A method for preparing enasidenib

Abstract

This invention relates to a method for preparing ennasstat in the field of pharmaceutical synthesis technology. The method involves first hydrolyzing compound 2 with a strong base to generate 7-hydroxy-5-(2-phenylethyl)-[1,2,4]triazolo[1,5-a]pyridine-8-carboxylic acid, which is then reacted in situ with pentanoyl chloride to form a mixed anhydride. This anhydride is then condensed with glycine ester hydrochloride, followed by direct hydrolysis without separation to finally obtain high-quality ennasstat. This invention offers advantages such as safer process, higher product purity and yield, significantly reducing the raw material cost of ennasstat and demonstrating substantial economic and social benefits.

Description

Technical Field

[0001] This invention relates to the field of pharmaceutical synthesis technology, and in particular to a method for preparing ennastine. Background Technology

[0002] On September 25, 2020, Japan approved the marketing of ENAROY (enarodustat), a new oral drug for anemia, for the treatment of anemia associated with chronic kidney disease (CKD).

[0003] New oral drug for anemia: Enararoy (enarodustat), basic drug information:

[0004] Chemical Names:enarodustat,JTZ-951

[0005] CAS Registry Number(s):1262132-81-9

[0006] Molecular Formula:C 17 H 16 N4O4

[0007] Molecular Weight: 340.338

[0008] Its chemical structural formula is as follows:

[0009]

[0010] ENAROY is an orally administered active HIF-PH inhibitor that promotes erythropoietin production by stimulating the endogenous production of erythropoietin and controlling the expression of molecules responsible for iron metabolism. Phase 3 clinical trials have confirmed its efficacy. Efficacy and safety in anemic CKD patients who do not have dialysis, peritoneal dialysis, or hemodialysis.

[0011] In the global market, the HIF-PHI drug field, whether for marketed drugs or products under development, is not yet crowded. However, the ever-increasing sales and broad market prospects have prompted various pharmaceutical companies to invest in the research and development of innovative HIF-PHI drugs.

[0012] In the existing technology, there are two synthetic routes for ennastine:

[0013] 1. The original manufacturer, Japan Tobacco Company, disclosed the process for commercial production of the compound in US2020 / 339563. The preparation method used is as follows: methyl 5,7-dichloro-[1,2,4]triazolo[1,5-a]pyridin-8-yl)carboxylate 2 is used as the key compound in the reaction. It reacts with compound 3 and is hydrolyzed to obtain 7-chloro-5-(2-phenylethyl)-[1,2,4]triazolo[1,5-a]pyridin-8-carboxylic acid (compound 5). Then, compound 5 and glycine methyl ester hydrochloride are amidated using HOBt and EDCI condensing agents to obtain compound 6. Finally, the target product ennasstat is synthesized by hydrolysis.

[0014] Pfizer scientists, in their paper *Org. Process. Res. Dev* (DOI: 10.1021 / acs.oprd.8b00193), described the thermal stability analysis of 45 common amide condensing agents. Molecules containing high-energy functional groups (HEFG), such as 1-hydroxybenzotriazole (HOBt), a known dry explosive, and 1-hydroxyazabenzotriazole (HOAt), often require extensive safety testing for large-scale use to ensure process safety. Furthermore, 1-hydroxybenzotriazole is prone to degradation, producing hydrazine-like structural impurities, and its starting material, chloronitrobenzene, also possesses potential genotoxicity. From a process safety perspective, this commercial production method has several shortcomings, requiring further process improvements.

[0015] Reaction equation:

[0016]

[0017] 2. Both US Patent US2011 / 77267 and journal article [ACS Medicinal Chemistry Letters, 2017, vol. 8, #12, pp. 1320-1325] report the preparation method in the compound discovery stage. Using 7-(benzyloxy)-5-iodo-[1,2,4]triazole[1,5-a]pyridine-8-carboxylic acid tert-butyl ester 25 as a starting material, it is coupled with phenylacetylene via a Sonogashira coupling reaction and ester hydrolysis to obtain compound 26; compound 26 and glycine methyl ester hydrochloride undergo an amidation reaction using HOBt and EDCI condensing agents to obtain SI-4; then, the benzyl group is removed by palladium C-hydrogen desorption to obtain SI-5; finally, the target product ennasstat is synthesized by hydrolysis.

[0018] Compound 26 is a salt of methanesulfonic acid. Using methanol or ethanol as a solvent in subsequent process steps can easily generate methanesulfonate esters, which are potential carcinogens. Furthermore, the final API step uses a palladium-on-carbon catalyst, which increases the need for palladium removal. These potential process defects and risks have led to this method being phased out by the original manufacturer and is unsuitable for commercial production.

[0019] Reaction equation:

[0020]

[0021] In summary, finding a method for preparing ennasstat with advantages such as "safer process, lower raw material cost, higher product purity and yield" has become an urgent technical problem to be solved in commercial production. Summary of the Invention

[0022] The purpose of this invention is to provide a method for preparing ennasstatin that makes the process safer, the product purer and the yield higher, and reduces production costs, thus making it more suitable for commercial production.

[0023] Therefore, the present invention provides a method for preparing ennasstatin, comprising the following steps:

[0024] S1: Prepare compound 3 from compound 2 according to the following reaction formula.

[0025]

[0026] S2: Compound 4 is prepared by reacting compound 3 with acyl chloride according to the following reaction formula, compound 5 is prepared by further adding glycine ester hydrochloride, and compound 1 is obtained by further preparing compound 5.

[0027]

[0028] Wherein, R1OCl is an acyl chloride, and R1 is one of methoxy, ethoxy, isobutoxy, isopropoxy, and pteropentyl.

[0029] R2 is one of methyl, ethyl, or isopropyl.

[0030] Compound 1 is the target product ennasstatin.

[0031] This invention addresses the shortcomings of existing synthetic methods by providing a novel method for preparing ennasstat. In step S1, 7-chloro-5-(2-phenylethyl)-[1,2,4]triazolo[1,5-a]pyridine-8-carboxylic acid (compound 2) is first hydrolyzed with a strong base to generate 7-hydroxy-5-(2-phenylethyl)-[1,2,4]triazolo[1,5-a]pyridine-8-carboxylic acid. This effectively avoids the side reaction of subsequent amide hydrolysis, thereby improving the purity and content of the product. In step S2, 7-hydroxy-5-(2-phenylethyl)-[1,2,4]triazolo[1,5-a]pyridine-8-carboxylic acid is in situ converted into a mixed anhydride. Compound 3 reacts with a mixture of anhydrides to form a reagent, including triphosgene, isobutyl chloroformate (IBCF), isopropyl chloroformate, and tervastatin chloride. The mixed anhydride formed by tervastatin chloride exhibits significant steric hindrance, which facilitates regioselectivity in its reaction with amines. Furthermore, the byproduct tervastatin can be easily removed through post-treatment. After condensation with glycine ester, it is directly hydrolyzed without separation to yield high-quality enanastatin (compound 1). This invention offers advantages such as safer process, higher product purity and yield, significantly reducing the raw material cost of enanastatin and demonstrating substantial economic and social benefits.

[0032] Furthermore, in step S1, the preparation of compound 3 is carried out in the following steps:

[0033] S1-1: In the reaction apparatus, under nitrogen protection, add compound 2 and solvent, heat to 50-90°C, add 50% potassium hydroxide aqueous solution dropwise, and continue the reaction after the dropwise addition is completed; the reaction is terminated when the weight content of compound 2 / (compound 2+compound 3) ≤ 1.0%; the amount of potassium hydroxide used relative to compound 3 is 1 to 10 equivalents, preferably 3 to 6 equivalents.

[0034] S1-2: After the reaction is complete, the pH of the reactants is adjusted to 3-5 with hydrochloric acid. Water is added dropwise to the reaction mixture at 70°C to allow more of the target product to precipitate from the organic solvent. The potassium chloride generated is cooled to 20-30°C. The precipitated crystals are collected by filtration and washed with water. The obtained solid is dried under reduced pressure to obtain compound 3.

[0035] Further, the solvent in step S1 includes 1,4-dioxane, tetrahydrofuran, ethanol, 2-methoxyethanol, 2-propanol, 1-butanol, 2-butanol, water, or mixtures thereof. Preferred solvent is 1-butanol.

[0036] Furthermore, step S2 includes the following sub-steps:

[0037] S2-1: In the reaction apparatus, under nitrogen protection, compound 3 prepared in step S1 is added to the solvent tetrahydrofuran, stirred and cooled to 0-10℃, and the acid-binding agent diisopropylethylamine is added; acyl chloride is added dropwise at about 0-5℃, and after the dropwise addition is completed, the mixture is stirred until the reaction is complete; then glycine ester hydrochloride is added, the temperature is controlled at 0-10℃, the reaction is maintained, and samples are taken for analysis. The reaction is terminated when the weight content of compound 3 / (compound 3+compound 4) ≤ 1.0%.

[0038] S2-2: Add sodium hydroxide aqueous solution dropwise to the reaction solution, heat to 30-50℃, maintain the reaction, take a sample for analysis, and stop the reaction when the content of compound 5 / (compound 5+compound 1) ≤ 1.0% by weight; adjust the pH to 5-7 with hydrochloric acid, cool to 20-30℃, filter to collect the solid, and wash with water and acetone in sequence to obtain the crude product;

[0039] S2-3: Under nitrogen protection, the crude product prepared in step S2-2, isopropanol and water are added to the reaction apparatus, the temperature is raised to 70-80℃, and after the solution becomes clear, the temperature is lowered to 20-30℃, the solid is collected by filtration and washed with isopropanol, and the obtained wet solid is dried under reduced pressure to obtain compound 1.

[0040] The acyl chloride in step S2-1 includes one of methyl chloroformate, ethyl chloroformate, isobutyl chloroformate, isopropyl chloroformate, and pivaloyl chloride. Preferably, pivaloyl chloride.

[0041] The glycine ester hydrochloride in step S2-1 includes one of glycine methyl ester hydrochloride, glycine ethyl ester hydrochloride, and glycine isopropyl ester hydrochloride. Preferably, it is glycine methyl ester hydrochloride. Attached Figure Description

[0042] Figure 1 This is the HPLC chromatogram for the purity detection of ennasstatin in Example 1. Detailed Implementation

[0043] Example 1

[0044] A method for preparing ennasstatin, comprising the following steps:

[0045] S1: Synthesis of compound 3, compound 3 is prepared according to the following reaction formula:

[0046]

[0047] Wherein, Ph is an aromatic group, and in this embodiment, Ph is 2-phenyl, and the corresponding compound 2 is 7-chloro-5-(2-phenylethyl)-[1,2,4]triazolo[1,5-a]pyridine-8-carboxylic acid.

[0048] The specific reaction process is as follows: In a reaction apparatus, under nitrogen protection, 60.2 g of 7-chloro-5-(2-phenylethyl)-[1,2,4]triazolo[1,5-a]pyridine-8-carboxylic acid (compound 2) and 300 ml of 1-butanol were added. The temperature was raised to 50-90℃, and 80.5 g of 50% potassium hydroxide aqueous solution was added dropwise. After the addition was completed, the reaction was continued, and samples were taken for analysis. The reaction was terminated when the weight percentage of compound 2 / (compound 2 + compound 3) ≤ 1.0%. After the reaction, the pH of the reaction mixture was adjusted to 3-5 with hydrochloric acid. 150 ml of water was added dropwise to the reaction mixture at 70℃, and the temperature was lowered to 20-30℃. The precipitated solid was collected by filtration and washed with 100 ml of water. The obtained solid was dried at approximately 50℃ under vacuum to obtain 53.2 g of compound 3, with a yield of 93.9% and an HPLC purity of 99.2%.

[0049] S2: Based on step S1, the synthesis of compound 1 is carried out, and the route is shown in the following formula:

[0050]

[0051] Wherein, R1OCl is an acyl chloride, and R1 is one of methoxy, ethoxy, isobutoxy, isopropoxy, and pteropenyl; in this embodiment, pteropenyl chloride is used.

[0052] R2 is one of methyl, ethyl, or isopropyl; in this example, R2 is methyl, and the corresponding compound added is glycine methyl ester hydrochloride.

[0053] The specific steps are as follows: In a reaction apparatus under nitrogen protection, add 28.3g of compound 3 and 100ml of tetrahydrofuran, stir and cool to 0-10℃, then add 35.2g of diisopropylethylamine as an acid-binding agent. Add 27.5g of pivaloyl chloride dropwise at 0-5℃. After the addition is complete, stir the mixture until the reaction is complete. Then add 13.5g of glycine methyl ester hydrochloride in portions, controlling the temperature at 0-10℃, maintain the reaction, and take samples for analysis. The reaction is terminated when the weight percentage of compound 3 / (compound 3 + compound 4) is ≤1.0%.

[0054] Then, add 80g of 30% sodium hydroxide aqueous solution dropwise to the reaction solution, heat to 30-50℃, maintain the reaction, take a sample for analysis, and stop the reaction when the content of compound 5 / (compound 5 + compound 1) is ≤1.0% by weight. Adjust the pH to 5-7 with hydrochloric acid, cool to 20-30℃, filter and collect the solid, and wash it successively with 100ml of water and 100ml of acetone to obtain the crude product with a weight of 40.5g.

[0055] Under nitrogen protection, 40.5 g of crude product, 500 ml of isopropanol and 100 ml of water were added to the reaction apparatus. The temperature was raised to 70-80 °C. After the solution became clear, the temperature was lowered to 20-30 °C and crystallized for 24 hours. The solid was collected by filtration and washed with 200 ml of isopropanol. The obtained solid was dried at about 60 °C under vacuum to obtain 29.1 g of compound 1, with a yield of 85.2% and an HPLC purity of 99.9%.

[0056] Step S1: With all other substances remaining constant, only the solvent is changed, and the data listed in Table 1 below is obtained:

[0057] Experiment number solvent S1 product yield (%) Purity (%) of product from step S1 1 1,4-Dioxane 86.5 99.2 2 Tetrahydrofuran 89.2 98.9 3 ethanol 88.6 98.1 4 2-Methoxyethanol 85.7 96.3 5 2-Propanol 87.3 98.4 6 1-Butanol 93.9 99.2 7 2-Butanol 87.6 97.2 8 water 84.6 95.8

[0058] The data in the table above shows that in step S1, using 1-butanol as the solvent results in a high yield and the best performance.

[0059] Step S2: With other substances remaining constant, compare the different acyl chlorides and obtain the data listed in Table 2 below:

[0060] Experiment number solvent S2 product yield (%) Purity (%) of product from step S2 1 Isobutyl chloroformate 83.6 99.7 2 Isopropyl chloroformate 82.5 99.7 3 Ethyl chloroformate 80.1 99.8 4 Methyl chloroformate 80.2 99.8 5 pivaloyl chloride 85.5 99.9

[0061] Data shows that using tervaline chloride is the optimal solution.

[0062] Step S2: With all other substances remaining constant, compare different glycine ester hydrochlorides and obtain the data listed in Table 3 below:

[0063]

[0064] Data shows that glycine methyl ester hydrochloride is the optimal solution.

[0065] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A method for preparing ennasstatin, characterized in that, Includes the following steps: S1: Prepare compound 3 from compound 2 according to the following reaction formula. ； S2: Compound 4 is prepared by reacting compound 3 with acyl chloride according to the following reaction formula, compound 5 is prepared by further adding glycine ester hydrochloride, and compound 1 is obtained by further preparing compound 5. ； Wherein, R1COCl is an acyl chloride, and R1 is selected from one of methoxy, ethoxy, isobutoxy, isopropoxy, and pteropentyl. R2 is selected from one of methyl, ethyl, and isopropyl. Step S2 includes the following sub-steps: S2-1: In the reaction apparatus, under nitrogen protection, compound 3 prepared in step S1 is added to the solvent tetrahydrofuran, stirred and cooled to 0-10℃, and the acid-binding agent diisopropylethylamine is added; acyl chloride is added dropwise at 0-5℃, and after the dropwise addition is completed, the mixture is stirred until the reaction is complete; then glycine ester hydrochloride is added, the temperature is controlled at 0-10℃, the reaction is maintained, and samples are taken for analysis. The reaction is terminated when the weight content of compound 3 / (compound 3+compound 4) ≤ 1.0%. The acyl chloride is selected from one of methyl chloroformate, ethyl chloroformate, isobutyl chloroformate, isopropyl chloroformate, and tervaline chloride; the glycine ester hydrochloride is selected from one of glycine methyl ester hydrochloride, glycine ethyl ester hydrochloride, and glycine isopropyl ester hydrochloride. S2-2: Add sodium hydroxide aqueous solution dropwise to the reaction solution, heat to 30-50℃, maintain the reaction, take a sample for analysis, and stop the reaction when the content of compound 5 / (compound 5+compound 1) ≤ 1.0% by weight; adjust the pH to 5-7 with hydrochloric acid, cool to 20-30℃, filter to collect the solid, and wash with water and acetone in sequence to obtain the crude product; S2-3: Under nitrogen protection, the crude product prepared in step S2-2, isopropanol and water are added to the reaction apparatus, the temperature is raised to 70-80℃, and after the solution is clear, the temperature is lowered to 20-30℃, the solid is collected by filtration and washed with isopropanol, and the obtained wet solid is dried under reduced pressure to obtain compound 1. Compound 1 is the target product ennasstatin.

2. The method for preparing ennasstat according to claim 1, characterized in that, In step S1, the preparation of compound 3 is carried out in the following steps: S1-1: In the reaction apparatus, under nitrogen protection, add compound 2 and solvent, heat to 50-90℃, add 50% potassium hydroxide aqueous solution dropwise, and continue the reaction after the dropwise addition is completed; the reaction ends when the weight content of compound 2 / (compound 2+compound 3) ≤ 1.0%; S1-2: After the reaction is complete, the pH of the reactants is adjusted to 3-5 with hydrochloric acid. Water is added dropwise to the reaction mixture at 70°C. The mixture is then cooled to 20-30°C. The precipitated crystals are collected by filtration and washed with water. The obtained solid is dried under reduced pressure to obtain compound 3.

3. The method for preparing ennasstat according to claim 2, characterized in that, The solvent in step S1-1 is selected from 1,4-dioxane, tetrahydrofuran, ethanol, 2-methoxyethanol, 2-propanol, 1-butanol, 2-butanol or water.

4. The method for preparing ennasstat according to claim 3, characterized in that, The solvent in step S1-1 is 1-butanol.

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