Abstract
5-Aminolevulinic acid (ALA) is known as a selective and biodegradable herbicide which is also recognized as the growth promotive factor at low concentration. The authors studied on the synthesis of ALA from 1, 5-dihydroxy-2-pyridone (DHPy) via piperidine-2, 5-dione (PDO). DHPy can be obtained easily from 2-furaldehyde by the conventional method. PDO was synthesized from DHPy by the reductive dehydroxylation with 5% Pd-C catalyst in an ethanol solution under a hydrogen atmosphere for 24hours refluxing. However, yield of PDO was 14% and that of 5-hydroxy-2-pyridone (HPy) was 28%. Considering the deactivation of the catalyst by the basic products, dil. HCl or acetic acid was added into the ethanol solution. As the result, dil. HCl addition reduced PDO yield, while acetic acid addition enhanced PDO yield. Furthermore, PDO yield was increased to 65 % and HPy yield was 21% when the reaction was carried out at room temperature in an acetic acid solution. HPy, by-product of this reaction, could be converted to PDO in 75% yield by the reduction with Pd-C in a methanol solution at room temperature. Therefore, the total yield of PDO was about 80%. PDO was hydrolyzed with dil. HCl and the final product of ALA HCl was obtained in 60% yield.
