CN116102532A - Method for recovering lipoic acid from lipoic acid crystallization mother liquor - Google Patents
Method for recovering lipoic acid from lipoic acid crystallization mother liquor Download PDFInfo
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- C07D—HETEROCYCLIC COMPOUNDS
- C07D339/00—Heterocyclic compounds containing rings having two sulfur atoms as the only ring hetero atoms
- C07D339/02—Five-membered rings
- C07D339/04—Five-membered rings having the hetero atoms in positions 1 and 2, e.g. lipoic acid
Abstract
The invention belongs to the technical field of pharmacy, and relates to a method for recovering lipoic acid from lipoic acid crystallization mother liquor. The method comprises the following steps: the method comprises the steps of using a reducing agent sodium borohydride or potassium borohydride to convert lipoic acid, cyclotrisulfur lipoic acid and lipoic acid polymers in lipoic acid crystallization mother liquor into dihydrolipoic acid, and then using a cyclization agent ferric trichloride to oxidatively cyclize the dihydrolipoic acid into the lipoic acid. The quality of the lipoic acid product recovered by the method meets the pharmacopoeia standard, so that the recovery of lipoic acid in lipoic acid crystallization mother liquor is realized, and the conversion of byproducts to main products is also realized.
Description
Technical Field
The invention belongs to the technical field of pharmacy, and relates to a method for recovering lipoic acid from lipoic acid crystallization mother liquor.
Background
Lipoic acid (lipoic acid) with molecular formula of C 8 H 14 O 2 S 2 Is an organic compoundCan be used as coenzyme to participate in acyl transfer in metabolism of substances in organism, and can eliminate free radicals which cause accelerated aging and pathopoiesia. Meanwhile, lipoic acid is absorbed in the intestinal tract in vivo and then enters cells, the lipoic acid has the characteristics of fat solubility and water solubility, and sulfhydryl groups are easy to carry out oxidation-reduction reaction, so that the lipoic acid can protect sulfhydryl enzyme from poisoning by heavy metal ions. Lipoic acid has been widely used in clinical medicine, and the application range includes: the treatment of liver dysfunction, subacute necrosis encephalopathy, nervous diseases, radiation injury, heavy metal poisoning such as arsenic, cadmium and mercury, etc. is known as universal antioxidant.
At present, lipoic acid is mainly synthesized by a chemical method, and a plurality of synthetic process routes related to lipoic acid are provided. Tao Naimin Shuoshi graduation paper "technological study of lipoic acid synthesis" has performed comprehensive carding on the lipoic acid synthesis route. Among them, adipic acid and derivatives are the schemes for industrial production, and typical synthetic routes are as follows:
the quality of the lipoic acid product produced by the scheme accords with the pharmacopoeia standards of various countries. The yield of the process is about 65% in the production process, and even lower, and the reasons for the lower yield mainly include the following two aspects: (1) Because lipoic acid has the characteristics of both fat solubility and water solubility, a large amount of products can be taken away by the water phase after the hydrolysis reaction; (2) The reaction process produces a large amount of byproducts, mainly cyclotrisulfur octoic acid and lipoic acid polymers. The production of these impurities not only reduces the yield but also affects the quality of the product, and the above impurities are also the main impurities recorded in pharmacopoeias of various countries. Aiming at the problem that a large amount of lipoic acid is carried away by the water phase in the post-treatment of the hydrolysis reaction, the article of research progress of lipoic acid production process and wastewater treatment process, which is published by Zhang Tengxiao et al, is carded and summarized, and a large amount of process schemes are summarized. However, there has been no report on the recovery and reuse of the mother liquor after the crystallization and separation of lipoic acid.
Analysis of the above-mentioned lipoic acid crystallization mother liquor components revealed that the contents of the impurity cyclotrishiooctanoic acid and lipoic acid polymers were very high in addition to lipoic acid. This presents a significant challenge for recovery of acceptable lipoic acid from lipoic acid crystallization mother liquor. The solvents contained in the mother liquor are mainly ethyl acetate, acetone, cyclohexane, petroleum ether and other solvents or combinations thereof, and the common schemes in production are as follows: acetone, ethyl acetate, acetone/cyclohexane system, ethyl acetate/cyclohexane system, acetone/petroleum ether system, ethyl acetate/petroleum ether system.
Disclosure of Invention
Accordingly, in view of the above-described lipoic acid crystallization mother liquor, an object of the present invention is to provide a method for recovering lipoic acid from lipoic acid crystallization mother liquor, in which lipoic acid, cyclotrisulfuric acid and lipoic acid polymers in lipoic acid crystallization mother liquor are all converted into dihydrolipoic acid using a reducing agent sodium borohydride or potassium borohydride, and then dihydrolipoic acid is oxidized and cyclized into lipoic acid using an cyclizing agent ferric trichloride, thereby efficiently recovering qualified lipoic acid.
According to the present invention, there is provided a method for recovering lipoic acid from lipoic acid crystallization mother liquor, comprising:
step 1: reduction to dihydrolipoic acid
Concentrating the lipoic acid crystal mother liquor to obtain oily concentrate, and carrying out reduction reaction on the concentrate in water under the condition that the pH value is 7-8 and in the presence of a reducing agent sodium borohydride or potassium borohydride to generate dihydrolipoic acid; after the reaction, acidizing the reaction liquid to pH 1-2 by acid, and extracting the acidized reaction liquid by a first organic solvent to obtain an organic phase containing the dihydrolipoic acid;
step 2: preparation of lipoic acid
And (2) carrying out an oxidative cyclization reaction on the organic phase containing the dihydrolipoic acid obtained in the step (1) in the presence of water, ferric trichloride, sodium hydroxide and oxygen to obtain the lipoic acid.
The method for recovering lipoic acid from lipoic acid crystallization mother liquor according to the present invention is described in more detail as follows.
In the invention, the lipoic acid crystallization mother liquor is crystallization mother liquor obtained after separating lipoic acid crude product in lipoic acid preparation, or crystallization mother liquor generated in the lipoic acid crude product refining process, or a mixed liquor of the lipoic acid crude product and the crystallization mother liquor. The crystallization mother liquor is analyzed by HPLC, as shown in figure 1, the content of the thiooctanoic acid in the crystallization mother liquor is 5-20%, the content of the cyclotrisulfoisooctanoic acid in the crystallization mother liquor is 1-7%, the content of the lipoic acid polymer is 0.1-2% and the solvent is one or more selected from ethyl acetate, acetone, cyclohexane and petroleum ether. For example, as a specific example, the lipoic acid crystallization mother liquor may be the mother liquor of CN109574987a examples 1-4 after separation of lipoic acid.
In the step 1 of preparing the dihydrolipoic acid by reduction, the lipoic acid crystal mother liquor is concentrated to obtain oily concentrate. The concentration is not limited, and for example, reduced pressure distillation concentration may be employed to obtain an oily concentrate.
And then the oily concentrate is subjected to reduction reaction in water under the condition that the pH value is 7-8 and in the presence of a reducing agent sodium borohydride or potassium borohydride to generate the dihydrolipoic acid. The reduction reaction using sodium borohydride or potassium borohydride as a reducing agent is known in the art and can be performed using conventional process conditions. Specifically, water is added to the oily concentrate in an amount of 5 to 30 times, preferably 10 to 20 times, the weight of the oily concentrate, then an inorganic base is added thereto to adjust the pH to 7 to 8 while stirring until the oily concentrate is uniformly dispersed, and then a reducing agent sodium borohydride or potassium borohydride is added thereto to perform a reduction reaction at 30 to 60 ℃, preferably 40 to 50 ℃ for a period of generally 5 to 10 hours. Wherein the inorganic base is selected from sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate and sodium hydroxide, and preferably sodium carbonate; the reducing agent sodium or potassium borohydride is used in an amount of 0.3 to 0.8 times, and preferably 0.5 to 0.7 times, the weight of the oily concentrate.
After the reduction reaction, the reaction solution is acidified to a pH of 1 to 2 with an acid, and the acidified reaction solution is extracted with a first organic solvent to obtain an organic phase containing dihydrolipoic acid. Specifically, hydrochloric acid, phosphoric acid or sulfuric acid solution or the like is used, and hydrochloric acid solution is preferable, and the pH of the reaction solution is adjusted to be controlled between 1 and 2; then, the acidified reaction solution is extracted for one or more times by adopting a first organic solvent, and the extracts are combined to obtain an organic extract phase containing the dihydrolipoic acid. The organic extract phase may be washed with water, if desired. Wherein the first organic solvent is selected from dichloromethane, ethyl acetate and toluene, and preferably dichloromethane; the total amount of the first organic solvent is 1 to 2 times of the water amount by volume.
In the step 2 of preparing lipoic acid, the organic phase containing the dihydrolipoic acid obtained in the step 1 is subjected to an oxidative cyclization reaction in the presence of water, ferric trichloride, sodium hydroxide and oxygen to obtain lipoic acid. Specifically, in the step 2, the water is used in an amount of 0.8 to 1.2 times the volume of the organic phase containing the dihydrolipoic acid; the amount of ferric trichloride is 0.3 to 0.6 times, preferably 0.35 to 0.45 times, the weight of the concentrate in step 1; the dosage of the sodium hydroxide is that the pH value of the reaction solution is adjusted to be 8-9; oxygen is continuously introduced until the reaction is complete. The temperature of the oxidation cyclization reaction is 30-60 ℃, preferably 40-50 ℃; the reaction time is 6-15 hours.
In the method for recovering lipoic acid from lipoic acid crystallization mother liquor, the method further comprises standing and layering at-5-10 ℃, preferably 0-5 ℃ after the oxidation cyclization reaction is completed, and separating to obtain a water phase; adjusting the pH of the water phase to 1-2 by hydrochloric acid, crystallizing and separating lipoic acid, filtering, washing and drying to obtain lipoic acid.
The method for recovering lipoic acid from lipoic acid crystallization mother liquor according to the present invention further comprises purifying lipoic acid obtained as described above. Specifically, the lipoic acid obtained above is added into a second organic solvent, dissolved at 30-40 ℃, preferably at 32-36 ℃, and decolorized by adding activated carbon and silica gel after the solution is cleared, and the activated carbon and the silica gel are removed by filtration after the decolorization is finished; cooling the filtrate to-20-0 deg.c, preferably-10-5 deg.c, crystallizing lipoic acid to separate out, raising the crystal, filtering, washing and drying to obtain lipoic acid. Wherein the second organic solvent is one or a combination of several of acetone, ethyl acetate, cyclohexane, n-heptane and petroleum ether, preferably an acetone/cyclohexane system or an ethyl acetate/cyclohexane system, specifically wherein the volume ratio of acetone to cyclohexane is 1: 4-7 of acetone/cyclohexane system or ethyl acetate and cyclohexane according to the volume ratio of 1:4 to 7 ethyl acetate/cyclohexane system.
Advantageous effects
In the method for recovering the lipoic acid from the lipoic acid crystallization mother liquor, the used reducing agent sodium borohydride or potassium borohydride can completely convert lipoic acid, cyclotrislipoic acid and lipoic acid polymers in the lipoic acid crystallization mother liquor into the dihydrolipoic acid, and the process is simple and convenient, thereby laying a foundation for recovering and obtaining the qualified lipoic acid. And then the ferric trichloride serving as a cyclization agent is used for oxidatively cyclizing the dihydrolipoic acid into lipoic acid, so that the qualified lipoic acid is effectively recovered.
The quality of the lipoic acid product recovered by the method meets the pharmacopoeia standard, so that the recovery of lipoic acid in lipoic acid crystallization mother liquor is realized, and the conversion of byproducts to main products is also realized.
Drawings
FIG. 1 is an HPLC analysis chart of lipoic acid crystallization mother liquor;
figure 2 is a typical HPLC profile of the finished lipoic acid recovered in example 1.
Detailed Description
The method for recovering lipoic acid from lipoic acid crystallization mother liquor according to the present invention will be described more specifically by examples, but the scope of the present invention is not limited to these examples.
Example 1
1kg of lipoic acid crystallization mother liquor was taken, and fig. 1 is an HPLC analysis chart of the lipoic acid crystallization mother liquor, wherein the content of lipoic acid (rt=20.8 min) was 10wt%, the content of cyclotrisulfur octanoic acid (rt=6.4 min) was 3wt%, and the content of lipoic acid polymer (rt=2.3 min) was 0.2wt%, and the lipoic acid crystallization mother liquor was concentrated under reduced pressure to obtain about 160g of oily concentrate. To the concentrate was added 2.5L of water, 41g of sodium carbonate was added in portions to adjust the pH of the solution to 7.9, and stirred until the oil was completely dissolved. 83g of sodium borohydride was added thereto, and the temperature was raised to 50℃for 7 hours. After the reaction, slowly adding 3N hydrochloric acid until the pH of the feed liquid is 1.1, adding 1.5L of dichloromethane, fully stirring, standing for layering, adding 1L of dichloromethane again into the water phase, fully stirring, and standing for layering. The dichloromethane phases of the two extractions are collected and combined, 1L of water is added, and after the mixture is fully stirred, the mixture is stood for layering, so that 2.8L of dichloromethane solution containing the dihydrolipoic acid is obtained.
2.5L of water and 65g of ferric trichloride are added into the dichloromethane containing the dihydrolipoic acid, and after uniform stirring, 32% sodium hydroxide is added, and the pH value of the feed liquid water phase is adjusted to 9. Then heating to 50 ℃, and continuously introducing oxygen to react for 8 hours. Cooling to 10 ℃ after the reaction is finished, and then standing for layering to remove a dichloromethane phase. Concentrated hydrochloric acid was added dropwise to the aqueous phase to a pH of 1.2, during which time a solid precipitated. And (3) after crystallization, carrying out solid-liquid separation, and washing with water to obtain a lipoic acid crude product.
The crude lipoic acid is added into a mixed solvent of 100mL of acetone and 700mL of cyclohexane, the temperature is raised to 40 ℃, and the mixture is stirred until the materials are completely dissolved. After the solution is cleared, adding 5g of active carbon and 15g of silica gel for decoloring, and filtering to remove the active carbon and the silica gel after decoloring. The filtrate was slowly cooled to-15 ℃ and solids precipitated during this time. Keeping the crystal growing temperature at-15 ℃ for 2 hours, carrying out solid-liquid separation after crystal growing, and drying to obtain 103g of lipoic acid, wherein the yield is 64.3% (calculated by concentrating oily matters), and the purity is 99.4% (see figure 2).
Example 2
5kg of the lipoic acid crystallization mother liquor was concentrated under reduced pressure to obtain 720g of an oily concentrate. To the concentrate was added 11L of water, 247g of sodium carbonate was added in portions to adjust the pH of the solution to 7.3, and the mixture was stirred until the oil was completely dissolved. 480g of sodium borohydride was added thereto, and the temperature was raised to 42℃for 9 hours. After the reaction, 2N hydrochloric acid is slowly added until the pH of the feed liquid is 1.6. Adding 6L of dichloromethane, fully stirring, standing for layering, adding 6L of dichloromethane into the water phase again, fully stirring, and standing for layering. The dichloromethane phases of the two extractions are collected and combined, 5L of water is added, and the mixture is fully stirred and then is stood for layering, so as to obtain 12.9L of dichloromethane solution containing the dihydrolipoic acid.
13L of water and 320g of ferric trichloride are added into the dichloromethane containing the dihydrolipoic acid, solid sodium hydroxide is added after uniform stirring, and the pH of a feed liquid water phase is adjusted to 8.2. Heating to 45 ℃, and continuously introducing oxygen to react for 12 hours. Cooling to 0 ℃ after the reaction is finished, and then standing for layering to remove a dichloromethane phase. Concentrated hydrochloric acid was added dropwise to the aqueous phase to a pH of 1.8, during which time a solid precipitated. And (3) after crystallization, carrying out solid-liquid separation, and washing with water to obtain a lipoic acid crude product.
The crude lipoic acid is added into a mixed solvent of 0.6L of ethyl acetate and 3L of cyclohexane, the temperature is raised to 30 ℃, and the mixture is stirred until the materials are completely dissolved. After the solution is cleared, 20g of active carbon and 70g of silica gel are added for decolorization, and the active carbon and the silica gel are removed by filtration after the decolorization is finished. The filtrate was slowly cooled to-5 ℃ and solids precipitated during this time. Keeping the crystal growing temperature at minus 5 ℃ for 2 hours, carrying out solid-liquid separation after the crystal growing, and drying to obtain 520g of lipoic acid, wherein the yield is 72.2% (calculated by concentrating oily matters) and the purity is 99.1%.
Claims (10)
1. A method for recovering lipoic acid from lipoic acid crystallization mother liquor, comprising:
step 1: reduction to dihydrolipoic acid
Concentrating the lipoic acid crystal mother liquor to obtain oily concentrate, and carrying out reduction reaction on the concentrate in water under the condition that the pH value is 7-8 and in the presence of a reducing agent sodium borohydride or potassium borohydride to generate dihydrolipoic acid; after the reaction, acidizing the reaction liquid to pH 1-2 by acid, and extracting the acidized reaction liquid by a first organic solvent to obtain an organic phase containing the dihydrolipoic acid;
step 2: preparation of lipoic acid
And (2) carrying out an oxidative cyclization reaction on the organic phase containing the dihydrolipoic acid obtained in the step (1) in the presence of water, ferric trichloride, sodium hydroxide and oxygen to obtain the lipoic acid.
2. The method for recovering lipoic acid from lipoic acid crystallization mother liquor according to claim 1, wherein the lipoic acid content is 5% to 20%, the cyclotrisulfooctanoic acid content is 1% to 7%, the lipoic acid polymer content is 0.1% to 2% based on the total weight of the lipoic acid crystallization mother liquor, and the solvent is one or more selected from the group consisting of ethyl acetate, acetone, cyclohexane and petroleum ether.
3. The method for recovering lipoic acid from lipoic acid crystallization mother liquor according to claim 1 or 2, characterized in that in the reduction preparation of dihydrolipoic acid in the step 1, the lipoic acid crystallization mother liquor is concentrated by reduced pressure distillation to obtain oily concentrate; adding water into the oily concentrate, wherein the water dosage is 5-30 times of the weight of the oily concentrate, adding inorganic alkali into the oily concentrate to adjust the pH value to 7-8, stirring until the oily concentrate is uniformly dispersed and dissolved, adding a reducing agent sodium borohydride or potassium borohydride, and carrying out reduction reaction at 30-60 ℃ for 5-10 hours, wherein the inorganic alkali is selected from sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate and sodium hydroxide; the usage amount of the reducing agent sodium borohydride or potassium borohydride is 0.3-0.8 times of the weight of the oily concentrate.
4. The method for recovering lipoic acid from lipoic acid crystallization mother liquor according to claim 1 or 2, characterized in that in the step 1 reduction preparation of dihydrolipoic acid, hydrochloric acid, phosphoric acid or sulfuric acid solution is used after the reduction reaction to adjust the pH of the reaction solution to be controlled between 1 and 2; then, extracting the acidified reaction solution for one or more times by adopting a first organic solvent, and combining the extracts to obtain an organic extract phase containing dihydrolipoic acid, wherein the first organic solvent is selected from dichloromethane, ethyl acetate and toluene, and the total dosage of the first organic solvent is 1-2 times of the dosage of water by volume.
5. The method for recovering lipoic acid from lipoic acid crystallization mother liquor according to claim 1 or 2, characterized in that in the step 2 of preparing lipoic acid, the amount of water is 0.8 to 1.2 times the volume of the organic phase containing dihydrolipoic acid; the dosage of the ferric trichloride is 0.3 to 0.6 times of the weight of the concentrate in the step 1; the dosage of the sodium hydroxide is that the pH value of the reaction solution is adjusted to be 8-9; continuously introducing oxygen until the reaction is complete; the temperature of the oxidation cyclization reaction is 30-60 ℃; the reaction time is 6-15 hours.
6. The method for recovering lipoic acid from lipoic acid crystallization mother liquor according to claim 1 or 2, characterized in that the method further comprises standing and layering at-5 ℃ to 10 ℃ after the completion of the oxidation cyclization reaction, and separating to obtain an aqueous phase; adjusting the pH of the water phase to 1-2 by hydrochloric acid, crystallizing and separating lipoic acid, filtering, washing and drying to obtain lipoic acid.
7. The method for recovering lipoic acid from lipoic acid crystallization mother liquor according to claim 6, further comprising the step of purifying said obtained lipoic acid, wherein the steps are as follows: adding the obtained lipoic acid into a second organic solvent, dissolving at 30-40 ℃, adding active carbon and silica gel for decoloring after dissolving, and filtering to remove the active carbon and the silica gel after decoloring; cooling the filtrate to-20-0 ℃, crystallizing and separating out lipoic acid, growing crystals, filtering, washing and drying to obtain lipoic acid, wherein the second organic solvent is one or a combination of more of acetone, ethyl acetate, cyclohexane, n-heptane and petroleum ether.
8. The method for recovering lipoic acid from lipoic acid crystallization mother liquor according to claim 7, wherein the second organic solvent is acetone and cyclohexane in a volume ratio of 1: 4-7 of acetone/cyclohexane system or ethyl acetate and cyclohexane according to the volume ratio of 1:4 to 7 ethyl acetate/cyclohexane system.
9. The method for recovering lipoic acid from lipoic acid crystallization mother liquor according to claim 1 or 2, characterized in that in the reduction preparation of dihydrolipoic acid in the step 1, the lipoic acid crystallization mother liquor is concentrated by reduced pressure distillation to obtain oily concentrate; adding water into the oily concentrate, wherein the water dosage is 5-30 times of the weight of the oily concentrate, adding inorganic alkali into the oily concentrate to adjust the pH value to 7-8, stirring until the oily concentrate is uniformly dispersed and dissolved, adding a reducing agent sodium borohydride or potassium borohydride, and carrying out reduction reaction at 30-60 ℃ for 5-10 hours, wherein the inorganic alkali is selected from sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate and sodium hydroxide; the dosage of the reducing agent sodium borohydride or potassium borohydride is 0.3 to 0.8 time of the weight of the oily concentrate;
in the step 1 of preparing the dihydrolipoic acid by reduction, after the reduction reaction, hydrochloric acid, phosphoric acid or sulfuric acid solution is used for adjusting the pH value of the reaction solution to be controlled between 1 and 2; then, extracting the acidified reaction solution for one or more times by adopting a first organic solvent, and combining the extracts to obtain an organic extract phase containing dihydrolipoic acid, wherein the first organic solvent is selected from dichloromethane, ethyl acetate and toluene, and the total dosage of the first organic solvent is 1-2 times of the dosage of water by volume;
in the preparation of the lipoic acid in the step 2, the water is used in an amount which is 0.8 to 1.2 times the volume of the organic phase containing the dihydrolipoic acid; the dosage of the ferric trichloride is 0.3 to 0.6 times of the weight of the concentrate in the step 1; the dosage of the sodium hydroxide is that the pH value of the reaction solution is adjusted to be 8-9; continuously introducing oxygen until the reaction is complete; the temperature of the oxidation cyclization reaction is 30-60 ℃; the reaction time is 6-15 hours.
10. The method for recovering lipoic acid from lipoic acid crystallization mother liquor according to claim 9, further comprising:
after the oxidation cyclization reaction is completed, standing and layering are carried out at the temperature of-5 ℃ to 10 ℃ to obtain a water phase by separation; adjusting the pH of the water phase to 1-2 by hydrochloric acid, crystallizing and separating lipoic acid, filtering, washing and drying to obtain lipoic acid;
the lipoic acid obtained above was purified as follows: adding the obtained lipoic acid into a second organic solvent, dissolving at 30-40 ℃, adding active carbon and silica gel for decoloring after dissolving, and filtering to remove the active carbon and the silica gel after decoloring; cooling the filtrate to-20-0 ℃, crystallizing and separating out lipoic acid, growing crystals, filtering, washing and drying to obtain lipoic acid, wherein the second organic solvent is one or a combination of more of acetone, ethyl acetate, cyclohexane, n-heptane and petroleum ether.
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