A process for the preparation of a microtubule affinity regulating kinase inhibitor intermediate

Abstract

The application provides a preparation method of a microtubule affinity-regulating kinase inhibitor intermediate, and belongs to the technical field of chemical synthesis. The microtubule affinity-regulating kinase inhibitor intermediate is (1S, 6R)-2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexan-1-ol, and the (1S, 6R)-2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexan-1-ol is prepared by using L-camphor sulfonic acid as a resolving agent. When (1S, 6R)-2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexan-1-ol is prepared by purifying 2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexan-1-ol racemate, the operation is simple, the resolving can be realized by salification, the product can be obtained by filtering and dissociating, the product has high molar yield, low product loss, good product quality and high chiral purity of 99%, and the method is more suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis technology, specifically relating to a method for preparing a microtubule affinity-modified kinase inhibitor intermediate. Background Technology

[0002] Inhibition of microtubule affinity-modified kinase (MARK) is a potentially attractive approach to halting neurofibrillary tangles lesions in Alzheimer's disease. Dementia is one of the highest areas of unmet medical needs. Alzheimer's disease (AD) is the most common cause of dementia, characterized by a slow-progressing decline in cognitive function, leading to symptoms such as memory loss and disorientation. Death occurs on average nine years after diagnosis. The incidence of AD increases with age; therefore, while approximately 5% of people over 70 are affected, this figure rises to 20% in those over 80. Despite significant efforts, a modifiable treatment for Alzheimer's disease remains elusive.

[0003] Neurofibrillary tangles (NFTs) are a pathological hallmark of Alzheimer's disease (AD), and the degree of tangle formation is closely related to cognitive decline. NFTs are composed of hyperphosphorylated tau protein, therefore, inhibiting tau protein kinases is a logical approach to treating Alzheimer's disease. Notably, KXGS microtubule-binding domains in tau are thought to control tau / microtubule binding affinity and kinetics. It is hypothesized that aberrant phosphorylation of serine residues in these KXGS motifs acts as a "master switch," leading to high levels of unbound tau and subsequent hyperphosphorylation. Microtubule affinity-regulated kinases (MARKs) have been shown to be among the kinases capable of phosphorylating S262, located in one of the KXGS binding motifs. Therefore, inhibiting MARKs may be an attractive therapeutic option for Alzheimer's disease.

[0004] Patent applications with publication numbers WO2009014620A1 and WO2011087999A1 disclose a class of 6-heterocyclic substituted pyrazolo[1,5-a]pyrimidines as inhibitors of MARK. Their selective inhibition of microtubule affinity-regulated kinase (MARK) makes them potentially useful for the treatment or prevention of Alzheimer's disease. The compounds MARK-IN-1 and MARK-IN-2 in the patents are potent inhibitors of microtubule affinity-regulated kinase (MARK), with the following structural formulas:

[0005]

[0006] (1S,6R)-2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexane-1-ol is an important intermediate fragment in the synthesis of the above-mentioned microtubule affinity-regulated kinase (MARK) inhibitor. Its CAS number is 1109284-39-0, its molecular weight is 255.31, and its molecular formula is C1. 14 H 19 F2NO has the following structural formula:

[0007]

[0008] Chinese patent application CN109715594A discloses a method for synthesizing (1S,6R)-2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexane-1-ol. The method involves reacting 7-oxabicyclo[4.1.0]heptan-2-one with DAST at room temperature to obtain 2,2-difluoro-7-oxabicyclo[4.1.0]heptane. Then, 2,2-difluoro-7-oxabicyclo[4.1.0]heptane is reacted with (R)-(+)-1-phenylethylamine in the presence of trimethylaluminum to obtain a racemic mixture of 2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexane-1-ol. This mixture is then purified by rapid chromatography to obtain (1S,6R)-2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexane-1-ol.

[0009]

[0010] The reported (1S,6R)-2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexane-1-ols are all obtained by chromatographic separation and purification of the racemic compounds after the reaction to obtain a single configuration product. The molar yield of the chromatographic purification is about 30%, which is low and requires a large amount of solvent, making it unsuitable for industrial production.

[0011] Therefore, there is a need to develop a process for preparing (1S,6R)-2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexane-1-ol that has a high yield, is easy to operate, has better quality control, and is suitable for industrial production. Summary of the Invention

[0012] The purpose of this invention is to provide a method for preparing a microtubule affinity-modified kinase inhibitor intermediate.

[0013] This invention provides the use of L-camphor sulfonic acid as a resolving agent in the resolution of the racemic mixture of 2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexane-1-ol to prepare (1S,6R)-2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexane-1-ol.

[0014] The present invention also provides a method for preparing (1S,6R)-2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexane-1-ol, which comprises the following steps:

[0015]

[0016] Step 1: Using the compound shown in Formula IV as a raw material, add the compound L-camphor sulfonic acid shown in Formula III and an organic solvent to react. After the reaction is completed, cool down to crystallize and obtain the compound shown in Formula II.

[0017] Step 2: Add the compound shown in Formula II to an organic solvent, add alkali and stir, then filter. The filter cake is the compound shown in Formula I.

[0018] Furthermore,

[0019] In step 1, the molar ratio of the compound shown in formula IV to L-camphor sulfonic acid is (2-5):1;

[0020] And / or, in step 1, the mass-to-volume ratio of the compound represented by formula IV to the organic solvent is 1 g: 10 to 100 mL;

[0021] Preferably,

[0022] In step 1, the molar ratio of the compound shown in formula IV to L-camphor sulfonic acid is 2:1;

[0023] And / or, in step 1, the mass-to-volume ratio of the compound represented by formula IV to the organic solvent is 1 g: 20 mL.

[0024] Further, in step 1, the organic solvent is acetone, ethyl acetate, tetrahydrofuran, acetonitrile, or methyl ether; preferably acetone.

[0025] Further, in step 1, the reaction temperature is 20–60°C; and / or the reaction time is 1–5 hours;

[0026] And / or, in step 1, the temperature for cooling and crystallization is 0–5°C;

[0027] And / or, in step 1, the crystallization is carried out by stirring for 0.5 to 1 hour;

[0028] Preferably, in step 1, the reaction temperature is 50°C.

[0029] Further, in step 1, the post-crystallization filtration involves drying the filter cake.

[0030] Furthermore,

[0031] In step 2, the organic solvent is a mixed solution of anhydrous ethanol and water;

[0032] And / or, in step 2, the base is sodium carbonate, potassium carbonate, sodium phosphate, or potassium phosphate;

[0033] And / or, in step 2, the temperature at which the alkali is added and stirred is 0–20°C.

[0034] Furthermore,

[0035] In step 2, the volume ratio of anhydrous ethanol to water is 1:4;

[0036] And / or, in step 2, the base is an aqueous solution of sodium carbonate;

[0037] And / or, in step 2, the temperature at which the alkali is added and stirred is 0–5°C.

[0038] Furthermore,

[0039] In step 2, the mass-to-volume ratio of the compound represented by formula II to the organic solvent is 1 g: 10-100 mL;

[0040] And / or, in step 2, the addition of alkali brings the pH to 7-8;

[0041] And / or, in step 2, the stirring time is 20 to 30 minutes.

[0042] Furthermore, in step 2, the filter cake is dried after filtration.

[0043] This invention uses L-camphor sulfonic acid as a resolving agent to form a salt with the racemic mixture. Utilizing the difference in solubility of the two chiral isomers after salt formation, it successfully separates (1S,6R)-2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexane-1-ol from the racemic mixture, achieving the purification of the racemic 2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexane-1-ol.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] The present invention provides a simple method for purifying the racemic mixture of 2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexane-1-ol to prepare (1S,6R)-2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexane-1-ol. Resolution can be achieved through salt formation, followed by filtration and dissociation to obtain the product. The obtained product has a high molar yield (greater than 42%), minimal product loss, and good quality with a chiral purity of up to 99%. This method is particularly suitable for industrial production.

[0046] Obviously, based on the above description of the present invention, and according to common technical knowledge and conventional methods in the field, various other modifications, substitutions or alterations can be made without departing from the basic technical concept of the present invention.

[0047] The following detailed embodiments further illustrate the above-described content of the present invention. However, this should not be construed as limiting the scope of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Attached Figure Description

[0048] Figure 1 This is the high-performance liquid chromatogram of compound of formula IV.

[0049] Figure 2 High-performance liquid chromatogram of compound I

[0050] Figure 3 This is the hydrogen spectrum of compound I.

[0051] Figure 4 This is the mass spectrum of compound I. Detailed Implementation

[0052] Unless otherwise specified, all raw materials or reagents used in the examples are commercially available or prepared by conventional methods. The racemic mixture of 2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexane-1-ol used in the examples can be prepared by the method disclosed in Chinese Patent Application Publication No. CN109715594A, or by other known methods, or by purchasing commercially available products.

[0053] Synthetic route of this invention:

[0054]

[0055] Step 1: Using the racemic mixture of compound IV, 2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexane-1-ol, L-camphor sulfonic acid and organic solvent were added sequentially, and the mixture was heated to react. After the reaction was completed, the mixture was cooled to crystallize, filtered, and dried to obtain compound II.

[0056] Step 2: Add the compound of formula II to an organic solvent, treat with alkali under cooling conditions, filter, and dry to obtain the compound of formula I.

[0057] In the first step: the resolving agent is L-camphor sulfonic acid; the organic solvent is acetone, ethyl acetate, tetrahydrofuran, acetonitrile or methyl ether; the reaction temperature is 20-60℃; the molar ratio of compound IV to resolving agent is 1:0.5.

[0058] In the second step: the base is sodium carbonate, potassium carbonate, sodium phosphate, or potassium phosphate; the organic solvent is a mixed solution of ethanol and water, with a volume ratio of ethanol to water of 1:4; the reaction temperature is 0-20℃.

[0059] Example 1: Using L-camphorsulfonic acid as a resolving agent

[0060] Compound IV (5.0 g, 19.6 mmol), L-camphorsulfonic acid (2.3 g, 9.8 mmol), and acetone (100 mL) were added to a reaction flask. The mixture was heated to 50 °C and stirred for 1 hour. The heating was then turned off, and the mixture was slowly cooled to room temperature. The mixture was then stirred at 0-5 °C for 0.5 hours. The mixture was filtered, and the filter cake was dried with hot air at 50 °C to give 6.66 g of compound II as a white solid. The molar yield was 45.9%, and the ee value was 99.9%.

[0061] Based on the content of Example 1, this invention investigated the resolving effect of different resolving agents on the salt formation of compound IV in acetone. The results are shown in Table 1 (the L-camphor sulfonic acid in Example 1 was replaced with different chiral resolving agents, while other conditions remained the same).

[0062] Table 1. Resolution effects of different chiral resolving agents and compounds of formula IV on salt formation in acetone.

[0063] Serial Number Dissolving agent molar yield ee value Remark Example 1 L-Camphorsulfonic acid 45.9％ 99.9％ Comparative Experiment 1 D-Camphorsulfonic acid / / No solid precipitated Comparative Experiment 2 L-tartaric acid 65.9％ -3.1％ Comparative Experiment 3 D-tartaric acid 67.3％ -0.7％

[0064] As shown in Table 1, L-tartaric acid and D-tartaric acid have virtually no resolving effect and cannot selectively precipitate a single configuration; when D-camphorsulfonic acid is used to form a salt, no solid can be precipitated; only by selecting L-camphorsulfonic acid as a resolving agent can the product with a single configuration be successfully separated.

[0065] Based on Example 1, this invention investigated the resolution effect of L-camphor sulfonic acid on the salt formation of compound IV in different solvents. The results are shown in Table 2 (the acetone in Example 1 was replaced with different solvents, while other conditions remained the same).

[0066] Table 2. Resolution effects of L-camphorsulfonic acid on salt formation of compound IV in different solvents

[0067] Serial Number Solvent splitting molar yield ee value Remark Example 1 acetone 45.9％ 99.9％ Comparative Experiment 4 Ethyl acetate 34.5％ 93.2％ Comparative Experiment 5 Methyl ether 51.9％ 82.3％ Comparative Experiment 6 Acetonitrile 31.3％ 96.5％ Comparative Experiment 7 Tetrahydrofuran 22.9％ 90.4％ Comparative Experiment 8 dichloromethane / / No solid precipitated Comparative Experiment 9 methanol / / No solid precipitated Comparative Experiment 10 ethanol / / No solid precipitated

[0068] When L-camphorsulfonic acid is used to form salts, solids cannot be precipitated when dichloromethane, methanol, or ethanol are used as solvents. However, the target configuration can be precipitated when ethyl acetate, tertiary methyl ether, acetonitrile, acetone, or tetrahydrofuran are used as solvents. Among them, the ee value is lower when tertiary methyl ether is used as a solvent, while the ee value is the highest when acetone is used as a solvent, reaching 99.9%.

[0069] Example 2: Preparation of Compound I

[0070] Add 20.0 g (41 mmol) of compound II to a reaction flask, along with 200 mL of anhydrous ethanol / water mixed solvent (volume ratio 1:4), stir, cool to 0-5 °C, slowly add 20% sodium carbonate aqueous solution, adjust pH to 7-8, then stir for 20-30 minutes, filter, and dry to dryness. Dry the filter cake with hot air at 50 °C to obtain 9.66 g of compound I as a white solid, with a molar yield of 92.3%, purity of 99.8%, and ee value of 99.9%. 1 H NMR(400MHz,Chloroform-d)δ7.35-7.22(m,5H),3.91(q,J=6.8Hz,1H),3.44-3.35(m,1H),2.74-2.67(m,1H),2.17-2 .07(m,1H),1.83-1.76(m,1H),1.71-1.54(m,2H),1.48-1.38(m,1H),1.36(d,J=6.8Hz,3H),1.03-0.90(m,1H); MS(ESI + )m / z256.4[M+H] + .

[0071] Example 3: Preparation of Compound II

[0072] Compound IV (1.5 kg, 5.88 mol), L-camphorsulfonic acid (683 g, 2.94 mol), and acetone (30 L) were added to a reaction flask. The mixture was heated to 50 °C and stirred for 1 hour. The heating was then turned off, and the mixture was slowly cooled to room temperature. The mixture was then stirred at 0-5 °C for 0.5 hours. The mixture was filtered, and the filter cake was dried with hot air at 50 °C to give 1.32 kg of a white solid, with a molar yield of 46.1% and an ee value of 99.9%.

[0073] Example 4: Preparation of Compound I

[0074] Compound II (1 kg, 20.5 mol) and ethanol / water mixed solvent (10 L, volume ratio 1:4) were added to a reaction flask. The mixture was stirred, and the temperature was lowered to 0-5 °C. A 20% sodium carbonate aqueous solution was slowly added dropwise to adjust the pH to 7-8. The mixture was then stirred for 20-30 minutes, filtered, and dried to dryness. The filter cake was dried with hot air at 50 °C to obtain 483 g of compound I as a white solid. The molar yield was 92.2%, the purity was 99.8%, and the ee value was 99.9%.

[0075] In summary, the present invention provides a simple method for purifying the racemic mixture of 2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexane-1-ol to prepare (1S,6R)-2,2-difluoro-6-(((R)-1-phenylethyl)amino)cyclohexane-1-ol. Resolution can be achieved through salt formation, and the product can be obtained by filtration and dissociation. The obtained product has a high molar yield, minimal product loss, and good quality with a chiral purity of up to 99%. Therefore, the method of the present invention is more suitable for industrial production.

Claims

1. A method for preparing (1 S 6 R )-2,2-difluoro-6-((( R The method of (-1-phenylethyl)amino)cyclohexane-1-ol, characterized in that: It includes the following steps: Step 1: Using the compound shown in Formula IV as a raw material, add the compound L-camphor sulfonic acid shown in Formula III and an organic solvent to react. After the reaction is completed, cool down to crystallize and obtain the compound shown in Formula II. Step 2: Add the compound shown in Formula II to an organic solvent, add alkali and stir, then filter. The filter cake is the compound shown in Formula I. In step 1, the organic solvent is acetone, ethyl acetate, tetrahydrofuran, acetonitrile, or methyl tertiary ether; In step 1, the molar ratio of the compound shown in formula IV to L-camphor sulfonic acid is (2~5):1; In step 1, the reaction temperature is 20~60℃; the reaction time is 1~5 hours. In step 1, the temperature for cooling and crystallization is 0~5℃; In step 2, the organic solvent is a mixed solution of anhydrous ethanol and water; In step 2, the alkali is sodium carbonate, potassium carbonate, sodium phosphate, or potassium phosphate; In step 2, alkali is added until the pH is 7-8; In step 2, the temperature at which the alkali is added and stirred is 0~20℃, and the stirring time is 20~30 minutes.

2. The method according to claim 1, characterized in that: In step 1, the mass-to-volume ratio of the compound represented by formula IV to the organic solvent is 1 g: 10~100 mL.

3. The method according to claim 2, characterized in that: In step 1, the molar ratio of the compound shown in formula IV to L-camphor sulfonic acid is 2:1; And / or, in step 1, the mass-to-volume ratio of the compound represented by formula IV to the organic solvent is 1 g: 20 mL.

4. The method according to claim 1, characterized in that: In step 1, the organic solvent is acetone.

5. The method according to claim 1, characterized in that: In step 1, the crystallization process involves stirring for 0.5 to 1 hour.

6. The method according to claim 1, characterized in that: In step 1, the reaction temperature is 50°C.

7. The method according to claim 1, characterized in that: In step 1, the crystallization is followed by filtration, and the filter cake is dried.

8. The method according to claim 1, characterized in that: In step 2, the volume ratio of anhydrous ethanol to water is 1:4; And / or, in step 2, the base is an aqueous solution of sodium carbonate; And / or, in step 2, the temperature at which the alkali is added and stirred is 0~5℃.

9. The method according to claim 1, characterized in that: In step 2, the mass-to-volume ratio of the compound shown in Formula II to the organic solvent is 1 g: 10~100 mL.

10. The method according to claim 1, characterized in that: In step 2, the filter cake is dried after filtration.

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