JPS5951293A - Purification of l-ascorbic acid-2-phosphoric acid ester - Google Patents

Abstract

PURPOSE:To obtain the titled compound useful in the fields of pharmaceuticals, foods, etc. in high yield and purity, by contacting a strongly acidic aqueous solution containing L-ascorbic acid-2-phosphoric acid ester with active carbon, and eluting the adsorbed compound with an aqueous solvent. CONSTITUTION:A strongly acidic aqueous solution (preferably acidified to <=1pH with HCl) containing L-ascorbic acid-2-phosphoric acid ester obtained e.g. by the phosphatizing reaction of L-ascorbic acid, is made to contact with active carbon packed in a column (granular active carbon wherein >=90% of the carbon has particle size of 8-250 mesh) preferably at 5-20 deg.C at a hourly flow rate of about 1pt.vol. of the solution per 1pt.vol. of the packed active carbon. The adsorbed L-ascorbic acid-2-phosphoric acid ester is eluted with an aqueous solvent such as an aqueous solution of methanol preferably at 7-9pH to obtain the purified titled compound.

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 order to eliminate these drawbacks, phosphoric esters are known to be stable against heat, light, oxidizing agents, etc., and various methods for producing phosphoric esters have been proposed.

L-ascorbic acid-2-phosphate ester 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, Contains various phosphoric oxides.

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 cannot provide satisfactory results. .

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 by purification using activated carbon. As a result of 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 to adsorb L-ascorbic acid-2-phosphate, and then eluted with an aqueous solvent. L-, which is characterized by
This is a method for purifying ascorbic acid-2-phosphate.

Examples of the liquid containing L-ascorbic acid-2-phosphate used in the present invention include a reaction liquid containing 2-phosphate obtained by subjecting L-ascorbic acid to a phosphoric acid reaction. .

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 [Japanese Patent Publication No. 52-18191, Chemical &amp;
Pharmaceutical buretin (Chemical)
al&Pharmaceutical Bulleti
n) Volume 19, No. 7, pp. 1433-1437 (1
971), Volume 30, No. 3. No. 1024-10
29 (1982)], 5,6-O-isopropylidene-L-ascorbic acid, general formula POX_3 (X:
A reaction solution obtained by mixing a tertiary amine (halogen) and a tertiary amine in a specific solvent and reacting the mixture while maintaining the pH value of at least about 8 (Japanese Patent Application Laid-open No. 52-13616
(see Publication No. 0).

As the liquid containing L-ascorbic acid-2-phosphate used in the method of the present invention, 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.

The method for removing the base or tertiary amine is as follows:
For example, the reaction solution is adjusted to a pH of about 11 or higher with an aqueous inorganic alkali (eg, sodium hydroxide, potassium hydroxide, etc.) solution, and then distilled off under reduced pressure.

To make the aqueous solution containing L-ascorbic acid-2-phosphate obtained in this way strongly acidic, for example, a strongly acidic mineral acid (e.g., hydrochloric acid, sulfuric acid, nitric acid, etc.) is used. From this point of view, it is preferable to use hydrochloric acid. The strong acidity of the aqueous solution 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 μm or less is 1 cc/g or more, and the total pore volume of pores with a diameter of 300 Å or less is 0.6 cc/g or more. , activated carbon having pore characteristics of pores having a diameter of 300 Å or less 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 The total pore volume of pores with a diameter of 300 Å or less is measured, for example, by a method such as a nitrogen gas adsorption method (method described in the above-mentioned literature). In addition, the average pore diameter of pores with a diameter of 300 Å or less is calculated by assuming that the pores with a diameter of 300 Å or less are cylindrical, and using the pore volume and nitrogen gas adsorption isotherm with the BET formula (method described in the above literature). ) is the value calculated from the following formula.

(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 can be produced by soaking wood materials such as wood chips, sawdust, and fruit shells in chemicals such as zinc chloride, phosphoric acid, and calcium chloride at approximately 600 to 700°C. After firing, it is obtained by removing the 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, for example,
It is preferable that 90% or more of the total particle size is 250 mesh. Note that the above-mentioned 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 Company Limited), Calgon (Calgon),
Cooperation, USA).

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 volume of activated carbon filled per hour. The temperature is approximately 5-20°C.

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.), or mixtures thereof.

The pH of the aqueous solution of the basic substance or inorganic salt is about 7 to
It is preferable to set it to 9. To achieve this pH range,
For example, in the case of sodium chloride, the required amount of aqueous sodium hydroxide solution is adjusted with hydrochloric acid, and in the case of ammonium phosphate or ammonium chloride, the required amount of 25% ammonia water is adjusted with phosphoric acid or hydrochloric acid. 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 may be subjected to various appropriate treatments before collecting the target product. For example, if the elution solvent is other than an aqueous solution of a water-soluble organic solvent, a strongly acidic ion exchange resin [
For example, it is preferable to desalinate by passing it through Diaion SK-110 (manufactured by Mitsubishi Kasei Corporation).

Next, it is preferable to use a salt as the target object. Examples of salts include magnesium salts, calcium salts, sodium salts,
Examples include 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 is carried out, for example, by applying the product to a column filled with activated carbon and adsorbing and removing the coloring component to the activated carbon. As the activated carbon,
Examples include those similar to those described above.

The liquid applied to the activated carbon column for decolorization is preferably neutral to weakly alkaline, specifically pH approximately 6 to 10.
, more preferably a pH of about 6 to 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 the usual concentration and crystallization steps. 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,
It has a high purity of 99% or more 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 isopropylidene ascorbic acid (hereinafter abbreviated as "IPA")
30 g was mixed and dissolved, and after cooling to 0 to 10°C, a 60% aqueous potassium hydroxide solution was added to adjust the pH to about 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.

Fill a column with 200 g of activated carbon (Specially made Shirasagi for chromatography) and fill it with water, and then add the above liquid whose pH was adjusted to about 0.5 using S.
It was flowed at V≒1, and about 1 liter of 4% hydrochloric acid was also flowed. Next, 53 g of phosphoric acid, 70 g of 25% aqueous ammonia and 19 g of water
About 0.9 liters of the L-ascorbic acid-2-phosphate ester was eluted by running 2 liters of the 00 g mixture (pH about 8). Transfer the eluate to 300 ml of strongly acidic ion exchange resin (
Ammonia removal was carried out through Diaion SK-110), the effluent was collected, and 26.4% of magnesium oxide was added to the liquid.
g was added to convert L-ascorbic acid-2-phosphate into a magnesium salt, and at the same time, unnecessary phosphoric acid was precipitated as magnesium phosphate. After filtering and removing the precipitate,
The effluent obtained by passing the liquid containing the above L-ascorbic acid-2-phosphate ester through a column packed with 20 g of activated carbon (special Shirasagi for chromatography) at SV≒10 and the effluent obtained by passing 200 ml of water further. The liquid was collected. Next, these effluents were combined and concentrated under reduced pressure to about 250 ml, and 1.5 g of powdered activated carbon (Shirasagi A, manufactured by Takeda Pharmaceutical Co., Ltd.) was added to the concentrated liquid, stirred for 10 minutes, and then filtered.
When 510 ml of 90% methanol was added dropwise to the filtrate, crystals were precipitated. The precipitated crystals were collected by filtration 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%.
Met. The content of this product as determined by area ratio by high performance liquid chromatography was 99.3% in terms of dry matter.

Elemental analysis value (%): C_1_2H_1_2O_1_8P_2Mg_3・12
Theoretical value as H_2O C 18.12 H 4.56
P 7.79Mg 9.17 Measured value C 18.00 H 4.63 P 7.33
Mg 9.04 The above properties, infrared absorption spectrum (IR) and ultraviolet absorption spectrum (UV) are the same as the values described in Chemical and Pharmaceutical Buretin Vol. 17, p. 381 (1969). (The ascorbic acid 3-phosphate ester described in this document is the same as that of Chemical and Pharmaceutical Buretin Vol. 19, No. 7, p. 1433 (1971) and Vol. 30 of the same, No. 33, page 1024 (1982)
It is ascorbic acid-2-phosphate ester. )
.

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

Example 3 In the method of Example 1, IPA was phosphorylated using phosphorus oxychloride instead of TCPP.
, to obtain 34.0 g of L-ascorbic acid-2-phosphate magnesium salt. 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%.

A phosphorylation reaction was carried out in the same manner as in Example 4 and Example 1.
Activated carbon (Specially made Shirasagi for chromatography) 200
ml was adsorbed with L-ascorbic acid-2-phosphate. The activated carbon was washed by passing about 1 liter of a 4% aqueous solution of hydrochloric acid, and then 2 liters of a 20% aqueous solution of isopropyl alcohol was poured into the S
V≒1, and a portion containing L-ascorbic acid-2-phosphate was collected. Then, it was treated in the same manner as in Example 1 to obtain crystals of L-ascorbic acid-2-phosphate magnesium salt. 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 literature.

After phosphorylation and adsorption onto a charcoal-powder chromatography column in the same manner as in Example 5 and Example 1, 50 g of ammonium chloride was added to 1,900 g of water using an approximately 4% aqueous hydrochloric acid solution.
ml and adjusted to pH 10 with 25% ammonia. Approximately 1.5 liters of the fraction containing L-ascorbic acid-2-phosphate was collected from the effluent, and the following procedures were carried out in the same manner as in Example 1, including deammonization, magnesium oxide neutralization, and
Perform methanol crystallization to obtain L-ascorbic acid.
A 2-phosphate ester magnesium salt was obtained. 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] A strongly acidic aqueous solution containing L-ascorbic acid-2-phosphate is brought into contact with activated carbon packed in a column to produce L-
A method for purifying L-ascorbic acid-2-phosphate, which comprises adsorbing ascorbic acid-2-phosphate and then eluting it with an aqueous solvent.