Method for synthesizing linker-MMAF

Abstract

The invention relates to a method for synthesizing a linker-MMAF, which comprises the following steps: S2, carrying out condensation reaction on a compound III and a compound IV to obtain a compound V; wherein in the step S2, the condensation reaction is carried out in the presence of a condensing agent 1-propyl phosphoric acid cyclic anhydride. The synthesis method disclosed by the invention does not need reversed-phase preparation, is simple to operate, and effectively reduces the refining cost; and during refining, a high-purity product is obtained, and meanwhile, the product yield is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of organic chemical synthesis, and particularly relates to a method for synthesizing a linker-MMAF. Background Art

[0002] Antibody-Drug Conjugate (ADC), as a type of targeted anticancer drug, can perfectly combine monoclonal antibodies and highly effective cytotoxins, making full use of the advantages of monoclonal antibodies in targeting and strong selectivity, and making good use of the advantages of cytotoxins in highly killing tumor cells. At the same time, after the cytotoxins are coupled with antibodies, the drugs formed have little toxicity to healthy cells, which effectively solves the disadvantage that single cytotoxins are highly toxic to the body.

[0003] When selecting cytotoxins, MMAF, as an anti-mitotic auristatin derivative, has high potential. The existing linker-MMAF synthesis method usually uses a methyl group to protect the carboxylic acid end of MMAF, and then remove the methyl ester after the linker and MMAF are condensed. However, in the process of hydrolyzing the methyl ester, it is easy for some linkers to fall off or break, making it difficult to purify the crude product. HPLC preparation is required, which is costly. In addition, when the linker and MMAF are condensed, the reaction of ordinary condensing agents is general and there are many impurities. Summary of the invention

[0004] Problem that the invention aims to solve

[0005] In order to solve the above problems existing in the prior art, the present invention provides a method for synthesizing linker-MMAF, which has a more thorough reaction, less impurities, and improves the product yield while obtaining a high-purity product.

[0006] Solutions for solving problems

[0007] The first object of the present invention is to provide a method for preparing compound V, comprising the following steps:

[0008]

[0009] S2. Compound III and compound IV undergo condensation reaction to obtain compound V;

[0010] Wherein, in the step S2, the condensation reaction is carried out in the presence of a condensation agent, 1-propylphosphoric acid cyclic anhydride.

[0011] Preferably, the step S2 is carried out in an organic solvent A.

[0012] Preferably, the organic solvent A is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, N,N-dimethylformamide, preferably dichloromethane.

[0013] Preferably, in step S2, the condensation reaction is carried out in the presence of an organic base.

[0014] Preferably, the organic base is one or more of piperidine, triethylamine, N,N-diisopropylethylamine, and pyridine, preferably N,N-diisopropylethylamine.

[0015] The second object of the present invention is to provide a method for synthesizing linker-MMAF, characterized in that it comprises the following steps:

[0016]

[0017] S2. Compound III and compound IV undergo condensation reaction to obtain compound V;

[0018] S3. Compound V is deprotected to obtain compound VI;

[0019] S4. Compound VI and RM undergo condensation reaction to obtain compound VII;

[0020] S5. Compound VII is deprotected to obtain compound I;

[0021] Wherein, in the step S2, the condensation reaction is carried out in the presence of a condensation agent, 1-propylphosphoric acid cyclic anhydride;

[0022] R- is a linker;

[0023] M is selected from -OH and One of them.

[0024] Preferably, the R is selected from one of the structures L1, L2 and L3 shown below:

[0025]

[0026] Preferably, the step S2 is carried out in an organic solvent A.

[0027] Preferably, the organic solvent A is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, N,N-dimethylformamide, preferably dichloromethane.

[0028] Preferably, in step S2, the condensation reaction is carried out in the presence of an organic base.

[0029] Preferably, the organic base is one or more of piperidine, triethylamine, N,N-diisopropylethylamine, and pyridine, preferably N,N-diisopropylethylamine.

[0030] Preferably, the step S3 is carried out in an organic solvent B.

[0031] Preferably, the organic solvent B is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, N,N-dimethylformamide, preferably dichloromethane.

[0032] Preferably, step S3 is performed in the presence of a base.

[0033] Preferably, the base is one or more of piperidine and diethylamine, preferably diethylamine.

[0034] Preferably, the step S4 is carried out in an organic solvent C.

[0035] Preferably, the organic solvent C is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, N,N-dimethylformamide, preferably N,N-dimethylformamide.

[0036] Preferably, in step S4, the condensation reaction is carried out in the presence of a condensation agent 1-hydroxybenzotriazole.

[0037] Preferably, in step S4, the condensation reaction is carried out in the presence of an organic base.

[0038] Preferably, the organic base is one or more of triethylamine, N,N-diisopropylethylamine and pyridine, preferably pyridine.

[0039] Preferably, the step S5 is carried out in an organic solvent D.

[0040] Preferably, the organic solvent D is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, N,N-dimethylformamide, preferably dichloromethane.

[0041] Preferably, step S5 is performed in the presence of an acid.

[0042] Preferably, the acid is one or more of hydrochloric acid, sulfuric acid, phosphoric acid, and trifluoroacetic acid, preferably trifluoroacetic acid.

[0043] Preferably, the method further comprises the steps of:

[0044]

[0045] S1. Compound II is deprotected to obtain compound III.

[0046] Preferably, the step S1 is carried out in an organic solvent E.

[0047] Preferably, the organic solvent E is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, N,N-dimethylformamide, preferably dichloromethane.

[0048] Preferably, step S1 is performed in the presence of a base.

[0049] Preferably, the base is one or more of piperidine and diethylamine, preferably diethylamine.

[0050] Preferably, the method further comprises the steps of:

[0051] S6. Compound I from step S5 is slurried with organic solvent F and purified by silica gel column.

[0052] Preferably, in step S6, the organic solvent F is diethyl ether.

[0053] Preferably, in step S6, the eluent of the silica gel column is a mixed solvent of dichloromethane and methanol.

[0054] Preferably, the volume ratio of the mixed solvent is dichloromethane:methanol=(10-30):1, preferably dichloromethane:methanol=(15-25):1, and more preferably dichloromethane:methanol=20:1.

[0055] Effects of the Invention

[0056] In the synthesis step of the present invention, the condensation reaction selects the condensation agent 1-propyl phosphoric acid cyclic anhydride (T3P), so that the reaction is more thorough and the impurities are less; and compared with other condensation agents, 1-propyl phosphoric acid cyclic anhydride (T3P) has low toxicity and low allergy, is environmentally friendly, and has good economic efficiency. The synthesis method of the present invention does not require reverse phase preparation, is simple to operate, and effectively reduces the refining cost; and during refining, while obtaining a high-purity product, the product yield is improved. DETAILED DESCRIPTION

[0057] In order to make the technical solutions and beneficial effects of the present invention more clearly understood, the following is a detailed description by listing specific embodiments. Unless otherwise defined, the technical and scientific terms used herein have the same meanings as those in the technical field to which this application belongs.

[0058] The first object of the present invention is to provide a method for preparing compound V, comprising the following steps:

[0059]

[0060] S2. Compound III and compound IV undergo condensation reaction to obtain compound V;

[0061] Wherein, in the step S2, the condensation reaction is carried out in the presence of a condensation agent, 1-propylphosphoric acid cyclic anhydride.

[0062] In certain embodiments, the step S2 is carried out in an organic solvent A.

[0063] In certain embodiments, the organic solvent A is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, and N,N-dimethylformamide.

[0064] In certain embodiments, the organic solvent A is dichloromethane.

[0065] In certain embodiments, in step S2, the condensation reaction is carried out in the presence of an organic base.

[0066] In certain embodiments, the organic base is one or more of piperidine, triethylamine, N,N-diisopropylethylamine, and pyridine.

[0067] In certain embodiments, the organic base is N,N-diisopropylethylamine.

[0068] The second object of the present invention is to provide a method for synthesizing linker-MMAF, comprising the following steps:

[0069]

[0070]

[0071] S2. Compound III and compound IV undergo condensation reaction to obtain compound V;

[0072] S3. Compound V is deprotected to obtain compound VI;

[0073] S4. Compound VI and RM undergo condensation reaction to obtain compound VII;

[0074] S5. Compound VII is deprotected to obtain compound I;

[0075] Wherein, in the step S2, the condensation reaction is carried out in the presence of a condensation agent, 1-propylphosphoric acid cyclic anhydride; R- is a linker;

[0076] M is selected from -OH and One of them.

[0077] In certain embodiments, the R is selected from one of the structures L1, L2 and L3 shown below:

[0078]

[0079]

[0080] In certain embodiments, the step S2 is carried out in an organic solvent A.

[0081] In certain embodiments, the organic solvent A is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, and N,N-dimethylformamide.

[0082] In certain embodiments, the organic solvent A is dichloromethane.

[0083] In certain embodiments, in step S2, the condensation reaction is carried out in the presence of an organic base.

[0084] In certain embodiments, the organic base is one or more of piperidine, triethylamine, N,N-diisopropylethylamine, and pyridine.

[0085] In certain embodiments, the organic base is N,N-diisopropylethylamine.

[0086] In certain embodiments, the step S3 is carried out in an organic solvent B.

[0087] In certain embodiments, the organic solvent B is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, and N,N-dimethylformamide.

[0088] In certain embodiments, the organic solvent B is dichloromethane.

[0089] In certain embodiments, step S3 is performed in the presence of a base.

[0090] In certain embodiments, the base is one or more of piperidine and diethylamine.

[0091] In certain embodiments, the base is diethylamine.

[0092] In certain embodiments, the step S4 is carried out in an organic solvent C.

[0093] In certain embodiments, the organic solvent C is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, and N,N-dimethylformamide.

[0094] In certain embodiments, the organic solvent C is N,N-dimethylformamide.

[0095] In certain embodiments, in step S4, the condensation reaction is carried out in the presence of a condensation agent, 1-hydroxybenzotriazole.

[0096] In certain embodiments, in step S4, the condensation reaction is carried out in the presence of an organic base.

[0097] In certain embodiments, the organic base is one or more of triethylamine, N,N-diisopropylethylamine, and pyridine.

[0098] In certain embodiments, the organic base is pyridine.

[0099] In certain embodiments, the step S5 is carried out in an organic solvent D.

[0100] In certain embodiments, the organic solvent D is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, and N,N-dimethylformamide.

[0101] In certain embodiments, the organic solvent D is dichloromethane.

[0102] In certain embodiments, step S5 is performed in the presence of an acid.

[0103] In certain embodiments, the acid is one or more of hydrochloric acid, sulfuric acid, phosphoric acid, and trifluoroacetic acid.

[0104] In certain embodiments, the acid is trifluoroacetic acid.

[0105] In certain embodiments, the method further comprises the steps of:

[0106]

[0107] S1. Compound II is deprotected to obtain compound III.

[0108] In certain embodiments, the step S1 is carried out in an organic solvent E.

[0109] In certain embodiments, the organic solvent E is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, and N,N-dimethylformamide.

[0110] In certain embodiments, the organic solvent E is dichloromethane.

[0111] In certain embodiments, step S1 is performed in the presence of a base.

[0112] In certain embodiments, the base is one or more of piperidine and diethylamine.

[0113] In certain embodiments, the base is diethylamine.

[0114] In certain embodiments, the method further comprises the steps of:

[0115] S6. Compound I from step S5 is slurried with organic solvent F and purified by silica gel column.

[0116] In certain embodiments, in step S6, the organic solvent F is diethyl ether.

[0117] In certain embodiments, in step S6, the eluent of the silica gel column is a mixed solvent of dichloromethane and methanol.

[0118] In certain embodiments, the volume ratio of the mixed solvent is dichloromethane:methanol=(10-30):1.

[0119] In certain embodiments, the volume ratio of the mixed solvent is dichloromethane:methanol=(15-25):1.

[0120] In certain embodiments, the volume ratio of the mixed solvent is dichloromethane:methanol=20:1.

[0121] The method of the present invention is described below by means of specific examples. It should be understood that these examples are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following examples; the implementation conditions adopted in the examples can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in routine experiments.

[0122] The following abbreviations are used in this article and have the definitions shown below:

[0123] Cit is citrulline;

[0124] Dap is dolaproine;

[0125] DCM is dichloromethane;

[0126] DEA is diethylamine;

[0127] DIEA is N,N-diisopropylethylamine;

[0128] Dil is dolaisoleuine;

[0129] DMF is N,N-dimethylformamide;

[0130] Fmoc is N-(9-fluorenylmethoxycarbonyl);

[0131] HOBt is 1-hydroxybenzotriazole;

[0132] N-Me-Val is N-methyl valine;

[0133] PAB is p-aminobenzyl;

[0134] PNP is p-nitrophenol;

[0135] MC is 6-maleimidocaproyl (maleimidocaproyl);

[0136] Phe is phenylalanine;

[0137] TFA is trifluoroacetic acid;

[0138] T3P is 1-propylphosphonic acid cyclic anhydride;

[0139] Val is valine;

[0140] ODMB is (2,4-dimethoxybenzyl) ester group;

[0141] Val-Cit is a valine-citrulline dipeptide;

[0142] MMAF is N-Me-Val-Val-Dil-Dap-Phe.

[0143] In the following examples, unless otherwise specified, all temperatures are in degrees Celsius. Unless otherwise specified, various starting materials and reagents are commercially available or synthesized according to known methods. Commercially available materials and reagents are used directly without further purification. Unless otherwise specified, commercial manufacturers include but are not limited to Sinopharm Group, J&K Technology Co., Ltd., TCI (Shanghai) Chemical Industry Development Co., Ltd., Shanghai Bid Pharmaceutical Technology Co., Ltd. and Shanghai Myrel Chemical Technology Co., Ltd.

[0144] Unless otherwise specified in the examples, the solution in the reaction refers to an aqueous solution.

[0145] Unless otherwise specified in the examples, the reaction temperature is room temperature, 20°C-30°C.

[0146] Example 1: Preparation of Compound III (Dap-Phe-ODMB)

[0147] In a 1L single-mouth bottle, add compound II (Fmoc-Dap-Phe-ODMB) (47.00g, 0.0665mol, 1.0eq) and 500.00mL dichloromethane (DCM), and start magnetic stirring. Add 94mL diethylamine (DEA). React at an external temperature of 30℃ for 12 hours. After detection, compound II (Fmoc-Dap-Phe-ODMB) reacts completely and the reaction is over. Remove the solvent to obtain a crude compound III (Dap-Phe-ODMB).

[0148] Example 2: Preparation of Compound V (Fmoc-MMAF-ODMB)

[0149] In a 1L three-necked flask, add crude compound III (Dap-Phe-ODMB) (0.0665 mol, 1.0 eq) and 500.00 mL of dichloromethane (DCM), and start magnetic stirring. Add compound IV (Fmoc-N-Me-Val-Val-Dil) (42.42 g, 0.0665 mol, 1.0 eq). Cool in an ice bath, control the internal temperature between 0°C and 10°C, add 1-propylphosphoric acid cyclic anhydride (T3P) (25.39 g, 0.0798 mol, 1.2 eq), and drop N,N-diisopropylethylamine (DIEA) (12.89 g, 0.0997 mol, 1.5 eq). After the dropwise addition, stir in an ice bath for 10 minutes, move to room temperature, react for 5 hours, and detect that compound IV (Fmoc-N-Me-Val-Val-Dil) reacts completely, and the reaction is over. The reaction solution was washed with water (500.00 mL*1), 5% citric acid aqueous solution (500.00 mL*1), saturated sodium bicarbonate aqueous solution (500.00 mL*1), and saturated brine (500.00 mL*1). The organic layer was dried over anhydrous sodium sulfate, filtered, desolventized, and purified to obtain 66.10 g of compound V (Fmoc-MMAF-ODMB) (purity 95%, yield 90%).

[0150] Example 3: Preparation of Compound VI (MMAF-ODMB)

[0151] In a 1L single-mouth bottle, add compound V (Fmoc-MMAF-ODMB) (41.00g, 0.0371mol, 1.0eq) and 400.00mL dichloromethane (DCM), and start magnetic stirring. Add 82mL diethylamine (DEA). React at an external temperature of 30°C for 12 hours. After detection, compound V (Fmoc-MMAF-ODMB) reacts completely and the reaction is over. Desolventize to obtain a crude compound VI (MMAF-ODMB). Add 500.00mL petroleum ether to the crude compound VI (MMAF-ODMB), stir for 2 hours, filter, and wash the solid with 500.00mL petroleum ether. Obtain 31.50g of compound VI (MMAF-ODMB) (purity 95%, yield 96%).

[0152] Example 4: Preparation of MC-MMAF-ODMB

[0153] In a 250mL three-necked flask, add compound VI (MMAF-ODMB) (9.00g, 0.0102mol, 1.0eq) and 90.00mL N,N-dimethylformamide (DMF), and start magnetic stirring. Add 1-hydroxybenzotriazole (HOBt) (0.28g, 0.0020mol, 0.2eq) and 6-maleimidocaproic acid (2.15g, 0.0102mol, 1.0eq). Cool in an ice bath, control the internal temperature between 0℃ and 10℃, and drop pyridine (1.21g, 0.0153mol, 1.5eq). After the drop is completed, move to an oil bath, react at an external temperature of 35℃ for 12 hours, and detect that compound VI (MMAF-ODMB) reacts completely, and the reaction is over. Desolventize to obtain the crude compound MC-MMAF-ODMB. The crude compound MC-MMAF-ODMB was added to 90.00 mL of ether and stirred for 2 hours, filtered, and the solid was washed with 90.00 mL of ether to obtain 11.00 g of the crude compound MC-MMAF-ODMB.

[0154] Example 5: Preparation of MC-MMAF

[0155] In a 500mL single-mouth bottle, add 11.00g of the crude compound MC-MMAF-ODMB and 110.00mL of dichloromethane (DCM), and turn on magnetic stirring. Add 11.00mL of trifluoroacetic acid (TFA) dropwise. After the dropwise addition, react at room temperature for 10 minutes, detect that the compound MC-MMAF-ODMB reacts completely, and the reaction is over. Remove the solvent to obtain the crude compound MC-MMAF. Add 110.00mL of ether to the crude compound MC-MMAF and stir for 2 hours, filter, wash the solid with 90.00mL of ether, and then purify it on a silica gel column. The eluent of the silica gel column is a mixed solvent of dichloromethane and methanol. The volume ratio of the mixed solvent is dichloromethane: methanol = 20:1, and 7.55g of the compound MC-MMAF (purity 95%, yield 80%) is obtained.

[0156] Example 6: Preparation of MC-Val-Cit-PAB-MMAF-ODMB

[0157] In a 250mL three-necked flask, add compound VI (MMAF-ODMB) (9.00g, 0.0102mol, 1.0eq) and 90.00mL N,N-dimethylformamide (DMF), and start magnetic stirring. Add 1-hydroxybenzotriazole (HOBt) (0.28g, 0.0020mol, 0.2eq) and MC-Val-Cit-PAB-PNP (7.53g, 0.0102mol, 1.0eq). Cool in an ice bath, control the internal temperature between 0℃ and 10℃, and drop pyridine (1.21g, 0.0153mol, 1.5eq). After the drop is completed, move to an oil bath, react at an external temperature of 35℃ for 12 hours, and detect that compound VI (MMAF-ODMB) reacts completely, and the reaction is over. Desolventize to obtain the crude compound MC-Val-Cit-PAB-MMAF-ODMB. The crude compound MC-Val-Cit-PAB-MMAF-ODMB was added to 90.00 mL of ether and stirred for 2 hours, filtered, and the solid was washed with 90.00 mL of ether to obtain 15.65 g of the crude compound MC-Val-Cit-PAB-MMAF-ODMB.

[0158] Example 7: Preparation of MC-Val-Cit-PAB-MMAF

[0159] In a 500mL single-mouth bottle, add 15.65g of crude compound MC-Val-Cit-PAB-MMAF-ODMB and 150.00mL of dichloromethane (DCM), and start magnetic stirring. Add 15.00mL of trifluoroacetic acid (TFA) dropwise. After the addition, react at room temperature for 10 minutes, and check that the compound MC-Val-Cit-PAB-MMAF-ODMB reacts completely, and the reaction is over. Desolventize to obtain the crude compound MC-Val-Cit-PAB-MMAF. The crude compound MC-Val-Cit-PAB-MMAF was added to 150.00 mL of ether and stirred for 2 hours, filtered, and the solid was washed with 90.00 mL of ether, and then purified by silica gel column. The eluent of the silica gel column was a mixed solvent of dichloromethane and methanol, and the volume ratio of the mixed solvent was dichloromethane: methanol = 20:1, to obtain 11.00 g of compound MC-Val-Cit-PAB-MMAF (purity 95%, yield 81%).

[0160] Example 8: Preparation of MC-Val-Ala-PAB-MMAF-ODMB

[0161] In a 250mL three-necked flask, add compound VI (MMAF-ODMB) (9.00g, 0.0102mol, 1.0eq) and 90.00mL N,N-dimethylformamide (DMF), and start magnetic stirring. Add 1-hydroxybenzotriazole (HOBt) (0.28g, 0.0020mol, 0.2eq) and MC-Val-Ala-PAB-PNP (6.65g, 0.0102mol, 1.0eq). Cool in an ice bath, control the internal temperature between 0℃ and 10℃, and drop pyridine (1.21g, 0.0153mol, 1.5eq). After dropping, move to an oil bath, react at an external temperature of 35℃ for 12 hours, and detect that compound VI (MMAF-ODMB) reacts completely, and the reaction is over. Desolventize to obtain the crude compound MC-Val-Ala-PAB-MMAF-ODMB. The crude compound MC-Val-Ala-PAB-MMAF-ODMB was added to 90.00 mL of ether and stirred for 2 hours, filtered, and the solid was washed with 90.00 mL of ether to obtain 15.50 g of the crude compound MC-Val-Ala-PAB-MMAF-ODMB.

[0162] Example 9: Preparation of MC-Val-Ala-PAB-MMAF

[0163] In a 500mL single-mouth bottle, add 15.50g of crude compound MC-Val-Ala-PAB-MMAF-ODMB and 150.00mL of dichloromethane (DCM), and start magnetic stirring. Add 15.00mL of trifluoroacetic acid (TFA) dropwise. After the addition, react at room temperature for 10 minutes, and check that the compound MC-Val-Ala-PAB-MMAF-ODMB reacts completely, and the reaction is over. Desolventize to obtain the crude compound MC-Val-Ala-PAB-MMAF. The crude compound MC-Val-Ala-PAB-MMAF was added to 150.00 mL of ether and stirred for 2 hours, filtered, and the solid was washed with 90.00 mL of ether, and then purified by silica gel column. The eluent of the silica gel column was a mixed solvent of dichloromethane and methanol, and the volume ratio of the mixed solvent was dichloromethane: methanol = 20:1, to obtain 10.41 g of compound MC-Val-Ala-PAB-MMAF (purity 95%, yield 82%).

[0164] It should be understood that the above embodiments are exemplary and are not intended to include all possible implementations included in the claims. Various modifications and changes may be made on the basis of the above embodiments without departing from the scope of the present disclosure. Similarly, the various technical features of the above embodiments may be arbitrarily combined to form other embodiments of the present invention that may not be explicitly described. Therefore, the above embodiments only express several implementations of the present invention and do not limit the scope of protection of the patent of the present invention.

Claims

1. A method for preparing compound V, characterized in that: The following steps are involved: S2. Compound III and compound IV undergo condensation reaction to obtain compound V; Wherein, in the step S2, the condensation reaction is carried out in the presence of a condensation agent, 1-propylphosphoric acid cyclic anhydride.

2. The method according to claim 1, characterized in that The step S2 is reacted in an organic solvent A; Preferably, the organic solvent A is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, N,N-dimethylformamide, preferably dichloromethane; Preferably, in step S2, the condensation reaction is carried out in the presence of an organic base; Preferably, the organic base is one or more of piperidine, triethylamine, N,N-diisopropylethylamine, and pyridine, preferably N,N-diisopropylethylamine.

3. A method for synthesizing linker-MMAF, characterized in that: The following steps are involved: S2. Compound III and compound IV undergo condensation reaction to obtain compound V; S3. Compound V is deprotected to obtain compound VI; S4. Compound VI and RM undergo condensation reaction to obtain compound VII; S5. Compound VII is deprotected to obtain compound I; Wherein, in the step S2, the condensation reaction is carried out in the presence of a condensation agent, 1-propylphosphoric acid cyclic anhydride; R- is a linker; M is selected from -OH and One of them.

4. The method according to claim 3, characterized in that The R is selected from one of the structures L1, L2 and L3 shown below:

5. The method according to claim 3, characterized in that The step S2 is reacted in an organic solvent A; Preferably, the organic solvent A is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, N,N-dimethylformamide, preferably dichloromethane; Preferably, in step S2, the condensation reaction is carried out in the presence of an organic base; Preferably, the organic base is one or more of piperidine, triethylamine, N,N-diisopropylethylamine, and pyridine, preferably N,N-diisopropylethylamine.

6. The method according to claim 3, characterized in that The step S3 is reacting in an organic solvent B; Preferably, the organic solvent B is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, N,N-dimethylformamide, preferably dichloromethane; Preferably, step S3 is carried out in the presence of a base; Preferably, the base is one or more of piperidine and diethylamine, preferably diethylamine.

7. The method according to claim 3, characterized in that The step S4 is reacted in an organic solvent C; Preferably, the organic solvent C is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, N,N-dimethylformamide, preferably N,N-dimethylformamide; Preferably, in step S4, the condensation reaction is carried out in the presence of a condensation agent, 1-hydroxybenzotriazole; Preferably, in step S4, the condensation reaction is carried out in the presence of an organic base; Preferably, the organic base is one or more of triethylamine, N,N-diisopropylethylamine and pyridine, preferably pyridine.

8. The method according to claim 3, characterized in that The step S5 is reacted in an organic solvent D; Preferably, the organic solvent D is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, N,N-dimethylformamide, preferably dichloromethane; Preferably, step S5 is carried out in the presence of an acid; Preferably, the acid is one or more of hydrochloric acid, sulfuric acid, phosphoric acid, and trifluoroacetic acid, preferably trifluoroacetic acid.

9. The method according to claim 3, characterized in that The method further comprises the steps of: S1. Compound II is deprotected to obtain compound III; Preferably, the step S1 is carried out in an organic solvent E; Preferably, the organic solvent E is one or more of dichloromethane, tetrahydrofuran, 2-methyltetrahydrofuran, N,N-dimethylformamide, preferably dichloromethane; Preferably, step S1 is carried out in the presence of a base; Preferably, the base is one or more of piperidine and diethylamine, preferably diethylamine.

10. The method according to any one of claims 3 to 9, characterized in that: The method further comprises the steps of: S6. Compound I of step S5 is slurried with organic solvent F and purified by silica gel column; Preferably, in step S6, the organic solvent F is diethyl ether; Preferably, in step S6, the eluent of the silica gel column is a mixed solvent of dichloromethane and methanol; Preferably, the volume ratio of the mixed solvent is dichloromethane:methanol=(10-30):1, preferably dichloromethane:methanol=(15-25):1, and more preferably dichloromethane:methanol=20:1.

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