Synthesis method of L- glutamine

L- glutamine exists widely in nature, for example, in the free state in the seedlings of pumpkin and sunflower, and its N- ethyl compound (theanine) exists in tea. Although glutamine can be extracted from natural products, fermentation and synthesis are used in large-scale production. 1.L- glutamic acid -5- methyl ester ([1499-55-4]) is synthesized by condensation, addition, salification and hydrolysis. Glutamic acid is esterified with methanol in the presence of concentrated sulfuric acid, and the obtained esterification solution is dripped into the mixed solution of methanol and carbon disulfide, and ammonia gas is introduced when cooling. After the esterification solution was added dropwise, ammonia gas was continuously introduced, then triethylamine was added, and it was sealed at 30℃ for 40 hours. Concentrated under reduced pressure and discharged ammonia to obtain γ-methyl ester -L- glutamic acid -N- ammonium carbamate concentrated solution. Heat to 40-45℃ and add acetic acid. After stirring for 30 minutes, carbon disulfide was removed under reduced pressure, and a large number of crystals were precipitated. Then, the same volume of methanol was added, and the crude glutamine was obtained by standing at 0℃ for 65438±02h and filtering. Decolorize activated carbon and recrystallize to obtain that finished product. 2. In the fermentation method, glucose or acetic acid and ethanol are used as carbon sources of the culture medium, and Brevibacterium flavum is used for fermentation. The yield was 39g/L, which was 39% based on glucose.