Patent Description:
Orotic acid is known to have various actions effective for maintaining and promoting health, such as a uric acid level-lowering action, an anti-inflammatory action, a nutritive analeptic action, and a liver function-promoting action. However, it is extremely difficult to dissolve orotic acid in water or alcohol, and thus it is difficult to blend orotic acid in a pharmaceutical drug, a cosmetic, a food, or the like. As a result, attempts have been made to use an orotic acid derivative having improved solubility in water while maintaining the physiological activity of orotic acid.

As a method for activating the carboxy group of orotic acid to synthesize an orotic acid derivative, an acid chloride method, an acid anhydride method, and an active ester method are known. However, since orotic acid has very low solubility in an organic solvent used industrially, problems such as a decrease in the reaction rate caused by carrying out the reaction at a low concentration easily occur. In addition, purification by column chromatography or the like may be required to remove byproducts. As a result, it is difficult to industrially produce an orotic acid derivative.

Patent Document <NUM> discloses a method for producing an orotic acid derivative by an active esterification method. However, in the method described in Patent Document <NUM>, the cost of the reagent itself is high, and column chromatography is performed for purification. Further, dichloromethane (DCM), which is a halogenic solvent, is used as the reaction solvent. Therefore, it is not suitable for industrial implementation.

<CIT> discloses in examples <NUM>, <NUM> and <NUM> a method for producing an orotic acid derivative comprising a condensation step involving an orotic acid halide with DCM as solvent and in the presence of a base. After reaction the solution is filtered and the orotic acid derivative is recovered in the filtrate.

<NPL>, discloses a method for producing an orotic acid derivative comprising a condensation step involving an orotic acid halide and step of separating the orotic acid derivative by filtration.

<CIT> discloses a method for producing an orotic acid derivative comprising a condensation step involving an orotic acid halide in the presence of a base and a filtration step.

As described above, the conventional method for producing an orotic acid derivative is not a suitable method for industrial implementation.

An object of the present invention is to provide an inexpensive and industrially feasible method for producing an orotic acid derivative.

The present invention provides an inexpensive and industrially feasible method for producing an orotic acid derivative.

In the present specification, a structure is disclosed in which an asymmetric carbon is present and enantiomers or diastereomers may be present, depending on the structure of the chemical formula. In that case, these isomers are represented by one chemical formula. These isomers may be used alone or in the form of a mixture.

In the present specification, a structure is disclosed which may have salt forms, depending on the structure of the chemical formula. In that case, one chemical formula includes the salt forms thereof. Further, in a case where solvate forms may be present, one chemical formula includes the solvate forms thereof.

In the present specification, the term "orotic acid derivative" includes a salt form. Examples of the salt form include an inorganic acid salt, and examples of the inorganic acid salt include a hydrochloride, a sulfate, and a nitrate.

The present invention provides a method for producing an orotic acid derivative. The production method of the present embodiment includes a condensation step of performing, under a basic condition, a condensation reaction between an orotic acid halide represented by General Formula (I) and a compound represented by General Formula (II) to generate an orotic acid derivative represented by General Formula (III) wherein the compound represented by General Formula (II) is glutamic acid; and a neutralization crystallization step of precipitating crystals of orotic acid by neutralization crystallization to separate a liquid containing the orotic acid derivative from the crystals of orotic acid. <CHM>
[In the formula, X is a halogen atom, and A is a group represented by General Formula (A-<NUM>)]
<CHM>
[In the formula, -NR<NUM>R<NUM> represents the glutamic acid residue, wherein R<NUM> is a hydrogen atom* is a bonding position at which the hydrogen atom in General Formula (II) is bonded.

The condensation step is a step of performing, under a basic condition, a condensation reaction between an orotic acid halide represented by General Formula (I) and a compound represented by General Formula (II) (hereinafter, may be referred to as a "compound (II)") to generate an orotic acid derivative represented by General Formula (III).

The orotic acid halide used in this step is a compound represented by General Formula (I) (hereinafter, also referred to as a "compound (I)"). In General Formula (I), X represents a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, a chlorine atom is preferable.

The orotic acid halide can be synthesized by a known method. Examples of the method for synthesizing an orotic acid halide include a method for reacting orotic acid with thionyl halide. Specific examples of the method for synthesizing an orotic acid halide will be described in the section "(Orotic acid halogenation step)" described later.

The compound (II) is a compound represented by General Formula (II). In General Formula (II), A is a group represented by General Formula (A-<NUM>). Hereinafter, a compound in which A in General Formula (II) is a group represented by General Formula (A-<NUM>).

Compound (II-<NUM>) can also be represented by General Formula (II-<NUM>), corresponding to A-H or (A-<NUM>)-H. <CHM>
[In the formula, R<NUM> and R<NUM> are the same as those in General Formula (A-<NUM>).

An orotic acid derivative generated in this step is a compound represented by General Formula (III) (hereinafter, also referred to as a "compound (III)"). In General Formula (III), A is a group represented by General Formula (A-<NUM>). Hereinafter, a compound in which A in General Formula (III) is a group represented by General Formula (A-<NUM>) is also described as a "compound (III-<NUM>)". The compound (III-<NUM>) is a compound produced by a condensation reaction between the compound (I) and the compound (II-<NUM>).

The compound (III-<NUM>) can also be represented by General Formula (III-<NUM>). In General Formula (III-<NUM>), R<NUM> and R<NUM> are the same as those in General Formula (A-<NUM>). <CHM>
[In the formula, R<NUM> and R<NUM> are the same as those in General Formula (A-<NUM>).

The condensation reaction between the compound (I) and the compound (II) can be carried out by a known method such as the Schotten-Baumann reaction. The condensation reaction can be carried out, for example, by dissolving the compound (I) and the compound (II) in a suitable solvent, mixing them, and reacting them under a basic condition.

The solvent used in the condensation reaction is not particularly limited; however, from the viewpoint of industrial usability, it is a water-containing solvent. A water-containing solvent refers to a solvent containing water. The water-containing solvent may be a solvent containing water, may be water alone, or may be a two-phase solvent of an organic solvent and water.

The organic solvent used for the two-phase solvent of an organic solvent and water is not particularly limited; however, it is preferably an organic solvent having no functional group (a hydroxy group, an amino group, a mercapto group, or the like) that reacts with an acid halide. Examples of such a solvent include hydrocarbon-based solvents such as toluene, xylene, anisole, hexane, and heptane; and ether-based solvents such as tetrahydrofuran, diethyl ether, and tert-butyl methyl ether.

Among them, from the viewpoint of improving the yield of the compound (III), it is preferable to use a two-phase solvent of an organic solvent and water. The organic solvent is effective in suppressing the decomposition of an acid halide. Since water can easily maintain a specified pH and has a good pH responsiveness, it is easy to secure the solubility of reaction raw materials and target products. For this reason, it is presumed that the two-phase solvent of an organic solvent and water is a system in which the progression of the reaction is promoted and the neutralization (the removal to the outside of system) of the acid generated as a by-product during the reaction easily progresses. As the two-phase solvent of an organic solvent and water, it is more preferable to use a two-phase solvent of toluene and water or a two-phase solvent of tetrahydrofuran and water, and it is still more preferable to use a two-phase solvent of tetrahydrofuran and water. In a case where a two-phase solvent of toluene/water is used, a liquid-liquid separation is easy and operability is excellent.

The mixing ratio of the organic solvent to water in the two-phase solvent of an organic solvent and water is not particularly limited; however, for example, the mixing ratio can be water:organic solvent (mass ratio) = <NUM>:<NUM> to <NUM>:<NUM>. The mixing ratio is preferably water:organic solvent (mass ratio) = <NUM>:<NUM> to <NUM>:<NUM>, more preferably water:organic solvent (mass ratio) = <NUM>:<NUM> to <NUM>:<NUM>, and particularly preferably water:organic solvent (mass ratio) = <NUM>:<NUM>.

As the organic solvent used for the two-phase solvent of an organic solvent and water, only one kind of organic solvent may be used, or two or more kinds thereof may be mixed and used.

In order to make a reaction condition basic, the reaction solution can be made basic by using a base. The base used for making the reaction solution basic is not particularly limited, and an organic base or an inorganic base can be used; however, an inorganic base is preferable. Examples of the organic base include triethylamine and pyridine. Examples of the inorganic base include sodium hydroxide, potassium hydroxide, and calcium hydroxide, and sodium hydroxide is preferable. Further, in order to promote the condensation reaction, a small amount of N,N-dimethyl-<NUM>-aminopyridine may be added to the reaction solution.

The reaction temperature in the condensation reaction is preferably <NUM> or lower. The temperature condition during the condensation reaction can be, for example, <NUM> to <NUM>.

The pH (the pH of the suspension in a case of using a two-phase solvent) in the condensation reaction may be under a basic condition. The pH during the condensation reaction is preferably maintained at, for example, pH <NUM> to <NUM> and is more preferably maintained at pH <NUM> to <NUM>.

The pressure conditions in the condensation reaction are not particularly limited; however, pressure conditions of normal pressure are preferable.

The reaction time of the condensation reaction is not particularly limited, and it can be appropriately set depending on the amounts of the compound (I) and the compound (II); however, for example, can be set to about <NUM> to <NUM> minutes.

During the condensation reaction, it is preferable to stir the reaction solution in order to promote the reaction. The shape of the stirring blade and rotation speed are not particularly limited; however, it is preferable that the crystals present in the reaction solution be homogeneously mixed in the solution.

A glass lining reactor can be used for the condensation reaction. Since a metal container liquates out, the metal container is not suitable as a reaction container for this reaction.

In the reaction solution of the condensation reaction, the concentration of the compound (I) (the orotic acid halide) at the start of the reaction is preferably <NUM>% to <NUM>% by mass and more preferably <NUM>% to <NUM>% by mass. In a case where the concentration of the orotic acid halide is equal to or more than the above lower limit value, the industrial productivity is good, and in a case where the concentration of the orotic acid halide is equal to or less than the above upper limit value, it is possible to prevent a decrease in yield due to the progression of side reactions.

In the reaction solution of the condensation reaction, the concentration ratio (the molar ratio) of the compound (I) (the orotic acid halide) and the compound (II) at the start of the reaction is preferably compound (II)/compound (I) = <NUM> to <NUM> and is more preferably compound (II)/compound (I) = <NUM> to <NUM>. In a case where the concentration ratio is equal to or more than the above lower limit value, the burden of collecting raw materials can be reduced, and in a case where the concentration ratio is equal to or less than the above upper limit value, the burden of purification can be reduced.

The method for adding the orotic acid halide to the reactor is not particularly limited, and the orotic acid halide may be directly added at one time, or the orotic acid halide may be divided and added in small amounts.

The condensation reaction between the compound (I) and compound (II) is shown below. <CHM>
[In the formula, X and A are the same as the above.

The neutralization crystallization step is a step of precipitating crystals of orotic acid by neutralization crystallization to separate a liquid containing the orotic acid derivative from the crystals of orotic acid. This step is performed after the condensation step.

In the condensation step, the orotic acid halide (the compound (I)) that did not react with compound (II) is hydrolyzed to orotic acid. As a result, orotic acid and the orotic acid derivative (the compound (III)) are mixed in the reaction solution after the condensation step. By this step, orotic acid can be selectively precipitated from the above-described mixed solution of orotic acid and the orotic acid derivative.

The reaction solution after the condensation step can be subjected to neutralization crystallization. Alternatively, in a case where a two-phase solvent of an organic solvent and water is used in the condensation step, the aqueous phase obtained by separating the organic solvent and water after the condensation step may be subjected to neutralization crystallization. Alternatively, the reaction solution may be a liquid containing orotic acid and an orotic acid derivative which has undergone any other treatment after the condensation step.

In a case where a two-phase solvent of an organic solvent and water is used in the condensation step, the method for separating the organic solvent and water after the condensation step is not particularly limited. Examples of the method for separating the organic solvent and water include separation by distilling off the organic solvent and the liquid-liquid separation. In a case where the organic solvent and water are homogeneously mixed, the organic solvent and water can be separated by distilling off the organic solvent, and in a case where the organic solvent and water are phase-separated, the organic solvent and water can be separated by liquid-liquid separation. In a case where tetrahydrofuran is used as the organic solvent, separation by distilling off the organic solvent is preferable, and in a case where toluene is used as the organic solvent, the liquid-liquid separation is preferable. In a case where liquid-liquid separation has been carried out, distillation (concentration) may be carried out thereafter in consideration of the solubility of the target product.

Neutralization crystallization may be carried out by a conventional method and can be carried out by gradually adding an acid to the target liquid containing orotic acid and an orotic acid derivative to lower the pH. The acid used for neutralization crystallization is not particularly limited; however, an inorganic acid is preferable. Examples of the inorganic acid include hydrochloric acid, sulfuric acid, and nitric acid, and hydrochloric acid is preferable.

Neutralization crystallization is carried out until the pH of the liquid phase reaches about a pH of <NUM> to <NUM>, preferably carried out until the pH reaches about <NUM> to <NUM>, and more preferably carried out until the pH reaches about <NUM> to <NUM>. In a case where the pH is lower than <NUM>, even the orotic acid derivative may also be precipitated.

The temperature at which neutralization crystallization is performed is not particularly limited; however, it can be, for example, in the range of <NUM> to <NUM>. In a case where the temperature at which neutralization crystallization is performed is equal to or more than the above lower limit value, impurities are less likely to precipitate, and in a case where the temperature is equal to or less than the above upper limit value, the decrease of the recovery rate can be prevented.

By this step, orotic acid can be selectively precipitated from a liquid composition in which orotic acid and an orotic acid derivative are mixed. The precipitated orotic acid crystals can be removed by filtration or the like. In this manner, the precipitated orotic acid crystals and the liquid containing the orotic acid derivative can be separated. For filtration, a commercially available filtration filter or the like can be used. In this manner, the purity of the orotic acid derivative in the filtrate can be improved without performing column chromatography or the like. As a result, a liquid containing an orotic acid derivative with high purity can be obtained.

The production method of the present embodiment may include other steps in addition to the condensation step and the neutralization crystallization step. Examples of the other steps include a secondary neutralization crystallization step of precipitating crystals of an orotic acid derivative by neutralization crystallization, a crystal collection step of collecting crystals of an orotic acid derivative, and an orotic acid halogenation step of synthesizing an orotic acid halide.

The secondary neutralization crystallization step is a step of subjecting the liquid containing the orotic acid derivative obtained in the neutralization crystallization step to neutralization crystallization to precipitate crystals of the orotic acid derivative.

The neutralization crystallization in this step may also be carried out by a conventional method, and an inorganic acid is preferably used. Examples of the inorganic acid include hydrochloric acid, sulfuric acid, and nitric acid, and hydrochloric acid is preferable.

The neutralization crystallization in this step is preferably carried out until the pH of the liquid phase reaches about <NUM> to <NUM>, more preferably carried out until the pH reaches about <NUM> to <NUM>, and still more preferably carried out until the pH reaches about <NUM> to <NUM>.

By this step, the orotic acid derivative can be selectively precipitated from the liquid containing the orotic acid derivative. The obtained orotic acid derivative is obtained as a salt of the acid used for acidifying the liquid. The salt of the orotic acid derivative can be converted to a free orotic acid derivative by neutralizing with an equivalent amount of a basic compound. As the basic compound, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium phosphate salt, potassium phosphate salt, ammonia, or the like can be used.

The crystal collection step is a step of collecting crystals of the orotic acid derivative after the secondary neutralization crystallization step.

The crystals of the orotic acid derivative can be collected, for example, by filtration or the like. For filtration, a commercially available filtration filter or the like can be used.

The orotic acid halogenation step is a step of halogenating orotic acid to obtain an orotic acid halide represented by General Formula (I), which is a raw material for the condensation reaction. The halogenation of orotic acid can be performed by a known method. For example, an orotic acid halide can be obtained by reacting orotic acid with an electrophilic halogenating agent such as thionyl halide (SOX<NUM>; X is a halogen atom). This step is preferably carried out in the presence of a catalytic amount of N,N-dimethylformamide by dissolving orotic acid in a solvent such as toluene. The reaction temperature can be, for example, <NUM> to <NUM>. It is preferable to use a glass lining reactor for the reaction. Since a metal container liquates out, the metal container is not suitable as a reaction container for this reaction.

In the halogenation reaction of orotic acid, the concentration of orotic acid in the reaction solution at the start of the reaction is preferably <NUM>% to <NUM>% by mass and more preferably <NUM>% to <NUM>% by mass. In a case where the concentration of orotic acid is equal to or more than the above lower limit value, the industrial productivity is good, and in a case where the concentration of the orotic acid halide is equal to or less than the above upper limit value, it is possible to prevent a decrease in yield due to the progression of side reactions.

The halogenation reaction of orotic acid may be carried out in air or may be carried out in a nitrogen gas atmosphere. The reaction is preferably carried out in the air.

The reaction for generating an orotic acid halide (<NUM>) from an orotic acid (<NUM>) and a thionyl halide (<NUM>) is shown below. In the following formula, X represents a halogen atom.

In addition to the above steps, the production method of the present embodiment may include, without particular limitation, a step commonly used as a method for purifying a chemical substance, such as a washing step or a drying step under reduced pressure.

According to the production method of the present embodiment, orotic acid and the orotic acid derivative can be separated by a simple method without performing column chromatography or the like. As a result, a highly purified orotic acid derivative can be obtained. Further, the production method of the present embodiment can be carried out using relatively inexpensive reagents.

As a result, the production method of the present embodiment is useful as a method for industrially producing an orotic acid derivative at a low cost.

The present invention will be described with reference to Examples.

Analysis by high-performance liquid chromatography (HPLC) was used to study the synthesis of orotic acid derivatives. The HPLC conditions used in the analysis are shown below.

Orotic acid (<NUM>, Thermo Fisher Scientific, Inc. ), toluene (<NUM>, Junsei Chemical Co. ), and N,N-dimethylformamide (DMF, <NUM>, Junsei Chemical Co. ) were added to a four-necked flask equipped with a Dimroth condenser tube, a Teflon (registered trade mark) stirring blade, a funnel for dropwise addition, and a thermometer, and stirred for several minutes. Then, thionyl chloride (SOCl<NUM>, <NUM>, <NUM> equivalents to the mole number of orotic acid, Tokyo Chemical Industry Co. ) was added thereto over <NUM> minutes using the funnel for dropwise addition. The four-necked flask was immersed in an oil bath and maintained at about <NUM> while stirring. Five hours after the temperature reached about <NUM>, <NUM>µL of the reaction solution in the four-necked flask was sampled. The sampled reaction solution was added to <NUM> of dehydrated methanol, stirred lightly, and then left to stand for about <NUM> minutes. Then, the orotic acid methyl ester in the sampled reaction solution was analyzed by HPLC. The yield of orotic acid chloride based on the orotic acid calculated from the analysis value of the orotic acid methyl ester was <NUM>%.

Next, the reaction solution in the four-necked flask was cooled to room temperature (about <NUM>) and filtered using a Kiriyama funnel (registered trade mark) to obtain crystals precipitated in the reaction solution. The crystals obtained on the filter paper were washed with <NUM> times their weight of toluene and then dried at room temperature at about <NUM> kPa for about <NUM> hour to remove the solvent. The amount of orotic acid chloride obtained was <NUM>.

Ion-exchanged water (<NUM>), sodium glutamate monohydrate (<NUM>, <NUM> equivalents to orotic acid chloride), and a <NUM>% aqueous sodium hydroxide solution (<NUM>, <NUM> equivalents to orotic acid chloride) were added to a <NUM>-mL four-necked flask equipped with a Teflon (registered trade mark) stirring blade and a thermometer. Orotic acid chloride (<NUM>) synthesized by the same method as in Synthesis Example <NUM> and the <NUM>% aqueous sodium hydroxide solution (<NUM>) were each divided into <NUM> aliquots and added alternately to the four-necked flask which had been ice-cooled so that the liquid temperature was maintained at <NUM> or lower. After the addition, the reaction solution was stirred at <NUM> or lower for <NUM> hour. The pH of the reaction solution was <NUM>. A part of this reaction solution was sampled, and N-orotinyl glutamic acid in the sampled reaction solution was analyzed by HPLC. The yield of N-orotinyl glutamic acid based on the orotic acid chloride calculated from the analysis value was <NUM>%.

A solution (<NUM>) obtained by mixing toluene with ion-exchanged water at a mass ratio of <NUM>:<NUM>, sodium glutamate monohydrate (<NUM>, <NUM> equivalents to orotic acid chloride), and a <NUM>% aqueous sodium hydroxide solution (<NUM>, <NUM> equivalents to orotic acid chloride) were added to a <NUM>-mL four-necked flask equipped with a Teflon (registered trade mark) stirring blade, a pH meter, and a thermometer. Orotic acid chloride (<NUM>) synthesized by the same method as in Synthesis Example <NUM> was added little-by-little to the four-necked flask which had been ice-cooled so that the liquid temperature was maintained at <NUM> or lower. During the addition and reaction of orotic acid chloride, the pH of the reaction solution (in the suspended state) was monitored with a pH meter, and a <NUM>% aqueous sodium hydroxide solution was automatically supplied by a supply pump so that the pH was maintained at <NUM>. The amount of the <NUM>% aqueous sodium hydroxide solution supplied to the reaction solution by the completion of the reaction was <NUM>. After the addition of orotic acid chloride, the reaction solution was stirred at <NUM> or lower for <NUM> hour. Then, a part of the reaction solution was sampled, and N-orotinyl glutamic acid in the sampled reaction solution was analyzed by HPLC. The yield of N-orotinyl glutamic acid based on the orotic acid chloride calculated from the analysis value was <NUM>%.

After completion of the reaction, the reaction solution was transferred to a separating funnel and separated into an organic layer containing toluene and an aqueous layer.

A solution (<NUM>) obtained by mixing tetrahydrofuran with ion-exchanged water at a mass ratio of <NUM>:<NUM>, sodium glutamate monohydrate (<NUM>, <NUM> equivalents to orotic acid chloride), and a <NUM>% aqueous sodium hydroxide solution (<NUM>, <NUM> equivalents to orotic acid chloride) were added to a <NUM>-mL four-necked flask equipped with a Teflon (registered trade mark) stirring blade, a pH meter, and a thermometer. Orotic acid chloride (<NUM>) synthesized by the same method as in Synthesis Example <NUM> was added little-by-little to the four-necked flask which had been ice-cooled so that the liquid temperature was maintained at <NUM> or lower. During the addition and reaction of orotic acid chloride, the pH of the reaction solution was monitored with a pH meter, and a <NUM>% aqueous sodium hydroxide solution was automatically supplied by a supply pump so that the pH was maintained at <NUM>. The amount of the <NUM>% aqueous sodium hydroxide solution supplied to the reaction solution by the completion of the reaction was <NUM>. After the addition of orotic acid chloride, the reaction solution was stirred at <NUM> or lower for <NUM> hour. Then, a part of the reaction solution was sampled, and N-orotinyl glutamic acid in the sampled reaction solution was analyzed by HPLC. The yield of N-orotinyl glutamic acid based on the orotic acid chloride calculated from the analysis values was <NUM>%.

<NUM>% hydrochloric acid was added to <NUM> of an aqueous layer containing <NUM> of N-orotinyl glutamic acid synthesized by the same method as in Example <NUM> and containing <NUM> of orotic acid to adjust the pH to <NUM>. Crystals of orotic acid precipitated due to a change in pH were removed by filtration to obtain a filtrate. Crystals of N-orotinyl glutamic acid hydrochloride were precipitated by adding <NUM>% hydrochloric acid to the obtained filtrate to adjust the pH to <NUM>. The crystals in this liquid were obtained by filtration and washed with about <NUM> of cold water.

The recovery rate of orotinyl glutamic acid recovered by this operation was <NUM>%, and the removal rate of orotic acid was <NUM>%. The ratio (the mass ratio) of orotic acid to orotinyl glutamic acid hydrochloride in the obtained crystals was <NUM>%.

<NUM> of an aqueous layer containing <NUM> of N-orotinyl glutamic acid synthesized in the same manner as in Example <NUM> and <NUM> of orotic acid were filtered through a filter to obtain a filtrate. The obtained filtrate was concentrated under reduced pressure until the amount was to be <NUM>, and crystals were precipitated. The crystals in this liquid were obtained by filtration and washed with about <NUM> of cold water.

The orotinyl glutamic acid recovered by this operation was in hydrochloride form. The recovery rate was <NUM>% and the removal rate of orotic acid was <NUM>%. The ratio (the mass ratio) of orotic acid to orotinyl glutamic acid hydrochloride in the obtained crystals was <NUM>%.

N-orotinyl glutamic acid was synthesized by the same method as in Example <NUM>, and crystals of N-orotinyl glutamic acid hydrochloride recovered by the same method as in Example <NUM> were used to prepare an aqueous solution containing <NUM> w/w% of N-orotinyl glutamic acid. Each of ethanol, methanol, isopropanol, acetone, and THF was added to <NUM> of the solution to carry out anti-solvent crystallization. Regardless of which solvent was used for anti-solvent crystallization, the solution became jelly-like, and it was difficult to separate the crystals of orotinyl glutamic acid.

N-Orotinyl glutamic acid was synthesized by the same method as in Example <NUM>, and crystals of N-orotinyl glutamic acid hydrochloride recovered by the same method as in Example <NUM> were used to prepare a slurry solution (dispersion medium: water) containing <NUM> w/w% of orotinyl glutamic acid. <NUM> of the slurry liquid was heated to <NUM> to dissolve crystals of N-orotinyl glutamic acid. The solution was cooled gradually. With cooling, the liquid property became jelly-like, and it was difficult to separate the crystals of orotinyl glutamic acid.

Claim 1:
A method for producing an orotic acid derivative, comprising:
a condensation step of performing, under a basic condition in a water-containing solvent, a condensation reaction between an orotic acid halide represented by General Formula (I) and a compound represented by General Formula (II) to generate an orotic acid derivative represented by General Formula (III), wherein the compound represented by General Formula (II) is glutamic acid; and
a neutralization crystallization step of precipitating crystals of orotic acid by neutralization crystallization to separate an aqueous phase containing the orotic acid derivative from the crystals of orotic acid, after the condensation step, wherein the pH of the aqueous phase is set to <NUM> to <NUM> in the neutralization crystallization step,
<CHM>
wherein X is a halogen atom, and A is a group represented by General Formula (A-<NUM>);
<CHM>
wherein -NR<NUM>R<NUM> represents the glutamic acid residue, wherein R<NUM> is a hydrogen atom and * is a bonding position at which the hydrogen atom in General Formula (II) is bonded.