Preparation method of indeno [1, 2-b] quinoline-10, 13-diketone derivative

Abstract

The invention relates to an indeno [1, 2-b] quinoline-10, 13-diketone derivative and a preparation method of the indeno [1, 2-b] quinoline-10, 13-diketone derivative. Specifically, the invention relates to a preparation method of a compound as shown in a formula I. The method comprises the step of forming the compound as shown in the formula I from a compound as shown in a formula D-a under an acidic condition. The method can efficiently enrich the compound shown in the formula I, improves the process yield, and is suitable for industrial production. # imgabs0 #

Description

A preparation method of indeno[1,2-b]quinoline-10,13-dione derivative Technical Field

[0001] The present invention belongs to the field of medicine and relates to a method for preparing an indeno[1,2-b]quinoline-10,13-dione derivative. Background Art

[0002] The compound (1S,9S)-1-amino-9-ethyl-5-fluoro-2,3-dihydro-9-hydroxy-4-methyl-1H,12H-benzo[de]pyrano[3',4':6,7]imidazo[1,2-b]quinoline-10,13(9H,15H)-dione) is a camptothecin derivative, a class of topoisomerase I, and has the effects of inhibiting tumor proliferation and having anti-tumor effects.

[0003] EP0495432 discloses a method for preparing the aforementioned compound, which mainly uses compound 1 as a substrate and reacts with compound 2 via a Friedlander reaction to form intermediate 3, followed by removal of the acetyl group under methanesulfonic acid conditions to obtain diastereomers, which are then separated by recrystallization to obtain the optical product.

[0004] The overall process is achiral, yielding diastereomer 4 with a dr ratio of approximately 1:1. The subsequent recrystallization step serves only to purify the optical product. Consequently, the single-step recrystallization yield is approximately 45%, and the overall process yield is less than 41%. For other syntheses, see CN111065621, CN115197088, and CN115197234.

[0005] Summary of the Invention

[0006] The present disclosure provides a method for preparing a compound of formula I or a salt thereof

[0007] The method comprises the steps of forming a compound of formula I from a compound of formula Da under acidic conditions,

[0008] Among them, P 1 is a hydroxyl protection group or hydrogen, such as hydrogen or tert-butyloxycarbonyl; R 1 Selected from hydrogen, halogen or C 1-6 Alkyl, such as methyl; R 2 is selected from hydrogen or halogen, such as fluorine.

[0009] In some embodiments, the acid used in the reaction is selected from hydrogen chloride (HCl) solution. In some embodiments, the acid used in the reaction is HCl / 1,4-dioxane solution, HCl / ethanol solution, HCl / ethyl acetate solution, HCl / isopropanol solution or HCl / isobutanol solution.

[0010] In some embodiments, the solvent used in the reaction of the compound of formula Da is selected from one or more of isobutanol, isopropanol, 3-methyl-2-butanol, ethyl acetate, ethanol, and 1,4-dioxane.

[0011] In other embodiments, the method further comprises the step of reacting a compound of formula A with a compound of formula B to form a compound of formula C.

[0012] where R 1 、R 2 、P 1 As defined above, P 2 is selected from amino protecting groups, such as acetyl.

[0013] The amount (molar amount) of the compound of formula B used in this step is not particularly limited as long as the reaction is ensured. Based on the compound of formula A, it is preferably 0.8 to 1.2 equivalents (eq.), including 0.8 equivalents, 0.9 equivalents, 1 equivalent, 1.1 equivalents, 1.2 equivalents or any value between two numbers.

[0014] In some embodiments, the reaction of the compound of formula A with the compound of formula B is carried out in the presence of an acidic catalyst. Examples thereof may be pyridinium p-toluenesulfonate or methanesulfonic acid. In some embodiments, the amount (molar amount) of the acidic catalyst used in this step is not particularly limited, and is preferably 0.03 to 0.3 equivalents based on the compound of formula A.

[0015] In some embodiments, the reaction of the compound of formula A with the compound of formula B is carried out in a solvent containing cresol or phenol. In some embodiments, the reaction of the compound of formula A with the compound of formula B is carried out in toluene containing o-cresol. Specific reaction conditions / operations can be found in CN111065621, and the relevant content is incorporated herein for illustration.

[0016] In some embodiments, the reaction of the compound of formula A with the compound of formula B is carried out in a solvent containing acetic acid or toluene. In some embodiments, the reaction of the compound of formula A with the compound of formula B is carried out in toluene containing acetic acid. Compared to the presence of o-cresol or phenol, a faster reaction rate can be observed in the presence of acetic acid or toluene. Specific reaction conditions / operations can be found in CN115197088, and the relevant content is incorporated herein for illustration.

[0017] In some embodiments, the reaction temperature of the compound of formula A and the compound of formula B is not limited as long as the reaction proceeds, and is preferably 90-130°C, including but not limited to 90°C, 100°C, 110°C, 120°C, 130°C, or any value therebetween. In some embodiments, the reaction temperature of the compound of formula A and the compound of formula B is a temperature at which toluene is refluxed. The reaction time of this step is not limited as long as the reaction proceeds, and is preferably 16-64 hours.

[0018] Some embodiments provide a preparation method wherein the compound of formula I is

[0019] The method comprises the steps of forming a compound of formula I-1 from a compound of formula D-1a under acidic conditions,

[0020] Some embodiments provide methods for preparing a compound of formula I or a salt thereof,

[0021] The method comprises the step of enriching the compound of formula D in the presence of an acid to obtain the compound of formula I, or the step of enriching the compound of formula I in the presence of an acid,

[0022] Among them, P 1 is a hydroxyl protection group or hydrogen, preferably hydrogen or tert-butyloxycarbonyl; R 1 Selected from hydrogen, halogen or C 1-6 Alkyl, preferably methyl; R 2 is selected from hydrogen or halogen, preferably fluorine.

[0023] In some embodiments, the compound of formula D comprises a compound of formula Da and a compound of formula I.

[0024] The "enrichment" described in the present disclosure is different from the crystallization resolution of diastereomers. Its principle is that under specific conditions, such as in the presence of an acid, a dynamic asymmetric transformation process driven by crystallization is used to convert a non-target configuration product into a target configuration product, thereby achieving the phenomenon of "enrichment" of the target configuration product. For example, in some embodiments of the present disclosure, enrichment refers to the conversion of a compound of formula Da into a compound of formula I in the presence of an acid, or in some embodiments of the present disclosure, enrichment refers to the conversion of a compound of formula D into a compound of formula I in the presence of an acid.

[0025] In some embodiments, the compound of Formula D is a diastereomeric mixture primarily containing two diastereoisomers, Compound 5 and Compound 6, with a dr value of approximately 1:1. In some embodiments, the compound of Formula D, in the presence of an acid, such as a hydrogen chloride solution, can effectively convert the non-target configuration to the target configuration, thereby enriching the compound of Formula I. In some embodiments, the dr value of the compound of Formula D in the presence of an acid, such as a hydrogen chloride solution, is increased from 1:1 to approximately 9:1.

[0026] In some embodiments, compound 6 is converted into compound 5 (or compound of formula I-1) in the presence of an acid.

[0027] The acid used is selected from hydrogen chloride solution. In some embodiments, the acid used in the reaction is HCl / 1,4-dioxane solution.

[0028] In some embodiments, the method further comprises the step of reacting the compound of formula A-1 with the compound of formula B-1 to form a compound of formula C-1.

[0029] Among them, P 2 is selected from amino protecting groups, preferably acetyl.

[0030] In other embodiments, the method further comprises the step of converting Formula C into a compound of Formula D,

[0031] In some embodiments, the compound of formula C is reacted in the presence of an acid, such as, for example, in the presence of methanesulfonic acid and water or in the presence of hydrochloric acid.

[0032] In some embodiments, the solvent used in the reaction of the compound of formula C is not particularly limited, as long as it does not inhibit the reaction, for example, a solvent containing 2-methoxyethanol and ethylcyclohexane is used. In other embodiments, the solvent used in the reaction of the compound of formula C is acetic acid or toluene. In some embodiments, the compound of formula C is subjected to deamino protecting group in toluene containing acetic acid.

[0033] In some embodiments, the reaction temperature for converting the compound of Formula C to the compound of Formula D is not limited as long as the reaction proceeds, and is preferably 90-130°C, including but not limited to 90°C, 100°C, 110°C, 120°C, 130°C, or any value therebetween. In some embodiments, the reaction temperature for converting the compound of Formula C to the compound of Formula D is a temperature at which toluene is refluxed. The reaction time for this step is not limited as long as the reaction proceeds, and is preferably 16-32 hours.

[0034] In some embodiments, the method further comprises the step of converting a compound of formula C-1 into a compound of formula D-1,

[0035] Some embodiments provide a method for preparing a compound of formula I or a salt thereof, comprising the steps of reacting compound 1 with compound 2 to form compound 3, and removing the amino protecting group - acetyl group of compound 3.

[0036] The reaction / or operation in this step is the same as the reaction of the compound of formula A with the compound of formula B. In some embodiments, compound 1 and compound 2 are reacted in the presence of an acidic catalyst. Example embodiments may be pyridinium p-toluenesulfonate or methanesulfonic acid. In some embodiments, compound 1 and compound 2 are reacted in the presence of methanesulfonic acid. Further, compound 1 and compound 2 are reacted in toluene containing acetic acid. Specific reaction conditions / operations can be found in CN115197088, and the relevant content is incorporated herein for illustration.

[0037] In another aspect, the present invention discloses a method for preparing a compound of formula I or a salt thereof, comprising reacting a compound of formula A-1 with a compound of formula B-1 to form a compound of formula C-1, and then deprotecting the compound of formula C-1 to form a compound of formula D-1.

[0038] Among them, P 2 is an amino protecting group, such as acetyl.

[0039] In some embodiments, the method of preparing a compound of Formula I or a salt thereof comprises the following steps:

[0040] Step 1) Compound 1 reacts with Compound 2 to form Compound 3,

[0041] Step 2) Compound 3 is deamino protected to form compound 4 (also known as compound of formula D-1),

[0042] Step 3) the step of enriching compound 5 (or compound of formula I-1),

[0043] In some embodiments, the step of enriching compound 5 (or compound of formula I-1) comprises the step of converting compound 6 into compound 5 (or compound of formula I-1) in the presence of an acid.

[0044] In some embodiments, the acid used for enrichment is selected from a solution of hydrogen chloride. In some embodiments, the acid used for enrichment is a solution of HCl / 1,4-dioxane, a solution of HCl / ethanol, a solution of HCl in ethyl acetate, a solution of HCl / isopropanol, or a solution of HCl in isobutanol.

[0045] On the other hand, the present disclosure also provides a method for preparing compound DC, which comprises the steps of preparing the compound of formula I

[0046] where R 1 、R 2 As defined in claim 1, R 3 、R 4 Each independently selected from hydrogen, deuterium, C 1-3 Alkyl or C 3-6 Cycloalkyl, such as hydrogen, deuterium or cyclopropyl.

[0047] In some embodiments, the method for preparing Compound DC comprises the step of reacting a compound of Formula I with Compound AA to form a compound of Formula DC.

[0048] In some embodiments, compound AA is reacted with a compound of formula I in the presence of a basic reagent to form a compound of formula DC. Examples thereof include N-methylmorpholine or triethylamine. Specific reaction conditions and procedures can be found in WO2020063676, and the relevant content is incorporated herein for illustrative purposes.

[0049] In some embodiments, the compound of formula DC is

[0050] The present disclosure also provides a method for preparing compound DD, which comprises the aforementioned steps of preparing the compound of formula I, or the steps of preparing the compound of formula DC,

[0051] where R 1 、R 2 As defined in claim 1, R 3 、R 4 are each independently selected from hydrogen, deuterium, C 1-3 Alkyl or C 3-6 Cycloalkyl, such as hydrogen, deuterium or cyclopropyl.

[0052] In some embodiments, the method for preparing compound DD further comprises the step of reacting a compound of formula I with compound BB to form a compound of formula DD.

[0053] where R 1 、R 2 As defined above, R 3 、R 4 are each independently selected from hydrogen, deuterium, C 1-3 Alkyl or C 3-6 Cycloalkyl, such as hydrogen, deuterium or cyclopropyl; P 3is an amino protecting group, such as Fomc-. In some embodiments, compound B reacts with a compound of formula I in the presence of a basic reagent to form a compound of formula DD. The base used in the reaction can be N-methylmorpholine or triethylamine. Specific reaction conditions and procedures can be found in WO2020063676, and the relevant content is incorporated herein for illustration.

[0054] In some embodiments, the compound of formula DD is

[0055] Another aspect of the present disclosure provides a method for preparing a compound of formula L, the method comprising the aforementioned steps of preparing a compound of formula I, or the steps of preparing a compound of formula DC, or the steps of preparing a compound of formula DD.

[0056] where R 1 、R 2 As defined above, R 3 、R 4 are each independently selected from hydrogen, deuterium, C 1-3 Alkyl or C 3-6 Cycloalkyl, such as hydrogen, deuterium or cyclopropyl.

[0057] In some embodiments, the method for preparing the compound of formula L further comprises the step of reacting the compound of formula I with the compound of formula L-1,

[0058] where R 1 、R 2 As defined above, R 3 、R 4 are each independently selected from hydrogen, deuterium, C 1-3 Alkyl or C 3-6 Cycloalkyl, such as hydrogen, deuterium or cyclopropyl.

[0059] In some embodiments, the compound of formula L is

[0060] The present disclosure also provides a method for preparing an antibody conjugate, which comprises the aforementioned step of preparing a compound of formula I, or the step of preparing a compound of formula DC, or the step of preparing a compound of formula DD, or the step of preparing a compound of formula DD.

[0061] The present disclosure also provides a method for preparing an antibody conjugate ADC, comprising the aforementioned step of preparing a compound of formula I, or the step of preparing a compound of formula DC, or the step of preparing a compound of formula DD, or the step of preparing a compound of formula DD, and the step of conjugating a compound of formula L to an antibody via a thioether bond.

[0062] where R 1 、R2 As defined above; R 3 、R 4 are each independently selected from hydrogen, deuterium, C 1-3 Alkyl or C 3-6 Cycloalkyl, such as hydrogen, deuterium or cyclopropyl; K is 1-10, such as 1, 2, 3, 4, 5; Ab is an antibody or an antigen-binding fragment thereof.

[0063] In some embodiments, the antibody or antigen-binding fragment thereof is selected from an anti-HER2 (ErbB2) antibody, an anti-EGFR antibody, an anti-B7-H3 antibody, an anti-c-Met antibody, an anti-HER3 (ErbB3) antibody, an anti-HER4 (ErbB4) antibody, an anti-CD20 antibody, an anti-CD22 antibody, an anti-CD30 antibody, an anti-CD33 antibody, an anti-CD44 antibody, or an anti-TROP2 antibody.

[0064] In some embodiments, the antibody conjugate ADC is

[0065] The salts of the compounds / intermediates disclosed herein include, but are not limited to, addition salts of the free form of the compounds / intermediates with acids or bases, wherein the acid used to form the salts includes, but is not limited to, hydrochloric acid or methanesulfonic acid. In some embodiments, the salts of the compounds / intermediates include, but are not limited to, hydrochloride or methanesulfonate.

[0066] The terms "to form" and "to convert" do not necessarily imply a single-step conversion reaction between two substrates; they may be a single-step or multi-step reaction. If an intermediate contains a protecting group, the intermediate is subjected to a one-step removal of the protecting group and then reacted with the corresponding substrate to obtain the corresponding target product.

[0067] The term "antibody" encompasses various antibody structures, including but not limited to monoclonal antibodies, polyclonal antibodies; Monospecific antibodies, multispecific antibodies (e.g., bispecific antibodies), full-length antibodies and antibody fragments (or antigen-binding fragments, or antigen-binding portions), as long as they exhibit the desired antigen-binding activity. "Antigen-binding fragment" encompasses single-chain antibodies (i.e., full-length heavy and light chains); Fab, modified Fab, Fab', modified Fab', F(ab')2, Fv, Fab-Fv, Fab-dsFv, single domain antibodies (e.g., VH or VL or VHH), scFv, divalent or trivalent or tetravalent antibodies. Methods for producing and preparing these antigen-binding fragments are well known in the art (see, e.g., Verma et al., 1998, Journal of Immunological Methods, 216, 165-181).

[0068] The term "antibody drug conjugate" refers to a ligand linked to a biologically active drug via a stable linker. In this disclosure, an "antibody-drug conjugate" (ADC) refers to a monoclonal antibody or antibody fragment linked to a biologically active toxic drug, such as isenotecan or its derivatives, via a stable linker.

[0069] The term "drug loading" can be expressed as the ratio of the amount of drug to the amount of antibody. The range of drug loading can be 1-10 cytotoxic drugs (D) linked to each antibody (Ab). In embodiments of the present disclosure, drug loading is expressed as DAR or k. Low drug loading reduces efficacy, while high drug loading has a negative impact on pharmacokinetics and toxicity. Exemplary values ​​can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or the mean of any two values. Preferably, the mean is 1-8, or 2-8, or 2-7, or 3-8, or 3-7, or 3-6, or 4-7, or 4-6, or 4-5. Conventional methods such as UV / visible spectroscopy, mass spectrometry, ELISA assay, monoclonal antibody size variant assay (CE-SDS) and HPLC characterization can be used to identify the average number of drugs per ADC molecule after the coupling reaction.

[0070] The disclosed monoclonal antibody size variant determination method (CE-SDS) can employ capillary electrophoresis with sodium dodecyl sulfate (CE-SDS) ultraviolet detection to quantitatively determine the purity of recombinant monoclonal antibody products based on molecular weight according to the capillary electrophoresis method (Chinese Pharmacopoeia) under reducing and non-reducing conditions.

[0071] The numerical values ​​disclosed herein are instrumental measurements and are subject to a certain degree of error. Generally speaking, a value within a reasonable error range of plus or minus 10% is considered. The context in which the numerical value is used must of course be considered. For example, the particle size of an active ingredient, where the error after measurement does not exceed plus or minus 10%, may be plus or minus 9%, plus or minus 8%, plus or minus 7%, plus or minus 6%, plus or minus 5%, plus or minus 4%, plus or minus 3%, plus or minus 2%, or plus or minus 1%, preferably plus or minus 5%.

[0072] The pharmaceutically acceptable salts of the compounds described herein or their salts may be selected from inorganic or organic salts, including "acid" addition salts and "base" addition salts. For example, salts formed by acid-base reactions with basic groups (amino groups), wherein the acid comprises an organic acid or an inorganic acid.

[0073] In the chemical structures of the compounds disclosed herein, the bond Indicates that the configuration is not specified, that is, if chiral isomers exist in the chemical structure, the bond Can be or include both Two configurations. Indicates the presence of chiral isomers in the structure, and also contains Two configurations.

[0074] In this disclosure, an "antibody conjugate" refers to a ligand linked to a biologically active drug via a stable linker. In this disclosure, an "antibody-drug conjugate" refers to a monoclonal antibody or antibody fragment linked to a biologically active toxic drug, such as isenotecan or its derivatives, via a stable linker.

[0075] The term "alkyl" refers to a saturated aliphatic hydrocarbon group, including alkyl groups having 1 to 6 carbon atoms. Non-limiting examples include methyl, ethyl, n-propyl, isopropyl.

[0076] The term "cycloalkyl" refers to a saturated monocyclic or polycyclic hydrocarbon substituent, wherein the cycloalkyl ring contains 3 to 6 carbon atoms. Non-limiting examples of monocyclic cycloalkyls include cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl, cyclohexadienyl, and the like; polycyclic cycloalkyls include spirocyclic, cycloparacyclic, and bridged cycloalkyls.

[0077] "Halogen" refers to fluorine, chlorine, bromine or iodine.

[0078] The "protecting groups" disclosed herein, such as "hydroxyl protecting groups" and "amino protecting groups," are groups known in the art that can be used to protect hydroxyl or amino groups, as described in the literature (Protective Groups in Organic Synthesis, 5th Ed. TW Greene & P.GMWuts). Examples of amino protecting groups include, but are not limited to, acetyl or Fomc. DETAILED DESCRIPTION

[0079] The present disclosure is further described below with reference to examples, but these examples are not intended to limit the scope of the present disclosure.

[0080] Experimental methods in the examples of this disclosure that do not specify specific conditions are generally based on conventional conditions or the conditions recommended by the raw material or product manufacturers. Reagents without specific sources are conventional reagents purchased from the market.

[0081] The structures of the compounds were confirmed by nuclear magnetic resonance (NMR) and / or mass spectroscopy (MS). NMR shifts (δ) are given in units of 10-6 (ppm).

[0082] NMR measurements were performed using a Bruker AVANCE-400 nuclear magnetic spectrometer, and the solvent was deuterated chloroform (CDCl3).

[0083] MS was determined using a Waters Micromass Quattro micro API triple quadrupole mass spectrometer in positive / negative ion mode with a mass scan range of 120-1300.

[0084] HPLC conditions (applicable to intermediates G, intermediate H, intermediate H-1, intermediate H-2, intermediate I-1, and intermediate I-2): chromatographic column: octadecylsilane bonded silica gel as filler (Agilent Zorbax Bonus-RP C18, 4.6 mm×150 mm, 3.5 μm), column temperature: 30°C, detection wavelength: 240 nm; mobile phase: phosphate buffer as mobile phase A, methanol as mobile phase B; the retention time of intermediate G is approximately 17 to 20 min, the retention time of intermediates H-1 and intermediate I-1 is approximately 7 to 8 min, and the retention time of intermediates H-2 and intermediate I-2 is approximately 9 to 10 min.

[0085] The thin layer chromatography silica gel plate used was Yantai Huanghai HSGF254 silica gel plate. The specification of the silica gel plate used in thin layer chromatography (TLC) was 0.2 mm ± 0.03 mm. The specification used for thin layer chromatography separation and purification products was 0.4 mm - 0.5 mm.

[0086] Embodiment 1:

[0087] Step 1:

[0088] Add 90 g of intermediate E, 86.7 g of intermediate F, 180 ml of acetic acid, 6.03 g of methanesulfonic acid, and 900 ml of toluene to a reaction flask and heat to reflux. After the reaction is complete, add 900 ml of toluene, cool to below room temperature, filter, and dry to obtain intermediate G.

[0089] Step 2: Add 3.5 L of 8M hydrochloric acid, 750 mL of anhydrous acetic acid, 1.5 L of toluene, and Intermediate G (153 g) to a reaction flask and stir thoroughly. Heat to reflux. After the reaction is complete, cool to room temperature and filter through a filter funnel covered with 300 g of celite. Wash the filter cake with 3 L of a 1:1 methanol:purified water mixture and concentrate to yield 153 g of Product H. HPLC analysis revealed a dr value of 52%:48%.

[0090] Step 3:

[0091] To a reaction flask, add 72 g of the product from Step 2, 1080 ml of isobutanol, and 1400 ml of a 1M HCl / 1,4-dioxane solution. Heat to 60°C with stirring and react. After completion, cool to room temperature and concentrate under reduced pressure at 45°C until no visible droplets remain, yielding a crude yellow product. HPLC analysis revealed a dr value (content ratio) of 90%:10%.

[0092] Step 4: Add 6N hydrochloric acid solution (1080 ml) and the yellow crude product obtained in step 3 to the reaction flask, heat to 45°C, pave 300 g of diatomaceous earth with a suction filtration funnel, filter, and wash the filter cake with 6N hydrochloric acid solution; transfer the filtrate to a reaction flask, heat to 45°C, and add 2.88 L of methanol dropwise; after the addition is complete, cool to room temperature; filter with suction, wash the filter cake with anhydrous methanol, 50 ml each time, and transfer the filter cake to a vacuum drying oven at 20-25°C and dry for 12-15 h to obtain 55.4 g of compound H-1, with a dr value of 99%:1% by HPLC. The total yield of steps E to H-1 is 75%.

[0093] Example 2:

[0094] To the reaction flask was added 0.5 g of the product obtained in step 2 of Example 1, 20 V volume of isobutanol solvent (10 ml) was added, and then 10 V volume of HCl / 1,4-dioxane solution (1 M, 5 ml) was slowly added. The mixture was heated to 60 ° C. and stirred for 20 hours. The mixture was cooled to room temperature and concentrated. The sample was taken and detected by HPLC. The content ratio of diastereomers H-1 / H-2 was 92.8% / 7.2%.

[0095] Example 3:

[0096] To the reaction flask was added 0.5 g of the product obtained in step 2 of Example 1, 15 V volume of isobutanol solvent (7.5 ml) was added, and then 15 V volume of HCl / 1,4-dioxane solution (1 M, 7.5 ml) was slowly added. The mixture was heated to 60 ° C. and stirred for 20 hours. The mixture was cooled to room temperature and concentrated. The sample was taken and detected by HPLC. The content ratio of diastereomers H-1 / H-2 was 92.1% / 7.9%.

[0097] Embodiment 4:

[0098] To the reaction flask was added 0.5 g of the product obtained in step 2 of Example 1, 15 V volume of isobutanol solvent (7.5 ml) was added, and then 15 V volume of HCl / 1,4-dioxane solution (2 M, 7.5 ml) was slowly added. The mixture was heated to 60 ° C. and stirred for 20 hours. The mixture was cooled to room temperature and concentrated. The sample was taken and detected by HPLC. The content ratio of diastereomers H-1 / H-2 was 92.2% / 7.8%.

[0099] Example 5:

[0100] To the reaction flask was added 0.5 g of the product obtained in step 2 of Example 1, and 15 V of HCl / isopropanol solution (4 M, 7.5 ml) was slowly added. The mixture was heated to 60° C. and stirred for 20 hours. The mixture was cooled to room temperature and concentrated. The mixture was sampled and analyzed by HPLC. The content ratio of diastereomers H-1 / H-2 was 89.5% / 10.5%.

[0101] Example 6:

[0102] To the reaction flask was added 0.5 g of the product obtained in step 2 of Example 1, 15 V volume of 3-methyl-2-butanol solvent (7.5 ml) was added, and then 15 V volume of HCl / 1,4-dioxane solution (1 M, 7.5 ml) was slowly added. The mixture was heated to 60 ° C. and stirred for 20 hours. The mixture was cooled to room temperature and concentrated. The sample was taken and detected by HPLC. The content ratio of diastereomers H-1 / H-2 was 83.2% / 16.8%.

[0103] Example 7:

[0104] To the reaction flask was added 0.5 g of the product obtained in step 2 of Example 1, 15 V volume of isobutanol solvent (7.5 ml) was added, and then 15 V volume of HCl / ethyl acetate solution (4 M, 7.5 ml) was slowly added. The mixture was heated to 60° C. and stirred for 20 hours. The mixture was cooled to room temperature and concentrated. The mixture was sampled and analyzed by HPLC. The content ratio of diastereomers H-1 / H-2 was 84.8% / 15.2%.

[0105] Example 8:

[0106] To the reaction flask was added 0.5 g of the product obtained in step 2 of Example 1, 15 V volume of isobutanol solvent (7.5 ml) was added, and then 15 V volume of HCl / ethanol solution (4 M, 7.5 ml) was slowly added. The mixture was heated to 60° C. and stirred for 20 hours. The mixture was cooled to room temperature and concentrated. The mixture was sampled and analyzed by HPLC. The content ratio of diastereomers H-1 / H-2 was 85.0% / 15.0%.

[0107] Example 9:

[0108] To the reaction flask was added 0.5 g of the product obtained in step 2 of Example 1, 15 V volume of isobutanol solvent (7.5 ml) was added, and then 5 V volume of hydrobromic acid (content ≥40%, 2.5 ml) was slowly added. The mixture was heated to 60 ° C and stirred for 20 hours. The mixture was cooled to room temperature and concentrated. The sample was taken and the HPLC analysis showed that the content ratio of diastereomers H-1 / H-2 was 62.2% / 37.8%.

[0109] Example 10:

[0110] To the reaction flask, 0.5 g of the product obtained in step 2 of Example 1 was added, 15 V volume of isobutanol solvent (7.5 ml) was added, and then 5 V volume of concentrated sulfuric acid (2.5 ml) was slowly added. The mixture was heated to 60° C. and stirred for 20 hours. The mixture was cooled to room temperature and concentrated. The mixture was sampled and analyzed by HPLC. The content ratio of diastereomers H-1 / H-2 was 52.7% / 47.3%.

[0111] Example 11:

[0112] To the reaction flask, 0.5 g of the product obtained in step 2 of Example 1 was added, 15 V volume of isobutanol solvent (7.5 ml) was added, and then 5 V volume of perchloric acid (2.5 ml) was slowly added. The mixture was heated to 60° C. and stirred for 20 hours. The mixture was cooled to room temperature and concentrated. The sample was taken and analyzed by HPLC. The content ratio of diastereomers H-1 / H-2 was 52.5% / 47.5%.

[0113] Example 12:

[0114] To the reaction flask, 0.5 g of the product obtained in step 2 of Example 1 was added, followed by 2.7 ml of methanesulfonic acid (5.4 V) and 0.6 ml of purified water (1.2 V), and the mixture was heated to 45° C. and stirred for 30 min; 10 ml of methanol (18 V) was added dropwise, and after the addition was complete, the temperature was maintained and stirred for 3 h; the mixture was naturally cooled to 25° C., and a sample was taken for HPLC detection, where the diastereoisomer H-1 / H-2 content ratio was 51.5% / 48.5%.

[0115] Example 13:

[0116] Step 1:

[0117] Add 155.5 g of intermediate E, 150.0 g of intermediate F and 2.8 L of toluene to the reaction flask, stir, add 10.5 g of methanesulfonic acid and 622 mL of acetic acid, and after the reflux reaction is completed, cool and concentrate the reaction solution until there is almost no liquid dripping to obtain intermediate G;

[0118] Step 2:

[0119] To the reaction flask, the intermediate G obtained in the previous step, 1.6 L of toluene, 3.110 L of purified water and 1.555 L of methanesulfonic acid were added and stirred. After the reflux reaction was completed, the temperature was lowered to 60-65 ° C, filtered (with diatomaceous earth as the filter aid), and the filter cake was washed with 2 × 1.0 L of a mixed solution of methanol and water (volume ratio 1:1). The filtrate and the washing liquid were combined and sampled for HPLC detection. The content ratio of diastereomers I-1 / I-2 was 50.2% / 49.8%;

[0120] Step 3:

[0121] The filtered liquid was concentrated under reduced pressure until no liquid remained; the concentrated liquid was transferred to a reaction flask, stirred, and heated to 45°C. 5.597 L of methanol was added dropwise, followed by 311 mL of purified water. After cooling to room temperature, the mixture was filtered, and the filter cake was washed with 2 L of methanol. The resulting filter cake was placed in a drying oven at 20-25°C and dried for 12-15 h to obtain 115.0 g of intermediate I-1. The dr value determined by HPLC was 97%:3%, and the total yield of the three steps (compound E to I-1) was 39.0%.

Claims

1. Method for preparing a compound of formula I or a salt thereof The method comprises the steps of forming a compound of formula I from a compound of formula Da under acidic conditions, Where P 1 is a hydroxyl protection group or hydrogen, preferably hydrogen or tert-butyloxycarbonyl; R 1 Selected from hydrogen, halogen or C 1-6 Alkyl, preferably methyl; R 2 Selected from hydrogen or halogen, preferably fluorine.

2. The process according to claim 1, wherein the acid is selected from hydrogen chloride solution.

3. The method according to claim 1 or 2, wherein the solution used for the reaction is selected from one or more of isobutanol, isopropanol, 3-methyl-2-butanol, ethyl acetate, ethanol, and 1,4-dioxane.

4. The method according to any one of claims 1 to 3, further comprising the step of reacting the compound of formula A with the compound of formula B to form a compound of formula C, Where R 1 , R 2 , P 1 As defined in claim 1, P 2 is selected from amino protecting groups, preferably acetyl.

5. The method according to claim 1-4, wherein the compound of formula I is The method comprises the steps of forming a compound of formula I-1 from a compound of formula D-1a under acidic conditions, 6. A method for preparing a compound of formula I or a salt thereof, The method comprises the step of enriching the compound of formula I with the compound of formula D in the presence of an acid, Where P 1 is a hydroxyl protection group or hydrogen, preferably hydrogen or tert-butyloxycarbonyl; R 1 Selected from hydrogen, halogen or C 1-6 Alkyl, preferably methyl; R 2 Selected from hydrogen or halogen, preferably fluorine.

7. The method according to any one of claims 1 to 6, comprising reacting a compound of formula A-1 with a compound of formula B-1 to form a compound of formula C-1, followed by deprotection of the compound of formula C-1 to form a compound of formula D-1, Where P 1 is a hydroxyl protecting group or hydrogen, preferably hydrogen or tert-butyloxycarbonyl; 2 is an amino protecting group, preferably acetyl.

8. A method for preparing compound DC, comprising the steps of any one of claims 1 to 7, Where R 1 , R 2 As defined in claim 1, R 3 , R 4 are each independently selected from hydrogen, deuterium, C 1-3 Alkyl or C 3-6 Cycloalkyl, for example hydrogen, deuterium or cyclopropyl.

9. A method for preparing compound DD, comprising the steps of any one of claims 1 to 8, Where R 1 , R 2 As defined in claim 1, R 3 , R 4 are each independently selected from hydrogen, deuterium, C 1-3 Alkyl or C 3-6 Cycloalkyl, for example hydrogen, deuterium or cyclopropyl.

10. A method for preparing a compound of formula L, The method comprises the steps of any one of claims 1 to 8, and the step of reacting a compound of formula I with a compound of formula L-1, Where R 1 , R 2 As defined in claim 1, R 3 , R 4 are each independently selected from hydrogen, deuterium, C 1-3 Alkyl or C 3-6 Cycloalkyl, for example hydrogen, deuterium or cyclopropyl.

11. A method for preparing an antibody conjugate, the method comprising the steps of any one of claims 1 to 10.

12. A method for preparing an antibody conjugate ADC, the method comprising the steps of any one of claims 1 to 10, and a step of conjugating formula L to an antibody via a thioether bond, Where R 1 , R 2 As defined in claim 1; R 3 , R 4 are each independently selected from hydrogen, deuterium, C 1-3 Alkyl or C 3-6 Cycloalkyl, such as hydrogen, deuterium or cyclopropyl; K is 1-10; Ab is an antibody or an antigen-binding fragment thereof.

13. The method according to claim 12, wherein the antibody is an anti-HER2 antibody, an anti-HER3 antibody or an anti-TROP2 antibody.

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