METHOD FOR PREPARING 3-CARBAMOYMETHYL-5-METHYLHEXANOIC ACID IN RECYCLING WAY

The present invention provides a method for recycling 3-carbamoymethyl-5-methylhexanoic acid from 3-carbamoymethyl-5-methylhexanoic acid chiral resolving mother liquor. The method comprises the following steps: (a) distilling 3-carbamoymethyl-5-methylhexanoic acid chiral resolving mother liquor, adding aromatic hydrocarbon, heating to dissolve, keeping the temperature and stirring; (b) after completing the reaction in step (a), cooling the reaction solution to 30-60° C., then adding alkali liquor dropwise, keeping the temperature and reacting; and (c) after completing the reaction in step (b), cooling the reactant to 20-30° C., layering, adjusting the pH of the separated water layer to 1 to 2, performing extraction by using an organic solvent, distilling an organic phase under a reduced pressure, and crystallizing at 0±5° C. to obtain 3-carbamoymethyl-5-methylhexanoic acid. The method provided in the present invention is convenient to operate, and the recycled product is high in purity (≧99.8%) and yield.