Method for detecting impurities in N-(carbobenzoxy)-L-tyrosine methyl ester reaction process

Abstract

The invention provides a method for detecting impurities in a reaction process of N-(carbobenzoxy)-L-tyrosine methyl ester, which comprises the following steps: in the reaction process of the N-(carbobenzoxy)-L-tyrosine methyl ester, if a plurality of other unknown substances are generated if the feeding proportion, the temperature, the dripping speed and the like are not controlled well, the impurities are detected to be detected; unknown impurities generated in the process have certain influence on the purity of a sample, production equipment can completely remove reaction raw materials or degradation products, but the impurity removal capacity is limited for a small amount of generated impurities which are equivalent to main products in property, and the production equipment can be used for improving the reaction rate, exploring the optimal reaction conditions and monitoring other impurities generated in the reaction process. And performing qualitative analysis on impurities, and performing auxiliary detection by using a high performance chromatography-ultraviolet detection method. The detection method has the advantages of high sensitivity, almost no detection interference, good accuracy, short analysis time and the like, and can effectively overcome the defects in the prior art. The method can be used for detecting the reaction process of N-(carbobenzoxy)-L-tyrosine methyl ester and related substances of the product.

Description

Technical Field

[0001] This invention relates to the field of biodetection technology, specifically to a method for detecting impurities in the reaction process of N-(benzyloxycarbonyl)-L-tyrosine methyl ester. Background Technology

[0002] N-(benzyloxycarbonyl)-L-tyrosine methyl ester (L-Tyrosine, N-[(phenyLmethoxy)carbonyL]-,methyLester) is an organic compound with the chemical formula C 18 H 19 NO5, molecular weight 329.35, CAS: 13512-31-7. It also has the following structural formula:

[0003] .

[0004] The reaction process of N-(benzyloxycarbonyl)-L-tyrosine methyl ester generally uses L-tyrosine methyl ester hydrochloride (Tyr-OMe·HCl) as the starting material, and monitors the reaction progress using thin-layer chromatography (TLC) until the reaction system is free of L-tyrosine methyl ester hydrochloride. However, TLC detection is complex and can only monitor the starting material, not other unknown impurities generated during the reaction or residual organic solvents. These unknown impurities can negatively impact product quality, and production equipment has limited impurity removal capabilities, especially for double-protected impurities, racemic impurities, and condensation impurities with properties similar to the main product, which are difficult to remove. A method is needed to monitor impurity changes throughout the reaction process to adjust reaction conditions promptly, reduce post-processing steps, and minimize solvent extraction. Currently, there is no method for detecting the reaction process or related substances in the main product using high-performance liquid chromatography (HPLC). Therefore, developing an HPLC method for detecting the reaction process is of paramount importance. The starting material for synthesizing N-(benzyloxycarbonyl)-L-tyrosine methyl ester is L-tyrosine methyl ester hydrochloride, which is highly soluble in water. However, the organic solvents added during the reaction and the products formed are poorly soluble in water but highly soluble in organic phases such as chloroform, dichloromethane, ethyl acetate, dimethyl sulfoxide, and acetone. The reaction process is complex and involves many reagents. Therefore, high-performance liquid chromatography (HPLC) detection must consider the starting material, intermediate products, and organic solvents. This invention addresses the shortcomings of existing technologies and, through long-term practical research, has determined a method with high sensitivity, short detection time, and rapid and sensitive detection. Summary of the Invention

[0005] To address the above issues, this invention provides a method for detecting impurities in the reaction process of N-(benzyloxycarbonyl)-L-tyrosine methyl ester, comprising the following steps: (1) Preparation of reference solution: Weigh L-tyrosine methyl ester hydrochloride and N-(benzyloxycarbonyl)-L-tyrosine methyl ester and place them in different volumetric flasks, dissolve them with diluent, make up to volume and shake well; (2) Test solution: The reaction solution is divided into two stages. Stage 1 - starting material L-tyrosine methyl ester hydrochloride has not been completely reacted: Weigh N-(benzyloxycarbonyl)-L-tyrosine methyl ester reaction solution, dissolve it with diluent, make up the volume, shake well, and test it on the instrument. Stage 2 - starting material L-tyrosine methyl ester hydrochloride has been completely reacted: In order to eliminate the interference of benzyl chloroformate residue and degradation products on the peak time of impurities in the reaction solution, add quinoline solution for extraction, add modified MIPs, seal and shake at room temperature for 20 min, filter, dissolve with diluent, make up the volume, shake well, and test it on the instrument. (3) Determination by high performance liquid chromatography: Inject the reference solution into the high performance liquid chromatograph and record the retention time; inject the test solution into the high performance liquid chromatograph, and compare the peak time and peak shape of the test solution chromatogram with the peak time and peak shape of L-tyrosine methyl ester hydrochloride and N-(benzyloxycarbonyl)-L-tyrosine methyl ester in the reference solution chromatogram to determine whether the test solution contains L-tyrosine methyl ester hydrochloride or other impurities, confirm the peak time and peak area of ​​the impurities, and express the content of other impurities in the sample using the area percentage method.

[0006] (4) Preferably, the reaction is ongoing, and the target product is gradually generated in the organic phase. Unknown substances are also gradually generated in the organic phase. During the initial stage 1 of the reaction, the residual L-tyrosine methyl ester hydrochloride is monitored to determine whether unknown substances are generated. The reaction solution needs to be dissolved in a mixture of 0.1%-0.5% TFA solution and acetonitrile (3:7 v / v) to reach a clear state. The solution is then filtered and tested. As the reaction proceeds, the reaction of L-tyrosine methyl ester hydrochloride is basically completed. In stage 2, the impurities generated in the organic phase are detected. The reaction solution is added to a 6-hydroxyquinoline or 2-hydroxyquinoline aqueous solution and shaken vigorously. The mixture is allowed to stand for 30 minutes to separate into layers. The upper organic phase is taken and dissolved in acetonitrile. MIPs are added at the same time. The mixture is sealed and shaken at room temperature for 20 minutes. The mixture is then filtered and tested.

[0007] Preferably, the chromatographic conditions for instrumental detection are as follows: Chromatographic column: Kinete 150mm × 4.6mm, 2.6μm, Phenomenex; Mobile phase: acetonitrile and trifluoroacetic acid, gradient elution, wherein the concentration of trifluoroacetic acid is 0.05-0.2%; Flow rate: 0.5-1 mL / min; Column temperature: 20-30℃; Injection volume: 10µL; Detection wavelength: UV274nm.

[0008] Stage 1: Dissolve in a 0.1% TFA solution and acetonitrile (3:7 v / v) mixed diluent. Stage 2: The reaction of L-tyrosine methyl ester hydrochloride is basically complete. At this point, add 1.0 g / L 6-hydroxyquinoline solution to the reaction solution and shake vigorously to initially eliminate the interference of benzyl chloroformate on the peaks of unknown substances. It reacts with benzyl chloroformate degradation products to form a salt. After standing for 30 minutes to separate the layers, take the upper organic phase and dissolve it in acetonitrile. Simultaneously, add 1 g of modified acrylic MIPs (molecularly imprinted polymers), seal and shake at room temperature for 20 minutes. This substance has specific adsorption sites and adsorbs unknown weakly polar substances such as benzyl chloroformate degradation products or other small molecule reactants generated from the reaction of the raw materials. It also adsorbs hydroxyquinoline and reactants. Impurities have similar polarity to the main peak, are relatively large in molecular weight, do not adsorb, and do not affect the sample's detection. Filter afterwards.

[0009] More preferably, the mobile phase consists of acetonitrile and trifluoroacetic acid with an initial volume ratio of 12:88, using gradient elution, wherein the trifluoroacetic acid solution concentration is 0.1%; the gradient elution ratios are shown in Table 1 below: Table 1

[0010] More preferably, the flow rate is 0.5 mL / min; Column temperature: 30℃; Injection volume: 10µL.

[0011] More preferably, the preparation method of modified acrylic MIPs (Molecularly Imprinted Polymers) is as follows: using anisole or benzyl alcohol as a virtual template, with anisole preferred, to induce the formation of holes that have complementary effects on weakly polar small molecules; using benzyl methacrylate as the main monomer and 4-vinylpyridine as a weakly polar monomer (3:1 v / v) to provide strong hydrophobicity and π-π interaction; adding a high proportion of divinylbenzene as a crosslinking agent to form a highly crosslinked, extremely hydrophobic network, which greatly enhances the affinity for weakly polar aromatic compounds. The template:monomer:crosslinking agent ratio is 0.5-3-40 (molar ratio); then cyclohexane (2.5 times the total monomer (monomer + crosslinking agent)) is added as a porogen / solvent, and the mixture is magnetically stirred for 3 hours to form a template-monomer complex; finally, 2% (molar amount) of azobisisobutyronitrile (AIBN) is added as an initiator for polymerization. In the post-treatment stage, MIPs were eluted with methanol-acetic acid (8:2 v / v), followed by surface hydrophobic modification with trimethylchlorosilane and triethylamine. The addition amount was 1 mL of triethylamine and 2 mL of trimethylchlorosilane per 1 g of MIPs to block residual hydroxyl groups on the surface and reduce non-specific adsorption. MIPs were then soaked in n-hexane for 24 h to adjust the weakly polar pores, ultimately forming a small, highly hydrophobic imprinted site lacking interaction with complex polar groups. Weakly polar small molecules can easily enter and bind tightly, while large molecular raw materials are difficult to enter or bind due to their large size and polarity mismatch. Large molecules have difficulty diffusing into the tight cross-linked network; the polymer surface is extremely hydrophobic and incompatible with the multiple polar functional groups (amides, phenolic hydroxyl groups) on N-(benzyloxycarbonyl)-L-tyrosine methyl ester, resulting in weak binding force and a binding force not comparable to the polarity of N-(benzyloxycarbonyl)-L-tyrosine methyl ester.

[0012] From chromatography Figure 4 The detection method of this invention can rapidly separate L-tyrosine methyl ester hydrochloride, impurities, and the main product. Beneficial effects of this invention: This method effectively solves multiple interference problems in the reaction of N-(benzyloxycarbonyl)-L-tyrosine methyl ester, such as benzyl chloroformate residues, degradation products, and weakly polar small molecule impurities, through staged pretreatment, customized MIPs, and synergistic chromatographic system design. It achieves accurate detection and quantification of unknown impurities throughout the entire reaction process. Compared with existing technologies, it has advantages such as high detection accuracy, thorough interference elimination, strong adaptability, and simple operation. It has significant technical guidance for optimizing the synthesis process of this compound and improving product quality stability, and possesses good patentability and practical application value.

[0013] Stage 1 (starting material not fully reacted): 0.1% TFA-acetonitrile (3:7) diluent was used to precisely match the polarity of the starting material (L-tyrosine methyl ester hydrochloride) to ensure its clear dissolution and avoid masking of early impurity peaks; Phase 2 (After the initial material reaction is completed): Quinoline salt formation and interference removal + MIPs adsorption combined process - 1.0 g / L 6-hydroxyquinoline is reacted with benzyl chloroformate degradation product to form a salt, and strong interfering substances are removed by stratification; then modified MIPs are used to specifically adsorb weakly polar small molecule impurities (degradation products, side reaction small molecules), and do not adsorb the main product (because the main product has many polar functional groups and large size, which do not match the hydrophobic channels and imprinted sites of MIPs), thus eliminating dual interference from the source. Attached Figure Description

[0014] Figure 1 Chromatogram of the reaction solution in stage 2 of Comparative Example 1 without any treatment.

[0015] Figure 2 : Chromatogram of the stage 2 reaction solution treated with only hydroxyquinoline in Example 3.

[0016] Figure 3 Chromatogram of the stage 2 reaction solution after treatment with hydroxyquinoline + MIPs in Example 2.

[0017] Figure 4 Chromatogram of the stage 2 reaction solution in Comparative Example 2, in which general MIPs were used instead of modified MIPs. Detailed Implementation

[0018] The present invention will be better understood through specific examples below. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0019] Example 1: Preparation of MIPs Preparation of modified acrylic MIPs: Anisole was used as a virtual template, benzyl methacrylate and 4-vinylpyridine were used as composite monomers in a 3:1 (v / v) ratio, and divinylbenzene was used as a crosslinking agent. The molar ratio of template:monomer:crosslinking agent was 1.5:3:40. Cyclohexane, with a total monomer volume of 2.5 times, was added, and the mixture was magnetically stirred for 3 h to form a template-monomer complex. Azobisisobutyronitrile (2% of the monomer molar amount) was added, and stirring was continued until completely dissolved. The mixture was heated to 60 °C and polymerized for 24 h to generate MIPs. The polymer blocks were removed, ground in a mortar, sieved, and collected. The polymer was eluted three times with methanol-acetic acid (8:2, v / v) (each eluent volume was 5 times the volume of the MIPs). The eluted MIPs were collected, and 1 mL of triethylamine and 2 mL of trimethylchlorosilane were added, along with an appropriate amount of dried toluene. Under nitrogen protection, the surface was refluxed at 60°C for 10 hours to complete the hydrophobic modification. Finally, the mixture was soaked in n-hexane for 24 hours, filtered, and vacuum dried to obtain the modified MIPs. Static adsorption experiments showed that the IF > 3, which satisfies the adsorption requirements for the degradation products.

[0020] Example 2: Staged detection of unknown impurities in the N-(benzyloxycarbonyl)-L-tyrosine methyl ester reaction process Preparation of reference solution: Weigh 25 mg of L-tyrosine methyl ester hydrochloride and 25 mg of N-(benzyloxycarbonyl)-L-tyrosine methyl ester into two 50 mL volumetric flasks, dissolve and dilute with 0.1% TFA-acetonitrile (3:7, v / v) mixed diluent, shake well to obtain reference solution (concentration of 0.5 mg / mL for both).

[0021] Preparation of test solution: Stage 1 (starting material not fully reacted): Take 1 mL of N-(benzyloxycarbonyl)-L-tyrosine methyl ester reaction solution (L-tyrosine methyl ester hydrochloride residue of about 5%), place it in a 50 mL volumetric flask, dissolve it with the above mixed diluent until clear, filter it through a 0.45 μm organic phase filter membrane, shake well, and obtain the Stage 1 test solution.

[0022] Stage 2 (starting material reaction complete): Take 1 mL of the subsequent reaction solution of the above reaction system (L-tyrosine methyl ester hydrochloride residue ≤0.1%), add 5 mL of 1.0 g / L 6-hydroxyquinoline solution, shake vigorously and let stand for 30 min to separate into layers, take about 1 mL of the upper organic phase and put it into a 25 mL volumetric flask, add 50 mg of the customized MIPs prepared in Example 1, seal and shake at room temperature for 20 min, filter with a 0.45 μm organic phase filter membrane, make up to volume with mixed diluent and shake well to obtain the test solution of Stage 2.

[0023] HPLC detection: Inject 10 μL each of the reference solution and the two-stage test solution into the liquid chromatograph, record the chromatograms and analyze them. The chromatographic conditions are as follows: Chromatographic column: Kinote 150mm × 4.6mm, 2.6μm, Phenomenex.

[0024] Mobile phase: acetonitrile and trifluoroacetic acid in an initial ratio of 12:88, with gradient elution, wherein the trifluoroacetic acid solution concentration was 0.1%; the gradient elution ratios are as follows: Table 2

[0025] like Figure 3 As shown, in the test sample of Stage 1, the resolution between the L-tyrosine methyl ester hydrochloride peak and the adjacent impurity peak was 2.3, with no interfering peaks and a quantitative relative error of 3.1%. This method can meet the requirements for the detection of raw materials. In the test sample of Stage 2, the main product peak was symmetrical, and three unknown weakly polar impurities were detected. The resolution between each impurity and the main product was ≥2.0. The elimination rate of the interfering peak of benzyl chloroformate degradation product was 100%, and the quantitative relative error of impurities was ≤4.5%. This method has high selectivity and good precision, and can effectively monitor the changes in the impurity spectrum during the reaction process, providing solid data support for process optimization.

[0026] Comparative Example 1: Single preprocessing method (no stages) The two-stage reaction solution was diluted with a 0.1% TFA-acetonitrile (3:7, v / v) mixed solvent. In stage 2, no 6-hydroxyquinoline extraction or MIPs adsorption was added; all other conditions were the same as in Example 2. 1 mL of each stage reaction solution was taken, diluted to volume with a 0.1% TFA-acetonitrile (3:7, v / v) mixed diluent, filtered, and then analyzed by HPLC.

[0027] like Figure 1 As shown, the peak shape of L-tyrosine methyl ester hydrochloride in the test sample of stage 1 was normal, but the peak of benzyl chloroformate degradation product appeared in the test sample of stage 2, which overlapped with the unknown impurity peak generated by the actual reaction. The resolution was only 0.5, and the impurity could not be accurately quantified. The number of impurities detected was only one before the main peak, and the relative error of quantification reached 12.3%, which could not meet the detection requirements.

[0028] Example 3, Stage 2: Quinoline-free extraction treatment In the preparation of the test sample in Stage 2, no 6-hydroxyquinoline solution was added for extraction. The other conditions were the same as in Example 2. Take 1 mL of the reaction solution in Stage 2, replace the 6-hydroxyquinoline solution with sodium hydroxide solution, shake vigorously, let stand for 30 min to separate the layers, take 1 mL of the upper organic phase directly, add customized MIPs, shake, filter, make up to volume and then detect.

[0029] like Figure 2 As shown, the spectrum also has obvious continuous peaks, which may be degradation products of benzyl chloroformate. These peaks partially overlap with one of the unknown impurity peaks. The interference peak elimination rate is only 65%, and the relative error of impurity quantification reaches 8.7%, making accurate quantification impossible.

[0030] Comparative Example 2 uses general MIPs In Stage 2, during the preparation of the test sample, general-purpose weakly polar MIPs (without surface hydrophobic modification, methyl methacrylate as the monomer, toluene as the template, and divinylbenzene as the crosslinking agent, with a template:monomer:crosslinking agent molar ratio of 1.5:3:40) were used. Cyclohexane, at 2.5 times the total monomer volume, was used as a porogen / solvent. The mixture was magnetically stirred for 3 hours to form a template-monomer complex. Then, 2% of the monomer molar amount of azobisisobutyronitrile was added as an initiator for polymerization. In the post-treatment stage, the MIPs were eluted with methanol-acetic acid (8:2 v / v) and soaked in n-hexane for 24 hours. This replaced the modified MIPs of Example 1, with the other conditions the same as in Example 2.

[0031] like Figure 4 As shown, general MIPs have poor adsorption specificity for weakly polar impurities and adsorb some of the main product, resulting in an 8.2% loss of the main product peak area; the impurities are not completely adsorbed, and there are still trace interference peaks remaining. The relative error of impurity quantification is 9.1%, and the resolution drops to 1.8.

[0032] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations; therefore, any obvious variations or modifications derived therefrom remain within the scope of protection of this invention.

Claims

1. A method for detecting impurities in the reaction process of N-(benzyloxycarbonyl)-L-tyrosine methyl ester, comprising the following steps: (1) Preparation of reference solution: Weigh L-tyrosine methyl ester hydrochloride and N-(benzyloxycarbonyl)-L-tyrosine methyl ester and place them in different volumetric flasks, dissolve them with diluent, make up to volume and shake well; (2) Test solution: a reaction solution in two stages. Stage 1 - Incomplete reaction of starting material L-tyrosine methyl ester hydrochloride: Weigh N-(benzyloxycarbonyl)-L-tyrosine methyl ester reaction solution, dissolve in diluent, make up to volume, shake well, and test on the instrument; Phase 2 - Starting material L-tyrosine methyl ester hydrochloride has been completely reacted: In order to eliminate the interference of benzyl chloroformate residue and degradation products on the peak time of impurities in the reaction solution, quinoline solution was added for extraction, followed by the addition of modified MIPs, sealed and shaken at room temperature, filtered, dissolved with diluent, diluted to volume, shaken well, and tested on the instrument. (3) Determination by high performance liquid chromatography: Inject the reference solution into the high performance liquid chromatograph and record the retention time; Inject the test solution into the high-performance liquid chromatograph. Compare the peak time and peak shape of the test solution chromatogram with the peak time and peak shape of L-tyrosine methyl ester hydrochloride and N-(benzyloxycarbonyl)-L-tyrosine methyl ester in the reference solution chromatogram to determine whether the test solution contains L-tyrosine methyl ester hydrochloride or other impurities. Confirm the peak time and peak area of ​​the impurities, and express the content of other impurities using the area percentage method.

2. The method for detecting impurities in the reaction process of N-(benzyloxycarbonyl)-L-tyrosine methyl ester according to claim 1, characterized in that: Phase 1: Monitor L-tyrosine methyl ester hydrochloride residues to determine if any unknown substances are generated. Dissolve the unknown substances in the reaction solution using a mixture of 0.1%-0.5% TFA solution and acetonitrile as a diluent until the solution is clear, filter, and then analyze the solution. In stage 2, to detect impurities generated in the organic phase, the reaction solution was added to a 0.5-1.0 g / L solution of 6-hydroxyquinoline or 2-hydroxyquinoline and shaken vigorously. After standing and separating into layers, the upper organic phase was taken and dissolved in acetonitrile. MIPs were added at the same time, and the mixture was sealed and shaken at room temperature. After filtration, the mixture was analyzed by the instrument.

3. The method for detecting impurities in the reaction process of N-(benzyloxycarbonyl)-L-tyrosine methyl ester according to claim 2, characterized in that, The chromatographic conditions for instrumental analysis are as follows: Chromatographic column: Kinete 150mm × 4.6mm, 2.6μm, Phenomenex; Mobile phase: acetonitrile and trifluoroacetic acid, gradient elution, wherein the concentration of trifluoroacetic acid is 0.05-0.2%; Flow rate: 0.5-1 mL / min; Column temperature: 20-30℃; Injection volume: 10µL; Detection wavelength: UV274nm.

4. The method for detecting impurities in the reaction process of N-(benzyloxycarbonyl)-L-tyrosine methyl ester according to claim 3, characterized in that, Mobile phase: Acetonitrile and trifluoroacetic acid with an initial volume ratio of 12:88, gradient elution, wherein the concentration of trifluoroacetic acid solution was 0.1%; the gradient elution ratios are shown in Table 1 below: Table 1 。 5. The method for detecting impurities in the reaction process of N-(benzyloxycarbonyl)-L-tyrosine methyl ester according to claim 3, characterized in that: Flow rate: 0.5 mL / min; Column temperature: 30℃; Injection volume: 10µL.

6. The method for detecting impurities in the reaction process of N-(benzyloxycarbonyl)-L-tyrosine methyl ester according to claim 2, characterized in that, The preparation method of modified acrylic MIPs includes the following steps: S1: A virtual template is mixed with a mixture of benzyl methacrylate and 4-vinylpyridine monomers, and a crosslinking agent, divinylbenzene, is added. The mixture is then magnetically stirred at room temperature, followed by the addition of a porogen and magnetic stirring to form a template-monomer complex. Azobisisobutyronitrile is then added as an initiator, and the mixture is heated to polymerize and produce MIPs. S2: MIPs were eluted with methanol-acetic acid, and then surface-hydrophobicated with trimethylchlorosilane and triethylamine; finally, MIPs were soaked in n-hexane to obtain modified MIPs.

7. The method for detecting impurities in the reaction process of N-(benzyloxycarbonyl)-L-tyrosine methyl ester according to claim 6, characterized in that, In step S1, the virtual template is anisole or benzyl alcohol, preferably anisole, and the molar ratio of virtual template:monomer:crosslinking agent is (0.5-1.5):(2.5-3.5):(35-45); the volume ratio of benzyl methacrylate to 4-vinylpyridine is (2-4):1, and the temperature is raised to 55-65℃ for polymerization for 22-26 hours.

8. The method for detecting impurities in the reaction process of N-(benzyloxycarbonyl)-L-tyrosine methyl ester according to claim 7, characterized in that, In step S1, the virtual template is anisole or benzyl alcohol, preferably anisole, and the molar ratio of virtual template:monomer:crosslinking agent is 0.5:3:40; the volume ratio of benzyl methacrylate to 4-vinylpyridine is 3:1, and the temperature is raised to 60°C for polymerization for 24 hours.

9. The method for detecting impurities in the reaction process of N-(benzyloxycarbonyl)-L-tyrosine methyl ester according to claim 8, characterized in that, In step S1, the volume of the porogen is 2.5-3 times the volume of the monomer and crosslinking agent mixture, the porogen is cyclohexane, and the amount of azobisisobutyronitrile added is 1.5-2.5% of the molar amount of the monomer.

10. The method for detecting impurities in the reaction process of N-(benzyloxycarbonyl)-L-tyrosine methyl ester according to claim 9, characterized in that, In step S2, the volume ratio of methanol to acetic acid is 8-9:1.5-2.5, and the solid-liquid ratio of MIPs to trimethylchlorosilane and triethylamine is 1:1:2 (g / mL / mL).

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