JPH0827101A - Crystallization of l-cystine and new crystals - Google Patents

Abstract

PURPOSE:To stably obtain columnar crystals of L-cystine without particularly severe control of crystallization conditions by effecting the neutralization crystallization of L-cystine in the presence of a trace amount of a transition metal and metaphosphoric acid. CONSTITUTION:In the presence of a trace amount of a transition metal and a metaphosphoric acid, particularly hexametaphosphoric acid, Lcystine is subjected to neutralization crystallization. Thus, columnar crystals can be readily obtained, even in the cases that the concentration of L-cystine is high, or the crystallization temperature is low, or hydrochloric acid is used for neutralization. Further, the cystine solution is concentrated in the presence of a transition metal ion and metaphosphoric acid to give the columnar crystals. When a metaphosphoric acid is added in the absence of a transition metal ion, a new crystal of L-cystine is obtained, giving a diffraction pattern having peaks at the diffraction angles (2theta) of about 15.0 deg., 16.8 deg., 21.5 deg., 23.7 deg., 24.2 deg. and 28.8 deg. by X-ray diffraction powder method using Cu-Kalpha beam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for crystallizing L-cystine which is useful as a raw material for pharmaceuticals, and particularly to L-cystine.
-Provides a method for obtaining columnar crystals of cystine.

[0002]

2. Description of the Related Art Generally, crystallization of L-cystine is mainly carried out by neutralization crystallization because the solubility of L-cystine at its isoelectric point is extremely low. However, the crystals of L-cystine that are usually precipitated by this method are plate-like, and the crystals have a slow separation speed during solid-liquid separation by filtration and the amount of adhered mother liquor remaining in the crystals is large. was there. If the separation speed is slow, the time required for the separation is long and a large amount of equipment is required. Further, if the attached mother liquor is large, the purity of the crystals is deteriorated and the amount of water for washing the crystals is large. Furthermore, since the water content in the crystals is large, the amount of heat required for drying the crystals is large, and the crystals are likely to solidify during drying. The disadvantage of the crystal form being plate-like was not only due to the large amount of the adhering mother liquor as described above, but also because the obtained dried product was easily scattered and its specific volume was large.

As crystals of L-cystine, columnar crystals are known in addition to the above plate crystals. (JP-A-58-596
4) The columnar crystals of L-cystine are about 16.2 ° and about 30.0 ° when measured by powder X-ray diffractometry using Cu-Kα ray as seen in JP-A-58-59964. Is a crystal characterized in that a diffraction pattern having a peak at a diffraction angle (2θ) is obtained. According to JP-A-58-59964, the water content of wet crystals of plate-like crystals is 15 to 30%. On the other hand, the columnar crystal is 2 to 6%, and the dense specific volume of the product is 1.5 to 3.5 ml / g of the plate crystal, but 1.
It has dropped to about 3 to 1.8 ml / g. The water content of the separated crystals varies depending on the separation method, and when separated by a centrifugal filter with a low centrifugal force such as a lab, the water content of plate crystals is usually 15% or more and that of columnar crystals is less than 15%. is there.

Although the columnar crystal is a crystal type of which its superiority is known, it is difficult to crystallize it in practice and it is difficult to practically use it. This is because, as described in JP-A-58-59964, the range of conditions for obtaining this crystal is limited, and it is difficult to obtain columnar crystals stably even in that range. is there.
According to JP-A-58-59964, sulfuric acid is better than hydrochloric acid as the type of neutralizing acid, and the concentration of L-cystine is preferably lower. For example, it is easy to obtain columnar crystals from a solution of 10 g / dl. Not. The crystallization temperature is 50
At 80 ° C or 80 ° C, columnar crystals are likely to precipitate, but 20
It is said that columnar crystals are difficult to obtain at ℃. On the other hand, JP-A-58
-59964 says that it is extremely effective to seed the columnar crystals in advance during crystallization. However, in such an unstable system, even if a seed crystal is added, it is not easy to continuously obtain a columnar crystal, and a small amount of plate crystal is mixed into the seed crystal. Making columnar crystals impossible is easily predictable. In fact, in the example of JP-A-58-59964, crystallization is performed at a high concentration and at a high temperature even in the system in which the seed crystal is added.

[0005]

A method for stably obtaining columnar crystals of L-cystine is developed.

[0006]

[Means for Solving the Problems]

The present inventors have conducted various studies to solve the above problems in crystallization of L-cystine, and found that L-cystine was neutralized in the presence of transition metal ions and metaphosphoric acid. It was found that columnar crystals free from the above problems can be easily obtained by analysis.

The inventor of the present invention intends to solve the above problems.
As a result of various studies on a method of easily obtaining columnar crystals having many advantages in the isolation and purification step of L-cystine, when L-cystine was crystallized in the presence of a trace amount of transition metal and metaphosphoric acid, particularly hexametaphosphoric acid, columnar crystals were formed. I found it easy to get.

That is, when L-cystine is neutralized and crystallized in the coexistence of a transition metal ion and metaphosphoric acid, the concentration of L-cystine is high, the crystallization temperature is low, and the neutralization is performed. Columnar crystals were easily obtained even when hydrochloric acid was used as the acid. Moreover, the seed of the columnar crystal was not required at all. Further, columnar crystals were obtained by concentrating crystallization of L-cystine in the coexistence of transition metal ions and metaphosphoric acid.

The fact that columnar crystals were obtained means that crystal powder X
Confirmed by line diffraction. Wet crystal Moisture content is 30 for plate crystals
%, While columnar crystals were less than 15%.

The L-cystine used in the present invention is a crude L-cystine obtained from a hydrochloric acid hydrolyzate of a plant or animal protein or a purified L-cystine, which is produced from a specific substrate by an enzymatic method. The crude L-cystine obtained may be purified L-cystine, or may be derived from any source as long as it can be crystallized.

As the transition metal ion, aluminum ion, zinc ion, manganese ion, ferrous ion or ferric ion can be used, and ferrous ion and ferric ion are particularly preferred. As metaphosphoric acid, pentametaphosphoric acid, hexametaphosphoric acid or heptametaphosphoric acid can be used, and hexametaphosphoric acid is particularly preferred.

In crystallization in the presence of transition metal ions and metaphosphoric acid, the concentration of metaphosphoric acid is effective from 1 to 2 mg / L in the case of hexametaphosphoric acid.
Even 00 mg / L was effective. The transition metal ion needs to be dissolved in the solution as an ion, but the required minimum concentration is related to the concentration of metaphosphoric acid added,
For example, when the concentration of hexametaphosphoric acid is 100 mg / L, 1-9 mg / L is effective. Further, when the concentration of hexametaphosphoric acid is 1000 mg / L, 10 to 10
Effective at 90 mg / L.

The columnar crystals of L-cystine thus obtained are usually separated and washed with water to wash away the added metaphosphoric acid, and a product of good quality is obtained. However, even in this case, it is natural that the lower the concentration of the added metaphosphoric acid, the smaller the amount of washing water.

The above-mentioned two types of L-cystine crystals, plate-shaped and column-shaped, are known as α crystals (plate-shaped) and β crystals (column-shaped) in theory (Shinya Nagashima, Journal of the Crystallographic Society of Japan, 35). , 38
1 (1993)), and its crystal structure has also been analyzed.
Further, the above-mentioned JP-A-58-59964 shows the solubility of both crystals. According to this, the solubility of β-crystal is slightly higher than that of α-crystal, which is generally stable in α-crystal. It means that β crystal can exist only under a special environment. In the above-mentioned Japanese Patent Laid-Open No. 58-59964, this environment is
This can be achieved by limiting the cystine concentration, temperature, and type of acid, but it is difficult to say that it is practical to industrially operate in such a narrow range. The present invention is characterized in that a β crystal can be obtained by an additive without particularly limiting the crystallization conditions, and its industrial utility is great.

The working principle of the present invention requires further scientific study, but is believed to be as follows.
Metaphosphoric acid is generally used as a chelating agent, and is used for boiler detergents, printing plates, shavings and the like. In the present invention, it is considered that the transition metal ion forms a complex with metaphosphoric acid, and this complex has a crystal growth inhibitory effect on the α crystal of L-cystine, and normally causes a metastable β crystal to exist stably. ing.

On the other hand, when crystallizing L-cystine, the present inventors added metaphosphoric acid in the absence of a transition metal to the above-mentioned α crystal by powder X-ray diffraction method using Cu-Kα ray. We found that crystals with a diffraction pattern different from that of β crystals were deposited and grew. The diffraction angle (2θ) of this crystal is
Many are common with α crystals, but characteristically about 15.0 degrees,
It has peaks at 16.8 degrees, 21.5 degrees, 23.7 degrees, 24.2 degrees, and 28.8 degrees. A crystal having such a diffraction angle has not hitherto been known and is a novel crystal. The appearance of this new crystal was needle-like, and was significantly different from the above α crystal and β crystal. Compared with α crystal and β crystal, this crystal has poor separability and has a large amount of water adhering to the crystal, but on the contrary, the space between crystals after drying is large, and the crystal dissolves in water, dilute acid or the like. At times, the solvent entered between the crystals quickly, and had a property of dissolving at a higher rate than other crystals.

L-cystine is usually dissolved in a solvent, subjected to electrolytic reduction and converted to L-cysteine, and then used as a medicinal raw material or, as it is, dissolved in an appropriate solvent to prepare a treatment solution for a palmer. To In any case, most of the uses are not used as crystals, and are used after once dissolved in some solvent. In this case, the solubility of L-cystine in water is second lowest to that of L-tyrosine among protein-constituting amino acids, so that it takes a long time to dissolve, which is a problem. The novel needle-like crystals newly found by the inventor are expected to solve the problem of dissolution rate in this use.

Further, in the presence of metaphosphoric acid, the pH at which crystals start to emerge (neutralization) during neutralization crystallization is high, and the solution state can be maintained up to a higher concentration at the same pH as in the case of normal α crystal. This means that when neutralizing the hydrolyzate of human hair and first removing and depositing tyrosine, it is possible to separate tyrosine at a higher pH, and it is possible to increase the removal rate of tyrosine. It has an advantageous effect on the purification of cystine.

The new crystals are obtained by adding metaphosphoric acid, for example hexametaphosphoric acid alone, the concentration of which is from 1 to 1.
Effective from 0 mg / L. On the other hand, the inventor has found that a crystal having a large grain size can be obtained by adding a limited metal, for example, nickel or cobalt in an equivalent ratio of 1/2 to 1/50 to metaphosphoric acid. These metals need to be dissolved as ions. When crystallized in a system in which only metaphosphoric acid is present, the length on the major axis side is about 0.1 mm or smaller than that depending on the concentration, but in the presence of the above metals, it is larger than 0.1 mm. 1 mm
Some reach.

In general, the additive adheres to the growth surface of the control crystal and inhibits the adsorption of the host molecule to the crystal, which affects the crystal growth. -Many studies have been conducted to change the crystal form (structure, outer shape) by additives for the purpose of rationalizing the drying process, or adjusting the dissolution rate of crystals in applications such as pharmaceuticals. The present invention is also one of them, and skillfully crystal structure,
This is an example in which the outer shape could be changed.

[0022]

EXAMPLES The present invention will be described in detail below with reference to examples. The powder X-ray diffraction of the crystals obtained in the examples is Phil.
The measurement was performed using a PW1700 powder X-ray diffractometer manufactured by ips and using Cu-Kα ray as a radiation source.

Example 1 To 3.5 g of L-cystine, 50 ml of 4% HCl was added, and after dissolution, 9.7 mg of ferric chloride hexahydrate was added and dissolved, and further 5.5 mg of sodium hexametaphosphate was added. Add, dissolve and add 1% of 27% NaOH with stirring at 35 ° C.
Added at 5 ml / hr. After about 32 minutes, the pH is 0.68
At this point, crystals started to appear, so the addition of NaOH was stopped once. After 24 minutes, the addition of NaOH was restarted, and the neutralization was completed when the pH was adjusted to pH 2. The obtained crystals were columnar crystals, and the water content of the wet crystals separated by filtration was 9%. According to powder X-ray diffraction of the crystal, the crystal form was β crystal. The powder X-ray diffraction pattern of this crystal is shown in FIG.

Example 2 To 3.5 g of L-cystine, 50 ml of 4% HCl was added, and after dissolution, 97 mg of ferric chloride hexahydrate was added and dissolved, and further 55 mg of sodium hexametaphosphate was added and dissolved. After that, add 15% of 27% NaOH while stirring at 35 ° C.
It was added at ml / hr. Approximately 20 minutes later, when the pH reached 0.61, crystals started to appear, so the addition of NaOH was stopped once. After 27 minutes, the addition of NaOH was restarted, and the neutralization was completed when the pH was adjusted to pH 2. The obtained crystals were columnar crystals, and the water content of the wet crystals separated by filtration was 12%. According to powder X-ray diffraction of the crystal, the crystal form was mainly β crystal.

Example 3 To 3.5 g of L-cystine, 50 ml of 4% HCl was added, and after dissolution, 4.8 mg of ferric chloride hexahydrate was added and dissolved, and further 5.5 mg of sodium hexametaphosphate was added. Add, dissolve and add 1% of 27% NaOH with stirring at 35 ° C.
Added at 5 ml / hr. After about 20 minutes, the pH is 0.61
At this point, crystals started to appear, so the addition of NaOH was stopped once. After 47 minutes, the addition of NaOH was restarted, and the neutralization was completed when the pH was adjusted to pH 2. The obtained crystals were columnar crystals, and the water content of the wet crystals separated by filtration was 3%. According to powder X-ray diffraction of the crystal, the crystal form was mainly β crystal.

Example 4 3.5 g of L-cystine was previously degassed to 4%
50 ml of HCl was added, and after dissolution, 0.5 g of sodium sulfite was added and dissolved, and after dissolution, 1 part of ferrous chloride / n hydrate was dissolved.
1.7 mg was added and dissolved, 5.5 mg of sodium hexametaphosphate was further added, and 27% NaOH was added at 15 ml / hr while stirring at 35 ° C. after dissolution. About 14
After 1 minute, when the pH reached 0.61, add 1 NaOH.
It stopped for 0 minutes. Then the pH was raised to 0.68. Since crystals started to appear, the addition of NaOH was stopped once.
After 47 minutes, the addition of NaOH was restarted, and the neutralization was completed when the pH was adjusted to pH 2. The obtained crystals were columnar crystals, and the water content of the wet crystals separated by filtration was 10%. According to powder X-ray diffraction of the crystal, the crystal form was mainly β crystal.

Example 5 To 3.5 g of L-cystine, 50 ml of 4% HCl was added, and after dissolution, 8.7 mg of aluminum chloride hexahydrate was added and dissolved, and sodium hexametaphosphate was added to 5.5.
mg was added, and after dissolution, 27% Na was added with stirring at 35 ° C.
OH was added at 15 ml / hr. Approximately 21 minutes later, when the pH reached 0.61, crystals began to appear, so the addition of NaOH was stopped. After 33 minutes, restart the NaOH addition and
The neutralization was completed at the time point of 2. The obtained crystals were mainly columnar crystals, but also contained a very small amount of needle-like crystals. The wet crystal separated by filtration had a water content of 14%. According to powder X-ray diffraction of the crystal, the crystal form was mainly β crystal.

Example 6 To 3.5 g of L-cystine, 50 ml of 4% HCl was added, and after dissolution, 5.5 mg of sodium hexametaphosphate was added.
Was added, and after dissolution, 27% NaOH was added with stirring at 35 ° C.
Was added at 15 ml / hr. After about 20 minutes, the pH was 0.
At 61, NaOH addition was stopped for 6 minutes and then the pH was raised to 0.68. Since crystals started to appear, the addition of NaOH was stopped once. After 74 minutes, the addition of NaOH was restarted, and the neutralization was terminated when the pH was adjusted to pH 2. The obtained crystals were needle crystals, and the water content of the wet crystals separated by filtration was 73%. After drying this crystal, Cu-Kα
X-ray powder diffraction using X-ray was measured. As a result, the diffraction angle (2θ) of this crystal is often the same as that of α crystal, but characteristically about 15.0 degrees, 16.8 degrees, 21.5 degrees,
It had peaks at 23.7 degrees, 24.2 degrees, and 28.8 degrees. The powder X-ray diffraction pattern of this crystal is shown in FIG.

Example 7 To 3.5 g of L-cystine, 50 ml of 4% HCl was added, and after dissolution, 12.8 of divalent nickel chloride hexahydrate.
After adding and dissolving mg, 5.5 mg of sodium hexametaphosphate was further added, and after dissolving, 27% NaOH was added at 15 ml / hr while stirring at 35 ° C. After about 21 minutes, when the pH reached 0.61, the addition of NaOH was stopped for 5 minutes, and then the pH was raised to 0.65 and NaO was added.
Since H was once stopped but no crystallization occurred, the pH was further raised to 0.68. Since crystals started to appear, the addition of NaOH was stopped once. After 76 minutes, restart the NaOH addition,
The neutralization was completed when the pH was adjusted to pH 2. The obtained crystals were needle-shaped crystals with a large particle size, and the water content of the wet crystals separated by filtration was 76%. After drying this crystal, Cu-K
Powder X-ray diffraction using α ray was measured. As a result, it had the same diffraction pattern as the crystal of Example 6.

Comparative Example 1 To 3.5 g of L-cystine was added 50 ml of 4% HCl, and after dissolution, 1% of 27% NaOH was added with stirring at 35 ° C.
Added at 5 ml / hr. After about 19 minutes, the pH is 0.61
At that point, crystals started to appear, so the addition of NaOH was stopped once. After 26 minutes, the addition of NaOH was restarted, and the neutralization was completed when the pH was adjusted to pH 3. The obtained crystals were a mixture of columnar crystals and plate crystals, and the water content of the wet crystals separated by filtration was 36%. According to powder X-ray diffraction of the crystal, the crystal form was a mixture of α crystal and β crystal.

Comparative Example 2 To 3.5 g of L-cystine, 50 ml of 4% HCl was added, and after dissolution, 97 mg of ferric chloride hexahydrate was added and dissolved. Then, 15 ml of 27% NaOH was added with stirring at 35 ° C. /
added at hr. Approximately 19 minutes later, when the pH reached 0.61, crystals started to appear, so the addition of NaOH was stopped once. After 25 minutes, the addition of NaOH was restarted, and the neutralization was completed when the pH was adjusted to 2. The obtained crystals were a mixture of plate-like crystals and columnar crystals, and the water content of the wet crystals separated by filtration was 2
It was 8%. According to powder X-ray diffraction of the crystal, the crystal form is α
It was a mixture of crystals and β crystals.

Comparative Example 3 3.5 g of L-cystine was previously degassed to 4%
50 ml of HCl was added, after dissolution, 0.5 g of sodium sulfite was added, and after dissolution, 27% N was added while stirring at 35 ° C.
aOH was added at 15 ml / hr. After about 13 minutes, pH
When the value reached 0.61, the addition of NaOH was stopped. Since crystals started to appear, the addition of NaOH was stopped once. After 20 minutes, the addition of NaOH was restarted, and the neutralization was completed when the pH was adjusted to pH 2. The obtained crystals were a mixture of plate crystals and needle crystals, and the water content of the wet crystals separated by filtration was 56%. According to powder X-ray diffraction of the crystal, the crystal form was almost α crystal.

[0033]

According to the present invention, columnar crystals can be obtained without particularly restricting crystallization conditions.
Its industrial utility is great. The columnar crystals have many advantages over the plate-like crystals, such as good separation from the crystallization mother liquor and low water content. The novel needle crystal of L-cystine of the present invention is
When dissolved in water or dilute acid, etc., the solvent enters the crystals faster and has a higher dissolution rate than other crystals, which is expected as a solution to the problem of the dissolution rate of L-cystine. To be done.

[Brief description of drawings]

FIG. 1 is a powder X-ray diffraction pattern of columnar crystals of L-cystine obtained in Example 1.

FIG. 2 is a powder X-ray diffraction pattern of needle crystals of L-cystine obtained in Example 6.

Claims (7)

[Claims] 1. A method for producing columnar crystals of L-cystine, which comprises crystallizing L-cystine from an L-cystine solution containing a transition metal ion and metaphosphoric acid. 2. The method according to claim 1, wherein the metaphosphoric acid is hexametaphosphoric acid. 3. The method according to claim 1 or 2, wherein the transition metal ion is a ferrous ion or a ferric ion. 4. When measured by powder X-ray diffractometry using Cu-Kα ray, it is about 15.0 degrees, 16.8 degrees, 21.5 degrees.
A crystal of L-cystine, characterized in that diffraction patterns having peaks at diffraction angles (2θ) of degrees, 23.7 degrees, 24.2, and 28.8 degrees are obtained. 5. The method for producing L-cystine crystals according to claim 4, which comprises crystallization from an L-cystine solution containing metaphosphoric acid. 6. The method according to claim 5, wherein the metaphosphoric acid is hexametaphosphoric acid. 7. The method according to claim 5, wherein L-cystine is crystallized in the presence of cobalt ion or nickel ion.