A hypophosphorous acid ester derivative, a preparation method thereof and a polypeptide liquid phase synthesis method as a carrier

Abstract

This invention provides a hypophosphite derivative, its preparation method, and a liquid-phase synthesis method for peptides using the hypophosphite derivative as a carrier, belonging to the fields of organic synthesis and peptide chemistry. In this invention, a hypophosphite derivative is prepared. The hypophosphite derivative provided in this application has advantages such as simple preparation method, low-cost raw materials, and easily adjustable structure. The peptide liquid-phase synthesis method using the hypophosphite derivative as a carrier can efficiently synthesize peptides and improve the solubility of intermediates in the preparation process of peptides (especially hydrophobic peptides), avoiding aggregation or precipitation, and has practical application value for peptide chemical synthesis.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis and polypeptide chemistry, and relates to a hypophosphite derivative and its preparation method, as well as a polypeptide liquid-phase synthesis method using it as a carrier. Background Technology

[0002] Peptides and proteins play vital physiological functions in living organisms, such as hormones, neurotransmitters, and antibodies, and are key molecules in drug development and biological research. In 1963, Merrifield first proposed the solid-phase peptide synthesis (SPPS) method, ushering in the era of automated peptide synthesis. This method simplifies product separation and purification processes by immobilizing the first amino acid on a solid resin and progressively extending the peptide chain, significantly improving synthesis efficiency and reproducibility. SPPS not only saves considerable time but also paves the way for automated synthesis, enabling rapid construction of large-scale peptide libraries in combinatorial chemistry, from research-level micro-synthesis, and has driven the development of peptide drugs. It is currently widely used in basic research and industrial production.

[0003] However, SPPS suffers from significant shortcomings in green chemistry and sustainability, which has become an increasingly prominent problem in its large-scale industrial applications. The most prominent issues are its extremely poor atom economy and extremely high process quality intensity. To achieve near-quantitative coupling efficiency at each step, several times the amount of amino acids and condensing agents are typically required, leading to a large waste of raw materials. Ultimately, only a very small proportion (e.g., the atom economy of arginine can be as low as 0.19) enters the target product. Even more serious is the high dependence of SPPS on large amounts of toxic solvents (such as N,N-dimethylformamide, dichloromethane, tetrahydrofuran, etc.). These solvents are not only used in coupling and deprotection reactions but are also consumed in large quantities during resin cleaning after each step, resulting in a huge environmental burden and high wastewater treatment costs.

[0004] Carrier-assisted liquid-phase synthesis (LPPS) of peptides uses soluble small molecules instead of the insoluble resins used in SPPS as carriers. This allows amino acid condensation and deprotection reactions to occur in a homogeneous solution, resulting in higher reaction efficiency than SPPS. Consequently, it eliminates the need for large amounts of excess reagents, significantly reducing waste and making it more environmentally friendly and economical. Furthermore, LPPS utilizes the solubility differences of carrier molecules in different solvents to purify intermediates through simple operations such as precipitation and extraction, eliminating the need for complex chromatographic procedures and combining the simplicity and speed of SPPS. Previously reported carriers, when used to prepare peptides, especially complex peptide sequences (long-sequence peptides or hydrophobic peptides), suffer from reduced solubility, precipitation, and gelation due to intermolecular aggregation, leading to hindered mass transfer and decreased reaction efficiency. Therefore, there is a need to develop carriers with high preparation efficiency to improve peptide aggregation during the preparation process. Summary of the Invention

[0005] The primary objective of this invention is to overcome the shortcomings of the prior art and provide a hypophosphite derivative.

[0006] Another object of the present invention is to provide a method for preparing the hypophosphite derivatives.

[0007] Another object of the present invention is to provide a method for liquid-phase synthesis of polypeptides using the aforementioned hypophosphite derivatives as carriers.

[0008] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0009] A hypophosphite derivative has the following general structural formula:

[0010]

[0011] The method for preparing the hypophosphite derivatives includes the following preparation steps:

[0012] Step a: Preparation of intermediate 1:

[0013] 2,4-Dihydroxybenzaldehyde and triethylamine were placed in dichloromethane (DCM), and a DCM solution of diphenylphosphine chloride was added dropwise under ice bath conditions. The mixture was stirred at room temperature, and then extracted and purified by adding saturated sodium bicarbonate solution and DCM to obtain intermediate 1.

[0014] Step b: Preparation of the target hypophosphite derivative ANT:

[0015] Intermediate 1 was dissolved in methanol (MeOH), and a MeOH solution of reducing agent (sodium borohydride or hydroxylamine hydrochloride) was added dropwise under ice bath. The mixture was stirred at room temperature. After the reaction was completed, saturated ammonium chloride solution and DCM were added for extraction, washing, drying, and vacuum distillation to obtain the target hypophosphite derivative ANT.

[0016] The reaction process is as follows:

[0017]

[0018] Furthermore, in step a, the molar ratio of 2,4-dihydroxybenzaldehyde, triethylamine, and diphenylphosphine chloride is 1:3:2.5, and the reaction time is 3 hours.

[0019] Furthermore, in step b, the molar ratio of intermediate 1 and reducing agent (sodium borohydride or hydroxylamine hydrochloride) is 1:3, and the reaction time is 2 hours.

[0020] The method for liquid-phase synthesis of peptides using hypophosphite derivatives as carriers includes the following synthesis steps:

[0021] Step A: Preparation of Intermediate 2:

[0022] Under the action of a dehydrating coupling agent, the hypophosphite derivative carrier ANT and an α-amino protected amino acid are dissolved in DCM and reacted with stirring at room temperature to obtain intermediate 2. The α-amino protected amino acid has a tert-butoxycarbonyl Boc- protecting group, and the C-terminus of the amino acid is linked to the ANT carrier to generate intermediate 2 as Boc-AA1-ANT. AA refers to any amino acid. Weakly polar n-hexane or petroleum ether is added to the DCM solution of intermediate 2. Taking advantage of the easy crystallization and precipitation property of the hypophosphite derivative carrier ANT in the solvent system, intermediate 2 is separated from impurities. The separated intermediate 2 is then filtered and washed or recrystallized to obtain purified intermediate 2.

[0023] Step B: Preparation of intermediate 3:

[0024] The purified intermediate 2 was treated with a Boc removal reagent and stirred to obtain intermediate 3 (NH2-AA1-ANT). A weakly polar n-hexane or petroleum ether was added to the DCM solution of intermediate 3. Taking advantage of the characteristic that the hypophosphite derivative carrier ANT is easy to crystallize and precipitate in the solvent system, intermediate 3 was separated from impurities. The separated intermediate 3 was filtered and washed or recrystallized to obtain purified intermediate 3.

[0025] Step C: Preparation of intermediate 4:

[0026] Using purified intermediate 3 as a starting material, step A was repeated to couple it with the second α-amino protected amino acid Boc-AA2-OH to obtain intermediate 4 (Boc-AA2-AA1-ANT).

[0027] Step D: Preparation of intermediate 5:

[0028] Using purified intermediate 4 as raw material, step B was repeated, and a Boc removal reagent was added to obtain intermediate 5 (NH2-AA2-AA1-ANT).

[0029] Step E: Preparation of intermediate 6:

[0030] Using purified intermediate 5 (NH2-AA2-AA1-ANT) as a starting material, it is coupled with the third α-amino protected amino acid Boc-AA3-OH; steps A to B are repeated to obtain intermediate NH2-AA3-AA2-AA1-ANT; the above steps are repeated cyclically, using the purified intermediate NH2-AA1 after the (n-1)th repetition. n-1 -X-AA3-AA2-AA1-ANT as a starting material, with the nth α-amino group protected by the amino acid Boc-AA n-OH undergoes a coupling reaction; repeat steps A to B to obtain intermediate 6 (Boc-AA). n -X-AA3-AA2-AA1-ANT).

[0031] Step F: Preparation of the target peptide:

[0032] Using aqueous solutions of trifluoroacetic acid (TFA) and triisopropylsilane (TIPS) as deprotecting agents, intermediate 6 (Boc-AA) was removed. n Protecting groups such as tBu, Boc, and Pbf on the side chain of the -X-AA3-AA2-AA1-ANT protein were removed, and the ANT carrier of the hypophosphite derivative was cleaved. The trifluoroacetate of the target sequence polypeptide was then obtained through separation and purification. The trifluoroacetate of the target polypeptide was neutralized with sodium bicarbonate solution, and the pH of the solution was adjusted to the isoelectric point of the target polypeptide. The polypeptide was extracted with ethyl acetate, the precipitate was collected, filtered, washed with ethyl acetate, and dried to obtain the purified target polypeptide NH2-AA. n -X-AA3-AA2-AA1-OH.

[0033] The reaction process is as follows:

[0034]

[0035] Where X is a random number of amino acids.

[0036] Further, in step A, the molar ratio of the carrier, the α-amino protected amino acid, the dehydrating coupling agent EDCI, and DMAP is 1:1.5:1.8:0.12, and the reaction time is 1–4 h.

[0037] Furthermore, the volume of the weakly polar n-hexane or petroleum ether mentioned in step A is 5 to 10 times the volume of the DCM.

[0038] Further, the Boc removal reagent in step B is a trifluoroacetic acid (DCM) solution with a volume ratio of 20% to 30%, the reaction temperature is 0 to 25°C, the reaction time is 0.5 to 3 hours, and the volume of the weakly polar n-hexane or petroleum ether is 5 to 10 times the volume of the DCM.

[0039] Furthermore, the deprotection reaction temperature in step F is 5–25°C, the reaction time is 1–4 h, and the volume ratio of each component in the deprotection reagent is: TFA / TIPS / H2O = 95:2.5:2.5.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] The hypophosphite derivative carriers proposed in this invention can improve the solubility of peptides (especially hydrophobic peptides) and their intermediates in common solvents, avoid aggregation and precipitation during the preparation process, and improve the efficiency of peptide sequence synthesis. These carriers have advantages such as simple preparation methods, low-cost raw materials, and easily adjustable structures. The peptide liquid-phase synthesis method based on the aforementioned hypophosphite derivatives as carriers combines the advantages of both liquid-phase and solid-phase synthesis methods, enabling the simple and rapid synthesis of peptides and their derivatives, while reducing raw material waste, minimizing waste pollution, saving costs, and being environmentally friendly. It has significant practical application value in organic synthesis and peptide chemistry. Attached Figure Description

[0042] Figure 1 This is a synthetic route diagram of the hypophosphite derivative ANT in Example 1;

[0043] Figure 2 This is a flowchart of the liquid-phase synthesis route of the polypeptide based on the hypophosphite derivative ANT as a carrier in Example 2. Detailed Implementation

[0044] The present invention can be better understood from the following embodiments. However, those skilled in the art will readily understand that the descriptions in the embodiments are for illustrative purposes only and should not, and will not, limit the invention as detailed in the claims.

[0045] Example 1:

[0046] Figure 1 The following is a synthetic route diagram for the hypophosphite derivative ANT in Example 1, illustrating the preparation of the hypophosphite derivative ANT:

[0047] Preparation of Intermediate 1: 25 mL of dichloromethane (DCM) was added to a two-necked flask. 2,4-Dihydroxybenzaldehyde (500 mg, 1 mmol) and triethylamine (1.62 mL, 2.5 mmol) were dissolved in DCM, and the mixture was stirred in an ice bath for 0.5 h. A solution of diphenylphosphine chloride (1.98 mL, 3 mmol) in DCM (1 mL) was added dropwise, and the mixture was stirred at room temperature for 3 h. Post-treatment: Saturated sodium bicarbonate and DCM were added for liquid-liquid extraction. The organic phases were combined, dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to obtain a brown oily intermediate 1 (1.93 g, yield: 99%). 1 H NMR (400MHz, CDCl3) δ10.21 (s, 1H), 7.92-7.78 (m, 8H), 7.69 (d, J=8.6Hz, 1H), 7.5 4 (tdd, J=7.1, 5.4, 1.5Hz, 4H), 7.50-7.36 (m, 9H), 7.25-7.19 (m, 1H), 2.03 (s, 1H).

[0048] Preparation of the hypophosphite derivative ANT: Intermediate 1 (1.5 g, 1 mmol) was dissolved in 10 mL of methanol (MeOH), and a MeOH solution of sodium borohydride (316 mg, 3 mmol) in 4 mL was added dropwise under ice bath. The mixture was stirred at room temperature for 3 h. Saturated ammonium chloride and DCM were added for liquid-liquid extraction. The organic phases were combined, dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to obtain a white solid hypophosphite derivative ANT (1.36 g, yield: 90%). 1 H NMR (400MHz, CDCl3) δ7.89-7.77(m, 4H), 7.74-7.63(m, 4H), 7.56-7.36(m, 12H), 7.2 4 (d, J=1.8Hz, 1H), 6.95 (dt, J=2.4, 1.1Hz, 1H), 6.80 (d, J=1.4Hz, 1H), 4.51 (s, 2H).

[0049] Example 2:

[0050] Figure 2 The above is a flowchart of the liquid-phase synthesis route of the polypeptide based on the hypophosphite derivative ANT as a carrier in Example 2. An example is given of the preparation of the oligopeptide VIA:

[0051] Preparation of intermediate 2 (Boc-Ala-ANT): Under ice bath conditions, amino acid Boc-Ala-OH (240 mg, 1.5 mmol), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI, 292 mg, 1.8 mmol), and 4-dimethylaminopyridine (DMAP, 12 mg, 0.12 mmol) were dissolved in DCM (7 mL). The mixture was kept in an ice bath for 10 min. A DCM solution of compound 2 (458 mg, 1 mmol) in 7 mL was added dropwise, and the mixture was stirred at room temperature for 2 h. Saturated ammonium chloride and DCM were added for separation extraction. The organic phases were combined, dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to obtain a white solid intermediate 2 (512 mg, yield: 85%). 1 HNMR (400MHz, CDCl3) δ7.83-7.78 (m, 8H), 7.58-7.41 (m, 12H), 7.31 (d, J=2.3Hz, 1H), 7.20 (d, J=8.5Hz, 1H), 7 .09 (dt, J=8.6, 1.8Hz, 1H), 5.13 (t, J=10.5Hz, 2H), 4.27 (d, J=7.9Hz, 1H), 1.41 (s, 9H), 1.28 (d, J=7.2Hz, 3H).

[0052] Preparation of intermediate 3 (NH2-Ala-ANT): Intermediate 2 (70 mg, 1 mmol) was dissolved in 2 mL of DCM, and trifluoroacetic acid (400 μL) was added dropwise under ice bath. After the reaction, saturated sodium bicarbonate solution and DCM were added for extraction and purification. The mixture was then extracted separately with saturated sodium bicarbonate solution and DCM, and the organic phases were combined. The organic phase was dried with anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to obtain a white solid intermediate 3 (52 mg, yield: 86%). 1 H NMR (400MHz, CDCl3) δ7.83-7.77(m, 8H), 7.58-7.38(m, 12H), 7.30(d, J=8.1Hz, 1H), 7.23(s, 1H), 7.19 (d, J=8.5Hz, 1H), 5.18-5.01 (m, 2H), 4.12 (d, J=7.1Hz, 1H), 1.26 (d, J=2.7Hz, 3H).

[0053] Preparation of intermediate 4 (Boc-Ile-Ala-ANT): Under ice bath conditions, Boc-Ile-OH (508 mg, 1.5 mmol), 1-hydroxybenzotriazole (HOBT, 297 mg, 1.5 mmol), and N,N′-diisopropylcarbodiimide (DIC, 340 μL, 1.5 mmol) were dissolved in DCM (14 mL). The mixture was kept in an ice bath for 10 min. Then, a DCM solution of intermediate 3 (897 mg, 1 mmol) (14 mL) was added dropwise, and the mixture was stirred at room temperature for 2 h. Saturated sodium bicarbonate solution and DCM were added for liquid-liquid extraction. The organic phases were combined, dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to obtain a white solid intermediate 4 (1.1 g, yield: 90.9%). 1 H NMR (400MHz, CDCl3) δ7.90-7.71 (m, 8H), 7.60-7.40 (m, 12H), 7.19 (d, J=8.7Hz, 2H), 7.12-7.08 (m, 1H), 5.12 (s, 2H), 4.57-4.50 (m, 1 H), 3.96 (t, J=7.7Hz, 1H), 2.04-1.99 (m, 2H), 1.61 (d, J=7.5Hz, 1H), 1.42 (s, 9H), 1.25 (s, 3H), 1.10-1.05 (m, 1H), 0.86-0.83 (m, 6H).

[0054] Preparation of intermediate 5 (NH2-Ile-Ala-ANT): Intermediate 4 (70 mg) was dissolved in 1 mL of DCM, and trifluoroacetic acid (354 μL) was added dropwise under ice bath. After the reaction was completed, saturated sodium bicarbonate solution and DCM were added for liquid-liquid extraction. The organic phases were combined, dried with anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to obtain a white solid intermediate 5 (55 mg, yield: 90%). 1 H NMR (400MHz, CDCl3) δ7.84-7.69 (m, 8H), 7.61-7.37 (m, 12H), 7.22 (d, J=8.5Hz, 1H), 7.15 (s, 1H), 7.04 (d, J=8.4Hz, 1H), 5.09 (s, 2H), 4.45 (t, J=7 .1Hz, 1H), 3.76 (s, 1H), 2.00 (d, J=15.3Hz, 1H), 1.44 (d, J=10.7Hz, 1H), 1 .26 (s, 3H), 1.17-1.11 (m, 1H), 0.88-0.87 (m, 3H), 0.76 (t, J=7.3Hz, 3H).

[0055] Preparation of intermediate 6 (Boc-Val-Ile-Ala-ANT): Under ice bath conditions, Boc-Val-OH (18 mg, 82.8 μmol), HOBT (11.2 mg, 82.8 μmol), and DIC (13 μL, 82.8 μmol) were dissolved in DCM (1 mL). A DCM solution of intermediate 5 (40 mg, 55.2 μmol) was added dropwise, and the mixture was stirred at room temperature for 2 h. After the reaction was complete, saturated sodium bicarbonate solution and DCM were added for liquid-liquid extraction. The combined organic phases were dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to obtain a white solid intermediate 6 (40 mg, yield: 78.9%). 1 H NMR (400MHz, MeOD) δ7.94-7.77 (m, 8H), 7.74-7.49 (m, 12H), 7.25 (dt, J=8.5, 1.9Hz, 1H) , 7.15 (dd, J=8.5, 2.5Hz, 1H), 7.08 (dt, J=8.4, 2.0Hz, 1H), 5.23-5.09 (m, 2H), 4.40 (q, J= 7.3Hz, 1H), 4.27-4.20 (m, 1H), 4.05 (t, J=6.6Hz, 1H), 2.29-2.19 (m, 1H), 2.04 (d, J=7.4 Hz, 1H), 1.46 (d, J=4.2Hz, 10H), 1.36 (s, 3H), 1.07 (d, J=7.0Hz, 1H), 0.95-0.89 (m, 12H).

[0056] Preparation of oligopeptide VIA: 6 mg of intermediate was added dropwise to a 95% trifluoroacetic acid cocktail solution (TFA: 1.9 mL, TIPS: 50 μL, H2O: 50 μL) under ice bath conditions, with stirring. After the reaction, saturated sodium bicarbonate solution was added to adjust the pH, and the mixture was extracted with ethyl acetate. The organic phases were combined, dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to obtain a white solid (oligopeptide VIA) with a yield of 62%. 1 H NMR (400MHz, D2O) δ4.27 (q, J=7.3Hz, 1H), 4.15 (d, J=8.4Hz, 1H), 3.78 (d, J=6.0Hz, 1H), 2.13 (dq, J=13.6, 6.8Hz, 1 H), 1.85-1.73 (m, 1H), 1.46 (m, 1H), 1.36 (d, J=7.3Hz, 3H), 1.14 (m, 1H), 0.97-0.86 (m, 9H), 0.81 (t, J=7.4Hz, 3H).

[0057] The above description is not intended to limit the invention, nor is the invention limited to the examples given. Any changes, modifications, additions, or substitutions made by those skilled in the art within the scope of the invention should also be considered within the protection scope of the invention.

Claims

1. A hypophosphite derivative ANT, characterized in that, The general structural formula of the hypophosphite derivative ANT is as follows:

2. A method for preparing the hypophosphite derivative ANT according to claim 1, characterized in that, Includes the following steps: Step a, intermediate 1 Preparation: 2,4-Dihydroxybenzaldehyde and triethylamine were placed in dichloromethane (DCM), and a DCM solution of diphenylphosphine chloride was added dropwise under ice bath conditions. The mixture was stirred at room temperature, and then extracted and purified by adding saturated sodium bicarbonate solution and DCM to obtain intermediate 1. Step b, preparation of the target hypophosphite derivative ANT: Intermediate 1 was dissolved in methanol (MeOH), and a MeOH solution of reducing agent (sodium borohydride or hydroxylamine hydrochloride) was added dropwise under ice bath. The mixture was stirred at room temperature. After the reaction was completed, saturated ammonium chloride solution and DCM were added for extraction, washing, drying, and vacuum distillation to obtain the target hypophosphite derivative ANT.

3. The method for preparing a hypophosphite derivative according to claim 2, characterized in that, The molar ratio of 2,4-dihydroxybenzaldehyde, triethylamine, and diphenylphosphine chloride in step a is 1:3:2.5, and the reaction time is 3 hours.

4. The method for preparing a hypophosphite derivative according to claim 2, characterized in that, In step b, the molar ratio of intermediate 1 to reducing agent (sodium borohydride or hydroxylamine hydrochloride) is 1:3, and the reaction time is 2 hours.

5. A method for liquid-phase synthesis of polypeptides using the hypophosphite derivative ANT as a carrier according to claim 1, characterized in that, Includes the following steps: Step A, Intermediate 2 Preparation: Under the action of a dehydrating coupling agent, the hypophosphite derivative carrier ANT and an α-amino protected amino acid (AA) are dissolved in DCM and reacted with stirring at room temperature to obtain intermediate 2; the α-amino protected amino acid has a tert-butoxycarbonyl Boc- protecting group, and the C-terminus of the amino acid is connected to the ANT carrier to generate intermediate 2 as Boc-AA1-ANT; AA refers to any amino acid; weakly polar n-hexane or petroleum ether is added to the DCM solution of intermediate 2, and the intermediate 2 is separated from impurities by taking advantage of the easy crystallization and precipitation characteristics of the hypophosphite derivative carrier ANT in the solvent system; The separated intermediate 2 is filtered and washed or recrystallized to obtain purified intermediate 2; Step B, intermediate 3 Preparation: The purified intermediate 2 was treated with a Boc removal reagent and stirred to obtain intermediate 3 (NH2-AA1-ANT); weakly polar n-hexane or petroleum ether was added to the DCM solution of intermediate 3, and intermediate 3 was separated from impurities by taking advantage of the characteristic that the hypophosphite derivative carrier ANT is easy to crystallize and precipitate in the solvent system. The separated intermediate 3 is filtered and washed or recrystallized to obtain purified intermediate 3; Step C, Intermediate 4 Preparation: Using purified intermediate 3 as a starting material, step A was repeated to couple it with the second α-amino protected amino acid Boc-AA2-OH to obtain intermediate 4 (Boc-AA2-AA1-ANT). Step D, Intermediate 5 Preparation: Using purified intermediate 4 as raw material, step B was repeated, and a Boc removal reagent was added to treat the intermediate to obtain intermediate 5 (NH2-AA2-AA1-ANT). Step E, intermediate 6 Preparation: Using purified intermediate 5 (NH2-AA2-AA1-ANT) as a starting material, it is coupled with the third α-amino protected amino acid Boc-AA3-OH; steps A and B are repeated to obtain intermediate NH2-AA3-AA2-AA1-ANT; the above steps are repeated cyclically, using the purified intermediate NH2-AA1 after the (n-1)th repetition. n-1 -X-AA3-AA2-AA1-ANT as the starting material (X is any random number of amino acids), and the nth α-amino-protected amino acid Boc-AA n -OH undergoes a coupling reaction; steps A and B are repeated to obtain intermediate 6 (Boc-AA). n -X-AA3-AA2-AA1-ANT); Step F, target peptide NH2-AA n Preparation of -X-AA3-AA2-AA1-OH: An aqueous solution of fluoroacetic acid (TFA) and triisopropylsilane (TIPS) is used as a deprotecting agent to remove intermediate 6 (Boc-AA). n Protecting groups such as tBu, Boc and Pbf on the side chain of -X-AA3-AA2-AA1-ANT) are removed, while the ANT carrier of hypophosphite derivatives is cleaved. The target peptide was neutralized with sodium bicarbonate solution to neutralize the trifluoroacetate, and the pH of the solution was adjusted to the isoelectric point of the target peptide. It was then extracted with ethyl acetate, the precipitate was obtained, and the purified target peptide was obtained by filtration, washing with ethyl acetate, and drying.

6. The method for liquid-phase synthesis of polypeptides based on the hypophosphite derivative ANT as a carrier according to claim 5, characterized in that, In step A, the molar ratio of the carrier, the α-amino protected amino acid, the dehydrating coupling agent 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI), and 4-dimethylaminopyridine (DMAP) is 1:1.5:1.8:0.12, and the reaction time is 1-4 h.

7. The method for liquid-phase synthesis of polypeptides based on the hypophosphite derivative ANT as a carrier according to claim 5, characterized in that, The volume of the weakly polar n-hexane or petroleum ether mentioned in step A is 5 to 10 times the volume of the DCM.

8. The method for liquid-phase synthesis of polypeptides based on the hypophosphite derivative ANT as a carrier according to claim 5, characterized in that, The Boc removal reagent in step B is a trifluoroacetic acid (DCM) solution with a volume ratio of 20% to 30%, the reaction temperature is 0 to 25°C, and the reaction time is 0.5 to 3 hours; the volume of the weakly polar n-hexane or petroleum ether is 5 to 10 times the volume of the DCM.

9. The method for liquid-phase synthesis of polypeptides based on the hypophosphite derivative ANT as a carrier according to claim 5, characterized in that, The deprotection reaction temperature in step F is 5–25°C, the reaction time is 1–4 h, and the volume ratio of each component in the deprotection reagent is: TFA / TIPS / H2O = 95:2.5:2.5.

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