Preparation method of glucosamine derivative

Abstract

The present invention relates to a process for the preparation of the glucosamine derivative 2-N-4, 6-di-O-tributyryl-D-glucosamine. The method is carried out according to the following reaction process, and comprises the following steps: in the presence of alkali, a compound shown in a formula 1 reacts with benzyl bromide to obtain a compound shown in a formula 2, and the alkali is selected from one or more of sodium tert-amyl alkoxide, potassium tert-butoxide and sodium hydroxide; in the presence of acid, carrying out ring-opening reaction on the compound in the formula 2 to obtain a compound in a formula 3; reacting the compound of formula 3 with an esterification reagent to obtain a compound of formula 4; and carrying out a debenzylation reaction on the compound in the formula 4 to obtain the 2-N-4, 6-di-O-tributyryl-D-glucosamine. The preparation method can be carried out at lower cost, and meanwhile, the preparation method is mild in reaction condition, simple in post-treatment, high in product purity and suitable for industrial production.

Description

Technical Field

[0001] This invention relates to a method for preparing glucosamine derivatives, and more particularly to a method for preparing 2-N-4,6-di-O-tributyryl-D-glucosamine. Background Technology

[0002] Glucosamine, also known as glucosamine, is a compound formed by replacing one of the hydroxyl groups of glucose with an amino group. Glucosamine is an important precursor in the glycosylation of proteins and lipids and is one of the most abundant monosaccharides in nature. Typical glucosamine compounds include N-acetylglucosamine (GlcNAc) and N-butyrylglucosamine (GlcNBu). GlcNAc is a monomer of chitin and is considered to have anti-inflammatory, antitumor, and antioxidant effects, with wide applications in food, medicine, and cosmetics. Some studies have also shown that GlcNBu has therapeutic potential in bone and joint diseases.

[0003] Prodrug derivatives of glucosamine have been developed to enhance or improve their efficacy in treating bone and joint diseases (such as osteoporosis, arthritis, etc.) by improving bioavailability, stability and reducing the metabolism of the compound, such as 2-N-4,6-di-O-tributyryl-D-glucosamine disclosed in patent document CN109929001A.

[0004] The synthesis method for 2-N-4,6-di-O-tributyryl-D-glucosamine disclosed in CN109929001A uses the relatively dangerous NaH reagent, which is not conducive to scale-up production. Furthermore, the reaction product requires column chromatography purification, resulting in high overall production costs and cumbersome operation, making it unsuitable for industrial production. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing methods for synthesizing glucosamine derivatives, especially 2-N-4,6-di-O-tributyryl-D-glucosamine, which are unsuitable for large-scale production and have high production costs. Instead, it provides a method for preparing glucosamine derivatives. This method can produce glucosamine derivatives at a lower cost, with high yield and high product purity, and has promising prospects for industrial production.

[0006] This invention provides a method for preparing 2-N-4,6-di-O-tributyryl-D-glucosamine. The method is carried out according to the reaction route shown below, specifically including the following steps:

[0007]

[0008] Step 1: In the presence of a base, react the compound of Formula 1 with benzyl bromide to obtain the compound of Formula 2, wherein the base is selected from one or more of sodium tert-amyl alcohol, potassium tert-butoxide, and sodium hydroxide.

[0009] Step 2: In the presence of an acid, the compound of formula 2 undergoes a ring-opening reaction to obtain the compound of formula 3;

[0010] Step 3 involves reacting the compound of formula 3 with an esterifying agent to obtain the compound of formula 4; and

[0011] Step 4 involves subjecting the compound of formula 4 to a debenzylation reaction to obtain 2-N-4,6-di-O-tributyryl-D-glucosamine.

[0012] In some embodiments, the method further includes the following steps:

[0013]

[0014] Step A involves reacting the compound of Formula 6 with benzaldehyde or benzaldehyde diacetate to obtain the compound of Formula 1. In some embodiments, the molar ratio of benzaldehyde or benzaldehyde diacetate to the compound of Formula 6 is preferably 1.1:1 to 2:1, more preferably 1.4:1 to 1.7:1. In some preferred embodiments, the compound of Formula 6 is reacted with benzaldehyde diacetate, wherein the molar ratio of benzaldehyde diacetate to the compound of Formula 6 is 1.4:1 to 1.5:1.

[0015] In some embodiments, step A is typically carried out in a solvent in the presence of a catalyst. In some specific embodiments, the catalyst for step A is preferably p-toluenesulfonic acid, the solvent is preferably DMF, and the reaction temperature is preferably 40°C to 70°C.

[0016] In some embodiments, step 1 is carried out in a solvent at a reaction temperature of -15°C to 25°C, preferably -5°C to 5°C, wherein the solvent is preferably selected from one or more of N,N-dimethylformamide (DMF), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), dichloromethane (DCM), and toluene. In some embodiments, the solvent is DMF and THF, and the volume ratio of DMF to THF is preferably 2:3 to 3:2, for example, 11:9.

[0017] In some embodiments, in step 1, the molar ratio of benzyl bromide to the compound of formula 1 may be 3.0:1 to 2.0:1, preferably 2.5:1 to 2.1:1.

[0018] In step 1), the molar ratio of the base to the compound of formula 1 can be 3.0:1 to 2.0:1, preferably 2.4:1 to 2.6:1, for example 2.5:1.

[0019] In some embodiments, conventional monitoring methods for such reactions in the art (e.g., TLC, HPLC, or NMR) can be used to monitor the reaction progress in step 1. For example, the reaction endpoint is defined as the complete reaction of compound 1 (content ≤ 1%). In some embodiments, the reaction time for step 1 can be from 2 hours to 18 hours.

[0020] In some embodiments, the method of this application further includes: after step 1, performing a first post-processing, optionally including but not limited to one or more of concentration, filtration, washing, drying, and recrystallization. In some specific embodiments, the first post-processing includes: adding water to the system for slurrying, then filtering, washing the filter cake with water and filtering again, and drying. In another specific embodiment, the first post-processing includes: adding water to the system for slurrying, then filtering, washing the filter cake with water and filtering again, drying, recrystallizing, filtering, washing with n-heptane, and drying. In one specific embodiment, recrystallization may include: mixing the solid, n-heptane, and dichloromethane, heating to 35°C–45°C, stirring at this temperature for 2–5 hours, then cooling to 10°C–25°C, and holding at this temperature for crystallization for 1–2 hours. In one specific embodiment, drying may be carried out at a temperature of 40°C–50°C.

[0021] In some embodiments, in step 2, the acid is hydrochloric acid, acetic acid, or sulfuric acid. In some embodiments, the acid is hydrochloric acid or acetic acid, and the volume ratio (V:V) of the acid to water corresponding to the mass of the compound of Formula 2 is 0.4:1 to 2.5:1, preferably 1.7:1 to 2.5:1, for example 2.1:1. In some embodiments, the acid is sulfuric acid, and the volume ratio of the acid to water corresponding to the mass of the compound of Formula 2 is 0.2:1 to 1.25:1, preferably 0.8:1 to 1.25:1, for example 1.05:1. In some embodiments, step 2 is carried out in the presence of hydrochloric acid or sulfuric acid at a reaction temperature of -10°C to 10°C, preferably 0°C to 10°C, more preferably 2°C to 8°C. In another embodiment, step 2 is carried out in the presence of acetic acid at a reaction temperature of 70°C to 80°C. In some embodiments, the reaction in step 2 is carried out in a solvent, which preferably includes acetonitrile and / or water, and preferably further includes one or more of toluene, dichloromethane, and n-heptane. In some specific embodiments, the solvent is acetonitrile and toluene, or acetonitrile and dichloromethane.

[0022] In some embodiments, conventional monitoring methods for such reactions in the art (e.g., TLC, HPLC, or NMR) can be used to monitor the reaction progress in step 2. For example, the reaction endpoint is defined as the complete reaction of the compound of formula 2 (content ≤ 1%).

[0023] In some embodiments, the reaction in step 2 can be quenched using an alkali, wherein the alkali is preferably selected from one or more of sodium carbonate, potassium carbonate, and sodium bicarbonate, more preferably sodium carbonate. In some embodiments, the molar ratio of the quenching alkali to the compound of formula 2 is preferably 1.0:1 to 2.0:1, more preferably 1.2:1 to 1.4:1. In some embodiments, the quenching temperature is preferably 0°C to 25°C, more preferably 0°C to 10°C. In one specific embodiment, the quenching includes: mixing the system with an alkali and stirring at 0°C to 10°C for 0.5 hours to 1 hour.

[0024] In some embodiments, the method of this application further includes: after quenching the reaction in step 2, a second post-processing is performed, optionally including but not limited to one or more of concentration, filtration, washing, drying, and recrystallization. In some specific embodiments, the second post-processing includes: vacuum concentration, suction filtration, washing the filter cake with water and drying, recrystallizing and then suction filtration, washing with n-heptane, and drying. In one specific embodiment, the recrystallization may include: mixing the filter cake with a solvent, heating to 35°C–40°C and stirring for 2–3 hours, cooling to 10°C–20°C, and maintaining the temperature for crystallization for 1–2 hours. In one specific embodiment, the solvent used is dichloromethane, or a mixture of dichloromethane and n-heptane. In one specific embodiment, drying may be carried out at a temperature of 40°C–50°C.

[0025] In some embodiments, in step 3, the esterifying agent is a reagent capable of reacting with the compound of formula 3 to form a compound having a butyrate ester structure. Optionally, the esterifying agent is butyric anhydride, butyryl chloride, or butyryl bromide, preferably butyric anhydride. The molar ratio of the esterifying agent to the compound of formula 3 is preferably 3.0:1 to 2.0:1, more preferably 2.5:1 to 2.1:1, for example 2.2:1.

[0026] In some embodiments, step 3 may be carried out in the presence of a catalyst, preferably pyridine and / or 4-dimethylaminopyridine (DMAP). In some embodiments, the catalyst is pyridine and 4-dimethylaminopyridine, optionally with a molar ratio of 4-dimethylaminopyridine to the compound of formula 3 of 0.01:1 to 0.05:1, and preferably 3:1 to 6:1, for example 5.4:1. In some embodiments, in step 3, the catalyst and butyric anhydride may be added at 15°C to 25°C. In some embodiments, step 3 may be carried out at a reaction temperature of 30°C to 40°C. In some embodiments, the reaction in step 3 is carried out in a solvent, preferably acetonitrile.

[0027] In some embodiments, conventional monitoring methods for such reactions in the art (e.g., TLC, HPLC, or NMR) can be used to monitor the reaction progress in step 3. For example, the complete conversion of compound 3 (content ≤1%) is used as the reaction endpoint. In some embodiments, the reaction time for step 3 can be 2 to 6 hours.

[0028] In some embodiments, the method of this application further includes: after step 3, performing a third post-processing, which optionally includes, but is not limited to, quenching, concentration, filtration, washing, drying, and recrystallization. In some specific embodiments, the third post-processing includes: adding sodium bicarbonate solution to the system, stirring to induce crystallization for 2 to 4 hours, filtering, washing the filter cake with water and n-heptane, and drying.

[0029] In some embodiments, step 4 is carried out by hydrogenation debenzylation. In some specific embodiments, step 4 is carried out in the presence of acid by palladium hydrogenation on carbon at a reaction temperature of 40°C to 50°C.

[0030] In some embodiments, step 4 is carried out by oxidative debenzylation. In some specific embodiments, step 4 is carried out using sodium bromate (NaBrO3) and sodium dithionite (Na2S2O4) at a reaction temperature of 20°C to 30°C. In some embodiments, the molar ratio of sodium bromate, sodium dithionite, and the compound of formula 4 in step 4 is preferably 1.7:1.3:1.0 to 3.0:2.5:1.0, for example, 2.7:2.25:1.0. By using sodium bromate and sodium dithionite for debenzylation, the resulting product has a low content of unknown impurities and high purity (HPLC purity above 95%).

[0031] In some embodiments, step 4 is carried out in a solvent, wherein the solvent used is preferably an ester solvent (e.g., ethyl acetate, isopropyl acetate (IPAc) or water).

[0032] In some embodiments, the method of this application further includes: after step 4, a fourth post-processing is performed, optionally including, but not limited to, one or more of separation, extraction, concentration, filtration, washing, drying, and recrystallization. The fourth post-processing includes: separating the organic phase, extracting the aqueous phase with isopropyl acetate, combining the organic phases, and drying to obtain a crude product; refining the crude product: mixing the crude product, toluene, and an aqueous solution of calcium acetate, stirring at 0°C to 30°C to crystallize for 1 to 2 hours, and then filtering; optionally, repeating the purification process 1 to 2 times with the filter cake, then mixing the obtained solid with ethyl acetate, adding n-heptane at 0°C to 30°C, maintaining the temperature to crystallize for 1 to 2 hours, filtering, and drying. In one specific embodiment, drying can be carried out at a temperature of 35°C to 45°C.

[0033] The preparation method of this invention features mild reaction conditions, simple post-processing, high product purity, and the ability to produce the glucosamine derivative 2-N-4,6-di-O-tributyryl-D-glucosamine on a large scale at a low cost, with high product yield and promising prospects for industrial production.

[0034] It should be understood that, within the scope of this invention, the above-described technical features and the technical features specifically described below (such as in the detailed embodiments) can be combined with each other to form new or preferred technical solutions. These will not be elaborated upon here. Detailed Implementation

[0035] To provide a clear and consistent understanding of the terminology used in this specification, some definitions are provided below. Furthermore, unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0036] When used in conjunction with the term "comprising" in the claims and / or description, the word "a" can mean "one," but it also aligns with the meanings of "one or more," "at least one," and "one or more." Similarly, the word "another" can mean at least a second or more.

[0037] As used in this specification and claims, the words “comprising” (and any form of inclusion, such as “comprising” and “including”), “having” (and any form of having, “having,” “including,” and “containing”) are inclusive and open-ended and do not exclude additional unlisted elements or processing steps. The terms “about” or “approximately” are used to indicate that the value includes errors introduced by the instruments and methods used in determining the value.

[0038] In the following examples, the amount of some compounds is expressed as "eq". "1eq" means the amount of compound used relative to the equimolar amount of the reactants in this step.

[0039] In the following examples, the amount of solvent used is expressed as "V". "1V" means the volume of water relative to the same mass of the reactants in that step. The volume and mass of the solvent used in each step can be known from common knowledge in the art.

[0040] To better understand the present invention and to more clearly demonstrate how to implement it, features of embodiments according to the present invention are now illustrated by way of example.

[0041] Example

[0042] The invention will be more readily understood by referring to the following embodiments, which are used to illustrate the invention and should not be construed as limiting the scope of the invention in any way.

[0043] Unless otherwise defined or the context clearly requires, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should be understood that any methods and materials similar to or equivalent to those described in this application may be used in the practice or testing of this invention. Unless otherwise stated, all materials and instruments used in this application are commercially available.

[0044] In the following examples, HPLC purity was determined by area normalization, and HPLC content was determined by external standard method.

[0045] Moisture content test method: KF volumetric method.

[0046] Preparation Example 1: Preparation of Compound 1

[0047] 230 kg of compound formula 6 was dissolved in 10 V DMF, and 1.5 eq benzaldehyde dimethyl acetal and 0.04 eq p-toluenesulfonic acid monohydrate were added. The reaction was carried out at 45 °C–50 °C. When the content of compound formula 6 was ≤1%, 30 V water was added and stirred to induce crystallization. The crystals were filtered and dried below 60 °C to obtain 225.7 kg of compound formula 1 (yield 72.5%). The HPLC purity of compound formula 1 was determined to be 96.91%.

[0048] Preparation Example 2: Preparation of Compound 1

[0049] 220 kg of compound 6 was dissolved in 4 V of DMF, and 1.4 eq of benzaldehyde dimethyl acetal and 0.05 eq of p-toluenesulfonic acid monohydrate were added. The reaction was carried out at 60 °C to 70 °C. When the content of compound 6 was ≤1%, 12 V of water was added and stirred to induce crystallization. The mixture was filtered and dried at below 60 °C to obtain 235.2 kg of compound 1 (yield 79.0%).

[0050] Example 1: Preparation of 2-N-4,6-di-O-tributyryl-D-glucosamine (compound of formula 5)

[0051] Step 1: Dissolve 96.1 g of compound 1 in a mixture of 11 V DMF and 9 V THF, then add 2.1 eq benzyl bromide. Under nitrogen protection, slowly add sodium tert-amyloxide (2.5 eq) in small amounts several times, maintaining the temperature at -5 to 5 °C. Continue to maintain the temperature at -5 to 5 °C and stir until the concentration of compound 1 is ≤1% as measured by sampling. Then, slowly add 33 V water to the system and slurry for 1 h. Filter, wash the filter cake with purified water, filter again, and dry at 40 °C to 50 °C to obtain 143.34 g of compound 2 (net yield 94.6%). Analysis showed that the HPLC content of compound 2 in the filter cake was 95.37%, the water content of the product compound 2 was 0.47%, and the qNMR content was 97.20%.

[0052] Step 2: Add 7V acetonitrile and 5V toluene to 90.0g of compound 2. Then cool the system to 0-10℃ and slowly add 2.1V hydrochloric acid dropwise. After the addition is complete, continue to control the temperature at 0-10℃ and react until the sample shows that compound 2 is <3%. Then slowly add the system dropwise to a sodium carbonate solution (1.32 eq sodium carbonate and 17V purified water) and quench the reaction at 0-10℃. After the addition is complete, stir at the controlled temperature for 1h, concentrate under reduced pressure until there is no obvious layering, filter, wash the filter cake with 2V purified water, dry the filter cake at 40-50℃ until it meets the requirements, add the filter cake to 15V dichloromethane, heat to 35-40℃, stir for 3h, cool to 10-20℃, keep at the temperature for 2h to crystallize, filter, wash the filter cake with 1V n-heptane, dry the filter cake at 40-50℃, and obtain 63.24g of compound 3 (net yield 84.68%). The HPLC analysis showed that the content of compound 3 was 96.71%.

[0053] Step 3: Dissolve 50.0 g of compound 3 in 4V acetonitrile, add 1V pyridine, maintain the temperature at 15–25℃, add 0.05 eq DMAP, maintain the temperature at 15–25℃, slowly add 2.2 eq butyric anhydride, after the addition is complete, maintain the temperature at 30–40℃, and react for 2 h. Sampling is then performed until compound 3 is ≤1%. The reaction system is added dropwise to 15V 5.1% sodium bicarbonate solution to induce crystallization. Stirring is performed for 4 h, followed by filtration. The filter cake is washed with 4V purified water and 2V n-heptane, and then dried to obtain 66.0 g of compound 4 (net yield 98.98%). The HPLC purity of compound 4 is 98.15%, and the qNMR content is 99.46%.

[0054] Step 4: Dissolve 50.0 g of compound 4 in 10 V isopropyl acetate, maintain the temperature at 20–30 °C, add an aqueous solution of sodium bromate (2.7 eq / 10 V), and then add an aqueous solution of sodium dithionite (2.25 eq / 10 V) at 20–30 °C to carry out the reaction. After 16 hours of reaction, take a sample for LCMS analysis. The results show that the content of compound 5 in the system is 100%. After the reaction is completed, separate the organic phase, extract the aqueous phase with 2 V isopropyl acetate, combine the organic phases, dry and concentrate to obtain crude oil. Dissolve the crude oil in 10 V toluene, add an aqueous solution of calcium acetate (1.0 eq / 4 V), stir at 0–10 °C to crystallize for 1 hour, filter, repeat the purification once more, add 3 V ethyl acetate to dissolve the obtained solid, add 12 V n-heptane dropwise at 0–10 °C, crystallize for 1 hour, filter, and dry the filter cake at 40±5 °C to obtain 22.0 g of compound 5 (yield 65.67%). The HPLC purity of compound 5 was determined to be 98.54%.

[0055] Example 2

[0056] Except for adjusting the reaction conditions and / or post-treatment methods in step 1, the other steps are performed in the same manner as in Example 1.

[0057] Example 2.1

[0058] Except that the base used in step 1 is potassium tert-butoxide, the process is carried out in the same manner as in Example 1.

[0059] In step 1, the HPLC content of compound 2 in the filter cake was 82.70%.

[0060] Example 2.2

[0061] Except that the base used in step 1 is sodium hydroxide and the solvent is 14V DMF, the process is carried out in the same manner as in Example 1.

[0062] In step 1, the HPLC content of compound 2 in the filter cake was 72.89%.

[0063] Example 2.3

[0064] Except for controlling the temperature to 5°C to 15°C in step 1, the process is carried out in the same manner as in Example 1.

[0065] In step 1, the HPLC content of compound 2 in the filter cake was 88.55%.

[0066] Example 2.4

[0067] Except for controlling the temperature to 15°C to 25°C in step 1, the process is carried out in the same manner as in Example 1.

[0068] In step 1, the HPLC purity of compound 2 in the filter cake was 85.84%.

[0069] Example 2.5

[0070] In step 1, 126.3 kg of compound 1 was dissolved in a mixture of 11V DMF and 9V THF, followed by the addition of 2.1 eq benzyl bromide. Under nitrogen protection, potassium tert-butoxide (2.5 eq) was slowly added in small amounts multiple times. The temperature was maintained at -5 to 5°C, and the mixture was stirred until the concentration of compound 1 was ≤1% as measured by sampling. Then, 33V water was slowly added dropwise to the system, and the mixture was stirred for 1 hour. The mixture was filtered, and the filter cake was washed with purified water, filtered again, and dried at 40°C to 50°C. The solid, n-heptane, and dichloromethane were mixed, heated to 35°C to 45°C, and stirred for 2 to 5 hours. The mixture was then cooled to 10°C to 25°C and kept at this temperature for 2 hours to allow crystallization. After filtration, the crystals were washed with n-heptane and dried at 40°C to 50°C, yielding 148.8 kg of compound 2 (yield 76.6%). The HPLC purity of compound 2 was determined to be 97.1%.

[0071] Steps 2 through 4 are performed in the same manner as in Example 1.

[0072] Example 3

[0073] Except for adjusting the reaction conditions and / or post-treatment methods in step 2, the other steps are performed in the same manner as in Example 1.

[0074] Example 3.1

[0075] Except for step 2, where the amount of hydrochloric acid used is 2.5V, the solvent is 7V acetonitrile, the reaction temperature is 2℃~8℃, and the reaction time is 7 hours, the process is carried out in the same manner as in Example 1.

[0076] The HPLC content of the compound of formula 3 obtained in step 2 was found to be 70.17%.

[0077] Example 3.2

[0078] Except for step 2, where the amount of hydrochloric acid used is 1.5V, the solvent is 7V acetonitrile, and the reaction time is 2 hours, the process is carried out in the same manner as in Example 1.

[0079] The HPLC content of compound 3 in the system was found to be 68.46%.

[0080] Example 3.3

[0081] Except that in step 2, the solvent is a mixture of 7V acetonitrile and 8V DCM, the process is carried out in the same manner as in Example 1.

[0082] After quenching, the HPLC content of compound 3 in the filter cake was found to be 95.28%.

[0083] Example 3.4

[0084] Except that in step 2, the solvent is a mixture of 7V acetonitrile and 2V n-heptane, the process is carried out in the same manner as in Example 1.

[0085] After quenching, the HPLC content of compound 3 in the filter cake was found to be 90.73%.

[0086] Example 3.5

[0087] Except for step 2, in which the system is added dropwise to a sodium bicarbonate solution for quenching, the process is carried out in the same manner as in Example 1.

[0088] After quenching, the HPLC content of compound 3 in the filter cake was found to be 86.24%.

[0089] Example 3.6

[0090] Except for adding the system dropwise to the sodium carbonate solution in step 2 and then allowing it to return to room temperature naturally, the process was carried out in the same manner as in Example 1.

[0091] After quenching, the HPLC content of compound 3 in the filter cake was found to be 86.1%.

[0092] Example 4

[0093] Except for adjusting the reaction conditions and / or post-treatment methods in step 4, the other steps are performed in the same manner as in Example 1.

[0094] Example 4.1

[0095] Except for step 4, where the amount of sodium bromate is 1.9 eq and the amount of sodium dithionite is 1.58 eq, the procedure is carried out in the same manner as in Example 1.

[0096] After 18 hours of reaction, samples were taken for LCMS analysis, and the content of compound 5 in the system was 87.81%.

[0097] Example 4.2

[0098] Except for step 4, where the amount of sodium bromate is 2.2 eq and the amount of sodium dithionite is 1.83 eq, the procedure is carried out in the same manner as in Example 1.

[0099] After 18 hours of reaction, samples were taken for LCMS analysis, and the content of compound 5 in the system was 92.59%.

[0100] Example 4.3

[0101] Steps 1 to 3 are performed in the same manner as in Example 1.

[0102] In step 4, 10g of compound 4 was mixed with 10V acetic acid, 5% wet Pd / C was added, and the mixture was stirred at 50psi and 40-50℃. After the reaction was completed, the mixture was filtered, and the filter cake was washed with ethyl acetate. The filtrate was concentrated and dried to obtain the crude product. Ethyl acetate / water (6V / 12V) was added to the crude product, and sodium carbonate solid was added at 15-25℃ to adjust the pH to 5-6. The organic phase was separated, dried and concentrated at low temperature to obtain a colorless oil. The colorless oil was dissolved in 3V ethyl acetate, and 15V n-heptane was added dropwise at 0-10℃. After crystallization at low temperature for 1 hour, the mixture was filtered. The filter cake was crystallized once more using the ethyl acetate-n-heptane system and then filtered. The filter cake was dried to obtain 6.28g of compound 5 (net yield 92.35%).

[0103] Example 4.4

[0104] Except that the Pd / C catalyst used in step 4 was reused for the second time, the process was carried out in the same manner as in Example 4.3, yielding 5.6 g of compound 5 (net yield 82.35%).

[0105] Example 5

[0106] The reaction steps are similar to those in Example 1, except that the reaction scale is slightly different from that in Example 1.

[0107] Step 1: 252.6 kg of compound 1 was added, and after post-treatment, 348.8 kg of compound 2 was obtained (yield 90%).

[0108] Step 2: Add 260.0 kg of compound 2, and after post-treatment, obtain 181.2 kg of compound 3 (yield 84%).

[0109] Step 3: Add 155.0 kg of compound 3, and after post-treatment, obtain 195.3 kg of compound 4 (yield 95%).

[0110] Step 4: Add 193.3 kg of compound 4 of formula 4, and after post-treatment, obtain 85.9 kg of compound 5 of formula 5 (yield 65%).

[0111] Comparative Example 1

[0112] Except for the slight differences in the reaction conditions and parameters in step 1 compared to Example 1, the other steps were carried out in the same manner as in Example 1.

[0113] Comparative Example 1.1

[0114] Except that the benzyl reagent used in step 1 is benzyl chloride and the base is potassium tert-butoxide, the process is carried out in the same manner as in Example 1.

[0115] Samples were taken after 18 hours of reaction, and the HPLC content of compound 2 was 7.58%.

[0116] Comparative Example 1.2

[0117] Except that the base used in step 1 is potassium hydroxide and the reaction temperature is 15–25°C, the process is carried out in the same manner as in Example 1.

[0118] Samples were taken after 36 hours of reaction, and the HPLC content of compound 2 was 13.62%.

[0119] Comparative Example 2

[0120]

[0121] Step 1': 1.0 eq of compound 1, 2.5 eq of TBSCl, and 3.0 eq of imidazole were mixed in 3V DMF and reacted at 30℃~40℃. The reaction was monitored until compound 1 was ≤1%. After the reaction was completed, the temperature was controlled at 15℃~25℃, 9V of water was added and stirred, and then 2V of tert-butyl methyl ether was added to extract the product. The product was dried, concentrated to remove the organic phase, and then 9V of n-hexane and 1V of methyl tert-butyl ether were added. The mixture was heated at 70℃ for 2 hours and then recrystallized overnight at room temperature with stirring. After filtration and drying, compound 7 (yield 84%) was obtained.

[0122] Step 2': Dissolve 1.0 eq of compound 7 in 10 V of ethyl acetate, add 0.9 eq of sodium bromate aqueous solution (10 V) and 0.45 eq of sodium dithionite aqueous solution (5 V) to react. After the reaction is completed, the organic phase is separated and recrystallized with n-heptane and isopropanol to obtain compound 8 (yield 85%).

[0123] Step 3': Mix 1.0 eq of compound 8 and 1.0 eq of potassium carbonate in methanol and react. After the reaction is complete, purify the reaction solution using a silica gel column to obtain compound 9 (column yield 46.10%).

[0124] In the post-processing of step 3', a large amount of benzoic acid residue was present. Although it could be removed by silica gel column purification, the yield was too low (column yield: 46.10%).

[0125] Furthermore, the Formula 8 compound exhibits poor stability. After the crude Formula 8 compound obtained in step 2) was stored at 0–10°C for 5 days, TLC analysis showed a decrease in the content of Formula 8 compound, while NMR analysis revealed an increase in impurities in the sample.

[0126] Therefore, the reaction conditions of this invention are mild, the post-processing is simple, and the product yield and purity are high, thus enabling the production of the glucosamine derivative 2-N-4,6-di-O-tributyryl-D-glucosamine at a lower cost. All steps of this application can be scaled up to the kilogram scale for production, showing promise for industrial production.

[0127] Although the invention has been described in detail with reference to embodiments thereof, these embodiments are provided for illustration and not limitation. Other embodiments that can be obtained according to the principles of the invention fall within the scope defined by the claims of the invention.

[0128] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention.

Claims

1. A method for preparing 2-N-4,6-di-O-tributyryl-D-glucosamine, the method comprising: Step 1: In the presence of a base, react the compound of Formula 1 with benzyl bromide to obtain the compound of Formula 2, wherein the base is selected from one or more of sodium tert-amyl alcohol, potassium tert-butoxide, and sodium hydroxide. Step 2: In the presence of an acid, the compound of formula 2 undergoes a ring-opening reaction to obtain the compound of formula 3; Step 3: React the compound of formula 3 with an esterifying agent to obtain the compound of formula 4; as well as Step 4 involves subjecting the compound of formula 4 to a debenzylation reaction to obtain 2-N-4,6-di-O-tributyryl-D-glucosamine.

2. The method according to claim 1, wherein, The method further includes the following steps: Step A involves reacting the compound of formula 6 with benzaldehyde or benzaldehyde dimethyl acetal to obtain the compound of formula 1. The molar ratio of benzaldehyde or benzaldehyde dimethyl acetal to the compound of formula 6 is preferably 1.1:1 to 2:1, more preferably 1.4:1 to 1.7:

1.

3. The method according to claim 2, wherein, Step A is carried out in a solvent such as DMF at a reaction temperature of 40°C to 70°C in the presence of a catalyst, preferably p-toluenesulfonic acid.

4. The method according to any one of claims 1 to 3, wherein, Step 1 is carried out in a solvent at a reaction temperature of -15℃ to 25℃, preferably -5℃ to 5℃. Preferably, the solvent is selected from one or more of N,N-dimethylformamide (DMF), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), dichloromethane (DCM), and toluene, more preferably N,N-dimethylformamide and tetrahydrofuran, and even more preferably the volume ratio of N,N-dimethylformamide and tetrahydrofuran is 2:3 to 3:

2.

5. The method according to any one of claims 1 to 4, wherein, In step 1, the molar ratio of benzyl bromide to the compound of formula 1 is 3.0:1 to 2.0:1, preferably 2.5:1 to 2.1:1; and / or, The molar ratio of the base to the compound of formula 1 is 3.0:1 to 2.0:1, preferably 2.4:1 to 2.6:

1.

6. The method according to any one of claims 1 to 5, wherein, In step 2, the acid is hydrochloric acid, acetic acid, or sulfuric acid. Preferably, when the acid is hydrochloric acid or acetic acid, the volume ratio of the acid to water corresponding to the mass of the compound of formula 2 is 0.4:1 to 2.5:1, more preferably 1.7:1 to 2.5:1; when the acid is sulfuric acid, the volume ratio of the acid to water corresponding to the mass of the compound of formula 2 is 0.2:1 to 1.25:1, more preferably 0.8:1 to 1.25:

1.

7. The method according to any one of claims 1 to 6, wherein, Step 2 is carried out in a solvent selected from acetonitrile and / or water, preferably further comprising one or more of toluene, dichloromethane and n-heptane.

8. The method according to any one of claims 1 to 7, wherein, In step 3, the esterification agent is selected from butyric anhydride, butyryl chloride, or butyryl bromide, preferably butyric anhydride; wherein the molar ratio of the esterification agent to the compound of formula 3 is preferably 3.0:1 to 2.0:1, more preferably 2.5:1 to 2.1:1; And / or, step 3 is carried out in a solvent such as acetonitrile at a reaction temperature of 30°C to 40°C in the presence of a catalyst, such as pyridine and / or 4-dimethylaminopyridine (DMAP).

9. The method according to any one of claims 1 to 8, wherein, Step 4 is carried out by hydrogenation debenzylation, preferably by palladium-carbon hydrogenation in the presence of acid at a reaction temperature of 40°C to 50°C.

10. The method according to any one of claims 1 to 8, wherein, Step 4 is carried out by oxidative debenzylation. Preferably, step 4 is carried out by reacting sodium bromate and sodium dithionite at a reaction temperature of 20°C to 30°C. More preferably, the molar ratio of sodium bromate, sodium dithionite and compound of formula 4 is 1.7:1.3:1.0 to 3.0:2.5:1.0.

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