Sulfur-containing amino acids such as methionine and S-alkyl cysteine exist commonly in the all organisms, and they are useful components for many important biological reactions. Particularly, methionine is an essential amino acid, which is an important compound for use as a feed additive.
For example, the following method is disclosed in “industrial organic chemistry”, Tokyo Kagaku-Dojin, 1978, pp. 273-275: 3-(methylthio)propanal obtained by addition of methanethiol to acrolein is reacted with hydrogen cyanide to obtain 2-hydroxyl-4-methylthiobutyronitrile; and then, the 2-hydroxyl-4-methylthiobutyronitrile is reacted with ammonium carbonate to obtain a substituted hydantoin and thereafter, the substituted hydantoin is hydrolyzed by an alkali. In addition, the following method is disclosed in “Chem. Ber.”, vol. 121, 1988, pp. 2209-2223: methanethiol is added to methyl 2-chloroacrylate; and then, the resultant adduct is reacted with a sodium azide and thereafter, the resultant product is hydrogenated under acidic conditions.