Method for preparing brivaracetam intermediate by chemical-enzyme method

Abstract

The invention discloses a method for preparing a brivaracetam intermediate I by a chemical-enzyme method. The method disclosed by the invention comprises the following steps: by taking n-butyraldehyde as a starting material, carrying out condensation and addition reaction on the n-butyraldehyde and malonic acid diester to generate a compound V, carrying out hydrolysis and decarboxylation on the compound V under an acidic condition to form a compound VI, then carrying out cyclization reaction on the compound VI and a nitrogen-containing reagent to generate a compound VII, then converting the compound VII into a compound VIII under the action of hydantoinase, and carrying out cyclization reaction on the compound VIII to generate a compound VIII. And finally, carrying out Hofmann degradation and ring closing reaction to obtain the brivaracetam intermediate I, wherein the chiral purity of the intermediate is greater than or equal to 99%. The route disclosed by the invention is simple to operate, high in atom economy, free of splitting and more suitable for industrial production.

Description

Technical field:

[0001] The invention belongs to the technical field of biocatalysis, and specifically relates to a method for preparing a brivaracetam intermediate by a chemical-enzymatic method. Background technology:

[0002] Brivaracetam is an anti-epileptic drug developed by UCB of Belgium, with a structure shown in Formula A. In February 2016, Brivaracetam was approved by the U.S. FDA for the treatment of partial-onset epilepsy in patients aged 16 years and above, and as an adjuvant treatment with or without secondary systemic seizures.

[0003]

[0004] UCB of Belgium disclosed a method for preparing Bu Wa Xi Tam in patent CN101263113B, as shown in Scheme 1. The method uses 2-hexenoic acid ethyl ester as the starting material, obtains racemic 4-n-propyl pyrrolidone through Macheal addition and hydrogenation ring closure, obtains optically pure (R)-4-n-propyl pyrrolidone through chiral chromatography, and then reacts with 2-bromobutyric acid methyl ester to obtain butyric acid methyl ester pyrrolidone, and finally obtains high-purity Bu Wa Xi Tam through aminolysis and chromatographic separation. This route uses heavy metal nickel, and no chiral center is constructed in the synthesis, and a chiral column is required for chromatographic preparation, and the production cost is extremely high.

[0005]

[0006]

[0007] Scheme 1

[0008] Through route Scheme 1, it was found that (R)-4-n-propylpyrrolidone (Compound I) is a key chiral intermediate for the synthesis of brivaracetam (CAS No.: 930123-37-8). Therefore, the preparation of Compound I has attracted industry attention and research.

[0009] Patent WO2020148731A1 discloses a method for preparing a key intermediate I, as shown in Scheme 2. This route uses 3-propyl-glutaric anhydride as the starting material, first reacts with phenylethylamine to introduce a chiral center, and then obtains the target intermediate through protection, rearrangement, hydrolysis, dehydration and ring closure reactions. This route uses highly toxic and explosive sodium azide, which makes the scale-up production operation difficult and risky, and is not suitable for industrial production.

[0010]

[0011] Scheme 2

[0012] Patent US10781170B1 discloses a new method for preparing a key intermediate I, as shown in Scheme 3. This method uses n-butyraldehyde and 2-cyanoacetamide as starting materials, and obtains the target intermediate I through reactions such as cyclization, hydrolysis, phenylethylamine splitting, chlorination, Hofmann rearrangement, and cyclization. In this route, the chirality of the target compound needs to be split by phenylethylamine, and the splitting step has a large material loss, a large amount of solvent, and cumbersome operation.

[0013]

[0014]

[0015] Scheme 3

[0016] In the prior art, the preparation method of brivaracetam intermediate I has low yield and high cost, and is not suitable for industrialization. Therefore, we need to develop a preparation method that is simple to operate, has cheap and readily available raw materials, high yield, and is suitable for industrialization. Summary of the invention:

[0017] The purpose of the present invention is to provide a method for preparing brivaracetam intermediate I by an efficient chemical-enzymatic method in view of the deficiencies in the prior art.

[0018] The technical solution adopted by the present invention is shown in Scheme 4.

[0019]

[0020] Wherein, R is selected from methyl, ethyl, and isopropyl.

[0021] Scheme 4

[0022] The invention provides a method for preparing a brivaracetam intermediate I, which comprises the following specific steps: taking n-butyraldehyde as a starting material, firstly performing a condensation reaction with a malonic acid diester to generate a compound IV, then performing an addition reaction with the malonic acid diester to obtain a compound V, hydrolyzing and decarboxylating the compound V under acidic conditions to form a compound VI, then performing a cyclization reaction with a nitrogen-containing reagent to generate a compound VII, then converting the compound VII into a compound VIII under the action of hydantoinase, performing a Hofmann degradation reaction with a halogen under alkaline conditions to generate a compound IX, and finally performing a self-cyclization of the compound IX in the presence of a catalyst to form a compound I.

[0023] Furthermore, in step 1, the molar ratio of n-butyraldehyde to malonate diester is 1:1 to 1:4, preferably 1:2.

[0024] Furthermore, the malonate diester is selected from dimethyl malonate, diethyl malonate, diisopropyl malonate, preferably diethyl malonate.

[0025] Furthermore, the reaction temperature of the condensation reaction in step 1 is 30-60°C.

[0026] Furthermore, in step 2, the molar ratio of compound IV to malonic acid diester is 1:1 to 1:2, preferably 1:1.

[0027] Furthermore, the reaction temperature of the addition reaction in step 2 is 40-70°C.

[0028] Furthermore, the addition reaction in step 2 requires the addition of a catalyst, which includes but is not limited to di-n-propylamine, diisopropylamine, triethylamine, diisopropylethylamine, titanium tetrachloride, preferably diisopropylamine.

[0029] Furthermore, the acid in step 3 is selected from hydrochloric acid, sulfuric acid, acetic acid, hydrofluoric acid, and hydrobromic acid, preferably hydrochloric acid.

[0030] Furthermore, the hydrolysis decarboxylation reaction temperature in step 3 is 40-70°C.

[0031] Furthermore, the nitrogen-containing reagent in step 4 is selected from urea, ammonia water, ammonia gas, ammonium carbonate, ammonium acetate, preferably urea.

[0032] Furthermore, the cyclization reaction in step 4 is carried out at 130-160° C., and the reaction time is 3-5 hours.

[0033] Furthermore, in step 5, the compound VII and hydantoinase are subjected to an enzymatic reaction in a buffer solution at a temperature of 20 to 60°C.

[0034] Furthermore, the hydantoinase in step 5 is derived from Bacillus stearothermophilus, Cycloclasticus sp., Burkholderia phytofirmans, Comamonas sp., Delftia acidovorans or homologs thereof, preferably Bacillus stearothermophilus.

[0035] Furthermore, the hydantoinase in step 5 participates in the catalytic reaction in the form of hydantoinase powder, hydantoinase solution, hydantoinase homogenate solution, cells containing hydantoinase, etc.

[0036] Furthermore, the cells containing hydantoinase are selected from genetically engineered Escherichia coli or yeast.

[0037] Furthermore, the concentration of the hydantoinase powder is 1-10 g / L or the concentration of the cells containing hydantoinase is 10-100 g / L.

[0038] Furthermore, the hydantoinase is selected from the hydantoinase D-Hase sold by Shangke Biopharmaceuticals (Shanghai) Co., Ltd.

[0039] Furthermore, the form of the halogen in step 6 is not particularly limited, and may be a halogen (chlorine, bromine, iodine) molecule, or a reagent capable of releasing halogen, or a reagent containing halogen in its molecule.

[0040] Furthermore, the halogen reagent includes but is not limited to Br2, NBS, NCS, sodium hypochlorite, sodium hypobromite, preferably Br2.

[0041] Furthermore, the alkaline reagent in step 6 is selected from NaOH, KOH, LiOH or a combination thereof.

[0042] Furthermore, the catalyst in step 7 is an acyl chloride reagent or a condensation agent.

[0043] Furthermore, the catalyst in step 7 includes but is not limited to DCC, EDCI, SOCl2, preferably DCC.

[0044] Furthermore, Compound I can be used to prepare Brivaracetam.

[0045] The beneficial effect of the present invention is that the present invention provides a method for preparing brivaracetam intermediate I by chemical-enzymatic method, wherein n-butyraldehyde is used as a starting material, firstly undergoes condensation and addition reaction with a malonic acid diester to generate compound V, then undergoes hydrolysis decarboxylation and cyclization reaction to obtain compound VII, then undergoes conversion into compound VIII under the action of hydantoinase, and finally undergoes Hofmann degradation and cyclization reaction to obtain compound I, with a chiral purity of ≥99%. The route is simple to operate, has high atom economy, does not require splitting, and is more suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 LC-MS chart of compound IVa of Example 1

[0047] Figure 2 LC-MS chart of Example 3 Compound Va

[0048] Figure 3 LC-MS chart of Example 5 Compound VI

[0049] Figure 4 LC-MS chart of Example 7 Compound VII

[0050] Figure 5 LC-MS chart of Example 8 Compound VIII

[0051] Figure 6LC-MS chart of Example 10 Compound IX DETAILED DESCRIPTION

[0052] The technical content of the present invention is further described below in conjunction with specific embodiments, the purpose of which is to provide a better understanding of the content of the present invention, but the protection scope of the present invention is not limited thereto.

[0053] Example 1 Preparation of Compound IVa

[0054]

[0055] Compound II (5 g, 0.07 mol, 1.0 eq), compound IIIa (22.6 g, 0.14 mol, 2.0 eq), morpholine (24.8 g, 0.28 mol, 4.0 eq), AcOH (2.5 g, 0.04 mol, 0.6 eq), and 50 mL of dichloromethane were added to a 100 mL single-mouth bottle. The temperature was raised to 48 ° C. The reaction was stirred for 16 hours and the reaction was completed. The reaction system was cooled to room temperature, 50 mL of H2O was added, the aqueous phase was extracted with dichloromethane, the organic phases were combined, and the mixture was concentrated under reduced pressure to obtain 9.5 g of crude compound IVa. The LC-MS spectrum is shown in FIG. Figure 1 , the crude product can be used directly in the next step.

[0056] Example 2 Preparation of Compound IVb

[0057]

[0058] In a 100 mL single-necked bottle, compound II (5 g, 0.07 mol, 1.0 eq), compound IIIb (27.3 g, 0.21 mol, 3.0 eq), morpholine (24.8 g, 0.28 mol, 4.0 eq), AcOH (2.5 g, 0.04 mol, 0.6 eq), and 50 mL of dichloromethane were added. The temperature was raised to 45 ° C. and the reaction was stirred for 16 hours until the reaction was completed. The reaction system was cooled to room temperature, 50 mL of H2O was added, the aqueous phase was extracted with dichloromethane, the organic phases were combined, and concentrated under reduced pressure to obtain 7.38 g of crude compound IVb, which was directly used in the next step.

[0059] Example 3 Preparation of Compound Va

[0060]

[0061] Compound IIIa (74.72 g, 0.47 mol, 1.0 eq), compound IVa (100 g, 0.47 mol, 1.0 eq), diisopropylamine (70.8 g, 0.70 mol, 1.5 eq) were added to a 1L single-mouth bottle, the temperature was raised to 58°C, stirred overnight, and the reaction was monitored by TLC to complete. After the reaction system was cooled to room temperature, ice water was added, and it was extracted three times with n-heptane. The organic layers were combined and concentrated under reduced pressure to obtain 112.5 g of crude compound Va. The LC-MS spectrum is shown in Figure 2 , the crude product can be used directly in the next step.

[0062] Example 4 Preparation of Compound Vb

[0063]

[0064] Add compound IIIb (61.6 g, 0.47 mol, 1.0 eq), compound IVb (87.9 g, 0.47 mol, 1.0 eq), diisopropylamine (70.8 g, 0.70 mol, 1.5 eq) to a 1L single-mouth bottle, heat to 58°C, stir overnight, and monitor the completion of the reaction by TLC. After cooling the reaction system to room temperature, add ice water, extract three times with n-heptane, combine the organic layers, and concentrate under reduced pressure to obtain 92.1 g of crude compound Vb, which is directly used in the next step.

[0065] Example 5 Preparation of Compound VI

[0066]

[0067] Compound Va (130 g, 0.35 mol, 1.0 eq), 10 mL of ethanol, and 20 mL of hydrochloric acid (6 N) were added to a 1 L single-mouth bottle, and the temperature was raised to 60 ° C. The reaction was stirred for 2 hours until the reaction was completed. The reaction system was cooled to 30 ° C. 450 mL of toluene was added, stirred for 30 minutes, and filtered with diatomaceous earth while hot. The separated toluene phase was washed three times with water and brine respectively. The organic phases were combined, dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain 35.5 g of compound VI. The reaction yield was 58.8%. The LC-MS spectrum is shown in Figure 3 .

[0068] Example 6 Preparation of Compound VI

[0069]

[0070] Compound Vb (110.3 g, 0.35 mol, 1.0 eq), 10 mL of ethanol, and 20 mL of hydrochloric acid (6N) were added to a 1 L single-mouth bottle, and the temperature was raised to 60 ° C. The reaction was stirred for 2 hours until the reaction was completed. The reaction system was cooled to 30 ° C. 450 mL of toluene was added. After stirring for 30 minutes, it was filtered with diatomaceous earth while hot. The separated toluene phase was washed three times with water and brine respectively. The organic phases were combined, dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain 33.2 g of compound VI. The reaction yield was 55%.

[0071] Example 7 Preparation of Compound VII

[0072]

[0073] Compound VI (35.5 g, 0.2 mol, 1.0 eq) and urea (30 g, 0.5 mol, 2.5 eq) were added to a 500 mL single-mouth bottle, the temperature was raised to 140 ° C, and the reaction was stirred for 4.5 hours. 120 mL of water was added to the system, and the stirring was continued for 15 minutes. The aqueous phase was then extracted three times with dichloromethane, and the organic phases were combined, dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain 26.2 g of compound VII. The reaction yield was 84.5%, and the product was a yellow solid. The LC-MS spectrum is shown in Figure 4 .

[0074] Example 8 Preparation of Compound VIII

[0075]

[0076] 4.8 g of compound VII and 7.2 g of hydantoin enzyme cells (D-Hase from Shangke Biopharmaceuticals (Shanghai) Co., Ltd.) were added to a 250 mL three-necked flask, phosphate buffer was added to adjust the pH to 7.98, and the reaction was carried out at 50 ° C for 48 hours. After TLC monitoring showed that the substrate disappeared, 4 volumes of acetonitrile were added to the reaction solution for oscillation inactivation, centrifuged for 3 minutes, and the reaction solution was filtered. Hydrochloric acid was added to the filtrate to adjust the pH to 1, and a large amount of solid was precipitated. The solid was filtered and dried in vacuo at 50 ° C to finally obtain 5.05 g of compound VIII, with a reaction yield of 97.3%, chiral purity> 98.7%, and LC-MS spectrum was shown in FIG. Figure 5 .

[0077] Example 9 Preparation of Compound VIII

[0078]

[0079] To a 250 mL three-necked flask, 5.4 g of compound VII and 8.0 g of hydantoinase powder (D-Hase, Shangke Biopharmaceutical (Shanghai) Co., Ltd.) were added, phosphate buffer was added to adjust the pH to 7.98, and the reaction was carried out at 50 ° C for 48 hours. After TLC monitoring showed that the substrate disappeared, 4 volumes of acetonitrile were added to the reaction solution for shaking inactivation, centrifuged for 3 minutes, and the reaction solution was filtered. Hydrochloric acid was added to the filtrate to adjust the pH to 1, a large amount of solid was precipitated, and the solid was filtered. The obtained solid was vacuum dried at 50 ° C to finally obtain 5.45 g of compound VIII, the reaction yield was 92.6%, and the chiral purity was >99.1%.

[0080] Example 10 Preparation of Compound IX

[0081]

[0082] Compound VIII (400 mg, 2.3 mmol, 1.0 eq) and NaOH aqueous solution (5 eq, 4 V / W) were added to a 100 mL three-necked flask, and the temperature was lowered to -5 to 5 °C. Br2 (478 mg, 2.99 mmol, 1.3 eq) was slowly added dropwise. After the addition was completed, stirring was continued for 10 minutes, and then the temperature was raised to 65 °C. After stirring for 30 minutes, the reaction was completed and cooled to room temperature. The methyl tert-butyl ether phase was discarded after extraction once with methyl tert-butyl ether. Concentrated hydrochloric acid was continued to be added to the reaction solution to adjust the pH to 5-6, and then concentrated under reduced pressure to obtain a crude product. The crude product was recrystallized from dichloromethane and methanol to precipitate a large amount of solids. The solids were filtered and dried in vacuo at 50 °C to finally obtain 322 mg of compound IX. The reaction yield was 96.5%, the chiral purity was >99.5%, and the LC-MS spectrum was shown in Figure 6 .

[0083] Example 11 Preparation of Compound I

[0084]

[0085] IX (360 mg, 2.48 mmol, 1.0 eq), 4.5 mL of dichloromethane and DCC (560 mg, 2.73 mmol, 1.1 eq) were added to a 100 mL three-necked flask and stirred for 3 to 4 hours. The reaction was completed after monitoring by TLC. 5 mL of water was added to the flask and stirred, and the organic phase was separated and concentrated under reduced pressure. The obtained solid was dried in vacuo at 50 ° C to finally obtain 252 mg of compound I with a reaction yield of 80% and a chiral purity of >99.5%.

Claims

1. The present invention discloses a method for preparing a brivaracetam intermediate I by a chemical-enzymatic method, characterized in that: The method uses compound VII as a starting material, converts it into compound VIII under the action of hydantoin, and compound VIII undergoes Hofmann degradation reaction to generate compound IX. Finally, compound IX generates brivaracetam intermediate I under the action of a catalyst.

2. The method according to claim 1, characterized in that The preparation method of compound VII is as follows: Wherein, R is selected from methyl, ethyl, and isopropyl.

3. The method according to claim 1, characterized in that The hydantoinase is derived from the hydantoinase D-Hase produced by Shangke Biopharmaceuticals (Shanghai) Co., Ltd.

4. The method according to claim 1, characterized in that The hydantoinase participates in the catalytic reaction in the form of hydantoinase powder, hydantoinase solution, hydantoinase homogenized solution, cells containing hydantoinase and the like.

5. The method according to claim 1, characterized in that The cells containing hydantoinase are selected from genetically engineered Escherichia coli or yeast.

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