An improved process for highly pure roxadustat

Abstract

The objective of the present invention is to provide a method for preparing Roxadustat that economically viable, suitable for industrial-scale production and achieving high purity and high yield.

Description

[0001] DESCRIPTION

[0002] AN IMPROVED PROCESS FOR HIGHLY PURE ROXADUSTAT

[0003] Technical Field

[0004] The invention relates to an improved method for synthesis of 2-(4-hydroxy-l-methyl-7-phenoxyisoquinoline-3-carboxamido) acetic acid (Roxadustat).

[0005] Background Art

[0006] Roxadustat is chemically known as 2-[(4-Hydroxy-l-methyl-7-phenoxyisoquinoline-3-carbonyl) amino] acetic acid (CAS No: 808118-40-3) and represented by the following structural formula:

[0007]

[0008] Roxadustat (compound I) is used for treatment of adult patients with symptomatic anemia associated with chronic kidney disease (CKD) ischemia, and hypoxia as an oral small molecule inhibitor of HIF prolyl hydroxylases, or HIF-PHs, which is marketed under the brand name Evrenzo in the EU and JP.

[0009] Arend et al. in US7323475B2 provided the first disclosure for isolation of compound I, Example D-81 by referring Example D-78, discloses a process for preparation of roxadustat as given below in Scheme 1.OH O OH O

[0010]

[0011] Roxadustat

[0012] Scheme 1

[0013] The drawbacks of the process depicted in Scheme 1, the method involves a large number of experimental steps and usually requires noble metal catalysis beside requiring purification by column chromatography. These factors contribute to low yields and high costs, making the synthesis process unsuitable for large-scale production.

[0014] Numerous synthetic methods for the preparation of Roxadustat and its intermediates, particularly the isoquinoline core depicted in Scheme 2, have been reported in the literature such as CN106478503A, CN104024227A, CN106083720A, CN104892509A, CN106478503A, US9206134B2, WO2014014834A1, WO2018072662, WO2019114811A1 W02021020998 and Org. Process Res. Dev. 2022, 26, 915-924.

[0015] OH O

[0016]

[0017] R= -H, -CH3, -CH2CH3, -CH2Ph

[0018] Scheme 2Píša et al. (Org. Process Res. Dev. 2022, 26, 915-924) critically assessed the existing synthesis routes in the literature, highlighting their lack of feasibility and reproducibility. Píša et al. proposed a more suitable and reliable process (Scheme 3) for pharmaceutical production, taking into account overall yield and scalability.

[0019] 1) DMSO, K2CO3COOH phenol 2) KOH Br

[0020] DMF, Pd(OAc), DPEPhos, EDIPA OBu if

[0021] AON, DBU - o ►

[0022]

[0023] glycine Roxadustat

[0024] Scheme 3

[0025] During the retrosynthetic design process, they also evaluated and identified potential process impurities step by step. However, they did not address the occurrence of a DBU hydrolysis impurity in the final step of this synthetic pathway. Although unsaturated nitrogenous bases such as l,8-Diazabicyclo(5.4.0)undec-7-ene (DBU) offer versatile and broad utility, they are prone to hydrolysis, potentially leading to the formation of reactive primary amines.

[0026] Goncalves et al. (Amino Acids, 2011, 40, 197) have reported the complete hydrolysis of DBU by refluxing in water or at ambient temperature with potassium hydroxide (KOH).

[0027] Hyde et al. (Org. Process Res. Dev. 2019, 23, 1860—1871) highlighted the formation of a process impurity due to the occurrence of a primary amine l-(3-Aminopropyl)azepan-2-one (Compound III) resulting from the hydrolysis of DBU (Scheme 4) for Uprifosbuvir API. This study emphasized that the hydrolysis impurity, Compound III, may likely be present in commercially purchased DBU.. Additionally, the formation of thi impurity is influenced by the water content in the solvents used during reactions.Water

[0028] Reflux

[0029]

[0030] Compund III

[0031] DBU hydrolysis product

[0032] Scheme 4

[0033] In the final step of the synthetic process developed by Pisa et al., as shown in Scheme 3, they stated that anhydrous acetonitrile (ACN) was used. However, no information is provided regarding the presence of Compound III in DBU. For pharmaceutical production on a large scale, using anhydrous solvents or implementing solvent drying systems is neither cost- effective nor feasible. If pure ACN needs to be used as a solvent in a pharmaceutical manufacturing process, HPLC-grade ACN is typically used. The water content in commercially available HPLC-grade ACN is reported between 0.02 - 0.03% on analysis certificates. In this case, the generation of Compound III and its condensation with the intermediate Compound II under reflux conditions during the manufacturing of Roxadustat is unquestionable, leading to the formation of the process impurity Compound IV (Scheme IV). The formation of this impurity (Compound IV) during the production of Roxadustat necessitates additional purification processes, such as recrystallization or extraction causing loss of yield and extra, process steps.

[0034] OH O

[0035] Solvent A

[0036] Compund III DBU hydrolysis product Compound IV

[0037]

[0038] DBU hyrolysls Impurity of Roxadustat Scheme IV

[0039] Based on these considerations, there still appears a need for preparing Roxadustat, specifically one that is easily applicable, cost-effective, and feasible for industrial-scale production.

[0040] Summary of the invention

[0041] The objective of the present invention is to provide a method for preparing Roxadustat thatutilizes readily available raw materials, employs a concise and environmentally friendly process, and is economically viable and suitable for industrial-scale production, achieving high purity and high yield.

[0042] Technical Problem

[0043] Active pharmaceutical ingredients (APIs) are individual components that are used as a part of finished pharmaceutical drug or medicinal product, where they provide the pharmacological activity.

[0044] While minor impurities during research and development studies for APIs may seem insignificant, they can lead to a major catastrophe when scaled up to API industrial manufacturing. An impurity can completely alter a formulation, potentially transforming it into something entirely different due to unpredictable chemical reactions. This not only results in significant time loss but also economically burdensome. Consequently, API manufacturers emphasize the need for reproducible and reliable synthesis pathways to ensure the production of high-quality APIs.

[0045] To address this need for Roxadustat, studies have been conducted to develop a new manufacturing process that offers advantageous properties, making it a suitable alternative to DBU for a similar class of reaction.

[0046] Solution to Problem

[0047] The objective of this invention is to provide an improved and straightforward process using a non-hydrolyzable base for the preparation of Roxadustat with high yield and purity.

[0048] Description of embodiments

[0049] The present invention put forward an enhanced method that involves reacting ethyl 4-hydroxy-l-methyl-7-phenoxyisoquinoline-3 -carboxylate (Compound II) with glycine in the presence of a suitable base and solvent to produce Roxadustat. This improved method is described in Scheme V.

[0050] OH O OH O

[0051]

[0052] Roxadustat Compund II

[0053] Scheme VThis application provides a method for synthesis of Roxadustat in high purity, including the following steps:

[0054] a) providing a mixture by addition of solvent, ethyl 4-hydroxy-l-methyl-7-phenoxyisoquinoline-3-carboxylate (Compound II) and glycine,

[0055] b) adding the base to the mixture,

[0056] c) then stirring the mixture at a suitable temperature for a suitable time,

[0057] d) cooling the mixture at a suitable temperature,

[0058] e) adding a suitable solvent into the mixture,

[0059] f) adjusting pH to the appropriate range with HC1 (aq.) and stirring the mixture at a suitable temperature for a suitable time,

[0060] g) filtering the crystals, washing with a suitable solvent, and

[0061] h) drying the crystals under a vacuum at the specified temperature

[0062] The appropriate ethyl 4-hydroxy-l-methyl-7-phenoxyisoquinoline-3 -carboxylate (Compound II) and glycine amount used in step (a) is between 1.0 - 2.0 equivalent.

[0063] Wherein suitable solvent in step (a) is selected from; water, 2-propanol, 1 -propanol, 1 -butanol, 2-butanol, tert-butyl alcohol, 1 -pentanol, 2-pentanol, amyl alcohol, ethylene glycol, glycerol, acetone, butanone, 2-pentanone, 3 -pentanone, methyl butyl ketone, methyl isobutyl ketone, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, tert-butyl acetate, isobutyl acetate, toluene, xylene, chloroform, dichloromethane, carbon tetrachloride, ethylene dichloride, chlorobenzene, acetonitrile, diethyl ether, diisopropyl ether, tert-butyl methyl ether, dibutyl ether, tetrahydrofuran (THF), 1,4-dioxane, 2-methoxyethanol, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), pyridine, dimethyl sulfoxide (DMSO), sulfolane, formamide, acetamide, propanamide, pyridine or mixtures thereof.

[0064] The base employed in step (b) is selected from tetra-alkyl ammonium hydroxides or benzyltrialkyl ammonium hydroxides such as benzyltrimethylammonium hydroxide (Triton B), benzyltriethylammonium hydroxide, tetrametylammonium hydroxide (TMAH), tetraetylammonium hydroxide (TEAH), tetrabutylammonium hydroxide (TBAH), tetrapropylammonium hydroxide (TP AH) etc. The appropriate base amount is between 1.0 -2.0 equivalent.

[0065] The suitable temperature used in step (c) is selected from room temperature to reflux temperature of the solvent used. The suitable time used in stirring the mixture in step (c) is between 1 - 16 hours.

[0066] The suitable temperature used in step (d) is selected from room temperature to -20 °C.

[0067] Wherein suitable solvent in step (e) is selected from, water, 2-propanol, 1 -propanol, 1 -butanol, 2-butanol, tert-butyl alcohol, 1 -pentanol, 2-pentanol, amyl alcohol, ethylene glycol, glycerol, acetone, butanone, 2-pentanone, 3-pentanone, methyl butyl ketone, methyl isobutyl ketone, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, tert-butyl acetate, isobutyl acetate, toluene, xylene, chloroform, dichloromethane, carbon tetrachloride, ethylene dichloride, chlorobenzene, acetonitrile, diethyl ether, diisopropyl ether, tert-butyl methyl ether, dibutyl ether.

[0068] The suitable range to adjust pH in step (f) is 0 - 6.

[0069] The suitable temperature to adjust pH used in step (f) is from -20 °C to 35 °C.

[0070] The suitable time used to stir the mixture in step (f) between 1 - 16 hours.

[0071] The suitable temperature to dry the product in step (g) is from 50 °C to 90 °C.

[0072] The suitable time used to dry the product in step (g) between 1 - 16 hours.

[0073] The improved method is described in Scheme V affording high purity products with high yields. It is simple, repeatable, cost-effective and suitable for industrial scale manufacturing.

[0074] The processes described in Scheme V are easy to handle, environmentally friendly, and offer improved yields with high purity, making them simple, repeatable, cost-effective and suitable for industrial-scale application. The degree of purity of the active ingredient and the resulting possible changes of the efficacy, further important properties for the pharmaceutical processing can be affected in an adverse manner, e.g. the capability to be pressed to form tablets by an impairment of the pourability or flowability of the crystalline form.

[0075] Specific aspects and embodiments of the invention will be further detailed in the following examples, which are provided solely for illustrative purposes and should not be interpreted as limiting the scope of the invention in any way.

[0076] Brief description of the drawings:

[0077] Fig. 1 shows the1H NMR spectra of compound IVFig. 2 shows the13C NMR of compound IV

[0078] Fig. 3 shows the1H NMR spectra of Roxadustat

[0079] Fig. 4 shows the13C NMR of Roxadustat

[0080] Fig. 5 shows the HPLC chromatogram of comparison example

[0081] Instrument parameters:

[0082] NMR parameters

[0083] 1H and13C NMR spectra were recorded on a JEOL 400 MHz NMR spectrometer. Chemical shifts 6 are reported in parts per million (ppm) relative to the residual protons in the NMR solvent (DMSO-d6: δ2.5 and carbon resonance of the solvent (DMSO-d6: δ40.00; CDCl3: 7.26 and carbon resonance of the solvent CDCl3: 77.00). NMR peak multiplicities were given as follows: s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, quint = quintet, br = broad, C, CH, CH2, CH3.

[0084] HPLC parameters

[0085] Column: Zorbax SB-Phenyl, 250 x 4.6 mm, 5 pm

[0086] Column temperature: 35 °C

[0087] Sample temperature: 25 °C

[0088] Injection volume: 10 pL

[0089] Flow rate: l. O mL / min.

[0090] Detector: UV, 260 nm

[0091] Elution: Gradient

[0092] Gradient Program

[0093] Mobile Phase: A: 10mM KH2PO4 buffer, pH 3.0 (adjusted with 30%H3PO4), B: ACN Time (min) Mobile Phase A (%) Mobile Phase B (%) — 50 50 5 50 50 30 40 60 30.1 50 50 35 50 50

[0094]

[0095] Retention times:Compound II: 16.65 min

[0096] Compound IV: 21.33 min

[0097] Roxadustat: 9.94 min

[0098] The following examples are provided to enable one skilled in the art to practice the invention and are merely illustrative of the invention. The examples should not be read as limiting the scope of the invention.

[0099] EXAMPLES

[0100] Example 1: Preparation of Compound IV (4-hydroxy-l-methyl-V-(3-(2-oxoazepan-l-yl)propyl)-7-phenoxyisoquinoline-3-carboxamide)

[0101] THF: Water, DBU 80°C, 16h.

[0102]

[0103] A 250 mL two-necked, round bottomed flask equipped with a magnetic stir bar and a reflux condenser was charged with ethyl 4-hydroxy-l-methyl-7-phenoxyisoquinoline-3 -carboxylate (compound II, 5.12 g, 0.0155 mol, 1.0 equiv.), l,8-Diazabicyclo(5.4.0)undec-7-ene (DBU, 4.63 mL, 0.031 mol, 2.0 equiv.) and THF (50 mL); water (0.28 mL). The resulting mixture was heated to 80 °C and stirred for 16 hours. Once the reaction was completed, the temperature was allowed to return to ambient levels, and water (70 mL) was introduced into the mixture which was extracted with toluene (3 x 50 mL). The combined organic phases were washed with water (50 mL) and brine (50 mL). The obtained organic phase was dried over Na2SO4. Purification of the crude product by flash column chromatography on silica gel (n-hexane / EtOAc, from 1: 1 to 0: 1) gave 4.37 g (yield; 63%) of the title compound (Compound IV) as a white-off solid.

[0104] ’H NMR (400 MHz, CDC13): 6 = 13.15 (s, 1 H), 8.67 (t, J = 6.5 Hz, 1 H), 8.33 (dd, J = 9.0, 0.6 Hz, 1 H), 7.46 - 7.36 (m, 4 H), 7.22 - 7.16 (m, 1 H), 7.12 - 7.06 (m, 2 H), 3.56 - 3.43 (m, 4 H), 3.40 - 3.32 (m, 2 H), 2.70 (s, 3 H), 2.61 - 2.52 (m, 2 H), 1.83 (quint, J = 6.5 Hz, 2 H), 1.75- 1.64 (m, 6 H).13C NMR (100 MHz, CDC13) 6 = 176.6 (C), 170.2 (C), 158.2 (C), 156.2 (C), 153.5 (C), 146.8 (C), 132.0 (C), 130.2 (CH), 125.6 (CH), 124.5 (C), 124.4 (CH), 122.2 (CH), 120.24 (C), 119.7 (CH), 111.9 (CH), 49.8 (CH2), 45.8 (CH2), 37.4 (CH2), 36.0 (CH2), 30.1 (CH2), 28.8 (CH2), 28.2 (CH2), 23.6 (CH2), 22.1 (CH3).

[0105] Example 2: The synthesis procedure of Roxadustat in Org. Process Res. Dev. 2022, 26, 915-924 as comparison Example

[0106] This example was performed by following the synthesis procedure of Roxadustat in Org. Process Res. Dev. 2022, 26, 915-924 using HPLC grade ACN (KF: 0.02%). A I L two-necked, round bottomed flask equipped with a magnetic stir bar and a reflux condenser was charged with ethyl 4-hydroxy-l-methyl-7-phenoxyisoquinoline-3-carboxylate (compound II, 50.12 g, 0.155 mol, 1.0 equiv.), glycine (13.96 g, 0.186 mol, 1.2 equiv. l,8-diazabicyclo(5.4.0)undec-7-ene (49.13 mL, 0.33 mol, 2.13 equiv) and ACN (500 mL) under positive pressure of N2. The suspended reaction mixture was stirred at 62 °C under N2atmosphere.

[0107] The reaction conversion was followed by HPLC (Compound II: 0.16%; purity of Roxadustat: 93.03%;

[0108] DBU hydrolysis impurity Compound IV: 6.15% at 7 h).

[0109] The mixture is allowed to down to ambient temperature and water (750 mL) was added. pH of the mixture was adjusted to 3 with 6 M HC1 and stirred vigorously for 3h at ambient temperature. After stirring additionally 1 h under ice cooling, the precipitate was filtered and washed with water (2 x 50 mL) and EtOH (3x50 mL).

[0110] The resulting off-white solid underwent vacuum drying at 80 °C for 10 hours, Roxadustat (50.5 g, 91.5%).

[0111] HPLC purity: 95.91;

[0112] DBU hydrolysis impurity Compound IV: 3.02%.

[0113] Example 3: The synthesis procedure of Roxadustat involving use of Triton B

[0114] A I L two-necked, round bottomed flask equipped with a magnetic stir bar and a reflux condenser was charged with ethyl 4-hydroxy-l-methyl-7-phenoxyisoquinoline-3-carboxylate (Compound II, 50.12 g, 0.155 mol, 1.0 equiv.), glycine (13.96 g, 0.186 mol, 1.2 equiv.), benzyltrimethylammonium hydroxide (Triton B, 40% in MeOH; 97.21 mL, 0.233 mol, 1.5equiv.) and DMF (250 mL) under positive pressure of N2. The suspended reaction mixture was stirred at 75 °C under N2 atmosphere. The reaction conversion was followed by HPLC (Compound II: 0.08%; purity of Roxadustat: 99.06%; at 4h). The mixture is allowed to down to ambient temperature and water (375 mL) was added. pH of the mixture was adjusted to 3 with 6 M HC1 and stirred vigorously for 3 h at ambient temperature. After stirring additionally 1 h under ice cooling, the precipitate was filtered and washed with water (2 x 50 mL) and EtOH (3 x 50 mL).

[0115] The resulting off-white solid underwent vacuum drying at 80 °C for 10 hours, Roxadustat (51.66 g, 94.6%).

[0116] HPLC purity: 99.68%.

[0117] 1H NMR (400 MHz, DMSO-6) δ (ppm) = 8.89 (t, J = 5.3 Hz, 1 H), 8.28 (dd, J = 9.0, 0.5 Hz, 1 H), 7.60 (dd, J = 2.4, 0.5 Hz, 1 H), 7.54 - 7.44 (m, 3 H), 7.28 - 7.22 (m, 1 H), 7.20 - 7.15 (m, 2 H), 3.86 (d, J = 5.4 Hz, 2 H), 2.69 (s, 3 H).13C NMR (100 MHz, DMSO-6) δ (ppm) = 171.1 (C), 169.7 (C), 158.2 (C), 156.2 (C), 153.3 (C), 147.2 (C), 131.9 (C), 130.9 (CH), 125.8 (CH), 125.0 (CH), 124.2 (C), 122.9 (CH), 120.3 (C), 120.0 (CH), 112.7 (CH), 42.6 (CH2), 22.03 (CH3).

Claims

CLAIMS1. A process for the improved preparation of Roxadustat (Compound I) including the following steps:a) providing a mixture by addition of solvent, ethyl 4 -hydroxy- l-methyl-7- phenoxyisoquinoline-3-carboxylate (Compound II) and glycine,b) adding the base to the mixture,OH O OH ORoxadustat Compound IIc) then stirring the mixture at a suitable temperature for a suitable time,d) cooling the mixture at a suitable temperature,e) adding a suitable solvent into the mixture,f) adjusting pH to the appropriate range with HC1 (aq.) and stirring the mixture at a suitable temperature for a suitable time,g) filtering the crystals, washing with a suitable solvent, andh) drying the crystals under a vacuum at the specified temperature.

2. The process according to claim 1, wherein the base used in the reaction step (b) is selected from; benzyltrimethylammonium hydroxide (Triton B), benzyltriethylammonium hydroxide, tetrametylammonium hydroxide (TMAH), tetraetylammonium hydroxide (TEAH), tetrabutylammonium hydroxide (TBAH), tetrapropylammonium hydroxide (TP AH).

3. The process according to claim 1, wherein the solvent used in the reaction step (a) is selected from; water, 2-propanol, 1 -propanol, 1 -butanol, 2-butanol, tert-butyl alcohol, 1 -pentanol, 2-pentanol, amyl alcohol, ethylene glycol, glycerol, acetone, butanone, 2- pentanone, 3-pentanone, methyl butyl ketone, methyl isobutyl ketone, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, tert-butyl acetate, isobutyl acetate, toluene, xylene, chloroform, dichloromethane, carbon tetrachloride, ethylene dichloride, chlorobenzene, acetonitrile, diethyl ether, diisopropyl ether, tert-butyl methyl ether, dibutyl ether, tetrahydrofuran (THF), 1,4-dioxane, 2-methoxyethanol, A / . A-di methyl formamide (DMF), A. A-dimcthylacctamidc (DMAc), N-methylpyrrolidone (NMP), pyridine, dimethyl sulfoxide (DMSO), sulfolane, formamide, acetamide, propanamide, pyridine or mixtures thereof.

4. The process according to claim 1, wherein the suitable temperature used in step (c) is selected from room temperature to reflux temperature of the solvent used.

5. The process according to claim 1, wherein the suitable time used in stirring the mixture in step (c) is between 1 - 16 hours.

6. The process according to claim 1, wherein the suitable temperature used in step (d) is selected from room temperature to -20 °C.

7. The process according to claim 1, wherein the suitable solvent in step (e) is selected from, water, 2-propanol, 1 -propanol, 1 -butanol, 2-butanol, tert-butyl alcohol, 1- pentanol, 2-pentanol, amyl alcohol, ethylene glycol, glycerol, acetone, butanone, 2- pentanone, 3 -pentanone, methyl butyl ketone, methyl isobutyl ketone, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, tert-butyl acetate, isobutyl acetate, toluene, xylene, chloroform, dichloromethane, carbon tetrachloride, ethylene dichloride, chlorobenzene, acetonitrile, diethyl ether, diisopropyl ether, tert-butyl methyl ether, dibutyl ether.

8. The process according to claim 1, wherein the suitable temperature to dry the product in step (g) is from 50 °C to 90 °C.

9. The process according to claim 1, wherein the suitable time used to dry the product in step (g) between 1 - 16 hours.

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