Refining method and solvent composition of esculentin intermediate

Abstract

The invention belongs to the technical field of medicine synthesis, and particularly relates to a refining method of an esculentin intermediate and a solvent composition of the esculentin intermediate. According to the present invention, the intermediate of the etencycline is (S2S)-N-[[3-(benzyloxy)-1, 2-oxazole-5-yl] methylene]-2-methylpropane-2-sulfinamide, and the structural formula of the etencycline is shown in the description; the method comprises the following steps: mixing a crude product of the esculentin intermediate with a mixed solvent of a soluble organic solvent and an inert organic solvent, heating, stirring, dissolving, cooling, stirring, crystallizing, filtering and drying to obtain a pure product of the esculentin intermediate. Wherein the soluble organic solvent is any one of isopropyl ether and methyl tert-butyl ether or a mixture of isopropyl ether and methyl tert-butyl ether; and the inert organic solvent is any one or a mixture of two of n-hexane and n-heptane. The purity of the pure product of the esculentin intermediate refined by the method is greater than 99.0%, and the content of single impurity is less than 0.5%; the method has the advantages of simplicity in operation, short refining time, good product quality and easiness in industrial amplification.

Description

Technical Field

[0001] The invention belongs to the technical field of drug synthesis, and particularly relates to a purification method of an elacycline intermediate and a solvent composition thereof. Background Art

[0002] Eracycline hydrochloride is a fully synthetic, broad-spectrum, fluorinated tetracycline antibacterial drug, and its structural formula is shown in Formula VI. The drug was developed by Tetraphase Pharms and was launched in the United States in August 2018, in the European Union in September 2018, and imported and launched in China in March 2023. Eracycline hydrochloride is mainly used to treat complicated intraperitoneal infections caused by sensitive microorganisms. Its mechanism of action is to bind to the 30S ribosomal subunit, thereby preventing the binding of amino acid residues in the extended peptide chain and disrupting the synthesis of bacterial proteins. This mechanism gives Eracycline hydrochloride a broad-spectrum antibacterial activity and has a significant inhibitory effect on a variety of drug-resistant bacteria.

[0003]

[0004] J.Med.Chem.2020,63,10652-10704 reviews the total synthesis route of elacycline hydrochloride. According to its synthesis route, the compound shown in the following formula I is an important key early intermediate in the synthesis of elacycline hydrochloride, and it plays an important role in the synthesis process of elacycline hydrochloride. In our research on this synthesis process, we found that the elacycline intermediate shown in formula I is prone to introduce more impurities during the preparation process, including K3, K4, benzyl chloride, K4a, etc. The structural formulas of K3, K4, benzyl chloride and K4a are shown in formula II-V, respectively.

[0005]

[0006] Further research found that the existing purification process of elacycline intermediates is difficult to reduce the above impurities to trace amounts or completely remove them. For example, the prior art Org.Process Res.Dev.2015,19,1784-1795 describes in detail the preparation process of 100 kg of elacycline intermediates shown in formula I. The purification method is to first dissolve the intermediate crude product shown in formula I with isopropanol at high temperature, then drop a portion of water for 5 hours, add seed crystals, precipitate solids, and then drop the remaining water for 5 hours, and then slowly cool down within 4 to 5 hours to crystallize for 5 hours, filter, and dry the filter cake at 40 to 45 degrees for 90 hours to obtain a pure intermediate. The purity of the obtained pure intermediate is 97.2%, the residual isopropanol is 0.04%, the water is 0.05%, and the chiral impurities are 0.5%. However, the refining method has at least the following defects: 1) the entire refining process takes a long time, nearly 20 hours; 2) the product purity is low; 3) the introduction of protic solvents such as alcohol and water in the next reaction needs to be strictly controlled; 4) due to the low melting point of the product, only 65-70°C, it is necessary to carry out low-temperature drying for up to 90 hours to remove the residual refining solvents isopropanol and water; 5) the intermediate obtained by the method still contains a certain amount of impurities K3, K4, benzyl chloride and K4a; and the next reaction process of the intermediate shown in formula I in the synthesis process of eracycline hydrochloride is to react with format vinyl magnesium chloride. The K3, K4 and K4a introduced in this step will react with vinyl magnesium chloride, introduce impurities, consume raw materials and reduce the reaction process; benzyl chloride will undergo format exchange with vinyl magnesium chloride and react with the intermediate of formula I to generate a product with a structure similar to the main product, affecting the quality of subsequent products.

[0007] Therefore, it is necessary to establish a method with simple operation, short time and high purity to purify the elacycline intermediate shown in formula I, improve product quality and promote the subsequent reaction process. This is of great significance to improving the quality of elacycline hydrochloride preparation products. Summary of the invention

[0008] In view of this, in order to overcome the problems of long refining process and low product purity in the prior art, the present invention proposes a new method for refining an elacycline intermediate, which utilizes a mixed solvent crystallization of a soluble organic solvent and an inert organic solvent to effectively shorten the operation time and improve the product quality.

[0009] One of the purposes of the present invention is to provide a method for purifying an eracycline intermediate, which provides support for the subsequent synthesis and quality control of eracycline.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

[0011] A method for refining an eracycline intermediate comprises crystallizing an eracycline intermediate crude product using a mixed solvent of a readily soluble organic solvent and an inert organic solvent to obtain an eracycline intermediate pure product; the readily soluble organic solvent comprises any one of isopropyl ether and methyl tert-butyl ether or a mixture of the two; the inert organic solvent comprises any one or more of petroleum ether, n-hexane, and n-heptane; the structural formula of the eracycline intermediate is shown in Formula I;

[0012]

[0013] Further, the Chinese chemical name of the crude intermediate of exalacycline is (S 2 S)-N-[[3-(Benzyloxy)-1,2-oxazol-5-yl]methylene]-2-methylpropane-2-sulfenamide.

[0014] Furthermore, the volume ratio of the readily soluble organic solvent to the inert organic solvent is 1:0.5 to 1:2, and most preferably 1:0.5, 1:1 and / or 1:2.

[0015] Furthermore, the usage ratio of the crude elacycline intermediate to the readily soluble organic solvent is 1g:2mL to 1g:5mL, preferably 1g:3mL to 1g:4mL, and most preferably 1g:3mL and / or 1g:4mL.

[0016] Furthermore, the crystallization time is 2h-4h, preferably 3h.

[0017] Furthermore, the crude intermediate of exalacycline is mixed with a solvent, heated to dissolve, and then crystallized.

[0018] Furthermore, after the crystallization step, the product is filtered and dried at 30-40° C. for 1.5-3 hours to obtain a pure intermediate of eracycline.

[0019] Preferably, the drying is performed at 35°C for 2 hours.

[0020] Furthermore, the purification method is to add the crude product of the elacycline intermediate into a mixed solvent of the soluble organic solvent and the inert organic solvent, dissolve, and crystallize to obtain a pure product of the elacycline intermediate (method one);

[0021] And / or the crude eracycline intermediate is first dissolved in the readily soluble organic solvent, then mixed with the inert organic solvent, and crystallized to obtain a pure eracycline intermediate (method 2).

[0022] Furthermore, the crystallization is performed by cooling the temperature to -20°C to 10°C.

[0023] Further, the solution is cooled to -20°C to 10°C within 4-6 hours for crystallization.

[0024] Preferably, the solution is cooled to -10°C to 0°C for crystallization, and most preferably, the solution is cooled to -10°C for crystallization.

[0025] Furthermore, the mixing in the second method refers to adding or dropping the dissolved solution into an inert organic solvent, or adding or dropping the inert organic solvent into the dissolved solution.

[0026] As one of the most preferred technical solutions, the refining method has the following steps:

[0027] Add the crude product of the elacycline intermediate and a soluble organic solvent into a reaction bottle, stir, heat, and stir to dissolve; add an inert organic solvent, stir to dissolve, cool to -10°C within 4-6 hours, stir to crystallize for 3 hours, filter, and dry at 35°C for 2 hours to obtain a pure product of the elacycline intermediate.

[0028] As one of the most preferred technical solutions, the refining method has the following steps:

[0029] Add the crude product of eracycline intermediate, soluble organic solvent and inert organic solvent into a reaction bottle, stir, heat, stir to dissolve, cool to -10°C within 4-6 hours, stir to crystallize for 3 hours, filter, and dry at 35°C for 2 hours to obtain the pure product of eracycline intermediate.

[0030] The second object of the present invention is to provide a solvent composition for refining an elacycline intermediate.

[0031] To achieve the above object, the present invention adopts the following technical solutions:

[0032] The invention discloses a solvent composition for refining an exalacycline intermediate, wherein the solvent composition comprises a soluble organic solvent and an inert organic solvent; the soluble organic solvent comprises any one of isopropyl ether and methyl tert-butyl ether or a mixture of the two; and the inert organic solvent comprises any one or more of petroleum ether, n-hexane and n-heptane.

[0033] The beneficial effects of the present invention are:

[0034] 1. The present invention provides a method for refining an elacycline intermediate, wherein a crude elacycline intermediate is crystallized in a mixed solvent of a soluble organic solvent and an inert organic solvent, and the obtained product has low impurity content and high purity. Under the method of the present invention, the purity of the product can be increased to more than 99.0%, the single impurity is less than 0.5%, the chiral impurity is less than 0.3%, and the water content is less than 0.05%, which significantly improves the product quality.

[0035] 2. The refining time of the elacycline intermediate can be shortened to about 10 hours by using the method of the present invention.

[0036] 3. The method of the present invention avoids the use of water and proton solvents, will not affect the anhydrous reaction in the subsequent process, and can shorten the drying time to 2 hours when using a lower drying temperature. It has the advantages of shortening the drying time, lowering the drying temperature, simplifying the operation, and being conducive to industrial scale-up. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 HPLC chart of crude intermediate of elacycline;

[0038] Figure 2 HPLC chart of the pure elacycline intermediate prepared in Example 1;

[0039] Figure 3 This is a chiral HPLC chart of the pure elacycline intermediate prepared in Example 1;

[0040] Figure 4 This is the DSC chart of the pure elacycline intermediate prepared in Example 1. DETAILED DESCRIPTION

[0041] The technical solution of the present invention will be further described clearly and completely in conjunction with specific embodiments below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present invention.

[0042] In the examples of the present invention, the structural formulas of the compounds involved are shown in Table 1.

[0043] Table 1. Compound information list

[0044]

[0045] In the present invention, the objects treated in Examples 1-7 and Comparative Example 1 are all crude products of the intermediate of eracycline with the structural formula O as shown in Formula I. The HPLC results of the crude products of the intermediate of eracycline are as follows: Figure 1 As shown, the pure residual content of the front HP stage L process is 82.9%, the residual intermediate K3 is 2.52%, the residual intermediate reagent K4benzyl chloride is 0.66%, the residual reagent abenzyl chloride of the front stage process is 6.04%, and the front stage process by-product K4a is 3.81%.

[0046] Example 1. Purification of crude elacycline intermediate

[0047] 50g of the crude intermediate of elacycline and 200ml of isopropyl ether were added to a reaction bottle, stirred, heated, stirred and dissolved, 100ml of n-hexane was added, stirred and dissolved, cooled to -10°C within 4 hours, stirred and crystallized for 3 hours, filtered, and dried at 35°C for 2 hours to obtain the pure intermediate of elacycline. The product is a needle-shaped yellow crystalline solid with a mass yield of 88.5% and a purity of 99.13%. K4a is 0.26%, K4 is 0.18%, benzyl chloride is 0.06%, K3 is 0.21%, chiral impurities are 0.24%, and water is 0.02%. Among them, the HPLC test results of the pure intermediate of elacycline are shown in Figure 2 The chiral HPLC test results of the pure intermediate of elacycline are shown in Figure 3 The DSC diagram of the pure intermediate of elacycline is shown in Figure 4 .

[0048] Example 2. Purification of crude elacycline intermediate

[0049] 50g of the crude product of the elacycline intermediate and 200ml of isopropyl ether were added to a reaction bottle, stirred, heated, stirred and dissolved, 100ml of n-heptane was added, stirred and dissolved, cooled to -10°C within 4 hours, stirred and crystallized for 3 hours, filtered, and dried at 35°C for 2 hours to obtain a pure elacycline intermediate. The product is a needle-shaped yellow crystalline solid, with a mass yield of 90.1%, a purity of 99.07%, K4a of 0.23%, K4 of 0.12%, benzyl chloride of 0.06%, K3 of 0.28%, chiral impurities of 0.22%, and water of 0.03%.

[0050] Example 3. Purification of crude elacycline intermediate

[0051] 50g of the crude product of the elacycline intermediate and 200ml of isopropyl ether were added to a reaction bottle, stirred, heated, stirred and dissolved, 100ml of petroleum ether was added, stirred and dissolved, cooled to -10°C within 4 hours, stirred and crystallized for 3 hours, filtered, and dried at 35°C for 2 hours to obtain the pure elacycline intermediate. The product is a needle-shaped yellow crystalline solid, with a mass yield of 87.9%, a purity of 99.22%, K4a of 0.24%, K4 of 0.14%, benzyl chloride of 0.06%, K3 of 0.29%, chiral impurities of 0.20%, and water of 0.02%.

[0052] Example 4. Purification of crude elacycline intermediate

[0053] 50g of the crude product of the elacycline intermediate and 200ml of methyl tert-butyl ether were added to a reaction bottle, stirred, heated, stirred and dissolved, 200ml of n-hexane was added, stirred and dissolved, cooled to -10°C within 4 hours, stirred and crystallized for 3 hours, filtered, and dried at 35°C for 2 hours to obtain the pure elacycline intermediate. The product was a needle-shaped yellow crystalline solid, with a mass yield of 89.3%, a purity of 99.12%, K4a of 0.34%, K4 of 0.13%, no benzyl chloride detected, K3 of 0.31%, chiral impurities of 0.25%, and water of 0.02%.

[0054] Example 5. Purification of crude elacycline intermediate

[0055] 50g of the crude product of the elacycline intermediate, 200ml of isopropyl ether and 100ml of n-hexane were added to a reaction bottle, stirred, heated, stirred and dissolved, cooled to -10°C within 6 hours, stirred and crystallized for 3 hours, filtered, and dried at 35°C for 2 hours to obtain the pure elacycline intermediate. The product is a needle-shaped yellow crystalline solid with a mass yield of 88.0%, a purity of 99.17%, K4a of 0.25%, K4 of 0.17%, benzyl chloride of 0.05%, K3 of 0.17%, chiral impurities of 0.21% and water of 0.02%.

[0056] Example 6. Purification of crude elacycline intermediate

[0057] 50g of the crude product of the elacycline intermediate, 150ml of isopropyl ether and 300ml of n-hexane were added to a reaction bottle, stirred, heated, stirred and dissolved, cooled to -10°C within 6 hours, stirred and crystallized for 3 hours, filtered, and dried at 35°C for 2 hours to obtain the pure elacycline intermediate. The product is a needle-shaped yellow crystalline solid with a mass yield of 89.1%, a purity of 99.05%, K4a of 0.34%, K4 of 0.20%, benzyl chloride of 0.05%, K3 of 0.25%, chiral impurities of 0.29% and water of 0.02%.

[0058] Example 7. Purification of crude elacycline intermediate

[0059] 50g of the crude product of the elacycline intermediate, 200ml of isopropyl ether and 100ml of n-hexane were added to a reaction bottle, stirred, heated, stirred and dissolved, cooled to -10°C within 5 hours, stirred and crystallized for 3 hours, filtered, and dried at 35°C for 2 hours to obtain the pure elacycline intermediate. The product is a needle-shaped yellow crystalline solid, with a mass yield of 89.3.0%, a purity of 99.52%, K4a of 0.16%, K4 of 0.10%, no benzyl chloride detected, K3 of 0.10%, chiral impurities of 0.15%, and water of 0.02%.

[0060] Comparative Example 1

[0061] Repeat according to the method of Org.Process Res.Dev.2015,19,1784-1795.

[0062] 50 g of the crude intermediate of elacycline and 135 ml of isopropanol were added to a reaction bottle, stirred, and heated to 45±5°C. 90 ml of water was added dropwise within 5 hours. After the addition was completed, seed crystals were added and stirred for 30 minutes. No solid was precipitated and the seed crystals were dissolved. 45 ml of water was added dropwise within 5 hours at 45±5°C. After the addition was completed, seed crystals were added and stirred for 30 minutes. No solid was precipitated. The temperature was lowered to 35°C. The product precipitated as oil. The mixture was separated into layers. Seed crystals were added and stirred for 2 hours. The solid content increased significantly. The temperature was naturally lowered and stirred overnight. The temperature was then lowered to 0°C and stirred for 5 hours. The mixture was filtered and dried at 45°C for 24 hours. The moisture content was 1.0%. The mixture was further dried for 12 hours. The moisture content was 0.23%. The mixture was further dried for 12 hours to obtain a pure intermediate of elacycline. The water content of the elacycline intermediate pure product is 0.10%, the property is a needle-shaped yellow crystalline solid, the mass yield is 80.4%, the purity is 96.50%, K4a is 1.24%, K4 is 0.27%, benzyl chloride is 0.86%, K3 is 1.13%, and the chiral impurity is 0.33%.

[0063] It can be seen from Examples 1 to 7 that the refining method of the present invention has a short refining operation time and can be completed in about 10 hours. The sample obtained can be dried for 2 hours and the moisture content can be less than 0.05%. There is no introduction of other proton solvents, which will not affect the anhydrous reaction in the subsequent process. The purity can be increased to more than 99.0%, the single impurity can be less than 0.5%, the chiral impurity can be less than 0.3%, the moisture content is less than 0.05%, the process is mild, the operation is simple, and it is convenient for large-scale application.

Claims

1. A method for purifying an elacycline intermediate, characterized in that: The crude product of eracycline intermediate is crystallized by using a mixed solvent of a readily soluble organic solvent and an inert organic solvent to obtain a pure product of eracycline intermediate; the readily soluble organic solvent includes any one of isopropyl ether and methyl tert-butyl ether or a mixture of the two; the inert organic solvent includes any one or more of petroleum ether, n-hexane and n-heptane; the structural formula of the eracycline intermediate is shown in Formula I; 2. The method according to claim 1, characterized in that: The volume ratio of the readily soluble organic solvent to the inert organic solvent is 1:0.5 to 1:

2.

3. The method according to claim 1, characterized in that The usage ratio of the crude elacycline intermediate product and the readily soluble organic solvent is 1g:2mL to 1g:5mL.

4. The method according to claim 1, characterized in that: The crystallization time is 2h-4h.

5. The method according to claim 1, characterized in that The crude elacycline intermediate product is mixed with a solvent, heated and dissolved, and then crystallized.

6. The method according to claim 1, characterized in that After the crystallization step, the product is filtered and dried at 30-40° C. for 1.5-3 hours to obtain a pure intermediate of eracycline.

7. The method according to claim 1, characterized in that The refining method comprises adding the crude product of eracycline intermediate into a mixed solvent of the soluble organic solvent and the inert organic solvent, dissolving, and crystallizing to obtain a pure product of eracycline intermediate; And / or the crude elacycline intermediate is first dissolved in the readily soluble organic solvent, then mixed with the inert organic solvent, and crystallized to obtain a pure elacycline intermediate.

8. The method according to claim 7, characterized in that The crystallization is performed by cooling the temperature to -20°C to 10°C.

9. The method according to claim 7, characterized in that: The solution is cooled to -20°C to 10°C within 4-6 hours to crystallize.

10. A solvent composition for refining an elacycline intermediate, characterized in that: The solvent composition comprises a soluble organic solvent and an inert organic solvent; the soluble organic solvent comprises any one of isopropyl ether and methyl tert-butyl ether or a mixture of the two; the inert organic solvent comprises any one or more of petroleum ether, n-hexane and n-heptane.

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