Method for resolving phenylalanine derivative, and intermediate

Abstract

A method for resolving a phenylalanine derivative of formula (I), and an intermediate. The method comprises: a resolving step comprising using a resolving reagent to react with the phenylalanine derivative represented by formula (I) in a reaction solvent to obtain a resolved intermediate, wherein the resolving reagent is selected from N-acetyl-D-phenylalanine and / or (2R,3R)-(-)-dibenzoyl-L-tartaric acid, and the reaction solvent is selected from 90-99% aqueous ethanol, absolute ethyl alcohol, or acetone. The method uses a chiral reagent to perform salt formation and racemate resolution, and has the advantages of being easy to operate, requiring no special production devices, and being easy to scale up production.

Description

Separation methods and intermediates of phenylalanine derivatives Technical Field

[0001] The present invention relates to the field of medicine, and in particular to a method for splitting phenylalanine derivatives and intermediates. Background Art

[0002] Boron neutron capture therapy (BNCT) is an effective treatment for tumors. In BNCT, BPA (4-dihydroxyborylphenylalanine or 4-boron-L-phenylalanine) is often used as a treatment. BPA is transported by the neutral amino acid transporter, the L-amino acid transporter system (LAT-1), so only the L-form (s-form) of BPA can be used in BNCT.

[0003] To monitor the distribution of BPA in patients, a radioactive 18F atom replaces a hydrogen atom on the benzene ring of the L-BPA molecule, forming 18F-BPA. The synthesis of 18F-BPA requires the use of an F-BPA precursor produced in accordance with Good Manufacturing Practice (GMP) requirements. Phenylalanine derivatives (such as, but not limited to, tert-butyl (2S)-2-amino-3-(2,4-dibromophenyl)propionate) are key intermediates required for the production of 18F-BPA precursors. This intermediate compound can also serve as an intermediate in the synthesis of boron compounds used in BNCT treatment, such as BPA, 2-fluoro-4-boronic acid-L-phenylalanine, and 2,4-diboronic acid-L-phenylalanine, showing broad potential for application.

[0004] Existing technologies for producing these synthetic intermediates often use SFC separation technology to resolve racemates. This technology suffers from high equipment costs, small production scales, and poor GMP compliance. Furthermore, due to the tert-butyl ester structure of this product, the success rate of selective asymmetric decomposition using enzymes is extremely low. Therefore, there is a need for a chemical resolution method for phenylalanine derivatives that is stable, simple to operate, and easily scalable.

[0005] Summary of the Invention

[0006] One object of the present invention is to provide a method for chiral separation of phenylalanine derivatives;

[0007] Another object of the present invention is to provide an intermediate obtained by the chiral resolution method.

[0008] To achieve the above-mentioned purpose, on the one hand, the present invention provides a method for chiral resolution of phenylalanine derivatives represented by formula (I),

[0009] X is selected from Br, I, F, Cl, CN, SCN or OCN;

[0010] R 1 、R 2 are each independently selected from: hydrogen or tert-butyloxycarbonyl;

[0011] R 3 selected from tert-butyl;

[0012] n = 1 or 2;

[0013] The method includes a resolution step comprising reacting a resolution reagent with a phenylalanine derivative represented by formula (I) in a reaction solvent to obtain a resolution intermediate. The resolution reagent is selected from N-acetyl-D-phenylalanine and / or (2R,3R)-(-)-diphenylformyl-L-tartaric acid. The reaction solvent is selected from 90-99% aqueous ethanol, anhydrous ethanol, or acetone.

[0014] Furthermore, the 90-99% ethanol aqueous solution can be selected from 90% ethanol aqueous solution, 92% ethanol aqueous solution, 94% ethanol aqueous solution, 95% ethanol aqueous solution, 96% ethanol aqueous solution, 98% ethanol aqueous solution or 99% ethanol aqueous solution.

[0015] In the present invention, the phenylalanine derivative represented by formula (I) is a racemate. The method of the present invention can effectively perform chiral resolution on the racemate of the phenylalanine derivative to obtain a phenylalanine derivative having a single configuration with high optical purity.

[0016] According to some specific embodiments of the present invention, the resolution step of the method comprises: reacting a resolution reagent with a phenylalanine derivative represented by formula (I) in a reaction solvent, crystallizing the reaction system at 10-30° C., and then filtering to obtain a resolution intermediate. In this case, the product obtained after precipitation and filtration mainly contains an S-configuration phenylalanine derivative salt. Recrystallization can further effectively remove the R-configuration phenylalanine derivative salt in the resolution intermediate.

[0017] According to some specific embodiments of the present invention, the method comprises stirring the reaction system at 10-30° C. for 10-25 hours to crystallize, and then filtering to obtain the resolved intermediate.

[0018] According to some specific embodiments of the present invention, the ee value of the compound represented by formula (II) in the resolved intermediate is greater than 35%.

[0019] A is a resolving agent.

[0020] According to some specific embodiments of the present invention, the compound represented by formula (II) is selected from the compound represented by formula (II-1) or formula (II-2):

[0021] According to some specific embodiments of the present invention, the ee value of the compound represented by formula (II) in the split intermediate is 36%-98%. For example, the ee value of the compound represented by formula (II) in the split intermediate can be 36%, 38%, 40%, 45%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97% or 98%.

[0022] The compound represented by formula (II) is a phenylalanine derivative salt with S configuration (ie, a salt obtained by reacting the phenylalanine derivative of formula (I) with a resolving agent).

[0023] According to some specific embodiments of the present invention, the reaction of the resolving agent with the phenylalanine derivative represented by formula (I) comprises reacting the resolving agent with the phenylalanine derivative represented by formula (I) at 30° C. to 55° C. to obtain a resolving intermediate.

[0024] According to some specific embodiments of the present invention, the reaction of the resolving agent with the phenylalanine derivative represented by formula (I) includes reacting the resolving agent with the phenylalanine derivative represented by formula (I) at 30°C to 55°C for 2-5h to obtain a resolving intermediate.

[0025] In the present invention, the resolution intermediate is a salt formed by a phenylalanine derivative represented by formula (I) and a resolution agent. Phenylalanine derivatives contain amino basic groups and readily react with acidic chiral resolution agents to form salts of phenylalanine derivatives. The chiral resolution agent can be removed by hydrolysis of the resolution intermediate.

[0026] According to some specific embodiments of the present invention, the resolution intermediate includes a phenylalanine derivative salt. Further, the resolution intermediate prepared by the method of the present invention includes a phenylalanine derivative salt with an S configuration and high optical purity.

[0027] According to some specific embodiments of the present invention, the reaction of the resolving agent with the phenylalanine derivative represented by formula (I) includes reacting the resolving agent with the phenylalanine derivative represented by formula (I) in a reaction solvent; the reaction solvent is 90-99% ethanol aqueous solution, and the resolving agent is N-acetyl-D-phenylalanine.

[0028] According to some specific embodiments of the present invention, the reaction of the resolving agent with the phenylalanine derivative represented by formula (I) includes reacting the resolving agent with the phenylalanine derivative represented by formula (I) in a reaction solvent; the reaction solvent is acetone, and the resolving agent is (2R, 3R)-(-)-diphenylformyl-L-tartaric acid.

[0029] According to some specific embodiments of the present invention, the molar ratio of the phenylalanine derivative represented by formula (I) to the resolving agent is 1:0.4-1.0. Further, the molar ratio of the phenylalanine derivative represented by formula (I) to the resolving agent is 1:0.5-0.8.

[0030] According to some specific embodiments of the present invention, the molar ratio of the phenylalanine derivative represented by formula (I) to the resolving agent is 1:0.6.

[0031] According to some specific embodiments of the present invention, the volume (mL) of the reaction solvent is 10 to 35 times the mass (g) of the phenylalanine derivative shown in formula (I). For example, the volume (mL) of the reaction solvent can be 10 times, 12 times, 15 times, 18 times, 20 times, 22 times, 25 times, 30 times, 32 times or 35 times the mass (g) of the phenylalanine derivative shown in formula (I). In other words, the volume-to-mass ratio (mL / g) of the reaction solvent to the phenylalanine derivative shown in formula (I) is 10 to 35.

[0032] According to some specific embodiments of the present invention, the mass of the phenylalanine derivative represented by formula (I) input into the splitting step is 30 mg to 50 g. For example, the mass of the phenylalanine derivative can be 30 mg, 50 mg, 100 mg, 200 mg, 300 mg, 500 mg, 1 g, 2 g, 5 g, 10 g, 20 g, 40 g, or 50 g. The splitting method of the present invention can be applicable to large-scale production.

[0033] According to some specific embodiments of the present invention, the method further comprises: subjecting the product obtained in the resolution step (resolution intermediate) to at least one recrystallization step in a recrystallization solvent to obtain a recrystallized resolution intermediate. In the present invention, after the recrystallization treatment, the optical purity of the S-configuration phenylalanine derivative salt can be further improved.

[0034] According to some specific embodiments of the present invention, the recrystallization comprises stirring the product obtained in the resolution step in a recrystallization solvent at 45-55°C for 1.5-2.5 hours, and then stirring at 15-25°C for 14-20 hours to obtain a recrystallized resolution intermediate.

[0035] According to some specific embodiments of the present invention, the HPLC content of the S-configuration phenylalanine derivative salt (the salt formed by the phenylalanine derivative and the resolving agent) in the recrystallized resolution intermediate is not less than 99%.

[0036] According to some specific embodiments of the present invention, the recrystallization comprises mixing the resolved intermediate with a recrystallization solvent to obtain a suspension, heating the suspension to 45-55° C. within 20-40 minutes, stirring for 1.5-2.5 hours, then cooling to 15-25° C. at a rate of 4-6° C. / h, and stirring for 14-20 hours to obtain a recrystallized resolved intermediate.

[0037] According to some specific embodiments of the present invention, the recrystallization solvent is selected from at least one of anhydrous ethanol, tetrahydrofuran, acetonitrile, acetone and 90-99% ethanol aqueous solution.

[0038] According to some specific embodiments of the present invention, wherein, the volume (mL) of the recrystallization solvent is 9 to 15 times the mass (g) of the resolved intermediate. Further, the volume (mL) of the recrystallization solvent can be 9 times, 10 times, 11 times, 12 times, 13 times, 14 times or 15 times the mass (g) of the resolved intermediate. In other words, the volume-to-mass ratio (mL / g) of the recrystallization solvent to the resolved intermediate is 9 to 15.

[0039] According to some specific embodiments of the present invention, the recrystallization further comprises filtering the precipitated crystals after the stirring is completed to obtain a filter cake.

[0040] Furthermore, the filter cake obtained after recrystallization is dried under vacuum at 50±5° C. to obtain a product. At this time, the optical purity of the S-configuration phenylalanine derivative salt in the product is not less than 99%.

[0041] According to some specific embodiments of the present invention, the method further comprises the step of hydrolyzing the resolution intermediate obtained in the step of reacting with the resolution agent or the resolution intermediate that has been recrystallized.

[0042] According to some specific embodiments of the present invention, the phenylalanine derivatives of formula (III) obtained by hydrolysis are In formula (III), X is independently selected from Br, I, F, Cl, CN, SCN or OCN; R 1 、R 2 are each independently selected from: hydrogen or tert-butyloxycarbonyl; R 3 Selected from tert-butyl; n=1 or 2.

[0043] In the present invention, the phenylalanine derivative of formula (III) is an S-configuration phenylalanine derivative.

[0044] According to some specific embodiments of the present invention, the phenylalanine derivative obtained by hydrolysis is selected from the following structures:

[0045] In formula (IIIa) and formula (IIIb), X is independently selected from Br, I, F, Cl, CN, SCN or OCN; R 1 、R 2 are each independently selected from: hydrogen or tert-butyloxycarbonyl; R 3 Selected from tert-butyl.

[0046] The hydrolysis can be carried out according to conventional hydrolysis methods in the art. According to some specific embodiments of the present invention, the method comprises hydrolyzing the split intermediate obtained in the split reaction step or the recrystallized split intermediate under alkaline conditions.

[0047] According to some specific embodiments of the present invention, the pH value of the alkaline condition is 7-14.

[0048] According to some specific embodiments of the present invention, the alkaline condition is in the presence of a base. Further, the base is selected from but not limited to at least one of metal hydroxides, metal carbonates, metal bicarbonates, and ammonia water.

[0049] According to some specific embodiments of the present invention, the base is selected from a mixture of one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, and ammonia water.

[0050] According to some specific embodiments of the present invention, the reaction temperature of the hydrolysis is 0-100°C; preferably 10-80°C; more preferably 15-60°C; most preferably 20-40°C.

[0051] According to some specific embodiments of the present invention, the reaction time of the hydrolysis is 5 min-2 h; preferably 10 min-1.5 h; more preferably 20 min-1 h.

[0052] According to some specific embodiments of the present invention, the reaction solvent for the hydrolysis is selected from a mixture of one or more of 95% ethanol aqueous solution, anhydrous ethanol, water or acetone.

[0053] According to some specific embodiments of the present invention, the phenylalanine derivative is selected from the following structures:

[0054] X is independently selected from Br, I, F, Cl, CN, SCN or OCN;

[0055] R 1 、R 2are each independently selected from: hydrogen or tert-butyloxycarbonyl;

[0056] R 3 Selected from tert-butyl.

[0057] According to some specific embodiments of the present invention, X is independently selected from Br, I, F, and Cl.

[0058] According to some specific embodiments of the present invention, the phenylalanine derivative is selected from but not limited to one of the following structures:

[0059] The present invention takes tert-butyl 2-amino-3-(2,4-dibromophenyl) propionate as an example, and its separation method is described in detail as follows:

[0060] An appropriate amount of tert-butyl 2-amino-3-(2,4-dibromophenyl)propionate and 10-30V of a reaction solvent are sequentially added to a reaction vessel to dissolve the mixture, and a resolving agent is added to obtain a suspension. The suspension is stirred at 30°C to 55°C for 2-5 hours, cooled to 20°C, and maintained for 10-20 hours to precipitate crystals, which are then filtered to obtain a crude product. The crude product is placed in a reaction vessel, and 12±2V of acetone is added at room temperature to obtain a suspension. The suspension is heated to 50±5°C within half an hour, maintained at this temperature and stirred for 2±0.5 hours. The suspension is cooled to 20±5°C at a rate of 5±1°C / h, maintained and stirred for about 17±3 hours, and crystals, i.e., the recrystallized product, are precipitated, with some impurities removed. The suspension is then filtered at room temperature. The filter cake is vacuum dried at 50±5°C to obtain chiral acid salt of tert-butyl (2S)-2-amino-3-(2,4-dibromophenyl)propionate. The obtained chiral acid salt can be neutralized with a base until the pH value of the reaction solution reaches 7-14, and (2S)-2-amino-3-(2,4-dibromophenyl)propionic acid tert-butyl ester is released and filtered out. (2S)-2-amino-3-(2,4-dibromophenyl)propionic acid tert-butyl ester:

[0061] The tert-butyl 2-amino-3-(2,4-dibromophenyl) propionate is prepared by the following method:

[0062] 1. Synthesis of tert-butyl 2-amino-3-(2,4-dibromophenyl) propionate

[0063] Dissolve N-benzylidene-glycine tert-butyl ester (40 g, 135.42 mmol, 1 eq), 1,4-dibromobenzyl bromide (44.53 g, 135.42 mmol, 1 eq), and tetrabutylammonium bromide (436.55 mg, 1.35 mmol, 0.01 eq) in 300 mL of toluene. Add 80 mL of potassium hydroxide (100 g, 1.78 mol, 13.16 eq) in water. Stir at 25°C for 12 hours until the reaction is complete. Allow to stand and separate, discard the aqueous phase, and retain the organic phase. Concentrate the organic phase at 55-60°C until no distillation occurs. Add acetonitrile (6 v) and heat to 50-55°C to dissolve. Slowly decrease the temperature (10-15°C per hour) to 0-5°C for crystallization. The mixture was stirred at 0-5°C for 1-2 hours, filtered, and the filter cake was rinsed with 0-5°C acetonitrile (1v), the mother liquor was discarded, and the filter cake was dried in a forced air drying oven at 45-50°C to obtain N-dibenzylidene-2,4-dibromophenylalanine tert-butyl ester.

[0064] Add tert-butyl N-benzylidene-2,4-dibromophenylalaninate and tetrahydrofuran (3v) to a 50.00ml four-necked flask. Add a mixed solution of citric acid (4.00eq.) and water (3v) dropwise. Stir for 20 hours, then concentrate the reaction mixture at 45-55°C until no distillation occurs. Add ethyl acrylate (5v) and water (5v), stir for 0.5 hours, separate the layers, and retain the aqueous phase. Extract the organic phase twice with water (3.5v). Combine the aqueous phases and extract the aqueous phase twice with EA (1.5v). Add EA (5v) to the aqueous phase and stir. Adjust the pH to 8-9 with sodium carbonate. The organic phase was washed once with saturated sodium chloride solution (5v), and the organic phase was concentrated at 45-55°C until no distillation occurred to obtain tert-butyl 2-amino-3-(2,4-dibromophenyl)propionate as an oil (51.87 g, purity: 98.0%, yield: 70.5%).

[0065] On the other hand, the present invention also provides an intermediate represented by formula (II),

[0066] wherein X is selected from Br, I, F, Cl, CN, SCN or OCN;

[0067] R 1 、R 2 are each independently selected from: hydrogen or tert-butyloxycarbonyl;

[0068] R 3 selected from tert-butyl;

[0069] n = 1 or 2;

[0070] A is a resolving agent.

[0071] Furthermore, A is independently selected from N-acetyl-D-phenylalanine or (2R,3R)-(-)-diphenylformyl-L-tartaric acid.

[0072] According to some specific embodiments of the present invention, the compound represented by formula (II) is selected from the compound represented by formula (II-1) or formula (II-2):

[0073] According to some specific embodiments of the present invention, the intermediate comprises one of the following structures:

[0074] According to some specific embodiments of the present invention, X is independently selected from Br, I, F, and Cl.

[0075] The intermediate represented by formula (II) can be prepared by the chiral resolution method of the present invention.

[0076] The phenylalanine derivatives of formula (III) can be prepared by the chiral resolution method of the present invention.

[0077] The intermediate represented by formula (II) can be used to prepare the phenylalanine derivatives represented by formula (III) of the present invention.

[0078] The intermediate represented by formula (II) and / or the phenylalanine derivative represented by formula (III) of the present invention can be used as a synthetic intermediate for preparing boron compounds that can be used for BNCT treatment, such as 4-borono-L-phenylalanine (BPA), 2-fluoro-4-boronic acid-L-phenylalanine (F-BPA) and 2,4-diboronic acid-L-phenylalanine, and has very broad application potential.

[0079] In summary, the present invention provides a method for resolving phenylalanine derivatives and intermediates thereof. The technical solution of the present invention has the following advantages:

[0080] The present invention uses a chiral reagent to perform salt formation and resolution of the racemate, which has the advantages of simple operation, no need for special production equipment, and easy expansion of production scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 is a chromatogram of structure identification example 1;

[0082] FIG2 is a chromatogram of structure identification example 2. DETAILED DESCRIPTION

[0083] The following describes in detail the implementation process of the present invention and the beneficial effects produced by specific embodiments, which is intended to help readers better understand the essence and characteristics of the present invention and is not intended to limit the scope of implementation of this case.

[0084] Chromatographic conditions for the ee value test in the embodiment of the present invention are as follows: chromatographic column: DAICEL CHIRALPAK ZWIX (250 mm*4 mm, 3 μm); mobile phase [water (50 mM formic acid + 25 mM diethylamine): methanol: tetrahydrofuran = 2:38:60)]; flow rate: 0.5 ml / min; detection wavelength: 210 nm; column temperature: 40°C.

[0085] Example 1

[0086] To the reaction vessel, 30 mg of tert-butyl 2-amino-3-(2,4-dibromophenyl) propionate was added in sequence, and anhydrous ethanol (16 v, the volume of anhydrous ethanol is 16 times the mass of tert-butyl 2-amino-3-(2,4-dibromophenyl) propionate) was added and stirred to dissolve; N-acetyl-D-phenylalanine (0.6 eq) was added and stirred at 40 ° C for 5 h. After the reaction was completed, the mixture was cooled to 10 ° C to precipitate crystals, filtered and vacuum dried. The ee value of the tested sample was 36.8%.

[0087] Example 2:

[0088] The difference between this embodiment and embodiment 1 is that embodiment 1 uses anhydrous ethanol as a solvent, while this embodiment uses acetone as a solvent, and the ee value of the obtained sample is 48.2%.

[0089] Example 3:

[0090] The difference between this embodiment and embodiment 1 is that embodiment 1 uses anhydrous ethanol (16v) as a solvent, while this embodiment uses a 95% ethanol aqueous solution (20v) as a solvent, and the ee value of the obtained sample is 86.2%.

[0091] Example 4:

[0092] Recrystallization: Take the sample of Example 3 and place it in a reaction vessel; add 95% ethanol aqueous solution (10v) at room temperature to obtain a suspension; raise the temperature to 50°C within half an hour, maintain it at 50°C and stir for two hours; cool it to 20°C at 5°C / h and keep stirring overnight; filter it with suction at room temperature, and dry the filter cake in vacuum at 50°C. The ee value of the sample is tested: 94.6%.

[0093] The recrystallized product was subjected to a hydrolysis reaction at a pH of 10-11, and the product was liberated and filtered to obtain tert-butyl (2S)-2-amino-3-(2,4-dibromophenyl) propionate.

[0094] Example 5:

[0095] The difference between this embodiment and embodiment 4 is that, while embodiment 4 uses 95% ethanol aqueous solution (10v) as the recrystallization solvent, this embodiment uses acetone (10v) as the recrystallization solvent, and the ee value of the obtained sample is 93.6%.

[0096] The recrystallized product is subjected to a hydrolysis reaction at a pH of 7-8, and is liberated and filtered to obtain tert-butyl (2S)-2-amino-3-(2,4-dibromophenyl) propionate.

[0097] Example 6:

[0098] The difference between this example and Example 4 is that Example 4 uses 95% ethanol aqueous solution (10v) as the recrystallization solvent, while this example uses acetonitrile (10v) as the recrystallization solvent, and the ee value of the obtained sample is 87.2%.

[0099] The recrystallized product was subjected to a hydrolysis reaction at a pH of 10-11, and the product was liberated and filtered to obtain tert-butyl (2S)-2-amino-3-(2,4-dibromophenyl) propionate.

[0100] Example 7:

[0101] The difference between this example and Example 4 is that Example 4 uses 95% ethanol aqueous solution (10v) as the recrystallization solvent, while this example uses tetrahydrofuran (10v) as the recrystallization solvent, and the ee value of the obtained sample is 93.6%.

[0102] The recrystallized product was subjected to a hydrolysis reaction at a pH of 12-13, and the product was liberated and filtered to obtain tert-butyl (2S)-2-amino-3-(2,4-dibromophenyl) propionate.

[0103] Example 8:

[0104] The difference between this embodiment and embodiment 4 is that, while embodiment 4 uses 95% ethanol aqueous solution (10v) as the recrystallization solvent, this embodiment uses anhydrous ethanol as the recrystallization solvent, and the ee value of the obtained sample is 96.2%.

[0105] The recrystallized product is subjected to a hydrolysis reaction at a pH of 9-10, and is liberated and filtered to obtain tert-butyl (2S)-2-amino-3-(2,4-dibromophenyl) propionate.

[0106] Example 9:

[0107] To the reaction vessel, 30 mg of tert-butyl 2-amino-3-(2,4-dibromophenyl)propionate was added in sequence, and acetone (27 v) was added and stirred to dissolve; (2R, 3R)-(-)-diphenylformyl-L-tartaric acid (0.6 eq) was added and stirred at 40 ° C for 5 h. After the reaction was completed, the mixture was cooled to 10 ° C to precipitate crystals, which were filtered and vacuum dried to obtain a sample.

[0108] Recrystallization: Weigh the above sample and place it in a reaction vessel; add tetrahydrofuran (10v) at room temperature to obtain a suspension; raise the temperature to 50°C within half an hour and maintain stirring at 50°C for two hours; cool to 20°C at a rate of 5°C / h and maintain stirring overnight; filter with suction at room temperature and dry the filter cake in vacuum at 50°C. The ee value of the obtained sample is 78.2%.

[0109] The recrystallized product was subjected to a hydrolysis reaction at a pH of 10-11, and the product was liberated and filtered to obtain tert-butyl (2S)-2-amino-3-(2,4-dibromophenyl) propionate.

[0110] Example 10:

[0111] Weigh approximately 600 mg of tert-butyl 2-amino-3-(2,4-dibromophenyl)propionate into a 20 ml glass bottle. Add 19.2 ml of acetone at room temperature and stir to obtain a clear solution. Add 0.6 eq of (2R,3R)-(-)-diphenylformyl-L-tartaric acid to the glass bottle to obtain a suspension. Raise the temperature to 50°C within half an hour and maintain stirring at 50°C for two hours. Cool the mixture to 20°C at a rate of 5°C / hour and maintain stirring for approximately 23 hours. Filter the mixture at room temperature and dry the filter cake in a vacuum oven at 50°C. (EE value: 80.36%, yield: 39.15%).

[0112] Recrystallization: Weigh the sample into a reaction flask and add 12V acetone at room temperature to obtain a suspension. Raise the temperature to 50°C within half an hour and maintain stirring at 50°C for two hours. Cool the mixture to 20°C at a rate of 5°C / hour and maintain stirring for approximately 17 hours. Centrifuge the mixture and dry the filter cake under vacuum. (EE value: 96.94%, yield: 92.03%)

[0113] The recrystallized product was subjected to a hydrolysis reaction at a pH of 10-11, and the product was liberated and filtered to obtain tert-butyl (2S)-2-amino-3-(2,4-dibromophenyl) propionate.

[0114] Example 11:

[0115] Weigh approximately 10 g of tert-butyl 2-amino-3-(2,4-dibromophenyl)propionate and place it in a 1 L jacketed reactor; add 320 ml of acetone at room temperature and stir to obtain a clear solution; weigh 0.6 equivalents of (2R,3R)-(-)-diphenylformyl-L-tartaric acid, dissolve it in a solvent, and add it to the jacketed reactor to obtain a suspension; raise the temperature to 50°C within half an hour, maintain stirring at 50°C for two hours; cool to 20°C at 5°C / h, maintain stirring for approximately 17 hours; filter with suction at room temperature, and dry the filter cake in vacuum at 50°C for approximately 6 hours (ee value: 93.36%, yield: 39.57%).

[0116] Recrystallization: Weigh approximately 3 g of the product and place it in a 50 mL jacketed reactor; add 36 mL of acetone at room temperature to obtain a suspension; heat to 50°C within half an hour and maintain stirring at 50°C for two hours; cool the system to 20°C at a rate of 5°C / h and maintain stirring for approximately 17 hours; filter with suction at room temperature and dry the filter cake in a vacuum at 50°C (ee value: 97.9%).

[0117] The recrystallized product was subjected to a hydrolysis reaction at a pH of 10-11, and the product was liberated and filtered to obtain tert-butyl (2S)-2-amino-3-(2,4-dibromophenyl) propionate.

[0118] Example 12:

[0119] Weigh approximately 50 g of tert-butyl 2-amino-3-(2,4-dibromophenyl)propionate and place it in a 5 L jacketed reactor; add 1600 ml of acetone at room temperature and stir to obtain a clear solution; weigh 0.6 equivalents of (2R,3R)-(-)-diphenylformyl-L-tartaric acid, dissolve it in a solvent, and add it to the jacketed reactor to obtain a suspension; heat it to 50°C within half an hour, maintain it at 50°C and stir for two hours; cool it to 20°C at a rate of 5°C / h and maintain stirring for about 20 hours; filter it with suction at room temperature, and dry the filter cake in vacuum at 50°C for about 10 hours (ee value: 90.52%, yield: 40.38%).

[0120] Recrystallization: Weigh approximately 15 g of the product and place it in a 250 mL jacketed reactor; add 225 mL of acetone at room temperature to obtain a suspension; heat to 50°C within half an hour and maintain stirring at 50°C for two hours; cool to 20°C at a rate of 5°C / h and maintain stirring for approximately 17 hours; filter with suction at room temperature and dry the filter cake in a vacuum at 50°C (ee value: 99.3%).

[0121] The recrystallized product was subjected to a hydrolysis reaction at a pH of 10-11, and the product was liberated and filtered to obtain tert-butyl (2S)-2-amino-3-(2,4-dibromophenyl) propionate.

[0122] Comparative Example 1:

[0123] To the reaction vessel, 1.0 g of tert-butyl 2-amino-3-(2,4-dibromophenyl)propionate and 8 ml of methyl tert-butyl ether were added in sequence; the mixture was stirred at 30-35°C for 12 h until the sample dissolved. 1.0 eq of (R)-(-)-mandelic acid (1.0 eq) was added and stirring was continued at 40-45°C for 2 h. The mixture was cooled to 10°C. The sample became suspended and was centrifuged for testing (ee: 0%).

[0124] Comparative Example 2:

[0125] To the reaction vessel, 1.0 g of tert-butyl 2-amino-3-(2,4-dibromophenyl)propionate and 12 ml of methyl tert-butyl ether-methanol solution (5:1) were added in sequence; after stirring until dissolved, 0.5 eq of D-tartaric acid was added and stirred at room temperature for 12 h until the sample dissolved. The sample was cooled to 10°C and became clear without crystal precipitation.

[0126] Comparative Example 3:

[0127] The difference between Comparative Example 3 and Example 1 is that Example 1 uses anhydrous ethanol as the solvent, while Comparative Example 3 uses acetonitrile as the solvent, and the ee value of the obtained sample is 6.0%.

[0128] Comparative Example 4:

[0129] The difference between Comparative Example 4 and Example 1 is that Example 1 uses N-acetyl-D-phenylalanine (0.6 eq) and anhydrous ethanol (16 v) as the resolving agent and solvent, respectively, while Comparative Example 4 uses L-camphorsulfonic acid (0.6 eq) as the resolving agent and acetone (5 v) as the solvent, and the ee value of the obtained sample is 6.2%.

[0130] Comparative Example 5:

[0131] The difference between Comparative Example 5 and Comparative Example 4 is that Comparative Example 4 uses acetone (5v) as the solvent, while Comparative Example 5 uses acetonitrile (29v) as the solvent, and the ee value of the obtained sample is 0%.

[0132] Comparative Example 6:

[0133] The difference between Comparative Example 6 and Comparative Example 4 is that Comparative Example 4 uses L-camphorsulfonic acid (0.6 eq) as a resolving agent, while Comparative Example 6 uses L-cysteine ​​(0.6 eq) as a resolving agent, and the ee value of the obtained sample is 16.8%.

[0134] Comparative Example 7:

[0135] The difference between Comparative Example 7 and Comparative Example 6 is that Comparative Example 6 uses acetone (5v) as the solvent, while Comparative Example 7 uses 95% ethanol aqueous solution (5v) as the solvent, and the ee value of the obtained sample is 0%.

[0136] Structural Identification Example 1

[0137] The sample prepared in Example 12 was tested according to the aforementioned ee value test conditions. The test results are shown in FIG1 and Table 1. FIG1 is a chromatogram, and Table 1 is a peak table of the chromatogram shown in FIG1.

[0138] Table 1

[0139] Referring to Figure 1 , the chromatographic peak of the S-configuration (i.e., IM3(S)) product is at 8.474 minutes, accounting for 99.65% (see Table 1); the chromatographic peak of the R-configuration (i.e., IM3(R)) product is at 9.465 minutes, accounting for only 0.35% (see Table 1). It can be seen that the method of the present invention can effectively separate the S-configuration.

[0140] Structural Identification Example 2

[0141] The product prepared in Example 8 of the present invention and ethyl acetate (5v) were added to a reaction vessel, and (Boc)2O (6.00eq.) and DMAP (0.01eq.) were added at 20-25°C. The mixture was stirred at 55-60°C for 6h. 2N aqueous ammonia (5v) was added and stirred for 12h. The mixture was separated into layers. Saturated ammonium chloride solution (5v) was added to the organic phase and stirred for 0.5h. The mixture was separated into layers. The organic phase was concentrated at 40-45°C until no distillation occurred, and n-heptane (1v) was added and distilled once. n-heptane (5v) was added and the mixture was cooled to 0-5°C, filtered, and the mother liquor was retained. 5% citric acid solution (5v) was added to the mother liquor, the mixture was cooled to 0-5°C, stirred for 0.5h, and allowed to stand for separation. The organic phase was concentrated at 85-90°C until no distillation occurred to obtain a light yellow solid. Ethyl acetate (10v) was added, the atmosphere was replaced with nitrogen once, and the mixture was stirred. Add AcOK (3.50 eq.) and B2Pin2 (2.50 eq.), replace the atmosphere with nitrogen once, and stir. Add Pd(dppf)Cl2 (0.10 eq.), replace the atmosphere with nitrogen three times. Stir at 75-78°C for 17 h. Cool to 20-25°C under nitrogen, pad the filter cake with celite, filter, and wash the filter cake once with EA (1 v), then discard. Filter the mother liquor under nitrogen, pad the filter cake with silica gel, and wash the filter cake once with EA (1 v), then discard. Add activated carbon (1.0X) and silica gel (1.0X) to the filtrate, heat to 55-60°C, and stir for 0.5 h. Cool to 20-25°C, filter, and discard the filter cake. Wash the mother liquor once with saturated ammonium chloride solution, and discard the aqueous phase. Concentrate the mother liquor at 50-55°C until no distillation occurs. Add n-heptane (2 v) and distill once. Add silica gel (3.0X) and n-heptane (5v) and concentrate until no distillation occurs. Filter through a pad of silica gel, retain the mother liquor, and discard the filter cake. Concentrate the mother liquor at 50-55°C until no distillation occurs. Add n-heptane (5v) to dissolve. Cool to -10-0°C for crystallization. Dry in an oven at 30-35°C for 12 hours to obtain a white solid, N,N-di(tert-butyloxycarbonyl)-2,4-di(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-(2S)-2-yl)-phenylalanine tert-butyl ester.

[0142] The obtained white solid (N,N-di(tert-butyloxycarbonyl)-2,4-di(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-(2S)-2-yl)-phenylalanine tert-butyl ester) and the N,N-di(tert-butyloxycarbonyl)-2,4-di(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-(2S)-2-yl)-phenylalanine tert-butyl ester reference substance [Batch No.: EW22935-28-P1(P2)-peak2-L; Source: Wuhan WuXi AppTec Pharmaceutical Development Co., Ltd.] were injected into a supercritical fluid chromatography according to the chromatographic conditions shown in Table 2. The chromatogram is shown in Figure 2.

[0143] Table 2

[0144] Referring to Figure 2 , the peak elution time of N,N-di(tert-butyloxycarbonyl)-2,4-di(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-(2S)-2-yl)-phenylalanine tert-butyl ester (see curve ② in Figure 2 ) obtained from (2S)-2-amino-3-(2,4-dibromophenyl)propanoate obtained by the resolution method of the present invention is consistent with that of the reference substance (see curve ① in Figure 2 ), and the reference substance is a commercially available S-configuration compound. This shows that the phenylalanine derivatives obtained by the resolution method of the present invention are of S-configuration. Obviously, the resolution intermediates and phenylalanine derivatives obtained by the method of the present invention are all of S-configuration, and the present invention can effectively separate products of S-configuration.

[0145] In summary, the resolution method of the present invention can not only effectively resolve the racemate and separate the required S configuration, but is also suitable for large-scale production with low cost and significant beneficial effects.

Claims

1. A method for chiral separation of phenylalanine derivatives represented by formula (I), X is selected from Br, I, F, Cl, CN, SCN or OCN; R 1 , R 2 Each independently selected from: hydrogen or tert-butyloxycarbonyl; R 3 Selected from tert-butyl; n = 1 or 2; in, The method comprises a splitting step: using a splitting reagent to react with a phenylalanine derivative shown in formula (I) in a reaction solvent to obtain a splitting intermediate; the splitting reagent is selected from N-acetyl-D-phenylalanine and / or (2R, 3R)-(-)-diphenylformyl-L-tartaric acid; and the reaction solvent is selected from 90-99% ethanol aqueous solution, anhydrous ethanol or acetone.

2. The chiral separation method according to claim 1, wherein: The splitting step comprises: using a splitting agent to react with the phenylalanine derivative shown in formula (I) in a reaction solvent, then crystallizing the reaction system at 10-30° C., filtering, and obtaining a split intermediate.

3. The chiral separation method according to claim 2, wherein: The method comprises stirring the reaction system at 10-30° C. for 10-25 hours to crystallize, and then filtering to obtain a resolved intermediate.

4. The chiral separation method according to claim 1, wherein: The ee value of the compound represented by formula (II) in the resolved intermediate is greater than 35% A is a resolving agent.

5. The chiral separation method according to claim 4, wherein: The compound represented by formula (II) is selected from the compounds represented by formula (II-1) or formula (II-2):

6. The chiral separation method according to claim 1, wherein: The reaction of the resolution agent with the phenylalanine derivative shown in formula (I) comprises reacting the resolution agent with the phenylalanine derivative shown in formula (I) at 30° C. to 55° C. to obtain a resolution intermediate.

7. The chiral separation method according to claim 1, wherein: The reaction solvent is 90-99% ethanol aqueous solution, and the resolution reagent is N-acetyl-D-phenylalanine; or, The reaction solvent is acetone, and the resolution reagent is (2R, 3R)-(-)-diphenylformyl-L-tartaric acid.

8. The chiral separation method according to claim 1, wherein: The molar ratio of the phenylalanine derivative represented by formula (I) to the resolution agent is 1:0.4-1.

0.

9. The chiral separation method according to claim 1, wherein: The volume (mL) of the reaction solvent is 10 to 35 times the mass (g) of the phenylalanine derivative.

10. The chiral separation method according to claim 1, wherein: The method further comprises: subjecting the obtained resolved intermediate to at least one recrystallization step in a recrystallization solvent.

11. The chiral separation method according to claim 10, wherein: The recrystallization comprises stirring the resolved intermediate obtained in the resolution step in a recrystallization solvent at 45-55° C. for 1.5-2.5 hours, and then stirring at 15-25° C. for 14-20 hours to obtain a recrystallized resolved intermediate.

12. The chiral separation method according to claim 10, wherein: The recrystallization comprises mixing the split intermediate with a recrystallization solvent to obtain a suspension, heating the suspension to 45-55° C. within 20-40 minutes, stirring for 1.5-2.5 hours, then cooling to 15-25° C. at a rate of 4-6° C. / h, stirring for 14-20 hours, and obtaining a recrystallized split intermediate.

13. The chiral separation method according to claim 10, wherein: The recrystallization solvent is at least one selected from anhydrous ethanol, tetrahydrofuran, acetonitrile, acetone and 90-99% ethanol aqueous solution; and / or The volume (mL) of the recrystallization solvent is 9 to 15 times the mass (g) of the resolved intermediate.

14. The chiral separation method according to claim 1, 10 or 11, wherein: The method further comprises the step of hydrolyzing the split intermediate obtained in the splitting step or the split intermediate after recrystallization, and obtaining the phenylalanine derivative of formula (III) through hydrolysis.

15. The chiral separation method according to claim 1, wherein: The mass of the phenylalanine derivative represented by formula (I) introduced into the separation step is 30mg-50g.

16. The chiral separation method according to claim 1, wherein: The phenylalanine derivatives are selected from the following structures: X is independently selected from Br, I, F, Cl, CN, SCN or OCN; R 1 , R 2 Each is independently selected from: hydrogen or tert-butyloxycarbonyl; R 3 Selected from tert-butyl.

17. The chiral separation method according to claim 1, wherein: The phenylalanine derivative is selected from one of the following structures:

18. The intermediate represented by formula (II) in, X is selected from Br, I, F, Cl, CN, SCN or OCN; R 1 , R 2 Each independently selected from: hydrogen or tert-butyloxycarbonyl; R 3 Selected from tert-butyl; n = 1 or 2; A is a resolving agent.

19. The intermediate according to claim 18, wherein A is independently selected from N-acetyl-D-phenylalanine or (2R,3R)-(-)-diphenylformyl-L-tartaric acid.

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