Method for detecting dipropylmalonic acid and impurities thereof

Abstract

The invention belongs to the technical field of medicine detection, and particularly relates to dipropyl malonic acid prepared by a dimethyl malonate method and a detection method of impurities of the dipropyl malonic acid. According to the detection method provided by the invention, the dipropyl malonic acid prepared by a dimethyl malonate method and impurities thereof are detected through high performance liquid chromatography (HPLC) for the first time; the impurities comprise propyl malonic acid, 2-methyl-2-propyl malonic acid, 2-propyl-2-butyl malonic acid, propyl malonic acid monomethyl ester, 2-methyl-2-propyl malonic acid monomethyl ester, dipropyl malonic acid monomethyl ester, 2-propyl-2-butyl malonic acid monomethyl ester, propyl malonic acid dimethyl ester, dipropyl malonic acid monopropyl ester and propyl malonic acid dimethyl ester; the invention relates to a method for preparing dipropyl malonic acid, which is selected from one or more of dipropyl malonic acid dimethyl ester, dipropyl malonic acid methyl ester propyl ester and 2-propyl-2-butyl malonic acid dimethyl ester, and solves the problems of quality control and process evaluation of dipropyl malonic acid serving as an intermediate of sodium valproate prepared by a dimethyl malonate method.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of drug detection, and particularly relates to a detection method of dipropyl malonic acid prepared by dimethyl malonate method and impurities thereof. BACKGROUND

[0002] Chinese invention patent [Preparation and hydrolysis method of 2-alkyl-2-propyl malonic acid diester, CN117430509A, 2024.1.23] speculates that 2-dipropyl malonic acid methyl propyl ester, 2-methyl-2-propyl malonic acid dimethyl ester (II), 2-propyl-2-butyl malonic acid dimethyl ester and 2-propyl-2-isopropyl malonic acid dimethyl ester may be contained in the preparation of dimethyl dipropyl malonate product; wherein II is hydrolyzed in the subsequent process to produce 2-methyl-2-propyl malonic acid (I) as a byproduct; the existence of impurity I will seriously affect the quality of dipropyl malonic acid; the impurity is subsequently transferred to the target product in the subsequent reaction, forming impurity 2-methyl valeric acid in the production of sodium valproate.

[0003]

[0004] Chinese patent CN118373737A discloses a preparation method of valproic acid, dimethyl malonate and 1-chloropropane are used to prepare dimethyl dipropyl malonate, dimethyl dipropyl malonate is hydrolyzed to obtain dipropyl malonic acid, and dipropyl malonic acid is decarboxylated to obtain valproic acid, and valproic acid is salted to obtain sodium valproate raw material drug. In the sodium valproate raw material drug, the technician detects the impurity 2-methyl valeric acid (L).

[0005] Regarding the pathway of 2-methyl valeric acid, Chinese patent CN117430509A considers that dimethyl dipropyl malonate contains 2-methyl-2-propyl malonic acid dimethyl ester (II), which produces 2-methyl-2-propyl malonic acid (I) in the hydrolysis reaction, and 2-methyl-2-propyl malonic acid is transferred to sodium valproate raw material drug in the subsequent reaction, forming impurity 2-methyl valeric acid (L), and the specific reaction is as follows:

[0006]

[0007] At present, the residual amount of 2-methyl valeric acid in sodium valproate raw material drug is high, and Chinese patent CN112972449A discloses that pharmacological tests show that 2-methyl valeric acid has vascular irritation, which can cause sodium valproate injection to have vascular irritation. Therefore, Chinese patent CN112972449A discloses a pharmaceutical composition, the content of sodium valproate is not less than 90%, and the content of 2-methyl valeric acid is not more than 0.014%, which can reduce the vascular irritation of sodium valproate drug.

[0008] However, there is no report on a detection method with high accuracy for 2-methylvaleric acid in sodium valproate bulk drug; and there is no detection method for impurities in dipropyl malonic acid or monomethyl dipropyl malonate prepared by dimethyl malonate method. SUMMARY

[0009] The application aims to provide a detection method for dipropyl malonic acid prepared by dimethyl malonate method and impurities thereof, and the detection method provided by the application realizes accurate detection and control of 2-methylvaleric acid in sodium valproate bulk drug by detecting 2-methyl-2-propyl malonic acid.

[0010] In order to achieve the above-mentioned purpose, the application provides the following technical scheme:

[0011] The application provides a detection method for dipropyl malonic acid prepared by dimethyl malonate method and impurities thereof, which utilizes high-performance liquid chromatography testing and comprises the following steps:

[0012] Mixing a test sample, acetonitrile and water to obtain a test sample solution;

[0013] Injecting a blank solution and the test sample solution into a high-performance liquid chromatograph to record a chromatogram; the chromatographic column of the high-performance liquid chromatograph is an Ultimate ODS-3 (4.6 mm x 250 mm, 5 μm), the detector is an SPD-20A, the detection wavelength is 200-215 nm, the flow rate is 0.8-1.2 mL / min, the mobile phase A is a trifluoroacetic acid solution, the mobile phase B is acetonitrile, and the volume ratio of the mobile phase A to the mobile phase B is 20-50:80-50; the test sample comprises dipropyl malonic acid prepared by dimethyl malonate method and impurities thereof; the impurities comprise at least one of propyl malonic acid, 2-methyl-2-propyl malonic acid, 2-propyl-2-butyl malonic acid, monomethyl propyl malonate, 2-methyl-2-propyl malonic acid monomethyl ester, dipropyl malonic acid monomethyl ester, 2-propyl-2-butyl malonic acid monomethyl ester, propyl malonic acid dimethyl ester, dipropyl malonic acid monopropyl ester, propyl malonic acid dimethyl ester, dipropyl malonic acid dimethyl ester, dipropyl malonic acid methyl propyl ester and 2-propyl-2-butyl malonic acid dimethyl ester.

[0014] Preferably, the concentration of the test sample in the test sample solution is 3-4 mg / mL.

[0015] Preferably, the column length of the chromatographic column of the high-performance liquid chromatograph is 250 mm, the inner diameter is 4.6 mm, and the packing particle size is 5 μm.

[0016] Preferably, when the test sample solution is injected into the high-performance liquid chromatograph, the column temperature of the chromatographic column of the high-performance liquid chromatograph is 32℃.

[0017] Preferably, the volume concentration of the trifluoroacetic acid solution is 0.1%; the solvent of the trifluoroacetic acid solution is water.

[0018] Preferably, the volume ratio of the acetonitrile and water is 1:1.

[0019] Preferably, the recording chromatogram further comprises: calculating the content of the compound by area normalization method.

[0020] The application further provides a preparation method of 2-methyl-2-propyl malonic acid, which comprises the following steps: mixing dimethyl malonate, 1-halogenated propane and a phase transfer catalyst to perform a propylation reaction (denoted as a propylation reaction of dimethyl malonate), so as to obtain 2-methyl-2-propyl malonic acid dimethyl ester; and performing a hydrolysis reaction of the 2-methyl-2-propyl malonic acid dimethyl ester with water (denoted as a dimethyl ester hydrolysis reaction), so as to obtain the 2-methyl-2-propyl malonic acid.

[0021] The application further provides a preparation method of dimethyl malonic acid monomethyl ester, which comprises the following steps: performing a dimethyl ester semi-hydrolysis reaction of dimethyl dipropyl malonate with water, so as to obtain the dimethyl malonic acid monomethyl ester.

[0022] The application further provides a preparation method of dimethyl malonic acid monomethyl ester, which comprises the following steps: performing a dimethyl ester semi-hydrolysis reaction of dimethyl dipropyl malonate with water, so as to obtain the dimethyl malonic acid monomethyl ester.

[0023] The application provides a detection method for dimethyl malonic acid and impurities thereof prepared by a dimethyl malonic acid method. The detection method provided by the application realizes detection of dimethyl malonic acid and impurities thereof prepared by a dimethyl malonic acid method through high performance liquid chromatography (HPLC) for the first time, the impurities include one or more of propyl malonic acid, 2-methyl-2-propyl malonic acid, 2-propyl-2-butyl malonic acid, propyl malonic acid monomethyl ester, 2-methyl-2-propyl malonic acid monomethyl ester, dimethyl malonic acid monomethyl ester, 2-propyl-2-butyl malonic acid monomethyl ester, propyl malonic acid dimethyl ester, dimethyl malonic acid monopropyl ester, propyl malonic acid dimethyl ester, dimethyl malonic acid dimethyl ester, dimethyl malonic acid methyl propyl ester and 2-propyl-2-butyl malonic acid dimethyl ester, and solves the problems of quality control and process evaluation of dimethyl malonic acid prepared by a dimethyl malonic acid method, which is an intermediate of sodium valproate.

[0024] The impurities in the dipropylmalonic acid sample are selected from one or more of propylmalonic acid, 2-methyl-2-propylmalonic acid, dipropylmalonic acid, 2-propyl-2-butylmalonic acid, propylmalonic acid monomethyl ester, 2-methyl-2-propylmalonic acid monomethyl ester, 2-propyl-2-butylmalonic acid monomethyl ester, propylmalonic acid dimethyl ester, dipropylmalonic acid monopropyl ester, propylmalonic acid dimethyl ester, dipropylmalonic acid dimethyl ester, dipropylmalonic acid methylpropyl ester and 2-propyl-2-butylmalonic acid dimethyl ester.

[0025] The impurities in the dipropylmalonic acid sample are selected from one or more of propylmalonic acid, 2-methyl-2-propylmalonic acid, dipropylmalonic acid, 2-propyl-2-butylmalonic acid, propylmalonic acid monomethyl ester, 2-methyl-2-propylmalonic acid monomethyl ester, 2-propyl-2-butylmalonic acid monomethyl ester, propylmalonic acid dimethyl ester, dipropylmalonic acid monopropyl ester, propylmalonic acid dimethyl ester, dipropylmalonic acid dimethyl ester, dipropylmalonic acid methylpropyl ester and 2-propyl-2-butylmalonic acid dimethyl ester.

[0026] The impurities in the dipropylmalonic acid sample are selected from one or more of propylmalonic acid, 2-methyl-2-propylmalonic acid, dipropylmalonic acid, 2-propyl-2-butylmalonic acid, propylmalonic acid monomethyl ester, 2-methyl-2-propylmalonic acid monomethyl ester, 2-propyl-2-butylmalonic acid monomethyl ester, propylmalonic acid dimethyl ester, dipropylmalonic acid monopropyl ester, propylmalonic acid dimethyl ester, dipropylmalonic acid dimethyl ester, dipropylmalonic acid methylpropyl ester and 2-propyl-2-butylmalonic acid dimethyl ester.

[0027] The impurities in the dipropylmalonic acid sample are selected from one or more of propylmalonic acid, 2-methyl-2-propylmalonic acid, dipropylmalonic acid, 2-propyl-2-butylmalonic acid, propylmalonic acid monomethyl ester, 2-methyl-2-propylmalonic acid monomethyl ester, 2-propyl-2-butylmalonic acid monomethyl ester, propylmalonic acid dimethyl ester, dipropylmalonic acid monopropyl ester, propylmalonic acid dimethyl ester, dipropylmalonic acid dimethyl ester, dipropylmalonic acid methylpropyl ester and 2-propyl-2-butylmalonic acid dimethyl ester.

[0028] The impurities in the dipropylmalonic acid sample are selected from one or more of propylmalonic acid, 2-methyl-2-propylmalonic acid, dipropylmalonic acid, 2-propyl-2-butylmalonic acid, propylmalonic acid monomethyl ester, 2-methyl-2-propylmalonic acid monomethyl ester, 2-propyl-2-butylmalonic acid monomethyl ester, propylmalonic acid dimethyl ester, dipropylmalonic acid monopropyl ester, propylmalonic acid dimethyl ester, dipropylmalonic acid dimethyl ester, dipropylmalonic acid methylpropyl ester and 2-propyl-2-butylmalonic acid dimethyl ester.

[0029] Compared with the prior art, the present application has the following advantages:

[0030] (1) The present application is the first to use methylmalonic acid dimethyl ester to prepare 2-methyl-2-propylmalonic acid by phase transfer catalysis, and the preparation reaction is as follows:

[0031]

[0032] (2) First selection HPLC detection and confirmation of new impurities 2-methyl-2- propylmalonic acid, 2-propyl-2-butylmalonic acid, 2-methyl-2-propylmalonic acid monomethyl ester, 2-propyl-2-butylmalonic acid monomethyl ester, dipropylmalonic acid monopropyl ester, 2-methyl-2-propylmalonic acid dimethyl ester, dipropylmalonic acid methyl propyl ester and 2-propyl-2-butylmalonic acid dimethyl ester in dipropylmalonic acid prepared by the dimethyl malonate method.

[0033] (3) No detection of 2-ethyl-2-propylmalonic acid, dipropylmalonic acid monoethyl ester and dipropylmalonic acid diethyl ester in dipropylmalonic acid prepared by the dimethyl malonate method. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0035] Figure 1 High performance liquid chromatogram of dipropylmalonic acid product prepared for Example 1;

[0036] Figure 2 High performance liquid chromatogram of dipropylmalonic acid product prepared for Example 2;

[0037] Figure 3 High performance liquid chromatogram of 2-methyl-2-propylmalonic acid reference substance prepared for Example 4;

[0038] Figure 4 High performance liquid chromatogram of 2-propyl-2-butylmalonic acid reference substance prepared for Example 6;

[0039] Figure 5 High performance liquid chromatogram of dipropylmalonic acid monomethyl ester reference substance prepared for Example 7;

[0040] Figure 6 High performance liquid chromatogram of dipropylmalonic acid reaction solution prepared for Example 3;

[0041] Figure 7 High performance liquid chromatogram of dipropylmalonic acid monomethyl ester reaction solution prepared for Example 7;

[0042] Figure 8 High performance liquid chromatogram of propylmalonic acid reference substance (purchased). DETAILED DESCRIPTION

[0043] The application provides a method for detecting dipropyl malonic acid prepared by dimethyl malonate method and impurities thereof, and utilizes high performance liquid chromatography testing, and comprises the following steps:

[0044] Main experimental instruments:

[0045] HPLC: Tsushima high performance liquid chromatograph;

[0046] Infusion pump: LC-20AT;

[0047] Detector: SPD-20A;

[0048] Chromatographic analysis processing system: LCsolution;

[0049] Mixing the test product, acetonitrile and water to obtain a test product solution;

[0050] Injecting the blank solution and the test product solution into the high performance liquid chromatograph to record a chromatogram; the high performance liquid chromatography conditions are as follows: the chromatographic column is Ultimate ODS-3 (4.6mm*250mm, 5um), the detection wavelength is 200-215nm, the mobile phase A is trifluoroacetic acid solution, the mobile phase B is acetonitrile, the volume ratio of the mobile phase A and the mobile phase B is 20-50:80-50, the flow rate is 0.8-1.2mL / min, and the column temperature is 32 DEG C.

[0051] In the application, the test product can comprise dipropyl malonic acid and impurities thereof; the impurities can comprise at least one of propyl malonic acid, 2-methyl-2-propyl malonic acid, 2-propyl-2-butyl malonic acid, propyl malonic acid monomethyl ester, 2-methyl-2-propyl malonic acid monomethyl ester, dipropyl malonic acid monomethyl ester, 2-propyl-2-butyl malonic acid monomethyl ester, propyl malonic acid dimethyl ester, dipropyl malonic acid monopropyl ester, propyl malonic acid dimethyl ester, dipropyl malonic acid dimethyl ester, dipropyl malonic acid methyl propyl ester and 2-propyl-2-butyl malonic acid dimethyl ester.

[0052] In the application, the concentration of the test product in the test product solution can be 3-4mg / mL.

[0053] In the application, the water can be purified water; and the volume ratio of the acetonitrile and the water can be 1:1.

[0054] In the application, the mixing A can comprise the following steps: placing the test product in a measuring flask, adding water and acetonitrile to dissolve and dilute to the scale, and shaking uniformly.

[0055] After obtaining the test sample solution, the present application injects the blank solution and the test sample solution into the high performance liquid chromatograph, and records the chromatogram. In the present application, the injection amount of the test sample solution can be 20 μL.

[0056] In the present application, the column length of the chromatographic column of the high performance liquid chromatograph can be 250 mm, the inner diameter can be 4.6 mm, and the packing particle size can be 5 μm.

[0057] In the present application, when the test sample solution is injected into the high performance liquid chromatograph, the column temperature of the chromatographic column of the high performance liquid chromatograph can be 32℃.

[0058] In the present application, the volume concentration of the trifluoroacetic acid solution can be 0.1%; the solvent of the trifluoroacetic acid solution can be water; and the water can be purified water.

[0059] In the present application, after recording the chromatogram, the present application can further comprise: calculating the content of the compound by area normalization method.

[0060] The test method provided by the present application can be used for determining at least one impurity in the dimethyl malonate method prepared dipropyl malonic acid, propyl malonic acid, 2-methyl-2-propyl malonic acid, 2-propyl-2-butyl malonic acid, propyl malonic acid monomethyl ester, 2-methyl-2-propyl malonic acid monomethyl ester, dipropyl malonic acid monomethyl ester, 2-propyl-2-butyl malonic acid monomethyl ester, propyl malonic acid dimethyl ester, dipropyl malonic acid monopropyl ester, propyl malonic acid dimethyl ester, dipropyl malonic acid dimethyl ester, dipropyl malonic acid methyl propyl ester and 2-propyl-2-butyl malonic acid dimethyl ester, and can also be used for determining at least one impurity in the dimethyl malonate method prepared dipropyl malonic acid monomethyl ester.

[0061] In order to further illustrate the present application, the schemes of the present application are described in detail below in combination with the drawings and examples, but they should not be understood as limiting the protection scope of the present application.

[0062] Example 1

[0063] Preparation of dipropyl malonic acid

[0064] Preparation of dipropyl malonic acid 0.10 mol of dimethyl malonate and 0.15 mol of potassium carbonate were prepared according to the preparation method of Example 1 of Chinese patent CN118373737A to obtain dipropyl malonic acid, HPLC: 98.310%, the high performance liquid chromatogram of dipropyl malonic acid of the present example is shown in Figure 1 .

[0065] Example 2

[0066] Preparation of dipropyl malonic acid

[0067] 0.10 mol of dimethyl malonate and 0.16 mol of potassium carbonate were prepared according to the preparation method of Example 1 of Chinese patent CN118373737A to obtain dipropyl malonic acid, HPLC: 99.450%, the high performance liquid chromatogram of dipropyl malonic acid of the present example is shown in Figure 2 .

[0068] Example 3

[0069] Preparation of dipropyl malonic acid

[0070] 0.10 mol of dimethyl malonate and 0.17 mol of potassium carbonate were prepared according to the preparation method of Example 1 of Chinese patent CN118373737A to obtain a dipropyl malonic acid reaction solution, the high performance liquid chromatogram of the dipropyl malonic acid reaction solution of the present example is shown in Figure 7 .

[0071] Example 4

[0072] Preparation of 2-methyl-2-propyl malonic acid

[0073]

[0074] To the reactor were added sequentially 0.2 mol dimethyl methylmalonate, 0.01 mol tetramethylammonium bromide, 0.03 mol KBr, 0.3 mol K2CO3, 120 mL DMF, 0.32 mol 1-chloropropane, stirred at 90°C for 1 h, stirred at 110°C for 7 h, stirred at 125°C for 4 h; after the reaction was complete, it was allowed to cool to room temperature, suction filtered to obtain a first filtrate and a first filter cake; the filter cake was slurried with methanol (60 mL), filtered to obtain a second filtrate and a second filter cake, which was 56.41 g of inorganic salts; the first filtrate and the second filtrate were combined, distilled to recover 60 mL of methanol, and then DMF was recovered under reduced pressure (for use in the next cycle); a potassium hydroxide solution (KOH: 32 g, water: 32 g) and 20 mL of methanol were added, and the mixture was stirred at 80-90°C for 3 h; after the reaction was complete, the mixture was concentrated at 100-120°C under normal pressure for 0.5 h, 10 g of water was added, and the mixture was hydrolyzed for another 2.5 h; after the reaction was complete, the mixture was concentrated at 100-120°C under normal pressure for 1.5 h, the temperature was raised to 150°C, and the mixture was concentrated for another 1 h to obtain a first solid in light yellow; the first solid was dissolved in 50 mL of water, and the pH was adjusted to 1-1.5 with concentrated hydrochloric acid; a second solid was obtained by suction filtration.

[0075] The third filtrate was combined with the inorganic salts, concentrated, crystallized, and dried to recover KCl solid; the second solid was recrystallized in a methanol aqueous solution to obtain 2-methyl-2-propylmalonic acid 16.6 g; mp. 106-108°C, yield 51.7%, HPLC purity 99.472%. The high performance liquid chromatogram of 2-methyl-2-propylmalonic acid in this example is shown in Fig. 2. Figure 3

[0076] 1 HNMR (400 MHz, DMSO-d6) δ: 12.60 (s, 2H, COOH x 2), 1.69-1.64 (m, 2H, CH2), 1.23 (s, 3H, CH3), 1.21-1.14 (m, 2H, CH2), 0.86 (t, J = 7.2 Hz, 3H, CH3).

[0077] Example 5

[0078] Preparation of 2-methylpentanoic acid

[0079]

[0080] The 2-methyl-2-propylmalonic acid 16.0 g was placed in a single-necked round-bottom flask, and decarboxylation was carried out at 180-190°C for 2 h to obtain dark brown liquid 11.36 g; rectification was carried out to obtain colorless liquid 2-methylpentanoic acid 7.2 g, yield 62.1%, HPLC purity 99.1%.

[0081] ​1 H NMR (400 MHz, DMSO-d6) δ: 11.05 (s, 1H, COOH), 2.30~2.22 (m, 1H, CH), 1.55~1.45 (m, 1H, 0.5CH2), 1.28~1.21 (m, 3H, CH2+0.5CH2), 1.00 (d, J=7.2 Hz, 3H, CH3), 0.81 (t, J=7.2 Hz, 3H, CH3).

[0082] Example 6

[0083] Preparation of 2-propyl-2-butylmalonic acid

[0084] 2-Propyl-2-butylmalonic acid was prepared according to Example 1 of Chinese patent CN116730832A, HPLC: 93.277%, the high performance liquid chromatogram of 2-propyl-2-butylmalonic acid of this example is shown in Figure 4 .

[0085] 1 H NMR (DMSO-d6, 400 MHz) δ: 0.88 (t, J=6.8 Hz, 3H, CH3), 0.89 (t, J=6.8 Hz, 3H, CH3), 1.08~1.17 (m, 4H, CH2CH2), 1.26~1.32 (m, 2H, CH2), 1.69~1.75 (m, 4H, CH2x2), 12.61 (s, 2H, CO2H).

[0086] Example 7

[0087] Preparation of dipropyl malonic acid monomethyl ester

[0088]

[0089] Under ice bath condition, 20 g of 35wt% sodium hydroxide solution was added dropwise into a solution containing 20 g (0.09 mol) of dipropyl malonic acid dimethyl ester in methanol (15 mL), after the dropwise addition was completed, the reaction was stirred at 30°C for 14 h. The methanol was removed by rotary evaporation, 10wt% sodium hydroxide aqueous solution was added, the pH value of the solution was adjusted to 12, ethyl acetate was added for extraction (30 mL x 3), the lower water layer was taken out, the organic layer was back-extracted with 10wt% sodium hydroxide aqueous solution, and the water layers were combined. The water layer was acidified with hydrochloric acid to a pH value of 1~2, ethyl acetate was added for extraction (30 mL x 3), the organic layers were combined, dried with anhydrous sodium sulfate, filtered, and the ethyl acetate was removed by rotary evaporation to obtain dipropyl malonic acid monomethyl ester 8.97 g, mp. 60~61°C, yield 48.0%, HPLC: 98.916%, the high performance liquid chromatogram of dipropyl malonic acid monomethyl ester of this example is shown in Figure 5 .

[0090] 1 HNMR (400 MHz, DMSO-d6) δ: 3.61 (s, 3H, CH3), 1.72 (t, J = 8.4 Hz, 4H, 2 x CH2), 1.14-1.07 (m, 4H, 2 x CH2), 0.86 (t, J = 7.3 Hz, 6H, 2 x CH3).

[0091] Example 8

[0092] Preparation of dipropyl malonic acid monopropyl ester

[0093]

[0094] Dipropyl malonic acid monopropyl ester was prepared by using dipropyl malonate as raw material, according to Chinese patent CN116768697A, and then the obtained dipropyl malonic acid monopropyl ester was hydrolyzed according to Example 6 of the present application to obtain dipropyl malonic acid monopropyl ester.

[0095] Example 9

[0096] HPLC detection

[0097] (1) Solution preparation:

[0098] Trifluoroacetic acid solution: 1 mL of trifluoroacetic acid was dissolved in 1000 mL of purified water to obtain a 0.1% (volume concentration) trifluoroacetic acid solution;

[0099] Diluent: a mixture of purified water and acetonitrile (volume ratio 50:50);

[0100] Test sample solution: 30-40 mg of test sample was weighed into a 10 mL volumetric flask, dissolved with diluent and diluted to the mark, shaken well to obtain the test sample solution;

[0101] (2) The liquid chromatography conditions are as follows:

[0102] Chromatographic column: Ultimate ODS-3 (4.6 mm x 250 mm, 5 μm);

[0103] Detection wavelength: 200-215 nm;

[0104] Mobile phase A: 0.1% (volume concentration) trifluoroacetic acid solution, 35%;

[0105] Mobile phase B: acetonitrile, 65%;

[0106] Flow rate: 1.0 mL / min;

[0107] Column temperature: 32°C;

[0108] (3) Test under the conditions of step (2) of HPLC, take the blank solution and the sample solution respectively, record the chromatogram, the HPLC of each sample solution is shown in Figures 1 to 7 According to the area normalization method, the content of the compound is calculated.

[0109] Select 2-ethyl-2-propylmalonic acid, dipropylmalonic acid monoethyl ester and dipropylmalonic acid diethyl ester as the control sample.

[0110] Select propylmalonic acid, 2-methyl-2-propylmalonic acid, 2-propyl-2-butylmalonic acid, dipropylmalonic acid monomethyl ester, dipropylmalonic acid monopropyl ester and dipropylmalonic acid dimethyl ester as the control sample.

[0111] Take the dipropylmalonic acid prepared in Example 1 for HPLC detection, and the results are shown in Figure 1 and Table 1.

[0112] Table 1 HPLC detection data of Example 1

[0113]

[0114] According to Figure 1 and Table 1, peak 1 (retention time 13.372 min, RRT = 0.70): 2-propylmalonic acid, 0.033%; peak 2 (retention time 15.922 min, RRT = 0.84): 2-methyl-2-propylmalonic acid, 0.243%; peak 4 (retention time 19.015 min, RRT = 1.00): dipropylmalonic acid, 98.310%; peak 5 (retention time 24.288 min, RRT = 1.28): dipropylmalonic acid monomethyl ester, 0.190%; peak 6 (retention time 25.151 min, RRT = 1.32): propylmalonic acid dimethyl ester, 0.128%; peak 8 (retention time 27.711 min, RRT = 1.46): dipropylmalonic acid monopropyl ester, 0.888%.

[0115] Take the dipropylmalonic acid prepared in Example 2 for HPLC detection, and the results are shown in Figure 2 and Table 2.

[0116] Table 2 HPLC detection data of Example 2

[0117]

[0118] According to Figure 2As shown in Table 2, peak 1 (retention time 13.370 min, RRT = 0.70): 2-propylmalonic acid, 0.067%; peak 2 (retention time 15.922 min, RRT = 0.84): 2-methyl-2-propylmalonic acid, 0.187%; peak 3 (retention time 19.020 min, RRT = 1.00): dipropylmalonic acid, 99.450%; peak 4 (retention time 24.284 min, RRT = 1.28): monomethyl dipropylmalonic acid, 0.035%; peak 5 (retention time 25.149 min, RRT = 1.32): dimethyl propylmalonic acid, 0.124%; peak 6 (retention time 27.716 min, RRT = 1.46): monopropyl dipropylmalonic acid, 0.077%.

[0119] The 2-methyl-2-propylmalonic acid reference standard prepared in Example 4 was sampled and analyzed by HPLC. The results are as follows: Figure 3 As shown in Table 3.

[0120] Table 3 HPLC detection data from Example 4

[0121]

[0122] according to Figure 3 As shown in Table 3, peak 2 (retention time 15.871 min): 2-methyl-2-propylmalonic acid, 99.472%.

[0123] The 2-propyl-2-butylmalonic acid reference standard prepared in Example 6 was sampled and analyzed by HPLC. The results are as follows: Figure 4 As shown in Table 4.

[0124] Table 4 HPLC detection data from Example 6

[0125]

[0126]

[0127] according to Figure 4 As shown in Table 4, peak 4 (retention time 19.280 min, RRT = 1.00): dipropylmalonic acid, 2.621%; peak 5 (retention time 21.506 min, RRT = 1.12): 2-propyl-2-butylmalonic acid, 93.462%.

[0128] The dipropylmalonic acid monomethyl ester reference standard prepared in Example 7 was sampled and analyzed by HPLC. The results are as follows: Figure 5 As shown in Table 5.

[0129] Table 5 HPLC detection data from Example 7

[0130]

[0131] According to Figure 5 It can be seen from Table 5 and Table 6 that peak 1 (retention time 16.346 min, RRT = 0.84): 2-methyl-2-propylmalonic acid, 0.053%; peak 2 (retention time 19.548 min, RRT = 1.00): dipropylmalonic acid, 0.439%; peak 4 (retention time 24.904 min, RRT = 1.27): dipropylmalonic acid monomethyl ester, 98.916%; peak 5 (retention time 25.623 min, RRT = 1.31): propylmalonic acid dimethyl ester, 0.017%; peak 8 (retention time 28.365 min, RRT = 1.45): dipropylmalonic acid monopropyl ester, 0.354%.

[0132] The reaction solution of dipropylmalonic acid prepared in Example 3 was sampled for HPLC detection, and the results are shown in Table 6. Figure 6

[0133] Table 6 HPLC detection data of the reaction solution of dipropylmalonic acid in Example 3

[0134]

[0135]

[0136] According to Figure 6 ​As can be seen from Table 6, Peak 1 (retention time 13.436 min, RRT = 0.70): 2-propylmalonic acid, 0.051%; Peak 2 (retention time 15.990 min, RRT = 0.84): 2-methyl-2-propylmalonic acid, 0.413%; Peak 4 (retention time 19.106 min, RRT = 1.00): dipropylmalonic acid, 88.343%; Peak 6 (retention time 21.401 min, RRT = 1.12): 2-propyl-2-butylmalonic acid, 0.025%; Peak 8 (retention time 24.166 min, RRT = 1.26): propylmalonic acid monomethyl ester, 0.016%; Peak 9 (retention time 24.426 min, RRT = 1.28): dipropylmalonic acid monomethyl ester, 1.603%; Peak 11 (retention time 26.220 min, RRT = 1.37): propylmalonic acid dimethyl ester, 1.034%; Peak 12 (retention time 27.866 min, RRT = 1.46): dipropylmalonic acid monopropyl ester, 6.898%; Peak 14 (retention time 29.517 min, RRT = 1.54): dipropylmalonic acid dimethyl ester, 0.451%; Peak 16 (retention time 32.858 min, RRT = 1.72): dipropylmalonic acid methylpropyl ester, 0.044%.

[0137] The reaction solution of dipropylmalonic acid monomethyl ester prepared in Example 7 was sampled and subjected to HPLC detection, and the results are shown in Table 7. Figure 7

[0138] Table 7 HPLC detection data of the reaction solution of dipropylmalonic acid monomethyl ester in Example 7

[0139]

[0140] According to Figure 7 ​As can be seen from Table 7, Peak 1 (retention time 13.583 min, RRT = 0.70): 2-propylmalonic acid, 1.213%; Peak 4 (retention time 16.143 min, RRT = 0.83): 2-methyl-2-propylmalonic acid, 0.607%; Peak 6 (retention time 19.456 min, RRT = 1.00): dipropylmalonic acid, 2.787%; Peak 8 (retention time 24.685 min, RRT = 1.27): monomethyl dipropylmalonate, 93.720%; Peak 9 (retention time 26.424 min, RRT = 1.36): dimethyl propylmalonate, 0.026%; Peak 10 (retention time 28.099 min, RRT = 1.44): monopropyl dipropylmalonate, 1.149%; Peak 12 (retention time 29.787 min, RRT = 1.53): dimethyl dipropylmalonate, 0.079%; Peak 13 (retention time 32.946 min, RRT = 1.69): methyl propyl dipropylmalonate, 0.033%.

[0141] The HPLC detection data of the samples of Examples 1, 2, 4, 6 and 7 are summarized in Table 8. The high performance liquid chromatogram of the control sample propylmalonic acid (purchased) is shown in Figure 1, with the peak appearing at 13.711 min. Figure 8

[0142] Table 8 HPLC detection data of Examples 1, 2, 4, 6 and 7

[0143]

[0144] ND: not detected.

[0145] The HPLC detection data of the sample of Example 1 and the reaction solution of Example 3 and the sample and reaction solution of Example 7 are summarized in Table 9.

[0146] Table 9 HPLC detection data of the sample and reaction solution

[0147]

[0148]

[0149] ND: not detected.

[0150] As can be seen from Tables 8 and 9, the impurities in the dipropylmalonic acid sample are propylmalonic acid, 2-methyl-2-propylmalonic acid, 2-propyl-2-butylmalonic acid, monomethyl dipropylmalonate and monopropyl dipropylmalonate, with the chemical structures being as follows:

[0151]

[0152] ​The impurities in the dipropyl malonic acid product or reaction solution are selected from one or more of propyl malonic acid, 2-methyl-2-propyl malonic acid, dipropyl malonic acid, 2-propyl-2-butyl malonic acid, propyl malonic acid monomethyl ester, 2-methyl-2-propyl malonic acid monomethyl ester, 2-propyl-2-butyl malonic acid monomethyl ester, propyl malonic acid dimethyl ester, dipropyl malonic acid monopropyl ester, propyl malonic acid dimethyl ester, dipropyl malonic acid dimethyl ester, dipropyl malonic acid methylpropyl ester and 2-propyl-2-butyl malonic acid dimethyl ester.

[0153] The impurities in the dipropyl malonic acid product or reaction solution are selected from one or more of propyl malonic acid, 2-methyl-2-propyl malonic acid, dipropyl malonic acid, 2-propyl-2-butyl malonic acid, propyl malonic acid monomethyl ester, 2-methyl-2-propyl malonic acid monomethyl ester, 2-propyl-2-butyl malonic acid monomethyl ester, propyl malonic acid dimethyl ester, dipropyl malonic acid monopropyl ester, propyl malonic acid dimethyl ester, dipropyl malonic acid dimethyl ester, dipropyl malonic acid methylpropyl ester and 2-propyl-2-butyl malonic acid dimethyl ester.

[0154] The relative peak times of the impurities in the dipropyl malonic acid prepared by the dimethyl malonate method are confirmed by HPLC detection: the RRT of propyl malonic acid is 0.70, the RRT of 2-methyl-2-propyl malonic acid is 0.84, the RRT of dipropyl malonic acid is 1.00, the RRT of 2-propyl-2-butyl malonic acid is 1.12, the RRT of dipropyl malonic acid monomethyl ester is 1.28 or 1.27, and the RRT of dipropyl malonic acid monopropyl ester is 1.45.

[0155] 2-ethyl-2-propyl malonic acid, dipropyl malonic acid monoethyl ester and dipropyl malonic acid diethyl ester are not detected in the dipropyl malonic acid prepared by the dimethyl malonate method.

[0156] As can be seen from the above examples, the detection method provided by the present application realizes the detection of the dipropyl malonic acid prepared by the dimethyl malonate method and its impurities by high performance liquid chromatography for the first time, and solves the problems of quality control and process evaluation of the intermediate of sodium valproate, i.e., the dipropyl malonic acid prepared by the dimethyl malonate method.

[0157] Although the above examples have made a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained under the premise of no creativity according to the present embodiments, which all belong to the protection scope of the present application.

Claims

1. A method for detecting dipropylmalonic acid and its impurities prepared by the dimethyl malonate method, characterized in that, The test using high-performance liquid chromatography includes the following steps: Mix the test sample, acetonitrile, and water to obtain the test sample solution; Inject the blank solution and the test solution into the high-performance liquid chromatograph and record the chromatograms. The high-performance liquid chromatograph uses an Ultimate ODS-3 column, an SPD-20A detector, a detection wavelength of 200–215 nm, a mobile phase flow rate of 0.8–1.2 mL / min, mobile phase A is a trifluoroacetic acid solution, mobile phase B is acetonitrile, and the volume ratio of mobile phase A to mobile phase B is 20–50:80–50. The test sample includes dipropylmalonic acid prepared by the dimethyl malonate method and its impurities; the impurities include one or more of propylmalonic acid, 2-methyl-2-propylmalonic acid, 2-propyl-2-butylmalonic acid, propylmalonic acid monomethyl ester, 2-methyl-2-propylmalonic acid monomethyl ester, dipropylmalonic acid monomethyl ester, 2-propyl-2-butylmalonic acid monomethyl ester, dimethyl propylmalonic acid, dipropylmalonic acid monopropyl ester, dimethyl propylmalonic acid, dimethyl propyl dipropylmalonic acid, and 2-propyl-2-butylmalonic acid dimethyl ester.

2. The detection method according to claim 1, characterized in that, The concentration of the test sample in the test solution is 3-4 mg / mL; the column of the high-performance liquid chromatograph has a column length of 250 mm, an inner diameter of 4.6 mm, and a packing particle size of 5 μm; when the test sample solution is injected into the high-performance liquid chromatograph, the column temperature of the high-performance liquid chromatograph is 32 °C; the volume concentration of the trifluoroacetic acid solution is 0.1%. The solvent for the trifluoroacetic acid solution is water; The volume ratio of acetonitrile to water is 1:1; after recording the chromatogram, the method further includes: calculating the content of the compound by area normalization.

3. The detection method according to claim 1, characterized in that, The preparation method of the 2-methyl-2-propylmalonic acid includes the following steps: mixing dimethyl methylmalonic acid with 1-halopropane and a phase transfer catalyst to carry out a propylation reaction to obtain dimethyl 2-methyl-2-propylmalonic acid; and reacting the dimethyl 2-methyl-2-propylmalonic acid with water to undergo a dimethyl ester hydrolysis reaction to obtain the 2-methyl-2-propylmalonic acid.

4. The detection method according to claim 1, characterized in that, The preparation method of the dipropylmalonic acid monomethyl ester includes the following steps: reacting dipropylmalonic acid dimethyl ester with water to undergo a dimethyl ester hemihydrolysis reaction to obtain the dipropylmalonic acid monomethyl ester.

5. The detection method according to claim 1, characterized in that, The preparation method of the dipropylmalon monopropyl ester includes the following steps: mixing dipropylmalonate and 1-halopropane with a phase transfer catalyst to carry out a propylation reaction to obtain dipropylmalonate; and reacting the dipropylmalonate with water to undergo a dipropyl ester hemihydrolysis reaction to obtain the dipropylmalonate monopropyl ester.

6. The detection method according to claim 1, characterized in that, The method described can be used to remove at least one impurity from propylmalonic acid, 2-methyl-2-propylmalonic acid, 2-propyl-2-butylmalonic acid, monomethyl propylmalonic acid, 2-methyl-2-propylmalonic acid monomethyl ester, dimethyl propylmalonic acid monomethyl ester, 2-propyl-2-butylmalonic acid monomethyl ester, dimethyl propylmalonic acid, dipropylmalonic acid monopropyl ester, dimethyl propylmalonic acid, dimethyl propyl dipropylmalonic acid, and 2-propyl-2-butylmalonic acid dimethyl ester in the preparation of dipropylmalonic acid by the dimethyl propylmalonic acid method. This method can also be used to determine at least one impurity among propylmalonic acid, 2-methyl-2-propylmalonic acid, dipropylmalonic acid, 2-propyl-2-butylmalonic acid, propylmalonic acid monomethyl ester, 2-methyl-2-propylmalonic acid monomethyl ester, 2-propyl-2-butylmalonic acid monomethyl ester, dimethyl propylmalonic acid, dipropylmalonic acid monopropyl ester, dimethyl propylmalonic acid, dimethyl propylmalonic acid, propyl methyl propyl dipropylmalonic acid, and 2-propyl-2-butylmalonic acid dimethyl ester in dipropylmalonic acid monomethyl ester prepared by the dimethyl malonate method.

7. The detection method according to claim 1, characterized in that... The impurities in the dipropylmalonic acid monomethyl ester product or reaction solution are selected from one or more of propylmalonic acid, 2-methyl-2-propylmalonic acid, dipropylmalonic acid, 2-propyl-2-butylmalonic acid, propylmalonic acid monomethyl ester, 2-methyl-2-propylmalonic acid monomethyl ester, 2-propyl-2-butylmalonic acid monomethyl ester, dipropylmalonic acid dimethyl ester, dipropylmalonic acid monopropyl ester, dipropylmalonic acid dimethyl ester, dipropylmalonic acid methyl ester propyl ester, and 2-propyl-2-butylmalonic acid dimethyl ester.

8. The detection method according to claim 1, characterized in that... The impurities in the dipropylmalonic acid product or reaction solution are selected from one or more of propylmalonic acid, 2-methyl-2-propylmalonic acid, dipropylmalonic acid, 2-propyl-2-butylmalonic acid, monomethyl propylmalonic acid, monomethyl 2-methyl-2-propylmalonic acid, monomethyl 2-propyl-2-butylmalonic acid, dimethyl propylmalonic acid, monopropyl dipropylmalonic acid, dimethyl propyl propyl dipropylmalonic acid, dimethyl propyl dipropylmalonic acid, and dimethyl 2-propyl-2-butylmalonic acid.

9. The detection method according to claim 1, characterized in that... The impurities in the dipropylmalonic acid monomethyl ester product or reaction solution are selected from one or more of propylmalonic acid monomethyl ester, 2-methyl-2-propylmalonic acid monomethyl ester, 2-propyl-2-butylmalonic acid monomethyl ester and dipropylmalonic acid monopropyl ester.

10. The detection method according to claim 1, characterized in that... 2-Ethyl-2-propylmalonic acid, monoethyl dipropylmalonic acid, and diethyl dipropylmalonic acid were not detected in the dipropylmalonic acid product or reaction solution prepared by the dimethyl malonate method.

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