JPH0261959B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying L-ascorbic acid-2-phosphate.

L-ascorbic acid is widely used in the fields of medicine, food, cosmetics, etc., but it is sensitive to heat and light and is an oxidizable substance. Therefore, in addition to eliminating these drawbacks, if we use a phosphoric acid ester,
It is known to be stable against light, oxidizing agents, etc., and various methods for producing phosphoric acid esters have been proposed.

L-ascorbic acid-2-phosphate ester is
It is obtained by phosphorylating L-ascorbic acid, but the reaction solution contains various impurities, such as decomposition products due to the instability of L-ascorbic acid and various phosphoric oxides. There is.
It is extremely difficult to obtain the desired L-ascorbic acid-2-phosphate ester in high yield and purity from such a reaction solution, and previously reported purification methods have not yielded satisfactory results. I can't.

In view of these circumstances, the present inventors conducted various studies on purification conditions and found that L-ascorbic acid-2-phosphate ester can be purified with high yield and high purity when purified using activated carbon. As a result of this discovery and further research, the present invention was completed.

In the present invention, a strongly acidic aqueous solution containing L-ascorbic acid-2-phosphate is brought into contact with activated carbon packed in a column.
L-ascorbic acid-2 characterized by adsorbing a phosphoric acid ester and then eluting it with an aqueous solvent.
- A method for purifying phosphoric acid esters.

L-ascorbic acid-2- used in the present invention
The liquid containing phosphoric acid ester is 2- obtained by subjecting L-ascorbic acid to a phosphorylation reaction.
A reaction solution containing a phosphoric acid ester can be mentioned.
The phosphorylation reaction may be any phosphorylation reaction. As the reaction solution, for example, L-ascorbic acid with or without protection at the 5- and 6-positions is reacted with a phosphoric acid halide in a specific solvent in the presence of a base at room temperature or below, and the resulting phosphoric acid derivative is Reaction liquid obtained by hydrolysis [Special Publication 1977-
Publication No. 18191, Chemical & Pharmaceutical Biuretin
Pharmaceutical Bulletin) Volume 19, No. 7, No.
pp. 1433-1437 (1971), Volume 30, No. 3, No.
1024-1029 (1982)], 5,6-0-isopropylidene-L-ascorbic acid, general formula
POX ₃ (X: halogen) and a tertiary amine are mixed in a specific solvent, and the mixture is
For example, a reaction solution obtained by maintaining the pH value of

L-ascorbic acid used in the method of the present invention
As the liquid containing 2-phosphoric acid ester, it is preferable to treat the above-mentioned reaction liquid in advance. Examples of such treatments include distilling off the solvent used, removing bases or tertiary amines, and the like.

As a method for distilling off the solvent, for example, in order to suppress decomposition of L-ascorbic acid-2-phosphate, the solvent is distilled off under reduced pressure at as low a temperature as possible.
As a method for removing the base or tertiary amine, for example, the reaction solution is PH-PHENED with an aqueous inorganic alkali (e.g., sodium hydroxide, potassium hydroxide, etc.) solution.
is about 11 or higher and distilled off under reduced pressure.

L-ascorbic acid obtained in this way
To make an aqueous solution containing 2-phosphate ester strongly acidic, for example, use a strongly acidic mineral acid (e.g. hydrochloric acid,
sulfuric acid, nitric acid, etc.), but from the viewpoint of handling, it is preferable to use hydrochloric acid. What is the strong acidity of the above aqueous solution?
It refers to a pH of about 2 or less, more preferably a pH of about 1 or less.

The activated carbon used in the method of the present invention is not particularly limited, but for example, the total pore volume of pores with a diameter of 15 μ or less is 1 c.c./g or more, and the total pore volume of pores with a diameter of 300 Å or less is 0.6 cc/g. Examples include activated carbon having pore characteristics of 20 Å or more and an average pore diameter of 20 Å or more.

Among the above pore characteristics, the total pore volume of pores with a diameter of 15μ or less can be determined by, for example, mercury intrusion method, nitrogen gas adsorption method [Keii Tominaga: Adsorption, pp. 95-113 (1967), Kyoritsu Shuppan], etc. It is measured by the method of diameter 300
The total pore volume of pores of Å or less is measured, for example, by a method such as a nitrogen gas adsorption method (method described in the above-mentioned document). Also, the diameter is 300Å
The average pore diameter of the pores below is calculated by the BET formula (method described in the above literature) from the pore volume and nitrogen gas adsorption isotherm, assuming that the pores with a diameter of 300 Å or less are cylindrical. This value is calculated from the specific surface area by the following formula.

Average pore diameter = 4 x pore volume/specific surface area (Note) The pore volume in this case refers to the total pore volume of pores with a diameter of 300 Å or less.

Activated carbon with specific pore characteristics as described above is produced by soaking wood materials such as wood chips, sawdust, and fruit grains (coconut shell) in chemicals such as zinc chloride, phosphoric acid, and calcium chloride, and heating them at approximately 600 to 700°C. After firing, it is obtained by removing added chemicals and washing with an acid such as hydrochloric acid.

The activated carbon may be in the form of powder or granules, but granules are preferred, and for example, 90% or more of the activated carbon has a particle size of 8 to 250 mesh. Note that the above mesh is based on the standards of Japanese Industrial Standards (JIS).

Specific examples of the activated carbon include Special Shirasagi for chromatography, Granular Shirasagi L, Granular Shirasagi W (all manufactured by Takeda Pharmaceutical Co., Ltd.), Calgon (CALGON, manufactured by Calgon Cooporation, USA), and the like.

The above aqueous solution is brought into contact with an activated carbon column by filling a column with activated carbon, filling the column with water to prepare the column, and passing the aqueous solution through the column. The rate at which the aqueous solution is passed may be according to a commonly used method, but it is preferable to pass the solution at a flow rate of about 0.5 to 2 times, preferably about 1 time, the amount of dissolved activated carbon charged per hour. The temperature is about 5
~20℃.

In this way, L-ascorbic acid-2-phosphate is adsorbed onto activated carbon.

The L-ascorbic acid-2-phosphate ester adsorbed on the activated carbon column is eluted with an aqueous solvent. The aqueous solvent refers to an aqueous solution based on water.

Specific examples of the aqueous solvent include aqueous solutions of water-soluble organic solvents (e.g., methanol, ethanol, acetone, isobutanol, isopropyl alcohol, etc.), basic substances (e.g., sodium hydroxide, potassium hydroxide, ammonia, dimethyl Examples include aqueous solutions of amines, diethylamine, etc.), aqueous solutions of inorganic salts (eg, sodium chloride, ammonium phosphate, ammonium chloride, etc.), and mixtures thereof.

The pH of the aqueous solution of the basic substance or inorganic salt is
Preferably it is about 7-9. To achieve this pH range, for example, in the case of sodium chloride, adjust the required amount of sodium hydroxide aqueous solution with hydrochloric acid, and in the case of ammonium phosphate or ammonium chloride, adjust the required amount of 25% ammonia water with phosphoric acid or hydrochloric acid. do. Further, in the case of the water-soluble organic solvent, an aqueous solution having a concentration of about 5 to 20% can be used as it is.

The elution temperature is preferably about 5 to 30°C. Further, the amount of the aqueous solvent used for elution is generally about 1.5 to 2.5 times the amount (volume) of the activated carbon.

The obtained eluate is processed before collecting the target substance.
Various appropriate treatments may be performed. for example,
If the elution solvent is not an aqueous solution of a water-soluble organic solvent, in order to remove these basic substances and cations, pass it through a strongly acidic ion exchange resin [e.g., Diaion SK-110 (manufactured by Mitsubishi Kasei Corporation)]. Desalting is preferred.

Next, it is preferable to use a salt as the target object. Examples of salts include magnesium salts, calcium salts,
Examples include sodium salts and potassium salts. As a method for forming the salt, for example, in the case of obtaining a magnesium salt, the desalination solution described above may be neutralized with magnesium oxide. Further, calcium chloride or calcium hydroxide may be used to obtain a calcium salt, sodium hydroxide may be used to obtain a sodium salt, and potassium hydroxide may be used to obtain a potassium salt in the same manner as above.

Furthermore, if necessary, it may be subjected to a step for removing colored components. The coloring component removal step includes, for example, applying to a column filled with activated carbon,
This is done by adsorbing and removing colored components on activated carbon. Examples of the activated carbon include those similar to those described above.

The characteristics of the liquid applied to the decolorizing activated carbon column are as follows:
Neutral or slightly alkaline is preferable, specifically
A pH of about 6-10, more preferably a pH of about 6-7. Examples of methods for adjusting the liquid properties include mineral acids (hydrochloric acid, sulfuric acid, nitric acid, etc.) and organic acids (acetic acid, etc.), with hydrochloric acid being particularly preferred.

The temperature when passing the above liquid through the column is
About 10-30°C is preferred. The resulting effluent and the resulting effluent from further passage of water are collected.

The solution containing the target product thus obtained is subjected to a conventional concentration step and crystallization step. For the concentration, a method such as vacuum concentration is employed, for example. The crystallization step is carried out, for example, by adding alcohols (eg, methanol, ethanol) or acetone.

By the purification method of the present invention, the target L-ascorbic acid-2-phosphate ester can be purified with high purity and high yield, and a product with almost no coloration can be obtained.

The product obtained by this purification method does not require recrystallization and has a high purity of over 99% as measured by high performance liquid chromatography. Moreover, according to this purification method, purification is achieved with a high recovery rate.

The present invention will be explained in more detail with reference to Examples below. Note that the percentage of the solution represents the weight/volume percentage unless otherwise specified.

Example 1 242 ml of pure water, 60.6 g of pyridine, and 30 g of isopropylidene ascorbic acid (hereinafter abbreviated as "IPA") were mixed and dissolved, and after cooling to 0 to 10°C, 60% aqueous potassium hydroxide solution was added to adjust the pH to approximately Adjusted to 13. Next, 30 g of tetrachloropyrophosphoric acid (hereinafter abbreviated as "TCPP") and a 60% aqueous potassium hydroxide solution were added dropwise to the mixture to react at 0 to 10°C.
After the dropwise addition was completed, pyridine was distilled off under reduced pressure, and hydrochloric acid was added to adjust the pH to about 0.5.

Filled with 200g of activated carbon (special Shirasagi for chromatography),
The above solution adjusted to a pH of about 0.5 was passed through a column filled with water at a SV≈1, and then 4% hydrochloric acid at a pH of about 1 was passed through the column. Next, 53g of phosphoric acid, 70g of 25% ammonia water
A mixture 2 containing 1,900 g of water and 1900 g of water (PH of about 8) was flowed to elute a portion containing L-ascorbic acid-2-phosphate ester of about 0.9. The eluate was passed through 300 ml of a strongly acidic ion exchange resin (Diaion SK-110) to remove ammonia and the effluent was collected, and 26.4 g of magnesium oxide was added to the solution to convert L-ascorbic acid-2-phosphate to magnesium. In addition to making a salt, unnecessary phosphoric acid was precipitated as magnesium phosphate. After filtering and removing the precipitate, the liquid containing the above L-ascorbic acid-2-phosphate was passed through a column packed with 20 g of activated carbon (special Shirasagi for chromatography) at SV≒10, resulting in an effluent. And the resulting effluent was collected through another 200 ml of water. These effluents are then combined and reduced to approx.
Concentrate under reduced pressure to 25 ml, add 1.5 g of powdered activated carbon (Shirasagi A, Takeda Pharmaceutical Co., Ltd.) to the concentrated liquid,
After stirring for 10 minutes, filter and add 90% methanol to the liquid.
When ml was added dropwise, crystals precipitated. The precipitated crystals were collected and dried to obtain 35.0 g of L-ascorbic acid-2-phosphate magnesium salt crystals. Almost no coloring was observed in this product. The recovery rate from the phosphorylation reaction solution was 86%. The content of this product based on the area ratio measured by high performance liquid chromatography was 99.3% on a dry matter basis.

Elemental analysis value (%): C ₁₂ H ₁₂ O ₁₈ P ₂ Mg ₃・12H ₂ O Theoretical value C18.12 H4.56 P7.79 Mg9.17 Measured value C18.00 H4.63 P7.33 Mg9.04 The above properties, infrared absorption spectrum (IR) and ultraviolet absorption spectrum (UV) were consistent with the values described in Chemical and Pharmaceutical Biuretin Vol. 17, p. 381 (1969). , ascorbic acid-3 described in this literature
- Phosphate esters are listed in Chemical and Pharmaceutical Biuretin Vol. 19, No. 7,
No. 1433 (1971) and Volume 30, No. 3, No.
From page 1024 (1982), ascorbic acid-2-phosphate ester. ).

Example 2 350ml of pure water, 50g of potassium carbonate and 30g of IPA
After mixing and dissolving, then adding 62ml of pyridine,
Phosphorylation was carried out by dropping 45 g of phosphorus oxyoxide while maintaining the temperature at 0±2°C. A 30% caustic soda aqueous solution was added to the reaction solution to adjust the pH to about 11, and pyridine was distilled off under reduced pressure. Furthermore, add hydrochloric acid to make the pH about 0.5,
Acetone was distilled off under reduced pressure, and the residue was treated in the same manner as in Example 1 to obtain 29.5 g of L-ascorbic acid 2-phosphate magnesium salt. Almost no coloring was observed in this product. The recovery rate from the phosphorylation reaction solution was 85%. IR of this product,
The UV data is consistent with the value described in the above literature, and the content according to the area ratio of high performance liquid chromatography is 99.1.
%showed that. In addition, acetone is used as a solvent for crystallization.
Similar results were obtained using 500ml.

Example 3 In the method of Example 1, IPA was phosphorylated using phosphorus oxychloride instead of TCPP, and it was purified in the same manner as in Example 1 to obtain L-ascorbic acid-2-phosphate ester. Magnesium salt 34.0
I got g. Purity 99.0%. Almost no coloring was observed in this product. The IP and UV values of this product matched the values described in the above literature.

The recovery rate from the phosphorylation reaction solution was 84%.

Example 4 A phosphorylation reaction was carried out in the same manner as in Example 1, and L-ascorbic acid-2-phosphate was adsorbed on 200 ml of activated carbon (special Shirasagi for chromatography) in the same manner as in Example 1. The activated carbon was washed through approximately 4% aqueous hydrochloric acid solution 1, and then through 20% isopropyl alcohol aqueous solution 2 at S≈1 to collect a portion containing L-ascorbic acid-2-phosphate. Then, treated in the same manner as in Example 1,
Crystals of L-ascorbic acid-2-phosphate magnesium salt were obtained. Purity 99.3%. The recovery rate from the phosphorylation reaction solution was 85%.

Almost no coloring was observed in this product.
The IR and UV of this crystal matched the values described in the above literature.

Example 5 After phosphorylation and adsorption to a column for carbon powder chromatography in the same manner as in Example 1,
About 4% aqueous hydrochloric acid solution, followed by ammonium chloride
Dissolve 50g in 1900ml of water and adjust the pH with 25% ammonium.
I poured the solution at 10. Approximately 1.5 fractions containing L-ascorbic acid-2-phosphate in the effluent
was collected, and the same operations as in Example 1 were performed, including deammonization, neutralization of magnesium oxide, and methanol crystallization, to obtain L-ascorbic acid-2-phosphate magnesium salt. Purity 99.2%. Almost no coloring was observed in this product. The recovery rate from the phosphorylation reaction solution was 83%. The IR and UV values of this product matched the values described in the above literature.

Claims (1)

[Claims] 1 A strongly acidic aqueous solution containing L-ascorbic acid-2-phosphate is brought into contact with activated carbon packed in a column to adsorb L-ascorbic acid-2-phosphate, and then eluted with an aqueous solvent. A characterized method for purifying L-ascorbic acid-2-phosphate.