Preparation method of intermediate of aurestatin derivative

Abstract

Compared with the prior art, the process route for preparing the intermediate of the aurestatin derivative has the advantages that the use of norephedrine in a synthesis route is effectively avoided, in addition, the target product can be produced in one step by the process route of the intermediate of the aurestatin derivative, and the process route is suitable for industrial production. The method can effectively avoid generation of reaction intermediate products, the purification method is simple, the yield and purity of the final product are high, and the method is suitable for industrial expanded production.

Description

A method for preparing an auristatin derivative intermediate Technical Field The present invention relates to the technical field of pharmaceutical intermediate synthesis, and in particular to a method for preparing an auristatin derivative intermediate. Background Art Antibody drug conjugate (ADC) is a type of anti-tumor drug, which includes three components: antibody, linker and toxin. The antibody and toxin are connected by the linker. Its mechanism of action is to use the targeting of the antibody to transport the drug to the target cells (such as tumor cells) and then release the toxin to kill the tumor cells. Although a large number of natural and chemically synthesized cytotoxins are known to exist, only a very small number of drug structures can be applied to ADC. This is mainly because the toxins that can be used as ADC loads must have complex characteristics such as extremely high cytotoxicity, intracellular targets and small molecular structures. Among them, auristatins (such as MMAE, MMAF, etc.) are cytotoxic molecules that have been successfully developed and applied in multiple ADC drugs. MMAE (Monomethyl Auristantin E, also known as methyl auristatin E) is a chemically synthesized derivative of auristatins, which can effectively inhibit mitosis by inhibiting tubulin polymerization. The current market price of MMAE is very expensive. One reason is that the currently known synthesis route of MMAE contains multiple steps. The synthesis route is relatively complicated and often needs to be carried out under extreme conditions, such as ultra-low temperature, and the yield is not high. Some of the substrates also involve the use of controlled compounds such as norephedrine. At present, the more common preparation route of MMAE is as follows, wherein compound (I-1) is a common starting material (an auristatin derivative intermediate): Regarding the preparation of the starting material compound (I-1), Chinese patent publication number CN107921144A discloses a preparation idea, wherein compound A is first used to prepare compound B (see Example 6 on page 49 of the specification), and then reacted with different intermediates to generate auristatin derivatives with different substitution groups (see Example 11 on page 51 of the specification, Example 17 on page 53 of the specification, and Example 25 on page 55 of the specification, etc.). The specification of the Chinese patent with publication number CN104185477A, ​​page 130,

[1061] The present invention discloses a process for preparing compound (I-1) based on compound B, and the route is: The preparation process of the above-mentioned compound (I-1) is a two-step reaction (i.e., through compound A→compound B→compound (I-1)), which not only has technical defects such as reduced final product yield and increased production cost, but its biggest defect is that the norephedrine used as a synthetic raw material is a precursor chemical that can be made into methamphetamine, commonly known as "ice", through a not complicated chemical transformation. It is a controlled variety and its purchase source is subject to certain restrictions, which increases the complexity and risk of the production process. Summary of the invention In view of the problems faced by the prior art, the present invention provides a new process route for preparing the above-mentioned auristatin derivative intermediates. Specifically, the auristatin derivative intermediates involved in the present invention are compounds represented by formula (I), enantiomers, racemates or pharmaceutically acceptable salts thereof: Its preparation route is: in: R1, R2, R3 are independently selected from H, C1-C8 alkyl, C1-C8 heteroalkyl, C2-C8 alkenyl, C2-C8 alkynyl, C3-C8 heterocycle, C3-C8 carbocycle, aryl, C1-C8 alkaryl, C1-C8 alkylcarbocycle or C1-C8 alkylheterocycle; R4 is an amino protecting group; R5 is O or S; R6 is H, OH, C1-C8 alkyl, C3-C8 carbocycle or O-(C1-C8 alkyl). The preparation method of the auristatin derivative intermediate provided by the present invention generally comprises the following steps: Step 1: dissolving compound a in an appropriate amount of organic solvent 1; Step 2: adding an aqueous solution of an inorganic base to the solution formed in step 1 to react; Step 3: post-treating the reaction system formed in step 2 to obtain a compound of formula (I); Wherein, the organic solvent 1 is selected from any one or more of N,N-dimethylformamide, N-methylpyrrolidone, methanol, ethanol, isopropanol, acetonitrile, acetone, tetrahydrofuran, and 1,4-dioxane solvents. In some preferred embodiments, the organic solvent 1 is methanol; in other preferred embodiments, the organic solvent 1 is anhydrous ethanol; in other preferred embodiments, the organic solvent 1 is tetrahydrofuran; in other preferred embodiments, the organic solvent 1 is acetonitrile. In other preferred embodiments, the organic solvent 1 is a mixed solution of any two of N,N-dimethylformamide, N-methylpyrrolidone, methanol, ethanol, isopropanol, acetonitrile, acetone, tetrahydrofuran, and 1,4-dioxane solvents, such as a solution of methanol and ethanol mixed in any volume ratio, a solution of N,N-dimethylformamide and N-methylpyrrolidone mixed in any volume ratio, a solution of N-methylpyrrolidone and methanol mixed in any volume ratio, a solution of ethanol and isopropanol mixed in any volume ratio, A solution of isopropanol and acetonitrile mixed in any volume ratio, a solution of acetonitrile and acetone mixed in any volume ratio, a solution of acetone and tetrahydrofuran mixed in any volume ratio, a solution of tetrahydrofuran and 1,4-dioxane solvent mixed in any volume ratio, or a solution of any volume ratio of other combinations, and when the organic solvent 1 is a mixed solution of two reagents, the two can be in any volume ratio, such as 1:1, 1:2, 1:3, 1:4... or 2:1, 3:1, 4:1... or other volume ratios. Preferably, R1 is selected from H, C1-C8 alkyl, C1-C8 heteroalkyl, C2-C8 alkenyl, C2-C8 alkynyl, C3-C8 heterocycle, C3-C8 carbocycle, aryl, C1-C8 alkylaryl, C1-C8 alkyl carbocycle or C1-C8 alkyl heterocycle; preferably, R1 is C1-C8 alkyl; more preferably, R1 is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl; more preferably, R1 is methyl or ethyl. Preferably, R2 is selected from H, C1-C8 alkyl, C1-C8 heteroalkyl, C2-C8 alkenyl, C2-C8 alkynyl, C3-C8 heterocycle, C3-C8 carbocycle, aryl, C1-C8 alkylaryl, C1-C8 alkyl carbocycle or C1-C8 alkyl heterocycle; preferably, R2 is aryl. Preferably, R3 is selected from H, C1-C8 alkyl, C1-C8 heteroalkyl, C2-C8 alkenyl, C2-C8 alkynyl, C3-C8 heterocycle, C3-C8 carbocycle, aryl, C1-C8 alkylaryl, C1-C8 alkyl carbocycle or C1-C8 alkyl heterocycle; preferably, R3 is C1-C8 alkyl; more preferably, R3 is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl; more preferably, R3 is methyl or ethyl. The R4 is a Boc protecting group, a Cbz protecting group, an Fmoc protecting group, or a benzyl group. In some specific embodiments, R4 is a Boc protecting group; in some specific embodiments, R4 is a Cbz protecting group; in some specific embodiments, R4 is an Fmoc protecting group; in other specific embodiments, R4 is a benzyl group. Preferably, the R5 is O; or preferably, the R5 is S. Preferably, the R6 is selected from H, OH, C1-C8 alkyl, C3-C8 carbocycle or O-(C1-C8 alkyl); more preferably, the R6 is O-(C1-C8 alkyl); even more preferably, the R6 is methoxy. Preferably, the structure of the compound a is selected from the following: Preferably, the structure of the compound of formula (I) is: The inorganic base involved in step 2 is lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, potassium carbonate, cesium carbonate, sodium carbonate. In some preferred embodiments, the inorganic base involved in step 2 is lithium hydroxide; in other preferred embodiments, the inorganic base involved in step 2 is sodium hydroxide; in other preferred embodiments, the inorganic base involved in step 2 is potassium hydroxide; in other preferred embodiments, the inorganic base involved in step 2 is calcium hydroxide; in other preferred embodiments, the inorganic base involved in step 2 is potassium carbonate; in other preferred embodiments, the inorganic base involved in step 2 is cesium carbonate; in other preferred embodiments, the inorganic base involved in step 2 is sodium carbonate. In some specific embodiments, the mass fraction of the inorganic alkali aqueous solution is 2%-15%; preferably, the mass fraction of the inorganic alkali aqueous solution is 3%-10%. In some preferred embodiments, the mass fraction of the inorganic alkali aqueous solution is 2%; preferably, the mass fraction of the inorganic alkali aqueous solution is 3%-10%. In some preferred embodiments, the mass fraction of the inorganic alkali aqueous solution is 3%; in some preferred embodiments, the mass fraction of the inorganic alkali aqueous solution is 4%; in some preferred embodiments, the mass fraction of the inorganic alkali aqueous solution is 5%; in other preferred embodiments, the mass fraction of the inorganic alkali aqueous solution is 6%; in other preferred embodiments, the mass fraction of the inorganic alkali aqueous solution is 7%; in other preferred embodiments, the mass fraction of the inorganic alkali aqueous solution is 8%; in other preferred embodiments, the mass fraction of the inorganic alkali aqueous solution is 9%; in other preferred embodiments, the mass fraction of the inorganic alkali aqueous solution is 10%; in other preferred embodiments, the mass fraction of the inorganic alkali aqueous solution is 11%; in other preferred embodiments, the mass fraction of the inorganic alkali aqueous solution is 12%; in other preferred embodiments, the mass fraction of the inorganic alkali aqueous solution is 13%; in other preferred embodiments, the mass fraction of the inorganic alkali aqueous solution is 14%; in other preferred embodiments, the mass fraction of the inorganic alkali aqueous solution is 15%. In other preferred embodiments, the inorganic alkali aqueous solution may also have other mass fractions, such as 4.8%, 5.5%, 5.7%, 7.4%, 9.4%, 8.9%, 9.1%...etc. In other specific embodiments, the weight volume ratio (g / mL) of compound a and organic solvent 1 is W 化合物a :V 有机溶 剂1 Preferably, the weight-to-volume ratio of the compound a to the organic solvent 1 is 1:3-14. In some preferred embodiments, the weight-to-volume ratio (g / mL) of the compound a to the organic solvent 1 is W 化合物a :V 有机溶剂1 In other preferred embodiments, the weight volume ratio (g / mL) of compound a and organic solvent 1 is W 化合物a :V 有机溶剂1 It is 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, 1:26, 1:27, 1:28, 1:29, or 1:30 or other non-integer ratios, such as approximately 1:3.1, ..., 1:3.2, ..., 1:5.27, ..., 1:6.23, ..., 1:6.72, ..., 1:10.32, ..., 1:11.21, ..., 1:13.45, ..., etc. In other specific embodiments, the molar ratio of compound a to the inorganic base is 1:1-10. Preferably, the molar ratio of compound a to the inorganic base is 1:1-5. In some preferred embodiments, the molar ratio of compound a to the inorganic base is 1:1; in some preferred embodiments, the molar ratio of compound a to the inorganic base is 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10. It can also be understood that in other preferred embodiments, the molar ratio of compound a to the inorganic base can also be a non-integer ratio, such as 1:1.1, ..., 1:1.5, ..., 1:2.6, ..., 1:4.8..., etc. In other specific embodiments, the reaction temperature of the reaction in step 2 is -10 to 78°C; preferably, the reaction temperature of the reaction in step 2 is 5 to 40°C; more preferably, the reaction temperature of the reaction in step 2 is 15 to 35°C (such as 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C), in some preferred embodiments, the reaction temperature of the reaction in step 2 can also be a range of values, such as 20±5°C, ..., 30±5°C, ..., etc. Furthermore, the step three requires adjusting the reaction system formed in the step two to be acidic before post-treatment. Further preferably, in the step 3, the reaction system formed in the step 2 is adjusted to pH = 1 to 6 before post-treatment, such as pH = 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3 , 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, of course, it can also be other values, such as 1.15, 2.26, 3.48... and so on. Furthermore, the post-treatment described in step three mainly includes an extraction process and a crystallization process. Furthermore, the extraction solvent used in the extraction process is selected from one or more of ethyl acetate, dichloromethane, methyl tert-butyl ether, isopropyl acetate, and 2-methyltetrahydrofuran solvents. It is understood that the volume of the extraction solvent should not be regarded as a limitation of the present invention. In some preferred embodiments, the weight-to-volume ratio (g / mL) of the compound a and the extraction solvent is W 化合物a :V 萃取溶剂 1:10-30 (e.g., 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, 1:26, 1:27, 1:28, 1:29, 1:30, or other ratios, such as non-limiting about 1:14.55, 1:14.57, 1:19.49, 1:20.17, 1:24.66, ..., etc.) Furthermore, the crystallization solvent selected in the crystallization process is one or more of N,N-dimethylformamide, N-methylpyrrolidone, methanol, ethanol, isopropanol, acetonitrile, acetone, 1,4-dioxane, ethyl acetate, dichloromethane, isopropyl acetate, tetrahydrofuran, 2-methyltetrahydrofuran, methyl tert-butyl ether, n-hexane, n-heptane, cyclohexane, and methylcyclopentane. In some preferred embodiments, the crystallization solvent is one of N,N-dimethylformamide, N-methylpyrrolidone, methanol, ethanol, isopropanol, acetonitrile, acetone, 1,4-dioxane, ethyl acetate, dichloromethane, isopropyl acetate, tetrahydrofuran, 2-methyltetrahydrofuran, methyl tert-butyl ether, n-hexane, n-heptane, cyclohexane, and methylcyclopentane. In other preferred embodiments, the crystallization solvent is two of N,N-dimethylformamide, N-methylpyrrolidone, methanol, ethanol, isopropanol, acetonitrile, acetone, 1,4-dioxane, ethyl acetate, dichloromethane, isopropyl acetate, tetrahydrofuran, 2-methyltetrahydrofuran, methyl tert-butyl ether, n-hexane, n-heptane, cyclohexane, and methylcyclopentane (i.e., crystallization solvent 1 and crystallization solvent 2), such as: ethyl acetate-n-hexane, methyl tert-butyl ether-n-heptane, ethyl acetate-n-heptane, etc. Wherein, the crystallization solvent 1 and the crystallization solvent 2 are in any volume ratio, preferably 1:1, 1:2, 2:1, 1:3, 3:1, 1:4, 4:1, 1:5, 5:1, etc. It is understood that the volume of the crystallization solvent should not be regarded as a limitation of the present invention; in some preferred embodiments, the weight-to-volume ratio (g / mL) of the compound a to the total volume of the crystallization solvent is W 化合物a :V 析晶溶剂 1:3-10 (such as 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, or other ratios, such as non-limiting approximately 1:3.11, 1:3.36, 1:5.27, 1:5.6, 1:8.97, 1:9.17, ..., etc.). Further, the target temperature of the crystallization process (i.e., the lowest temperature dropped during the crystallization process) is -25 to 60°C; preferably, the target temperature of the crystallization process is -10 to 40°C; more preferably, the target temperature of the crystallization process is 0 to 10°C, which can be a specific temperature or a range of values ​​(such as 0°C, 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C, 10°C, 2±2°C, 3±2°C, 4±2°C, 5±2°C, 6±2°C, 7±2°C, 8±2°C, etc.). It is understandable that the above crystallization process can be to first add the crystallization solvent and then lower the temperature of the entire system to the target temperature; or to first lower the temperature of the entire system to the target temperature and then add the crystallization solvent. In addition, the post-treatment described in step 3 may include other processes besides the extraction process and the crystallization process, such as drying of the extract, filtering and rotary evaporation of the extract, filtering of the crystallization system and other conventional operations. Compared with the prior art, the process route of the auristatin derivative intermediate provided by the present invention effectively avoids the use of the controlled compound-norephedrine, and the reaction conditions are mild. In addition, the process route of the auristatin derivative intermediate provided by the present invention can produce the target product in one step, can effectively avoid the generation of reaction intermediates, has a simple purification method, and has a high yield and purity of the final product, which is suitable for industrialized expansion production. DETAILED DESCRIPTION

definition

Claims

1. A method for preparing an auristatin derivative intermediate, characterized in that: The auristatin derivative intermediate is a compound represented by formula (I) or its enantiomer, racemate or pharmaceutically acceptable salt: Its preparation route is: in: R1, R2, R3 are independently selected from H, C1-C8 alkyl, C1-C8 heteroalkyl, C2-C8 alkenyl, C2-C8 alkynyl, C3-C8 heterocycle, C3-C8 carbocycle, aryl, C1-C8 alkaryl, C1-C8 alkylcarbocycle or C1-C8 alkylheterocycle; R4 is an amino protecting group; R5 is O or S; R6 is H, -OH, C1-C8 alkyl, C3-C8 carbocycle or -O-(C1-C8 alkyl); The preparation method thereof comprises the following steps: Step 1: dissolving compound a in an appropriate amount of organic solvent 1; Step 2: adding an aqueous solution of an inorganic base to the solution formed in step 1 to react; Step 3: post-treating the reaction system formed in step 2 to obtain a compound of formula (I); Wherein, the organic solvent 1 is selected from any one or more of N,N-dimethylformamide, N-methylpyrrolidone, methanol, ethanol, isopropanol, acetonitrile, acetone, tetrahydrofuran, and 1,4-dioxane solvents.

2. The preparation method according to claim 1, characterized in that: The R4 is a Boc protecting group, a Cbz protecting group, a Fmoc protecting group or a benzyl group.

3. The preparation method according to claim 1, characterized in that: The structure of the compound a is selected from the following:

4. The preparation method according to claim 1, characterized in that: The structure of the compound of formula (I) is:

5. The preparation method according to claim 1, characterized in that: The organic solvent 1 is selected from methanol and ethanol.

6. The preparation method according to claim 1, characterized in that: The inorganic base involved in the step 2 is lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, potassium carbonate, cesium carbonate, or sodium carbonate.

7. The preparation method according to claim 1, characterized in that: The mass fraction of the inorganic alkali aqueous solution is 2%-15%; preferably, the mass fraction of the inorganic alkali aqueous solution is 3%-10%; preferably, the weight volume ratio (g / mL) of the compound a and the organic solvent 1 is W 化合物a :V 有机溶剂1 is 1:3-30; further preferably, the weight volume ratio (g / mL) of the compound a and the organic solvent 1 is W 化合物a :V 有机溶剂1 It is 1:3–14.

8. The preparation method according to claim 1, characterized in that: The molar ratio of the compound a to the inorganic base is 1:1-10; preferably, the molar ratio of the compound a to the inorganic base is 1:1-5.

9. The preparation method according to claim 1 is characterized in that: The reaction temperature of the reaction in step 2 is -10 to 78°C; preferably, the reaction temperature of the reaction is 5 to 40°C; preferably, the reaction temperature of the reaction is 15 to 35°C.

10. The preparation method according to claim 1, characterized in that: The step three requires adjusting the reaction system formed in step two to be acidic before post-treatment.

11. The preparation method according to claim 1, characterized in that: The post-treatment described in step three mainly includes an extraction process and a crystallization process; preferably, the extraction solvent selected in the extraction process is selected from one or more of ethyl acetate, dichloromethane, methyl tert-butyl ether, isopropyl acetate, and 2-methyltetrahydrofuran solvents; preferably, the crystallization solvent selected in the crystallization process is one or more of N,N-dimethylformamide, N-methylpyrrolidone, methanol, ethanol, isopropanol, acetonitrile, acetone, 1,4-dioxane, ethyl acetate, dichloromethane, isopropyl acetate, tetrahydrofuran, 2-methyltetrahydrofuran, methyl tert-butyl ether, n-hexane, n-heptane, cyclohexane, and methylcyclopentane.

12. The preparation method according to claim 11, characterized in that: The target temperature of the crystallization process is -25 to 60°C; preferably, the target temperature of the crystallization process is -10 to 40°C; more preferably, the target temperature of the crystallization process is 0 to 10°C.