdery solid was obtained by filtration, i.e., the target product 3-isobutylglutaric acid monoamide. Liquid phase detection of the product showed a purity of 99.8%, a yield of 95% and an overall yield of 77.5%. Figure 4 illustrates the liquid phase assay results of 3-isobutylglutaric acid monoamide.

[1] Patent: CN106278931, 2017, A. Location in patent: Paragraph 0038; 0039; 0040
[2] Patent: WO2012/93411, 2012, A2. Location in patent: Page/Page column 18-19
[3] Patent: WO2009/4643, 2009, A2. Location in patent: Page/Page column 26
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