Hexakis(X-phenoxy) cyclotriphosphazene compounds, preparation method and application in the preparation of tetrapeptide gastrin

Abstract

The present invention relates to a hexakis(X-phenoxy)cyclotriphosphazene compound, a preparation method thereof and an application thereof in the preparation of tetrapeptide gastrin, belonging to the technical field of organic synthesis. The general structural formula of the hexakis(X-phenoxy)cyclotriphosphazene compound HXPCP is as shown in formula (I). The present invention also provides a preparation method of tetrapeptide gastrin assisted by a hexakis(X-phenoxy)cyclotriphosphazene compound. The present invention uses the liquid-phase synthesis method of tetrapeptide gastrin assisted by the hexakis(X-phenoxy)cyclotriphosphazene HXPCP as a carrier, utilizes the auxiliary precipitation effect of the HXPCP carrier and the advantages of multiple reaction sites, and through a strategy of simultaneously coupling and deprotecting (Boc, Fmoc) with 6-8 equivalents of amino acids by liquid-phase reaction, optimizes and simplifies the preparation method of tetrapeptide gastrin.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic synthesis, and particularly relates to a hexakis(X-phenoxy)cyclotriphosphazene compound, a preparation method thereof, and an application thereof in the preparation of tetragastrin. Background Art

[0002] Gastrin is a gastrointestinal hormone that stimulates gastric acid secretion, first discovered by Edkins et al. Gastrin is secreted by G cells present in the mucosa of the pylorus of the stomach and the upper part of the small intestine, enters the bloodstream and then acts on the stomach, thereby promoting gastric juice secretion and nutritional effects. Through structure and function studies, Tracy and Gregory found that the entire physiological activity range of gastrin can be elucidated by the C-terminal tetrapeptide sequence Trp-Met-Asp-Phe-NH2. This tetrapeptide is the smallest fragment for natural gastrin to exert its physiological regulatory function and is called cholecystokinin tetrapeptide (CCK-4). Tetragastrin (TG) is a synthetic peptide with biological activity, and its amino acid sequence and chemical structure are identical to those of the C-terminal tetrapeptide amide of gastrin (CCK-4).

[0003] Tetragastrin has a wide range of applications. Clinically, it can replace histamine to examine the gastric acid secretion function of the human body. Compared with histamine, it has a stronger effect, fewer side effects, and an earlier peak. In terms of treatment, it can strongly promote gastric acid secretion, has a nutritional and proliferative effect on the gastric mucosa, can improve symptoms of low gastric acid and gastroptosis, and can also be used to treat atrophic gastritis and improve sequelae caused by gastrectomy, such as loss of appetite, diarrhea, etc. At the same time, it can be used for the treatment of aphthous stomatitis for a long time. However, when such N-terminal free tetrapeptides enter the bloodstream as injection drugs, they are easily catalytically degraded and inactivated by aminopeptidases in serum. In order to maintain their stability in vivo and enhance their biological activity, appropriate protecting groups are often used to block their N-terminals during design and synthesis to achieve the purpose.

[0004] The current production methods of tetragastrin mainly use traditional solution synthesis and solid-phase synthesis methods, which have problems such as cumbersome separation and purification steps, large waste of raw materials and solvents, and a large amount of resin solid waste that is difficult to degrade, resulting in serious environmental pollution. At present, there is no technology publicly available for using cyclotriphosphazene derivatives as auxiliary groups or carriers for polypeptide synthesis. Summary of the Invention

[0005] To address the deficiencies in the prior art, the present invention provides a hexakis(X-phenoxy)cyclotriphosphazene compound, a preparation method thereof, and an application thereof in the preparation of tetrapeptide gastrin. Specifically, a liquid-phase synthesis method of tetrapeptide gastrin assisted by the hexakis(X-phenoxy)cyclotriphosphazene compound (HXPCP) is mainly adopted. By utilizing the auxiliary precipitation effect of the HXPCP carrier and the advantages of multiple reaction sites, a strategy of simultaneously coupling and deprotecting (Boc, Fmoc) with 6 equivalents of amino acids through a liquid-phase reaction is employed to optimize and simplify the preparation method of tetrapeptide gastrin, verify the recyclability and reusability of the HXPCP carrier, enhance the atom economy, greenness, and scale of the tetrapeptide gastrin synthesis process, and contribute to emission reduction, energy consumption reduction, cost savings, environmental protection, and sustainable development.

[0006] The hexakis(X-phenoxy)cyclotriphosphazene compound provided by the present invention has a general structural formula as shown in formula (Ⅰ):

[0007]

[0008] (Ⅰ)

[0009] In the formula, X represents CH2Br, CH(Ar)Br, CH(R)Br, CH2NH2, CH2OH, CH2SH, CH(Ar)NH2, CH(Ar)OH, CH(Ar)SH, C(Ar)=N-OH, CH(R)NH2, CH(R)OH, CH(R)SH, CH=N-OH, OH or SH.

[0010] The present invention provides a preparation method of a hexakis(X-phenoxy)cyclotriphosphazene compound, which includes the following steps: Weigh a certain amount of hexachlorocyclotriphosphazene, dissolve it in an appropriate solvent, add 6 - 8 molar amounts of p-substituted phenol and an equimolar amount of a basic substance, stir at room temperature for 3 - 6 hours, and after the reaction ends, obtain a purified hexakis(X-phenoxy)cyclotriphosphazene compound through separation and purification.

[0011] The present invention provides an application of a hexakis(X-phenoxy)cyclotriphosphazene compound in the preparation of tetrapeptide gastrin.

[0012] The present invention provides a preparation method of tetrapeptide gastrin assisted by a hexakis(X-phenoxy)cyclotriphosphazene compound, which includes the following steps:

[0013] Step 1: Using the hexakis(X-phenoxy)cyclotriphosphazene compound as an auxiliary group, react with an N-terminal protected amino acid under the action of a coupling agent to obtain product A; subject product A to purification treatment to obtain purified product A; wherein, the N-terminal protected amino acid is phenylalanine protected with a protecting group of fluorenylmethyloxycarbonyl or tert-butoxycarbonyl.

[0014] Step 2: Treat the purified product A with a fluorenylmethyloxycarbonyl (Fmoc) removal reagent or a tert-butoxycarbonyl (Boc) removal reagent to obtain product B; subject product B to purification to obtain purified product B.

[0015] Step 3: Use purified product B as a raw material to carry out a coupling reaction with aspartic acid whose N-terminus and side-chain carboxyl group are both protected, to obtain the compound [PG-Asp(OtBu)-Phe-]6HXPCP, and then remove the N-terminal protecting group to obtain the compound [H-Asp(OtBu)-Phe-]6HXPCP.

[0016] Use the compound [H-Asp(OtBu)-Phe-]6HXPCP as a raw material, and then carry out a coupling reaction with N-terminal protected methionine to obtain the compound [PG-Met-Asp(OtBu)-Phe-]6HXPCP, and then remove the N-terminal protecting group to obtain the compound [H-Met-Asp(OtBu)-Phe-]6HXPCP.

[0017] Use the compound [H-Met-Asp(OtBu)-Phe-]6HXPCP as a raw material, and then carry out a coupling reaction with N-terminal protected tryptophan to obtain the compound [PG-Trp-Met-Asp(OtBu)-Phe-]6HXPCP.

[0018] Step 4: Remove the auxiliary group in the compound [PG-Trp-Met-Asp(OtBu)-Phe-]6HXPCP, and remove the protecting groups on the side chains, and through separation and purification, obtain the trifluoroacetate salt of tetrapeptide gastrin.

[0019] Step 5: Carry out separation and purification on the trifluoroacetate salt of tetrapeptide gastrin to obtain purified tetrapeptide gastrin.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] The present invention provides a hexa(X-phenoxy)cyclotriphosphazene compound, a preparation method and an application in the preparation of tetrapeptide gastrin. It mainly adopts a liquid-phase synthesis method of tetrapeptide gastrin assisted by hexa(X-phenoxy)cyclotriphosphazene HXPCP. Utilizing the auxiliary precipitation effect and the advantages of multiple reaction sites of the HXPCP carrier, through the strategy of simultaneously coupling and deprotecting (Boc, Fmoc) with 6 equivalents of amino acids in a liquid-phase reaction, the preparation method of tetrapeptide gastrin is optimized and simplified. The recyclability and reusability of the HXPCP carrier are verified, enhancing the atom economy, greenness and scale of the tetrapeptide gastrin synthesis process, which is beneficial to emission reduction, consumption reduction, cost saving, environmental protection and sustainable development.

[0022] The present invention uses a small molecule HXPCP to replace the resin in the existing solid-phase peptide synthesis as a carrier to assist peptide synthesis. Its advantages are that the peptide loading capacity can reach 6 equivalents, greatly improving the atomic utilization rate of the carrier. The reaction is carried out in a homogeneous (liquid phase) system, with higher reaction efficiency, saving the feeding amount of protected amino acids, reducing raw material waste and the material index PMI of the process operation. Since HXPCP can assist in the precipitation of peptide synthesis process intermediates, it simplifies the separation operation, shortens the purification process and time consumption of traditional solution peptide synthesis, and greatly improves the production efficiency. After peptide cleavage, the fragments of the auxiliary group can be recycled, reducing waste emissions, saving costs and having better environmental benefits. The reaction scale is not limited by the reactor and additional conditions, and large-scale production can be carried out to further improve production efficiency, economic benefits, environmental protection and sustainability. Detailed implementation mode

[0023] The following further elaborates on the present invention in combination with specific embodiments. It should be understood that the listed embodiments are only for facilitating the understanding of the core methods and application fields of the present invention, but the scope of the present invention is not limited thereto.

[0024] In the following various embodiments, the experimental methods and detection methods are conventional methods unless otherwise specified; the reagents and materials can be purchased on the market unless otherwise specified.

[0025] A hexakis(X-phenoxy)cyclotriphosphazene compound (HXPCP) provided by the present invention has a structural general formula shown in formula (Ⅰ):

[0026]

[0027] (Ⅰ)

[0028] In the formula, X represents CH2Br, CH(Ar)Br, CH(R)Br, CH2NH2, CH2OH, CH2SH, CH(Ar)NH2, CH(Ar)OH, CH(Ar)SH, C(Ar)=N-OH, CH(R)NH2, CH(R)OH, CH(R)SH, CH=N-OH, OH or SH.

[0029] A preparation method of a hexakis(X-phenoxy)cyclotriphosphazene compound provided by the present invention includes the following steps:

[0030] Weigh a certain amount of hexachlorocyclotriphosphazene, dissolve it in an appropriate amount of solvent, add 6 - 8 molar equivalents of para - substituted phenol and an equimolar amount of a basic substance, stir at room temperature for 3 - 6 hours, and use thin - layer chromatography to test. The newly formed spots converge into one spot, indicating that the reaction is complete. Stop the reaction and remove the solvent by rotary evaporation. Mix the residue with an appropriate amount of silica gel, elute and separate it on a silica gel column, collect and combine the fractions of the product spots, then remove the solvent by rotary evaporation again and dry it under vacuum to obtain purified hexakis(X - phenoxy)cyclotriphosphazene compound HXPCP;

[0031] The para - substituent X of the phenol is one of CH2Br, CH(Ar)Br, CH(R)Br, CH2NH2, CH2OH, CH2SH, CH(Ar)NH2, CH(Ar)OH, CH(Ar)SH, C(Ar)=N - OH, CH(R)NH2, CH(R)OH, CH(R)SH, CH=N - OH, OH or SH;

[0032] The solvent refers to one or several of chloroform, dichloromethane, tetrahydrofuran, acetonitrile, N, N - dimethylformamide, benzene or aromatic hydrocarbon solvents;

[0033] The basic substance refers to one or several of hydroxides or carbonates of alkali metals or alkaline earth metals such as sodium hydroxide (or lithium or potassium or calcium or magnesium, etc.), sodium carbonate (or lithium or potassium or calcium or magnesium, etc.), and organic tertiary amines such as triethylamine, diisopropylethylamine, DBU, DMAP, MMP, etc.

[0034] The present invention provides an application of hexakis(X - phenoxy)cyclotriphosphazene compounds in the preparation of tetrapeptide gastrin.

[0035] The present invention provides a preparation method of tetrapeptide gastrin assisted by hexakis(X - phenoxy)cyclotriphosphazene compounds, comprising the following steps:

[0036] Step 1: Using hexakis(X - phenoxy)cyclotriphosphazene compounds as auxiliary groups, react with N - terminal protected amino acids under the action of a coupling agent to obtain product A; subject product A to purification treatment to obtain purified product A;

[0037] Among them, the N - terminal protected amino acid is phenylalanine (PG - Phe - OH) protected by a protecting group (PG) of fluorenylmethoxycarbonyl (Fmoc) or tert - butyloxycarbonyl (Boc);

[0038] In one embodiment, the resin in solid-phase polypeptide synthesis is replaced with an auxiliary group HXPCP, and it is stirred and reacted with an N-terminal protected amino acid at 0 to 50 °C for 1 to 3 hours under the action of a coupling agent to obtain product A; the molar ratio of the amino acid to the HXPCP auxiliary group is 6 to 7:1; the coupling agent is a dehydration coupling activator and a basic substance with a molar ratio of 6 to 7:1;

[0039] The auxiliary group is hexakis(X-phenoxy)cyclotriphosphazene HXPCP;

[0040] The amino acid used is phenylalanine (PG-Phe-OH) protected by a protecting group (PG) of fluorenylmethyloxycarbonyl (Fmo) or tert-butoxycarbonyl (Boc). The C-terminus of the protected phenylalanine (PG-Phe-OH) is connected to the HXPCP auxiliary group to generate compound A, (PG-Phe-)6HXPCP.

[0041] Among them, during the purification process of product A, a small-polarity alkane or ether solvent is added to product A, and by virtue of the property that the HXPCP auxiliary group is easily crystallized and precipitated in the solvent system, product A is separated from other impurities;

[0042] The separated product A is filtered, washed or recrystallized to obtain purified product A;

[0043] Step 2, the purified product A is treated with a de-fluorenylmethyloxycarbonyl reagent or a de-tert-butoxycarbonyl reagent to obtain product B; the product B is purified to obtain purified product B;

[0044] In one embodiment, the N-terminal protecting group PG is removed: the purified product A is treated with a de-Fmoc reagent and stirred and reacted at 10 to 50 °C for 0.5 to 2 hours, or treated with a de-Boc reagent and stirred and reacted at 10 to 50 °C for 0.5 to 2 hours to obtain product B, (H-Phe-)6HXPCP;

[0045] A small-polarity alkane or ether solvent is added to product B, and by virtue of the property that the HXPCP auxiliary group is easily crystallized and precipitated in the solvent system, product B is separated from other impurities;

[0046] The separated product B is filtered, washed or recrystallized to obtain purified product B;

[0047] It should be noted that when the protecting group PG is Fmoc, the product A is treated with a de-Fmoc reagent. When PG is Boc, the product A is treated with a de-Boc reagent. Then, by virtue of the property that phosphate esters are prone to crystallization and precipitation in different solvent systems, the product B can be separated from other impurities, and the purified product B can be obtained through simple filtration, washing, or recrystallization operations.

[0048] Step 3: Using the purified product B as a raw material, it is coupled with aspartic acid PG-Asp(OtBu)-OH in which both the N-terminus and the side-chain carboxyl group are protected to obtain the compound [PG-Asp(OtBu)-Phe-]6HXPCP, and then the N-terminal protecting group is removed to obtain the compound [H-Asp(OtBu)-Phe-]6HXPCP;

[0049] Using the compound [H-Asp(OtBu)-Phe-]6HXPCP as a raw material, it is further coupled with N-terminal protected methionine to obtain the compound [PG-Met-Asp(OtBu)-Phe-]6HXPCP, and then the N-terminal protecting group is removed to obtain the compound [H-Met-Asp(OtBu)-Phe-]6HXPCP;

[0050] Using the compound [H-Met-Asp(OtBu)-Phe-]6HXPCP as a raw material, it is further coupled with N-terminal protected tryptophan to obtain the compound [PG-Trp-Met-Asp(OtBu)-Phe-]6HXPCP;

[0051] It should be noted that Step 3 mainly involves repeating the above Steps 1 and 2 to sequentially couple with N-terminal and side-chain protected aspartic acid [PG-Asp(OtBu)-OH], methionine [PG-Met-OH], and tryptophan [PG-Trp-OH], and performing the de-PG reaction to prepare the precursor C of tetrapeptide gastrin, [PG-Trp-Met-Asp(OtBu)-Phe-]6HXPCP.

[0052] Among them, in this Step 3, the N-terminal protecting groups involved in N-terminal and side-chain protected aspartic acid [PG-Asp(OtBu)-OH], methionine [PG-Met-OH], and tryptophan [PG-Trp-OH] include fluorenylmethyloxycarbonyl (Fmoc) or tert-butoxycarbonyl (Boc); and the removal of the N-terminal protecting group is carried out by treatment with a de-fluorenylmethyloxycarbonyl reagent or a de-tert-butoxycarbonyl reagent. The side-chain protecting group is OtBu. For Boc-Asp(OFm)-OH in which both the N-terminus and the side-chain carboxyl group of aspartic acid are protected, the N-terminal protecting group on aspartic acid is Boc, and the side-chain carboxyl protecting group is OFm.

[0053] Step 4: Remove the auxiliary group in the compound [PG-Trp-Met-Asp(OtBu)-Phe-]6HXPCP and remove the protecting groups of the side chains. After separation and purification, the trifluoroacetate salt of tetrapeptide gastrin is obtained.

[0054] Specifically, using a 25% ammonia solution in tetrahydrofuran as the shearing agent, first remove and separate the auxiliary group from the compound [PG-Trp-Met-Asp(OtBu)-Phe-]6HXPCP, and then use a cocktail solution of trifluoroacetic acid as the side chain deprotecting agent to remove the protecting groups on the side chains. After separation and purification, the trifluoroacetate salt of tetrapeptide gastrin is obtained.

[0055] In one embodiment, removing the carrier and deprotecting the side chains: Using a 25% ammonia solution in tetrahydrofuran as the shearing agent, first remove and separate the HXPCP auxiliary group. Then use a cocktail solution of trifluoroacetic acid as the side chain deprotecting agent. The reaction conditions are stirring at 5 - 30°C for 1 - 3 hours to remove the protecting groups such as tBu and Boc on the side chains, and at the same time remove the HXPCP auxiliary group. After separation and purification, a white solid of the trifluoroacetate salt of tetrapeptide gastrin, [TFA*H-Trp-Met-Asp-Phe-OH], is obtained; the component ratio in the cocktail solution of trifluoroacetic acid is: TFA / TIPS / H2O = 95:2.5:2.5.

[0056] Step 5: Separate and purify the trifluoroacetate salt of tetrapeptide gastrin to obtain purified tetrapeptide gastrin.

[0057] In one embodiment, the process of separating and purifying the trifluoroacetate salt of tetrapeptide gastrin includes: recovering the trifluoroacetate salt of tetrapeptide gastrin by rotary evaporation, neutralizing the residual solution with sodium bicarbonate, adjusting the pH to 8 - 9, extracting with ethyl acetate, precipitating, and obtaining purified tetrapeptide gastrin after filtration, washing with ethyl acetate, and drying.

[0058] Among them, the ethyl acetate extraction solution obtained is rotary evaporated and concentrated to 1 / 3 - 1 / 4 of the original volume, and an alkane or ether solvent is added. By virtue of the characteristic that the auxiliary group is easily crystallized and precipitated in different solvent systems, the auxiliary group can be separated from other impurities; the separated auxiliary group is filtered, washed, or recrystallized to obtain a purified auxiliary group, which can be reused directly or after regeneration as an auxiliary group.

[0059] In one embodiment, the general structural formula of the product B is:

[0060]

[0061] In the formula, X represents CH2Br, CH(Ar)Br, CH(R)Br, CH2NH2, CH2OH, CH2SH, CH(Ar)NH2, CH(Ar)OH, CH(Ar)SH, C(Ar)=N-OH, CH(R)NH2, CH(R)OH, CH(R)SH, CH=N-OH, OH or SH;

[0062] PG represents Fmoc, Boc or H.

[0063] In one embodiment, the general structural formula of the compound [PG-Asp(OtBu)-Phe-]6HXPCP is:

[0064]

[0065] In the formula, X represents CH2Br, CH(Ar)Br, CH(R)Br, CH2NH2, CH2OH, CH2SH, CH(Ar)NH2, CH(Ar)OH, CH(Ar)SH, C(Ar)=N-OH, CH(R)NH2, CH(R)OH, CH(R)SH, CH=N-OH, OH or SH;

[0066] PG represents Fmoc, Boc or H.

[0067] In one embodiment, the general structural formula of the compound [PG-Met-Asp(OtBu)-Phe-]6HXPCP is:

[0068]

[0069] In the formula, X represents CH2Br, CH(Ar)Br, CH(R)Br, CH2NH2, CH2OH, CH2SH, CH(Ar)NH2, CH(Ar)OH, CH(Ar)SH, C(Ar)=N-OH, CH(R)NH2, CH(R)OH, CH(R)SH, CH=N-OH, OH or SH;

[0070] PG represents Fmoc, Boc or H.

[0071] In one embodiment, the general structural formula of the compound [PG-Trp-Met-Asp(OtBu)-Phe-]6HXPCP is:

[0072]

[0073] In the formula, X represents CH2Br, CH(Ar)Br, CH(R)Br, CH2NH2, CH2OH, CH2SH, CH(Ar)NH2, CH(Ar)OH, CH(Ar)SH, C(Ar)=N-OH, CH(R)NH2, CH(R)OH, CH(R)SH, CH=N-OH, OH or SH;

[0074] PG represents Fmoc, Boc, Cbz or H.

[0075] The following examples provide specific synthetic methods for preparing the above compounds and the corresponding intermediate compounds.

[0076] Example 1

[0077] A preparation method of hexakis(4-methoxyphenoxy)cyclotriphosphazene (HMPCP), comprising:

[0078] Accurately weigh 5.59 g (45 mmol, 9 eq) of p-methoxyphenol, place it in a 250 mL round-bottom flask, add 100 mL of THF to dissolve it completely, add 1.8 g (45 mmol, 9 eq) of NaOH, stir at room temperature for 0.5 h, dissolve 1.74 g (5 mmol, 1 eq) of hexachlorocyclotriphosphazene in 50 mL of THF, and dropwise add it to the reaction system. After the addition is complete, raise the reaction temperature to 70 °C and reflux for 24 h. Monitor by TLC, developing solvent: PE:EA = 2:1. After the reaction is completed, filter to remove the NaCl generated during the reaction, and concentrate under reduced pressure to remove THF. Add 80 mL of ethyl acetate to completely dissolve the reaction mixture, wash it three times with saturated Na2CO3 solution, and finally recrystallize with dichloromethane to obtain the product as a white solid with a yield of 95%.

[0079] Hexakis(4-methoxyphenoxy)cyclotriphosphazene (C 42 H 42 N3O 12 P3) structure characterization data: 1 H NMR (400 MHz, DMSO- d 6) δ 7.18 (d, J = 9.0 Hz, 6H), 6.98 (d, J = 9.1 Hz, 6H), 3.75 (s, 9H); 13 CNMR (101 MHz, DMSO- d 6) δ 157.22, 143.90, 121.37, 115.44, 55.93; 3131P NMR (162 MHz, DMSO- d 6) δ -15.73; HRMS (ESI) m / z calcd for C 42 H 43 N3O 12 P3 + (M+H) + = 874.20541, found 874.20538.

[0080] Example 2

[0081] Preparation method of hexakis(4-hydroxyphenoxy)cyclotriphosphazene (HHPCP), comprising:

[0082] Accurately weigh 1.97 g (2.25 mmol, 1 eq) of hexakis(4-methoxyphenoxy)cyclotriphosphazene, add 50 mL of dichloromethane to completely dissolve it, take 1.3 mL (13.52 mmol, 6 eq) of BBr3 in a fume hood, slowly drop it into 50 mL of dichloromethane and stir continuously, then dropwise add it to the reaction solution, react at room temperature, a white precipitate gradually appears during the reaction, monitor the reaction by TLC, eluent: DCM:MeOH = 10:1, the reaction is completed in about 1.5 h, concentrate under reduced pressure to remove the solvent, add 100 mL of distilled water and stir for 1 h, centrifuge and wash three times with distilled water, and obtain 1.74 g of the product as a white solid after vacuum drying, with a yield of 98%.

[0083] Structural characterization data of hexakis(4-hydroxyphenoxy)cyclotriphosphazene (C 36 H 30 N3O 12 P3): 1 1H NMR (400 MHz, DMSO- d 6) δ 9.43 (s, 6H), 6.64 (q, J J = 9.1 Hz, 24H); 13 13C NMR (101 MHz, DMSO- d 6) δ 154.92, 142.91, 121.92, 116.15; 31 31P NMR (162 MHz, DMSO- d 6) δ 10.07; HRMS (ESI) m / z calcd for C 36 H 31 N3O 12 P3 + (M+H) +=790.11151, found 790.11145.

[0084] Example 3

[0085] The synthetic route of hexakis(4-phenylalanyloxy-phenoxy)cyclotriphosphazene, (H-Phe)6-HHPCP is as follows:

[0086]

[0087] The specific preparation method includes:

[0088] Synthesis of hexakis(4-tert-butoxycarbonyl-phenylalanyloxy-phenoxy)cyclotriphosphazene (Boc-Phe)6-HHPCP:

[0089] Accurately weigh 10.92 g (41.15 mmol, 7.2 eq) of Boc-Phe-OH, 7.89 g (41.15 mmol, 7.2 eq) of EDCI, and 0.50 g (4.12 mmol, 0.72 eq) of DMAP, and add them to 50 mL of DCM in sequence. After they are fully dissolved, activate them in an ice bath for 0.5 h, add 4.51 g (5.72 mmol, 1 eq) of the carrier HHPCP, then immediately place it in an ice-water bath and react at room temperature. Monitor the whole process by TLC. The reaction should be complete in about 1 h. After the reaction is completed, concentrate under reduced pressure to remove DCM, then add 50 mL of ethyl acetate to completely dissolve the reaction mixture, and wash it 3 times with 100 mL of saturated NH4Cl solution, water, saturated NaHCO3 solution, and water in sequence. Dry it with anhydrous Na2SO4, concentrate under reduced pressure to remove ethyl acetate, then add 5 mL of ethyl acetate to dissolve it, and dropwise add n-hexane while ultrasonically vibrating. Precipitation will gradually occur as n-hexane is added dropwise. Observe by TLC after standing until the supernatant does not contain the target product. Filter and collect the precipitate, and dry it under vacuum to obtain a white solid with a yield of 95%. Developing agent: PE:EA = 3:1.

[0090] Structure characterization data of (Boc-Phe)6-HHPCP: 1 H NMR (400 MHz, DMSO- d 6) δ 7.56 (d, J J = 7.3 Hz, 6H), 7.33 – 7.20 (m, 30H), 6.98 (s, 24H), 4.59 – 4.34 (m, 6H), 3.22 –3.03 (m, 12H), 1.35 (s, 54H); 13 C NMR (101 MHz, DMSO- d6) δ 171.51, 156.00,147.92, 147.67, 137.69, 129.70, 128.72, 127.04, 123.27, 122.03, 79.03, 55.94,55.35, 39.99, 36.76, 28.56; 31 P NMR (162 MHz, DMSO- d 6) δ 29.47; HRMS (ESI) m / z calcd for C 120 H 132 N9O 30 P3Na + (M+Na) + 2295.82187 , found 2295.82593.

[0091] Synthesis of hexakis(4-phenylalanyloxyphenoxy)cyclotriphosphazene, (H-Phe)6-HHPCP: Take 11.53 g of (Boc-Phe)6-HHPCP and put it into a 100 mL round-bottom flask. Add 21 mL of DCM to dissolve it completely. Place the system in an ice-water bath and stir for 10 min to lower the system temperature to the lowest. Dropwise add 7 mL of trifluoroacetic acid (V DCM :V TFA = 3:1). After dropping, remove the ice-water bath and react at room temperature. Monitor by TCL. The deprotection is complete in about 1 h. After the reaction, concentrate under reduced pressure at room temperature to remove DCM and TFA, and add DCM multiple times for concentration under reduced pressure to remove TFA to the greatest extent. It should be noted that since the product after de-Boc is unstable, it does not need to be purified and should be immediately put into the next reaction. After concentration under reduced pressure, a pale yellow foamy solid is obtained with a yield of 99%.

[0092] (H-Phe)6-HHPCP structural characterization data: 1 H NMR (400 MHz, DMSO- d 6) δ 9.01 – 8.78(m, 12H), 7.38 – 7.25 (m, 30H), 7.07 – 6.90 (m, 24H), 4.57 (t, J = 6.9 Hz, 6H),3.34 (dd, J = 13.8, 6.0 Hz, 6H), 3.26 – 3.16 (m, 6H); 13 C NMR (101 MHz, DMSO- d6) δ 168.37, 147.11, 135.06, 129.97, 129.13, 127.86, 123.10, 54.02, 36.64; 31 P NMR (162 MHz, DMSO- d 6) δ 8.32; HRMS (ESI) m / z calcd for C 90 H 86 N9O 18 P3 2+ (M + 2H) 2+ 836.76463, found 836.76440.

[0093] Example 4

[0094] The synthetic route of hexa[4-(9-fluorenylmethoxycarbonylmethyl)aspartyl-phenylalanyloxy-phenoxy]cyclotriphosphazene, [H-Asp(OFm)-Phe]6-HHPCP is as follows:

[0095]

[0096] The specific preparation method includes:

[0097] Synthesis of hexa(4-tert-butoxycarbonyl-(9-fluorenylmethoxycarbonylmethyl)aspartyl-phenylalanyloxy-phenoxy)cyclotriphosphazene (Boc-Asp(OFm)-Phe)6-HHPCP: The specific operation is the same as that of Boc-Asp(OtBu)-Phe-HHPCP, only replacing Boc-Asp(OtBu)-OH with Boc-Asp(OFm)-OH, and the yield is 95%. React 6 - 7 equivalents of Boc-Asp(OFm)-OH with 1 equivalent of (H-Phe)6-HHPCP, and [Boc-Asp(OFm)-Phe]6-HHPCP is obtained after separation and purification.

[0098] (Boc-Asp(OFm)-Phe)6-HHPCP structure characterization data: 1 H NMR (400 MHz, DMSO- d 6) δ 8.62 – 8.49 (m, 6H), 7.88 (d, J = 16.1 Hz, 12H), 7.67 – 7.61 (m, 12H), 7.44 – 7.21 (m, 60H), 6.97 (s, 18H), 4.80 – 4.68 (m, 6H), 4.54 – 4.39 (m, 6H), 4.25(dd, J= 29.9, 7.5 Hz, 18H), 3.20 (s, 12H), 2.71 (s, 12H), 1.33 (s, 54H); 13 C NMR(101 MHz, DMSO- d 6) δ 171.79, 170.59, 155.67, 147.83, 141.10, 137.27, 129.77,128.76, 128.20, 127.62, 127.14, 125.69, 123.34, 121.86, 120.59, 78.82, 66.52,60.23, 55.36, 54.43, 51.17, 46.57, 28.56; 31 P NMR (162 MHz, DMSO-d6) δ 8.66;HRMS (ESI) m / z calcd for C 228 H 224 N 15 O 48 P3 2+ (M+2H) 2+ 2017.24086, found 2017.24390.

[0099] Synthesis of hexakis[4-(9-fluorenylmethoxycarbonylmethyl ester)aspartyl-phenylalanyloxy-phenoxy]cyclotriphosphazene, [H-Asp(OFm)-Phe]6HHPCP:

[0100] Take 12.43 g of (Boc-Asp(OFm)-Phe)6-HHPCP and put it into a 100 mL round-bottom flask. Add 15 mL of DCM to dissolve it completely. Place the system in an ice-water bath and stir for 10 min to lower the temperature of the system to the lowest. Dropwise add 5 mL of trifluoroacetic acid (V DCM :V TFA = 3:1). After dropping, remove the ice-water bath and react at room temperature. Monitor by TCL. The deprotection is complete in about 1 h. After the reaction, concentrate under reduced pressure at room temperature to remove DCM and TFA, and add DCM multiple times for concentration under reduced pressure to remove TFA to the greatest extent. After concentration under reduced pressure, a white foamy solid is obtained with a yield of 96%.

[0101] Structure characterization data of (H-Asp(OFm)-Phe)6-HHPCP: 1 H NMR (400 MHz, DMSO- d 6) δ 9.23(t, J= 7.2 Hz, 6H), 8.40 (s, 12H), 7.96 – 7.82 (m, 12H), 7.70 – 7.55 (m, 12H), 7.47 – 6.91 (m, 72H), 4.90 – 4.18 (m, 30H), 3.31 – 2.59 (m, 24H); 13 C NMR (101MHz, DMSO- d 6) δ 170.07, 169.64, 168.32, 147.66, 143.92, 143.84, 141.12, 136.85, 129.68, 128.88, 128.25, 125.53, 123.26, 121.88, 120.64, 67.01, 55.37, 54.68, 48.99, 46.37, 36.69, 35.65; 31 P NMR (162 MHz, DMSO- d 6) δ 8.40; HRMS(ESI) m / z calcd for C 198 H 176 N 15 O 36 P3 2+ (M+2H) 2+ 1717.08357, found 1717.08374.

[0102] Example 5

[0103] The synthetic route of hexakis(4-methionyl-(9-fluorenylmethoxycarbonylmethyl)aspartyl-phenylalanyloxy-phenoxy)cyclotriphosphazene, (H-Met-Asp(OFm)-Phe)6-HHPCP is as follows:

[0104]

[0105] The specific preparation method includes:

[0106] Synthesis of hexakis(4-tert-butoxycarbonyl-methionyl-(9-fluorenylmethoxycarbonylmethyl)aspartyl-phenylalanyloxy-phenoxy)cyclotriphosphazene, (Boc-Met-Asp(OFm)-Phe)6-HHPCP:

[0107] Accurately weigh 2.76 g (14.38 mmol, 7.2 eq) of EDCI, 1.94 g (14.38 mmol, 7.2 eq) of HOBt, and 3.59 g (14.38 mmol, 7.2 eq) of Boc-Met-OH and add them successively to a 100 mL round-bottom flask. Add 30 mL of DCM to completely dissolve them, seal and stir to activate for 0.5 h in an ice bath. Add 6.85 g (1.99 mmol, 1.0 eq) of (H-Asp(OFm)-Phe)6-HHPCP and 2.377 mL (12.24 mmol, 3.0 eq) of DIEA to the activated solution, and place it at room temperature for reaction for 2 h. Monitor the reaction process by TLC (developing agent: PE:EA = 1:1). After the reaction is completed, concentrate under reduced pressure to remove dichloromethane, then add 50 mL of ethyl acetate to dissolve the reaction mixture, and wash it successively with 30 mL of saturated NH4Cl solution, distilled water, saturated NaHCO3 solution, and distilled water 3 times, and dry it with anhydrous Na2SO4. Precipitate it with an ethyl acetate / n-hexane system to obtain a white solid with a yield of 82%.

[0108] Structural characterization data of (Boc-Met-Asp(OFm)-Phe)6-HHPCP (Compound 70): 1 H NMR (400 MHz, DMSO- d 6) δ 8.60 (s, 6H), 8.33 – 8.15 (m, 6H), 7.92 – 7.81 (m, 12H), 7.61 (s,12H), 7.41 – 7.13 (m, 60H), 6.94 (dd, J = 17.9, 9.9 Hz, 24H), 4.82 – 4.63 (m,12H), 4.20 (s, 12H), 4.07 – 3.96 (m, 12H), 2.73 (dt, J = 37.5, 17.9 Hz, 16H),2.42 (s, 20H), 2.00 (d, J = 30.4 Hz, 30H), 1.39 (s, 54H); 13 C NMR (101 MHz, DMSO- d6) δ 172.13, 171.04, 170.40, 147.73, 143.99, 141.08, 137.10, 129.69, 128.79, 128.18, 127.78, 127.60, 127.19, 125.60, 124.99, 123.25, 121.84, 120.55, 78.73, 78.55, 66.52, 54.57, 54.00, 52.85, 49.56, 46.51, 36.80, 36.46, 32.14, 30.88, 30.31, 30.05, 28.61, 15.00; 31 P NMR (162 MHz, DMSO- d 6) δ 8.63; HRMS(ESI) m / z calcd for C 258 H 278 N 21 O 54 P3S6 2+ (M+2H) 2+ 2410.36231, found 2410.36108.

[0109] Synthesis of hexakis(4-methionyl-(9-fluorenylmethoxycarbonylmethyl)aspartyl-phenylalanyloxy-phenoxy)cyclotriphosphazene, (H-Met-Asp(OFm)-Phe)6-HHPCP: 12.43 g of (Boc-Asp(OFm)-Phe)6-HHPCP was placed in a 100 mL round-bottom flask, 15 mL of DCM was added to dissolve it completely. The system was placed in an ice-water bath and stirred for 10 min to lower the temperature of the system to the lowest. 5 mL of trifluoroacetic acid (V DCM :V TFA =3:1) was added dropwise. After the addition, the ice-water bath was removed and the reaction was carried out at room temperature. Monitored by TLC, the deprotection was complete in about 1 h. After the reaction, DCM and TFA were removed by concentration under reduced pressure at room temperature, and DCM was added repeatedly for concentration under reduced pressure to remove TFA to the greatest extent. A white foamy solid was obtained after concentration under reduced pressure, and the yield was 96%.

[0110] (H-Met-Asp(OFm)-Phe)6-HHPCP (Compound 71) Structural Characterization Data: 1 H NMR (400 MHz, DMSO- d 6) δ 8.92 (s, 12H), 8.30 (s, 12H), 7.97 – 7.78 (m, 12H), 7.63 (d, J= 10.2 Hz, 12H), 7.32 (dt, J = 44.8, 11.1 Hz, 48H), 7.07 – 6.83 (m, 24H), 4.84 – 4.19 (m, 30H), 4.05 – 2.55 (m, 48H), 2.03 – 1.89 (m, 30H); 13 C NMR (101 MHz, DMSO- d 6) δ 171.19, 170.71, 170.50, 170.15, 168.56, 147.76, 143.95 (d, J = 5.8Hz), 141.13, 137.16, 129.68, 128.79, 128.22, 127.61, 125.59, 123.27, 121.85, 120.61, 67.47, 54.61, 52.03, 51.44, 49.74, 46.50, 39.74, 39.53, 14.85; 31 P NMR(162 MHz, DMSO- d 6) δ 8.51; HRMS (ESI) m / z calcd for C 228 H 230 N 21 O 42 P3S6 2+ (M + 2H) 2+ 2110.20502, found 2110.20313.

[0111] Example 6

[0112] The synthetic route of hexakis(4-benzyloxycarbonyl - tryptophanyl - methionyl - (9 - fluorenylmethoxycarbonyl methyl ester) aspartyl - phenylalanyloxy - phenoxy) cyclotriphosphazene, (Cbz - Trp - Met - Asp(OFm) - Phe)6 - HHPCP is as follows:

[0113]

[0114] (Synthesis of (Cbz-Trp-Met-Asp(OFm)-Phe)6-HHPCP: Weigh accurately 2.14 g (11.16 mmol, 7.2 eq) of EDCI, 1.51 g (11.16 mmol, 7.2 eq) of HOBt, 3.78 g (11.16 mmol, 7.2 eq) of Cbz-Trp-OH, and 3.07 mL (18.61 mmol, 12 eq) of DIEA, and add them successively to a 100 mL round-bottom flask. Add 40 mL of DCM to dissolve them completely. Seal and stir the mixture in an ice bath for activation for 0.5 h. Add 6.54 g (1.55 mmol, 1.0 eq) of (H-Met-Asp(OFm)-Phe)6-HHPCP to the activated solution, and place it at room temperature for reaction for 3 h. During the reaction, solids gradually precipitate out, and the target product is detected by TLC monitoring the reaction process (developing agent: DCM:MeOH = 20:1). After the reaction is completed, filter, dry the solid, concentrate the filtrate, and the product continuously precipitates out. Filter and dry it to finally obtain a white powder with a yield of 83%.

[0115] (Structural characterization data of (Cbz-Trp-Met-Asp(OFm)-Phe)6-HHPCP (Compound 72): 1 H NMR (400 MHz, DMSO-d6) δ 10.82 (s, 6H), 8.71 – 8.19 (m, 18H), 7.81 (s, 12H), 7.58 (d, J = 28.1 Hz, 18H), 6.98 (d, J = 45.4 Hz, 138H), 4.97 – 4.65 (m, 24H), 4.45 – 4.14 (m, 30H), 3.13 (d, J = 26.3 Hz, 18H), 2.98 – 2.67 (m, 18H), 2.40 (s, 12H), 1.94 (d, J = 12.6 Hz, 30H); 13 C NMR (101 MHz, DMSO- d6) δ 172.56, 171.43, 171.03, 170.51, 156.37, 147.73, 143.95, 137.35, 136.53, 129.72, 128.14, 127.93, 125.60, 124.31, 123.28, 121.86, 121.83, 121.28, 120.55, 119.04, 118.61, 111.74, 110.57, 66.56, 65.75, 55.98, 52.41, 46.48, 32.37 (d, J = 4.5 Hz), 29.83, 27.99, 15.11; 31 1P NMR (162 MHz, DMSO- d 6) δ 8.51.

[0116] Example 7

[0117] Synthesis of Tetrapeptide Gastrin (Amine Cleavage)

[0118] For (Cbz-Trp-Met-Asp(OFm)-Phe)6-HHPCP provided in Example 6, an ammonolysis reaction was selected to cleave the carrier, and the cleavage route was as follows:

[0119]

[0120] The specific preparation method was as follows:

[0121] Take 94.5 mg of (Cbz-Trp-Met-Asp(OFm)-Phe)6-HHPCP, dissolve it in 20 mL of tetrahydrofuran, stir at room temperature, add 1 mL of ammonia water dropwise to the reaction system. The reaction solution immediately became clear after adding ammonia water. Monitor the reaction by TLC (developing agent: DCM:MeOH = 10:1). The carrier and the OFm group were removed simultaneously. The reaction was completed in about 4 h. Concentrate under reduced pressure to remove the solvent, add ethyl acetate for recrystallization to obtain tetrapeptide gastrin as a white powder with a yield of 62%. At the same time, the recovered HHPCP carrier was obtained with a carrier yield of 68%. The structural characterization data of the recovered HHPCP was completely consistent with the HHPCP raw material before the coupling reaction and could be directly reused as a carrier for polypeptide synthesis. It saves raw material costs, reduces waste discharge, improves efficiency, and is conducive to environmental protection and sustainable development.

[0122] Structural Characterization Data of N-Carbobenzoxy Tetrapeptide Gastrin Cbz-TG: 11H NMR (400 MHz, DMSO-d6) δ 10.98 (s, 1H), 8.44 – 8.25 (m, 2H), 8.25 – 8.15 (m, 1H), 7.73 – 7.61 (m, 2H), 7.42 (d, J J = 8.2 Hz, 1H), 7.37 – 7.10 (m, 12H), 7.09 – 6.92 (m, 3H), 4.94 (s, 2H), 4.49 – 4.27 (m, 4H), 3.10 (d, J J = 10.5 Hz, 2H), 2.98 – 2.77 (m, 3H), 2.44– 2.29 (m, 3H), 2.00 (s, 5H); 31 31P NMR (162 MHz, DMSO- d d6) δ No peak; HRMS (ESI) m / z calcd for C 37 21H 42 N6O8SNa + (M+Na) + 753.26770, found 753.26733.

[0123] Treatment with liquid HF at 0 °C for 10 - 30 minutes can completely remove Cbz to obtain the tetrapeptide gastrin TG. FSO3H, CH3SO3H, CF3SO3H, and C6H5SCH3-TFA are also good Cbz-removing reagents. Me3SiI can selectively remove Cbz and Boc protecting groups within a few minutes in chloroform and acetonitrile. For BBr3 / CH2Cl2, larger molecular peptide Cbz derivatives can be removed in TFA because the peptide has a higher solubility in acid than in CH2Cl2. To remove Cbz from the peptide chain, 0.5 M 4-(methylthio)phenol can be added to TFA or HF / Me2S / p-cresol (25:65:10, v / v) can be used to inhibit the addition of benzyl cation (Bn + +) to aromatic amino acids. In addition, there are some less commonly used methods as follows. Such as HCl / CHCl3, HCl / HOAc, HBr / SO2, HBr solution, TosOH, HI / HOAc, phosphorus iodide, Et3SiH, boiling TFA, ethanol solution of 8 M HCl or refluxing 6 M HCl for 1 hour, or heating with concentrated hydrochloric acid at 25 - 75 °C for 1 - 1.5 hours, etc.

[0124] The present invention uses a small molecule HXPCP to replace the resin in the existing solid-phase peptide synthesis as a carrier for assisting peptide synthesis. Its advantages are that the peptide loading capacity can reach 6 equivalents, greatly improving the atomic utilization rate of the carrier. The reaction is carried out in a homogeneous (liquid phase) system, with higher reaction efficiency, saving the feeding amount of protected amino acids, reducing raw material waste and the process operation material index PMI. Since HXPCP can assist in the precipitation of peptide synthesis process intermediates, simplifying the separation operation, shortening the purification process and time consumption of traditional solution peptide synthesis, and greatly improving the production efficiency. After peptide cleavage, the fragments of the auxiliary group can be recycled, reducing waste emissions, saving costs, and having better environmental benefits. The reaction scale is not limited by the reactor and additional conditions, and large-scale production can be carried out, further improving production efficiency, economic benefits, environmental protection and sustainability.

[0125] The above embodiments are only some of the embodiments listed for facilitating the understanding of the synthesis and application methods of the materials of the present invention, and are not used to limit the present invention. It can be understood that relevant practitioners can easily make appropriate modifications to this structure. Therefore, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Use of a hexakis(X-phenoxy)cyclotriphosphazene compound in the preparation of tetrapeptide gastrin, characterized in that, The general structural formula of hexakis(X-phenoxy)cyclotriphosphazene compounds is shown in Formula (I): （Ⅰ） In the formula, X represents OH.

2. A preparation method of tetrapeptide gastrin assisted by a hexakis(X-phenoxy) cyclotriphosphazene compound, characterized in that, It includes the following steps: Step 1: Using hexakis(X-phenoxy)cyclotriphosphazene compounds as auxiliary groups, reacting with N-terminal protected amino acids under the action of a coupling agent to obtain product A; purifying product A to obtain purified product A; wherein, the N-terminal protected amino acid is phenylalanine protected by a protecting group of fluorenylmethyloxycarbonyl or tert-butoxycarbonyl; Step 2: Treating purified product A with a fluorenylmethyloxycarbonyl removing reagent or a tert-butoxycarbonyl removing reagent to obtain product B; purifying product B to obtain purified product B; Step 3: Using purified product B as a raw material, carrying out a coupling reaction with aspartic acid whose N-terminal and side-chain carboxyl groups are both protected to obtain compound [PG-Asp(OtBu)-Phe-]6HXPCP, and then removing the N-terminal protecting group to obtain compound [H-Asp(OtBu)-Phe-]6HXPCP; Using compound [H-Asp(OtBu)-Phe-]6HXPCP as a raw material, and then carrying out a coupling reaction with N-terminal protected methionine to obtain compound [PG-Met-Asp(OtBu)-Phe-]6HXPCP, and then removing the N-terminal protecting group to obtain compound [H-Met-Asp(OtBu)-Phe-]6HXPCP; Using compound [H-Met-Asp(OtBu)-Phe-]6HXPCP as a raw material, and then carrying out a coupling reaction with N-terminal protected tryptophan to obtain compound [PG-Trp-Met-Asp(OtBu)-Phe-]6HXPCP; Step 4: Removing the auxiliary group in compound [PG-Trp-Met-Asp(OtBu)-Phe-]6HXPCP, and removing the protecting groups of the side chains, and through separation and purification, obtaining the trifluoroacetate salt of tetrapeptide gastrin; Step 5: Separating and purifying the trifluoroacetate salt of tetrapeptide gastrin to obtain purified tetrapeptide gastrin; The general structural formula of hexakis(X-phenoxy)cyclotriphosphazene compounds is shown in Formula (I): （Ⅰ） In the formula, X represents OH.

3. The preparation method of the tetrapeptide gastrin assisted by the hexakis(X-phenoxy) cyclotriphosphazene compound according to claim 2, characterized in that, The general structural formula of product B is: In the formula, X represents O; PG represents Fmoc, Boc or H.

4. The preparation method of tetrapeptide gastrin assisted by hexakis(X-phenoxy) cyclotriphosphazene compounds according to claim 2, characterized in that, The general structural formula of compound [PG-Asp(OtBu)-Phe-]6HXPCP is: In the formula, X represents O; PG represents Fmoc, Boc or H.

5. The preparation method of tetrapeptide gastrin assisted by hexakis(X-phenoxy) cyclotriphosphazene compounds according to claim 2, characterized in that, The general structural formula of compound [PG-Met-Asp(OtBu)-Phe-]6HXPCP is: In the formula, X represents O; PG represents Fmoc, Boc or H.

6. The preparation method of tetrapeptide gastrin assisted by hexakis(X-phenoxy) cyclotriphosphazene compounds according to claim 2, characterized in that, The general structural formula of compound [PG-Trp-Met-Asp(OtBu)-Phe-]6HXPCP is: In the formula, X represents O; PG represents Fmoc, Boc, Cbz or H.

7. The preparation method of tetrapeptide gastrin assisted by hexakis(X-phenoxy) cyclotriphosphazene compounds according to claim 2, characterized in that, The obtained trifluoroacetate salt of tetrapeptide gastrin includes: Using a 25% ammonia solution in tetrahydrofuran as a shearing agent, the auxiliary group of the compound [PG-Trp-Met-Asp(OtBu)-Phe-]6HXPCP was first removed and separated, and then a cocktail solution of trifluoroacetic acid was used as a side chain deprotecting agent to remove the protecting groups on the side chain. After separation and purification, the trifluoroacetate salt of tetrapeptide gastrin was obtained.

8. The preparation method of tetrapeptide gastrin assisted by hexakis(X-phenoxy) cyclotriphosphazene compounds according to claim 2, characterized in that, The process of separating and purifying the trifluoroacetate salt of tetrapeptide gastrin includes: recovering the trifluoroacetate salt of tetrapeptide gastrin by rotary evaporation, neutralizing the residual solution with sodium bicarbonate, adjusting the pH to 8-9, extracting with ethyl acetate, precipitating, filtering, washing with ethyl acetate, and drying to obtain purified tetrapeptide gastrin; Among them, the ethyl acetate extraction solution obtained was rotary evaporated and concentrated to 1 / 3-1 / 4 of the original volume, and an alkane or ether solvent was added. By virtue of the property that the auxiliary group is easily crystallized and precipitated in different solvent systems, the auxiliary group can be separated from other impurities; the separated auxiliary group was filtered, washed or recrystallized to obtain a purified auxiliary group, which can be reused directly or after regeneration as an auxiliary group after recovery.

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