Method for preparing nitrogen-containing fused ring compounds

Abstract

The present application provides a method for preparing nitrogen-containing fused ring compounds with antitumor activity, which can efficiently obtain the target product under relatively mild reaction conditions, and compared with the original process, the yield is significantly improved and the material cost is significantly reduced, which facilitates the scale-up of the process.

Description

[Technical Field]

[0001] This application is based on and claims priority from Chinese Application No. 202310025425.7, filed on January 9, 2023. The disclosure of the Chinese application is incorporated herein by reference in its entirety.

[0002] Technical Field The present application relates to the field of pharmaceutical chemical industry, and in particular to a method for preparing nitrogen-containing fused ring compounds. [Background technology]

[0003] background art Camptothecin (CPT) is a pentacyclic quinoline-based parent compound isolated from the Celastraceae plant Camptotheca acuminata Decne. It consists of a quinoline ring AB, a pyrrole ring C, a pyridone ring D, and an α-hydroxylactone ring E, with the 20-position being S-configured. It was introduced clinically in the early 1970s due to its excellent anticancer activity. Clinical trials were subsequently discontinued due to severe side effects such as diarrhea and hemorrhagic cystitis.

[0004] [ka]

[0005] Research data reveal that camptothecin forms a three-membered ring complex with cellular DNA topoisomerase I, thereby inhibiting DNA unwinding, leading to DNA replication inhibition and cell death (Cancer Res. 1989, 49, 6365). Camptothecin and its derivatives have shown potent antitumor activity in animal models of cancer, including lung, breast, colorectal, and ovarian cancer (Nature Review Cancer. 2006, 6, 789).

[0006] Currently, several camptothecin preparations are approved for oncology treatment. For example, topotecan is used to treat ovarian cancer, and belotecan is used to treat ovarian cancer and small cell lung cancer. Dxd, developed by Daiichi Sankyo, was approved by the FDA on August 11, 2022, becoming the world's first HER2-targeted antibody-drug conjugate, trastuzumab-deruxtecan (T-DXd, DS-8201). Currently, this drug has shown remarkable results in common solid cancers, including non-small cell lung cancer, breast cancer, gastric cancer, and colorectal cancer.

[0007] The synthesis process of camptothecin analogs has important implications for the commercialization of antitumor drugs, for example, impurity control and mass production of camptothecin analogs significantly affect the production costs of antitumor drugs.

[0008] Daiichi Sankyo Co., Ltd. (Daiichi Sankyo) has disclosed a synthetic route for camptothecin analogs in China Patent Application Publication No. 111065621A. However, this synthetic method leaves much to be desired. For example, the two-step high-temperature reaction requires a large amount of equipment, the reaction time is long, and the yield of the desired product is low (the total yield of the two steps is 43%). It is difficult to recycle isomers, and it is difficult to control the isomers after the process is scaled up, resulting in low synthetic efficiency. These ultimately lead to high costs for scaled-up production. Summary of the Invention

[0009] Contents of the present invention In order to solve the above technical problems, the present application provides a preparation method for obtaining exatecan and its analogs having a single configuration as shown in formula (I), wherein R and R in formula (I) are independently hydrogen, halogen, C 1~6 Alkyl, C 1~6 Hydroxyalkyl, C 1~6 Alkoxyalkyl, C 1~6 Alkoxy, C 1~4or R1 and R2, taken together with the carbon atom to which they are attached, form a 5- to 6-membered carbocyclic or oxygen-containing heterocyclic ring. In some embodiments, R1 and R2 are independently selected from the group consisting of halogen and C 1~6 In some embodiments, R and R are selected from F, Cl, Br, I, and C. 1~2 In some embodiments, R1 and R2 are independently selected from the group consisting of alkyl, methyl, and HCl. In some embodiments, R1 is Cl and R2 is methyl.

[0010] [ka]

[0011] One embodiment involves obtaining the parent core structure shown in formula (III) under mild conditions, then inverting the isomer to the target configuration shown in formula (IV) under acidic conditions, followed by deprotection and salting out, resulting in a three-step synthesis of the target compound shown in formula (I) in a single configuration with an overall yield of >75%. This method is highly versatile and can be applied to the synthesis of other exatecan analogs. The process is simple, allows control of the isomers, has high synthetic efficiency, is inexpensive, and is easy and practical to amplify.

[0012] Specifically, the present application provides a synthetic method suitable for the large-scale preparation of single-configuration exatecan and its analogs, the synthetic route of which is as follows:

[0013] [ka]

[0014] where R1 and R2 are hydrogen, halogen, C 1~6 Alkyl, C 1~6 Hydroxyalkyl, C 1~6 Alkoxyalkyl, C 1~6 Alkoxy, C 1~4or R1 and R2 together with the carbon atom to which they are attached form a 5- to 6-membered carbocyclic or oxygen-containing heterocyclic ring; preferably, R1 and R2 are independently selected from the group consisting of halogen and C 1~6 alkyl; preferably, R and R are selected from F, Cl, Br, I and C. 1~2 alkyl; preferably, R1 and R2 are independently selected from Cl and methyl; preferably, R1 is Cl and R2 is methyl; wherein R3 is an electron-withdrawing protecting group, such as a substituted ethoxycarbonyl (e.g., 2,2,2-trichloroethoxycarbonyl, 2-trimethylsilylethoxycarbonamide), formyl, acetyl, chloroacetyl, dichloroacetyl, trichloroacetyl, trifluoroacetyl, Fmoc, an Fmoc-like group, Troc, Cbz, Teoc, Alloc, phthaloyl (Pht), trifluoromethanesulfonyl, tert-butylsulfonyl, methylsulfonyl, benzenesulfonyl, p-toluenesulfonyl, benzylsulfonyl, 2-(trimethylsilyl)ethanesulfonyl, 4-nitrobenzenesulfonyl, (9H-9-pentyl)methylsulfonyl, 2- or 4-nitrobenzenesulfonyl, 2,4-dinitrobenzenesulfonyl, or pivaloyl.

[0015] In one aspect, the present application provides a method for preparing a compound of formula (III), the method comprising reacting a compound of formula (II) with compound 2 in the presence of a catalyst.

[0016] [ka]

[0017] where R1 and R2 are independently hydrogen, halogen, C 1~6 Alkyl, C 1~6 Hydroxyalkyl, C 1~6 Alkoxyalkyl, C 1~6 Alkoxy, C 1~4or R1 and R2 together with the carbon atom to which they are attached form a 5- to 6-membered carbocyclic or oxygen-containing heterocyclic ring; preferably, R1 and R2 are selected from the group consisting of halogen and C 1~6 alkyl; preferably, R1 and R2 are selected from F, Cl, Br, I and C 1~2 alkyl; preferably, R1 and R2 are independently selected from Cl and methyl; preferably, R1 is Cl and R2 is methyl; R3 is an electron-withdrawing protecting group; The catalyst is selected from PPTS, AcOH, TFA, H2SO4, proline, PPA, P2O5, CAN, T3P, KOH, I2, MgCl2 and TMSCl.

[0018] In some embodiments, the catalyst is PPA.

[0019] In some embodiments, the compound represented by Formula (II) and compound 2 are reacted in a solvent, wherein the solvent is selected from the group consisting of aromatic hydrocarbons (e.g., toluene, xylene, o-toluene, m-toluene), aliphatic hydrocarbons (e.g., hexane, n-heptane), alcohols (e.g., methanol, ethanol, isopropanol), organic acids (e.g., acetic acid, trifluoroacetic acid), phenols (e.g., phenol, o-cresol, m-cresol, p-cresol), ethers (e.g., ethyl ether, ethylene oxide, anisole), esters (e.g., methyl acetate, ethyl acetate, propyl acetate), ketones (e.g., acetone, butanone), amides (e.g., DMF, DMA), nitriles (e.g., acetonitrile), heterocycles (e.g., NMP, 1,4-dioxane, 2-MeTHF), sulfur-containing organic solvents (e.g., DMSO), and any combination thereof.

[0020] In some embodiments, the solvent used in the method is a combination of a phenolic solvent and a heterocyclic solvent.

[0021] In some embodiments, the organic solvent is a mixed solvent of o-cresol and 1,4-dioxane.

[0022] More specifically, in one aspect, the present application provides a method for preparing a compound represented by formula (III), the method comprising reacting a compound represented by formula (II) with compound 2 in the presence of PPA in a mixed solvent of o-cresol and 1,4-dioxane.

[0023] [ka]

[0024] where R1, R2 and R3 are defined as above.

[0025] Studies have shown that the reaction reagents have a significant effect on the reaction rate, product selectivity, product stability, and impurities. In some embodiments, acidic catalysts such as p-toluenesulfonic acid, PPTS, AcOH, TFA, H2SO4, proline, phosphoric acid, or other catalysts such as P2O5, CAN, T3P, KOH, I2, MgCl2, or TMSCl can be selected instead of PPA, but PPA is more preferred.

[0026] At the same time, research has found that the reaction solvent also has a significant effect on the reaction rate and reaction by-products. In some embodiments, the reaction solvent is PhMe, xylene, AcOH, TFA, phenol, o-toluene, m-toluene, p-cresol, EtOH, DMF, DMSO, DMA, NMP, anisole, ACN, butanone, n-heptane, ethyl acetate, 1,4-dioxane, and 2-MeTHF, as well as a mixed solvent system thereof. However, a mixed solvent system of o-cresol and 1,4-dioxane is more preferred.

[0027] In some embodiments, the volume ratio of o-cresol:1,4-dioxane is from (10:1) to (1:10), for example, from (10:1) to (1:1), from (9:1) to (1:1), from (8:1) to (1:1), from (7:1) to (1:1), from (6:1) to (1:1), from (5:1) to (1:1), from (4:1) to (1:1), from (3:1) to (1:1), or from (2:1) to (1:1), preferably 1:1.

[0028] In some embodiments, the feed molar ratio of the compound represented by Formula (II) to compound 2 is (1:1) to (1:1.5). For example, it may be (0.8:1) to (1:1.5). As a further example, it may be (1:1) to (1:1.1), (1:1) to (1:1.2), (1:1) to (1:1.3), or (1:1) to (1:1.4), and is preferably 1:1.2.

[0029] In some embodiments, the amount of PPA provided is 0.2 to 5 equivalents, for example, 0.2 equivalents, 0.3 equivalents, 0.4 equivalents, 0.5 equivalents, 0.6 equivalents, 0.7 equivalents, 0.8 equivalents, 0.9 equivalents, 1.0 equivalents, 1.1 equivalents, 1.2 equivalents, 1.3 equivalents, 1.4 equivalents, 1.5 equivalents, 1.6 equivalents, 1.7 equivalents, 1.8 equivalents, 1.9 equivalents, 2.0 equivalents, 2.5 equivalents, 3.0 equivalents, 3.5 equivalents, 4.0 equivalents, 4.5 equivalents, or 5.0 equivalents, preferably 1.0 equivalent, based on the compound of Formula (II).

[0030] In some embodiments, the compound represented by Formula (II) and Compound 2 are reacted at a temperature between 60°C and 140°C, for example, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, or 140°C, preferably between 85°C and 95°C.

[0031] In some embodiments, the compound represented by formula (II) and compound 2 are reacted for 6 to 48 hours, for example, 6 to 24 hours, 6 to 18 hours, and preferably 12 to 18 hours.

[0032] In some embodiments, the reaction is carried out without gas (eg, nitrogen) protection or with nitrogen and argon protection, preferably under a nitrogen environment.

[0033] In some embodiments, a work-up step is included after the reaction is complete to obtain a crude compound of formula (III).

[0034] In some embodiments, the work-up step includes adding water, aqueous sodium carbonate, or aqueous sodium bicarbonate for quenching, followed by filtration; or adding a mixed solvent of DCM and DCM-IPA or 2-MeTHF for extraction; or directly concentrating the reaction solution under reduced pressure to remove 1,4-dioxane, then adding one or more solvents selected from isopropanol, ethyl acetate, acetone, MTBE, PhMe, n-heptane, and ACN for dilution, followed by filtration; preferably concentrating under reduced pressure to remove 1,4-dioxane, then adding MTBE and n-heptane simultaneously or separately, followed by filtration to obtain a crude product of the compound of Formula (III).

[0035] In some embodiments, the crude product of the compound of Formula (III) does not need to be dried, and preferably residual solvent is removed under vacuum or blowing conditions at 45-55° C. before further processing.

[0036] In some embodiments, after obtaining the crude product of the compound represented by Formula (III), the method also includes a step of washing the crude product of the compound represented by Formula (III).

[0037] In some embodiments, the washing step comprises dissolving the crude product of the compound of Formula (III) in an organic solvent to obtain an organic phase, washing the organic phase with an aqueous phase 1 to 5 times, and concentrating the organic phase. In some embodiments, the organic solvent is selected from the group consisting of DCM, a mixed solvent system of DCM-IPA, DCM-EtOH, or DCM-MeOH, and 2-MeTHF, preferably 2-MeTHF.

[0038] In some embodiments, each aqueous phase is independently selected from the group consisting of water, aqueous NaCl, aqueous ammonium chloride, aqueous sodium carbonate, aqueous sodium bicarbonate, aqueous sodium hydroxide, aqueous disodium hydrogen phosphate, aqueous sodium sulfite, aqueous sodium thiosulfate, and any combination thereof.

[0039] In some embodiments, the organic phase is washed sequentially with an aqueous NaCl solution, a mixed solution of an aqueous sodium sulfite solution (e.g., a 2% aqueous sodium sulfite solution) and a saturated aqueous NaCl solution (e.g., a saturated aqueous NaCl solution) (e.g., a 1:1 volume ratio of the aqueous sodium sulfate solution to the aqueous NaCl solution), a mixed solution of an aqueous sodium carbonate solution (e.g., a 2% aqueous sodium carbonate solution) and a saturated aqueous NaCl solution (e.g., a 1:1 volume ratio of the aqueous sodium carbonate solution to the aqueous NaCl solution), and an aqueous NaCl solution.

[0040] In some embodiments, a recrystallization step is also included after washing the crude product of the compound of Formula (III).

[0041] In some embodiments, the recrystallization step comprises dissolving the compound of Formula (III) in 2-MeTHF and precipitating the crystals using MTBE. In some specific embodiments, the compound of Formula (III) is added to 2-MeTHF and heated to 40-60°C to obtain a supersaturated solution of the compound of Formula (III), followed by adding MTBE in an amount 2-5 times the amount of 2-MeTHF, lowering the temperature to 20-30°C, and recovering the compound of Formula (III) by filtration. Optionally, the method also includes steps of washing with MTBE and drying after filtration.

[0042] In the above preparation method, the types and equivalent amounts of reaction reagents and solvents are screened, and the reaction temperature, supply ratio, post-treatment and purification steps are optimized, thereby achieving a lower reaction temperature, a shorter reaction time, improved reaction stability and yield, simplification of post-reaction treatment and purification steps, and improved process stability and scalability.

[0043] In one aspect, the present application provides a method for preparing a compound of formula (IV), the method comprising the steps of converting a compound of formula (III) to a compound of formula (IV):

[0044] [ka]

[0045] where R1, R2 and R3 are as defined above.

[0046] In some embodiments, the conversion is carried out in an organic solvent selected from alcohols (e.g., methanol, ethanol, isopropanol, n-butanol), ketones (e.g., acetone, butanone, methyl isobutyl ketone), esters (e.g., ethyl acetate, isopropyl acetate), ethers (e.g., MTBE, isopropyl ether, anisole), aliphatic hydrocarbons (e.g., n-heptane), heterocycles (e.g., THF, 1,4-dioxane, 2-MeTHF, NMP), amides (e.g., DMF, DMA), sulfur-containing organic solvents (e.g., DMSO), halogen-containing organic solvents (e.g., DMSO), halogenated aliphatic hydrocarbons (e.g., DCM), ammonium hydroxide (e.g., CA), aromatic hydrocarbons (e.g., toluene), and any combination thereof.

[0047] In some embodiments, the conversion is carried out in an organic solvent selected from the group consisting of methanol, ethanol, isopropanol, n-butanol, acetone, butanone, methyl isobutyl ketone, ethyl acetate, isopropyl acetate, MTBE, n-heptane, THF, 1,4-dioxane, 2-MeTHF, isopropyl ether, DMF, DMA, DMSO, NMP, anisole, DCM, CAN, toluene, and any combination thereof.

[0048] In some embodiments, the conversion is carried out in the presence of an acid. In some embodiments, the acid is HCl.

[0049] In some embodiments, the conversion is carried out in HCl / 1,4-dioxane.

[0050] In some embodiments, the amount of acid provided is 2 to 20 equivalents based on the compound represented by Formula (III).

[0051] In some embodiments, the present application provides a method for preparing a compound of Formula (IV), comprising converting a compound of Formula (III) to a compound of Formula (IV) in the presence of HCl.

[0052] [ka]

[0053] where R1, R2 and R3 are as defined above.

[0054] Studies have found that different acids have a significant effect on the stability of the raw materials and products, as well as the isomer ratio of the products. In some embodiments, acid reagents such as concentrated hydrochloric acid, dilute hydrochloric acid, HCl in organic solvent solution, hydrobromic acid, acetic acid, methanesulfonic acid, p-toluenesulfonic acid, benzoic acid, boron trifluoride in ethyl ether solution, TFA, H2SO4 and H3PO4, preferably HCl / 1,4-dioxane solution, can be added for the conversion.

[0055] In some embodiments, the amount of HCl / 1,4-dioxane fed is 2 to 20 equivalents, preferably 4 to 8 equivalents.

[0056] In some embodiments, the reaction solvent is methanol, ethanol, isopropanol, n-butanol, acetone, butanone, methyl isobutyl ketone, ethyl acetate, isopropyl acetate, MTBE, n-heptane, THF, 1,4-dioxane, 2-MeTHF, isopropyl ether, DMF, DMA, DMSO, NMP, anisole, DCM, ACN, and toluene, preferably 1,4-dioxane.

[0057] In some embodiments, the conversion is carried out at a temperature of 25 to 100°C, preferably 40 to 50°C, for example 45°C.

[0058] In some embodiments, the conversion is carried out for 1 to 24 hours, for example, 4 to 24 hours, 1 to 20 hours, preferably 6 to 10 hours.

[0059] In some embodiments, the reaction is carried out in such a manner that the ratio of the target product to its isomer in the reaction solution is between (2:1) and (30:1), e.g., between (2:1) and (25:1), between (2:1) and (20:1), between (2:1) and (15:1), between (5:1) and (30:1), between (5:1) and (25:1), between (5:1) and (20:1), between (5:1) and (15:1), between (10:1) and (30:1), between (10:1) and (25:1), between (10:1) and (20:1), between (10:1) and (15:1), between (15:1) and (30:1), between (15:1) and (25:1), between (15:1) and (20:1), preferably between (10:1) and (25:1).

[0060] In some embodiments, after conversion, a post-treatment step is also included.

[0061] In some embodiments, workup involves direct concentration under reduced pressure or addition of one or more anti-solvents for the reaction solvent, such as one or more of ethanol, isopropanol, n-butanol, acetone, butanone, methyl isobutyl ketone, ethyl acetate, isopropyl acetate, MTBE, n-heptane, THF, 1,4-dioxane, isopropyl ether, anisole, DCM, ACN, and toluene to precipitate more solids followed by filtration, preferably adding MTBE followed by filtration to obtain the desired product.

[0062] In some embodiments, the method further comprises preparing a compound of formula (III) according to any of the methods described in the first aspect.

[0063] After reacting and treating under the above specific reaction conditions, the ratio of the compound represented by formula (IV) and its isomer increases from about 1:1 to 30-40:1, the purity of the product is further improved, the subsequent removal of isomeric impurities is facilitated, the production cost is reduced, and the process is more suitable for scale-up production.

[0064] In another aspect, the present application provides a method for preparing a compound of formula (I) or a salt thereof, the method comprising removing the amino protecting group of a compound of formula (IV) to obtain a compound of formula (I).

[0065] [ka]

[0066] where R1, R2 and R3 are as defined above.

[0067] The amino protecting group can be removed by methods known in the art, for example, when R3 is Fmoc, the deprotection reaction can be carried out by adding Et2NH.

[0068] In some embodiments, removal of the amino protecting group of a compound of formula (IV) also constitutes a work-up step.

[0069] In some embodiments, the work-up step comprises one to three cycles of concentration, slurry washing, and filtration to obtain the crude compound of Formula (I).

[0070] In some embodiments, the original solution is concentrated to 1 / 4 to 1 / 2, preferably 1 / 3 of its volume, and then acetonitrile is added to form a slurry, followed by continued concentration.

[0071] In some embodiments, the slurry is washed sequentially at a high temperature of 60 to 80°C (preferably 65 to 75°C) and a low temperature of 10 to 40°C (preferably 20 to 30°C), and then the solid is collected by filtration to obtain a crude product of the compound represented by Formula (IV).

[0072] In some embodiments, after the post-treatment is completed, the method further comprises the step of salting out the compound of Formula (I). In some embodiments, salting out refers to reacting the compound of Formula (I) with an acid reagent to obtain a salt of the compound of Formula (I).

[0073] Studies have shown that the choice of acid reagent used has a significant impact on the product stability, salting-out ratio, filtration rate, and efficiency of removing isomeric impurities. In some embodiments, the acid used includes hydrochloric acid, hydrobromic acid, methanesulfonic acid, p-toluenesulfonic acid, camphorsulfonic acid, phosphoric acid, acetic acid, benzoic acid, sulfuric acid, and TFA, preferably methanesulfonic acid.

[0074] In some embodiments, the reaction solvent is one of water, methanol, ethanol, isopropanol, acetonitrile, THF, and 1,4-dioxane, or any combination thereof, preferably a mixed solvent system of methanol and water.

[0075] Research has shown that the order of addition of reagents significantly affects reaction stirring and temperature control. If methanesulfonic acid or water is added last, the reaction solution will release heat vigorously, making temperature control and stirring difficult. In a preferred experimental scheme, methanesulfonic acid is added slowly to a mixture of water and MeOH, and the crude free base product is added all at once last. This process provides effective stirring and allows for easy reaction temperature control.

[0076] In some embodiments, the reaction temperature is 20 to 80° C., preferably 40 to 55° C. Under these temperature conditions, stirring is effective, salting out is complete, and the product is stable.

[0077] In some embodiments, a post-treatment step is further included after salting out.

[0078] In some embodiments, the post-reaction step comprises filtration such as direct filtration, adding water and mixing followed by filtration, adding methanol and mixing followed by filtration, adding EtOH and mixing followed by filtration, adding isopropanol and mixing followed by filtration, adding acetone and mixing followed by filtration, or adding acetonitrile and mixing followed by filtration, preferably adding methanol for crystallization and filtration.

[0079] In some embodiments, the method further comprises preparing a compound of formula (IV) according to any of the methods described above.

[0080] In some embodiments, the method further comprises preparing a compound of Formula (III) according to any of the methods described above.

[0081] In another aspect, the present application provides a method for preparing a drug-linker, including a method for preparing a compound of Formula (I) or a salt thereof according to any of the methods described above, wherein the drug is a compound of Formula (I) or a salt thereof.

[0082] In some embodiments, the method further comprises preparing a compound of formula (IV) according to any of the methods described above.

[0083] In some embodiments, the method further comprises preparing a compound of Formula (III) according to any of the methods described above.

[0084] In another aspect, the present application provides a method for preparing an antibody-drug conjugate, which comprises reacting an antibody with a drug conjugate, wherein the drug conjugate is prepared according to the method described above.

[0085] Beneficial Effects of the Invention This application provides a method for preparing exatecan and its derivatives by optimizing the types and equivalents of reaction reagents, reaction solvents, and temperatures, developing conditions for isomer inversion, and avoiding high temperatures and long reaction times, thereby improving the overall yield of the three-step synthesis from 43% to over 75%, thereby reducing material costs by one-third compared to the original process. Furthermore, the substrate for configuration inversion has a wide range of applications and can be used to synthesize various exatecan compounds and their analogs.

[0086] BRIEF DESCRIPTION OF THE DRAWINGS The drawings described in this specification are used to provide a further understanding of the present invention and constitute a part of this application. The schematic examples of the present invention and their descriptions are used to explain the present invention and are not intended to constitute an undue limitation of the present invention. [Brief explanation of the drawings]

[0087] [Figure 1] FIG. 1 is an HPLC profile of compound 8 prepared in Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0088] Specific Model for Implementing the Invention Hereinafter, the embodiments of the present invention will be described in detail with reference to examples. However, those skilled in the art will understand that the following examples are for the purpose of illustrating the present invention and should not be considered to limit the scope of the present invention. If specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. If the manufacturers of the reagents and instruments used are not specified, they are all commercially available conventional products.

[0089] The meanings of the abbreviations and English terms used in this document are as follows:

[0090] [Table 1]

[0091] Example 1-1: Preparation of Compound 6

[0092] [ka]

[0093] PPA (68.05 g, 201.38 mmol), o-cresol (360 mL), and 1,4-dioxane (360 mL) were added sequentially to a 2 L glass reaction bottle, and stirring was initiated. Compound 5 (90.00 g, 201.38 mmol) and compound 2 (58.31 mmol, 221.51 mmol) were then added. The air was replaced with nitrogen gas three times, and stirring was continued under a N2 atmosphere. Heating was initiated, and the internal temperature was maintained at 85-95 °C, with stirring continued for 12-18 h. The reaction was stopped when the concentration of compound 5 reached less than 1.0% as detected by HPLC.

[0094] Workup: The reaction solution was cooled to <60°C, transferred, and then concentrated under reduced pressure at 50-60°C until no visible dripping of liquid occurred, indicating complete concentration. The concentrated solution was transferred to a 10 L glass bottle, stirring was initiated, and MTBE (5 L) was slowly added to precipitate a large amount of solid, followed by n-heptane (1.4 L). Stirring was continued for 1-2 hours after addition. The mixture was then filtered and dried by suction. The filter cake was washed twice with MTBE (500 mL x 2) and suction filtered until no visible dripping of liquid occurred. The filter cake was collected and dried under vacuum at 40-50°C for 16-24 hours. The crude product, 152.66 g, of compound 6 was obtained (yield: 112.5%, HPLC: 96.44% (46.62% + 49.82%), qNMR: 88%).

[0095] Washing: 150 g of crude compound 6 was collected and added to 4500 mL of 2-MeTHF. The mixture was stirred at room temperature to dissolve the compound. Then, 1500 mL of aqueous NaCl solution was added sequentially. The mixture was stirred for 5-15 minutes and allowed to stand for layering. The organic phase was separated, 750 mL of 2% aqueous sodium sulfite solution and 750 mL of saturated saline solution were added, the mixture was stirred for 5-10 minutes, and the mixture was allowed to stand for layering. The organic phase was separated, 750 mL of 2% aqueous sodium carbonate solution and 750 mL of saturated saline solution were added, the mixture was stirred for 5-10 minutes, and the mixture was allowed to stand for layering. The organic phase was separated, and 750 mL of water and 750 mL of saturated saline solution were added, the mixture was stirred for 5-10 minutes, and the mixture was allowed to stand for layering. The organic phase was separated, and the mixture was concentrated under reduced pressure at 35-45 °C until no clear liquid was dripping, yielding washed compound 6.

[0096] Purification: The washed material was dissolved in 2-MeTHF (450 mL) and heated to 40-60°C (gradual dissolution occurred, and after the mixture became clear, a small amount of solid precipitated). Stirring was continued for 10-20 minutes. MTBE (1800 mL) was slowly added. After the addition, the mixture was slowly cooled to 20-30°C and stirring was continued for 1-3 hours. The filter cake was then filtered and suction dried. The filter cake was washed once with MTBE (300 mL) and suction dried. The filter cake was collected and dried under vacuum at 40-50°C for 16-24 hours. The recovered material gave 120 g of compound 6 (89% overall yield, HPLC: 99.17% (48.75%, 50.42%), QNMR: 96%).

[0097] Example 1-2: Preparation of Compound 6

[0098] [ka]

[0099] PPA (227 mg, 1.5 eq) and 1,4-dioxane (2 ml) were added sequentially to a glass reaction bottle, and stirring was initiated. Compound 5 (200 mg) and Compound 2 (140 mg) were then added. After replacing the air with nitrogen gas three times, stirring was continued under a N2 atmosphere, and heating was initiated. The internal temperature was maintained at 85-95°C, and stirring was continued for 12-18 hours. The reaction was stopped when the concentration of Compound 5 was less than 1.0% as detected by HPLC.

[0100] Workup: The reaction solution was cooled to <60°C, transferred, and then concentrated under reduced pressure at 50-60°C until no more liquid was visibly dripping, indicating complete concentration. 10 mL of MTBE and 3 mL of n-heptane were slowly added, and stirring was continued for 1-2 hours. The mixture was then filtered and dried by suction. The filter cake was washed twice with MTBE and suction filtered until no more liquid was visibly dripping. The filter cake was collected and dried under vacuum at 40-50°C for 16-24 hours. The recovered material gave 370 mg of crude compound 6 (approximately 75% yield).

[0101] Example 2: Preparation of Compound 7

[0102] [ka]

[0103] Compound 6 (114.00 g, 169.10 mmol) and 1,4-dioxane (2280 mL) were added sequentially to a 5 L glass bottle, and stirring was initiated. Hydrochloric acid / 1,4-dioxane (274 mL, 1096 mmol, 4 M) was added, and heating was initiated. The internal temperature was controlled at 40-50 °C, and stirring was continued for 6-10 h. The reaction was stopped when the compound 6:isomer ratio reached 10:1-25:1 as determined by HPLC detection.

[0104] Workup: The reaction solution was cooled for 20-30 min, and MTBE (2600 mL) was slowly added. After the addition, the mixture was cooled to 15-20°C and stirred for 1-3 h. The filter case was washed three times with MTBE (330 mL x 3), suction filtered, and dried. The filter cake was collected and dried under vacuum at 40-50°C for 16-24 h. The recovered material gave 108.3 g of product (yield: 95%, HPLC: 97.18% compound 7 and 2.12% isomers, QNMR: 99%).

[0105] Example 3: Preparation of Compound 8

[0106] [ka]

[0107] Compound 7 (104.44 g, 154.92 mmol) and 1,4-dioxane (627 mL) were added sequentially to a 1 L glass bottle, and stirring was initiated. EtNH (56.65 g, 774.62 mmol) was slowly added while controlling the internal temperature at 20–30°C. After the addition, stirring was continued at this temperature for 18–24 h. The reaction was stopped when the content of compound 7 was confirmed to be less than 1% by HPLC detection.

[0108] Post-treatment: The reaction solution was transferred and concentrated under reduced pressure at 40-50°C to approximately one-third of its original volume. Acetonitrile (530 mL) was added, and slurry washing was performed at room temperature for 1-2 hours. Concentration under reduced pressure was continued until no visible dripping of liquid was observed, and the concentration was completed. Acetonitrile (1060 mL) was added, and the mixture was heated to 65-75°C and slurry washing was performed for 2 hours. After gradually cooling to 20-30°C, stirring was continued for 8-16 hours. The mixture was filtered and dried by suction, and the filter cake was washed once with acetonitrile (200 mL). The filter cake was recovered, and acetonitrile (1060 mL) was added. Slurry washing was performed for 2 hours at 65-75°C. After gradually cooling to 20-30°C, stirring was continued for 3-5 hours. The mixture was filtered and dried by suction, and the filter cake was washed once with acetonitrile (200 mL). The filter cake was recovered and vacuum dried at 40-50°C for 16-24 hours.

[0109] Salting out: Water (255 mL) and methanol (126 mL) were added to a 3 L glass bottle and stirring was initiated. Methanesulfonic acid (255 mL) was slowly added, and the internal temperature was controlled at 20-30°C. After the addition, the above crude free alkali product (60 g, 132.77 mmol) was added in three portions, and the mixture was heated for 40-50°C to react, followed by stirring for 1-2.5 hours. A mixed solution of methanesulfonic acid (126 mL) and methanol (126 mL) was slowly added, and stirring was continued for 1-2 hours. Methanol (1070 mL) was slowly added, causing a large amount of solid to precipitate. After the addition, stirring was continued for 1-2 hours. The mixture was cooled to 20-30°C, and stirring was continued for 3-5 hours.

[0110] After filtration, the cake was dried under suction, rinsed once with methanol (300 mL), and then filtered under suction. The cake was collected and dried under vacuum at 40-50°C for 18-24 hours. The material was recovered to give 65.12 g of product (yield: 90%, HPLC: Compound 8, 99.58%; isomer 0.08%, QNMR: 98%).

[0111] The HPLC analysis of compound 8 is shown in FIG.

[0112] Example 4: Reagent screening experiment for the cyclization reaction of step 1

[0113] [ka]

[0114] Compound 9 was used as a model substrate. 100 mg of compound 9 was added to each reaction, and reacted with compound 2 in 1 ml of solvent to prepare the target compound 10. The progress of the reaction was monitored by HPLC, and the results after 4 hours of reaction are shown in Table 1.

[0115] [Table 2]

[0116] The data in the table above show that Reaction 23 (PPA, o-Crestor) is the fastest reaction, has fewer impurities, is more cost-effective, and can be further optimized for better conditions than the combination of PPA and m-Crestor (Reaction 21).

[0117] Example 5: Solvent screening experiments for step 1 cyclization

[0118] [ka]

[0119] Compound 11 was used as a model substrate. 100 mg of compound 11 was added to each reaction, and 1 equivalent of PPA was added to react with compound 2 to prepare target compound 12. The progress of the reaction was monitored by HPLC. The reaction was carried out at 95°C for 11 hours. The results are shown in Table 2.

[0120] [Table 3]

[0121] The data in the table above showed that the mixed solvent system of o-cresol and 1,4-dioxane had the best reaction compared to the single solvent.

[0122] Example 6: Conditional screening experiment inverting the Step 2 configuration

[0123] [ka]

[0124] Compound 13 was used as a model substrate, and 50 mg of compound 13 was added to each reaction, and 1 ml of solvent was used to screen the ratio of products 14 and 15 under different conditions. The results were as follows:

[0125] [Table 4]

[0126] The data in the table above shows that the highest ratio of target compound 14 was obtained at a reaction temperature of 45°C under the conditions of hydrochloric acid / dioxane.

[0127] Although the specific embodiments of the present invention have been described in detail, it is understood that those skilled in the art can make various modifications and substitutions to these details based on all the teachings disclosed, and these modifications fall within the scope of protection of the present invention. The full scope of the present invention is given by the appended claims and any equivalents thereof.

Claims

1. A method for preparing a compound of formula (III), comprising the step of reacting a compound of formula (II) with compound 2 in the presence of a catalyst, 【Chemistry 1】 In the formula, R １ and R ２ are independently hydrogen, halogen, C １～６ Alkyl, C １～６ Hydroxyalkyl, C １～６ Alkoxyalkyl, C １～６ Alkoxy, C １～４ independently selected from the group consisting of haloalkyl, hydroxyl, and cyano, or R １ and R ２ together with the carbon atoms to which they are attached form a 5- to 6-membered carbocyclic or oxygen-containing heterocyclic ring; R ３ is an electron-withdrawing protecting group; The catalyst was PPTS, AcOH, TFA, H ２ SO ４ , proline, PPA, P ２ O ５ ,CAN,T ３ P, KOH, I ２ , MgCl ２ and TMSCl.

2. 10. The method of claim 1, wherein the catalyst is PPA.

3. 2. The method of claim 1, wherein the compound represented by formula (II) and compound 2 are reacted in a solvent, and the solvent is selected from the group consisting of aromatic hydrocarbons (e.g., toluene, xylene, o-toluene, m-toluene), aliphatic hydrocarbons (e.g., hexane, n-heptane), alcohols (e.g., methanol, ethanol, isopropanol), organic acids (e.g., acetic acid, trifluoroacetic acid), phenols (e.g., phenol, o-cresol, m-cresol, p-cresol), ethers (e.g., ethyl ether, ethylene oxide, anisole), esters (e.g., methyl acetate, ethyl acetate, propyl acetate), ketones (e.g., acetone, butanone), amides (e.g., DMF, DMA), nitriles (e.g., acetonitrile), heterocycles (e.g., NMP, 1,4-dioxane, 2-MeTHF), sulfur-containing organic solvents (e.g., DMSO), and any combination thereof.

4. 4. The method of claim 3, wherein the solvent is a combination of a phenolic solvent and a heterocyclic solvent.

5. 5. The method according to claim 4, wherein the solvent is a mixed solvent of o-cresol and 1,4-dioxane.

6. The following items: (1-1) The volume ratio of o-cresol to 1,4-dioxane is (10:1) to (1:10); (1-2) The molar ratio of the compound represented by formula (II) to compound 2 is (1:1) to (1:1.5); (1-3) The amount of PPA supplied is 0.2 to 5 equivalents based on the compound represented by formula (II); (1-4) reacting the compound represented by formula (II) with compound 2 at 60°C to 140°C; (1-5) reacting the compound represented by formula (II) with compound 2 for 6 to 48 hours; (1-6) The reaction is carried out without gas protection or under nitrogen and argon protection; (1-7) after completion of the reaction, further comprising a post-treatment step to obtain a crude product of the compound represented by formula (III); (1-8) After obtaining the crude product of the compound represented by formula (III) according to item (1-7), the method further comprises a step of washing the crude product of the compound represented by formula (III); (1-9) After the washing step described in item (1-8), a recrystallization step is further included. The method according to any one of claims 1 to 5, characterized by one or more of the following:

7. The volume ratio of o-cresol to 1,4-dioxane is from 10:1 to 1:1; and / or The method according to claim 6, wherein the feed molar ratio of the compound represented by formula (II) to compound 2 is (0.8:1) to (1:1.5).

8. The following items: 1-1) The post-treatment step described in item (1-7) includes a step of quenching by adding water, an aqueous sodium carbonate solution, or an aqueous sodium bicarbonate solution, followed by filtering; or a step of extracting by adding a mixed solvent of DCM and DCM-IPA or 2-MeTHF; or a step of directly concentrating the reaction solution under reduced pressure to remove 1,4-dioxane, followed by diluting with one or more solvents selected from isopropanol, ethyl acetate, acetone, MTBE, PhMe, n-heptane, and ACN, either simultaneously or separately, followed by filtering; 1-2) There is no need to dry the crude product of the compound of formula (III) obtained in item (1-7); 1-3) The washing step described in item (1-8) includes the steps of dissolving the crude product of the compound represented by formula (III) in an organic solvent to obtain an organic phase, washing the organic phase with an aqueous phase 1 to 5 times, and concentrating the organic phase; 1-4) The recrystallization step described in item (1-9) includes dissolving the compound represented by formula (III) in 2-MeTHF and precipitating the crystals with MTBE. The method of claim 6, characterized by one or more of the following:

9. A process for preparing a compound of formula (IV), comprising the step of converting a compound of formula (III) into a compound of formula (IV), 【Chemistry 2】 In the formula, R １ , R ２ and R ３ is as defined in claim 1.

10. 10. The method of claim 9, wherein the conversion is carried out in an organic solvent selected from the group consisting of alcohols (e.g., methanol, ethanol, isopropanol, n-butanol), ketones (e.g., acetone, butanone, methyl isobutyl ketone), esters (e.g., ethyl acetate, isopropyl acetate), ethers (e.g., MTBE, isopropyl ether, anisole), aliphatic hydrocarbons (e.g., n-heptane), heterocycles (e.g., THF, 1,4-dioxane, 2-MeTHF, NMP), amides (e.g., DMF, DMA), sulfur-containing organic solvents (e.g., DMSO), halogenated aliphatic hydrocarbons (e.g., DCM), ammonium (e.g., CAN), aromatic hydrocarbons (e.g., toluene), and any combination thereof.

11. 11. The process according to claim 9 or 10, wherein the conversion is carried out in the presence of an acid.

12. 12. The method of claim 11, wherein the acid is HCl.

13. The following items: (2-1) The conversion is carried out in HCl / 1,4-dioxane; (2-2) The amount of acid supplied is 2 to 20 equivalents based on the compound represented by formula (III); (2-3) The conversion is carried out at 25 to 100°C; (2-4) Stopping the reaction when the ratio of the compound represented by formula (IV) to its isomer is (2:1) to (30:1); (2-5) The conversion takes place within 1 to 24 hours; (2-6) After the conversion, further post-treatment steps are included; (2-7) Further comprising a step of preparing a compound represented by formula (III) according to the method of any one of claims 1 to 8.

13. The method according to any one of claims 9 to 12, characterized by one or more of the following:

14. The following items: 2-1) The post-treatment step according to item (2-7) involves direct concentration under reduced pressure or the addition of one or more anti-solvents among the organic solvents according to claim 10, followed by precipitation of more solids, followed by filtration to obtain the target product; 2-2) The anti-solvent described in Item 2-1) is one or more of ethanol, isopropanol, n-butanol, acetone, butanone, methyl isobutyl ketone, ethyl acetate, isopropyl acetate, MTBE, n-heptane, THF, 1,4-dioxane, isopropyl ether, anisole, DCM, ACN, and toluene.

14. The method of claim 13, characterized by one or more of:

15. A method for preparing a compound of formula (I) or a salt thereof, comprising removing the amino protecting group of a compound of formula (IV) to obtain a compound of formula (I); 【Transformation 3】 In the formula, R １ , R ２ and R ３ is as defined in claim 1.

16. The following items: (3-1) further comprising a post-treatment step after removing the amino-protecting group of the compound represented by formula (IV); (3-2) After the post-treatment described in item (3-1), the method further comprises a step of salting out the compound represented by formula (I); (3-3) Further comprising a post-treatment step after the salting out described in item (3-2); (3-4) The method further comprises the step of preparing a compound represented by formula (IV) by the method according to any one of claims 9 to 14; (3-5) The method further comprises the step of preparing a compound represented by formula (III) by the method according to any one of claims 1 to 8.

16. The method of claim 15, characterized by one or more of:

17. The following items: 3-1) The post-treatment step described in item (3-1) is carried out 1 to 3 times, including concentration, slurry washing, and filtration, to obtain a crude product of the compound represented by formula (I); 3-2) The concentration step described in Item 3-1) refers to concentrating the original solution to 1 / 4 to 1 / 2 of its volume, then mixing it with acetonitrile to form a slurry, and further concentrating it until it is dry; 3-3) The slurry washing described in item 3-1) is carried out successively at a high temperature of 60 to 80°C and a low temperature of 10 to 40°C, and then the solid is collected by filtration to obtain a crude product of the compound represented by formula (I); 3-4) The salting out method according to item (3-2) comprises reacting the compound of formula (I) with an acid reagent to obtain a salt of the compound of formula (I); 3-5) The post-treatment step described in item (3-3) is filtration, for example, direct filtration, filtration after adding and mixing with water, filtration after adding and mixing with methanol, filtration after adding and mixing with EtOH, filtration after adding and mixing with isopropanol, filtration after adding and mixing with acetone, or filtration after adding and mixing with acetonitrile.

17. The method of claim 16, characterized by one or more of:

18. A method for preparing a drug-linker, comprising the step of preparing a compound represented by formula (I) or a salt thereof according to any one of claims 15 to 17, wherein the drug is a compound represented by formula (I) or a salt thereof.

19. A method for preparing an antibody-drug conjugate, prepared by reacting an antibody with a drug-linker, further comprising the step of preparing the drug-linker according to the method of claim 18.

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