Preparation method of 7-demethylated amamicycline

Abstract

The invention belongs to the field of medicine synthesis, and particularly discloses a preparation method of 7-demethylated amazonicycline. The preparation method comprises the following steps: by taking 7-aminosancycline as an initial raw material, adding N-benzyl and N-methyl, then carrying out substitution reaction by using N-hydroxymethyl phthalimide, then removing phthaloyl by using methylamine, carrying out amination reduction reaction by using sodium borohydride and pivalaldehyde, and finally, carrying out hydrogenation by using pd / C to remove benzyl, thereby obtaining the 7-methyl oxalicycline. According to the route, the target product can be prepared with the total yield of 55%. According to the method, the impurity reference substance of the high-purity 7-methyl omalonin can be prepared, the accuracy of qualitative and quantitative analysis of the impurity is improved, the control on the impurity is enhanced, and the quality of an omalonin finished product is further improved.

Description

Technical Field

[0001] The present invention relates to omadacycline, in particular to 7-demethylomadacycline and a preparation method thereof, and belongs to the technical field of pharmaceutical chemistry. Background Art

[0002] Omadacycline was approved by the FDA in October 2018 for the treatment of acute bacterial skin and skin structure infections (ABSSSI) and community-acquired bacterial pneumonia (CABP) in adults. In January 2020, with the support of the "National 13th Five-Year Major New Drug Creation Project", Zai Lab was approved for marketing in China on December 16, 2021.

[0003] The mechanism of action of omadacycline is to specifically bind to the A site of the bacterial ribosome 30S subunit, inhibit the normal binding of aminoacyl-tRNA to this site, terminate the peptide chain extension, block protein synthesis and thus produce an antibacterial effect. The post-antibiotic effect (PAE) of omadacycline on Staphylococcus aureus, Streptococcus pneumoniae, Enterococcus, and Escherichia coli is better than linezolid and similar to tigecycline.

[0004] 7-Demethyl Omadacycline is a process impurity produced by removing a methyl group from the N, N-dimethyl group at the 7-position during the process of synthesizing Omadacycline. It is also produced by slow degradation during storage. 7-Demethyl Omadacycline remains in the final product of Omadacycline. When it reaches a certain limit, it produces certain toxic side effects, affecting the product quality of Omadacycline. Therefore, the original research has included 7-Demethyl Omadacycline (free state) in the quality standards of Omadacycline tosylate API (limit ≤0.3%) and Omadacycline tosylate preparation (limit ≤0.5%). The structural formula of the above 7-Demethyl Omadacycline is as follows: , 7-Demethylomacycline Molecular formula: C 28 H 38 N4O7 Molecular weight: 542.63.

[0005] Omadacycline is the latest generation of tetracycline antibiotics. The 7-demethylomadacycline impurity is limited in the quality standards of both raw materials and preparations. However, through domestic and foreign literature research, no preparation method of the impurity is disclosed. In addition, the residual amount of 7-demethylomadacycline impurity in the mother liquor is very small. It is very costly to enrich it by preparative chromatography to obtain a sufficient amount of reference substance. Therefore, a method for preparing high-purity 7-demethylomadacycline is provided to obtain an impurity reference substance for controlling the quality of omadacycline, which is of great significance to the research and control of the finished product quality of omadacycline. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing 7-demethylomadacycline, an impurity of omadacycline, so as to solve the problem that there is a lack of efficient method for preparing the above-mentioned impurity reference substance in the prior art.

[0007] The invention provides a method for preparing 7-demethylomadacycline.

[0008] In order to achieve the above object, the present invention adopts the following technical scheme: a method for preparing 7-demethylomadacycline, the synthetic route is as follows: .

[0009] The specific steps include: The reaction formula of step 1 is as follows: , 7-aminosancycline is used as a starting material and reacted with benzyl chloride to obtain compound 1, specifically, the starting material is dissolved in a solvent, a base and benzyl chloride are added, and the reaction is carried out at 25 to 35° C. After the reaction is completed, the mixture is concentrated under reduced pressure, water and dichloromethane are added to separate the layers, and a dichloromethane layer is obtained. After drying, the dichloromethane layer is subjected to decompression and rotary drying to obtain compound 1; In the process of preparing compound 1, the molar ratio of 7-aminosancycline to benzyl chloride used is 1:0.9 to 1.3, preferably (1:0.9 to 1.0); Using solvent 1 is selected from one or a mixture of methanol, ethanol, THF, and dioxane; The base used is selected from one of triethylamine, diisopropylethylamine, DBU (1,8-diazacyclo[5,4,0]undecene-7), and diisopropylamine, or a mixture of several of them.

[0010] The reaction formula of step 2 is as follows: , The compound 1 obtained in step 1 is dissolved in a solvent, and reacted with iodomethane under the action of a base at 0-5°C. After the reaction is completed, the compound 1 is added into water and stirred. After stirring, the mixture is filtered and dried to obtain the compound 2. In the process of preparing compound 2, solvent 2 is selected from one or a mixture of dichloromethane, chloroform, tetrahydrofuran, and acetonitrile; The base used is selected from triethylamine, diisopropylethylamine, DBU (1,8-diazacyclo[5,4,0]undecene-7), diisopropylamine or a mixture of the two or more.

[0011] The reaction formula of step 3 is as follows: , Dissolve the compound 2 obtained in step 2 and N-hydroxymethylphthalimide in a solvent, react at 20-30° C., add water and stir after the reaction, filter and dry to obtain compound 3; In the process of preparing compound 3, solvent 3 is selected from one or a mixture of trifluoroacetic acid, trifluoromethanesulfonic acid, acetic acid, and methanesulfonic acid; In the process of preparing compound 3, the molar ratio of compound 2 to N-hydroxymethylphthalimide is 1:2.0-3.0, preferably (1:2.5-3.0).

[0012] The reaction formula of step 4 is as follows: , The compound 3 obtained in step 3 is dissolved in a solvent, and a 30% methylamine methanol solution is added at 20-30° C. After the reaction is completed, the mixture is filtered, and the filtrate is added to methyl tert-butyl ether and stirred. After stirring, the mixture is filtered and dried to obtain compound 4; In the process of preparing compound 4, solvent 4 is selected from one or a mixture of methanol, ethanol, acetonitrile and tetrahydrofuran; In the process of preparing compound 4, the molar ratio of compound 3 to 30% methylamine methanol solution is 1:5.0-10.0, preferably (1:5.0-8.0).

[0013] The reaction formula of step 5 is as follows: , The compound 4 obtained in step 4 is dissolved in a solvent, and sodium borohydride, triethylamine and p-valeraldehyde are added to react at 20-30° C. After the reaction is completed, water is added, and the mixture is extracted with dichloromethane, dried, filtered, and the filtrate is concentrated under reduced pressure to obtain a concentrated solution, and methyl tert-butyl ether is added to stir, and after stirring, filtered, and dried to obtain compound 5; In the process of preparing compound 5, solvent 5 is selected from one or a mixture of methanol, ethanol, acetonitrile and tetrahydrofuran; In the process of preparing compound 5, the molar ratio of compound 4 to pivalaldehyde is 1:1.2 to 2.0, preferably (1:1.2 to 1.8); In the process of preparing compound 5, the molar ratio of compound 4 to sodium borohydride is 1:1.1-2.0, preferably (1:1.1-1.6).

[0014] The reaction formula of step 6 is as follows: , The compound 5 obtained in step 5 is dissolved in a solvent, and Pd / C and triethylamine are added at 10-30° C., and hydrogen is introduced to react. After the reaction is completed, the reaction is filtered, and the filtrate is added with water, extracted with dichloromethane, dried, filtered, and the filtrate is concentrated under reduced pressure to obtain a concentrated solution, and n-heptane is added to stir, and after stirring, filtered, and dried to obtain the target compound 7-methylomacycline; In the process of preparing the compound 7-methylomadacycline, the solvent 6 is selected from one or a mixture of methanol, ethanol, acetonitrile and tetrahydrofuran; In the process of preparing the compound 7-methylomadacycline, the temperature of the reaction liquid is controlled at 10-30°C, preferably at 20-30°C.

[0015] The present invention provides a method for preparing 7-methylomadacycline, which mainly has the following beneficial effects:

[0016] 1. The present invention uses 7-aminosancycline as a starting material, undergoes N-benzyl, N-methyl, N-hydroxymethylphthalimide substitution, removes phthalyl from methylamine, undergoes amination reduction reaction with sodium borohydride and pivalaldehyde, and then removes the benzyl group with pd / C hydrogenation to obtain 7-methylomadacycline. This route can prepare the target product with a yield of 55%.

[0017] 2. The present invention can prepare a high-purity impurity reference substance of 7-methylomadacycline, improve the accuracy of qualitative and quantitative analysis of the impurity, help strengthen the control of the impurity, and further improve the quality of the finished product of omadacycline.

[0018] 3. The present invention prepares 7-methylomadacycline through directional synthesis, thereby solving the shortcomings of the impurity reference substance, such as difficulty in enrichment, low purity, and low yield. DETAILED DESCRIPTION

[0019] In order to further understand the present invention, the preparation method of 7-methyl omadacycline provided by the present invention is described in detail below in conjunction with the examples. It should be understood that these examples are only for further illustrating the features of the present invention in detail, and are not intended to limit the scope of the present invention or the scope of the claims of the present invention. Example 1

[0020] Preparation of compound 1 (7-benzylaminosancycline) Dissolve 100 g (0.232 mol) of 7-aminosancycline in 400 ml of methanol, add 30 ml of triethylamine, stir and dissolve, slowly add 29.3 g (0.232 mol) of benzyl chloride, react at 25-35 ° C for 3 h, and after the reaction is completed, evaporate the solvent under reduced pressure, add 400 ml of dichloromethane and 200 ml of water to the residue, extract and separate, and obtain a dichloromethane layer, dry it with 20 g of anhydrous sodium sulfate, filter, and evaporate to dryness under reduced pressure at 37 ° C to obtain 111 g of solid compound 1, with a yield of 92%. m / z [M+H] + :520.20.

[0021] Preparation of Compound 2 (7-(N-methyl-N-benzyl)-sancycline) 100g (0.192mol) of compound 1 was dissolved in 500ml of chloroform, and 25ml of diisopropylethylamine was added. The reaction solution was cooled to 0-5°C, and 27.2g (0.192mol) of iodomethane was slowly added at this temperature. After the addition, the reaction was continued at 0-5°C for 3h. After the reaction was completed, 200ml of water was added, and the organic layer was obtained. It was dried with 20g of anhydrous sodium sulfate, filtered, and the solvent was evaporated under reduced pressure at 37°C to obtain 93g of solid, with a yield of 91%. m / z [M+H] + :534.21.

[0022] 3) Preparation of compound 3 90g (0.169mol) of compound 2 was dissolved in 270ml of trifluoromethanesulfonic acid, and stirred to dissolve at 20-30°C. At this temperature, 74.8g (0.422mol) of N-hydroxymethylphthalimide was slowly added, and the reaction was continued at 20-30°C for 8h. After the reaction was completed, ice water was slowly added, and the solid was precipitated by stirring. The solid was filtered, washed with water, and dried at 38°C to obtain 130g of solid with a yield of 90.2%. m / z [M+H] + :852.28.

[0023] 4) Preparation of compound 4 100g (0.117mol) of compound 3 was dissolved in 500ml of methanol, stirred and dissolved at 20-30°C, 60.5g of 30% methylamine methanol solution was added, and the reaction was continued at 20-30°C for 3h. After the reaction was completed, the mixture was filtered, 500ml of methyl tert-butyl ether was added to the filtrate, and the solid was precipitated by stirring, filtered, and dried at 38°C to obtain 59g of compound 5 with a yield of 90%. m / z [M+H]+ :563.24.

[0024] 5) Preparation of compound 5 50g (0.0893mol) of compound 4 was dissolved in 500ml of methanol, and 15ml of triethylamine, 9.22g (0.107mol) of p-valeraldehyde and 3.7g (0.0982mol) of sodium borohydride were added. The mixture was stirred at 20-30℃ for 3h. After the reaction was completed, 100ml of water was slowly added, and 500ml of dichloromethane was added. The dichloromethane layer was separated and dried with 20g of anhydrous sodium sulfate, filtered and evaporated to dryness under reduced pressure at 37℃ to obtain 50g of compound 5 with a yield of 90%. m / z [M+H] + :633.32.

[0025] 6) Preparation of 7-demethylomacycline 50g (0.0794mol) of compound 5 was dissolved in 300ml of methanol, and 5g of Pa / C (10%) was added for hydrogenation reaction. The hydrogen pressure was 0.2Mpa, and the reaction was carried out at a temperature of 20-30°C for 5h. After the reaction was completed, it was filtered, and the filtrate was added into water. 400ml of dichloromethane was added for extraction. The dichloromethane layer was separated by stratification, 20g of anhydrous sodium sulfate was added for drying, the mixture was filtered, and the mixture was evaporated to dryness under reduced pressure to obtain a residue. 200ml of n-heptane was added for pulping, the residue was filtered, and the residue was dried at 38°C to obtain 38.8g of 7-demethylomacycline with a yield of 90.5%. m / z [M+H] + :543.27. Example 2

[0026] 1) Preparation of compound 1 (7-benzylaminosancycline) Dissolve 100 g (0.232 mol) of 7-aminosancycline in 500 ml of tetrahydrofuran, add 40 ml of diisopropylethylamine, stir and dissolve, slowly add 32.2 g (0.255 mol) of benzyl chloride, react at 25-35 ° C for 3 h, and after the reaction is completed, evaporate the solvent under reduced pressure, add 500 ml of dichloromethane and 300 ml of water to the residue, extract and separate, and obtain a dichloromethane layer, dry it with 20 g of anhydrous sodium sulfate, filter, and evaporate to dryness under reduced pressure at 37 ° C to obtain 109 g of solid compound 1, with a yield of 90%.

[0027] 2) Preparation of compound 2 (7-(N-methyl-N-benzyl)-sancycline) 100g (0.192mol) of compound 1 was dissolved in 500ml of tetrahydrofuran, and 30ml of triethylamine was added. The reaction solution was cooled to 0-5°C, and 27.2g (0.192mol) of iodomethane was slowly added at this temperature. After the addition, the reaction was continued at 0-5°C for 3h. After the reaction was completed, 300ml of water was added, and the layers were separated to obtain an organic layer. The layer was dried with 20g of anhydrous sodium sulfate, filtered, and the solvent was evaporated under reduced pressure at 37°C to obtain 95g of solid with a yield of 93%.

[0028] 3) Preparation of compound 3 Dissolve 90g (0.169mol) of compound 2 in 300ml of trifluoroacetic acid, stir and dissolve at 20-30°C, slowly add 89.7g (0.506mol) of N-hydroxymethylphthalimide at this temperature, and continue to react at 20-30°C for 8h. After the reaction is completed, slowly add ice water, stir to precipitate solid, filter, wash with water, and dry at 38°C to obtain 132.5g of solid with a yield of 92%.

[0029] 4) Preparation of compound 4 100 g (0.117 mol) of compound 3 was dissolved in 500 ml of acetonitrile, stirred and dissolved at 20-30°C, 71 g of 30% methylamine methanol solution was added, and the reaction was continued at 20-30°C for 3 h. After the reaction was completed, the reaction was filtered, 400 ml of methyl tert-butyl ether was added to the filtrate, and the solid was precipitated by stirring, filtered, and dried at 38°C to obtain 58.3 g of compound 5 with a yield of 89%.

[0030] 5) Preparation of compound 5 50 g (0.0893 mol) of compound 4 was dissolved in 500 ml of methanol, and 15 ml of triethylamine, 13.8 g (0.160 mol) of p-valeraldehyde and 5.38 g (0.142 mol) of sodium borohydride were added. The mixture was stirred at 20-30 °C for 3 h. After the reaction was completed, 150 ml of water was slowly added, and 500 ml of dichloromethane was added. The dichloromethane layer was separated and dried over 20 g of anhydrous sodium sulfate, filtered and evaporated under reduced pressure at 37 °C to obtain 50.3 g of compound 5 with a yield of 90.5%.

[0031] 6) Preparation of 7-demethylomacycline 50 g (0.0794 mol) of compound 5 was dissolved in 400 ml of methanol, and 6 g of Pa / C (10%) was added for hydrogenation reaction. The hydrogen pressure was 0.2 MPa and the reaction was carried out at a temperature of 20-30°C for 5 h. After the reaction was completed, the filtrate was filtered and added into water. 500 ml of dichloromethane was added for extraction. The dichloromethane layer was separated by layers and 20 g of anhydrous sodium sulfate was added for drying. The layer was filtered and evaporated to dryness under reduced pressure to obtain a residue. 200 ml of n-heptane was added for pulping. The residue was filtered and dried at 38°C to obtain 39.4 g of 7-demethylomacycline with a yield of 92%.

Claims

1. A method for preparing 7-demethylomadacycline, comprising the following steps: 。 2. The preparation method according to claim 1, wherein the reaction formula of step 1 is as follows: ， 7-aminosancycline is used as a starting material and reacted with benzyl chloride to obtain compound 1, specifically, the starting material is dissolved in a solvent, a base and benzyl chloride are added, and the reaction is carried out at 25 to 35° C. After the reaction is completed, the mixture is concentrated under reduced pressure, water and dichloromethane are added to separate the layers, and a dichloromethane layer is obtained. After drying, the dichloromethane layer is subjected to decompression and rotary drying to obtain compound 1; in, The molar ratio of 7-aminosancycline to benzyl chloride used in step 1 is 1:0.9-1.0; Wherein, the solvent 1 used in step 1 is selected from one or a mixture of methanol, ethanol, THF, and dioxane; Wherein, the base used in step 2 is selected from one or a mixture of triethylamine, diisopropylethylamine, DBU (1,8-diazacyclo[5,4,0]undecene-7), and diisopropylamine.

3. The preparation method according to claim 1, wherein the reaction formula of step 2 is as follows: ， The compound 1 obtained in step 1 is dissolved in a solvent, and reacted with iodomethane under the action of a base at 0-5°C. After the reaction is completed, the mixture is added into water and stirred. After stirring, the mixture is filtered and dried at 38°C to obtain a compound 2. in, The solvent 2 used in step 2 is selected from one or a mixture of dichloromethane, chloroform, tetrahydrofuran, and acetonitrile; Wherein, the base used in step 2 is selected from triethylamine, diisopropylethylamine, DBU (1,8-diazacyclo[5,4,0]undecene-7), diisopropylamine or a mixture of the above.

4. The preparation method according to claim 1, wherein the reaction formula of step 3 is as follows: ， Dissolve the compound 2 obtained in step 2 and N-hydroxymethylphthalimide in a solvent, react at 20-30° C., add water and stir after the reaction, filter and dry to obtain compound 3; in, The solvent 3 used in step 3 is selected from one or a mixture of trifluoroacetic acid, trifluoromethanesulfonic acid, acetic acid, and methanesulfonic acid; Wherein, the molar ratio of compound 2 used in step 3 to N-hydroxymethylphthalimide is 1:2.5-3.

0.

5. The preparation method according to claim 1, wherein the reaction formula of step 4 is as follows: ， The compound 3 obtained in step 3 was dissolved in a solvent, and a 30% methylamine methanol solution was added at 20-30°C. After the reaction was completed, the reaction was filtered, and the filtrate was added to methyl tert-butyl ether and stirred. After stirring, the filtrate was filtered and dried at 38°C to obtain compound 4; in, The solvent 4 used in step 4 is selected from one or a mixture of methanol, ethanol, acetonitrile and tetrahydrofuran; Wherein, the molar ratio of compound 3 used in step 4 to 30% methylamine methanol solution is 1:5.0-8.

0.

6. The preparation method according to claim 1, wherein the reaction formula of step 5 is as follows: ， The compound 4 obtained in step 4 is dissolved in a solvent, and sodium borohydride, triethylamine and p-valeraldehyde are added to react at 20-30° C. After the reaction is completed, water is added, and the mixture is extracted with dichloromethane, dried, filtered, and the filtrate is concentrated under reduced pressure to obtain a concentrated solution, and methyl tert-butyl ether is added to stir, and after stirring, filtered, and dried to obtain compound 5; in, The solvent 5 used in step 5 is selected from one or a mixture of methanol, ethanol, acetonitrile and tetrahydrofuran; Wherein, the molar ratio of compound 4 used in step 5 to pivalaldehyde is 1:1.2-1.

8.

7. The preparation method according to claim 1, wherein the reaction formula of step 6 is as follows: ， The compound 5 obtained in step 5 is dissolved in a solvent, and Pd / C and triethylamine are added at 10-30° C., and hydrogen is introduced to react. After the reaction is completed, the reaction is filtered, and the filtrate is added with water, extracted with dichloromethane, dried, filtered, and the filtrate is concentrated under reduced pressure to obtain a concentrated solution, and n-heptane is added to stir, and after stirring, filtered, and dried to obtain the target compound 7-methylomacycline; in, The solvent 6 used in step 6 is selected from one or a mixture of methanol, ethanol, acetonitrile and tetrahydrofuran; Wherein, the reaction temperature in step 6 is controlled at 20-30°C.

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