Synthesis method of (2S, 3R)-3-(4-methoxyphenyl) serine

Abstract

The invention relates to the field of medicinal chemistry, in particular to a synthesis method of (2S, 3R)-3-(4-methoxyphenyl) serine. The invention relates to a synthesis method of (2S, 3R)-3-(4-methoxyphenyl) serine, which comprises the following steps: carrying out condensation reaction on p-methoxybenzaldehyde and glycine to obtain a compound 1; adding into water containing a polar solvent, adding an alkaline compound and acetic anhydride, reacting, drying, filtering and concentrating to obtain a compound 2; adding L-acetylase into the compound 2 to react, and treating a crude product to obtain a compound 3; in order to effectively improve the problems of low production efficiency, tedious intermediate purification steps and difficulty in industrial large-scale synthesis of the existing target product in a synthesis process, high chemical purity and high chiral selectivity of the product are achieved through cooperation of the steps; the reaction path is simple, the operation is simple and convenient, harsh reaction conditions or complex purification equipment is not needed, and industrial large-scale production requirements are met.

Description

Technical Field

[0001] This application relates to the field of medicinal chemistry, specifically to a method for synthesizing (2S,3R)-3-(4-methoxyphenyl)serine. Background Technology

[0002] (2S,3R)-3-(4-methoxyphenyl)serine is a key chiral intermediate for selective immunoproteasome inhibitors (such as carfilzomib derivatives) used to treat autoimmune diseases. Its chiral purity and chemical purity directly determine the in vivo activity and toxic side effects of the drug, and it has vital application value in the pharmaceutical and chemical fields.

[0003] Currently, there are two main types of technical routes for synthesizing this compound both domestically and internationally: one type uses a chiral auxiliary group as the core, such as the method reported by Liebigs Annalen der Chemie (1991, 753: 121-135): the synthetic route is as follows:

[0004] Reagents such as bis(trimethylsilylamine) lithium are used to react under low temperature conditions, but chiral cofactors are expensive and difficult to supply on the market, and the reaction conditions are harsh, making it difficult to meet the needs of drug development and industrial production. Another approach involves separating the target product from four chiral isomers using high-performance liquid chromatography (HPLC), as reported in the literature published in the Journal of Medicinal Chemistry, 2018, vol. 61 [11127–11143]. However, this method suffers from high production costs, low separation efficiency, limited product yield, and generates a large amount of organic waste liquid during the chromatographic separation process, resulting in poor environmental friendliness. Furthermore, existing routes may have issues such as cumbersome intermediate purification steps, high reagent toxicity, and insufficient chiral excess values, which restrict the large-scale supply and application expansion of this key intermediate. Summary of the Invention

[0005] In order to effectively improve the problems of low production efficiency, cumbersome intermediate purification steps, and difficulty in large-scale industrial synthesis of (2S,3R)-3-(4-methoxyphenyl)serine, this application provides a method for synthesizing (2S,3R)-3-(4-methoxyphenyl)serine.

[0006] In a first aspect, this application provides a method for synthesizing (2S,3R)-3-(4-methoxyphenyl)serine, the reaction formula of which is shown in Formula I, comprising the following steps:

[0007] Step (1): Add p-methoxybenzaldehyde to tetrahydrofuran solution, add glycine, and then add potassium hydroxide in batches to undergo a condensation reaction. After post-treatment, compound 1 is obtained. Step (2): Add compound 1 obtained in step (1) to water containing a polar solvent, add an alkaline compound and acetic anhydride, react for 3-5 hours, dry, filter, and concentrate to obtain compound 2; Step (3): Take compound 2 obtained in step (2) and add it to water. Add alkali solution to adjust the pH to 8-9. Add L-acetyltransferase at 40-50℃ and react for 24-48 hours. Crude product treatment yields compound 3.

[0008] Preferably, the condensation reaction in step (1) is carried out at a temperature of 10-30℃ and the reaction is stirred for 12-24 hours.

[0009] More preferably, the condensation reaction in step (1) is carried out at a temperature of 25°C.

[0010] A further preferred embodiment is that the mass ratio of p-methoxybenzaldehyde to glycine is (2-3):1.

[0011] This application achieves the preparation of (2S,3R)-3-(4-methoxyphenyl)serine through a three-step reaction linkage: configuration-oriented generation, precise group protection, and enzyme-catalyzed specific recognition. The first step, configuration control, reduces cumbersome purification steps; the second step protects and optimizes the enzyme's recognition environment; and the third step, enzyme catalysis, achieves the targeted retention of the target configuration. Finally, through the coordination of these steps, high chemical purity and high chiral selectivity of the product are achieved. The reaction path is simple and easy to operate, and the raw materials are widely available and readily available. No harsh reaction conditions or complex purification equipment are required, making it suitable for large-scale industrial production.

[0012] The first step, the condensation reaction, yields a high-purity intermediate without complex purification procedures, simplifying the process, reducing product loss, and providing a pure and structurally compatible substrate for subsequent reactions, avoiding interference from impurities in site-specific reactions. The second step involves a precise acylation reaction between the high-purity threonine intermediate generated in the first step and acetic anhydride, producing a product protected by an acetylamino group. This avoids non-specific binding of the free amino group to the active site of subsequent enzymes and provides a specific recognition site for enzymatic resolution, ensuring the selectivity of subsequent enzymatic catalysis. The third step, enzymatic resolution, utilizes the specific recognition capability of L-acetyltransferase, combined with the acetylamino protecting group introduced in the second step, to precisely identify and act on the target isomer (2S,3R)-isomer. Non-target isomers are retained due to poor spatial structure compatibility with the enzyme's active site. This selective catalysis creates a significant polarity difference between the target product and the non-target isomers: subsequent simple extraction achieves efficient separation without complex chromatographic separation or expensive chiral reagents. This process ensures the chiral purity of the target product, simplifies post-processing steps, and features mild and environmentally friendly reaction conditions, significantly improving the overall efficiency and industrial adaptability of the process.

[0013] By utilizing the ratio range of p-methoxybenzaldehyde to glycine disclosed in this application, the amino group of glycine loses a proton under alkaline conditions, forming an amino anion with strong nucleophilicity. This anion can directionally attack the electrophilic carbon of the aldehyde group, forming an imine intermediate. At this point, the benzene ring of p-methoxybenzaldehyde forms significant steric hindrance with the methoxy group, restricting the attack direction of the hydroxyl group on the imine carbon. This forces the hydroxyl group to attack only from the reverse side of the benzene ring, resulting in a threo-racemic structure with the C2-amino and C3-hydroxyl groups arranged in an anti-reaction configuration, thus avoiding the formation of erythro-isomers and condensation byproducts from the starting material itself. Therefore, insufficient p-methoxybenzaldehyde content may reduce the specificity and efficiency of the reaction. In an alkaline environment, excessive glycine content easily leads to dehydration condensation to form a dipeptide product. This dipeptide contains amino and carboxyl groups similar to the threo-intermediate, increasing the difficulty of post-processing, reducing the chemical purity of the product, and potentially interfering with the site specificity of the acetylation reaction. Ultimately, this results in a simultaneous decrease in the chiral purity and yield of the target product.

[0014] Preferably, the post-treatment in step (1) includes adding hydrochloric acid to adjust the pH to 5-6, filtering, rinsing with water and ethyl acetate, and drying.

[0015] Preferably, the alkaline compound in step (2) includes one or more of sodium carbonate, potassium carbonate, sodium bicarbonate, triethylamine, and N,N-diisopropylethylamine.

[0016] More preferably, the alkaline compound in step (2) is sodium carbonate; Preferably, the polar solvent in step (2) includes one or more of dioxane, tetrahydrofuran, and N,N-dimethylformamide.

[0017] In step (2) of this application, sodium carbonate is the preferred basic compound. After hydrolysis, it efficiently activates the intermediate amino group, enhancing the reactivity. It can also promptly neutralize the acetic acid produced by acetylation, and the residue can be easily removed by extraction, making it more suitable for industrial production. It can simultaneously improve the solubility of the threo-intermediate and acetic anhydride, ensuring that the amino acetylation reaction is uniform and sufficient, generating the target intermediate. Step 2 ensures a high conversion rate and intermediate purity of the acetylation reaction, and provides a precise recognition site for subsequent enzymatic resolution, avoiding non-specific interference of free amino groups on the enzyme active site. While improving product purity and yield, it also reduces process costs, simplifies the operation process, and enhances the overall industrial adaptability of the process.

[0018] Preferably, in step (3), L-acetyltransferase accounts for 4%-8% of the mass of compound 2.

[0019] More preferably, step (3) above also includes the addition of 4-methoxybenzoic acid grafted L-lactate dehydrogenase, wherein the mass ratio of 4-methoxybenzoic acid grafted L-lactate dehydrogenase to L-acetylase is 1:(4-6).

[0020] A further preferred method for preparing 4-methoxybenzoic acid-grafted L-lactate dehydrogenase includes: dissolving L-lactate dehydrogenase in phosphate buffer, adding EDC and NHS, stirring and activating for 30-45 min, adding 4-methoxybenzoic acid, stirring and reacting at 35-40℃ for 4-6 h, purifying by column chromatography, and freeze-drying to obtain 4-methoxybenzoic acid-grafted L-lactate dehydrogenase.

[0021] In this application, the enzymatic reaction in step (3) is the core of achieving high chiral purity of the target product. The active site of L-acetyltransferase can rapidly recognize the (2S,3R) isomer that has not been fixed in the conformation by L-lactate dehydrogenase grafted with 4-methoxybenzoic acid, and catalyze the hydrolysis of its acetyl group to an amino group. Its natural substrate recognition characteristic is that it preferentially binds to compounds in the threotype configuration where the acetylamino group and hydroxyl group are arranged in trans configuration.

[0022] To further improve chiral selectivity, the inventors grafted 4-methoxybenzoic acid onto L-lactate dehydrogenase using L-acetyltransferase. The protein backbone of L-lactate dehydrogenase can interact with non-target isomers, thereby reducing contact between non-target isomers and L-acetyltransferase and improving its catalytic efficiency. After 4-methoxybenzoic acid grafting modification, the binding ability of L-lactate dehydrogenase to non-target isomers is significantly enhanced, thus improving the chiral selectivity of L-acetyltransferase and increasing the purity of diastereomers. Furthermore, the protein backbone of L-lactate dehydrogenase can stabilize the spatial conformation of L-acetyltransferase, reducing deformation of the active site caused by environmental fluctuations, further improving its recognition accuracy of target isomers and increasing the purity of diastereomers. Therefore, when the content of 4-methoxybenzoic acid grafted L-lactate dehydrogenase is too low, it cannot completely capture non-target isomers. The unbound (2R,3S)-isomers may still interact weakly with L-acetyltransferase, resulting in a decrease in chiral purity.

[0023] Preferably, the crude product treatment step (3) involves adding activated carbon and stirring for 1-2 hours, filtering, adding hydrochloric acid to the aqueous phase to adjust the pH to 2-3, extracting with ethyl acetate, concentrating to precipitate the solid, filtering, and drying to obtain the product.

[0024] Preferably, the alkaline solution in step (3) is a 1N-2N sodium hydroxide solution.

[0025] In the crude product processing, activated carbon adsorption is added to remove L-acetyltransferase and 4-methoxybenzoic acid-grafted L-lactate dehydrogenase from the system. Filtration separates the enzymes from the reaction solution. Extraction separates the target product from non-target isomers. After aqueous concentration, the target product precipitates due to concentration saturation, resulting in a high-purity product.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. This application completes the preparation of (2S,3R)-3-(4-methoxyphenyl)serine through only three steps: configuration-oriented generation, precise group protection, and enzyme-catalyzed specific recognition. The configuration control in the first step reduces cumbersome purification steps, the second step protects and optimizes the enzyme's recognition environment, and the third step uses enzyme catalysis to achieve the targeted retention of the target configuration. Finally, through the coordination of each step, high chemical purity and high chiral selectivity of the product are achieved. The reaction path is simple and easy to operate, the raw materials are widely available and readily available, and there is no need for harsh reaction conditions or complex purification equipment, making it suitable for large-scale industrial production.

[0027] 2. By using enzyme-specific recognition, the target configuration (2S,3R) can be accurately separated from racemic mixtures, obtaining products with high chiral purity without the need for complex separation equipment. At the same time, the enzymatic reaction is environmentally friendly and in line with the concept of green synthesis. Detailed Implementation

[0028] In this application, L-acetyltransferase was purchased from Aladdin; L-lactate dehydrogenase was purchased from Maclean's; and Pseudomonas lipase was purchased from Sigma-Aldrich. Other raw materials were commercially available.

[0029] Preparation Example 1 Preparation of 4-methoxybenzoic acid-grafted L-lactate dehydrogenase: 28 g of L-lactate dehydrogenase was dissolved in 100 mL of 0.05 M phosphate buffer (pH 7.5), 1.2 g of EDC and 0.7 g of NHS were added, and the mixture was stirred and activated for 30 min. Then, 1.5 g of 4-methoxybenzoic acid was added, and the mixture was stirred at 35 °C for 4 h. The mixture was purified by column chromatography (elution buffer was 0.02 M phosphate buffer, pH 7.5), pre-frozen at -40 °C for 4 h, and then sublimed at -10 °C for 12 h under a vacuum of 5 Pa. Finally, the mixture was heated to 20 °C and dried for 4 h to obtain 4-methoxybenzoic acid-grafted L-lactate dehydrogenase. Example 1

[0030] A method for synthesizing (2S,3R)-3-(4-methoxyphenyl)serine includes the following steps: Step (1): 20 kg of tetrahydrofuran and 4 kg of p-methoxybenzaldehyde are added to a 50 L reactor, along with 1.5 kg of glycine. 2.7 kg of KOH is added in three batches at 25 °C, and the mixture is stirred for 24 h. The pH is adjusted to 5 with 6 N hydrochloric acid, filtered, rinsed with 2.5 L of water, and then rinsed with 2 L of ethyl acetate. The mixture is dried to obtain compound 1 (Pu: 99%, Yield: 41.6%). Step (2): Take compound 1 obtained in step (1) and add it to 20 L of dioxane aqueous solution (v:v=1:1). Add 1.9 kg of sodium carbonate and 1.87 kg of acetic anhydride and react for 3 h. Add 6N hydrochloric acid to adjust pH=2. Extract twice with ethyl acetate, adding 3 L each time. Add 0.5 kg of anhydrous sodium sulfate to the organic phase and dry. Filter and concentrate to obtain compound 2. Step (3): Take 3.95 kg of compound 2 obtained in step (2) and add it to 40 L of water. Add 1N sodium hydroxide solution to adjust the pH to 8. Heat in a 40℃ water bath, add 190 g of L-acetyltransferase and react for 48 h. Add activated carbon and stir for 1 h. Filter, add 6N hydrochloric acid to adjust the pH to 2 in the aqueous phase, extract twice with ethyl acetate, adding 2 L each time. Concentrate the aqueous phase to precipitate the solid, filter, and dry to obtain compound 3. (Pu: 99%, ee: 99%, Yield: 73%) Example 2

[0031] A method for synthesizing (2S,3R)-3-(4-methoxyphenyl)serine includes the following steps: Step (1): 20 kg of tetrahydrofuran and 4 kg of p-methoxybenzaldehyde are added to a 50 L reactor, along with 1.5 kg of glycine. 2.7 kg of KOH is added in three batches at 10 °C, and the mixture is stirred for 24 h. The pH is adjusted to 5 with 6 N hydrochloric acid, filtered, rinsed with 2.5 L of water, and then rinsed with 2 L of ethyl acetate. The mixture is dried to obtain compound 1 (Pu: 98.5%, Yield: 40.1%). Step (2): Take compound 1 obtained in step (1) and add it to 20 L of dioxane aqueous solution (v:v=1:1). Add 1.9 kg of sodium carbonate and 1.87 kg of acetic anhydride and react for 3 h. Add 6N hydrochloric acid to adjust pH=2. Extract twice with ethyl acetate, adding 3 L each time. Add 0.5 kg of anhydrous sodium sulfate to the organic phase and dry. Filter and concentrate to obtain compound 2. Step (3): Take 3.95 kg of compound 2 obtained in step (2) and add it to 40 L of water. Add 1N sodium hydroxide solution to adjust the pH to 8. Heat in a 40℃ water bath, add 190 g of L-acetyltransferase and react for 48 h. Add activated carbon and stir for 1 h. Filter, add 6N hydrochloric acid to adjust the pH to 2 in the aqueous phase, extract twice with ethyl acetate, adding 2 L each time. Concentrate the aqueous phase to precipitate the solid, filter, and dry to obtain compound 3. (Pu: 98.2%, ee: 98.5%, Yield: 71.5%) Example 3

[0032] A method for synthesizing (2S,3R)-3-(4-methoxyphenyl)serine includes the following steps: Step (1): 20 kg of tetrahydrofuran and 3 kg of p-methoxybenzaldehyde are added to a 50 L reactor, along with 2.5 kg of glycine. 2.7 kg of KOH is added in three batches at 25 °C, and the mixture is stirred for 24 h. The pH is adjusted to 5 with 6 N hydrochloric acid, filtered, rinsed with 2.5 L of water, and then rinsed with 2 L of ethyl acetate. The mixture is dried to obtain compound 1 (Pu: 98%, Yield: 38.6%). Step (2): Take compound 1 obtained in step (1) and add it to 20 L of dioxane aqueous solution (v:v=1:1). Add 1.9 kg of sodium carbonate and 1.87 kg of acetic anhydride and react for 3 h. Add 6N hydrochloric acid to adjust pH=2. Extract twice with ethyl acetate, adding 3 L each time. Add 0.5 kg of anhydrous sodium sulfate to the organic phase and dry. Filter and concentrate to obtain compound 2. Step (3): Take 3.95 kg of compound 2 obtained in step (2) and add it to 40 L of water. Add 1N sodium hydroxide solution to adjust the pH to 8. Heat in a 40℃ water bath, add 190 g of L-acetyltransferase and react for 48 h. Add activated carbon and stir for 1 h. Filter, add 6N hydrochloric acid to adjust the pH to 2 in the aqueous phase, extract twice with ethyl acetate, adding 2 L each time. Concentrate the aqueous phase to precipitate the solid, filter, and dry to obtain compound 3. (Pu: 98.8%, ee: 99%, Yield: 71.2%) Example 4

[0033] A method for synthesizing (2S,3R)-3-(4-methoxyphenyl)serine includes the following steps: Step (1): 20 kg of tetrahydrofuran and 4 kg of p-methoxybenzaldehyde are added to a 50 L reactor, along with 1.5 kg of glycine. 2.7 kg of KOH is added in three batches at 25 °C, and the mixture is stirred for 24 h. The pH is adjusted to 5 with 6 N hydrochloric acid, filtered, rinsed with 2.5 L of water, and then rinsed with 2 L of ethyl acetate. The mixture is dried to obtain compound 1. Step (2): Take compound 1 obtained in step (1) and add it to 20 L of dioxane aqueous solution (v:v=1:1). Add 1.9 kg of sodium carbonate and 1.87 kg of acetic anhydride and react for 3 h. Add 6N hydrochloric acid to adjust pH=2. Extract twice with ethyl acetate, adding 3 L each time. Add 0.5 kg of anhydrous sodium sulfate to the organic phase and dry. Filter and concentrate to obtain compound 2. Step (3): Take 3.95 kg of compound 2 obtained in step (2) and add it to 40 L of water. Add 1N sodium hydroxide solution to adjust the pH to 8. Heat in a 40℃ water bath, first add 30 g of 4-methoxybenzoic acid grafted L-lactate dehydrogenase prepared in Example 1, then add 160 g of L-acetyltransferase and react for 48 h. Add activated carbon and stir for 1 h. Filter, add 6N hydrochloric acid to the aqueous phase to adjust the pH to 2, extract twice with ethyl acetate, adding 2 L each time. Concentrate the aqueous phase to precipitate the solid, filter, and dry to obtain compound 3. (Pu: 99.5%, ee: 99.6%, Yield: 74.1%) Example 5

[0034] A method for synthesizing (2S,3R)-3-(4-methoxyphenyl)serine includes the following steps: Step (1): 20 kg of tetrahydrofuran and 4 kg of p-methoxybenzaldehyde are added to a 50 L reactor, along with 1.5 kg of glycine. 2.7 kg of KOH is added in three batches at 25 °C, and the mixture is stirred for 24 h. The pH is adjusted to 5 with 6 N hydrochloric acid, filtered, rinsed with 2.5 L of water, and then rinsed with 2 L of ethyl acetate. The mixture is dried to obtain compound 1. Step (2): Take compound 1 obtained in step (1) and add it to 20 L of dioxane aqueous solution (v:v=1:1). Add 1.9 kg of sodium carbonate and 1.87 kg of acetic anhydride and react for 3 h. Add 6N hydrochloric acid to adjust pH=2. Extract twice with ethyl acetate, adding 3 L each time. Add 0.5 kg of anhydrous sodium sulfate to the organic phase and dry. Filter and concentrate to obtain compound 2. Step (3): Take 3.95 kg of compound 2 obtained in step (2) and add it to 40 L of water. Add 1N sodium hydroxide solution to adjust the pH to 8. Heat in a 40℃ water bath, first add 30 g of L-lactate dehydrogenase, then add 160 g of L-acetyltransferase and react for 48 h. Add activated carbon and stir for 1 h. Filter, add 6N hydrochloric acid to adjust the pH to 2 in the aqueous phase, extract twice with ethyl acetate, adding 2 L each time. Concentrate the aqueous phase to precipitate the solid, filter, and dry to obtain compound 3. (Pu: 99.2%, ee: 99.1%, Yield: 73.4%) Example 6

[0035] A method for synthesizing (2S,3R)-3-(4-methoxyphenyl)serine includes the following steps: Step (1): 20 kg of tetrahydrofuran and 4 kg of p-methoxybenzaldehyde are added to a 50 L reactor, along with 1.5 kg of glycine. 2.7 kg of KOH is added in three batches at 25 °C, and the mixture is stirred for 24 h. The pH is adjusted to 5 with 6 N hydrochloric acid, filtered, rinsed with 2.5 L of water, and then rinsed with 2 L of ethyl acetate. The mixture is dried to obtain compound 1. Step (2): Take compound 1 obtained in step (1) and add it to 20 L of dioxane aqueous solution (v:v=1:1). Add 1.9 kg of sodium carbonate and 1.87 kg of acetic anhydride and react for 3 h. Add 6N hydrochloric acid to adjust pH=2. Extract twice with ethyl acetate, adding 3 L each time. Add 0.5 kg of anhydrous sodium sulfate to the organic phase and dry. Filter and concentrate to obtain compound 2. Step (3): Take 3.95 kg of compound 2 obtained in step (2) and add it to 40 L of water. Add 1N sodium hydroxide solution to adjust the pH to 8. Heat in a 40℃ water bath, first add 38 g of 4-methoxybenzoic acid grafted L-lactate dehydrogenase prepared in Example 1, then add 152 g of L-acetyltransferase and react for 48 h. Add activated carbon and stir for 1 h. Filter, add 6N hydrochloric acid to adjust the pH to 2 in the aqueous phase, extract twice with ethyl acetate, adding 2 L each time. Concentrate the aqueous phase to precipitate the solid, filter, and dry to obtain compound 3. (Pu: 98.7%, ee: 99.4%, Yield: 73.6%) Example 7

[0036] A method for synthesizing (2S,3R)-3-(4-methoxyphenyl)serine includes the following steps: Step (1): 20 kg of tetrahydrofuran and 4 kg of p-methoxybenzaldehyde are added to a 50 L reactor, along with 1.5 kg of glycine. 2.7 kg of KOH is added in three batches at 25 °C, and the mixture is stirred for 24 h. The pH is adjusted to 5 with 6 N hydrochloric acid, filtered, rinsed with 2.5 L of water, and then rinsed with 2 L of ethyl acetate. The mixture is dried to obtain compound 1. Step (2): Take compound 1 obtained in step (1) and add it to 20 L of dioxane aqueous solution (v:v=1:1). Add 1.9 kg of sodium carbonate and 1.87 kg of acetic anhydride and react for 3 h. Add 6N hydrochloric acid to adjust pH=2. Extract twice with ethyl acetate, adding 3 L each time. Add 0.5 kg of anhydrous sodium sulfate to the organic phase and dry. Filter and concentrate to obtain compound 2. Step (3): Take 3.95 kg of compound 2 obtained in step (2) and add it to 40 L of water. Add 1N sodium hydroxide solution to adjust the pH to 8. Heat in a 40℃ water bath, first add 23 g of 4-methoxybenzoic acid grafted L-lactate dehydrogenase prepared in Example 1, then add 167 g of L-acetylase and react for 48 h. Add activated carbon and stir for 1 h. Filter, add 6N hydrochloric acid to the aqueous phase to adjust the pH to 2, extract twice with ethyl acetate, adding 2 L each time. Concentrate the aqueous phase to precipitate the solid, filter, and dry to obtain compound 3. (Pu: 99.5%, ee: 99.3%, Yield: 73.5%) Comparative Example 1 A method for synthesizing (2S,3R)-3-(4-methoxyphenyl)serine includes the following steps: Step (1): 20 kg of tetrahydrofuran and 4 kg of p-methoxybenzaldehyde are added to a 50 L reactor, along with 1.5 kg of glycine. 2.7 kg of KOH is added in three batches at 25 °C, and the mixture is stirred for 24 h. The pH is adjusted to 5 with 6 N hydrochloric acid, filtered, rinsed with 2.5 L of water, and then rinsed with 2 L of ethyl acetate. The mixture is dried to obtain compound 1. Step (2): Take compound 1 obtained in step (1) and add it to 20 L of dioxane aqueous solution (v:v=1:1). Add 1.9 kg of sodium carbonate and 1.87 kg of acetic anhydride and react for 3 h. Add 6N hydrochloric acid to adjust pH=2. Extract twice with ethyl acetate, adding 3 L each time. Add 0.5 kg of anhydrous sodium sulfate to the organic phase and dry. Filter and concentrate to obtain compound 2. Step (3): Take 3.95 kg of compound 2 obtained in step (2) and add it to 40 L of water. Add 1N sodium hydroxide solution to adjust the pH to 8. Heat in a 40℃ water bath, add 190 g of Pseudomonas lipase and react for 48 h. Add activated carbon and stir for 1 h. Filter, add 6N hydrochloric acid to adjust the pH to 2 in the aqueous phase, extract twice with ethyl acetate, adding 2 L each time. Concentrate the aqueous phase to precipitate the solid, filter, and dry to obtain compound 3. (Pu: 97.8%, ee: 94.1%, Yield: 68.8%) Based on the above comparative examples, Examples 1-3 show that in step 1 of this application, p-methoxybenzaldehyde and glycine undergo a condensation reaction, and the temperature of the condensation reaction is kept at 25°C, achieving high purity and yield. High-purity intermediates can be obtained without complicated purification operations. Furthermore, by using the ratio range of p-methoxybenzaldehyde to glycine disclosed in this application, the specificity and efficiency of configuration control are guaranteed, further reducing cumbersome purification steps and improving the purity and yield of the intermediates.

[0037] As can be seen from Examples 1, 4-7, and Comparative Example 1, in step 3 of this application, the enzymatic resolution utilizes the specific recognition ability of L-acetyltransferase. Combined with the acetylamino protecting group introduced in the second step, the active site of L-acetyltransferase exhibits a natural substrate recognition characteristic that preferentially binds to compounds in the threon configuration where the acetylamino group and hydroxyl group are arranged in trans configuration. That is, compound 2 in this application is a threon racemic mixture, which precisely matches the substrate configuration requirement of L-acetyltransferase. Furthermore, by introducing 4-methoxybenzoic acid to graft L-lactate dehydrogenase... The (2R,3S) isomer, which serves as an auxiliary enzyme with a fixed conformation, provides precise substrate guidance for L-acetyltransferase catalysis. This allows the active site of L-acetyltransferase to rapidly recognize the (2S,3R) isomer, which is not fixed in the conformation. The catalytic characteristic of this natural substrate recognition is to preferentially bind to compounds in the threotype configuration where the acetylamino group and hydroxyl group are arranged in the trans configuration. This causes the acetyl group of compound 2 to hydrolyze to an amino group, further improving the purity of the diastereomer and optimizing the product yield and purity, thus achieving efficient product conversion.

[0038] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for the synthesis of (2S, 3R)-3-(4-methoxyphenyl)serine, characterized in that: The method comprises the following steps: Step (1): p-methoxybenzaldehyde is added into a tetrahydrofuran solution, glycine is added, and then potassium hydroxide is added in batches to perform a condensation reaction, and a compound 1 is obtained after post-treatment; Step (2): the compound 1 obtained in step (1) is added into water containing a polar solvent, a basic compound and acetic anhydride are added, and the reaction is performed for 3-5 hours, and then drying, filtration and concentration are performed to obtain a compound 2. Step (3): the compound 2 obtained in step (2) is added into water, a lye is added to adjust the pH to 8-9, L-acetylase is added at 40-50°C to react for 24-48h, and the crude product is treated to obtain the compound 3; the route of the production method is as follows: .

2. The method of synthesis of (2S, 3R)-3-(4-methoxyphenyl)serine according to claim 1, characterized by: In step (1), the condensation reaction is performed at a temperature of 10-30 DEG C and under stirring for 12-24 hours.

3. The method of synthesis of (2S, 3R)-3-(4-methoxyphenyl)serine according to claim 1, characterized by: In step (1), the post-treatment comprises adding hydrochloric acid to adjust the pH to 5-6, and then performing filtration, water and ethyl acetate elution and drying.

4. The method of synthesis of (2S, 3R)-3-(4-methoxyphenyl)serine according to claim 1, characterized by: In step (2), the basic compound comprises one or more of sodium carbonate, potassium carbonate, sodium bicarbonate, triethylamine and N, N-diisopropyl ethylamine.

5. The method of synthesis of (2S, 3R)-3-(4-methoxyphenyl)serine according to claim 1, characterized by: In step (2), the polar solvent comprises one or more of dioxane, tetrahydrofuran and N, N-dimethylformamide.

6. The method of synthesizing (2S, 3R)-3-(4-methoxyphenyl)serine according to claim 1, characterized by: In step (3), the L-acetylase accounts for 4%-8% of the mass of the compound 2.

7. The method of synthesis of (2S, 3R)-3-(4-methoxyphenyl)serine according to claim 1, characterized by: In step (3), the crude product treatment step is adding activated carbon under stirring for 1-2 hours, performing filtration, adding hydrochloric acid into the water phase to adjust the pH to 2-3, performing ethyl acetate extraction, concentrating to precipitate a solid, performing filtration and drying to obtain the compound 3.

8. The method of synthesis of (2S, 3R)-3-(4-methoxyphenyl)serine according to claim 1, characterized by: In step (3), the alkali solution is a 1N-2N sodium hydroxide solution.

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