Magnetic nano resolving agent, preparation thereof and application of magnetic nano resolving agent in chiral drug crystal resolution

Abstract

The invention discloses a magnetic nano resolving agent, a preparation method thereof and application of the magnetic nano resolving agent in chiral drug crystal resolution. The magnetic nano resolving agent is prepared by grafting a cellulose derivative on the surfaces of magnetic nano particles with stable hydrophobic ligands through ligand exchange reaction. When the magnetic nano resolving agent is added into a racemic nimodipine supersaturated solution for crystallization, the cellulose derivative on the outer layer of the magnetic nano resolving agent can selectively enter S-nimodipine crystals, so that the S-nimodipine crystals are endowed with magnetic responsiveness; and the R-type crystal is non-magnetic. After crystallization is finished, two enantiomer crystals can be efficiently separated by applying an external magnetic field. The single crystallization resolution yield reaches 40%, the R-type ee value is larger than or equal to 90%, and the S-type ee value is larger than or equal to 80%.

Description

Technical Field

[0001] The present invention belongs to the technical field of chiral separation, and particularly relates to a magnetic nano-resolving agent, its preparation and its application in the chiral drug crystallization resolution. Background Art

[0002] Dihydropyridine drugs are a class of calcium antagonists with a 1,4-dihydropyridine ring as the core structure, mainly used for the treatment of cardiovascular diseases such as cerebral vasospasm, hypertension, and migraine. Their metabolic characteristics and pharmacodynamic effects are highly related to the enantiomeric configuration. Early studies have confirmed that S The (-)-configurations of nitrendipine, nimodipine, amlodipine, barnidipine, and benidipine have higher calcium antagonist activities than their R (+)-isomers (Goldmann, S.; Stoltefuss, J. Angew. Chem. Int. Edit. Engl. 1991, 30, 1559-1578.). However, the vast majority of S (-)-configuration dihydropyridine compounds are quite expensive because the Hantzsch reaction for synthesizing dihydropyridine molecules is not stereoselective, and dihydropyridine compounds except amlodipine are neutral, and the resolution method by diastereomeric salt resolution is cumbersome.

[0003] Nimodipine was first developed and successfully launched by Bayer AG in Germany in 1985. Subsequently, global authoritative disease guidelines (such as the American Heart Association AHA and the European Stroke Organization ESO) have clearly listed nimodipine as the first-choice drug for the treatment of cerebral vasospasm after subarachnoid hemorrhage. Its mechanism of blocking calcium ion influx and relaxing spastic blood vessels has been widely clinically verified. According to statistics by foreign research institutions, the global market size of nimodipine reached 906.4 million US dollars in 2018. Some studies have shown that S The pharmacodynamic effect of (-)-nimodipine is R 5 times that of the (+)-configuration and is more likely to participate in the metabolic cycle (Tokuma, Y.; Noguchi, H. Journal of Chromatography A 1995, 694 , 181). For the preparation of S (-)-nimodipine, although high-purity resolution can be achieved by chromatography, the cost of chiral chromatographic columns is high, the throughput is low, and the consumption of organic solvents is large, making it difficult to be applied industrially. Chinese Patent (CN202110267395.1) inhibits the growth of S type crystal nuclei by adding cellulose derivatives to promote the preferential precipitation of R type, and the single-crystallization yield can reach 9-15% and the ee value can reach 69-97%. However, this method can only obtain (-)-nimodipine with relatively low pharmacodynamic effect and still cannot meet the clinical requirements for high-pharmacodynamic R (-)-nimodipine, SDemand for Nimodipine of type SUMMARY OF THE INVENTION

[0004] The object of the present invention is to solve the above-mentioned S - technical problem that Nimodipine is difficult to prepare efficiently, and to provide a magnetic nanoresolving agent and a preparation method thereof, as well as a chiral drug crystallization resolution technology based on the magnetic nanoresolving agent.

[0005] The chiral drug may specifically be a dihydropyridine calcium antagonist drug, and more specifically may be Nimodipine.

[0006] Nimodipine is a relatively special one among dihydropyridine compounds. Racemic Nimodipine crystallizes out in the form of a racemic mixture (conglomerate) in methanol and acetone (space group P212121), and the obtained crystal is a physical mixture of R and S single crystals, which provides sufficient conditions for efficient crystallization resolution.

[0007] The magnetic nanoresolving agent provided by the present invention is a magnetic nanoparticle surface-modified with a cellulose derivative, wherein, the magnetic nanoparticles are selected from magnetic nanoparticles formed by the following materials: Fe, Co, FePt, CoPt, Fe 3 O 4 , γ-Fe 2 O 3 , M 1 Fe 2 O 4 ,, wherein, M 1 Fe 2 O 4 in M 1 represents Zn, Mn, Ni or Co; The particle size of the magnetic nanoparticles may be 3 to 200 nm, specifically may be 5 to 25 nm, and more specifically may be 5 to 15 nm; The cellulose derivative is cellulose acetate with a side-chain modified carboxyl group, In the cellulose acetate with a side-chain modified carboxyl group, the degree of substitution corresponding to the acetyl group is 1.5 to 3, and the degree of substitution of the side-chain modified carboxyl group is 0.1 to 1.0; Specifically, the cellulose derivative is cellulose acetate phthalate (CAP), the degree of substitution corresponding to the acetyl group of the cellulose acetate phthalate is 1.5 to 2.5, the degree of substitution of the benzoyl group is 0.1 to 1.0, and the molecular weight after methylation of the cellulose acetate phthalate is 5 to 100 kDa, specifically may be 10 to 35 kDa, and more specifically may be 20 to 35 kDa.

[0008] The above-mentioned magnetic nano-splitting agent, namely magnetic nanoparticles with cellulose derivatives on the surface, is prepared by a ligand exchange reaction between the cellulose derivatives and magnetic nanoparticles stabilized by hydrophobic ligands; Among them, the hydrophobic ligands used for the magnetic nanoparticles stabilized by hydrophobic ligands are selected from at least one of the following: oleic acid, oleylamine, pyrrolidone, 11,11-bis(hydroxymethyl)undecane, poly(4-vinylpyridine), and block copolymers of poly(4-vinylpyridine) and polyethylene.

[0009] The ligand exchange reaction adopted in the present invention is based on the principle of competitive displacement of the side-chain carboxyl groups of cellulose acetate phthalate (CAP) with the hydrophobic ligands (such as oleic acid) on the surface of magnetic nanoparticles, so as to achieve the stable grafting of natural polymers on the surface of magnetic particles (the reaction formula is as Figure 1 shown). It is recorded in the literature that many polymers such as polyacrylic acid, polyacrylic acid-polystyrene block polymers, polyethylene glycol with carboxyl groups at the ends, and polystyrene can be combined with magnetic particles through the ligand exchange mechanism ( Angew. Chem. Int. Ed. 2011, 50 , 7811; Nano Lett. 2010, 10 , 3216; Macromolecules 2020, 53 , 473.), which proves that it is applicable to a variety of polymer systems. Specifically, the above-mentioned magnetic nano-splitting agent, namely magnetic nanoparticles with cellulose derivatives on the surface, is prepared by a method including the following steps: (1) Dissolve the cellulose derivative in its good solvent, mix it with magnetic nanoparticles stabilized by hydrophobic ligands, stir and react at a certain temperature for a period of time, and achieve the grafting of the cellulose derivative on the surface of the magnetic nanoparticles through ligand displacement; (2) Add a selective solvent of the cellulose derivative (the selective solvent refers to the precipitant of the cellulose derivative, but less is added, and the grafted nanoparticles are more soluble in the precipitate) to the reaction solution, magnetically attract or centrifuge to collect the precipitate of the magnetic nanoparticles grafted with the cellulose derivative, then add a good solvent to disperse, and repeat the above steps twice to remove the excess hydrophobic ligands and cellulose derivatives. Finally, disperse the magnetic nano-splitting agent in a good solvent for storage, and that's it.

[0010] In step 1) of the above method, the cellulose derivative is cellulose acetate with carboxyl groups modified on the side groups, the degree of substitution corresponding to the acetyl group in the cellulose acetate with carboxyl groups modified on the side groups is 1.5-3, and the degree of substitution of the groups with carboxyl groups modified on the side groups is 0.1-1.0; Specifically, the cellulose derivative is cellulose acetate phthalate (CAP). The degree of substitution corresponding to the acetyl group of the cellulose acetate phthalate is 1.5 - 2.5, and the degree of substitution of the benzoyl group is 0.1 - 1.0. Its methylated molecular weight is 5 - 100 kDa, specifically it can be 10 - 35 kDa, and more specifically it can be 20 - 35 kDa; The good solvent is DMSO (dimethyl sulfoxide), DMF (N,N - dimethylformamide), tetrahydrofuran, dioxane, acetone; In the above method step (1), the "hydrophobic ligand - stabilized magnetic nanoparticles" can be prepared according to existing methods. For example, oleic acid - stabilized iron oxide nanoparticles (Fe 3 O 4 @oleic acid) can be prepared with reference to the literature ( Nat. Mater. 2004, 3 , 891.; J. Am. Chem. Soc. 2002, 124 , 8204; Pure and Applied Chemistry 2006, 78 , 1003.). The mass ratio of the cellulose derivative to the hydrophobic ligand - stabilized magnetic nanoparticles can be: 0.2 - 10:1, specifically it can be 1:1; The certain temperature is 15 - 80 degrees; The period of time is 0.5 - 24 h.

[0011] In the above method step (2), the selective solvent is at least one of methanol, ethanol, isopropanol, n - hexane, cyclohexane, acetonitrile; The volume ratio of the addition amount of the selective solvent to the volume of the reaction solution can be 0.1 - 5:1.

[0012] The good solvent is the same as that in step (1); The application of the above magnetic nanoparticle resolving agent in the chiral drug crystallization resolution also belongs to the protection scope of the present invention.

[0013] In the said application, the chiral drug can be a dihydropyridine calcium antagonist drug, and more specifically it can be nimodipine.

[0014] More specifically, the application is that the magnetic nanoparticle resolving agent is used for S - the highly efficient directional resolution of nimodipine.

[0015] The present invention efficiently constructs a magnetic nanoparticle resolving agent through a ligand exchange reaction. When it is added to the supersaturated solution of racemic nimodipine for crystallization, the magnetic nanoparticle resolving agent embeds S- Make it magnetic in nimodipine crystals. After crystallization, the two enantiomeric crystals are separated by a method similar to magnetic ore dressing to achieve S - Highly efficient directional resolution of nimodipine.

[0016] The present invention also provides a method for directional resolution S - Of nimodipine.

[0017] The directional resolution provided by the present invention S - The method of nimodipine includes the following steps: (1) Dissolve racemic nimodipine in a solvent, heat to complete dissolution and then filter to obtain a supersaturated solution of nimodipine to be resolved; (2) Add a dispersion of a magnetic nano-resolution agent to the above-mentioned supersaturated solution of nimodipine to make it uniformly dispersed. After slowly cooling to the crystallization temperature, add R - Nimodipine crystal seeds and let it stand; (3) After constant temperature crystallization for a certain time, cool down at a certain rate, continue crystallization, and obtain a mixture of a colored crystal and a colorless crystal after crystallization; (4) Remove the crystallization supernatant, wash the crystals, then add n-hexane to soak the crystals, adsorb with a magnet and collect the magnetic crystals, that is, the resolution of the two enantiomers is achieved. The magnetic crystals are S - Nimodipine.

[0018] In step (1) of the above method, the solvent is acetone; In the supersaturated solution of nimodipine, the concentration of nimodipine is not less than 350 mg•mL -1 , not higher than 800 mg•mL -1 , specifically 450 mg•mL -1 .

[0019] In step (2) of the above method, the magnetic nano-resolution agent accounts for 0.05-2.0 wt% of the mass of the racemic substrate to be resolved, specifically 0.25-1.0 wt%.

[0020] In step (3) of the above method, the temperature of the constant temperature crystallization can be 20-40 degrees, and the time can be 6-48 hours; Cool down at a certain rate, and the cooling rate is 4-50 degrees / hour, preferably 10 degrees / hour, and the final temperature is 0-20 degrees; The time for the continued crystallization can be 6-48 hours; More specifically, at a constant temperature of 25 degrees, crystallize for 0-12 h, cool down from 25 degrees to 15 degrees at a cooling rate of 10 degrees / hour in a gradient manner, and continue crystallization at the final temperature of 15 degrees for 0-23 h (specifically 3-23 h, more specifically 3 h, 5 h, 11 h, 23 h). In step (4) of the above method, the magnetic field strength of the magnet used is greater than 0.2 T.

[0021] The present invention has the following advantages: 1. The present invention for the first time uses ligand exchange reaction to prepare magnetic nanoresolving agents, realizes the stable grafting of polymers on the surface of magnetic particles, has mild reaction conditions, high grafting rate, and the magnetic nanoresolving agents can be stably dispersed in solvents for more than one week. Moreover, the ligand exchange reaction can be realized in a conventional reactor, and the single-batch output can reach the gram level.

[0022] 2. The chiral recognition polymer used is a natural polymer cellulose derivative, with cheap and renewable raw materials, simple synthesis, and large-scale preparation has been realized industrially.

[0023] 3. Although existing studies have proved that S -nimodipine has better drug efficacy than R -nimodipine, however, due to the lack of low-cost resolution means and the extremely large demand for nimodipine, nimodipine sold on the market currently appears in the form of racemates. The "magnetic separation" crystallization resolution technology applied in the present invention requires simple equipment and can realize full-automatic resolution, which is beneficial to large-scale industrial production. Description of the Drawings

[0024] Figure 1 In (a) is a schematic structural diagram of cellulose acetate phthalate; (b) is a schematic diagram of preparing magnetic nanoresolving agents by ligand exchange reaction.

[0025] Figure 2 is the permeation gel chromatogram of cellulose acetate phthalate with different molecular weights of methyl esters.

[0026] Figure 3 In (a) is the thermogravimetric curve of the magnetic nanoresolving agent and (b) the hysteresis loop and the photo of it being attracted by a magnet when dispersed in tetrahydrofuran.

[0027] Figure 4 In (a) is the photo of the R and S type nimodipine crystals obtained in Example 6 attracted by a magnet, among which the attracted ones are S type crystals, and the non-attracted ones are R type crystals. The ones attracted by saturated brine as the solvent are the magnetic nanoresolving agents with a 5 nm core, and the ones attracted by n-hexane as the solvent are the magnetic nanoresolving agents with a 10 nm core; (b) is the photo of the R and S type nimodipine crystals obtained in Example 6 (using magnetic nanoresolving agents with a 10 nm core).

[0028] Figure 5 It is a typical split HPLC chromatogram. Specific embodiments

[0029] The present invention will be further described in detail below in conjunction with specific embodiments. The examples given are only for clarifying the present invention and not for limiting the scope of the present invention. The following examples can be used as a guide for those of ordinary skill in the art to make further improvements and do not constitute any limitation to the present invention in any way.

[0030] The experimental methods in the following examples are all conventional methods unless otherwise specified, and are carried out according to the techniques or conditions described in the literature in this field or according to the product instructions. The materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

[0031] CAP 30k (Phthaloyl 30.8 wt%, degree of substitution 0.7; acetyl 25.2 wt%, degree of substitution 2.1) is commercially available cellulose acetate phthalate, CAS: 9004-38-0. Cellulose acetate phthalate with different molecular weights is obtained through the following steps.

[0032] CAP 20k and CAP 10k are all prepared using CAP 30k as the raw material. The principle is to hydrolyze the glycosidic bond of the cellulose main chain using perchloric acid to degrade high molecular weight CAP into short chains, and through NMR characterization, the degree of side group substitution remains unchanged.

[0033] Preparation of CAP 20k : Add 10 g of commercial CAP to a 500 mL round-bottom flask, then add 180 mL of acetic acid and 20 mL of acetic anhydride, and stir at 60 °C for 4 h. After all the cellulose acetate phthalate has dissolved, cool to 40 °C. Dropwise add a mixed solution of perchloric acid and acetic acid (0.6 mL of 70% perchloric acid aqueous solution, 2.4 mL of acetic acid) to the system, and react at 40 °C for 5 hours.

[0034] After the reaction is completed, drop the reaction solution into ether for precipitation, filter by suction, dissolve the obtained white powdery solid in about 100 mL of tetrahydrofuran, and precipitate again in ether. Repeat this dissolution-precipitation cycle three times. Dry the obtained white solid in a vacuum oven at room temperature overnight to obtain 8.1 g of white solid, with a yield of 81%.

[0035] Preparation of CAP 10k : Add 10 g of commercial cellulose acetate phthalate (Sheen's) to a 500 mL round-bottom flask, then add 180 mL of acetic acid and 20 mL of acetic anhydride, and stir at 60 °C for 4 h. After all the cellulose acetate phthalate has dissolved, cool the temperature to 40 °C. Dropwise add a mixed solution of perchloric acid and acetic acid (0.6 mL of 70% perchloric acid aqueous solution, 2.4 mL of acetic acid) to the system, and react at 40 °C for 16 h.

[0036] After the reaction is completed, drop the reaction solution into ether for precipitation, filter by suction, dissolve the obtained white powdery solid in about 100 mL of tetrahydrofuran, and precipitate again in ether. Repeat this dissolution-precipitation cycle three times. Dry the obtained white solid in a vacuum oven at room temperature overnight to obtain 7.5 g of white solid, with a yield of 75%.

[0037] Methyl esterification of CAP: Dissolve 100 mg of cellulose acetate phthalate in 5 mL of THF, add 1 mL of a n-hexane solution of trimethylsilyldiazomethane (2 M) under light protection, and stir at room temperature for 12 h.

[0038] After the reaction is completed, precipitate the mixed solution in ether, centrifuge to obtain a white solid, add 5 mL of THF to dissolve it, and precipitate again in ether. Repeat this dissolution-precipitation cycle three times. Dry the obtained white solid in a vacuum oven at room temperature overnight to obtain a white solid for GPC testing.

[0039] When measuring the molecular weight, first carboxylate-methylate the carboxyl group of the cellulose derivative with a carboxyl group and then measure it. Avoid the influence between the carboxyl group and the chromatographic column. The relative molecular weight and molecular weight distribution of the above-mentioned methyl esterified cellulose acetate phthalate were measured by gel permeation chromatography (GPC). Use a Waters 515 pump, a Waters 2410 differential refractometer detector, and Waters Styragel HT2+HT3+HT4 chromatographic columns. The column temperature is 35 °C, narrow distribution polystyrene is used as the standard sample, tetrahydrofuran is used as the mobile phase, and the flow rate is 1.0 mL / min. The obtained gel permeation chromatogram is as Figure 2 shown.

[0040] The obtained ee% values of nimodipine were all obtained by testing with high performance liquid chromatography (equipped with a PU-2089 pump, an A S -2055 autoinjector, a CD-2095 detector, and a UV-2070 detector). The chromatographic column used was a CHIRALCEL OD column, the mobile phase was n-hexane:isopropanol = 90:10; the flow rate was 1.0 mL / min; the sample concentration was 0.5 mg / mL; the detection wavelength was 254 nm.

[0041] Example 1. Preparation of magnetic nanoseparation agent (10 nm Fe₃O₄ core) Prepare according to Figure 1 the flow chart shown.

[0042] (1) Oleic acid-stabilized Fe₃O₄ nanoparticles (Fe 3 O 4 -OA; Fe 3 O 4 @oleic acid) were prepared according to the literature method ([[]] Nat. Mater. 2004, 3 , 891.), and the diameter was controlled at about 10 nm.

[0043] (2) Dissolve 60 mg of cellulose acetate phthalate (methyl esterification molecular weight 30 k) in 3 mL of THF, and slowly add dropwise the THF solution of Fe 3 O 4 -OA (3 mL, 20 mg / mL), and stir and react at 60 °C for 12 hours. After the reaction, take out 2 mL of the reaction solution, and add 0.6 mL of n-hexane (30% of the THF solvent) to selectively precipitate the Fe 3 O 4 -CAP flocculent precipitate. Centrifuge to collect the precipitate, and redisperse it in 5 mL of THF. Repeat the above operation twice to obtain the product Fe 3 O 4 (10 nm)-CAP 30k (49.7 mg).

[0044] Example 2. Preparation of magnetic nanoseparation agent (5 nm Fe₃O₄ core) (1) Oleic acid-stabilized Fe₃O₄ nanoparticles (Fe 3 O 4 -OA; Fe 3 O 4 @oleic acid) were prepared according to the literature method ([[]] J. Am. Chem. Soc. 2002, 124 , 8204; Pure and Applied Chemistry 2006, 78 , 1003.), and the diameter was controlled at about 5 nm.

[0045] (2) Dissolve 60 mg of cellulose acetate phthalate (methyl esterification molecular weight 30 k) in 3 mL of THF, and slowly add dropwise the THF solution of Fe 3 O 4-THF solution of OA (3 mL, 20 mg / mL), and stirred the reaction at 60 °C for 12 hours. After the reaction, 2 mL of the reaction solution was taken out, and 0.6 mL of n-hexane (30% of the THF solvent) was added to selectively precipitate Fe 3 O 4 -CAP flocculent precipitate, the precipitate was collected by centrifugation and redispersed in 5 mL of THF. The above operation was repeated twice to obtain the product Fe 3 O 4 (5nm)-CAP 30k (44.2 mg).

[0046] Example 3 In this example, the effect of different crystallization times on the resolution of nimodipine was studied. The specific operation method was as follows: (1) Add 5.4 g of acetone to 4.2 g of racemic nimodipine, heat up to 50 °C, stir well to dissolve it, and filter while hot to obtain a supersaturated solution.

[0047] (2) Measure 1.8 g of the solution obtained in step (1) into a 25 mL beaker (the mass of nimodipine contained is 750 mg).

[0048] (3) Add 250 μL (15 mg / mL) of the solution of the magnetic nano-resolution agent (prepared in Example 1) dispersed in acetone to the beaker, and shake the solution slightly to completely disperse it.

[0049] (4) After adding a very small amount of R type nimodipine crystal seeds, place it in a 25 °C water bath to crystallize for 12 h. Slowly cool from 25 °C to 15 °C (1 hour), and crystallize at 15 °C for different times.

[0050] (5) Remove the crystallization supernatant, wash the crystals with ethanol, then add n-hexane to soak the crystals, and adsorb and collect the magnetic crystals with a magnet (about 0.2 T). Dry the magnetic and non-magnetic crystals separately, dissolve the crystals in isopropanol, and test the ee value by chiral HPLC.

[0051] The crystals obtained in this example were mainly characterized by crystal yield and enantiomeric excess value. The statistical results are as follows: Table 1. Effect of different crystallization times on the resolution of nimodipine

[0052] Note: Crystallize at 25 °C for 0 - 12 h; Gradient cooling from 25 °C to 15 °C for 12 - 13 h; Crystallize at 15 °C for 13 - 36 h.

[0053] Example 4 In this example, the effects of different addition amounts on the resolution of nimodipine were studied. The specific operation method was as follows: (1) Add 5.4 g of acetone to 4.2 g of racemic nimodipine, heat to 50 °C, stir well to dissolve it, and filter while hot to obtain a supersaturated solution.

[0054] (2) Measure 1.8 g of the solution obtained in step (1) into a 25 mL beaker (the mass of nimodipine contained is 750 mg).

[0055] (3) Add 250 μL of a solution of magnetic nanoresolving agent (prepared in Example 1) dispersed in acetone (30, 15, 7.5, 3 mg / mL) to the beaker, and gently shake the solution to completely disperse it.

[0056] (4) After adding a very small amount of R seed crystals of type

[0057] nimodipine, place it in a 25 °C water bath for crystallization for 12 h. Slowly cool from 25 °C to 15 °C (1 hour), and crystallize at 15 °C for 11 h.

[0058] Table 2. Effects of different addition amounts of magnetic nanoresolving agent on the resolution of nimodipine

[0059] Example 5 In this example, the effects of different CAP molecular weights on the resolution of nimodipine were studied. The specific operation method was as follows: (1) Add 5.4 g of acetone to 4.2 g of racemic nimodipine, heat to 50 °C, stir well to dissolve it, and filter while hot to obtain a supersaturated solution.

[0060] (2) Measure 1.8 g of the solution obtained in step (1) into a 25 mL beaker (the mass of nimodipine contained is 750 mg).

[0061] (3) Add 250 μL of a solution of magnetic nanoresolving agent dispersed in acetone (the concentration is determined according to the content of CAP, and it is 0.25 wt% calculated based on the content of CAP) to the beaker, and gently shake the solution to completely disperse it.

[0062] (4) After adding a very small amount of R seed crystals of type

[0063] (5) Remove the crystalline supernatant, wash the crystals with ethanol, then soak the crystals in n - hexane, and adsorb and collect the magnetic crystals with a magnet. Dry the magnetic and non - magnetic crystals separately. After dissolving the crystals in isopropanol, test the ee value by chiral HPLC.

[0064] Table 3. Influence of different CAP molecular weights on the surface of magnetic nano - resolving agents on the resolution of nimodipine

[0065] Note: The particle size is 10 nm for all, and the preparation method is as in Example 1. CAPs with molecular weights of 30, 20, and 10 were used respectively. kDa were used. Example 6 In this example, the influence of magnetic nanoparticles with different particle sizes on the resolution of nimodipine was studied. The specific operation method is as follows: (1) Add 5.4 g of acetone to 4.2 g of racemic nimodipine, heat up to 50 °C, stir well to dissolve it, and filter while it is hot to obtain a supersaturated solution.

[0066] (2) Measure 1.8 g of the solution obtained in step (1) into a 25 - mL beaker (the mass of nimodipine contained is 750 mg).

[0067] (3) Add 250 μL of the magnetic nano - resolving agent solution dispersed in acetone to the beaker (the concentration is determined according to the content of CAP, and it is 0.25 wt% calculated based on the CAP content), and gently shake the solution to make it completely dispersed.

[0068] (4) After adding a very small amount R of the crystal seeds of type nimodipine, place it in a 25 °C water bath to crystallize for 12 h. Slowly cool from 25 °C to 15 °C (1 hour), and crystallize at 15 °C for 11 h.

[0069] (5) Remove the crystalline supernatant, wash the crystals with ethanol, then soak the crystals in n - hexane or saturated brine, and adsorb and collect the magnetic crystals with a magnet. Dry the magnetic and non - magnetic crystals separately. After dissolving the crystals in isopropanol, test the ee value by chiral HPLC.

[0070] Table 4. Influence of magnetic cores with different sizes in magnetic nano - resolving agents on the resolution of nimodipine

[0071] Note: The CAP molecular weight is 30k for all, and the magnetic nanoparticles used are all magnetite, but the sizes are different. The 5 - nm resolving agent was prepared as in Example 2, and the 25 - nm one was prepared in a similar way to Examples 1 and 2.

[0072] The present invention has been described in detail above. For those skilled in the art, without departing from the gist and scope of the present invention and without unnecessary experiments, the present invention can be implemented within a relatively wide range under equivalent parameters, concentrations and conditions. Although specific embodiments of the present invention are given, it should be understood that the present invention can be further improved. In short, according to the principle of the present invention, this application intends to cover any modifications, uses or improvements to the present invention, including those that depart from the scope disclosed in this application and are made with conventional techniques known in the art.

Claims

1. A magnetic nano-resolution agent, which is a magnetic nano-particle with a cellulose derivative modified on the surface, in, The magnetic nanoparticles are selected from the following materials: Fe, Co, FePt, CoPt, Fe3O4, γ-Fe2O3, M1Fe2O4, wherein M1 in M1Fe2O4 represents Zn, Mn, Ni or Co; The particle size of the magnetic nanoparticles is 3 to 200 nm; The cellulose derivative is cellulose acetate with a carboxyl group modified by a side group.

2. The magnetic nano-resolution agent according to claim 1, characterized in that The degree of substitution of the acetyl group in the cellulose acetate with side-group modified carboxyl group is 1.5-3, and the degree of substitution of the group with side-group modified carboxyl group is 0.1-1.0; The hydrophobic ligand used in the hydrophobic ligand-stabilized magnetic nanoparticles is selected from at least one of the following: oleic acid, oleylamine, pyrrolidone, 11,11-bis(hydroxymethylundecane), poly(4-vinylpyridine), and a block copolymer of poly(4-vinylpyridine) and polyethylene.

3. The magnetic nano-resolution agent according to claim 1, characterized in that The cellulose derivative is cellulose acetate phthalate (CAP), the substitution degree of the acetyl group of the cellulose acetate phthalate is 1.5-2.5, the substitution degree of the benzoyl group is 0.1-1.0, and the molecular weight of the cellulose acetate phthalate after methyl esterification is 5-100 kDa.

4. A method for preparing the magnetic nano-resolution agent according to any one of claims 1 to 3, comprising the following steps: (1) dissolving a cellulose derivative in a good solvent, mixing the mixture with magnetic nanoparticles stabilized by hydrophobic ligands, stirring the mixture for a period of time at a certain temperature, and grafting the cellulose derivative onto the surface of the magnetic nanoparticles through ligand replacement; (2) Add a selective solvent for cellulose derivatives to the reaction solution, collect the magnetic nanoparticles grafted with cellulose derivatives by magnetic attraction or centrifugation, then add a good solvent to disperse them, and repeat the above steps twice to remove excess hydrophobic ligands and cellulose derivatives. Finally, the magnetic nanoresolving agent is dispersed in the good solvent and stored.

5. The method according to claim 4, characterized in that In step 1), the good solvent is DMSO dimethyl sulfoxide, DMF, tetrahydrofuran, dioxane, acetone; The mass ratio of the cellulose derivative to the hydrophobic ligand-stabilized magnetic nanoparticles is: 0.2-10:1; The certain temperature is 15-80 degrees; The period of time is 0.5-24h; In step (2), the selective solvent is at least one of methanol, ethanol, isopropanol, n-hexane, cyclohexane, and acetonitrile; The good solvent is the same as that in step (1).

6. Use of the magnetic nano-resolution agent according to any one of claims 1 to 3 in the crystal resolution of chiral drugs.

7. The use according to claim 6, characterized in that: The chiral drug is a dihydropyridine drug, more specifically nimodipine. Further, the application is a magnetic nano-resolving agent for S -Efficient targeted resolution of nimodipine.

8. A directional split S - nimodipine method, comprising the steps of: (1) dissolving racemic nimodipine in a solvent, heating until completely dissolved, and filtering to obtain a supersaturated solution of nimodipine to be separated; (2) Add the dispersion of magnetic nano-resolution agent to the above nimodipine supersaturated solution to make it evenly dispersed, slowly cool it to the crystallization temperature, and then add R - Nimodipine seed crystals, let stand; (3) After a certain period of constant temperature crystallization, the temperature is lowered at a certain rate and crystallization continues. After the crystallization is completed, a mixture of a colored crystal and a colorless crystal is obtained; (4) removing the crystallization supernatant, washing the crystals, adding n-hexane to soak the crystals, and using a magnet to adsorb and collect the magnetic crystals, thereby achieving the separation of the two enantiomers. The magnetic crystals are S -Nimodipine.

9. The method according to claim 8, characterized in that In step (1), the solvent is acetone; In the supersaturated solution of nimodipine, the concentration of nimodipine is not less than 350 mg•mL -1 , not more than 800 mg•mL -1 ; In step (2), the magnetic nano-resolution agent accounts for 0.05-2.0 wt% of the racemic substrate to be resolved; In step (3), the temperature of the isothermal crystallization is 20-40 degrees and the time is 6-48 hours; Cool down at a certain rate, the cooling rate is 4-50 degrees / hour, and the final temperature is 0-20 degrees; The time for continuing crystallization is 6-48 hours; In step (4), the magnetic field strength of the magnet used is greater than 0.2 T.

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