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Method for preparing L-theanine by chemical method

A technology of theanine and chemical method, applied in chemical instruments and methods, preparation of organic compounds, organic chemistry, etc., can solve the problems of easy racemization of products and low yield, and achieve good economical effect

Inactive Publication Date: 2012-09-26
NANJING TECH UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Compared with the other three methods, the chemical synthesis method has the advantages of low cost, relatively simple operation, and easy industrial production, but there are also low yields, and the product is easy to racemize, including D and L isomers, which needs to be further carried out. Split and other issues

Method used

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  • Method for preparing L-theanine by chemical method
  • Method for preparing L-theanine by chemical method
  • Method for preparing L-theanine by chemical method

Examples

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Comparison scheme
Effect test

Embodiment 1

[0030] Example 1: Preparation of N-benzylproline.

[0031] L-proline (0.30 mol) and potassium hydroxide (0.90 mol) were dissolved in 200 mL of isopropanol, under nitrogen protection, stirred, and heated to 40°C. Benzyl chloride (0.45mol) was slowly added dropwise, maintaining the temperature and stirring was continued for 6h. Neutralize to pH=6 with concentrated hydrochloric acid, add 80 mL of chloroform to the reaction mixture, and let stand overnight. Filter, wash the filter cake with chloroform until the washing liquid is colorless, combine the organic phases, evaporate the solvent, recrystallize the crude product with acetone, and dry it under vacuum at 60°C to obtain 57.9 g of N-benzylproline, with a yield of 94.0% , m.p.175~176℃; 1 H NMR (CDCl 3 , 300MHz) δ: 9.90(s, 1H), 7.46~7.28(m, 5H), 4.45, 4.17(AB, J=13.0Hz, 2H), 3.81(dd, J=8.8, 6.6Hz, 1H), 3.70 ~3.62(m, 1H), 2.91~2.82(m, 1H), 2.36~2.20(m, 2H), 2.06~1.87(m, 2H); HRMS(ESI) calcd for C 12 h 15 NNaO 2 [M+Na] + ...

Embodiment 2

[0032] Embodiment 2: chiral auxiliary agent---the preparation of 2-[N-(N'-benzyl-prolyl)amino]benzophenone.

[0033] Dissolve the N-benzylproline (0.20mol) obtained in Example 1 in 200mL of dichloromethane, stir at 0°C, add thionyl chloride (0.4mol) dropwise, continue stirring after dropping, add 2-amino Benzophenone (0.20mol / 50mL dichloromethane) solution, return to room temperature, continue the reaction for 10h, add saturated aqueous sodium carbonate solution to stop the reaction, adjust pH=7, separate the organic phase, dry over anhydrous sodium sulfate, filter, and evaporate the solvent , the crude product was recrystallized from absolute ethanol, and dried under vacuum at 60°C to obtain 65.4 g of 2-[N-(N'-benzyl-prolyl)amino]benzophenone, with a yield of 85.1%, m.p.100-101 ℃; 1 H NMR (DMSO-d 6 , 500MHz) δ: 11.03(s, 1H), 8.30(dd, J=8.3, 0.8Hz, 1H), 7.74~7.72(m, 2H), 7.69~7.65(m, 1H), 7.60~7.54(m, 3H), 7.46(dd, J=7.8, 1.5Hz, 1H), 7.31~7.29(m, 2H), 7.20~7.17(m, 1H), 7.14...

Embodiment 3

[0034] Example 3: Preparation of glycine Schiff base Ni(II) complex.

[0035] The chiral auxiliary agent BPB (0.005mol), nickel chloride hexahydrate (0.01mol) and glycine (0.025mol) obtained in Example 2 were dissolved in 17.5mL of methanol, under nitrogen protection, stirred, and heated to 40-50°C. Add potassium hydroxide (0.035mol / 7.5mL methanol) solution, stir at 55-65°C for 1h, cool to room temperature, add acetic acid (0.035mol) under stirring, pour the above mixture into 75mL of water, and a large amount of crystals are precipitated. It was filtered and the crystals were washed twice with water. The crude product was recrystallized with acetone and dried under vacuum at 60°C to obtain 2.4 g of a glycine Schiff base Ni(II) complex with a yield of 96.3%, m.p.219-220°C; 1 H NMR (CDCl 3 , 500MHz) δ: 8.31(d, J=8.7, 1H), 8.07(d, J=7.1Hz, 2H), 7.53~7.49(m, 3H), 7.43(t, J=7.5Hz, 2H), 7.31 (t, J=7.4Hz, 1H), 7.23~7.19(m, 1H), 7.10(d, J=7.1, 1H), 6.98(d, J=4.5Hz, 1H), 6.80(dd, J...

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Abstract

The invention discloses a method for preparing L-theanine by a chemical method. The method comprises the following steps: firstly, reacting ethylamine with acryloyl chloride in the presence of an alkali to obtain N-ethylacrylamide; secondly, perform Michael addition reaction on chiral auxiliary BPB based glycine Schiff base Ni(II) coordination compound and the N-ethylacrylamide in the presence ofthe alkali to obtain theanine Schiff base Ni(II) coordination compound; and finally, performing acid hydrolysis on the theanine Schiff base Ni(II) coordination compound to prepare the L-theanine. Themethod adopts the chiral auxiliary chemical method to prepare the L-theanine, and constructs a complete theanine fragment through the Michael addition reaction so as to prepare the theanine Schiff base Ni(II) coordination compound, wherein the rigid space structure of the coordination compound can maintain the L-configuration of the theanine so as to ensure the optical purity of the L-theanine. The method can reclaim the chiral auxiliary in high yield, and can elute Ni(II) ions through ion exchange for recycling.

Description

technical field [0001] The invention relates to a method for preparing L-theanine by chemical method. Background technique [0002] L-theanine, namely N-ethyl-γ-L-glutamine (theanine, N-ethyl-γ-L-glutamine), is a unique amino acid in tea and an effective taste substance in green tea. The content of L-theanine directly determines the quality of tea. No matter what grade of tea, L-theanine accounts for more than 50% of the free amino acids in tea, and the content in dry tea is about 1% to 2% (Liu Yuan, Wang Jian. The latest research progress of theanine. China Food and Nutrition, 2007, (10): 23~25.). As early as 1950, Japanese scholar Yajiro Sato extracted, refined and determined the chemical structure of L-theanine from tea for the first time. In the following 50 years, many scholars have conducted systematic research on L-theanine from the aspects of tea tree physiology, cultivation, breeding, biochemistry and quality chemistry. In the past 10 years, the focus of research...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07C237/06C07C231/14
Inventor 周佳栋曹飞王月霞李振江黄荣醒张芙蓉杨颖朱优江韦萍
Owner NANJING TECH UNIV
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