Process for the preparation of 7-demethyloxytetracycline

Abstract

The application belongs to the field of medicine synthesis, and particularly discloses a preparation method of 7-demethylomaline. The application takes 7-aminoomaricin as a starting material, carries out N-benzyl and N-methyl, then carries out substitution reaction by using N-hydroxymethyl phthalimide, carries out amine reduction reaction by using sodium borohydride and tert-pentanol, and finally carries out benzyl removal by using pd / C hydrogenation to obtain 7-methylomaline. The route can prepare the target product with a total yield of 55%. The application can prepare the impurity control of 7-methylomaline with high purity, improve the accuracy of qualitative and quantitative analysis of the impurity, is conducive to strengthening the control of the impurity, and further improves the quality of omaline finished products.

Description

TECHNICAL FIELD

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

[0002] Omadacycline was approved by 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, it was supported by the National Major New Drug Creation Program of the 13th Five-Year Plan. On December 16, 2021, Rely Pharmaceuticals Co., Ltd. was approved for listing in China.

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

[0004] 7-demethylomadacycline is a process impurity produced by removing one methyl group from the N,N-dimethyl group at position 7 in the synthesis process of omadacycline. It is also slowly degraded during storage. 7-demethylomadacycline remains in the final product of omadacycline. When it reaches a certain limit, it produces certain toxic side effects and affects the product quality of omadacycline. Therefore, the original research has set the 7-demethylomadacycline (free state) into the quality standards of omadacycline tosylate raw material (limit ≤0.3%) and omadacycline tosylate preparation (limit ≤0.5%). The structure of the above 7-demethylomadacycline is as follows:

[0005] ,

[0006] 7-demethylomadacycline

[0007] Molecular formula: C 28 H 38 N4O7

[0008] Molecular weight: 542.63.

[0009] Omalidomycin is the latest generation of tetracycline antibiotics, the raw material and preparation quality standards are limited to 7-demethylation of omalidomycin impurities, but through the literature research at home and abroad, the preparation method of the impurity is not disclosed, in addition, the residual amount of 7-demethylation of omalidomycin impurities in the mother liquor is very small, and the cost of obtaining sufficient amount of reference substance by preparative chromatography is very high, therefore, a method for preparing high-purity 7-demethylation of omalidomycin is provided to obtain impurity reference substance for the quality control of omalidomycin, which has important significance for the quality research and control of omalidomycin. SUMMARY

[0010] The purpose of the present application is to provide a preparation method of 7-demethylation of omalidomycin, an impurity of omalidomycin, to solve the problem of lack of efficient preparation method of the above-mentioned impurity reference substance in the prior art.

[0011] The present application provides a preparation method of 7-demethylation of omalidomycin.

[0012] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: a preparation method of 7-demethylation of omalidomycin, the synthetic route is as follows:

[0013] .

[0014] Specifically comprising the following steps:

[0015] Step 1 reaction formula is as follows:

[0016] ,

[0017] 7-amino tetracycline is used as starting material, and compound 1 is obtained by reaction with benzyl chloride, specifically, the starting material is dissolved in a solvent, a base and benzyl chloride are added, and the reaction is carried out at 25-35℃, after the reaction is completed, vacuum concentration is carried out, water and dichloromethane are added for layer separation, dichloromethane layer is obtained, after drying, vacuum rotary evaporation is carried out to obtain compound 1;

[0018] In the preparation of compound 1, the molar ratio of 7-amino tetracycline to benzyl chloride used is 1:0.9-1.3, preferably (1:0.9-1.0);

[0019] The solvent 1 is selected from one or several mixtures of methanol, ethanol, THF, dioxane;

[0020] The base used is selected from one or several mixtures of triethylamine, diisopropyl ethylamine, DBU (1,8-diazabicyclo[5,4,0]undec-7), diisopropylamine.

[0021] Step 2 reaction formula is as follows:

[0022] ,

[0023] 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, water is added and stirred. After stirring, filtration is performed, and drying is performed to obtain compound 2.

[0024] In the preparation of compound 2, the solvent 2 is selected from one or more of dichloromethane, chloroform, tetrahydrofuran, acetonitrile.

[0025] The base used is selected from one or more of triethylamine, diisopropylethylamine, DBU (1,8-diazabicyclo[5,4,0]undec-7-ene), diisopropylamine.

[0026] The reaction formula of step 3 is as follows:

[0027] ,

[0028] Compound 2 obtained in step 2 is dissolved in a solvent, and reacted with N-hydroxymethyl phthalimide at 20-30°C. After the reaction is completed, water is added and stirred. After stirring, filtration is performed, and drying is performed to obtain compound 3.

[0029] In the preparation of compound 3, the solvent 3 is selected from one or more of trifluoroacetic acid, triflic acid, acetic acid, methanesulfonic acid.

[0030] In the preparation of compound 3, the molar ratio of compound 2 to N-hydroxymethyl phthalimide is 1:2.0-3.0, preferably (1:2.5-3.0).

[0031] The reaction formula of step 4 is as follows:

[0032] ,

[0033] Compound 3 obtained in step 3 is dissolved in a solvent, and 30% methylamine methanol solution is added at 20-30°C. After the reaction is completed, filtration is performed, and the filtrate is stirred in methyl tert-butyl ether. After stirring, filtration is performed, and drying is performed to obtain compound 4.

[0034] In the preparation of compound 4, the solvent 4 is selected from one or more of methanol, ethanol, acetonitrile, tetrahydrofuran.

[0035] In the preparation of 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).

[0036] The reaction formula of step 5 is as follows:

[0037] ,

[0038] The compound 4 obtained in step 4 is dissolved in a solvent, sodium borohydride, triethylamine and tert-pivalaldehyde are added at 20-30°C, after the reaction is completed, water is added, extracted with dichloromethane, dried, filtered, the filtrate is concentrated under reduced pressure to obtain a concentrated solution, methyl tert-butyl ether is added and stirred, after stirring, filtered and dried to obtain compound 5;

[0039] In the preparation of compound 5, the solvent 5 is selected from one or more of methanol, ethanol, acetonitrile and tetrahydrofuran;

[0040] In the preparation of compound 5, the molar ratio of compound 4 to tert-pivalaldehyde is 1:1.2-2.0, preferably (1:1.2-1.8);

[0041] In the preparation of compound 5, the molar ratio of compound 4 to sodium borohydride is 1:1.1-2.0, preferably (1:1.1-1.6).

[0042] The reaction formula of step 6 is as follows:

[0043] ,

[0044] The compound 5 obtained in step 5 is dissolved in a solvent, pd / C and triethylamine are added at 10-30°C, and hydrogen is introduced for reaction, after the reaction is completed, filtered, the filtrate is added with water, extracted with dichloromethane, dried, filtered, the filtrate is concentrated under reduced pressure to obtain a concentrated solution, n-heptane is added and stirred, after stirring, filtered and dried to obtain the target compound 7-methyl omadacycline;

[0045] In the preparation of compound 7-methyl omadacycline, the solvent 6 is selected from one or more of methanol, ethanol, acetonitrile and tetrahydrofuran;

[0046] In the preparation of compound 7-methyl omadacycline, the reaction liquid temperature is controlled at 10-30°C, preferably the reaction liquid temperature is controlled at 20-30°C.

[0047] The present application provides a preparation method of 7-methyl omadacycline, which has the following beneficial effects:

[0048] 1. The present application uses 7-amino omadacycline as a starting material, which is subjected to N-benzyl, N-methyl, N-hydroxymethyl phthalimide substitution, methylamine removal of phthaloyl, amine reduction reaction with sodium borohydride and tert-pivalaldehyde, and then benzyl is removed by pd / C hydrogenation to obtain 7-methyl omadacycline. The route can prepare the target product with a yield of 55%.

[0049] 2. The present application can prepare the impurity reference substance of 7-methyl omadacycline with high purity, improve the accuracy of qualitative and quantitative analysis of the impurity, and is beneficial to strengthen the control of the impurity, and further improve the finished product quality of omadacycline.

[0050] 3. The present application solves the problems of difficulty in enriching the impurity reference substance, low purity and low yield of 7-methyl omadacycline by directed synthesis. DETAILED DESCRIPTION

[0051] In order to further understand the present application, the preparation method of 7-methyl omadacycline provided by the present application is described in detail below in combination with examples. It should be understood that these examples are only for further detailed description of the features of the present application, and are not a limitation on the scope of the present application or the scope of claims of the present application. Example 1

[0052] Preparation of compound 1 (7-benzylamine tetracycline)

[0053] 100 g (0.232 mol) of 7-amino tetracycline was dissolved in 400 ml of methanol, 30 ml of triethylamine was added, and the solution was stirred and dissolved. 29.3 g (0.232 mol) of benzyl chloride was slowly added, and after the addition was completed, the reaction was carried out at 25-35°C for 3 h. After the reaction was completed, the solvent was evaporated under reduced pressure, and the residue was added to 400 ml of dichloromethane and 200 ml of water to perform extraction and separation. The dichloromethane layer was dried with 20 g of anhydrous sodium sulfate, filtered, and evaporated 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.

[0054] Preparation of compound 2 (7-(N-methyl-N-benzyl)-tetracycline)

[0055] 100 g (0.192 mol) of compound 1 was dissolved in 500 ml of chloroform, 25 ml of diisopropyl ethylamine was added, and the reaction solution was cooled to 0-5°C. 27.2 g (0.192 mol) of iodomethane was slowly added at this temperature, and after the addition was completed, the reaction was continued at 0-5°C for 3 h. After the reaction was completed, 200 ml of water was added, and the organic layer was separated. The organic layer was dried with 20 g of anhydrous sodium sulfate, filtered, and the solvent was evaporated under reduced pressure at 37°C to obtain 93 g of solid with a yield of 91%, m z [M+H] + : 534.21.

[0056] 3) Preparation of compound 3

[0057] ​​90 g (0.169 mol) of compound 2 was dissolved in 270 mL of trifluoromethanesulfonic acid and stirred at 20–30 °C. At this temperature, 74.8 g (0.422 mol) of N-hydroxymethyl phthalimide was slowly added, and the reaction was continued at 20–30 °C for 8 h. After the reaction was complete, ice water was slowly added, and the mixture was stirred to precipitate a solid. The solid was filtered, washed with water, and dried at 38 °C to obtain 130 g of solid, with a yield of 90.2%. m / z [M+H] + : 852.28.

[0058] 4) Preparation of compound 4

[0059] 100 g (0.117 mol) of compound 3 was dissolved in 500 ml of methanol and stirred at 20–30 °C. Then, 60.5 g of a 30% methylamine methanol solution was added, and the reaction was continued at 20–30 °C for 3 h. After the reaction was complete, the mixture was filtered, and 500 ml of methyl tert-butyl ether was added to the filtrate. The mixture was stirred to precipitate a solid, which was then filtered and dried at 38 °C to give 59 g of compound 5, with a yield of 90%. m / z [M+H] + : 563.24.

[0060] 5) Preparation of compound 5

[0061] 50 g (0.0893 mol) of compound 4 was dissolved in 500 mL of methanol, followed by the addition of 15 mL of triethylamine, 9.22 g (0.107 mol) of pivalal, and 3.7 g (0.0982 mol) of sodium borohydride. The mixture was stirred at 20–30 °C for 3 h. After the reaction was complete, 100 mL of water was slowly added, followed by 500 mL of dichloromethane. The mixture was allowed to separate into two layers, which were dried over 20 g of anhydrous sodium sulfate, filtered, and evaporated to dryness under reduced pressure at 37 °C to obtain 50 g of compound 5, with a yield of 90%. m / z [M+H] + : 633.32.

[0062] 6) Preparation of 7-Demethylomacycline

[0063] The 50 g (0.0794 mol) compound 5 was dissolved in 300 ml of methanol, 5 g of Pa / C (10%) was added, and hydrogenation was performed at a hydrogen pressure of 0.2 MPa at a temperature of 20-30 °C for 5 h. After the reaction was completed, the reaction solution was filtered, water was added to the filtrate, and extraction was performed using 400 ml of dichloromethane. The dichloromethane layer was separated, dried using 20 g of anhydrous sodium sulfate, filtered, and evaporated under reduced pressure to obtain a residue. The residue was slurried using 200 ml of n-heptane, filtered, and dried at 38 °C to obtain 7-demethyloma ring 38.8 g at a yield of 90.5%. m z [M+H] + : 543.27. Example 2

[0064] 1) Preparation of compound 1 (7-benzylamino-omaricin)

[0065] The 7-amino-omaricin 100 g (0.232 mol) was dissolved in 500 ml of tetrahydrofuran, 40 ml of diisopropyl ethyl amine was added, and the solution was stirred and dissolved. Then, 32.2 g (0.255 mol) of benzyl chloride was slowly added, and the reaction was performed at a temperature of 25-35 °C for 3 h. After the reaction was completed, the solvent was evaporated under reduced pressure, and the residue was extracted with 500 ml of dichloromethane and 300 ml of water to obtain a dichloromethane layer. The dichloromethane layer was dried using 20 g of anhydrous sodium sulfate, filtered, and evaporated under reduced pressure at 37 °C to obtain 109 g of a solid compound 1 at a yield of 90%.

[0066] 2) Preparation of compound 2 (7-(N-methyl-N-benzyl)-omaricin)

[0067] The 100 g (0.192 mol) compound 1 was dissolved in 500 ml of tetrahydrofuran, 30 ml of triethylamine was added, and the reaction solution was cooled to 0-5 °C. Then, 27.2 g (0.192 mol) of iodomethane was slowly added at a temperature of 0-5 °C, and the reaction was performed at a temperature of 0-5 °C for 3 h. After the reaction was completed, 300 ml of water was added, and the organic layer was separated. The organic layer was dried using 20 g of anhydrous sodium sulfate, filtered, and evaporated under reduced pressure at 37 °C to obtain 95 g of a solid at a yield of 93%.

[0068] 3) Preparation of compound 3

[0069] The 90 g (0.169 mol) compound 2 was dissolved in 300 ml of trifluoroacetic acid, and the solution was stirred and dissolved at a temperature of 20-30 °C. Then, 89.7 g (0.506 mol) of N-hydroxymethyl phthalimide was slowly added at a temperature of 20-30 °C, and the reaction was performed at a temperature of 20-30 °C for 8 h. After the reaction was completed, the reaction solution was slowly added to ice water, and a solid was precipitated by stirring. The solid was filtered, washed with water, and dried at 38 °C to obtain 132.5 g of a solid at a yield of 92%. ​

[0070] 4) Preparation of compound 4

[0071] Dissolve 100 g (0.117 mol) of compound 3 in 500 ml of acetonitrile, stir the solution at a temperature of 20-30 °C, add 71 g of 30% methylamine methanol solution, continue to react at 20-30 °C for 3 h, after the reaction is completed, filter, add 400 ml of methyl tert-butyl ether to the filtrate, stir to precipitate the solid, filter, and dry at 38 °C to obtain 58.3 g of compound 5 with a yield of 89%.

[0072] 5) Preparation of compound 5

[0073] Dissolve 50 g (0.0893 mol) of compound 4 in 500 ml of methanol, add 15 ml of triethylamine, add 13.8 g (0.160 mol) of tert-pivaldehyde, add 5.38 g (0.142 mol) of sodium borohydride, stir at 20-30 °C for 3 h, after the reaction is completed, slowly add 150 ml of water, add 500 ml of dichloromethane, separate the dichloromethane layer, dry with 20 g of anhydrous sodium sulfate, filter, and evaporate to dryness at 37 °C under reduced pressure to obtain 50.3 g of compound 5 with a yield of 90.5%.

[0074] 6) Preparation of 7-demethylomaline

[0075] Dissolve 50 g (0.0794 mol) of compound 5 in 400 ml of methanol, add 6 g of Pa / C (10%), perform hydrogenation reaction, hydrogen pressure is 0.2 Mpa, react at a temperature of 20-30 °C for 5 h, after the reaction is completed, filter, add water to the filtrate, extract with 500 ml of dichloromethane, separate the dichloromethane layer, dry with 20 g of anhydrous sodium sulfate, filter, evaporate to dryness under reduced pressure, obtain a residue, add 200 ml of n-heptane to perform slurry, filter, and dry at 38 °C to obtain 7-demethylomaline 39.4 g with a yield of 92%.

Claims

1. A method for preparing 7-demethylomacycline, comprising the following steps: 。 2. The preparation method according to claim 1, wherein the reaction formula in step 1 is as follows: ， Using 7-aminoxacycline as the starting material, compound 1 was obtained by reacting it with benzyl chloride. Specifically, the starting material was dissolved in solvent 1, alkali and benzyl chloride were added, and the reaction was carried out at 25-35°C. After the reaction was completed, the mixture was concentrated under reduced pressure, and water and dichloromethane were added to separate the layers to obtain a dichloromethane layer. After drying, the mixture was evaporated under reduced pressure to obtain compound 1. in, The molar ratio of 7-aminoxacycline to benzyl chloride used in step 1 is 1:0.9 to 1.0; In step 1, solvent 1 is selected from one or a mixture of methanol, ethanol, THF, and dioxane; The base used in step 1 is selected from one or a mixture of several of the following: 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 in step 2 is as follows: ， Compound 1 obtained in step 1 was dissolved in solvent 2 and reacted with iodomethane under the action of alkali at 0-5℃. After the reaction was completed, water was added and stirred. After stirring, the mixture was filtered and dried at 38℃ to obtain compound 2. in, The solvent 2 used in step 2 is selected from one or a mixture of several of dichloromethane, trichloromethane, tetrahydrofuran, and acetonitrile; The base used in step 2 is selected from one or a mixture of several of the following: triethylamine, diisopropylethylamine, DBU (1,8-diazacyclo[5,4,0]undecene-7), and diisopropylamine.

4. The preparation method according to claim 1, wherein the reaction formula in step 3 is as follows: ， Compound 2 obtained in step 2 was dissolved in solvent 3 with N-hydroxymethyl phthalimide and reacted at 20-30°C. After the reaction was completed, water was added and stirred. After stirring, the mixture was filtered and dried 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; In step 3, the molar ratio of compound 2 to N-hydroxymethyl phthalimide is 1:2.5 to 3.

0.

5. The preparation method according to claim 1, wherein the reaction formula in step 4 is as follows: ， Compound 3 obtained in step 3 was dissolved in solvent 4, and 30% methylamine methanol solution was added at 20-30°C. After the reaction was completed, the mixture was filtered, and the filtrate was added to methyl tert-butyl ether and stirred. After stirring, the mixture 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; In step 4, the molar ratio of compound 3 to 30% methylamine methanol solution is 1:5.0 to 8.

0.

6. The preparation method according to claim 1, wherein the reaction formula in step 5 is as follows: ， Compound 4 obtained in step 4 was dissolved in solvent 5. Sodium borohydride, triethylamine, and tert-pentanal were added at 20-30°C to react. After the reaction was completed, water was added, and the mixture was extracted with dichloromethane, dried, filtered, and the filtrate was concentrated under reduced pressure to obtain a concentrated solution. Methyl tert-butyl ether was added and stirred. After stirring, the mixture was 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; In step 5, the molar ratio of compound 4 to pivalaldehyde is 1:1.2 to 1.

8.

7. The preparation method according to claim 1, wherein the reaction formula in step 6 is as follows: ， Compound 5 obtained in step 5 was dissolved in solvent 6. Pd / C and triethylamine were added at 10–30 °C, and hydrogen gas was introduced to carry out the reaction. After the reaction was completed, the mixture was filtered, water was added to the filtrate, and the mixture was extracted with dichloromethane, dried, filtered, and concentrated under reduced pressure to obtain a concentrated solution. Heptane was added and stirred. After stirring, the mixture was filtered and dried to obtain the target compound 7-methyl-Omacycline. in, The solvent 6 used in step 6 is selected from one or a mixture of several of methanol, ethanol, acetonitrile, and tetrahydrofuran; In step 6, the reaction temperature is controlled at 20–30°C.

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