Method for dehydrogenating Anecorstat acetate

Abstract

The invention belongs to the technical field of steroid hormone preparation, and particularly relates to a method for dehydrogenating Anecorstat Acetate, the Anecorstat Acetate is used as a substrate, Nocardioides simplex is used as a fermentation strain, biological fermentation conversion is carried out to obtain a product C, and the structural formula of the product C is # imgabs0 #; during the biological fermentation conversion, Tween 80, methanol and PPE are also added, the weight ratio of the Anekostat acetate to the Tween 80 is 200: (0.2-2), the weight ratio of the Anekostat acetate to the methanol is 200: (10-30), and the weight ratio of the Anekostat acetate to the PPE is 200: (10-50); the yield and the purity are improved, and meanwhile the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of steroid hormone preparation, and particularly relates to a method for dehydrogenating anecortave acetate. Background Art

[0002] Anecortava acetate is a cheap and widely used steroidal intermediate. Its C(1,2) dehydrogenated product is an important intermediate for the preparation of 3TR. However, due to its extremely strong hydrophobicity and molecular spatial structure, whether it is enzyme catalysis or biological transformation, on the one hand, the hydrophobicity makes it very easy to foam, which seriously affects mass transfer, so the feed concentration is low. On the other hand, the conversion rate is low when using Arthrobacter or dehydrogenase catalysis; both cannot form efficient conversion.

[0003] Patent application CN112375114A discloses a method for preparing prednisolone acetate, wherein anecortave acetate is subjected to biological fermentation to obtain a dehydrogenated deesterified product, which is then subjected to an esterification reaction to obtain a dehydrogenated product, and the total yield and purity thereof need to be improved. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for dehydrogenating anecortave acetate, which improves the yield and purity and reduces the production cost.

[0005] The present invention provides a method for dehydrogenating anecortave acetate, using anecortave acetate as a substrate and Nocardia simplex Nocardioides simplex The fermentation strain is used to carry out biological fermentation conversion to obtain product C, and the structural formula of the product C is: ; During the biological fermentation conversion, Tween 80, methanol and PPE are also added, the weight ratio of anecortave acetate to Tween 80 is 200:0.2-2, the weight ratio of anecortave acetate to methanol is 200:10-30, and the weight ratio of anecortave acetate to PPE is 200:10-50.

[0006] The reaction route is: .

[0007] Preferably, the weight ratio of anecortave acetate to Tween 80 is 200:0.5-1.5, and the weight ratio of anecortave acetate to methanol is 200:15-25.

[0008] Preferably, the weight ratio of anecortave acetate to PPE is 200:20-40.

[0009] Preferably, Nocardia simplex Nocardioides simplex During seed culture, PPE was added to the culture medium.

[0010] Preferably, Nocardia simplex Nocardioides simplex When seed culture was performed, anecortave acetate was not added to the culture medium.

[0011] Preferably, product C is mixed with dichloromethane and 4-dimethylaminopyridine, acetic anhydride is added, and the mixture is reacted. After the reaction is completed, the mixture is filtered, concentrated, and filtered with suction to obtain filter cake 1 and filtrate 1. The filter cake 1 contains product B, and the structural formula of product B is: ; The filter cake 1, acetone and water are mixed, heated to reflux, crystallized, and filtered to obtain a filter cake 2 and a filtrate 2; The filtrate 2 is concentrated under reduced pressure and filtered to obtain a filter cake 3, wherein the filter cake 3 contains the product B; The filtrate 1 and the filter cake 2 are mixed to obtain a mother liquor, which is used as a substrate and then fed back to the Nocardia simplex culture medium. Nocardioides simplex Product C is obtained in the biological fermentation transformation of the fermentation strain.

[0012] Preferably, the weight-to-volume ratio of the product C to dichloromethane is 1 g:6-10 mL, and the weight ratio of the product C to 4-dimethylaminopyridine is 1:0.02-0.1.

[0013] Preferably, the weight-to-volume ratio of the filter cake 1 to acetone is 1 g: 20-40 mL, and the weight-to-volume ratio of the filter cake 1 to water is 1 g: 1-4 mL.

[0014] Preferably, the heating temperature for heating and reflux is 60° C., and the temperature is lowered to 40° C. before crystallization.

[0015] Preferably, the filtrate 2 is concentrated under reduced pressure, the concentrated acetone is replaced with water, the temperature is lowered to 30° C., and suction filtered to obtain a filter cake 3 The beneficial effect of the present invention is that the present invention uses Nocardia simplex ( Nocardioides simplex ACCC10205), using PPE, Tween 80 and methanol as auxiliary materials to promote the conversion of anecortave acetate. During the conversion process, the hydrolysis of the 21-position acetate and the dehydrogenation of the C(1,2) position are carried out simultaneously, and the main product is product C. Its feed concentration can be as high as 200g / L, and the dehydrogenation conversion rate can reach about 90%, which is an efficient and stable conversion solution.

[0016] The crude product obtained by bioconversion is dried and esterified to obtain a mixture of anecortave acetate dehydrogenate (product B) and anecortave acetate (substrate A), wherein the content of the dehydrogenate is about 91%. The crude product is refined using acetone to obtain a fine product of anecortave acetate dehydrogenate with a purity of 99%, and the single fine product yield is more than 70%.

[0017] The mother liquor obtained by refining is a mixture of anecortave acetate dehydrogenate and anecortave acetate, and the mixture is recycled. Compared with other mother liquors refined by the steroid C(1,2) biotransformation dehydrogenation process alone, due to the existence of the 21-position acetate hydrolysis reaction, the undehydrogenated substrates wrapped inside the crystals are more easily dissolved, which improves the efficiency of C(1,2) dehydrogenation conversion. Efficient conversion can be achieved after only simple treatment. When the feed concentration is 100g / L, the dehydrogenation rate reaches more than 88%.

[0018] The comprehensive yield of the entire process reaches more than 90%, and the purity of the finished product liquid phase detection reaches more than 99%.

[0019] Generally speaking, it is difficult to directly convert anecortave acetate to obtain product B, the conversion rate is low, and the feed concentration is also low. The present invention first converts it into product C, and then esterifies product C to obtain product B. In the process of converting the substrate into product C, the inventors found that if the feed amount of the substrate is increased, the yield and conversion rate of the product will be significantly reduced. If the feed amount of the substrate is not increased, the cost will be difficult to further reduce, and the production capacity cannot be effectively improved. In order to reduce costs, increase production capacity, and improve the effect of converting substrates into product C, the present invention adds auxiliary materials to the biological fermentation conversion system, especially PPE, and the combination of PPE, methanol, and Tween 80 simultaneously increases the feed concentration and product yield and purity.

[0020] Generally speaking, after esterification, product C undergoes C(1,2) dehydrogenation to obtain product B. The technicians are not aware of the Nocardioides simplex Product B can also be converted into product C, and it is not known that product C also contains part of substrate A. Therefore, it has no motivation to process the esterified product and return it to the fermentation substrate for conversion. After esterification, the present invention converts the separated mother liquor again to obtain product C. The mother liquor is a mixture of substrate A and product B. It is different from other steroid intermediate single dehydrogenation mother liquor reactions (single dehydrogenation mother liquor reactions require that the content of undehydrogenated substrates reaches a certain proportion in order to be successfully converted). This return conversion solves the problem of the mother liquor being unable to be converted due to crystal encapsulation. The reason is that the hydrolysis reaction of the 21-position acetate promotes crystal disintegration, and the undehydrogenated substances encapsulated in the mixed crystals are quickly released from the mother liquor mixed crystals to undergo dehydrogenation reaction, C (1,2) dehydrogenation reaction, thereby improving the conversion speed, conversion rate and yield, and further reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a product detection diagram of Example 2 of the present invention.

[0022] Figure 2 This is a product detection diagram of Example 3 of the present invention.

[0023] Figure 3 This is a detection diagram of the refined product of Example 4 of the present invention.

[0024] Figure 4 This is a product detection diagram after biological transformation and dehydrogenation of the mother liquid material in Example 4 of the present invention.

[0025] Figure 5 This is a product detection diagram of Comparative Example 1 of the present invention.

[0026] Figure 6 This is a product detection diagram of Comparative Example 2 of the present invention.

[0027] Figure 7 This is a product detection diagram of Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0028] Example 1 1. Bacterial culture 1) Slant culture, the strain is Nocardia simplex ( Nocardioides simplex , the deposit number is ACCC10205), the culture medium is 1.3% glucose, 1.3% yeast extract, 2% agar, pH=7.0, culture conditions: 3 days, 30℃. After the culture is completed, it is stored at 4℃.

[0029] 2) Primary seed culture medium The culture medium is: 0.3% beef extract (mass concentration), 0.5% peptone (mass concentration), pH 6.8. Culture conditions: half of the slant is added to 100 ml of culture medium, cultured at 180 rpm and 30°C for 24 hours.

[0030] 3) Secondary seed culture (material volume 2 liters), the culture medium composition and dosage are shown in the following table.

[0031]

[0032] 2. Conversion Before sterilization, an additional 10 g of substrate (i.e., anecortave acetate) was added to the secondary seed culture medium as an induction. The seeds were cultured for about 24 hours. When the OD of the bacterial solution was greater than 10 and no foreign bacterial contamination was found under a microscope, the bacterial solution of the secondary seed culture was obtained.

[0033] Add the treated substrate (i.e. 190 g of anecortave acetate) and auxiliary materials (1 g of Tween 80, 20 g of methanol, 20 g of PPE (polyoxyethylene polyoxypropylene pentaerythritol ether)) into the bacterial solution of the above-mentioned secondary seed culture, stir evenly, and start the transformation at a ventilation volume of 0.2 VVM, a tank pressure of 0.05 MPa, a temperature of 30°C, and a stirring speed of 650 rpm. The transformation lasts for about 140 hours and then ends.

[0034] The reaction scheme for the dehydrogenation of anecortave acetate is as follows:

[0035] The feed concentration in this embodiment is (10g+190g) / 2L=100g / L.

[0036] Conversion results: The dehydrogenation rate of anecortave acetate was 1.07% (compound B) + 88.73% (compound C) = 89.80%. The weight percentage of each reaction substance in the product is shown in the following table (the total mass of the added substrate is 100%).

[0037]

[0038] Example 2 The bacterial culture was the same as in Example 1, except for the transformation, which was as follows: In the secondary seed culture medium, before sterilization, no additional 10 g of substrate is added as an induction (i.e., no substrate is added), and the seeds are cultured for about 24 hours. When the OD of the bacterial solution is greater than 10 and there is no contamination from foreign bacteria under microscopic examination, the bacterial solution of the secondary seed culture is obtained.

[0039] Add the treated substrate (i.e., 200 g of anecortave acetate) and auxiliary materials (1 g of Tween 80, 20 g of methanol, and 20 g of PPE) to the bacterial solution of the above-mentioned secondary seed culture, stir evenly, and start transformation at a ventilation volume of 0.2 VVM, a tank pressure of 0.05 MPa, a temperature of 30°C, and a stirring speed of 650 rpm. The transformation lasts for about 140 hours and then ends.

[0040] Conversion results: The dehydrogenation rate of anecortave acetate is 1.084% (compound B) + 90.017% (compound C) = 91.101%. The weight percentage of each reaction substance in the product is shown in the following table.

[0041]

[0042] The test results of the content of each reaction substance are as follows Figure 1 shown.

[0043] Example 3 The bacterial culture was the same as in Example 1, except for the transformation, which was as follows: In the secondary seed culture medium, before sterilization, no additional 10 g of substrate is added as an induction (i.e., no substrate is added), and the seeds are cultured for about 24 hours. When the OD of the bacterial solution is greater than 10 and there is no contamination from foreign bacteria under microscopic examination, the bacterial solution of the secondary seed culture is obtained.

[0044] Add the treated substrate (i.e. 400 g of anecortave acetate) and auxiliary materials (1 g of Tween 80, 20 g of methanol, and 40 g of PPE) to the bacterial solution of the above-mentioned secondary seed culture, stir evenly, and start transformation at a ventilation volume of 0.2 VVM, a tank pressure of 0.05 MPa, a temperature of 30°C, and a stirring speed of 650 rpm. The transformation lasts for about 140 hours and then ends.

[0045] Conversion results: The dehydrogenation rate of anecortave acetate is 1.068% (compound B) + 88.733% (compound C) = 89.801%. The weight percentage of each reaction substance in the product is shown in the following table.

[0046]

[0047] The test results of the content of each reaction substance are as follows Figure 2 shown.

[0048] Comparative Example 1 The bacterial culture was the same as in Example 1, except for the transformation, which was as follows: In the secondary seed culture medium, before sterilization, no additional 10 g of substrate is added as an induction (i.e., no substrate is added), and the seeds are cultured for about 24 hours. When the OD of the bacterial solution is greater than 10 and there is no contamination from foreign bacteria under microscopic examination, the bacterial solution of the secondary seed culture is obtained.

[0049] Add the treated substrate (i.e., 200 g of anecortave acetate) and auxiliary materials (1 g of Tween 80, 20 g of methanol, and 20 g of PPG2000) to the bacterial solution of the above-mentioned secondary seed culture, stir evenly, and start the transformation at a ventilation volume of 0.2 VVM, a tank pressure of 0.05 MPa, a temperature of 30°C, and a stirring speed of 650 rpm. The transformation lasts for about 136 hours and then ends.

[0050] Conversion results: The dehydrogenation rate of anecortave acetate is 1.068% (compound B) + 65.151% (compound C) = 66.219%. The weight percentage of each reaction substance in the product is shown in the following table.

[0051]

[0052] The test results of the content of each reaction substance are as follows Figure 5 shown.

[0053] Comparative Example 2 The bacterial culture was the same as in Example 1, except for the transformation, which was as follows: In the secondary seed culture medium, before sterilization, no additional 10 g of substrate is added as an induction (i.e., no substrate is added), and the seeds are cultured for about 24 hours. When the OD of the bacterial solution is greater than 10 and there is no contamination from foreign bacteria under microscopic examination, the bacterial solution of the secondary seed culture is obtained.

[0054] Add the treated substrate (i.e. 200 g of anecortave acetate) and auxiliary materials (1 g of Tween 80, 20 g of methanol, and 20 g of silicone oil) to the bacterial solution of the above-mentioned secondary seed culture, stir evenly, and start transformation at a ventilation volume of 0.2 VVM, a tank pressure of 0.05 MPa, a temperature of 30°C, and a stirring speed of 650 rpm. The transformation lasts for about 140 hours and then ends.

[0055] Conversion results: The dehydrogenation rate of anecortave acetate is 1.096% (compound B) + 77.075% (compound C) = 78.171%. The weight percentage of each reaction substance in the product is shown in the following table.

[0056]

[0057] The test results of the content of each reaction substance are as follows Figure 6 shown.

[0058] Comparative Example 3 The bacterial culture was the same as in Example 1, except for the transformation, which was as follows: In the secondary seed culture medium, before sterilization, no additional 10 g of substrate is added as an induction (i.e., no substrate is added), and the seeds are cultured for about 24 hours. When the OD of the bacterial solution is greater than 10 and there is no contamination from foreign bacteria under microscopic examination, the bacterial solution of the secondary seed culture is obtained.

[0059] Add the treated substrate (i.e. 200 g of anecortave acetate) and auxiliary materials (1 g of Tween 80, 20 g of methanol) to the bacterial solution of the above-mentioned secondary seed culture, stir evenly, and start the transformation at a ventilation volume of 0.2 VVM, a tank pressure of 0.05 MPa, a temperature of 30°C, a stirring speed of 650 rpm. The transformation lasts for about 140 hours and then ends.

[0060] Conversion results: The dehydrogenation rate of anecortave acetate is 0.596% (compound B) + 79.543% (compound C) = 80.139%. The weight percentage of each reaction substance in the product is shown in the following table.

[0061]

[0062] The test results of the content of each reaction substance are as follows Figure 7 shown.

[0063] Comparative Example 4 The bacterial culture was the same as in Example 1, except for the transformation, which was as follows: In the secondary seed culture medium, before sterilization, no additional 10 g of substrate is added as an induction (i.e., no substrate is added), and the seeds are cultured for about 24 hours. When the OD of the bacterial solution is greater than 10 and there is no contamination from foreign bacteria under microscopic examination, the bacterial solution of the secondary seed culture is obtained.

[0064] Add the treated substrate (i.e. 200 g of anecortave acetate) and auxiliary materials (20 g of PPE, 3 g of Tween 80, 40 g of methanol) to the bacterial solution of the above-mentioned secondary seed culture, stir evenly, and start transformation at a ventilation volume of 0.2 VVM, a tank pressure of 0.05 MPa, a temperature of 30°C, a stirring speed of 650 rpm. The transformation lasts for 140 hours and then ends.

[0065] Conversion results: The dehydrogenation rate of anecortave acetate is 1.537% (compound B) + 83.871% (compound C) = 85.408%. The weight percentage of each reaction substance in the product is shown in the following table.

[0066]

[0067] Comparative Example 5 The bacterial culture was the same as in Example 1, except for the transformation, which was as follows: In the secondary seed culture medium, before sterilization, no additional 10 g of substrate is added as an induction (i.e., no substrate is added), and the seeds are cultured for about 24 hours. When the OD of the bacterial solution is greater than 10 and there is no contamination from foreign bacteria under microscopic examination, the bacterial solution of the secondary seed culture is obtained.

[0068] Add 200 g of the treated anecortave acetate dehydrogenation hydrolyzate (substance D) and auxiliary materials (1 g Tween 80, 20 g methanol, 20 g PPE) to the bacterial solution of the above-mentioned secondary seed culture, stir evenly, and start the transformation at a ventilation volume of 0.2 VVM, a tank pressure of 0.05 MPa, a temperature of 30°C, a stirring speed of 650 rpm. The transformation lasts for 166 hours and then ends.

[0069] Conversion results: The dehydrogenation rate is 12.863% (Compound C). The weight percentage of each reaction substance in the product is shown in the following table.

[0070]

[0071] Example 4 The crude product is esterified in the following steps: 1) The product obtained by the conversion of Example 1 was filtered, the filter cake was rinsed with clean water, and suction was filtered until no liquid was dripped, the filter cake was scooped out and dried, and 184.2 g of white solid was obtained.

[0072] Under stirring conditions, 1650 ml of dichloromethane, 184.2 g of the above white solid (ie, crude dehydrogenation product) and 7.4 g of DMAP (4-dimethylaminopyridine) were added to the dry reaction bottle and stirred for 20 min.

[0073] 2) Replace the reaction flask with nitrogen and cool the reactor to 12°C.

[0074] 3) Under nitrogen protection, add 200g of acetic anhydride dropwise at controlled temperature.

[0075] 4) After the addition is completed, the temperature is raised to 25°C and kept warm for 3 hours. The reaction endpoint is determined by TLC tracking when the raw material point disappears completely.

[0076] 5) After the reaction, cool to 15°C and slowly add 220 g of methanol to quench the reaction.

[0077] 6) After the addition is complete, stir at 20°C for 2 hours.

[0078] 7) Filter the system to remove the bacterial residue and filter the filtrate into another reactor.

[0079] 8) Concentrate dichloromethane under normal pressure to an internal temperature of 50°C, cool to 4°C, and filter with suction. The filter cake obtained is 179.2 g of crude product of anecortave acetate dehydrogenate. Concentrate the filtrate to dryness to obtain 18.1 g of "mother liquor 1".

[0080] The reaction route is: .

[0081] Refining, steps are: 179.2 g of the obtained crude anecortave acetate dehydrogenate was added to 20 times the volume of acetone (i.e., 1 g of crude anecortave acetate dehydrogenate was added to 20 mL of acetone), and 2 times the volume of water (i.e., 1 g of crude anecortave acetate dehydrogenate was added to 2 mL of water), the temperature was raised to 60°C and refluxed to dissolve, the temperature was lowered to 40°C, and the crystal was grown with stirring for 30 minutes, filtered, and the filter cake obtained was dried to obtain 34.1 g of "mother liquor 2".

[0082] The obtained filtrate was concentrated to dryness under reduced pressure, and the concentrated acetone was replaced with water, cooled to 30°C, filtered, and the obtained filter cake was dried to obtain 143.4 g of anecortave acetate dehydrogenate product, with a liquid phase normalized content of 99.339% and a mass yield of 71.7% relative to the substrate. The test results of the content of each substance are as follows Figure 3 shown.

[0083] The mother liquor is bioconverted and dehydrogenated, and the steps are: The obtained mother liquor 1 and mother liquor 2 were mixed to obtain 52.2 g of mother liquor, with a yield of 26.1% relative to the substrate.

[0084] 52.2 g of the mother liquid was used as a substrate and put into 500 mL of the secondary seed culture solution of Example 1 for conversion. The conversion lasted for 88 hours, and the dehydrogenation rate was 11.169% (compound B) + 77.005% (compound C) = 88.174%. After filtration and drying, 45.8 g of off-white solid was obtained. The test results of the content of each substance are as follows: Figure 4 shown.

[0085] Comparative Example 6 Product D and product C are mixed and recrystallized to obtain mixed crystals of D and C, in which C accounts for 42.345% and D accounts for 56.516%.

[0086] According to the conversion and dehydrogenation steps of "mother liquor biological conversion and dehydrogenation" in Example 4, an equal amount of D and C mixed crystals were taken for dehydrogenation conversion. The conversion was carried out for 96 hours. The conversion effect was poor. In the liquid phase detection product, C accounted for 54.890% and D accounted for 43.674%. The conversion effect could not meet the expected standard.

[0087] A person skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of protection of the present application is limited to these examples. In line with the concept of the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0088] One or more embodiments of the present application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the present application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present application should be included in the protection scope of the present application.

Claims

1. A method for dehydrogenating anecortave acetate, characterized in that: Using anecortave acetate as substrate, Nocardia simplex Nocardioides simplex The fermentation strain is used to carry out biological fermentation conversion to obtain product C, and the structural formula of the product C is: ； During the biological fermentation conversion, Tween 80, methanol and PPE are also added, the weight ratio of anecortave acetate to Tween 80 is 200:0.2-2, the weight ratio of anecortave acetate to methanol is 200:10-30, and the weight ratio of anecortave acetate to PPE is 200:10-50.

2. The method according to claim 1, characterized in that: The weight ratio of anecortave acetate to Tween 80 is 200:0.5-1.5, and the weight ratio of anecortave acetate to methanol is 200:15-25.

3. The method according to claim 1, characterized in that: The weight ratio of anecortave acetate to PPE is 200:20-40.

4. The method according to claim 1, characterized in that: Nocardia simplex Nocardioides simplex During seed culture, PPE was added to the culture medium.

5. The method according to claim 1, characterized in that: Nocardia simplex Nocardioides simplex When seed culture was performed, anecortave acetate was not added to the culture medium.

6. The method according to any one of claims 1 to 5, characterized in that: Product C is mixed with dichloromethane and 4-dimethylaminopyridine, and acetic anhydride is added to react. After the reaction is completed, the mixture is filtered, concentrated, and filtered with suction to obtain filter cake 1 and filtrate 1. The filter cake 1 contains product B, and the structural formula of product B is: ； The filter cake 1, acetone and water are mixed, heated to reflux, crystallized, and filtered to obtain a filter cake 2 and a filtrate 2; The filtrate 2 is concentrated under reduced pressure and filtered to obtain a filter cake 3, wherein the filter cake 3 contains the product B; The filtrate 1 and the filter cake 2 are mixed to obtain a mother liquor, which is used as a substrate and then fed back to the Nocardia simplex culture medium. Nocardioides simplex Product C is obtained in the biological fermentation transformation of the fermentation strain.

7. The method according to claim 6, characterized in that: The weight-to-volume ratio of the product C to dichloromethane is 1 g:6-10 mL, and the weight ratio of the product C to 4-dimethylaminopyridine is 1:0.02-0.

1.

8. The method according to claim 6, characterized in that: The weight-to-volume ratio of the filter cake 1 to acetone is 1 g: 20-40 mL, and the weight-to-volume ratio of the filter cake 1 to water is 1 g: 1-4 mL.

9. The method according to claim 6, characterized in that: The heating temperature for heating reflux was 60°C, and the temperature was lowered to 40°C before crystallization.

10. The method according to claim 6, characterized in that: The filtrate 2 was concentrated under reduced pressure, the concentrated acetone was replaced with water, the temperature was lowered to 30° C., and suction filtered to obtain a filter cake 3.

Images