The present invention relates to a (S)-2-methyl-1,4,5,6-tetrahydromethylpyrimidine-4-
carboxylic acid synthesis method. According to the method, L-
glutamine is used as a
raw material, the alpha-amino of the L-
glutamine is protected with a protection group, a decarbonylating agent is added, a Hofmann
degradation reaction is performed to remove the
carbonyl group attached to the remaining amino, the protection group is removed to obtain L-2,4-diaminobutyric acid, and finally the prepared L-2,4-diaminobutyric acid and trimethyl orthoacetate are subjected to a ring forming reaction to obtain the (S)-2-methyl-1,4,5,6-tetrahydromethylpyrimidine-4-
carboxylic acid. Compared to the method in the prior art, the method of the present invention has the following characteristics that the
chemical synthesis route is provided, the steps of the synthesis process are simple, the raw materials are easy to obtain, the product purity is high, and the method is suitable for large-scale industrial production.