High-selectivity synthesis method of amikacin sulfate

Abstract

Aiming at the defects of incomplete protection of kanamycin A, more acylation side reactions, poor suitability with a microchannel reactor and the like in the existing silanization protection process, the invention provides the high-selectivity synthesis method of amikacin sulfate. According to the method, breakthrough is achieved through an improved route of silanization full protection, directional deprotection and microchannel acylation, and full protection of seven hydroxyl groups and four amino groups of kanamycin A is achieved by combining hexamethyldisilazane with a high-boiling-point solvent; due to spatial position and activity differences of four amino groups, a solvent containing a small amount of water is used for directionally removing a trimethylsilyl protecting group of a 1-position amino group; the particle size of the active ester is controlled to be smaller than or equal to 100 microns through high-speed stirring, and high-selectivity acylation is completed in the micro-channel reactor. According to the method, the ratio of the 1-position acylation product to the 3-position acylation product is increased to 20: 1 or above, the synthesis yield reaches 75% or above, and the method is suitable for industrial continuous production.

Description

Technical Field

[0001] This invention belongs to the field of pharmaceutical chemical synthesis technology, specifically relating to a highly selective synthesis method for amikacin sulfate. Background Technology

[0002] Amikacin sulfate (also known as amikacin) is a first-line broad-spectrum aminoglycoside antibiotic in clinical practice. It has significant activity against sensitive bacteria such as Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, as well as most aminoglycoside-resistant strains. Its sulfate form has been included in the National Essential Medicines List and the National Basic Medical Insurance and Work Injury Insurance Drug List (Category A) and is widely used in the clinical treatment of serious infections such as pyelonephritis, respiratory tract infections, and sepsis.

[0003] Currently, the mainstream industrial synthesis process of amikacin still uses kanamycin A as the starting material, and the core route is: silanization protection - preparation of active ester - acylation - hydrolysis - hydrazolysis, and the specific reaction equations are as follows.

[0004] Silanization reaction:

[0005] Esterification reaction:

[0006] Acylation reaction:

[0007] Hydrolysis reaction:

[0008] Hydrazolysis reaction:

[0009] To address the shortcomings of mainstream processes, several existing patents have proposed improved schemes, forming synthetic routes with distinct characteristics, as follows: 1) Some patents (such as CN106866755B and CN110577558A) employ a "partial silanization protection" strategy, protecting only all hydroxyl groups and the 6'' amino group of kanamycin A, while retaining the 1- and 3-position amino groups for directional acylation, thus avoiding the long reaction time of full silanization; 2) Some patents (such as CN110577558A and CN105440090B) introduce 4-N,N-dimethylpyridine (DMAP) or use 1-hydroxybenzotriazole (HOBT) as an acylation catalyst, combined with DCC. 3) Some patents (such as CN106866755B, CN105440090B, CN108976267B) omit the separate preparation step of active ester and use silanized products to directly acylate with PHBA, avoiding the use of NOP and reducing the harm to employees' health; 4) Other patents (such as CN111233952A) use mercaptobenzothiazole to activate the carboxyl group to achieve reagent recovery and reuse, or (such as CN105254687A) replace the side chain raw material with 2(S)-2-hydroxy-4-carbamoylbutyric acid and use sodium hypochlorite degradation instead of hydrazine hydrolysis to avoid the generation of phthaloyl hydrazine solid waste.

[0010] However, both mainstream industrial processes and existing improved patent synthetic routes still have many unresolved technical drawbacks: 1) Insufficient silanization protection efficiency: mainstream processes and some improved routes suffer from incomplete protection, leading to the easy exposure of the 3-position amino group of kanamycin A, which competes with the target amino group at the 1-position for acylation, generating a large number of byproducts (the ratio of 1-position to 3-position acylated products is only about 3:1), increasing the difficulty and cost of post-processing; 2) The acylation catalyst DMAP introduced in some patents contains an N,N-dimethylpyridine ring in its chemical structure, which has potential mutagenicity. As a catalyst for drug synthesis intermediates, DMAP residues are difficult to completely remove by conventional separation methods, requiring the establishment of stringent quality control standards and detection methods. This increases product quality risks and the difficulty of controlling industrial production; in addition, there are problems such as high cost of special reagents (such as mercaptobenzothiazole) or complex recovery processes; 3) Limited adaptability of reaction conditions to industrialization, some improved routes require low temperature reaction (such as -15~-10℃) or precise control of flow acceleration rate, which increases energy consumption and equipment control difficulty, and the reaction yield of some routes is low (such as CN105254687A yield of only 64.0%~65.2%); 4) Poor adaptability to continuous production: the particle size of active ester particles prepared by mainstream processes and some patents is easy to exceed the standard (>100μm), which cannot be adapted to microchannel reactors, and only batch reaction can be used, resulting in low production efficiency, and the one-time conversion efficiency of kanamycin A is less than 65%.

[0011] Therefore, developing a method for synthesizing amikacin sulfate that can achieve full protection of kanamycin A, directional acylation, and adaptable continuous production, while properly controlling the risk of catalyst mutation and taking into account environmental protection and cost advantages, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0012] To address the shortcomings of existing silanization protection processes, such as incomplete protection of kanamycin A, numerous acylation side reactions, and poor compatibility with microchannel reactors, this invention provides a highly selective synthesis method for amikacin sulfate. This method increases the ratio of the 1-position acylated product to the 3-position acylated product from 3:1 to over 20:1. Due to the significantly improved selectivity for 1-position amino acylation of kanamycin A, the synthesis yield reaches over 75%, making it suitable for continuous industrial production and compatible with existing production lines, resulting in significant cost advantages.

[0013] The core objective of this invention is to overcome the defects of existing processes and specifically solve the following four key problems: 1) to achieve complete protection of the seven hydroxyl groups and four amino groups of kanamycin A, avoiding exposure of the amino group at the 3-position from the source; 2) to directionally remove the TMS (silanization) protecting group of the amino group at the 1-position, ensuring that the acylation reaction occurs only at the target site; 3) to control the particle size of the active ester to adapt to the microchannel reactor and achieve continuous production; 4) to improve the one-time conversion efficiency of kanamycin A and reduce the cost of by-product recovery.

[0014] The technical solution of this invention is: a highly selective synthesis method for amikacin sulfate, based on the synergistic design of "protecting group selectivity regulation and parameter optimization", specifically including four core steps: (1) Full protection of silanization: The combination strategy of “acetonitrile pre-silanization + high boiling point solvent / HMDS (hexamethyldisilazane) reflux” is adopted. By utilizing the strong silanization ability of HMDS and the high boiling point characteristics of the solvent, the full protection of all hydroxyl and amino groups of kanamycin A is achieved. (2) Targeted deprotection: Utilizing the high sensitivity of the 1-position amino TMS protecting group to trace amounts of moisture, by precisely controlling the moisture content of acetone and the reaction temperature, only the 1-position amino TMS protecting group is removed, while other sites remain blocked. (3) Preparation of active ester: By rapidly adding DCC and stirring at high speed, the mixture of active ester and DCU is dispersed into particles with a particle size ≤100μm, which avoids microchannel blockage and increases the contact area of ​​raw materials. (4) Microchannel acylation: In the microchannel, the feed flow rate of the silane solution and the active ester solution is controlled to make the silane (only 1 reaction site) slightly excess, so as to ensure that the active ester fully participates in the 1-position amino acylation and eliminates the polyacylation side reaction.

[0015] The technical solution of this invention is: a highly selective synthesis method for amikacin sulfate, characterized in that, Silanization reaction:

[0016] 1-N-Detrimethylsilylation reaction:

[0017] Esterification reaction:

[0018] Acylation reaction:

[0019] Specifically, the following steps are included: (1) Fully protected silanization: Take kanamycin A, use acetonitrile as solvent, add hexamethyldisilazane and a small amount of trimethylchlorosilane to carry out silanization reaction; after the reaction is completed, distill off the acetonitrile under reduced pressure, add a high-boiling-point solvent, continue to reflux the reaction, and after the reaction is completed, distill off the solvent to obtain the fully protected silanized product. (2) Targeted deprotection: Add acetone containing 0.1% to 0.5% water to the fully protected silanized product of step (1) and deprotect at 0 to 30°C to obtain a solution of kanamycin silanized intermediate with only the amino group at position 1 exposed. (3) Preparation of active ester: Take γ-phthalimino-α-hydroxybutyric acid (PHBA) and N-hydroxyphthalimide (NOP), use acetone as solvent, add DCC within 1~5 min, and carry out esterification reaction by stirring at high speed to obtain a particulate active ester solution with a particle size ≤100μm. (4) Microchannel acylation: The silanization intermediate solution from step (2) and the active ester solution from step (3) are introduced into a microchannel reactor at a molar flow rate ratio of 1.04~1.06:1 for acylation reaction. After the reaction, the amikacin sulfate is obtained by acid hydrolysis, hydrolysis, hydrazine hydrolysis, salt formation and crystallization.

[0020] Furthermore, in step (1), the silanization reaction in acetonitrile is carried out under reflux for 6-8 hours, the molar ratio of hexamethyldisilazane to kanamycin A is 6-20:1, and a trace amount of trimethylchlorosilane is used, preferably in a volume ratio of 1:200 with hexamethyldisilazane.

[0021] Furthermore, in step (1), after the reaction is completed, acetonitrile is removed by vacuum distillation. The high-boiling solvent added is one or a mixture of 1,4-dioxane, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), toluene, o-xylene, m-xylene, p-xylene or dimethyl sulfoxide (DMSO), and the amount used is 1 to 10 times the weight of kanamycin A.

[0022] Furthermore, in step (2), the reaction time is 5 to 60 minutes.

[0023] Furthermore, the stirring speed in step (3) is 1000~2000 r / min. The molar ratio of PHBA, NOP and DCC is 1.0~1.5:1.0~1.5:1.

[0024] Furthermore, in step (4), the reaction temperature of the microchannel reactor is -10℃ to 50℃, the residence time of the raw materials is 20s to 100s, and after passing through the microchannel reactor, the raw materials enter the reaction tank and continue to react for 20min to 180min under nitrogen protection.

[0025] Compared with the prior art, the beneficial effects of the present invention are reflected in the following four aspects: 1. Significantly improved selectivity of acylated products: The ratio of 1-position to 3-position acylated products was optimized from 3:1 to over 20:1, and by-products were significantly reduced, greatly reducing the difficulty of post-processing; 2. Suitable for continuous production: The active ester particle size is ≤100μm, which can stably pass through the microchannel reactor, enabling continuous production; 3. Significant industrial advantages: high conversion efficiency, no need for mutagenic catalysts, low product quality risk; mild reaction conditions, low energy consumption and equipment control difficulty; can be integrated with existing production lines, significant cost advantage, synthesis yield of over 75%. Attached Figure Description

[0026] Figure 1 The detection spectra of the 1-position acylated product and the 3-position acylated product in the example are shown. Detailed Implementation

[0027] The effects are illustrated below with reference to specific examples.

[0028] Example 1: (1) Weigh 48.5 g (0.1 mol) of pure kanamycin A, add 460 ml acetonitrile, 200 ml hexamethyldisilazane and 1 ml trimethylchlorosilane, and reflux for 6 hours; after the reaction is completed, distill under reduced pressure until no obvious liquid distills out, add 100 ml toluene, continue to reflux for 4 hours, remove toluene by distillation under reduced pressure to obtain fully protected silane; (2) Add 920 ml of acetone containing 0.2% water to the silanized product after distillation to remove toluene, control the temperature at 20~30℃, react for 30 min, and continue to cool down to 0℃ for later use to obtain an acetone solution of kanamycin silanization intermediate with only the amino group exposed at position 1. (3) Add 27.4g of α-hydroxy-γ-phthalimide butyric acid, 20g of N-hydroxyphthalimide and 600ml of acetone to a 500ml three-necked flask, stir for 30 minutes until completely dissolved, cool to 10℃~15℃, increase the rotation speed to 1500r / min, add 50ml of acetone solution containing 19.4g of DCC within 5 minutes, and continue the reaction for 30 minutes to obtain an active ester solution (after drying, the particle size is ≤100μm). (4) Control the temperature of the microreactor to 10℃~15℃, and simultaneously introduce the kanamycin silane / acetone solution from step (2) and the active ester solution from step (3) into the microreactor. The flow rate is controlled according to the molar ratio of active ester (calculated as α-hydroxy-γ-phthalimide butyric acid) to kanamycin silane at 1:1.05, and the residence time is 100s. After the reaction, the material enters a three-necked flask under nitrogen protection and continues to react at 10~15℃ for 50min to obtain the acylated product.

[0029] The above-mentioned solution was hydrolyzed with a small amount of water and dilute hydrochloric acid. After the reaction was completed, the hydrolysis products were separated. The solution was cooled to 20°C, and 20.2 g of 80% hydrazine hydrate was added. The solution was then heated to reflux for 5 hours. After cooling, hydrochloric acid was added to adjust the pH to 4.0. The filtrate was filtered and the components were analyzed. The molar ratio of 1-position acylated product to 3-position acylated product was 24.5:1. The chromatogram is shown below. Figure 1 The above-mentioned liquid was subjected to column chromatography, concentration, and freeze-drying according to the scheme disclosed in Example 1 of patent CN106866755B to obtain 45.6g of amikacin (total yield 78%). Amikacin was then reacted with sulfuric acid to form a salt and crystallized (see Example 1 of CN103113429B), with a product purity of 99.1%.

[0030] Example 2: (1) Weigh 48.5 g (0.1 mol) of pure kanamycin A, add 460 ml acetonitrile, 200 ml hexamethyldisilazane and 1 ml trimethylchlorosilane, and reflux for 6 hours; after the reaction is completed, distill under reduced pressure until no obvious liquid distillation, add 100 ml N-methylpyrrolidone, and continue to reflux at 120 °C for 4 hours. Remove N-methylpyrrolidone by distillation under reduced pressure to obtain fully protected silane. (2) Add 920 ml of acetone containing 0.2% water to the silanized product after distillation to remove N-methylpyrrolidone, control the temperature at 20~30℃, react for 30 min, and continue to cool down to 0℃ for later use to obtain an acetone solution of kanamycin silanization intermediate with only the amino group exposed at position 1. (3) Add 27.4g of α-hydroxy-γ-phthalimide butyric acid, 20g of N-hydroxyphthalimide and 600ml of acetone to a 500ml three-necked flask, stir for 30 minutes until completely dissolved, cool to 10℃~15℃, increase the rotation speed to 1500r / min, add 50ml of acetone solution containing 19.4g of DCC within 5 minutes, and continue the reaction for 30 minutes to obtain an active ester solution (after drying, the particle size is ≤100μm). (4) Control the temperature of the microreactor to 10℃~15℃, and simultaneously introduce the kanamycin silane / acetone solution from step (2) and the active ester solution from step (3) into the microreactor. The flow rate is controlled according to the molar ratio of active ester (calculated as α-hydroxy-γ-phthalimide butyric acid) to kanamycin silane 1:1.06, and the residence time is 100s. After the reaction, the material enters a three-necked flask under nitrogen protection and continues to react at 10~15℃ for 50min to obtain the acylated product. The steps were the same as in Example 1. After filtration, the components of the filtrate were analyzed. The ratio of acylated product at position 1 to acylated product at position 3 was 24.0:1. 46.5g of amikacin was obtained, with a total yield of 79.5%. The amikacin sulfate prepared further had a purity of 99.4%.

[0031] Example 3: (1) Weigh 48.5 g (0.1 mol) of pure kanamycin A, add 460 ml acetonitrile, 200 ml hexamethyldisilazane and 1 ml trimethylchlorosilane, and reflux for 6 hours; after the reaction is completed, distill under reduced pressure until no obvious liquid distills out, add 100 ml toluene, continue to reflux for 4 hours, remove toluene by distillation under reduced pressure to obtain fully protected silane; (2) Add 800 ml of acetone containing 0.3% water to the silanized product after distillation to remove toluene, control the temperature at 20~30℃, react for 30 min, and continue to cool down to 0℃ for later use to obtain an acetone solution of kanamycin silanization intermediate with only the amino group exposed at position 1. (3) Add 27.4g of α-hydroxy-γ-phthalimide butyric acid, 20g of N-hydroxyphthalimide and 600ml of acetone to a 500ml three-necked flask, stir for 30 minutes until completely dissolved, cool to 10℃~15℃, increase the rotation speed to 2000r / min, add 50ml of acetone solution containing 19.4g of DCC within 5 minutes, and continue the reaction for 30 minutes to obtain an active ester solution (after drying, the particle size is ≤100μm). (4) Control the temperature of the microreactor at 10℃~15℃, and simultaneously introduce the kanamycin silane / acetone solution from step (2) and the active ester solution from step (3) into the microreactor. The flow rate is controlled according to the molar ratio of the active ester (calculated as α-hydroxy-γ-phthalimide butyric acid) to the kanamycin silane at 1:1.04, and the residence time is 100s. After the reaction, the material enters a three-necked flask under nitrogen protection and continues to react at 10~15℃ for 50min to obtain the acylated product. The procedure was the same as in Example 1. After filtration, the components of the filtrate were analyzed. The ratio of acylated product at position 1 to acylated product at position 3 was 22.6:1. 44.4 g of amikacin was obtained, with a total yield of 75.9%. The amikacin sulfate prepared further had a purity of 99.1%.

Claims

1. A highly selective method for the synthesis of amikacin sulfate, characterized in that, Specifically, the following steps are included: (1) Fully protected silanization: Take kanamycin A, use acetonitrile as solvent, add hexamethyldisilazane and a small amount of trimethylchlorosilane to carry out silanization reaction; after the reaction is completed, distill off the acetonitrile under reduced pressure, add a high-boiling-point solvent, continue to reflux the reaction, and after the reaction is completed, distill off the solvent to obtain the fully protected silanized product. (2) Targeted deprotection: Add acetone containing 0.1% to 0.5% water to the fully protected silanized product of step (1) and deprotect at 0 to 30°C to obtain a solution of kanamycin silanized intermediate with only the amino group at position 1 exposed. (3) Preparation of active ester: Take γ-phthalimino-α-hydroxybutyric acid and N-hydroxyphthalimide, use acetone as solvent, add DCC within 1~5 min, and carry out esterification reaction by stirring at high speed to obtain an active ester solution with particles ≤100μm in diameter. (4) Microchannel acylation: The kanamycin silanization intermediate solution from step (2) and the active ester solution from step (3) are introduced into a microchannel reactor at a molar flow rate ratio of 1.04~1.06:1 to carry out the acylation reaction. After the reaction, the amikacin sulfate is obtained by acid hydrolysis, hydrolysis, hydrazine hydrolysis, salt formation and crystallization.

2. The synthesis method as described in claim 1, characterized in that, The silanization reaction in step (1) in acetonitrile is carried out under reflux for 6-8 hours.

3. The synthesis method as described in claim 1, characterized in that, In step (1), the high-boiling solvent is one or a mixture of 1,4-dioxane, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, toluene, o-xylene, m-xylene, p-xylene or dimethyl sulfoxide.

4. The synthesis method as described in claim 1, characterized in that, In step (2), the reaction time is 5 to 60 minutes.

5. The synthesis method as described in claim 1, characterized in that, The stirring speed in step (3) is 1000~2000 r / min.

6. The synthesis method as described in claim 1, characterized in that, In step (4), the reaction temperature of the microchannel reactor is -10℃ to 50℃, and the residence time of the raw materials is 20s to 100s.

7. The synthesis method according to any one of claims 1-6, characterized in that, In step (4), after passing through the microchannel reactor, the mixture enters the reaction vessel and continues to react for 20 min to 180 min under nitrogen protection.

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