Preparation method of 1-N-ethyl gentamicin C1a sulfate

Abstract

The invention discloses a preparation method of 1-N-ethyl gentamicin C1a sulfate. The preparation method comprises the following steps: generating a gentamicin C1a-Zn complex from gentamicin C1a and zinc acetate; the preparation method comprises the following steps: reacting a gentamicin C1a-Zn complex with di-tert-butyl dicarbonate ester under the catalysis of potassium carbonate to generate a 3, 2 ', 6'-tri-N-t-butyloxycarbonyl gentamicin C1a-Zn complex; and decomplexing to obtain the 3, 2 ', 6'-tri-N-t-butyloxycarboryl gentamicin C1a. Carrying out a silanization reaction on the silicon dioxide and hexamethyldisilazane; carrying out N-alkylation reaction on the obtained product and acetaldehyde, and then adding potassium borohydride for reduction; and carrying out hydrolysis reaction on the obtained product in dilute sulphuric acid, adding an anti-solvent after hydrolysis is completed, crystallizing, filtering, and drying to obtain a finished product of the 1-N-ethyl gentamicin C1a sulfate. The reaction conditions are mild, the whole process is carried out at room temperature, the purification operation is simplified, and a green production process is realized.

Description

Technical Field

[0001] This invention relates to the field of medicinal chemistry, specifically to a method for preparing 1-N-ethylgentamicin C1a sulfate. Background Technology

[0002] 1-N-ethylgentamicin C1a sulfate is a new generation of semi-synthetic aminoglycoside antibiotic that is highly effective, low in toxicity, and effective against drug-resistant bacteria.

[0003] The preparation method of 1-N-ethylgentamicin C1a sulfate disclosed in Chinese patent document CN 101928312 B (application number 201010132963.9) includes the following steps: gentamicin C1a and zinc acetate undergo a coordination reaction in methanol solvent, followed by dropwise addition of a mixture of acetic anhydride, triethylamine, and tetrahydrofuran for acylation. After post-treatment, 3,2',6'-tris-N-acetylgentamicin C1a is obtained. Then, it undergoes a silylation reaction with hexamethyldisilazane in chloroform solvent, followed by an N-alkylation reaction with acetaldehyde in dichloroform solvent, and a reduction reaction with potassium borohydride. Hydrolysis is then performed with NaOH solution, and after post-treatment, 1-N-ethylgentamicin C1a is obtained. 1-N-ethylgentamicin C1a was dissolved in anhydrous ethanol or anhydrous methanol by stirring, then concentrated sulfuric acid was added dropwise, and after post-treatment, 1-N-ethylgentamicin C1a sulfate was obtained.

[0004] Chinese patent document CN 105524129 B (application number 201510998419.5) discloses a method for preparing etimicin sulfate, comprising the following steps: Gentamicin C1a base is dissolved in a certain proportion of solvent, a certain proportion of complexing agent is added for complexation, a certain proportion of amino protecting agent is added, the mixture is maintained for a certain time, a certain proportion of precipitant is added, the mixture is stirred, and then filtered. A certain proportion of acetylation reagent is added to the filtrate, and the mixture is reacted for a certain time. A certain proportion of reducing agent is added, and the mixture is reacted for a certain time to remove the amino protecting group. A certain proportion of water is added, and the mixture is concentrated under vacuum under certain conditions to remove the solvent. The pH is adjusted with ammonia, and the mixture is adsorbed onto a macroporous resin. The mixture is then purified by gradient separation with dilute ethanol. A solution of a certain purity is collected, concentrated under vacuum under certain conditions, and then sulfuric acid is added to adjust the pH. A certain proportion of activated carbon is added for decolorization, and the mixture is filtered and dried. In this method, the complexing agent is one of cobalt acetate, copper acetate, zinc acetate, cobalt sulfate, copper sulfate, or zinc sulfate, and the amino protecting agent is triphenylmethyl chloride.

[0005] In addition, Chinese patents CN93112412, CN201010132962.4, CN201310691184.6, CN201410525775.0 and CN201410107616.9 also disclose methods for preparing 1-N-ethylgentamicin C1a sulfate. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing 1-N-ethylgentamicin C1a sulfate with mild reaction conditions, simplified steps, and high yield and purity.

[0007] The technical solution for achieving the objective of this invention is a method for preparing 1-N-ethylgentamicin C1a sulfate, comprising the following steps: ① Gentamicin C1a and zinc acetate undergo a coordination reaction in methanol to form a gentamicin C1a-Zn complex.

[0008] ② The gentamicin C1a-Zn complex reacts with di-tert-butyl dicarbonate under potassium carbonate catalysis to generate 3,2',6'-tris-N-tert-butyloxycarbonylgentamicin C1a-Zn complex. After the reaction is complete, the solvent methanol is removed to obtain a concentrated solution.

[0009] ③ Dissolve the concentrated solution obtained in step ② in dichloromethane, add water, shake and let stand to separate the layers, take the dichloromethane phase, add an inert solvent, the product solid precipitates, filter and dry to obtain 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a.

[0010] ④ The 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a obtained in step ③ is refluxed with hexamethyldisilazane in chloroform solvent under concentrated sulfuric acid catalysis to carry out silylation reaction. After the reaction is completed, chloroform is removed.

[0011] ⑤ The product obtained in step ④ is reacted with acetaldehyde in dichloromethane solvent at a temperature of 0℃~10℃ for N-alkylation reaction. Then potassium borohydride is added for reduction. After the reaction is complete, dichloromethane is removed by distillation.

[0012] ⑥ The product obtained in step ⑤ is reacted in sulfuric acid. After the reaction is complete, an antisolvent is added for crystallization, followed by filtration and drying to obtain 1-N-ethylgentamicin C1a sulfate product.

[0013] In step ① above, the weight ratio of zinc acetate to gentamicin C1a is 1:1 to 2:1; the weight ratio of methanol to gentamicin C1a is 7:1 to 15:1.

[0014] In step ② above, the weight ratio of di-tert-butyl dicarbonate to gentamicin C1a is 1.5:1 to 2:1; the weight ratio of potassium carbonate to gentamicin C1a is 0.1:1 to 0.5:1.

[0015] In step ② above, the reaction temperature is 15℃~35℃ and the reaction time is 10~20h.

[0016] In step ③ above, the inert solvent is one or a combination of more than one of diethyl ether, n-hexane, n-heptane, and methyl tert-butyl ether.

[0017] In step ④ above, the weight ratio of hexamethyldisilazane to 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a is 1~2:1; the weight ratio of concentrated sulfuric acid to 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a is 1:50~1:100.

[0018] In step ⑤ above, the weight ratio of concentrated sulfuric acid to 3,2',6'-tris-N-tert-butyloxycarbonylgentamicin C1a is 1:50 to 1:100; the weight ratio of acetaldehyde to 3,2',6'-tris-N-tert-butyloxycarbonylgentamicin C1a is 0.3:1 to 0.5:1.

[0019] In step ⑤ above, the weight ratio of potassium borohydride to 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a is 0.1:1 to 0.2:1.

[0020] In step ⑥ above, the molar ratio of H2SO4 in sulfuric acid to gentamicin C1a is 3~6:1.

[0021] In step ⑥ above, the antisolvent is anhydrous ethanol and / or methanol, and the amount used is 1 to 2 times the volume of dilute sulfuric acid.

[0022] This invention has positive effects: (1) In step ② of the present invention, when protecting the amino group, the present invention uses tert-butoxycarbonyl as the amino protecting group and potassium carbonate as the catalyst. The reaction is carried out at 15℃~35℃, which makes the reaction milder and more selective. The yield of intermediate 3,2',6'-tris-N-tert-butoxycarbonyl gentamicin C1a obtained by this step is over 98%, and the purity is over 99%.

[0023] (2) In step ② of the present invention, potassium carbonate and ditert-butyl dicarbonate are directly added to the reaction solution obtained in step ① without the use of organic solvents. Therefore, in step ③, the extraction method is used instead of column chromatography to remove zinc ions, which reduces the discharge of a large amount of organic waste liquid, saves energy, shortens the construction period, and realizes green production process.

[0024] (3) In step ③ of the present invention, an inert solvent is added directly to crystallize, and a solid product is obtained while purifying. The operation is simple and avoids a lot of tedious operations such as column chromatography, concentration and freeze drying.

[0025] (4) In step ⑥ of the present invention, the deprotection group and salt formation reaction are completed in this step.

[0026] Tert-butyloxycarbonyl can be hydrolyzed at room temperature under acidic conditions. The removed protecting group generates gas and is discharged, so there is no residue in the reaction system. This avoids the problem that traditional acetyl protecting groups need to be hydrolyzed at high temperature under sodium hydroxide conditions for a long time (more than 20 hours). It greatly reduces the generation of side reactions and the hydrolysate obtained has high purity. There is no need for macroporous resin or ion exchange resin column chromatography. High-purity products can be obtained by crystallization alone.

[0027] (5) The purity of 1-N-ethylgentamicin C1a sulfate prepared by the present invention reaches more than 99%, and the total yield of the route reaches more than 70%. Attached Figure Description

[0028] Figure 1 This is a synthetic route diagram of the present invention.

[0029] Figure 2 The HPLC chromatogram of 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a prepared in Example 1.

[0030] Figure 3 The mass spectrum of 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a prepared in Example 1.

[0031] Figure 4 The nuclear magnetic resonance (NMR) 1H spectrum of 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a prepared in Example 1.

[0032] Figure 5 The nuclear magnetic resonance C1a spectrum of 3,2',6'-tris-N-tert-butoxycarbonylgentamicin prepared in Example 1.

[0033] Figure 6 The infrared spectrum of 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a prepared in Example 1.

[0034] Figure 7 The HPLC chromatogram of 1-N-ethylgentamicin C1a sulfate prepared in Example 1 is shown.

[0035] Figure 8 This is the HPLC chromatogram of the reference solution.

[0036] Figure 9 The mass spectrum of 1-N-ethylgentamicin C1a sulfate prepared in Example 1 is shown.

[0037] Figure 10 The nuclear magnetic resonance (NMR) H-spectrum of 1-N-ethylgentamicin C1a sulfate prepared in Example 1.

[0038] Figure 11 The nuclear magnetic resonance C-ray spectra of 1-N-ethylgentamicin C1a sulfate prepared in Example 1.

[0039] Figure 12 The infrared spectrum of 1-N-ethylgentamicin C1a sulfate prepared in Example 1. Detailed Implementation

[0040] The following describes some of the possible embodiments of the present invention, intended to provide a basic understanding of the invention, and is not intended to identify the key or decisive elements of the invention or limit the scope of protection. It is readily understood that, based on the technical solutions of the present invention, those skilled in the art can propose other interchangeable implementations without altering the essential spirit of the invention. Therefore, the following specific embodiments are merely illustrative examples of the technical solutions of the present invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solutions of the present invention.

[0041] (Example 1) See Figure 1 The preparation method of 1-N-ethylgentamicin C1a sulfate in this embodiment includes the following steps: ① In a 3L reaction flask, add 700g methanol, 100g gentamicin C1a and 150g zinc acetate, and stir the mixture at 15℃~35℃ (20℃ in this example) for 2 hours to generate gentamicin C1a-Zn complex.

[0042] ② Add 10g of potassium carbonate and 170g of di-tert-butyl dicarbonate to the system after the reaction in step ①, and continue to stir the reaction at 15℃~35℃ (20℃ in this example) for 10~20h (15h in this example) to generate 3,2',6'-tris-N-tert-butyloxycarbonylgentamicin C1a-Zn complex. After the reaction is complete, distill to remove methanol to obtain concentrated solution.

[0043] ③ Dissolve the concentrated solution obtained in step ② in 300 mL of dichloromethane, add 300 mL of water, shake, and let stand to separate the layers.

[0044] Take the dichloromethane phase, add 600 mL of diethyl ether, the product solid precipitates, filter and dry to obtain 164.4 g of 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a product.

[0045] The HPLC chromatogram of 3,2',6'-tris-N-tert-butyloxycarbonyl gentamicin C1a obtained in this step is shown in [reference needed]. Figure 2 Mass spectrum can be found Figure 3 The nuclear magnetic resonance H-ray spectrum is shown below. Figure 4 See the C-NMR spectrum. Figure 5 Infrared spectrum (see) Figure 6 .

[0046] ④ Add 650g of chloroform to a dry 2L flask, add 130g of 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a obtained in step ③, stir to dissolve, add 200g of hexamethyldisilazane and 2.6g of concentrated sulfuric acid (concentration above 70%, 75% in this example), heat to reflux for 6 hours, and then concentrate by rotary evaporation to dryness of chloroform.

[0047] ⑤ Dissolve the product obtained in step ④ in 650g of dichloromethane, cool it to below 10℃, add 1.3g of concentrated sulfuric acid and 39g of acetaldehyde, react at 0℃~10℃ for 0.5 hours, then add 13g of potassium borohydride for reduction reaction for 0.5 hours, then add 260g of borate buffer, react for 1 hour, after the reaction is complete, separate the aqueous phase and remove the dichloromethane from the organic phase by distillation.

[0048] ⑥ Add 200 mL of 4M sulfuric acid solution to the system obtained after removing dichloromethane in step ⑤, and carry out the hydrolysis reaction at room temperature (15℃~35℃) for 2 hours. After the reaction is completed, slowly add 500 mL of anhydrous ethanol. A white solid precipitates out. Continue stirring for 3 hours after the addition is complete. Filter and dry to obtain 99.4 g of solid with a purity of 99.1%. The overall yield of the route is 71% (based on 1-N-ethylgentamicin C1a).

[0049] The mass spectrum of 1-N-ethylgentamicin C1a sulfate prepared in this embodiment is shown in the figure. Figure 9 The nuclear magnetic resonance H-ray spectrum is shown below. Figure 10 See the C-NMR spectrum. Figure 11 Infrared spectrum (see) Figure 12 It was confirmed that 1-N-ethylgentamicin C1a sulfate was prepared according to the above method.

[0050] The purity of 1-N-ethylgentamicin C1a sulfate prepared in this embodiment was tested, and related substances were determined according to high performance liquid chromatography (General Chapter 0512 of Chinese Pharmacopoeia 2020).

[0051] Test solution: Take an appropriate amount of the product prepared in this example, add the mobile phase to dissolve and dilute to prepare a solution containing approximately 0.25 mg of 1-N-ethylgentamicin C1a per 1 mL.

[0052] Control solution: Accurately measure 1 mL of the test solution and place it in a 100 mL volumetric flask. Dilute to the mark with the mobile phase and shake well.

[0053] System suitability solution: Take appropriate amounts of 1-N-ethylgentamicin C1a reference standard and netilmicin standard, dissolve and dilute them in the mobile phase to prepare a mixed solution containing approximately 0.025 mg of each per ml.

[0054] Sensitivity solution: Accurately measure an appropriate amount of the control solution and quantitatively dilute it with the mobile phase to prepare a solution containing approximately 0.25 μg of 1-N-ethylgentamicin C1a per 1 mL.

[0055] Chromatographic conditions: Octadecylsilane-bonded silica gel was used as the packing material (4.6 mm × 250 mm, 5 μm or equivalent column). The mobile phase was 0.2 mol / L trifluoroacetic acid solution (containing 0.05% pentafluoropropionic acid, 1.5 g / L anhydrous sodium sulfate, and 0.8% (v / v) 50% sodium hydroxide solution, with pH adjusted to 3.5 using 50% sodium hydroxide solution) - acetonitrile (96:4). The flow rate was 1.0 mL / min, and the column temperature was 35 °C. Detection was performed using an integrating pulsed amperometric electrochemical detector. The detection electrode was a gold electrode (3 mm diameter recommended), the reference electrode was an Ag / AgCl composite electrode, and the counter electrode was a titanium alloy electrode. Four detection potential waveforms were used (see table below). Alkali (50% sodium hydroxide solution 1→25, recommended flow rate 0.5 mL / min) was added after the column. The injection volume was 25 μL.

[0056] System suitability requirements: In the system suitability solution chromatogram, the resolution between the 1-N-ethylgentamicin C1a peak and the netilmicin peak should be greater than 4.0. In the sensitivity solution chromatogram, the signal-to-noise ratio of the peak height of the 1-N-ethylgentamicin C1a peak should be greater than 10.

[0057] Determination method: Accurately measure the test solution and the control solution, inject them into the liquid chromatograph, and record the chromatograms up to three times the retention time of the main component peak.

[0058] Limits: If impurity peaks are present in the chromatogram of the test solution, the netilmicin peak area, calculated based on the corrected peak area (multiplied by a correction factor of 0.8), shall not exceed 2.5 times (2.5%) the area of ​​the main peak of the control solution. The area of ​​any other single impurity peak shall not exceed 2.5 times (2.5%) the area of ​​the main peak of the control solution. The sum of the corrected peak areas of all impurities shall not exceed 5 times (5.0%) the area of ​​the main peak of the control solution. Peaks smaller than the area of ​​the main peak of the sensitivity solution shall be ignored.

[0059] The HPLC chromatogram of the test sample prepared from 1-N-ethylgentamicin C1a sulfate in Example 1 is shown in [Figure 1]. Figure 7 The reference solution chromatogram is shown below. Figure 8 .

[0060] Calculation formula: .

[0061] The calculation results are as follows: .

[0062] Analysis and testing showed that the total impurities were 0.9% and the purity was 99.1%, which is better than the requirements of the Chinese Pharmacopoeia.

[0063] (Example 2) The preparation method of 1-N-ethylgentamicin C1a sulfate in this embodiment includes the following steps: ① In a 3L reaction flask, add 1000g methanol, 100g gentamicin C1a and 100g zinc acetate, and stir the mixture at 15℃ for 2 hours to generate gentamicin C1a-Zn complex.

[0064] ② Add 30g of potassium carbonate and 150g of di-tert-butyl dicarbonate to the system after the reaction in step ①, and continue to stir the reaction at 15℃~35℃ for 18h. After the reaction is completed, remove methanol by vacuum distillation.

[0065] ③ Disperse the concentrated solution obtained in step ② in 300 mL of dichloromethane, add 500 mL of water, shake, and let stand to separate into layers.

[0066] Take the dichloromethane phase, add 500 mL of n-hexane, the product solid precipitates, filter and dry to obtain 163.7 g of 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a product.

[0067] ④ Add 1300g of chloroform and 130g of 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a obtained in step ③ to a dry 2L flask, stir to dissolve, add 260g of hexamethyldisilazane and 2.0g of concentrated sulfuric acid, heat to reflux for 6 hours, and then concentrate by rotary evaporation to dryness of chloroform.

[0068] ⑤ Dissolve the product obtained in step ④ in 1000g of dichloromethane, cool it to below 10℃, add 2.6g of concentrated sulfuric acid and 50g of acetaldehyde, and react at 0℃~10℃ for 0.5 hours. After the reaction is complete, add 16g of potassium borohydride for reduction reaction for 0.5 hours, then add 300g of borate buffer and react for 1 hour. After the reaction is complete, separate the aqueous phase and remove the dichloromethane by distillation of the organic phase.

[0069] ⑥ Add 180 mL of 5M sulfuric acid solution to the system obtained after removing dichloromethane in step ⑤, and carry out the hydrolysis reaction at room temperature (15℃~35℃) for 4 hours. After the reaction is completed, slowly add 600 mL of methanol to the reaction product. A white solid precipitates out. After the addition is complete, continue stirring for 3 hours, filter, and dry to obtain 100.2 g of solid with a purity of 99.0%. The overall yield of the route is 71.6% (based on 1-N-ethylgentamicin C1a).

[0070] (Example 3) See Figure 1 The preparation method of 1-N-ethylgentamicin C1a sulfate in this embodiment includes the following steps: ① In a 3L reaction flask, add 1500g methanol, 100g gentamicin C1a and 200g zinc acetate, and stir at 30℃ for 2 hours to generate gentamicin C1a-Zn complex.

[0071] ② Add 50g of potassium carbonate and 200g of di-tert-butyl dicarbonate to the system after the reaction in step ①, and continue to stir the reaction at 15℃~35℃ for 20h. After the reaction is completed, remove methanol by vacuum distillation to obtain a concentrated solution.

[0072] ③ Disperse the concentrated solution obtained in step ② in 300 mL of dichloromethane, add 600 mL of water, shake, and let stand to separate into layers.

[0073] Take the dichloromethane phase and add a mixture of methyl tert-butyl ether (300 ml) and n-heptane (300 ml). The product solid precipitates out, and after filtration and drying, 163.9 g of 3,2',6'-tris-N-tert-butyloxycarbonyl gentamicin C1a product is obtained.

[0074] ④ Add 1000g of chloroform to a dry 2L flask, add 130g of 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a obtained in step ③, stir to dissolve, add 130g of hexamethyldisilazane and 1.3g of concentrated sulfuric acid, heat to reflux for 6 hours, and then concentrate by rotary evaporation to dryness of chloroform.

[0075] ⑤ Dissolve the product obtained in step ④ in 1300g of dichloromethane, cool it to below 10℃, add 2g of concentrated sulfuric acid and 65g of acetaldehyde, and react at 0℃~10℃ for 0.5 hours. After the reaction is complete, add 26g of potassium borohydride for reduction reaction for 0.5 hours, then add 300g of borate buffer and react for 1 hour. After the reaction is complete, separate the aqueous phase and remove the dichloromethane by distillation of the organic phase.

[0076] ⑥ Add 180 mL of 5M sulfuric acid solution to the system obtained in step ⑤ and carry out hydrolysis reaction at room temperature for 3 hours. After the reaction is completed, slowly add a mixture of 540 mL of methanol and 360 mL of ethanol to the reaction product. A white solid precipitates out. After the addition is complete, continue stirring for 3 hours, filter, and dry the solid to obtain 101.5 g with a purity of 99.1% and an overall yield of 72.5% (based on 1-N-ethylgentamicin C1a).

Claims

1. A method for preparing 1-N-ethylgentamicin C1a sulfate, characterized in that... Includes the following steps: ① Gentamicin C1a and zinc acetate undergo a coordination reaction in methanol to form a gentamicin C1a-Zn complex; ② The gentamicin C1a-Zn complex reacts with ditert-butyl dicarbonate under potassium carbonate catalysis to generate 3,2',6'-tris-N-tert-butyloxycarbonylgentamicin C1a-Zn complex. After the reaction is complete, methanol is removed to obtain a concentrated solution. ③ Dissolve the concentrated solution obtained in step ② in dichloromethane, add water, shake and let stand to separate the layers, take the dichloromethane phase, add an inert solvent, the product solid precipitates, filter and dry to obtain 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a; ④ The 3,2',6'-tris-N-tert-butoxycarbonyl gentamicin C1a obtained in step ③ is refluxed with hexamethyldisilazane in chloroform solvent under concentrated sulfuric acid catalysis to carry out silylation reaction. After the reaction is completed, chloroform is removed. ⑤ The product obtained in step ④ is reacted with acetaldehyde in dichloromethane solvent at a temperature of 0℃~10℃ for N-alkylation reaction. Then potassium borohydride is added for reduction. After the reaction is complete, dichloromethane is removed by distillation. ⑥ The product obtained in step ⑤ is reacted in sulfuric acid. After the reaction is complete, an antisolvent is added for crystallization, followed by filtration and drying to obtain 1-N-ethylgentamicin C1a sulfate product.

2. The method for preparing 1-N-ethylgentamicin C1a sulfate according to claim 1, characterized in that: In step ①, the weight ratio of zinc acetate to gentamicin C1a is 1:1 to 2:1; the weight ratio of methanol to gentamicin C1a is 7:1 to 15:

1.

3. The method for preparing 1-N-ethylgentamicin C1a sulfate according to claim 1, characterized in that: In step ②, the weight ratio of ditert-butyl dicarbonate to gentamicin C1a is 1.5:1 to 2:1; the weight ratio of potassium carbonate to gentamicin C1a is 0.1:1 to 0.5:

1.

4. The method for preparing 1-N-ethylgentamicin C1a sulfate according to claim 3, characterized in that: In step ②, the reaction temperature is 15℃~35℃ and the reaction time is 10~20h.

5. The method for preparing 1-N-ethylgentamicin C1a sulfate according to claim 1, characterized in that: In step ③, the volume ratio of water to dichloromethane is 1 to 2:1; the inert solvent is one or a combination of more than one of diethyl ether, n-hexane, n-heptane, and methyl tert-butyl ether.

6. The method for preparing 1-N-ethylgentamicin C1a sulfate according to claim 1, characterized in that: In step ④, the weight ratio of hexamethyldisilazane to 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a is 1 to 2:1; the weight ratio of concentrated sulfuric acid to 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a is 1:50 to 1:

100.

7. The method for preparing 1-N-ethylgentamicin C1a sulfate according to claim 1, characterized in that: In step ⑤, the weight ratio of concentrated sulfuric acid to 3,2',6'-tris-N-tert-butyloxycarbonylgentamicin C1a is 1:50 to 1:100; the weight ratio of acetaldehyde to 3,2',6'-tris-N-tert-butyloxycarbonylgentamicin C1a is 0.3:1 to 0.5:

1.

8. The method for preparing 1-N-ethylgentamicin C1a sulfate according to claim 7, characterized in that: In step ⑤, the weight ratio of potassium borohydride to 3,2',6'-tris-N-tert-butyloxycarbonylgentamicin C1a is 0.1:1 to 0.2:

1.

9. The method for preparing 1-N-ethylgentamicin C1a sulfate according to claim 1, characterized in that: In step ⑥, the molar ratio of H2SO4 in sulfuric acid to gentamicin C1a is 3–6:

1.

10. The method for preparing 1-N-ethylgentamicin C1a sulfate according to claim 1, characterized in that: In step ⑥, the antisolvent is anhydrous ethanol and / or methanol, and the amount used is 1 to 2 times the volume of sulfuric acid.

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