Preparation method of ornidazole

Abstract

The invention discloses a preparation method of ornidazole. The method is simple in post-treatment. The content of the compound I contained in the ornidazole prepared by the method is less than 20 ppm, and the medication safety is improved. Wherein the structure of the compound I is as follows: # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the technical field of medicines, and particularly relates to a method for preparing ornidazole. Background Art

[0002] Ornidazole, chemically known as 2-methyl-1-(3-chloro-2-hydroxypropyl)-3-nitro-1H-imidazole, is a third-generation nitroimidazole antibiotic developed after metronidazole and tinidazole, with higher efficacy, shorter course of treatment, better tolerance, and wider distribution in the body. It has good anti-anaerobic and anti-trichomonal effects. Both the original drug and intermediate metabolites of ornidazole are active, acting on the DNA of anaerobic bacteria, amoeba, giardia, and trichomonas cells, breaking their helical structure or blocking their transcription and replication, resulting in death. It is suitable for a variety of diseases caused by anaerobic infection, prevention of infection before surgery, and treatment of anaerobic infection after surgery.

[0003] The inventors have found that in the process of generating ornidazole (compound II) by reacting 2-methyl-5-nitroimidazole (compound IV) and epichlorohydrin (compound III) under the action of Lewis acid, as the concentration of ornidazole in the system increases, the "hydroxyl" of ornidazole is easy to further react with the activated epichlorohydrin to generate compound I, and the reaction is as follows:

[0004]

[0005] Compound I, 1-chloro-3-((1-chloro-3--(2-methyl-5-nitro-1H-imidazol-1-yl)propan-2-yl)oxy)propan-2-ol, was assessed as a warning structure by the genotoxic software.

[0006]

[0007] The ICH-M7 guideline states that impurities with warning structures unrelated to the structure of the API and without mutagenicity data can be controlled to not exceed acceptable limits. The TTC intake calculation for a single impurity is shown in Table 1:

[0008] Table 1: Acceptable intake levels for individual impurities

[0009] Treatment period ≤1 month >1-12 months >1-10 years >10 years to lifetime Total daily intake (μg / day) 120 20 10 1.5

[0010] The conventional daily dose of ornidazole is 1g, which can be used continuously for 1-10 days based on different indications. If the drug is used multiple times throughout life, it needs to be controlled according to the total acceptable daily intake of 20μg / day during the 1-12 month treatment period. Therefore, compound I must be controlled to be less than 20ppm in the ornidazole finished product. Summary of the invention

[0011] In order to achieve the purpose of the present invention, the first aspect of the present invention provides a method for preparing ornidazole, comprising the following steps:

[0012] (1) 2-methyl-5-nitroimidazole reacts with epichlorohydrin in an organic solvent in the presence of an acid. After the reaction is completed, a reaction solution is obtained.

[0013] (2) quenching the reaction solution obtained in step (1) with water, filtering, and directly adjusting the pH value of the filtrate with a weak base without adding an acid to adjust the pH, and then separating the organic phase;

[0014] (3) washing the organic phase in step (2) with water and concentrating it to obtain ornidazole;

[0015] Wherein, in step (1), the organic solvent is immiscible with water.

[0016] Furthermore, the acid in step (1) is selected from one or more of formic acid, acetic acid, sulfuric acid or aluminum chloride, and the molar ratio of 2-methyl-5-nitroimidazole to the acid in step (1) is 1:0.7-10.

[0017] Furthermore, in step (1), when the acid is selected from one or more of formic acid or acetic acid, the molar ratio of 2-methyl-5-nitroimidazole to the acid is 1:3-10.

[0018] Furthermore, in step (1), when the acid is selected from one or more of sulfuric acid or aluminum chloride, the molar ratio of 2-methyl-5-nitroimidazole to the acid is 1:0.7 to 2, preferably 1:1 to 1.2.

[0019] In some typical embodiments, in step (1), the acid is selected from aluminum chloride, and the molar ratio of 2-methyl-5-nitroimidazole to AlCl3 is 1:1.

[0020] Furthermore, in step (1), the molar ratio of 2-methyl-5-nitroimidazole to epichlorohydrin is 1:1 to 1.5, for example 1:1.

[0021] Furthermore, in step (1), the organic solvent is selected from one or more of ethyl acetate, dichloromethane, chloroform or diethyl ether, preferably ethyl acetate.

[0022] Furthermore, the reaction temperature of step (1) is 0-10°C.

[0023] Furthermore, the volume mass ratio of the amount of water used for quenching with water in step (2) to the 2-methyl-5-nitroimidazole in step (1) is 1 to 10:1, for example 3:1, and the quenching temperature is 0 to 10°C, preferably 0 to 5°C.

[0024] Furthermore, the filtration in step (2) is to recover the 2-methyl-5-nitroimidazole that has not participated in the reaction in the reaction system, and the temperature during filtration is controlled at 0-5°C.

[0025] Furthermore, in step (2), the weak base is selected from diethylamine, triethylamine, ammonia water or sodium bicarbonate, preferably ammonia water.

[0026] Furthermore, in step (2), the molar ratio of the weak base to 2-methyl-5-nitroimidazole is 1 to 1.25:1, for example 1.25:1.

[0027] Furthermore, in step (2), the pH is adjusted to 5-6 using a weak base.

[0028] Furthermore, in step (3), the organic phase in step (2) is washed with water 2 to 3 times, and the volume mass ratio of the water used for each washing to the 2-methyl-5-nitroimidazole in step (1) is 0.5 to 20:1, for example 1.5:1.

[0029] Furthermore, in step (3), the organic phase in step (2) is washed twice with water, and the volume mass ratio of the water used for each washing to the 2-methyl-5-nitroimidazole in step (1) is 0.5 to 20:1, for example, 1.5:1.

[0030] As a preferred embodiment, the present invention provides a method for preparing ornidazole, comprising the following steps:

[0031] a) 2-methyl-5-nitroimidazole reacts with epichlorohydrin in ethyl acetate in the presence of AlCl3 at 0-10°C. After the reaction is completed, a reaction solution is obtained.

[0032] b) quenching the reaction solution obtained in step a) with water at 0-5° C. and filtering to obtain a filtrate;

[0033] c) directly adding ammonia water to adjust the pH of the filtrate obtained in step b) to 5-6 without adding acid to adjust the pH, standing and stratifying, and separating the organic phase;

[0034] d) washing the organic phase in step c) with water for 2 to 3 times and concentrating to obtain ornidazole.

[0035] Further, in the step a), the molar ratio of 2-methyl-5-nitroimidazole to AlCl3 is 1:0.7-2, preferably 1:1-1.2. In some typical embodiments, the molar ratio of 2-methyl-5-nitroimidazole to AlCl3 in the step a) is 1:1.

[0036] Furthermore, in step a), the molar ratio of 2-methyl-5-nitroimidazole to epichlorohydrin is 1:1 to 1.5, for example 1:1.

[0037] Furthermore, the volume mass ratio of the amount of water used for quenching with water in step b) to the 2-methyl-5-nitroimidazole in step (1) is 1 to 10:1, for example 3:1, and the quenching temperature is 0 to 10°C, preferably 0 to 5°C.

[0038] Furthermore, the ammonia water in step c) is 25% ammonia water.

[0039] Furthermore, in step c), the molar ratio of aqueous ammonia to 2-methyl-5-nitroimidazole is 1 to 1.25:1, for example 1.25:1. When the amount of aqueous ammonia is 1.35, a large amount of colloidal solids will precipitate from the reaction system, which is not conducive to further post-treatment.

[0040] Furthermore, in the step (d), the organic phase is washed twice with water, and the volume mass ratio of the water used for each washing to the 2-methyl-5-nitroimidazole in the step a) is 0.5 to 20:1, for example 1.5:1.

[0041] The post-treatment of the present invention is simple. It is not necessary to use concentrated hydrochloric acid or other inorganic acids to first adjust the pH of the reaction system to 1 and then use concentrated ammonia water to adjust the pH to 7.0-7.5. Instead, the pH is directly adjusted to 5-6 with ammonia water, thereby avoiding the generation of a large amount of acid wastewater and the formation of colloids. Moreover, the content of compound I in the ornidazole prepared by the method is less than 20ppm, thereby improving the safety of the drug. The structure of the compound I is as follows:

[0042]

[0043] Moreover, in the process of preparing ornidazole of the present invention, the filter cake obtained by filtering after quenching with water in step (2) or step b) is unreacted 2-methyl-5-nitroimidazole, which can be further recycled and reused, thus saving resources.

[0044] Optionally, the ornidazole prepared by the present invention containing less than 20 ppm of compound I can be further purified by conventional methods, such as recrystallization from 40% to 60% (V / V) ethanol aqueous solution, preferably recrystallization from 50% (V / V) ethanol aqueous solution.

[0045] Another aspect of the present invention provides ornidazole prepared by the above method.

[0046] Another aspect of the present invention provides an ornidazole containing less than 20 ppm of compound I, wherein the structure of compound I is as follows:

[0047]

[0048] Another aspect of the present invention provides a pharmaceutical preparation of ornidazole, which contains less than 20 ppm of compound I of ornidazole.

[0049] Another aspect of the present invention provides a use of ornidazole containing less than 20 ppm of compound I in preparing an ornidazole pharmaceutical preparation.

[0050] Another aspect of the present invention provides a use of ornidazole containing less than 20 ppm of compound I for preparing molinidazole.

[0051] Another aspect of the present invention provides a compound I having the following structure:

[0052]

[0053] Another aspect of the present invention provides a method for preparing compound I, comprising the following steps: Compound II or compound IV and compound III generate compound I in the presence of an acid, and the reaction is as follows:

[0054]

[0055] Furthermore, the acid is selected from one or more of formic acid, acetic acid, sulfuric acid or aluminum chloride, preferably aluminum chloride.

[0056] Furthermore, the reaction temperature is 25-40°C.

[0057] Furthermore, the molar ratio of compound III to compound II is 1 to 3:1.

[0058] Furthermore, the molar ratio of compound III to compound IV is 1.5 to 4:1.

[0059] Another aspect of the present invention provides a use of Compound I as a standard or reference substance in the quality study of ornidazole or molinidazole.

[0060] According to the prior art CN1304001C, the compound I provided by the present invention also has a potential use in treating or preventing atopic dermatitis. Another aspect of the present invention provides a use of compound I in preparing an external medicine for treating or preventing atopic dermatitis.

[0061] Another aspect of the present invention provides a method for detecting compound I in ornidazole, using an HPLC-MS-ESI analysis system. Under an electrospray ionization source probe, compound I undergoes solvent volatilization, ion desolvation, and protonation into charged ions. Then, under the action of an electric field, the compound I passes through an ion transmission capillary to reach a mass analyzer and hits the electrode surface of an electron multiplier. The generated secondary electrons are amplified by multiple stages and output to an amplifier, and are finally converted into quantifiable data signals by computer processing.

[0062] Further, the HPLC-MS conditions of the detection method are:

[0063]

[0064]

[0065] Furthermore, the mobile phase A is obtained by dissolving 2.0 mL of aqueous ammonia in a mixed solution of 900 mL of water and 100 mL of acetonitrile, adjusting the pH to 2.5 with perfluorobutyric acid, mixing, and ultrasonicating.

[0066] Furthermore, the mobile phase B is obtained by dissolving 1.0 mL of perfluorobutyric acid in 1000 mL of acetonitrile, and mixing and ultrasonicating. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 : Spectrum of standard solution of compound I.

[0068] Figure 2 : LOD solution spectrum of compound I.

[0069] Figure 3 : LOQ solution spectrum of compound I.

[0070] Figure 4 : HPLC reaction control spectrum of compound I prepared by Example 3.

[0071] Figure 5 : HPLC purity profile of compound I.

[0072] Figure 6 : NMR spectrum of compound I. DETAILED DESCRIPTION

[0073] The technical solution of the present invention will be further described and illustrated below in conjunction with specific embodiments.

[0074] This embodiment is only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0075] the term:

[0076] The terms “comprising” and “including” should be interpreted as open ended, indicating the presence of the listed elements but not excluding the existence, occurrence or addition of any other one or more elements that are not listed.

[0077] All ranges recited herein include those endpoints of the range between the two values ​​recited.All values ​​recited herein, whether stated or not, include the degree of expected experimental error, technical error, and instrumental error for the given technique used to measure the value.

[0078] The abbreviations used in the present invention are explained as follows:

[0079] ppm: parts per million

[0080] LCMS: Liquid chromatography-mass spectrometry

[0081] ESI-MS: Electrospray Mass Spectrometry

[0082] 1 H NMR: Hydrogen nuclear magnetic resonance

[0083] HFBA: Perfluorobutyric acid

[0084] ACN: Acetonitrile

[0085] D2O: Heavy Water

[0086] Main instruments: High performance liquid chromatography equipped with mass spectrometer

[0087] Detection method of compound I in ornidazole:

[0088] Diluent: NH4OH:H2O:ACN=2:900:100 (V / V / V), pH 2.5 (2.0 mL of ammonia water was dissolved in a mixed solution of 900 mL of water and 100 mL of acetonitrile, and the pH was adjusted to 2.5 with perfluorobutyric acid, mixed, and sonicated)

[0089] Blank solution: diluent

[0090] Compound I stock solution: Prepare a Compound I stock solution containing Compound I at a concentration of 2 μg / mL. (For example: weigh 20 mg of Compound I, accurately weigh it in a 20 mL volumetric flask, dissolve it with diluent and dilute it to the mark, mix it; accurately transfer 1.0 mL of the solution to a 50 mL volumetric flask, dilute it to the mark with diluent, mix it; accurately transfer 1.0 mL of the solution to a 10 mL volumetric flask, dilute it to the mark with diluent, mix it.)

[0091] Compound I standard solution (Imp standard): Prepare a standard solution containing Compound I at a concentration of 0.2 μg / mL. (For example: accurately transfer 2.0 mL of Compound I stock solution to a 20 mL volumetric flask, dilute to the mark with diluent, and mix well.)

[0092] Sensitivity (LOQ) solution: Prepare a sensitivity solution containing 66 ng / mL of Compound I. (For example: Accurately pipette 3.3 mL of the Compound I standard solution into a 10 mL volumetric flask, dilute to the mark with diluent, and mix well.)

[0093] Limit of detection (LOD) solution: Prepare a sensitive solution containing 20 ng / mL of compound I. (For example: accurately pipette 1.0 mL of compound I standard solution into a 10 mL volumetric flask, dilute to the mark with diluent, and mix well.)

[0094] Ornidazole test solution: Prepare a test solution containing 10 mg / mL of ornidazole. (For example: weigh 10 mg of ornidazole sample, accurately weigh it into a 1.5 ml injection vial, accurately transfer 1.0 ml of diluent into the injection vial, dissolve, and mix.)

[0095] Recovery solution: Prepare a recovery solution containing 0.2 μg / mL of compound I and 10 mg / mL of ornidazole. (For example: weigh 10 mg of ornidazole reference substance, accurately weigh it into a 1.5 ml injection vial, accurately transfer 1.0 mL of compound I standard solution into the injection vial, dissolve, and mix.)

[0096] Program control solution: Same as compound I standard solution.

[0097] HPLC and mass spectrometry conditions:

[0098]

[0099]

[0100] Mobile phase A: 2.0 mL of aqueous ammonia was dissolved in a mixed solution of 900 mL of water and 100 mL of acetonitrile, and then the pH was adjusted to 2.5 with perfluorobutyric acid, mixed, and obtained by ultrasonication.

[0101] Mobile phase B: Dissolve 1.0 mL of perfluorobutyric acid in 1000 mL of acetonitrile, mix and sonicate.

[0102] Analytical methods:

[0103] Injection procedure:

[0104] Serial number name Number of needles 1 Blank solution 1 needle or more needles 2 Limit of Detection (LOD) Solution 1 needle 3 Sensitivity (LOQ) Solution 1 needle 4 Compound I standard solution (Imp standard) 5-pin 5 Blank solution 1 needle 6 Blank solution 1 needle 7 Sample solution 1 needle 8 Recovery Solution 1 needle 9 Blank solution 1 needle 10 Program Control Solution (Control) 1 needle

[0105] Inject samples according to the above-mentioned HPLC and mass spectrometry conditions and injection procedures, and record the chromatographic process.

[0106] System adaptability requirements:

[0107] Blank solution: In the obtained mass spectrum, there is no obvious interference at compound I (not greater than half of the peak area of ​​the main peak in the LOD solution).

[0108] Retention time of compound I: In the mass spectrum obtained, the retention time range of compound I is 6.3 min ± 5.0%. The proportion of the organic phase in the initial mobile phase A can be appropriately adjusted to ensure that the retention time of the main peak is within the above time range.

[0109] Sensitivity solution: In the obtained mass spectrum, the signal-to-noise ratio S / N of compound I shall not be less than 10.

[0110] Compound I standard solution: RSD of mass spectra obtained from 5 injections of Compound I standard solution was ≤10.0% based on the main peak area; RSD of mass spectra obtained from all Compound I standard solutions and program control solutions was ≤15% based on the main peak area.

[0111] Recovery rate of compound I: The recovery rate is 70.0%-130.0%.

[0112] Calculation: Calculated by external standard method.

[0113] The quantification limit of compound I in ornidazole is 6.6 ppm; the detection limit is 2 ppm.

[0114] Comparative Example 1:

[0115] Ornidazole was prepared according to Example 1 of CN101633643B, wherein the content of compound I was 0.31%.

[0116] Example 1: Preparation of Ornidazole

[0117] Add 50g of compound II to 400ml of ethyl acetate, add 52.5g of AlCl3 at 15-30℃, stir for 1 hour, cool to 0-10℃, add a certain amount of compound III, keep warm for 1 hour, slowly add 150ml of water to quench the reaction solution, control the temperature at 0-5℃ and filter. Add 33.6g of 25% ammonia water to the filtrate at 15-25℃, stir for 0.2-0.5 hours, stand for stratification, and retain the organic phase. Wash the organic phase twice with 75ml*2 water at 15-25℃ to remove ethyl acetate to obtain ornidazole.

[0118] Samples 1 to 3 were obtained by the above preparation method, wherein the amount of compound III was 36.4 g, 45.1 g, and 51.0 g, respectively. After three experiments, each sampling point was analyzed by high performance liquid chromatography, and the results are shown in Table 2.

[0119] Table 2.

[0120]

[0121]

[0122] Example 2: Preparation of Compound I

[0123] Add 100mL ethyl acetate and 10g ornidazole to a 250ml reaction bottle, add 10.5g AlCl3 at a temperature of 15-30°C and stir for 1 hour, control the system temperature to below 30°C and drop 6.3g epichlorohydrin. After the dropwise addition, keep warm and stir at 20°C-30°C for 1 hour. Add the system to 12mL ice water, stir for 15 minutes, and separate the liquids. Wash the organic phase twice with 15mL water, and combine the aqueous phases. Extract the aqueous phase twice with 30mL ethyl acetate, and concentrate the aqueous phase to obtain 4.4g of the compound of formula I, 1-chloro-3-((1-chloro-3-(2-methyl-5-nitro-1H-imidazole-1-yl)propan-2-yl)oxy)propan-2-ol.

[0124] LCMS (ESI-MS) m / z: 312.05, 314.05 (M+H + ), dichloro characteristic peak;

[0125] NMR: 1H NMR(600MHz,D2O)δ8.75(s,1H),4.91(ddd,J=14.8,4.7,2.8Hz,1H),4.63(dt,J=14.7,10.2Hz,1H),4.54(dt,J=14.7,3.4Hz,1H),4.42(ddd,J= 14.7,9.0,2.5Hz,1H),4.38–4.33(m,1H),4.30(dt,J=8.6,3.3Hz,1H),3.81(qd,J=11.9,4.7Hz,2H),3.77–3.67(m,2H),2.84(d,J=2.8Hz,3H).

[0126] Example 3: Preparation of Compound I

[0127] Add 100mL ethyl acetate and 10g 2-methyl-5-nitroimidazole to a 250ml reaction bottle, add 12.5g AlCl3 and stir for 1 hour at a temperature of 15-30°C, and then add 15g epichlorohydrin at a temperature of below 30°C. After the addition, keep warm and stir at 20°C-30°C for 1 hour. Add the system to 12mL ice water, stir for 15 minutes, filter, and separate. Wash the organic phase twice with 15mL water, and combine the aqueous phases. Extract the aqueous phase twice with 30mL ethyl acetate, and concentrate the aqueous phase to obtain 3g of the compound of formula I, 1-chloro-3-((1-chloro-3-(2-methyl-5-nitro-1H-imidazole-1-yl)propan-2-yl)oxy)propan-2-ol.

[0128] LCMS (ESI-MS) m / z: 312.05, 314.05 (M+H + ), dichloro characteristic peak;

[0129] NMR: 1H NMR(600MHz,D2O)δ8.75(s,1H),4.91(ddd,J=14.8,4.7,2.8Hz,1H),4.63(dt,J=14.7,10.2Hz,1H),4.54(dt,J=14.7,3.4Hz,1H),4.42(ddd,J= 14.7,9.0,2.5Hz,1H),4.38–4.33(m,1H),4.30(dt,J=8.6,3.3Hz,1H),3.81(qd,J=11.9,4.7Hz,2H),3.77–3.67(m,2H),2.84(d,J=2.8Hz,3H).

Claims

1. A method for preparing ornidazole, characterized in that: The following steps are involved: (1) 2-methyl-5-nitroimidazole reacts with epichlorohydrin in an organic solvent in the presence of an acid. After the reaction is completed, a reaction solution is obtained. (2) quenching the reaction solution obtained in step (1) with water, filtering, and directly adjusting the pH value of the filtrate with a weak base without adding an acid to adjust the pH, and then separating the organic phase; (3) washing the organic phase in step (2) with water and concentrating it to obtain ornidazole; Wherein, the organic solvent in step (1) is immiscible with water.

2. The preparation method according to claim 1, characterized in that: In step (1), the acid is selected from one or more of formic acid, acetic acid, sulfuric acid or aluminum chloride, preferably aluminum chloride.

3. The preparation method according to claim 1, characterized in that: In step (1), the organic solvent is selected from one or more of ethyl acetate, dichloromethane, chloroform or ether, preferably ethyl acetate; and the reaction temperature is 0 to 10°C.

4. The preparation method according to claim 1, characterized in that: In the step (1), the molar ratio of 2-methyl-5-nitroimidazole to acid and epichlorohydrin is 1:0.7-10:1-1.

5.

5. The preparation method according to claim 1, characterized in that: The volume mass ratio of the amount of water used for quenching with water in step (2) to the 2-methyl-5-nitroimidazole in step (1) is 1 to 10:1, preferably 3:1, and the quenching temperature is 0 to 10°C, preferably 0 to 5°C.

6. The preparation method according to claim 1, characterized in that: In step (2), the filtration temperature is controlled at 0-5°C.

7. The preparation method according to claim 1, characterized in that: In step (2), the weak base is selected from one or more of diethylamine, triethylamine, aqueous ammonia or sodium bicarbonate, and the pH value is adjusted to 5-6, preferably aqueous ammonia.

8. The preparation method according to claim 1, characterized in that: In the step (2), the molar ratio of the weak base to 2-methyl-5-nitroimidazole is 1 to 1.25:1, preferably 1.25:

1.

9. The preparation method according to claim 1, characterized in that: In step (3), the organic phase is washed with water 2 to 3 times, preferably 2 times; the volume mass ratio of water used for each washing to 2-methyl-5-nitroimidazole in step (1) is 0.5 to 20:1, preferably 1.5:

1.

10. Ornidazole prepared by the method according to any one of claims 1 to 9.

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