Method for chemically synthesizing Fmoc-Ser-NH2

Abstract

The invention discloses a method for chemically synthesizing Fmoc-Ser-NH2, and relates to the technical field of polypeptide synthesis. The method comprises the following steps: synthesizing Fmoc-O-Ac-Ser by taking O-acetylserine hydrochloride as a raw material, then carrying out carboxyl amidation, and then carrying out controlled saponification to obtain a target product. The method solves the problems that the cost is high when a solid-phase synthesis method is adopted at present, the product is unstable when strong acid is used for removing side chain tert-butyl groups in a liquid-phase synthesis method, or the cost is high or the yield is low when a hydrogenation method is adopted for removing side chain benzyl. Comprising the following synthesis steps: taking O-acetylserine hydrochloride as a raw material, then taking baking soda as alkali, carrying out Fmoc protection on amino groups to prepare N-Fmoc-O-acetylserine, synthesizing mixed anhydride from the N-Fmoc-O-acetylserine under the catalysis of the alkali, then carrying out ammonolysis to prepare N-Fmoc-O-acetylserine amide, and finally, preparing the N-Fmoc-O-acetylserine amide from the N-Fmoc-O-acetylserine amide. N-Fmoc-O-acetylserine amide is used for saponifying O-acetyl by controlling conditions, so that a target product Fmoc-Ser-NH2 is synthesized.

Description

Technical Field

[0001] The present invention relates to the technical field of polypeptide synthesis, and in particular to a method for chemically synthesizing Fmoc-Ser-NH2. Background Art

[0002] Fmoc-Ser-NH2 is a fluoromolybdate (Fmoc) protected amino (NH2) derivative of serine (Serine, Ser). Fmoc-Ser-NH2 is an important compound, especially in synthetic chemistry and biochemistry, and its Fmoc protecting group gives it greater flexibility and selectivity in various reactions. Fmoc-Ser-NH2 is often used in solid phase peptide synthesis (SPPS) as part of the construction of peptides or proteins. Due to the importance of serine in proteins, this derivative can also be used to study related biochemical processes.

[0003] Literature reports that Fmoc-Ser(tBu)-NH2 is prepared by carboxyl amidation using Fmoc-Ser(tBu) as the raw material, and then acidification is performed to remove the O-tert-butyl group, thereby obtaining the target product Fmoc-Ser-NH2. This synthesis method has the disadvantages of difficulty in removing the O-tert-butyl group, difficulty in controlling the conditions, many product impurities and difficulty in purification. In addition, the raw material Fmoc-Ser(tBu) is obtained by transesterification with isobutylene, which is expensive and difficult to purchase in the market.

[0004] There are literature reports that Fmoc-Ser (Bzl) is used as a raw material, and then the carboxyl group is amidated to obtain Fmoc-Ser (Bzl) -NH2, and then hydrogenated to obtain the target product Fmco-Ser-NH2. The raw material Fmoc-Ser (Bzl) of this method needs to be prepared under a strong base to prepare BOC-Ser (Bzl) and then de-BOC to obtain FMOC. The product is easy to racemize under a strong base. The Fmoc-Ser (Bzl) -NH2 raw material is catalyzed by palladium carbon to pass hydrogen, and then Fmco-Ser-NH2 is obtained. Passing hydrogen has a great safety hazard and the price of palladium carbon is expensive.

[0005] In the literature, there are many methods for synthesizing Fmoc-Ser-NH2, but these methods generally have certain defects, such as: difficulty in removing the O-tert-butyl group, difficulty in controlling the conditions, low product purity, difficulty in purification, high cost and difficulty in obtaining raw materials, which limits the wide application of Fmoc-Ser-NH2 and the convenience of practical operation. Summary of the invention

[0006] In view of the above technical problems, the present application solves the shortcomings of the synthesis process in the above literature and designs a synthesis method with simple operation, easy control of conditions, stable quality, stable yield, and better overall cost and benefit.

[0007] In order to achieve the above object, the technical solution adopted in the present application is: a method for chemically synthesizing Fmoc-Ser-NH2, comprising the following steps:

[0008] Step 1: O-acetylserine hydrochloride is used as a raw material, baking soda is added in an organic solvent for catalysis, and Fmoc-OSu is used as a protective agent to protect the amino group to form an Fmoc-protected amino acid derivative, namely Fmoc-O-Ac-serine.

[0009] Step 2: Fmoc-O-Ac-serine is added to an organic solvent, an organic base is added as an acid-binding agent, and ethyl chloroformate is added dropwise at low temperature to react, and then the reaction solution is added dropwise to concentrated ammonia water at low temperature to carry out aminolysis, and Fmoc-O-Ac-Ser-NH2 is obtained after the reaction.

[0010] Step 3: Dissolve Fmoc-O-Ac-Ser-NH2 in a water mixture, cool it with tap water, add 5N liquid alkali for saponification, and then purify it to obtain the target product Fmoc-Ser-NH2.

[0011] Preferably, in step 1, the molar ratio of O-acetylserine hydrochloride to baking soda is 1:1.5-3.

[0012] Preferably, in the step one, the amino group is protected with Fmoc-OSu, and the molar ratio of O-acetylserine hydrochloride to Fmoc-OSu is 1:0.95-1.1.

[0013] Preferably, the organic solvent in step 1 is any one of THF and acetonitrile.

[0014] Preferably, the organic solvent in step 2 is any one of dichloromethane, THF, ethyl acetate and acetonitrile.

[0015] Preferably, the acid binding agent in step 2 is one of pyridine, N-methylmorpholine, triethylamine and diisopropylethylamine, and the molar ratio of ethyl chloroformate to the acid binding agent is 1:1-2.5.

[0016] Preferably, the reaction temperature in step 2 is between 0°C and 15°C.

[0017] Preferably, the water mixture in step 3 is prepared by mixing water with any one of THF, methanol, ethanol and acetonitrile.

[0018] Preferably, the liquid alkali in step three is any one of sodium carbonate, caustic soda solution, potassium carbonate, potassium bicarbonate and triethylamine.

[0019] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0020] 1. The present invention uses O-acetylserine hydrochloride as a raw material, combined with an effective catalyst and a protective agent, thereby ensuring the high efficiency of the synthesis step and the rapid progress of the reaction.

[0021] 2. The method of the present invention simplifies the synthesis process through three main steps, avoids tedious protective group removal and repeated purification steps, reduces operational complexity, and improves experimental efficiency.

[0022] 3. In the synthesis process of the present invention, low temperature conditions and mild organic solvents are used to reduce the probability of side reactions, thereby improving the selectivity and purity of the product.

[0023] 4. The present invention improves the purity of the final product Fmoc-Ser-NH2 by selecting an appropriate acid-binding agent and optimizing the reaction conditions, reduces the generation of impurities, and makes the subsequent purification process more efficient.

[0024] 5. The synthesis method of the present invention avoids the use of hydrogen, reduces potential safety hazards in the experimental process, and the chemical reagents (such as alkaline substances) used are relatively safe and easier to operate.

[0025] 6. The synthesis of O-acetylserine hydrochloride and its derivatives in the present invention is relatively simple, the cost is relatively low, and the raw materials are easily available in the market, so it has good economy and sustainability.

[0026] 7. The present invention allows operators to optimize the synthesis method according to experimental requirements by selecting different organic solvents and acid-binding agents, thereby making the synthesis method more flexible.

[0027] 8. The solvent and reaction conditions used in the present invention are relatively mild, which reduces pollution to the environment, conforms to the principles of green chemistry, and promotes sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The synthetic method for preparing Fmoc-Ser-NH2 of the present invention

[0029] Figure 2 The liquid phase spectrum of Example 2 of the present invention;

[0030] Figure 3 The liquid phase spectrum of Example 3 of the present invention;

[0031] Figure 4 The liquid phase spectrum of Example 4 of the present invention;

[0032] Figure 5 is the liquid phase spectrum of Example 5 of the present invention; DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0035] Embodiment 1:

[0036] A method for chemically synthesizing Fmoc-Ser-NH2, the synthetic route is as follows Figure 1 As shown, the following steps are included:

[0037] Step 1: O-acetylserine hydrochloride is used as a raw material, baking soda is added in an organic solvent for catalysis, and Fmoc-OSu is used as a protective agent to protect the amino group to form an Fmoc-protected amino acid derivative, namely Fmoc-O-Ac-serine. By using O-acetylserine hydrochloride as a raw material, combined with an effective catalyst and protective agent, the high efficiency of the synthesis step and the rapid progress of the reaction are ensured.

[0038] Step 2: Fmoc-O-Ac-serine is added to an organic solvent, an organic base is added as an acid-binding agent, and ethyl chloroformate is added dropwise at low temperature for reaction, and then the reaction solution is added dropwise to concentrated ammonia water at low temperature for aminolysis, and Fmoc-O-Ac-Ser-NH2 is obtained after the reaction. By selecting an appropriate acid-binding agent and optimizing the reaction conditions, the purity of the final product Fmoc-Ser-NH2 is improved, the generation of impurities is reduced, and the subsequent purification process is more efficient.

[0039] Step 3: Dissolve Fmoc-O-Ac-Ser-NH2 in a water mixture, cool it with tap water, add 5N liquid alkali for saponification, and then purify it to obtain the target product Fmoc-Ser-NH2.

[0040] The synthesis process is simplified through three main steps, avoiding tedious protective group removal and repeated purification steps, reducing operational complexity and improving experimental efficiency; the synthesis of O-acetylserine hydrochloride and its derivatives is relatively simple, the cost is relatively low, and the raw materials are easily available on the market, with good economy and sustainability. The synthesis method avoids the use of hydrogen, reduces safety hazards in the experimental process, and the chemical reagents used (such as alkaline substances) are relatively safe and easier to operate.

[0041] In the step 1, the molar ratio of O-acetylserine hydrochloride to baking soda is 1:1.5-3.

[0042] In the step one, the amino group is protected with Fmoc-OSu, and the molar ratio of O-acetylserine hydrochloride to Fmoc-OSu is 1:0.95-1.1.

[0043] The organic solvent in step 1 is any one of THF and acetonitrile.

[0044] The organic solvent in step 2 is any one of dichloromethane, THF, ethyl acetate and acetonitrile.

[0045] The acid-binding agent in step 2 is one of pyridine, N-methylmorpholine, triethylamine and diisopropylethylamine, and the molar ratio of ethyl chloroformate to the acid-binding agent is 1:1-2.5. By selecting different organic solvents and acid-binding agents, operators can optimize according to experimental requirements, making the synthesis method more flexible.

[0046] The reaction temperature in step 2 is between 0° C. and 15° C. The low temperature and mild organic solvent reduce the probability of side reactions, thereby improving the selectivity and purity of the product.

[0047] The water mixed liquid in step 3 is prepared by mixing water with any one of THF, methanol, ethanol and acetonitrile.

[0048] The liquid alkali in step 3 is any one of sodium carbonate, caustic soda solution, potassium carbonate, potassium bicarbonate and triethylamine.

[0049] Embodiment 2:

[0050] like Figure 3As shown, in the 1#250ml three-necked flask, add Fmoc-Ser(tBu)7.68g / 0.02mol, add 30ml acetonitrile, and stir to dissolve. Cool down to 10℃ with ice-salt bath, then add 4g triethylamine and 2.6g ethyl chloroformate at the same time to react. After dripping DIPEA and ethyl chloroformate, maintain 10℃ for reaction for 30 minutes, and then warm to room temperature for 2 hours. At the same time, add 20mlTHF and 4.2g concentrated ammonia water to the 2#250ml three-necked flask for standby use. The reaction solution in the 1# three-necked flask with the above reaction was quickly dripped into the 2# three-necked flask at 10-15℃ for aminolysis. After dripping, naturally warm to room temperature and react overnight. The next day, add 10ml water to the 2# three-necked flask and stir for one hour to hydrolyze the unreacted raw material intermediate. The reaction solution in the 2# three-necked flask was neutralized with 2N hydrochloric acid, and then the acetonitrile was concentrated. 40ml EA was added to the concentrated residue, and the layers were stirred. The aqueous layer was discarded if there was no product. The organic layer was washed 4 times with 10% sodium carbonate brine 15ml×4, and the water was separated. The aqueous layer was discarded. The organic layer was washed 4 times with dilute acidic brine 15ml×4, and the water was separated. The organic layer was dried by adding anhydrous sodium sulfate. Filter, concentrate the filtrate to a small volume, do not concentrate, add an appropriate amount of petroleum ether to the residue, stir and crystallize, and filter to obtain the intermediate Fmoc-Ser(tBu)-NH25.91g. 5.91g Fmoc-Ser(tBu)-NH2 was dissolved in 50ml 3N HCl / THF solution and stirred overnight. The next day, 50ml EA and 20ml water were added to the reaction solution, and the layers were separated. The aqueous layer was discarded. The organic layer was washed with 10% sodium carbonate brine 15ml×4 to remove polar impurities 4 times, then washed with brine until neutral, and water was separated. Anhydrous sodium sulfate was added to the organic layer for drying. Filter, the filtrate was concentrated to remove about half of the volume of solvent, and a large amount of MTBE was added to the residual liquid for pulping and filtering. The crude product was recrystallized with THF-EA to obtain the product Fmoc-Ser-NH22.6g, HPLC94.49%, and the yield of this step was 48%.

[0051] The reaction point plate for amidation is as follows: DCM:MeOH=5:1, UV color development, the middle is the raw material Fmoc-Ser, and the two sides are the reaction solutions after amidation.

[0052] Embodiment 3:

[0053] like Figure 3As shown, 5.5g O-acetylserine hydrochloride was dissolved in 40ml water, 15ml acetonitrile was added, and the mixture was stirred to dissolve. 5g baking soda was added, and then 9.6g FMOC-OSu was added. After the addition, the mixture was reacted at room temperature overnight. The next day, the reaction solution was dissolved with a small amount of dilute hydrochloric acid to make the solid clear, and then the system pH was maintained at 8 with sodium carbonate. 30% EA / Pet (V / V) 20ml×3 was added to the reaction solution and the mixture was extracted 3 times, and the organic phase was discarded. 50ml EA was added to the aqueous phase, and the mixture was acidified to pH 2-3 with dilute hydrochloric acid, separated, and the organic phase was washed with brine to remove large polar impurities, and the aqueous layer was separated. The organic phase was dried with anhydrous sodium sulfate. Filter, concentrate the filtrate to a small volume, add petroleum ether to the residual liquid for pulping, filter and dry to obtain FMOC-O-Ac-Ser9.28g.

[0054] Dissolve 9.28g FMOC-O-Ac-Ser in 40ml DCM, then add 7.1g DIPEA to the reaction bottle at 10℃ to adjust the system pH to 8-9, and add 3.54g ethyl chloroformate at the same time. After the addition, continue to react at 10℃-15℃ for 30 minutes, and then naturally warm to room temperature for 1 hour. Prepare the aminolysis solution (25ml THF + 5.25g concentrated ammonia water) in another reaction bottle, and drop the above reaction solution into the aminolysis solution at 10-15℃ for reaction. After the drop is completed, naturally warm to room temperature for overnight reaction. The next day, add 15ml water to the reaction solution and stir for one hour to hydrolyze the unreacted raw material intermediate. Adjust to neutral with 2N hydrochloric acid, then concentrate to remove the organic solvent, add 60ml EA to the concentrated residue, stir and separate. The water layer without product is discarded, and the organic layer is washed 4 times with 10% sodium carbonate brine 20ml×4, and the water is separated and the water layer is discarded. The organic layer was washed 4 times with 20 ml of dilute acidic brine, and the water was removed. The organic layer was dried by adding anhydrous sodium sulfate. Filter, concentrate the filtrate to a small volume, do not concentrate, add an appropriate amount of petroleum ether to the residual liquid, stir and crystallize, and filter to obtain the intermediate Fmoc-Ser(Ac)-NH28.14g. 8.14g Fmoc-Ser(Ac)-NH2 was dissolved in 20 ml of acetonitrile and 20 ml of aqueous solution, and 4.4 g KHCO3 was added and stirred overnight. The next morning, 80 ml EA was added to the reaction solution, the layers were separated, and the water layer was discarded. The organic layer was washed with 10% sodium carbonate brine 20 ml×4 to remove large polar impurities 4 times, and then washed with brine until neutral, and the water was removed. Anhydrous sodium sulfate was added to the organic layer to dry. Filter, the filtrate was concentrated to remove about half of the volume of the solvent, and a large amount of MTBE was added to the residual liquid for pulping and filtering. The crude product was recrystallized from THF-EA to obtain 5.46 g of the product Fmoc-Ser-NH2, HPLC 97.55%, and the yield of this step was 75.9%.

[0055] Embodiment 4:

[0056] like Figure 4As shown, 22g O-acetylserine hydrochloride was dissolved in 120ml water, 40ml acetonitrile was added, and the mixture was stirred to dissolve. 22.2g baking soda was added in batches, and then 39.6g FMOC-OSu was added in batches. After the addition, the mixture was reacted at room temperature overnight. The next day, the reaction solution was dissolved with a small amount of dilute hydrochloric acid to make the solid clear, and then the system pH was maintained at 8 with sodium carbonate. 30% EA / Pet (V / V) 40ml×3 was added to the reaction solution for 3 times of extraction, and the organic phase was discarded. 220ml EA was added to the aqueous phase, and the solution was acidified to pH 2-3 with dilute hydrochloric acid, separated, and the organic phase was washed with brine to remove large polar impurities, and the aqueous layer was separated. The organic phase was dried with anhydrous sodium sulfate. Filter, concentrate the filtrate to a small volume, add petroleum ether to the residual liquid for pulping, filter and dry to obtain FMOC-O-Ac-Ser40g.

[0057] Dissolve 40g FMOC-O-Ac-Ser in 120ml DCM, then add 20g triethylamine to the reaction bottle at 10℃ to adjust the system pH to 8-9, and add 17.58g ethyl chloroformate at the same time. After the addition, continue to react at 10℃-15℃ for 30 minutes, then naturally warm to room temperature for 1 hour. Prepare the ammonolysis solution (120ml THF + 23g concentrated ammonia water) in another reaction bottle, and drip the above reaction solution into the ammonolysis solution at 10-15℃ for reaction. After the dripping is completed, naturally warm to room temperature for overnight reaction. The next day, add 40ml water to the reaction solution and stir for one hour to hydrolyze the unreacted raw material intermediate. Use 2N hydrochloric acid to neutralize, then concentrate to remove the organic solvent, add 300ml EA to the concentrated residue, and stir to separate. The water layer without product is discarded, and the organic layer is washed 4 times with 10% sodium carbonate brine 50ml×4, and the water is separated and the water layer is discarded. The organic layer was washed 4 times with 50 ml of dilute acidic brine, and the water was separated. The organic layer was dried by adding anhydrous sodium sulfate. Filter, concentrate the filtrate to a small volume, do not concentrate, add an appropriate amount of petroleum ether to the residual liquid, stir and crystallize, and filter to obtain the intermediate Fmoc-Ser(Ac)-NH233.8g. 33.8gFmoc-Ser(Ac)-NH2 was dissolved in 100 ml of acetonitrile and 30 ml of aqueous solution, and 10.8 gKHCO3 was added and stirred overnight. The next morning, 300 mlEA was added to the reaction solution, the layers were separated, and the water layer was discarded. The organic layer was washed with 10% sodium carbonate brine 50 ml×4 to remove large polar impurities 4 times, and then washed with brine until neutral, the water was separated, and anhydrous sodium sulfate was added to the organic layer to dry. Filter, the filtrate was concentrated to remove about half of the volume of the solvent, and a large amount of MTBE was added to the residual liquid for pulping and filtering. The crude product was recrystallized with THF-EA to obtain 24.5 g of the product Fmoc-Ser-NH2, HPLC 98.07%, and the yield of this step was 82.3%.

[0058] Embodiment 5:

[0059] like Figure 5As shown, 110g O-acetylserine hydrochloride was dissolved in 600ml water, 200ml THF was added, and the mixture was stirred to dissolve. 101g baking soda was added in batches, and then 198g FMOC-OSu was added in batches. After the addition, the mixture was reacted at room temperature overnight. The next day, the reaction solution was dissolved with a small amount of dilute hydrochloric acid to make the solid clear, and then sodium carbonate was used to maintain the system pH 8. 30% EA / Pet (V / V) 200ml×3 was added to the reaction solution and extracted 3 times, and the organic phase was discarded. 800ml EA was added to the aqueous phase, acidified to pH 2-3 with dilute hydrochloric acid, separated, and the organic phase was washed with brine to remove large polar impurities, and the aqueous layer was separated. The organic phase was dried over anhydrous sodium sulfate. Filter, concentrate the filtrate to a small volume, add petroleum ether to the residual liquid for pulping, filter and dry to obtain FMOC-O-Ac-Ser191.5g.

[0060] Dissolve 191.5g FMOC-O-Ac-Ser in 300ml acetonitrile, then add 133.4g DIPEA to the reaction bottle at 10℃ to adjust the system pH to 8-9, and add 73g ethyl chloroformate at the same time. After the addition, continue to react at 10℃-15℃ for 30 minutes, then naturally warm up to room temperature for 1 hour. Prepare the aminolysis solution (400ml THF + 120g concentrated ammonia water) in another reaction bottle, and drip the above reaction solution into the aminolysis solution at 10-15℃ for reaction. After the dripping is completed, naturally warm up to room temperature for overnight reaction. The next day, add 200ml water to the reaction solution and stir for one hour to hydrolyze the unreacted raw material intermediate. Use 2N hydrochloric acid to neutralize, then concentrate to remove the organic solvent, add 800ml EA to the concentrated residue, and stir to separate. The water layer without product is discarded, and the organic layer is washed 4 times with 10% sodium carbonate brine 200ml×4, and the water is separated and the water layer is discarded. The organic layer was washed 4 times with 200ml of dilute acidic brine, and the water was removed. The organic layer was dried by adding anhydrous sodium sulfate. Filter, concentrate the filtrate to a small volume, do not concentrate, add an appropriate amount of petroleum ether to the residual liquid, stir and crystallize, and filter to obtain the intermediate Fmoc-Ser(Ac)-NH2164.5g. 164.5gFmoc-Ser(Ac)-NH2 was dissolved in 300ml acetonitrile and 200ml aqueous solution, and 56.5gNa2CO3 was added and stirred overnight. The next morning, 400ml of water and 800mlEA were added to the reaction solution, and then sodium carbonate was dissolved with dilute hydrochloric acid, separated, and the aqueous layer was discarded. The organic layer was washed with 10% sodium carbonate brine 200ml×4 to remove large polar impurities 4 times, and then washed with brine until neutral, and the water was removed. Anhydrous sodium sulfate was added to the organic layer to dry. Filter, the filtrate was concentrated to remove about half of the volume of the solvent, and a large amount of MTBE was added to the residual liquid for pulping and filtering. The crude product was recrystallized with THF-EA to obtain 121 g of the product Fmoc-Ser-NH2, HPLC 99.39%, and the yield of this step was 83.2%.

[0061] The above is only a preferred embodiment of the present application, and is only selected as a control condition. The impact on product yield and quality does not mean that this patent technology has only been verified by nine experiments.

[0062] Comparing Example 2 and Example 3, during the experiment, Example 2 used Fmoc-Ser(tBu) as a raw material to synthesize the target product, but no product of satisfactory quality was obtained. Example 3 used O-Ac-Ser.HCl as a raw material to obtain a product of satisfactory quality, so it is better to use O-Ac-Ser.HCl as a raw material to synthesize Fmoc-Ser-NH2.

[0063] Comparative Examples 3, 4, and 5, the proportion of some auxiliary materials was optimized during the operation, and in the process of reproducing the experiment, the target product with better and better quality and higher yield was obtained. For example, the molar ratio of O-acetylserine hydrochloride to sodium bicarbonate was 1:1.5-3, and the molar ratio of Fmoc-OSu was 1:0.95-1.1. These optimizations improved the selectivity of the reaction and the purity of the product, thereby forming the final synthetic route.

[0064] All embodiments use mild reaction conditions, and the reaction temperature is controlled between 0°C and 15°C to reduce the occurrence of side reactions. The organic solvents (such as THF, acetonitrile, etc.) and acid binding agents (such as triethylamine, etc.) used are also carefully selected to improve the flexibility and efficiency of the reaction.

[0065] By comparing the experimental results of different embodiments, it can be seen that selecting appropriate raw materials, optimizing material ratios and controlling reaction conditions are key factors in improving the quality and yield of Fmoc-Ser-NH2 synthesis. The synthesis method of the present invention has significant advantages in improving experimental efficiency, reducing operational complexity and environmental impact, and is suitable for practical application and industrial production.

[0066] In general, the comparative experimental analysis of multiple embodiments provides strong support for the synthesis route of the present invention and verifies its effectiveness and feasibility in synthesizing Fmoc-Ser-NH2.

[0067] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for chemically synthesizing Fmoc-Ser-NH2, comprising the following steps: Step 1: O-acetylserine hydrochloride is used as a raw material, baking soda is added in an organic solvent for catalysis, and Fmoc-OSu is used as a protective agent to protect the amino group to form an Fmoc-protected amino acid derivative, namely Fmoc-O-Ac-serine; Step 2: Fmoc-O-Ac-serine is added to an organic solvent, an organic base is added as an acid-binding agent, and ethyl chloroformate is added dropwise at low temperature to react, and then the reaction solution is added dropwise to concentrated ammonia water at low temperature to perform aminolysis, and Fmoc-O-Ac-Ser-NH2 is obtained after the reaction; Step 3: Dissolve Fmoc-O-Ac-Ser-NH2 in a water mixture, cool it with tap water, add 5N liquid alkali for saponification, and then purify it to obtain the target product Fmoc-Ser-NH2.

2. A method for chemically synthesizing Fmoc-Ser-NH2 according to claim 1, characterized in that: In the step 1, the molar ratio of O-acetylserine hydrochloride to baking soda is 1:1.5-3.

3. A method for chemically synthesizing Fmoc-Ser-NH2 according to claim 1, characterized in that: In the step one, the amino group is protected with Fmoc-OSu, and the molar ratio of O-acetylserine hydrochloride to Fmoc-OSu is 1:0.95-1.

1.

4. A method for chemically synthesizing Fmoc-Ser-NH2 according to claim 1, characterized in that: The organic solvent in step 1 is any one of THF and acetonitrile.

5. A method for chemically synthesizing Fmoc-Ser-NH2 according to claim 1, characterized in that: The organic solvent in step 2 is any one of dichloromethane, THF, ethyl acetate and acetonitrile.

6. A method for chemically synthesizing Fmoc-Ser-NH2 according to claim 1, characterized in that: The acid binding agent in step 2 is one of pyridine, N-methylmorpholine, triethylamine and diisopropylethylamine, and the molar ratio of ethyl chloroformate to the acid binding agent is 1:1-2.

5.

7. A method for chemically synthesizing Fmoc-Ser-NH2 according to claim 1, characterized in that: The reaction temperature in step 2 is between 0°C and 15°C.

8. A method for chemically synthesizing Fmoc-Ser-NH2 according to claim 1, characterized in that: The water mixed liquid in step 3 is prepared by mixing water with any one of THF, methanol, ethanol and acetonitrile.

9. A method for chemically synthesizing Fmoc-Ser-NH2 according to claim 1, characterized in that: The liquid alkali in step 3 is any one of sodium carbonate, caustic soda solution, potassium carbonate, potassium bicarbonate and triethylamine.

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