A method for enantioselective extraction and resolution of racemic compounds by reverse micelles

Abstract

The present invention discloses a method for preparing chiral compounds by enantioselective reverse micelle extraction to resolve racemic compounds. In the resolution method, a chiral amino acid surfactant forms reverse micelles in a water-insoluble non-aqueous solvent, and enantiomers in the racemic compound in the aqueous phase are selectively extracted to separate the racemic compound. The method for preparing chiral compounds by enantioselective reverse micelle extraction to resolve racemic compounds has the characteristics of simple resolution process, convenient process operation, high enantioselectivity, reusable reverse micelles and low resolution cost, meets the requirements of large-scale resolution, and opens up a new way for chiral resolution.

Description

Technical Field

[0001] The present invention belongs to the technical field of chiral separation, and particularly relates to a method for preparing chiral compounds by enantioselective reverse micelle extraction for resolving racemates. Background Art

[0002] Although enantiomers of chiral drugs have the same chemical composition, differences in their spatial three-dimensional structures often lead to different biological activities, thereby affecting the physical and chemical properties, pharmacological activities, and drug metabolism of the drugs. So far, although there are many methods for preparing chiral drugs, the resolution of racemic drugs remains the main route for obtaining commercial chiral drugs.

[0003] Reverse micelles are thermodynamically stable, optically transparent, nanoscale systems formed by self-assembly of a certain concentration of surfactants dissolved in non-aqueous solvents. Among them, the hydrophilic "heads" face inward and contact the water pool, while the hydrophobic "tails" contact the surrounding hydrophobic solvents to maintain the thermodynamic equilibrium of the system. In the reverse micelle system, the internal "water pool" can dissolve biomolecules and prevent them from denaturing. Therefore, the reverse micelle extraction technology has been developed using the "water pool" characteristics of reverse micelles for the extraction and separation of proteins, enzymes, antibodies, and antibiotics. However, the existing reverse micelle extraction technology is only applicable to the extraction and separation of bioactive molecules and cannot be used for the resolution of racemic compounds.

[0004] The present invention discloses a method for enantioselective reverse micelle extraction for resolving racemic compounds, opening up a new way for the preparation of chiral drugs from racemic compounds. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing chiral compounds by enantioselective reverse micelle extraction for resolving racemates, which has the characteristics of simple resolution process, convenient process operation, high enantioselectivity, and low resolution cost, and meets the requirements of large-scale resolution of racemates for preparing chiral compounds.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] The method for enantioselective reverse micelle extraction for resolving racemic compounds uses reverse micelles formed by chiral surfactants in non-aqueous solvents as chiral recognition extractants to selectively recognize one enantiomer from the aqueous solution of racemates. The recognized enantiomer enters the reverse micelles, while the other unrecognized enantiomer remains in the aqueous phase. The separation of the reverse micelle phase and the aqueous phase realizes the resolution of racemic compounds.

[0008] In the above method for enantioselective reverse micelle extraction for resolving racemic compounds, the chiral surfactant has the following characteristics:

[0009] The chiral surfactant is an N-acyl-substituted chiral amino acid.

[0010] The N-acyl-substituted chiral amino acid, wherein the alkyl group is an octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, henicosyl, docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl, heptacosyl, octacosyl, nonacosyl, triacontyl, hentriacontyl, dotriacontyl, tritriacontyl, or tetratriacontyl group, each independently being a straight-chain or branched-chain group.

[0011] The N-acyl-substituted chiral amino acid, wherein the configuration of the amino acid is the L-configuration or the D-configuration.

[0012] The N-acyl-substituted chiral amino acid, wherein the amino acid is alanine, valine, leucine, isoleucine, proline, phenylalanine, tyrosine, tryptophan, serine, threonine, cysteine, methionine, histidine, lysine, arginine, aspartic acid, glutamic acid, asparagine, or glutamine, each independently.

[0013] In the method for enantioselective extraction and resolution of a racemic compound using reverse micelles, the non-aqueous solvent has the following characteristics:

[0014] The non-aqueous solvent is a single organic solvent that is sparingly soluble in water or a mixed organic solvent that is sparingly soluble in water, and is selected from one or a mixture of two or a mixture of three organic solvents such as hydrocarbons, halogenated hydrocarbons, alcohols, ethers, ketones, esters, etc. that are sparingly soluble in water.

[0015] The organic solvent that is sparingly soluble in water is selected from one or a mixture of two or a mixture of three solvents such as dichloromethane, chloroethane, dichloroethane, chloroform, carbon tetrachloride, n-pentane, isopentane, n-hexane, cyclohexane, n-heptane, isoheptane, n-octane, isooctane, n-pentanol, isopentanol, n-hexanol, isohexanol, n-heptanol, isoheptanol, n-octanol, isooctanol, cyclohexanol, propyl ether, butyl ether, pentyl ether, hexyl ether, cyclohexyl ether, phenyl ether, benzene, toluene, xylene, chlorobenzene, dichlorobenzene, butanone, pentanone, hexanone, cyclohexanone, ethyl formate, propyl formate, butyl formate, pentyl formate, hexyl formate, isooctyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, pentyl acetate, hexyl acetate, isooctyl acetate.

[0016] In the method for enantioselective extraction and resolution of a racemic compound using reverse micelles, the preparation method of the chiral surfactant is as follows:

[0017] Using malonate (S1) as a raw material, C-alkylation reaction with a halogenated hydrocarbon is carried out under alkali catalysis to obtain alkyl malonate (S2); S2 is hydrolyzed to obtain alkyl malonic acid (S3); S3 is decarboxylated at high temperature to obtain alkyl acid (S4); after S4 is acyl chlorinated, N-acylation reaction with a chiral amino acid is carried out to obtain N-alkanoyl-substituted chiral amino acid (S).

[0018] The present invention also provides an application of enantioselective reverse micelle extraction in resolving racemic compounds of amino alcohols.

[0019] In the application of the enantioselective reverse micelle extraction in resolving racemic compounds of amino alcohols, the racemic compounds of amino alcohols include: propranolol, alprenolol, oxprenolol, pindolol, nadolol, esmolol, metoprolol, practolol, atenolol, acebutolol, labetalol, carvedilol.

[0020] The enantioselective reverse micelle extraction for resolving racemic compounds of amino alcohols includes the following steps:

[0021] Prepare a reverse micelle solution of a chiral surfactant in a non-aqueous solvent and an aqueous solution of a racemic compound, mix the reverse micelle solution and the aqueous solution of the racemic compound, stir or shake to make the enantiomers in the racemic compound reach a distribution equilibrium between the reverse micelle phase and the aqueous phase, let it stand or centrifuge to separate the phases, and separate the reverse micelle phase and the aqueous phase to obtain the reverse micelle phase and the aqueous phase containing optically active enantiomers respectively.

[0022] For the reverse micelle phase and the aqueous phase separated by enantioselective reverse micelle extraction, conventional separation and purification methods can be used to further improve the optical purity, and the reverse micelle can be reused. Among them, after the reverse micelle phase is back-extracted with water, it is separated and purified by conventional methods such as concentration, crystallization, etc., and an enantiomer of amino alcohol can be obtained, and the reverse micelle can be reused; the aqueous phase is directly separated and purified by conventional methods such as concentration, crystallization, etc., and another enantiomer of amino alcohol can be obtained.

[0023] Compared with the prior art, the beneficial technical effects obtained by the present invention are as follows:

[0024] (1) The chiral polar group in the chiral surfactant has a molecular recognition effect on one enantiomer in the racemate, and can selectively bring this enantiomer into the reverse micelle phase, while the other enantiomer not recognized by the molecule remains in the aqueous phase, so the enantioselective resolution is high.

[0025] (2) For the reverse micelle phase obtained by extraction and separation, after back-extraction with water, the reverse micelle phase can be reused.

[0026] (3) The method for enantioselective resolution of racemic compounds by reverse micelle extraction provided by the present invention has the advantages of large processing capacity, simple operation, simple device, low resolution cost, etc., meets the requirements of large-scale production, and provides a new way for the resolution of chiral compounds. Description of the Drawings

[0027] Figure 1 TEM images of n-hexane solutions of chiral surfactant DLV at different concentrations. From left to right, the concentrations are 0.5 g / L, 1 g / L, and 2 g / L in sequence.

[0028] Figure 2 TEM images of the reverse micelle phase of 1 g / L chiral surfactant DLV in n-hexane before and after extraction of 1 g / L racemic propranolol aqueous solution. The left image is the TEM image of the reverse micelle phase before extraction, and the right image is the TEM image of the reverse micelle phase after extraction.

[0029] Figure 3 High performance liquid chromatography diagram of the reverse micelle phase after extraction equilibrium of equal volumes of 1 g / L racemic propranolol aqueous solution and 1 g / L chiral surfactant DLV in n-hexane reverse micelle solution. Detailed Embodiments

[0030] The technical solutions of the present invention are further described below in conjunction with specific embodiments, but these embodiments do not limit the present invention in any form. Unless otherwise specified in the embodiments, all are conventional reagents and conventional methods.

[0031] Example 1

[0032] Preparation of 2-decyldodecanoyl-L-valine (DLV)

[0033] Preparation of diethyl 2,2-didecylmalonate

[0034] 1.60 g of diethyl malonate was dissolved in 8 mL of tetrahydrofuran. At 0 °C, 0.40 g of NaH (60%) was added, and the reaction was carried out until the solution became clear and transparent. Then 2.21 g of 1-bromodecane was added, and the temperature was raised to 85 °C for reflux reaction for 5 h. The temperature was lowered to 0 °C, 0.40 g of NaH (60%) was added again, stirred for 45 min, and then 2.21 g of 1-bromodecane was added. The temperature was raised to 85 °C for reaction for 5 h. The reaction product was cooled to room temperature, the white solid was filtered off, and the filtrate was purified by vacuum distillation to obtain yellow oily diethyl 2,2-didecylmalonate (2.30 g, yield 52%).

[0035] Preparation of 2,2-didecylmalonic acid

[0036] 1.32 g of diethyl 2,2-didecylmalonate was dissolved in 3 mL of ethanol, and then 7.5 mL of 4 M NaOH solution was added. The mixture was refluxed at 85 °C for 10 h. The solvent of the reaction mixture was removed by rotary evaporation. The residue was adjusted to pH 2 with 2 M HCl solution, and then extracted with ethyl acetate (10 mL × 3). The organic phase was dried over anhydrous magnesium sulfate overnight, and the solvent was removed by rotary evaporation under reduced pressure to obtain 2,2-didecylmalonic acid as a yellow oil (0.70 g, yield 61%).

[0037] Preparation of 2-decyldodecanoic acid

[0038] 1.15 g of 2,2-didecylmalonic acid was dissolved in 3 mL of acetic acid. The mixture was heated at 185 °C for 8 h to decarboxylate, and the solvent was removed by rotary evaporation to obtain 2-decyldodecanoic acid as a yellowish-brown oil (0.97 g, yield 95%).

[0039] Preparation of 2-decyldodecanoyl-L-valine (DLV)

[0040] 0.34 g of 2-decyldodecanoic acid was added to 1 mL of thionyl chloride. The mixture was refluxed at 90 °C for 3 h. The excess thionyl chloride was removed by rotary evaporation under reduced pressure. The obtained alkyl acyl chloride was dissolved in 5.5 mL of tetrahydrofuran. Separately, 0.13 g of L-valine was dissolved in 5.5 mL of 0.2 M NaOH solution, and then the tetrahydrofuran solution of the alkyl acyl chloride was slowly added dropwise at 0 °C, and 2 M NaOH solution was simultaneously added dropwise to keep the pH in the range of 8 - 9. After the addition was complete, the mixture was stirred at 0 °C for 3 h. The reaction mixture was extracted with 15 mL of ethyl acetate to remove the unreacted alkyl acyl chloride. The aqueous phase was acidified to pH 2 with 1 M hydrochloric acid and extracted with ethyl acetate (15 mL × 3). The combined organic phases were dried over anhydrous magnesium sulfate overnight, and the solvent was removed by rotary evaporation under reduced pressure to obtain 2-decyldodecanoyl-L-valine as a yellowish-brown viscous substance (0.24 g, yield 55%). 1 H NMR (400 MHz, CDCl3) δ 6.02 (1H, d), 4.58 (1H, t), 2.30 - 2.25 (1H, m), 1.67 - 1.64 (1H, m), 1.39 - 1.25 (36H, m), 1.00 (3H, d), 0.97 (3H, d), 0.90 (6H, t).

[0041] Example 2

[0042] Preparation of 2-decyldodecanoyl-L-leucine (DLL)

[0043] Using 0.14 g of L-leucine instead of 0.13 g of L-valine, following the steps of Example 1, 2-decyldodecanoyl-L-leucine as a yellowish-brown viscous substance was obtained (0.23 g, yield 51%). 1HNMR(400MHz,CDCl3)δ8.82(1H,d),4.58~4.50(1H,m),2.24~2.18(1H,m),1.86~1.60(7H,m),1.34~1.1.19(32H,m),0.98~0.84(12H,m).

[0044] Example 3

[0045] Preparation of 2-butylhexanoyl-L-phenylalanine (BHF)

[0046] Using 2.74 g of 1-bromobutane instead of 4.42 g of 1-bromodecane and 0.18 g of L-phenylalanine instead of 0.13 g of L-valine, 2-butylhexanoyl-L-phenylalanine in the form of a yellowish-brown viscous substance (0.17 g, yield 53.1%) was obtained according to the steps of Example 1. 1 HNMR(400MHz,CDCl3)δ7.41~7.26(5H,m),6.03(1H,d),4.71(1H,t),3.09~2.85(2H,d),2.31~2.25(1H,m),1.40~1.26(12H,m),0.90(6H,t).

[0047] Example 4

[0048] Preparation of octadecanoyl-D-asparagine (ODN)

[0049] Using 3.05 g of 1-bromohexadecane instead of 4.42 g of 1-bromodecane and 0.15 g of D-asparagine instead of 0.13 g of L-valine, octadecanoyl-D-asparagine in the form of a yellow viscous substance (0.18 g, yield 47.4%) was obtained according to the steps of Example 1. 1 HNMR(400MHz,CDCl3)δ6.03~5.82(3H,d),4.78(1H,t),2.95~2.70(2H,d),2.12(2H,t),1.42~1.26(30H,m),0.89(3H,t).

[0050] Example 5

[0051] Determination of critical micelle concentration

[0052] Solutions of 10 g / L chiral surfactant dissolved in different organic solvents were prepared as mother liquors, and then the mother liquors were diluted in proportion to obtain chiral surfactant solutions with different concentrations. Then, the ultraviolet absorption spectra of the solutions with different concentrations were measured. A double logarithmic curve of absorbance versus concentration at the maximum ultraviolet absorption wavelength was made, and the concentration at the inflection point was the CMC. The CMCs of various chiral surfactants forming reverse micelles in various organic solvents are as follows in the table:

[0053]

[0054]

[0055] TEM images of n - hexane solutions of chiral surfactant DLV at different concentrations are shown in the appendix Figure 1 As shown, for the n - hexane solution of DLV with a concentration of 0.5 g / L, since the concentration of DLV is less than the CMC, the existence of reverse micelles was not observed; while for the n - hexane solutions of DLV with concentrations of 1 g / L and 2 g / L, since the concentration of DLV reaches or exceeds the CMC, it was observed that DLV exists in the n - hexane solvent in the form of reverse micelles.

[0056] Example 6

[0057] Prepare reverse micelle solutions of chiral surfactant DLV dissolved in n - pentane, n - hexane and cyclohexane according to the critical micelle concentrations (1 g / L, 1 g / L and 2 g / L), and prepare aqueous solutions of racemic propranolol at two concentrations (1 g / L and 2 g / L). Take 3 kinds of reverse micelle solutions, mix them with aqueous solutions of racemic propranolol with the same concentration and volume respectively, and stir magnetically for 10 min. Let it stand for layering, separate the organic phase and the aqueous phase, analyze the concentration of propranolol enantiomers by high - performance liquid chromatography, and calculate the enantioselectivity coefficient (α) and enantiomeric excess value (e.e.%) according to the following formula:

[0058]

[0059]

[0060] Among them, c org,R and c aqu,R represent the concentrations of R - propranolol in the organic phase and the aqueous phase respectively, and c org,S and c aqu,S represent the concentrations of S - propranolol in the organic phase and the aqueous phase respectively.

[0061] The obtained enantioselectivity coefficient (α) and enantiomeric excess value (e.e.%) are as follows in the table:

[0062] Chiral surfactant Organic solvent α e.e. % DLV n-Pentane 1.72 25.4 DLV n-Hexane 2.75 40.6 DLV Cyclohexane 1.48 17.7

[0063] For the n - hexane reverse micelle solution of 1 g / L chiral surfactant DLV, before and after the extraction of 1 g / L racemic propranolol solution, the TEM images of the reverse micelle phase are shown in the appendix Figure 2 As shown, the high - performance liquid chromatography diagram of the reverse micelle phase after extraction is shown in the appendix Figure 3 As shown.

[0064] Example 7

[0065] Prepare reverse micelle solutions of chiral surfactant DLL dissolved in n - hexane, cyclohexane, and n - heptane at critical micelle concentrations (1 g / L, 1.5 g / L, and 2.5 g / L), and prepare aqueous solutions of racemic propranolol at three concentrations (1 g / L, 1.5 g / L, and 2.5 g / L). Take the reverse micelle solutions at three concentrations and mix them with aqueous solutions of racemic propranolol of the same concentration and volume respectively, and stir magnetically for 10 min. Let it stand for layering, separate the organic phase and the aqueous phase, analyze the concentration of propranolol enantiomers by high - performance liquid chromatography, and calculate the enantioselectivity coefficient (α) and enantiomeric excess value (e.e. %), and the results are as follows in the table:

[0066] Chiral surfactant Organic solvent α e.e. % DLL n-Hexane 1.35 13.2 DLL Cyclohexane 1.43 16.8 DLL n-Heptane 1.21 8.8

[0067] Example 8

[0068] Prepare reverse micelle solutions of chiral surfactant BHF in n - hexane, BHF in dichloroethane, HDN in toluene, and HDN in chlorobenzene at critical micelle concentrations (6.5 g / L, 9.0 g / L, 5.5 g / L, and 6.0 g / L). And prepare aqueous solutions of five racemates of alprenolol, pindolol, metoprolol, and atenolol at a concentration of 1 g / L respectively. Take equal volumes of the four reverse micelle solutions and the aqueous solutions of the four racemates and mix them, and stir magnetically for 10 min. Let it stand for layering, separate the organic phase and the aqueous phase, analyze the concentration of enantiomers by high - performance liquid chromatography, and calculate the enantioselectivity coefficient (α) and enantiomeric excess value (e.e. %), and the results are as follows in the table:

[0069] Chiral surfactant Organic solvent Racemate α e.e. % BHF n-Hexane Alprenolol 1.82 24.8 BHF Dichloroethane Pindolol 1.42 15.2 ODN Toluene Metoprolol 2.20 32.7 ODN Chlorobenzene Atenolol 1.35 13.6

Claims

1. A method for resolving racemic compounds by enantioselective reverse micelle extraction, characterized in that: Using reverse micelles formed by chiral surfactants in non-aqueous solvents as chiral recognition extractants to selectively recognize one enantiomer from an aqueous solution of racemates. The recognized enantiomer enters the reverse micelles, while the other unrecognized enantiomer remains in the aqueous phase. The separation of the reverse micelle phase and the aqueous phase realizes the resolution of racemic compounds; The chiral surfactant is a chiral amino acid substituted by N-acyl; In the chiral amino acid substituted by N-acyl, the amino acids are each independently selected from alanine, valine, leucine, isoleucine, proline, phenylalanine, tyrosine, tryptophan, serine, threonine, cysteine, methionine, histidine, lysine, arginine, aspartic acid, glutamic acid, asparagine, glutamine; The preparation method of the chiral surfactant is as follows: Using malonic ester S1 as a raw material, undergoing C-alkylation reaction with halogenated hydrocarbons under the catalysis of a base to obtain alkyl malonic ester S2; S2 undergoes hydrolysis reaction to obtain alkyl malonic acid S3; S3 undergoes high-temperature decarboxylation to obtain alkyl acid S4; After S4 is acyl chlorinated, it undergoes N-acylation reaction with chiral amino acids to obtain chiral amino acid S substituted by N-acyl; The non-aqueous solvent is an organic solvent that is poorly soluble in water; The racemic compound is any racemate of propranolol, alprenolol, pindolol, metoprolol, atenolol.

2. The method for resolving racemic compounds by enantioselective reverse micelle extraction according to claim 1, characterized in that: In the chiral amino acid substituted by N-acyl, the alkyl groups are each independently selected from straight-chain or branched octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl, docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl, heptacosyl, octacosyl, nonacosyl, triacontyl, hentriacontyl, dotriacontyl, tritriacontyl, tetratriacontyl.

3. The method for resolving racemic compounds by enantioselective reverse micelle extraction according to claim 1, characterized in that: In the chiral amino acid substituted by N-acyl, the configuration of the amino acid is L-configuration or D-configuration.

4. The method for resolving racemic compounds by enantioselective reverse micelle extraction according to claim 1, characterized in that: The organic solvent that is poorly soluble in water is a single organic solvent that is poorly soluble in water or a mixed organic solvent that is poorly soluble in water, selected from one or a mixture of two or a mixture of three of hydrocarbons, halogenated hydrocarbons, alcohols, ethers, ketones, esters that are poorly soluble in water.

5. The method for resolving racemic compounds by enantioselective reverse micelle extraction according to claim 1, characterized in that: The water-insoluble organic solvents described above are selected from one or two solvents mixed or three solvents mixed among methylene chloride, chloroethane, dichloroethane, chloroform, carbon tetrachloride, n-pentane, isopentane, n-hexane, cyclohexane, n-heptane, isoheptane, n-octane, isooctane, n-pentanol, isopentanol, n-hexanol, isohexanol, n-heptanol, isoheptanol, n-octanol, isooctanol, cyclohexanol, propyl ether, butyl ether, pentyl ether, hexyl ether, cyclohexyl ether, phenyl ether, benzene, toluene, xylene, chlorobenzene, dichlorobenzene, butanone, pentanone, hexanone, cyclohexanone, ethyl formate, propyl formate, butyl formate, pentyl formate, hexyl formate, isooctyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, pentyl acetate, hexyl acetate, isooctyl acetate.

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