Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D413/00—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and oxygen atoms as the only ring hetero atoms
  • C07D413/02—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and oxygen atoms as the only ring hetero atoms containing two hetero rings
  • C07D413/10—Heterocyclic compounds containing two or more hetero rings, at least one ring having nitrogen and oxygen atoms as the only ring hetero atoms containing two hetero rings linked by a carbon chain containing aromatic rings
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P43/00—Drugs for specific purposes, not provided for in groups A61P1/00-A61P41/00
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P9/00—Drugs for disorders of the cardiovascular system
  • A61P9/12—Antihypertensives

Definitions

• This invention relates to a process for preparing l-[[2'-(2,5-dihydro-5-oxo-l,2 J 4-oxadiazol-3- yl)[l f -biphenyl]-4-yl]methyl]-2-ethoxy-lH-benzimidazole-7-carboxylic acid (azilsartan) of formula (I)
• the invention also relates to preparation of new solid forms of intermediates that make it possible to obtain azilsartan with a high purity over 99.7 % (HPLC) and to their characterization.
• Azilsartan (I) which is a highly selective blocker of angiotensin II ATI receptors, was developed by Takeda and is used for the treatment of high blood pressure. Its synthesis is described in EP 0 520423 (Scheme 1)
• the application WO2012107814 discusses a process for preparing azilsartan using various cyclizing agents in the presence of a base.
• the application WO2012157980 describes cyclization with the use of carbonyl imidazole.
• a process for preparing azilsartan, comprising a cyclizing reaction without the presence of a solvent, is described in WO2014049512.
• the invention relates to preparation of very pure azilsartan.
• the process is based on the use and preparation of new solid forms of the key intermediates that have a principal influence on the purity of the final product - azilsartan.
• they are hemisolvates (2:1) of the ethyl ester (III) with 2-methyltetrahydrofuran (Ilia) or with methyl isobutyl ketone.
• MIBK Methyl isobutyl ketone
• Solvates can also be produced in mixtures of solvents containing 2-methyltetrahydrofuran or methyl isobutyl ketone.
• Solvents in which the above mentioned crystalline solvates can develop include primary or secondary alcohols and ketones. The use of ethanol, methanol, isopropanol or acetone and methyl ethyl ketone is especially convenient.
• azilsartan ethyl ester (III) is transformed to azilsartan (I) by means of alkaline hydrolysis, which may be carried out with the use of sodium or potassium hydroxide in water or suitable solvents of the alcohol type at a temperature from 25 °C to 80°C.
• alkaline hydrolysis does not virtually change the chemical purity of the intermediate, azilsartan can be, after acidification, obtained in an excellent purity of about 99.8%.
• Hydrochloric or acetic acid can be used for the acidification.
• Table 2 XRPD - diffraction peaks corresponding to the solvate of azilsartan ethyl ester with 2-methyltetrahydrofuran (Ilia)
• the solvate of azilsartan ethyl ester with 2-methyltetrahydrofuran exhibits the following main characteristic peaks in X-ray powder diffraction, measured with the use of CuKa radiation: 8.9; 10.5; 12.0; 16.8; 19.6 and 23.5 ⁇ 0.2° 2-theta.
• the prepared solvate is further characterized with the use of DSC (Fig. 2).
• Table 3 XRPD - characteristic diffraction peaks corresponding to the hemisolvate of azilsartan ethyl ester with methyl isobutyl ketone (Illb)
• the solvate of azilsartan ethyl ester with methyl isobutyl ketyone exhibits the following main characteristic peaks in X-ray powder diffraction, measured with the use of CuK ⁇ radiation: 8.6; 11.7; 16.6; 19.2; 21.4 and 25.5 ⁇ 0.2° 2-theta.
• Fig. 1 XRPD pattern for the solvate of azilsartan ethyl ester with 2-methyltetrahydrofuran (Ilia)
• Fig. 2 DSC curve for the solvate of azilsartan ethyl ester with 2-methyltetrahydrofuran (Ilia)
• Fig. 3 TGA curve for the solvate of azilsartan ethyl ester with 2-methyltetrahydrofuran (Ilia)
• Fig. 4 XRPD pattern for the solvate of azilsartan ethyl ester with methyl isobutyl ketone (Illb)
• Fig. 5 DSC curve for the solvate of azilsartan ethyl ester with methyl isobutyl ketone (Mb)
• Fig. 6 TGA curve for the solvate of azilsartan ethyl ester with methyl isobutyl ketone (Illb)
• the samples in the examples below were characterized by the X-ray Powder Diffraction (XRPD), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) methods.
• XRPD X-ray Powder Diffraction
• DSC Differential Scanning Calorimetry
• TGA Thermogravimetric Analysis
• a flat powder sample was used that was placed on a Si plate.
• 0.02 rad Soller slits and a 1 ⁇ 4 anti-diffusion slit were used.
• For the setting of the secondary optical equipment an X'Celerator detector with maximum opening of the detection slot, 0.02 rad Soller slits and a 5.0 mm anti- diffusion slit were used.
• DSC Differential scanning calorimetry
• the temperature program that was used consists of 1 minute's stabilization at the temperature of 22°C and then of heating up to 250(300)°C at the heating rate of 10°C/min. 4.0 N 2 at the flow of 20 ml/min was used as the carrier gas.
• the ethoxy oxime (II) (150 g; 327 mmol) is suspended in 1370 ml of diethyl carbonate. The suspension is heated up to 65 °C. A solution of sodium ethoxide in ethanol (21 %, 154 ml, 412 mmol) is added dropwise to the reaction mixture at 65°C during 30 minutes. After completion of the addition the reaction mixture is agitated at 65 °C for 30 minutes. The reaction mixture is cooled down to 60 °C and water (520 ml) is added. The resulting emulsion is agitated for at least 15 minutes. After separation of the layers the organic phase is extracted with water (520 ml).
• the combined aqueous extracts are diluted with ethanol (600 ml) and methyl isobutyl ketone (100 ml). The temperature of the solution is adjusted to 40°C. Acetic acid (43 ml, 750 mmol) is added to the solution dropwise at 40°C during 30 minutes. The resulting suspension is agitated at 40°C for 30 minutes and then cooled down to 20°C. The separated substance is aspirated and washed with water (2 x 150 ml). The final product is dried in a vacuum drier at 45°C. 154 g (88% of the theoretical quantity, HPLC 99.5%) of azilsartan ethyl ester hemisolvate with methyl isobutyl ketone (Illb) was obtained.
• Example 3 Example 3:
• a solution of sodium ethoxide in ethanol (21 %, 77 ml, 206 mmol) is added dropwise to the reaction mixture at 65°C during 30 minutes. After completion of the addition the reaction mixture is agitated at 65°C for 30 minutes. The reaction mixture is cooled down to 60 °C and water (260 ml) is added. The resulting emulsion is agitated for at least 15 minutes. After separation of the layers the organic phase is extracted with water (260 ml). The combined aqueous extracts are diluted with ethanol (260 ml) and 2-methyltetrahydrofuran (150 ml). The temperature of the solution is adjusted to 40°C.
• Acetic acid (21 ml, 370 mmol) is added to the solution dropwise at 40°C during 30 minutes.
• the resulting suspension is agitated at 40°C for 30 minutes and then cooled down to 20°C.
• the separated substance is aspirated and washed with water (2 x 75 ml).
• the final product is dried in a vacuum drier at 45°C. 72.5 g (84% of the theoretical quantity, HPLC 99.4%) of azilsartan ethyl ester hemisolvate 2-methyltetrahydrofuran (Ilia) was obtained.
• Azilsartan ethyl ester (III) (380 g; 784 mmol) is suspended in 2600 ml of 2-methyltetrafuran. The suspension is heated up to reflux. 1200 ml of distillate is removed from the reaction mixture by distillation. The resulting suspension is cooled down to 45 °C. The reaction mixture is agitated at 45°C for 30 minutes and then cooled down to 20°C. The separated substance is aspirated and washed with cooled 2-memyltelrafuran (75 ml). The final product is dried in a vacuum drier at 45°C. 372 g (90% of the theoretical quantity, HPLC 99.7%) of azilsartan ethyl ester hemisolvate 2-methyltetrahydrofuran (Ilia) was obtained.
• Example 5 Example 5:
• ethoxy- lH-benzimidazole-7-carboxy lie acid (I).
• Ethoxy azilsartan hemisolvate with 2-methyltetrafuran (Ilia) (160 g) was weighed into a 5 liter pot and suspended in a NaOH/water solution (38g/500 ml). The reaction mixture is heated up to 50°C and agitated for 4 hours. The reaction mixture is diluted with acetone (250 ml), acetic acid (101 g) is added and the mixture is left to crystallize at 50°C for lh. After cooling to 20°C and agitation for half an hour the product is aspirated and washed with water (2 x 110 ml). The final product is then dried in a vacuum drier at 45°C. 129 g (93% of the theoretical quantity, HPLC 99.8%) of azilsartan (I) was obtained.
• Ethoxy azilsartan hemisolvate with methyl isobutyl ketone (Illb) 100 g was weighed into a 5 liter pot and suspended in a NaOH/water solution (23g 315 ml). It was heated up to 50°C and agitated for 4 hours. The reaction mixture is diluted with acetone (160 ml), acetic acid (63 g) is added and the mixture is left to crystallize at 50°C for 1 hour. Then, the suspension is cooled down to 20°C and, after half an hour, aspirated and washed with water (2 x 70 ml). The resulting product is dried in a vacuum drier at 45°C. 82 g (95% of the theoretical quantity, HPLC 99.7%) of azilsartan (I) was obtained.

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