DESC:“IMPROVED PROCESSES FOR THE PREPARATION OF ROXADUSTAT”

FIELD OF THE INVENTION
The present invention relates to an improved process for the preparation of Roxadustat and also provided a process for preparation of pure crystalline Form A of Roxadustat.

BACKGROUND OF THE INVENTION
Roxadustat (I) or FG-4592, chemical entitled [[(4-hydroxy-1-methyl-7-phenoxy isoquinolin-3-yl) carbonyl] amino]] acetic acid. Roxadustat (FG-4592) is an oral small molecule inhibitor of Hypoxia-Inducible Factor-prolyl hydroxylases, or HIF-PHs, in Phase 3 clinical development for treating and preventing disorders associated with HIF, including anemia in chronic kidney disease or CKD, ischemia, and hypoxia. Its structural formula is as follows:

Roxadustat was approved by European Medicine Agency (EMA) on Aug 18, 2021. It was developed by Fibrogen Inc, then marketed as Evrenzo® by Astellas Pharma in EU.

Roxadustat is reported in US 7323475 of Fibrogen Inc. The synthetic process for Roxadustat is reported in US ‘475, which comprises compound of formula (1) is treated with phosphoryl bromide (POBr3) in presence of acetonitrile (ACN)/ sodium bicarbonate (NaHCO3)/water to obtain formula (2). The compound of formula (2) is treated with sodium hydroxide (NaOH) in presence of ethanol (EtOH) & acidified with hydrochloric acid (HCl) to obtain formula (3). The compound of formula (3) is treated with n-butyllithium (n-BuLi) in hexane in presence of tetrahydrofuran (THF) & benzyl bromide/potassium carbonate (K2CO3) to obtain compound of formula (4). The compound of formula (4) is treated with potassium hydroxide (KOH) in presence of EtOH to obtain compound of formula (5). The compound of formula (5) is treated with triethylamine (Et3N) in presence of dichloromethane (CH2Cl2) & isobutylchloro formate (ClCO2iBu)/ glycine benzyl ester hydrochloride (glycine benzyl ester HCl) to obtain compound of formula (6). The compound of formula (6) is treated with Pd/C, H2 in presence of ethyl acetate (EtOAc) to obtain Roxadustat (I).
The above process is schematically shown as below:

Scheme-I
US 8883823 of Fibrogen Inc reported process for the preparation of Roxadustat (I), which comprises the compound of formula (V) is treated with Bis-dimethylaminomethane (VI) in presence of acetic acid to obtain the compound of formula (VII). The compound of formula (VII) is treated with acetic anhydride in presence of morpholine to obtain the compound of formula (VIII). The compound of formula (VIII) is reduced with H2, Pd/C, sodium carbonate (Na2CO3) in presence of ethyl acetate (EtOAc) to obtain the compound of formula (IX). The compound of formula (IX) is treated with glycine in methanol/ sodium methoxide (NaOCH3) in presence of acetic acid to obtain Roxadustat (I).
The above process is schematically shown as below:

Scheme-II
The above processes disclose the preparation of the Roxadustat (I) is difficult for bulk manufacturing process commercially. There are many steps, the raw materials are expensive, and the production cost is high. Impurities are generated in the preparation process of the Roxadustat (I), and the impurities affect the purity of the Roxadustat (I).

Therefore, it is necessary to design a safer and more environmentally-friendly synthetic route. So, our inventors have developed an improved process for the preparation of Roxadustat (I) with a low-cost, environmentally-friendly, and efficient synthesis method with high purity and good yield.

OBJECT OF THE INVENTION
One objective of the present invention relates to an improved process for the preparation of Roxadustat.

The second objective of the present invention provided a process for preparation of pure crystalline Form A of Roxadustat.

SUMMARY OF THE INVENTION

The present invention relates to an improved process for the preparation of Roxadustat and also provided a process for preparation of pure crystalline Form A of Roxadustat.

One embodiment of the present invention provides an improved for the preparation of Roxadustat (I), comprising the steps of:
a) reacting compound of formula (IV) with methylating agent in presence of catalyst, solvent and base to obtain the compound of formula (III),

b) optionally isolating compound of formula (III) with solvent,
c) reacting compound of formula (III) with glycine methylester hydrochloride (glycine methylester. HCl) in presence of coupling reagent, solvent and base to obtain the compound of formula (II),

d) optionally isolating compound of formula (II) with solvent,
e) hydrolyzing the compound of formula (II) with base in presence of solvent to obtain the Roxadustat (I), and

f) optionally purifying Roxadustat by treating with base and acid.

In yet another embodiment of the invention provides a process for preparation of pure crystalline Form A of Roxadustat having purity of greater than 99 %, comprising the steps of:
a. Crude Roxadustat is leached in solvent or mixture of solvents,
b. heating the reaction mixture at suitable temperature,
c. cooling the reaction mixture,
d. filter the Roxadustat,
e. adding solvent to the obtained step d),
f. adding aqueous base to the solution of step e),
g. heating the reaction mixture at suitable temperature,
h. cooling the reaction mixture,
i. acidifying with acid to the solution of step h), and
j. isolating the pure crystalline Form A of Roxadustat.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an improved process for the preparation of Roxadustat and also provided a process for preparation of pure crystalline Form A of Roxadustat.

One embodiment of the present invention provides an improved for the preparation of Roxadustat (I), comprising the steps of:
a) reacting compound of formula (IV) with methylating agent in presence of catalyst, solvent and base to obtain the compound of formula (III),

b) optionally isolating compound of formula (III) with solvent,
c) reacting compound of formula (III) with glycine methylester hydrochloride (glycine methylester. HCl) in presence of coupling reagent, solvent and base to obtain the compound of formula (II),

d) optionally isolating compound of formula (II) with solvent,
e) hydrolyzing the compound of formula (II) with base in presence of solvent to obtain the Roxadustat (I), and

f) optionally purifying Roxadustat by treating with base and acid.

According to an embodiment of the present invention, reacting compound of formula (IV) with methylating agent in presence of catalyst, solvent and base, the reaction is carried out at 90 to 110°C for 2-6 hours, followed by adjust pH 6-7 with dilute HCl to obtain the compound of formula (III). Optionally isolating compound of formula (III) with solvent.

According to an embodiment of the present invention, reacting compound of formula (III) with glycine methylester. HCl in presence of coupling reagent, solvent and base, the reaction is carried out at 20 to 35°C for 2-6 hours to obtain the compound of formula (II). Optionally isolating compound of formula (II) with solvent.

According to an embodiment of the present invention, hydrolyzing the compound of formula (II) with base in presence of solvent and the reaction is carried out at 35 to 50°C for 2-6 hours to obtain the Roxadustat (I). Optionally purifying Roxadustat by treated with base and acid.

According to an embodiment of the present invention, wherein the methylating agent selected from trimethylboron, tetramethyltin, methylboronic acid or isopropyl methylboronic acid.

According to an embodiment of the present invention, wherein the catalyst is selected from palladium-based catalyst; the palladium-based catalyst is selected from bis(triphenylphosphine) palladium chloride, palladium acetate, triphenylphosphine palladium acetate, tetrakis(triphenylphosphine) palladium, and palladium acetylacetonate, bis(benzonitrile)palladium dichloride, tris (benzylideneacetone) dipalladium, (1,3-bis(diphenylphosphine)propane)palladium chloride, (1,1'-bis(diphenylphosphino)ferrocene)palladium(II) dichloride and [1,1'-bis(diphenylphosphino) ferrocene] palladium dichloride dichloromethane complex.

According to an embodiment of the present invention, wherein the base selected from inorganic base or organic base; inorganic base is selected from alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide; alkali metal carbonates such as sodium carbonate, potassium carbonate, cesium carbonate and lithium carbonate; alkali metal bicarbonates such as sodium bicarbonate and potassium bicarbonate; alkali metal alkoxides such as sodium methoxide, potassium methoxide, sodium tertiary butoxide, potassium tertiary butoxide; alkali metal hydrides such as sodium hydride, potassium hydride, lithium hydride; ammonia; sodium sulphite; tri sodium phosphate (Na3PO4) or tri potassium phosphate (K3PO4); organic base is selected from triethylamine, triethanolamine, diisopropylethylamine, di-n-propylamine and 4-dimethylaminopyridine.

According to an embodiment of the present invention, wherein the coupling reagent is selected from N-hydroxybenzotriazole (HOBT), 1-hydroxy-7-azabenzotriazole (HOAT), (benzotriazol-1-yloxy) tripyrrolidinophosphonium hexafluorophosphate (PyBOP), benzotriazol-1-yloxytris(dimethylamino) phosphonium hexafluorophosphate (BOP), 1,1-carbonyldiimidazole (CDI), ?,?'-diisopropylcarbodiimide (DIC), 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC.HCl), N,N-dicyclohexylcarbodiimide (DCC), l-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium-3-oxide hexafluorophosphate (HATU), 2-(1H-benzotriazol-l-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HBTU) and the like.

According to an embodiment of the present invention, wherein the acid selected used in the present invention can be selected from but not limited to "inorganic acids" such as hydrofluoric acid, hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, perchloric acid, carbonic acid; and "organic acids" such as formic acid, acetic acid, trifluoroacetic acid, propionic acid, butyric acid, valeric acid, capric acid, oxalic acid, malonic acid, maleic acid, fumaric acid, lactic acid, succinic acid, citric acid, uric acid, tartaric acid, benzoic acid, 4-hydroxybenzoic acid, salicylic acid, oleic acid, octanoic acid, stearic acid, mandelic acid, adepic acid, pivalic acid, camphorsulfonic acid, substituted/unsubstituted alkyl/aryl sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, naphthalenesulfonic acid and or mixtures thereof.

According to an embodiment of the present invention. wherein the solvent is selected from tetrahydrofuran, toluene, water, acetone, acetonitrile, ethyl acetate, isopropyl alcohol, methanol, ethanol, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), isopropyl acetate and n-butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, n-hexane, diethyl ether, diisopropyl ether, dioxane, 1,2-dimethoxyethane, dichloromethane (MDC), dichloroethane, carbon tetrachloride and chloroform, methyl tert-butyl ether (MTBE), N-methyl-2-pyrrolidone (NMP), 2-methoxy ethanol, dimethoxyethane, glycol diethyl ether, ethylene glycol ethyl ether or ethylene glycol, and/or mixtures thereof.

In yet another embodiment of the invention provides a process for preparation of pure crystalline Form A of Roxadustat having purity of greater than 99 %, comprising the steps of:
a. Crude Roxadustat is leached in solvent or mixture of solvents,
b. heating the reaction mixture at suitable temperature,
c. cooling the reaction mixture,
d. filter the Roxadustat,
e. adding solvent to the obtained step d),
f. adding aqueous base to the solution of step e),
g. heating the reaction mixture at suitable temperature,
h. cooling the reaction mixture,
i. acidifying with acid to the solution of step h), and
j. isolating the pure crystalline Form A of Roxadustat.

According to an embodiment of the present invention, Roxadustat is leached in solvent or mixture of solvents, the reaction is carried out at 30 to 50°C and then cooled to 5-20°C, filtered to obtain Roxadustat. Roxadustat is dissolved in solvent, followed by adding with base and the reaction is carried out at 30 to 50°C for 1-4 hours and then cooled to 25-30°C and followed by acidifying with acid to obtain the crystalline Form A of Roxadustat.

According to an embodiment of the present invention, wherein the base selected from inorganic base or organic base; inorganic base is selected from alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide; alkali metal carbonates such as sodium carbonate, potassium carbonate, cesium carbonate and lithium carbonate; alkali metal bicarbonates such as sodium bicarbonate and potassium bicarbonate; alkali metal alkoxides such as sodium methoxide, potassium methoxide, sodium tertiary butoxide, potassium tertiary butoxide; alkali metal hydrides such as sodium hydride, potassium hydride, lithium hydride; ammonia; sodium sulphite; tri sodium phosphate (Na3PO4) or tri potassium phosphate (K3PO4); organic base is selected from triethylamine, triethanolamine, diisopropylethylamine, di-n-propylamine and 4-dimethylaminopyridine.

According to an embodiment of the present invention, wherein the acid selected used in the present invention can be selected from but not limited to "inorganic acids" such as hydrofluoric acid, hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, perchloric acid, carbonic acid; and "organic acids" such as formic acid, acetic acid, trifluoroacetic acid, propionic acid, butyric acid, valeric acid, capric acid, oxalic acid, malonic acid, maleic acid, fumaric acid, lactic acid, succinic acid, citric acid, uric acid, tartaric acid, benzoic acid, 4-hydroxybenzoic acid, salicylic acid, oleic acid, octanoic acid, stearic acid, mandelic acid, adepic acid, pivalic acid, camphorsulfonic acid, substituted/unsubstituted alkyl/aryl sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, naphthalenesulfonic acid and or mixtures thereof.

According to an embodiment of the present invention. wherein the solvent is selected from tetrahydrofuran, toluene, water, acetone, acetonitrile, ethyl acetate, isopropyl alcohol, methanol, ethanol, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), isopropyl acetate and n-butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, n-hexane, diethyl ether, diisopropyl ether, dioxane, 1,2-dimethoxyethane, dichloromethane (MDC), dichloroethane, carbon tetrachloride and chloroform, methyl tert-butyl ether (MTBE), N-methyl-2-pyrrolidone (NMP), 2-methoxy ethanol, dimethoxyethane, glycol diethyl ether, ethylene glycol ethyl ether or ethylene glycol, and/or mixtures thereof.

According to the embodiment of the present invention, the present invention provides an efficient process for the purification of Roxadustat substantially free from impurities such as Methyl ester impurity (i), Dimer impurity (ii), Des methyl impurity (iii) and Bromo impurity (iv).

According to the embodiment of the present invention, substantially free we mean that the process produces impurities such as a compound of formula (i) equal to or lower than 0.15% and/or an amount of a compound of formula (ii) equal to or lower than 0.15% and/or an amount of a compound of formula (iii) equal to or lower than about 0.15% and/or an amount of a compound of formula (iv) equal to or lower than about 0.15%.

According to an embodiment of the present invention provides Roxadustat 90% of the drug particles have a particle size less than 250 microns.

According to an embodiment of the present invention, wherein Roxadustat is isolating as a pure crystalline Form A. crystalline Form A of Roxadustat having HPLC purity = 99.5%.

The following examples illustrate the present invention, but should not be construed as limiting the scope of the invention.

EXAMPLES
Example-1:
Preparation of 4-hydroxy-1-methyl-7-phenoxyisoquinoline-3-carboxylic acid (III).
Butyl 1-bromo-4-hydroxy-7-phenoxyisoquinoline-3-carboxylate (IV) (100 g, 0.2402 mol), 2-methoxy ethanol (800 ml), tri potassium phosphate (178.5g, 0.8408 mol), methyl boronic acid (50.32g, 0.8407 mol) and tetrakis(triphenylphosphine) palladium (3.5g) were added in to RB flask. The obtained reaction mixture was allowing to rise at 95-105°C and stir for 3-4 hrs. After completion of the reaction, the reaction mixture was cooled to 25-30°C and reaction mixture filtered and then take filtrate into RB flask & distilled off 2-methoxy ethanol under vacuum at below 80°C. The obtained product allowed to cool at 25-30°C, charge purified water (1000 ml) and adjusted filtrate pH:6-7 with 1:1 dilute hydrochloric acid. The obtained product was filtered to obtain Crude 4-hydroxy-1-methyl-7-phenoxyisoquinoline-3-carboxylic acid.
Crude 4-hydroxy-1-methyl-7-phenoxyisoquinoline-3-carboxylic acid and methanol (500 ml) into RB flask. The reaction mixture temperature was raised to reflux (60-65°C) for 20-30 min and then allowed to cool at RT. The obtained solid was filtered to get pure 4-hydroxy-1-methyl-7-phenoxyisoquinoline-3-carboxylic acid (III).

Yield: 84.58% (60 g)
Purity: ~ 97% by HPLC

Example-2:
Preparation of methyl 2-(4-hydroxy-1-methyl-7-phenoxyisoquinoline-3-carboxamido) acetate (II).
4-Hydroxy-1-methyl-7-phenoxyisoquinoline-3-carboxylic acid (III) (100 g, 0.3386 mol) and DMF (400 mL) into RB flask. The reaction mixture was cooled to 0-5°C and then charge (Benzotriazol-1-yloxy) tripyrrolidinophosphonium hexafluorophosphate (PyBOP) (246.7g, 0.474 mol), glycine methyl ester. HCl (55.26 g, 0.4401 mol) were in to RB flask, followed by slowly add triethylamine (102.78g,1.015 mol). The reaction mixture temperature was raised to 25-30°C & stir for 3-4 hrs. After completion of the reaction, slowly charge purified water (1200 ml) at below 30°C and filtered to obtain crude methyl 2-(4-hydroxy-1-methyl-7-phenoxyisoquinoline-3-carboxamido) acetate.
Crude methyl 2-(4-hydroxy-1-methyl-7-phenoxyisoquinoline-3-carboxamido) acetate and toluene (200ml) into RB flask. The reaction mixture temperature was heated to 70-75°C for 20-30 min and then allowed to cool at 10-15°C & filter to obtained pure methyl 2-(4-hydroxy-1-methyl-7-phenoxyisoquinoline-3-carboxamido) acetate (II).

Yield: 80.47% (100 g)
Purity: 99% by HPLC

Example-3:
Preparation of Roxadustat (I).
Methyl 2-(4-hydroxy-1-methyl-7-phenoxyisoquinoline-3-carboxamido) acetate (II) (100 g, 0.2729 mol), methanol (300 mL), water (500 ml) and sodium hydroxide (25.10g, 0.6277 mol) were added in to RB flask. The obtained reaction mixture temperature was to allowed at 40-45°C and stir for 3-4 hrs. After completion of the reaction, the reaction mixture was cooled to 25-30°C and then adjusted pH:4-5 with 1:2 dilute HCl. The obtain product was filtered and then washed with acetone to obtained crude Roxadustat (I).

Example-4:
Purification of Roxadustat.

Crude Roxadustat leached in 30% methanol (240 ml) and dichloromethane (560 ml) into RB flask. The reaction mixture was heated at 40-45°C for 30-45 min and then it was allowed to cool at 10-15° and filtered to obtain Roxadustat.
Above wet material Roxadustat and charge purified water (800 ml) into RB flask, followed by adjust pH:9.5-10.5 with 50% NaOH solution (w/v) at below 30°C. Observed clear solution in reaction mass. The reaction mass temperature was heated at 40-45°C and stir for 1-2 hrs at 40-45°C. The obtained reaction mas was filtered through high flown bed and bed wash with purified water (200 ml) at 40-45°C. The obtained total filtrate into RB flask and it was allowed to cool at below 30°C. The obtained reaction mas was adjust pH:4.0-5.0 with 1:2 dil HCl at below 30°C and stir for 1-2 hrs at 25-30°C. The obtain solid was filtered and wash with purified water (100 ml) at 25-30°C to get pure Roxadustat.

Yield: 83.45% (80 g)
Purity: = 99.8% by HPLC
,CLAIMS:We claim:
1. A process for preparation of pure crystalline Form A of Roxadustat having purity of greater than 99 %, comprising the steps of:
a) Crude Roxadustat is leached in solvent or mixture of solvents,
b) heating the reaction mixture at suitable temperature,
c. cooling the reaction mixture,
d. filter the Roxadustat,
e. adding solvent to the obtained step d),
f. adding aqueous base to the solution of step e),
g. heating the reaction mixture at suitable temperature,
h. cooling the reaction mixture,
i. acidifying with acid to the solution of step h), and
j. isolating the pure crystalline Form A of Roxadustat.

2. The process as claimed in claim 1, wherein the base selected from inorganic base or organic base; inorganic base is selected from alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide; alkali metal carbonates such as sodium carbonate, potassium carbonate, cesium carbonate and lithium carbonate; alkali metal bicarbonates such as sodium bicarbonate and potassium bicarbonate; alkali metal alkoxides such as sodium methoxide, potassium methoxide, sodium tertiary butoxide, potassium tertiary butoxide; alkali metal hydrides such as sodium hydride, potassium hydride, lithium hydride; ammonia; sodium sulphite; tri sodium phosphate (Na3PO4) or tri potassium phosphate (K3PO4); organic base is selected from triethylamine, triethanolamine, diisopropylethylamine, di-n-propylamine and 4-dimethylaminopyridine.

3. The process as claimed in claim 1, wherein the acid selected from inorganic acids such as hydrofluoric acid, hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, perchloric acid, carbonic acid; and "organic acids" such as formic acid, acetic acid, trifluoroacetic acid, propionic acid, butyric acid, valeric acid, capric acid, oxalic acid, malonic acid, maleic acid, fumaric acid, lactic acid, succinic acid, citric acid, uric acid, tartaric acid, benzoic acid, 4-hydroxybenzoic acid, salicylic acid, oleic acid, octanoic acid, stearic acid, mandelic acid, adepic acid, pivalic acid, camphorsulfonic acid, substituted/unsubstituted alkyl/aryl sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, naphthalenesulfonic acid and or mixtures thereof.

4. The process as claimed in claim 1, wherein the solvent is selected from tetrahydrofuran, toluene, water, acetone, acetonitrile, ethyl acetate, isopropyl alcohol, methanol, ethanol, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), isopropyl acetate and n-butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, n-hexane, diethyl ether, diisopropyl ether, dioxane, 1,2-dimethoxyethane, dichloromethane (MDC), dichloroethane, carbon tetrachloride and chloroform, methyl tert-butyl ether (MTBE), N-methyl-2-pyrrolidone (NMP), 2-methoxy ethanol, dimethoxyethane, glycol diethyl ether, ethylene glycol ethyl ether or ethylene glycol, and/or mixtures thereof.

5. The process as claimed in claim 1, an efficient process for the purification of Roxadustat substantially free from impurities such as Methyl ester impurity (i), Dimer impurity (ii), Des methyl impurity (iii) and Bromo impurity (iv).

6. The process as claimed in claim 5, wherein the substantially free mean that the process produces impurities such as a compound of formula (i) equal to or lower than 0.15% and/or an amount of a compound of formula (ii) equal to or lower than 0.15% and/or an amount of a compound of formula (iii) equal to or lower than about 0.15% and/or an amount of a compound of formula (iv) equal to or lower than about 0.15%.

7. The process as claimed in claim 1, Roxadustat 90% of the drug particles have a particle size less than 250 microns.

8. The process as claimed in claim 1, wherein Roxadustat is isolating as a pure crystalline Form A. crystalline Form A of Roxadustat having HPLC purity = 99.5%.