Synthesis method of semeglutide side chain intermediate

Abstract

The invention discloses a synthesis method of a semeglutide side chain intermediate, and belongs to the technical field of chemical synthesis processes. The synthesis method comprises the following steps: 1) weighing a compound 1, adding an aprotic polar solvent, NMM and Fmoc-Lys-OH, and reacting to obtain a compound 2; 2) weighing trifluoroacetic acid and the compound 2 for reaction to obtain a compound 3; 3) weighing the compound 1, adding an aprotic polar solvent, NMM and a compound 3, and reacting to obtain a compound 4; 4) weighing trifluoroacetic acid and the compound 4 for reaction to obtain a compound 5; and 5) weighing active ester to react with the compound 5 to obtain the semeglutide fat side chain intermediate. According to the method, the high-activity mixed anhydride and the amine are subjected to condensation reaction, so that the synthesis efficiency is improved, the product purity is improved, the production cost is reduced, and the method is of great significance to large-scale production, contributes to the development of the field of biological medicines and brings economic benefits to enterprises.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis process, and particularly relates to the synthesis of a semaglutide side chain intermediate. Background Art

[0002] Semaglutide is a polypeptide with 31 amino acids in the main chain. The structural formula of semaglutide is as follows: Figure 1 As shown. Semaglutide is a drug developed by Novo Nordisk of Denmark, designed for patients with type 2 diabetes. The pathological characteristic of type 2 diabetes is the reduced ability of pancreatic islet cells to respond to insulin. Glucagon-like peptide-1 (GLP-1) receptor agonists are a hot topic in the research of hypoglycemic drugs, and Semaglutide, as a leader among them, has significant therapeutic effects.

[0003] Semaglutide is similar to GLP-1 and has advantages in the treatment of type 2 diabetes. It is a long-acting preparation that is injected once a week and can lower blood sugar and assist in weight loss. Studies have shown that Semaglutide can improve insulin resistance, activate GLP-1 receptors, promote pancreatic beta cell proliferation and differentiation, increase insulin secretion, inhibit glucagon secretion, and reduce the risk of cardiovascular disease.

[0004] In the synthesis process of semaglutide, in addition to the use of conventional amino acids or protected amino acids, a large amount of key intermediates containing fatty chains, Fmoc-L-Lys[Oct-(OtBu)-Glu-(OtBu)-AEEA-AEEA]-OH (molecular formula C 64 H 101 N5O 16 , molecular weight 1196.53, Chinese name: fluorenylmethoxycarbonyl-L-lysyl[octyl-(O-tert-butyl)-glutamyl-(O-tert-butyl)-AEEA-AEEA]-OH). As an indispensable raw material, the supply of this compound in the market mainly depends on direct aminocarboxyl condensation or active ester synthesis. In addition to conventional protected amino acids, these synthesis methods also require the use of a large amount of expensive condensation agents and catalysts. The process is complicated and requires high operator quality and production equipment. Therefore, the market supply of this type of product is insufficient and the selling price is high, which in turn pushes up the synthesis cost of semaglutide.

[0005] Among them, the active ester method is characterized by the intermediates it generates being both stable and highly reactive, making it an excellent choice for the synthesis of complex peptides or systems that require long-term reactions. This method allows for the separation, purification, and storage of intermediates, providing greater flexibility for experiments. However, the active ester method has relatively low reactivity, which may result in a slow reaction rate and significant stereochemical effects. In a solution system, long-term presence of carboxyl-activated polypeptide chains may lead to racemization, which in turn affects the purity and activity of the product.

[0006] In contrast, the aminocarboxylic acid condensation method (mixed anhydride method as the core technology of aminocarboxylic acid condensation) is known for its advantages of simple operation, fast reaction speed and easy access to high-purity peptides. Especially in situations where high-purity peptides need to be synthesized quickly, the mixed anhydride method shows excellent performance. In addition, the preparation of chloroformate reagents is relatively convenient and low-cost, which makes the mixed anhydride method have significant economic advantages in the large-scale preparation of peptides. However, the high activity of mixed anhydrides leads to their poor stability, so the reaction must be carried out under strict low-temperature and anhydrous conditions. At the same time, by-products may be produced when mixed anhydrides react with amino components, which increases the difficulty of product purification. Summary of the invention

[0007] In view of the defects existing in the above-mentioned prior art, in order to solve the problem that the synthesis process of the intermediate Fmoc-L-Lys[Oct-(OtBu)-Glu-(OtBu)-AEEA-AEEA]-OH is complicated and expensive, the purpose of the present invention is to design and provide a new mixed anhydride method for synthesizing semaglutide side chain intermediates. The present invention adopts a mixed anhydride method combined with a partially active ester method, and has multiple advantages in the process of preparing the key intermediate of semaglutide, such as high reaction activity, short reaction time, and low raw material price. The method of the present invention optimizes the reaction process, improves the synthesis efficiency, and solves the problems of slow reaction speed (the activated ester method often requires overnight reaction, while the synthesis reaction of the present application is completed within one hour), low purity (the byproducts in the activated ester method need recrystallization to be removed, while the byproducts of the present application can be removed by simple phase extraction), low yield (the total yield of the activated ester method is ≤45, while the total yield of the present application is ≥50) and high production cost (the activated ester method requires a relatively expensive condensing agent, and the main reagents of the present application are NMM and chloroformate, which has obvious cost advantages) in the traditional method. The method shows significant advantages of high efficiency, environmental protection and low cost in the field of drug synthesis, and provides new ideas and means for drug research and development.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] In one aspect, the present invention provides a method for synthesizing a semaglutide side chain intermediate, comprising the following steps:

[0010] (1) Weighing compound 1, adding a non-protonic polar solvent, NMM and Fmoc-Lys-OH, and performing a condensation reaction to obtain compound 2;

[0011] (2) weighing trifluoroacetic acid and compound 2 to carry out a deprotection reaction to obtain compound 3;

[0012] (3) Weighing compound 1, adding a non-protonic polar solvent, NMM and compound 3, and performing a condensation reaction to obtain compound 4;

[0013] (4) weighing trifluoroacetic acid and compound 4 to carry out a deprotection reaction to obtain compound 5;

[0014] (5) Weigh the active ester and carry out condensation reaction with compound 5 to obtain Fmoc-L-Lys[Oct-(OtBu)-Glu-(OtBu)-AEEA-AEEA]-OH.

[0015] Wherein, the structural formula of compound 1 is shown in the following formula I:

[0016]

[0017] The structural formula of compound 2 is shown in Formula II below:

[0018]

[0019] The structural formula of compound 3 is shown in the following formula III:

[0020]

[0021] The structural formula of compound 4 is shown in Formula IV below:

[0022]

[0023] The structural formula of compound 5 is shown in Formula V below:

[0024]

[0025] The structural formula of the active ester is one of the following:

[0026]

[0027] Preferably, the active ester has the structural formula shown in Formula VI:

[0028]

[0029] The structural formula of Fmoc-L-Lys[Oct-(OtBu)-Glu-(OtBu)-AEEA-AEEA]-OH is shown in the following formula VII:

[0030]

[0031] The synthetic method specifically comprises the following steps:

[0032] (1) Compound 1 is dissolved by adding a non-protonic polar solvent under argon, the temperature is lowered, NMM is added, the mixture is cooled, chloroformate is added dropwise, a pre-cooled DMF solution of Fmoc-Lys-OH is added dropwise, the mixture is stirred for reaction, separated, and dried to obtain Compound 2;

[0033] The method for preparing the precooled Fmoc-Lys-OH DMF solution is as follows: weighing Fmoc-Lys-OH and dissolving it in a non-protonic polar solvent solution, adding NMM, shaking to dry, and freezing to obtain;

[0034] (2) trifluoroacetic acid was added slowly to compound 2 under continuous stirring to react, and then added to alkaline water with stirring, centrifuged, and dried to obtain compound 3;

[0035] (3) Compound 1 was dissolved by adding a non-protonic polar solvent under argon, the temperature was lowered, NMM was added, the mixture was cooled, chloroformate was added dropwise, and a pre-cooled DMF solution of compound 3 was added dropwise, the mixture was stirred to react, separated, and dried to obtain compound 4;

[0036] The method for preparing the pre-cooled DMF solution of compound 3 is as follows: weighing compound 3, dissolving it in a non-protonic polar solvent solution, stirring to dryness, and freezing to obtain;

[0037] (4) trifluoroacetic acid was added to compound 4 slowly under continuous stirring to react, and then added to alkaline water with stirring, centrifuged, and dried to obtain compound 5;

[0038] (5) Compound 5 was taken, NaHCO3 was added in batches, the pH was adjusted to neutral, and then an amount of NaHCO3 equivalent to compound 5 was added, stirred to dissolve, and an ethanol solution of an active ester was added dropwise, and the reaction was carried out at room temperature. After the reaction was completed, purification was performed to obtain the semaglutide side chain intermediate Fmoc-L-Lys[Oct-(OtBu)-Glu-(OtBu)-AEEA-AEEA]-OH.

[0039] In the synthesis method, the chloroformate in step (1) is selected from at least one of ethyl chloroformate, isopropyl chloroformate, n-butyl chloroformate or isobutyl chloroformate;

[0040] The aprotic polar solvent is an organic solvent.

[0041] The aprotic polar solvent is dimethylformamide (DMF), acetonitrile (MCN), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), hexamethylphosphoric acid triamide (HMPA).

[0042] In the synthesis method, the reaction temperature in step (1) is -20°C ± 2°C;

[0043] The molar and volume ratio of the compound 1, the aprotic polar solvent, NMM and Fmoc-Lys-OH ( 3.8～3.9 )mol:( 3～ 4)L: (940~1000)mL: (7.36~7.50)mol;

[0044] The equivalent of the chloroformate is 1.05-1.5, which not only ensures the smooth progress of the reaction, but also avoids the waste of resources.

[0045] In the synthesis method, the reaction temperature in step (2) is 10° C. to 20° C.;

[0046] The mass volume ratio of the trifluoroacetic acid to compound 2 is (3.0-3.3) L: (3-3.6) kg.

[0047] In the synthesis method, the reaction temperature in step (3) is -20°C ± 2°C;

[0048] The mass volume ratio of the compound 1, the aprotic polar solvent, NMM and the compound 3 is 1.69 kg: (3.34-4.00) L: (720-750) mL: (3.7-3.8) kg.

[0049] In the synthesis method, the reaction temperature in step (4) is 10-15°C;

[0050] The mass volume ratio of the trifluoroacetic acid to compound 4 is (3.30-3.50) L: (4.4-4.5) kg.

[0051] In the synthesis method, the molar ratio of compound 5 to active ester in step (5) is 1:1.

[0052] In a second aspect, the present invention discloses the use of any of the methods described in the foregoing in the synthesis of semaglutide side chain intermediates or semaglutide.

[0053] The method for synthesizing the semaglutide side chain of the present invention adopts a mixed anhydride method as the core technology of aminocarboxyl condensation, and combines with a partial active ester method to achieve efficient synthesis of the target compound. The method uses chemical raw materials conventionally supplied in the market as raw materials, ensuring reasonable cost control. During the reaction process, an anhydrous non-protonic polar solvent is used as a reaction medium to increase the reaction rate and ensure product purity; the reaction temperature is precisely controlled to ensure that the activity and stability of the reactants reach the optimal state.

[0054] After the condensation reaction of the present invention is completed, the reaction is quenched by dilute alkaline water to remove excess reactants. Subsequently, an organic solvent is used for extraction to effectively separate the product from the reaction system. Then, after drying, concentration and appropriate solvent recrystallization, a purified product with high purity is obtained. In the subsequent deprotection agent treatment process, the amino compound intermediate is successfully prepared. After concentration, appropriate solvent recrystallization and vacuum drying, a high-quality amine salt is obtained. Through two rounds of condensation reactions, the ammonium salt and the single active ester of the higher fatty acid are condensed under the catalytic action of the base to form the target product. Finally, the product is preliminarily purified by methods such as phase extraction and silica gel flash crude purification. Subsequently, the compound is deeply purified by a salt conversion process to finally obtain a high-purity target compound. This method not only improves the synthesis efficiency, but also optimizes the product purity, providing strong technical support for drug research and development and production.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] The mixed anhydride method of the present invention utilizes a high-activity mixed anhydride and an amine to carry out a condensation reaction, quickly completes the synthesis, improves production efficiency, and simultaneously improves product purity. In terms of synthesizing the fat-linked side chain of semaglutide, the method can effectively improve product quality and yield, overcoming the shortcomings of traditional methods.

[0057] The method of the present invention can significantly reduce production costs, thereby expanding manufacturing capacity and improving product quality; it provides a more economical and sufficient key intermediate for the synthesis of semaglutide, effectively reduces the production cost of semaglutide and improves its production capacity. The method of the present invention is easy to promote and apply, can provide the market with more sufficient drugs to meet the urgent needs of the majority of patients, and make positive contributions to human health. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a schematic diagram of the peptide sequence contained in the main chain of semaglutide;

[0059] Figure 2 The synthetic route of Fmoc-L-Lys[Oct-(OtBu)-Glu-(OtBu)-AEEA-AEEA]-OH;

[0060] Figure 3 This is the HPLC detection spectrum of the crude semaglutide side chain;

[0061] Figure 4 This is the HPLC detection spectrum of the crude semaglutide side chain after purification by column chromatography. DETAILED DESCRIPTION

[0062] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0063] Example 1: Synthesis of Fmoc-L-Lys[Oct-(OtBu)-Glu-(OtBu)-AEEA-AEEA]-OH

[0064] The synthetic route of Fmoc-L-Lys[Oct-(OtBu)-Glu-(OtBu)-AEEA-AEEA]-OH of the present invention is as follows: Figure 2 shown.

[0065] 1. Synthesis of Compound 2

[0066] The specific synthesis process of compound 2 is as follows:

[0067]

[0068] (1) 2.71 kg of ground Fmoc-Lys-OH (Fmoc-lysine, 7.36 mol) was dissolved in 3.5 L of anhydrous DMF, and 200 g of anhydrous sodium sulfate and 1.23 L of NMM (nitromethylmorpholine, 1.2 eq) were added. The mixture was shaken to dryness for 10 minutes, and the bottle was sealed and placed in a freezer for later use.

[0069] (2) Weigh 1.01 kg of Boc-AEEA-OH (compound 1, 3.83 mol, 1.02 eq) and add it to a 20 L double-layer glass reactor. Equip it with a temperature probe and a constant pressure funnel. Fill the reactor with argon gas and add 3.5 L of anhydrous DMF (dimethylformamide). Start mechanical stirring (speed 600-700) to dissolve. Open the coolant valve to cool the solution in the reactor to 0 °C and add 940 mL NMM (1.1eq), the reaction solution is further cooled to -18°C under argon protection (during the cooling process, the bottle and the argon bag must always be kept unobstructed to prevent the negative pressure in the bottle from causing moisture or oxygen to invade and affect the reaction), close the coolant valve, and use a 1000mL constant pressure funnel to drop 1100mL of isobutyl chloroformate SJF (25.6mol, 1.1eq), plug the top of the constant pressure funnel, carefully open the piston of the constant pressure funnel, control at 100-120 drops / min, maintain the temperature at -17±2°C, and add it within 35±5 minutes. After the dropwise addition is completed, ensure that the temperature of the reaction solution is -18±3°C. Rinse the constant pressure funnel with 100mL of anhydrous DMF and add all of it to the reactor. Stir the reaction for 18 minutes. Close the piston of the constant pressure funnel, add the DMF solution of Fmoc-Lys-OH pre-cooled in the freezer to the constant pressure funnel (be careful not to pour the desiccant, wash the desiccant at the bottom of the bottle with 100mL DMF and carefully add the supernatant), carefully open the piston of the constant pressure funnel and slowly drip into the reaction bottle, and control the dripping speed to make the temperature of the reaction liquid below -8°C. After the dripping is completed, rinse the constant pressure funnel containing the Fmoc-Lys-OH DMF solution with 100mL of anhydrous DMF, add the washing liquid to the reaction liquid, continue to stir the reaction at about -8±5°C for 4 hours, close the cold bath, continue to stir (speed 500~550), and react until the reaction is complete as detected by TLC or HPLC.

[0070] Note: TLC detection conditions: PE:EA=1:1. Slowly add the reaction solution into 50L 5% ammonia solution (5kg crushed ice, 5Kg sodium chloride, continuous and effective stirring) to precipitate fine powder solid, and centrifuge for 20 minutes. The mother liquor is placed in a designated container for disposal, and the filter cake is washed with water until neutral. Then put it into 20L 3% dilute hydrochloric acid (3kg crushed ice, 2Kg sodium chloride), stir for 2 minutes, and centrifuge. Wash the filter cake with water until neutral, and centrifuge for 20 minutes. Spread the filter cake on a stainless steel plate, put it into an oven and dry it at 45°C for 12 hours, until the loss on drying is less than 2%, and then package it for storage. The mother liquor is discarded.

[0071] 2. Synthesis of Compound 3

[0072] The specific synthesis process of compound 3 is as follows:

[0073]

[0074] Add 3.30L TFA (trifluoroacetic acid) to a 20L glass reactor, open the coolant valve to maintain the temperature in the reactor at 10-15°C. Slowly add 3.59kg (5.84mol) of ground compound 2 under continuous stirring. During this process, the temperature of the reaction liquid should be around 20°C. After vigorous stirring to completely dissolve the solid matter, use TLC to detect the completion of the reaction. Place a stainless steel barrel on a well-ventilated operating table, set up a mechanical stirrer, then add 30L 5% ammonia solution (147.0mol) and 6kg salt and 5kg crushed ice to the barrel, and slowly add the TFA solution containing compound 3 to the alkaline water in the stainless steel barrel under vigorous stirring. After adding, rinse the reactor with a small amount (100-300mL) of glacial acetic acid, pour the reactor washing liquid into the stainless steel barrel and stir for 5 minutes. Centrifuge, wash the filter cake with water until neutral, spread out and dry (45°C) until the drying loss is less than 0.5%. Compound 3 is obtained.

[0075] 3. Synthesis of compound 4

[0076] The specific synthesis process of compound 4 is as follows:

[0077]

[0078] (1) 3.74 kg of compound 3 (powdered solid) was dissolved in 3.34 L of dry DMF, 200 g of anhydrous sodium sulfate was added, stirred and dried for ten minutes, the bottle was tightly stoppered, and placed in a refrigerator for later use. TLC detection conditions: PE:EA = 1:1 or DCM:MOH = 20:1.

[0079] (2) Weigh 1.69 kg of compound 1 (1.07 eq) and add it to a 20 L glass jacketed reactor. Equip it with a temperature probe and a constant pressure funnel. Fill the reactor with argon. Add 3.34 L of anhydrous DMF and start stirring with the stirrer (speed 600-700). Turn on the coolant switch to cool the solution in the reactor to 0 °C. After adding 720 mL of NMM (1.09 eq), the reaction solution is cooled under argon protection (during the cooling process, always ensure that the bottle and the argon bag are unobstructed to prevent negative pressure in the bottle). When the temperature reaches -18±3℃, turn off the coolant switch, add 850mL of isobutyl chloroformate (1.08eq) with a 1000mL constant pressure funnel, plug the top of the constant pressure funnel, carefully open the piston of the constant pressure funnel, and slowly drip isobutyl chloroformate into the reaction bottle. The dripping speed is controlled at 120-180 drops / min, and the addition is completed within 30±2 minutes to ensure that the reaction liquid temperature is -17±3℃. After the dripping is completed, ensure that the reaction liquid temperature is -18±2℃. Rinse the constant pressure funnel with 100mL of anhydrous DMF and add all of it to the reactor. Continue stirring and reacting for 20 minutes, add the DMF solution of compound 3 precooled in the refrigerator to the constant pressure funnel and drip it into the reaction liquid, the temperature is not higher than -8℃. After the dripping is completed, rinse the container containing the DMF solution of compound 3 and the constant pressure funnel with 100mL of anhydrous DMF, and add all of the washing liquid to the reaction liquid. Continue stirring the reaction at -18±2°C for 4 hours, then close the coolant valve and continue stirring (speed 500-550) until the reaction is complete as detected by TLC or HPLC. TLC detection conditions: PE:EA=1:1.

[0080] Add the reaction solution into a stainless steel barrel containing 90L of 10% salt water (stir well), precipitate solids, and centrifuge. The mother liquor is placed in a designated container and discarded, and the filter cake is washed with water until it is neutral. Then put the combined filter cake into 20L of 5% hydrochloric acid solution cooled with 3kg of crushed ice and 2kg of sodium chloride, stir and wash for 2 minutes, and immediately centrifuge and dehydrate. The filter cake is washed with water until it is neutral. Then put it into 20L of 5% ammonia water cooled with 5kg of crushed ice, stir for 3 minutes, and immediately centrifuge and dehydrate. Wash the filter cake with water until it is neutral. Centrifuge and dehydrate for 20 minutes. Spread and dry (45°C, 12 hours) until the loss on drying is less than 2%. Package and store. The centrifuged mother liquor is discarded.

[0081] 4. Synthesis of Compound 5

[0082] The specific process of the synthesis of compound 5 is as follows:

[0083]

[0084] Add 3.30L TFA (trifluoroacetic acid) to a 20L glass reactor, open the coolant valve to maintain the temperature in the reactor at 10-15°C. Slowly add 4.43kg (5.84mol) of ground compound 4 under continuous stirring. During this process, the temperature of the reaction liquid should be around 20°C. After vigorous stirring to completely dissolve the solid matter, use TLC to detect the completion of the reaction. Place a stainless steel barrel on a well-ventilated operating table, set up a mechanical stirrer, then add 30L 5% ammonia solution (147.0mol) and 6kg salt and 5kg crushed ice to the barrel, and slowly add the TFA solution containing compound 3 to the alkaline water in the stainless steel barrel under vigorous stirring. After adding, rinse the reactor with a small amount (100-300mL) of glacial acetic acid, pour the reactor washing liquid into the stainless steel barrel and stir for 5 minutes. Centrifuge, wash the filter cake with water until neutral, spread out and dry (45°C) until the drying loss is less than 0.5%, and obtain compound 5.

[0085] 5. Synthesis of the target compound Fmoc-L-Lys[Oct-(OtBu)-Glu-(OtBu)-AEEA-AEEA]-OH

[0086] The specific process of synthesis of the target compound Fmoc-L-Lys[Oct-(OtBu)-Glu-(OtBu)-AEEA-AEEA]-OH is as follows:

[0087]

[0088] Among them, compound 8 is an active ester purchased from outside, and its structural formula is shown in the following formula VI:

[0089]

[0090] In a reaction kettle equipped with a thermometer and mechanical stirring, add 10L of water, add 1.3kg of compound 5, stir evenly, add NaHCO3, adjust the pH to 7, add 0.34kg of NaHCO3, stir to dissolve, drop 1.3kg of compound 8 dissolved in 10L of ethanol, and start the reaction at room temperature. After reacting for 2h, the reaction is completed, adjust the pH to 7 with 10% phosphoric acid, remove the ethanol by rotary evaporation, and then adjust the pH to 3. Extract with 10L of ethyl acetate, let stand and stratify, take the organic phase, wash with an appropriate amount of saturated brine, let stand and stratify, take the organic phase, dry with anhydrous sodium sulfate, and concentrate to obtain the target compound Fmoc-L-Lys[Oct-(OtBu)-Glu-(OtBu)-AEEA-AEEA]-OH. The purity of the target compound is calculated by the area normalization method, such as Figure 3 The results showed that the purity of the crude product at the end of the synthesis was 88% according to the area normalization analysis of the HPLC analysis spectrum.

[0091] The product after purification was analyzed by HPLC, and the results were as follows Figure 4 As shown, the area normalized assay purity of the product (soap-like solid) was 98.8%.

Claims

1. A method for synthesizing a semaglutide side chain intermediate, characterized in that: The following steps are involved: (1) Weighing compound 1, adding a non-protonic polar solvent, NMM and Fmoc-Lys-OH, and performing a condensation reaction to obtain compound 2; (2) weighing trifluoroacetic acid and compound 2 to carry out a deprotection reaction to obtain compound 3; (3) Weighing compound 1, adding a non-protonic polar solvent, NMM and compound 3, and performing a condensation reaction to obtain compound 4; (4) weighing trifluoroacetic acid and compound 4 to carry out a deprotection reaction to obtain compound 5; (5) Weighing an active ester and subjecting it to a condensation reaction with compound 5 to obtain Fmoc-L-Lys[Oct-(OtBu)-Glu-(OtBu)-AEEA-AEEA]-OH; Wherein, the structural formula of compound 1 is shown in the following formula I: The structural formula of compound 2 is shown in Formula II below: The structural formula of compound 3 is shown in the following formula III: The structural formula of compound 4 is shown in Formula IV below: The structural formula of compound 5 is shown in Formula V below: The active ester has the following structural formula: Preferably, the active ester has the structural formula shown in Formula VI: The structural formula of Fmoc-L-Lys[Oct-(OtBu)-Glu-(OtBu)-AEEA-AEEA]-OH is shown in the following formula VII:

2. The synthesis method according to claim 1, characterized in that The specific steps include: (1) Compound 1 is dissolved by adding a non-protonic polar solvent under argon, the temperature is lowered, NMM is added, the mixture is cooled, chloroformate is added dropwise, a pre-cooled DMF solution of Fmoc-Lys-OH is added dropwise, the mixture is stirred for reaction, separated, and dried to obtain Compound 2; (2) trifluoroacetic acid was added slowly to compound 2 under continuous stirring to react, and then added to alkaline water with stirring, centrifuged, and dried to obtain compound 3; (3) Compound 1 was dissolved by adding a non-protonic polar solvent under argon, the temperature was lowered, NMM was added, the mixture was cooled, chloroformate was added dropwise, and a pre-cooled DMF solution of compound 3 was added dropwise, the mixture was stirred to react, separated, and dried to obtain compound 4; The method for preparing the pre-cooled DMF solution of compound 3 is as follows: weighing compound 3, dissolving it in a non-protonic polar solvent solution, stirring to dryness, and freezing to obtain; (4) trifluoroacetic acid was added to compound 4 slowly under continuous stirring to react, and then added to alkaline water with stirring, centrifuged, and dried to obtain compound 5; (5) Compound 5 was taken, NaHCO3 was added in batches, the pH was adjusted to neutral, and then an amount of NaHCO3 equivalent to compound 5 was added, stirred to dissolve, and an ethanol solution of an active ester was added dropwise, and the reaction was carried out at room temperature. After the reaction was completed, purification was performed to obtain the semaglutide side chain intermediate Fmoc-L-Lys[Oct-(OtBu)-Glu-(OtBu)-AEEA-AEEA]-OH.

3. The synthesis method according to claim 2, characterized in that The chloroformate in step (1) is selected from at least one of ethyl chloroformate, isopropyl chloroformate, n-butyl chloroformate or isobutyl chloroformate; The aprotic polar solvent is an organic solvent.

4. The synthesis method according to claim 3, characterized in that The aprotic polar solvent is one of dimethylformamide, acetonitrile, dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran or hexamethylphosphoric triamide.

5. The synthesis method according to claim 2, characterized in that The reaction temperature in step (1) is -20°C ± 2°C; The molar and volume ratio of the compound 1, the aprotic polar solvent, NMM and Fmoc-Lys-OH is ( 3.8～3.9 )mol:( 3～4 )L: (940~1000)mL: (7.36~7.50)mol; The equivalent weight of the chloroformate is 1.05 to 1.5; The preparation method of the precooled Fmoc-Lys-OH DMF solution is as follows: weigh Fmoc-Lys-OH, dissolve it in a non-protonic polar solvent solution, add NMM, shake to dry, and freeze to obtain.

6. The synthesis method according to claim 2, characterized in that The reaction temperature in step (2) is 10°C to 20°C; The mass volume ratio of the trifluoroacetic acid to compound 2 is (3.0-3.3) L: (3-3.6) kg.

7. The synthesis method according to claim 2, characterized in that The reaction temperature in step (3) is -20°C ± 2°C; The mass volume ratio of the compound 1, the aprotic polar solvent, NMM and the compound 3 is 1.69 kg: (3.34-4.00) L: (720-750) mL: (3.7-3.8) kg.

8. The synthesis method according to claim 2, characterized in that The reaction temperature in step (4) is 10-15°C; The mass volume ratio of the trifluoroacetic acid to compound 4 is (3.30-3.50) L: (4.4-4.5) kg.

9. The synthesis method according to claim 2, characterized in that The molar ratio of compound 5 to active ester in step (5) is 1:

1.

10. Use of the method according to any one of claims 1 to 9 in the synthesis of semaglutide side chain intermediates or semaglutide.

Images