Imidazole → L-Methionine

A mixture of 1.74 g. of 5-(β-methylthioethyl)hydantoin, 68 mg. of imidazole and 20 ml. of water was heated to 160° C. in a 50 ml. autoclave and then allowed to react for 3 hours at 160° C., while being stirred. After the reaction was over, the autoclave was rapidly cooled to room temperature and the residual pressure was released. The autoclave was given a good wash with water to take off the reaction mixture, and then the reaction mixture was subjected to evaporation to dryness by means of a rotary evaporator. The resulting solid was shaken sufficiently with 100 ml. of methyl acetate. The methyl acetate insoluble matter was separated from the methylacetate solution. A portion of of the insoluble matter was recrystallized from water and then subjected to an infrared absorption spectrum and melting point measurements (m.p. 267° C., decomposed). Thus, it was found to be methionine. On the other hand, the methyl acetate soluble matter was found to be unreacted 5-(β-methylthioethyl)hydantoin and a negligible amount of by-products. According to a copper chelatemetric colorimetry of the insoluble matter (the colorimetry was conducted according to the method described in the specification of Japanese Laid-Open Patent Application No. 116008/1974), it was found that 0.75 g. of methionine (yield 50%) was attained.