Crystal of 5-aminolevulinic acid phosphate and process for producing the same

1. A crystal of 5-aminolevulinic acid phosphate, which shows characteristic peaks at 7.9°±0.2°, 15.8°±0.2°, 18.9°±0.2°, 20.7°±0.2°, 21.1°±0.2°, 21.4°±0.2°, 22.9°±0.2°, 33.1°±0.2°, and 34.8±0.2° as diffraction angles 2θ in powder X-ray diffraction measured with a wavelength of 1.54 Å (Cu Kα),

wherein the crystal has a melting point of 129 to 131° C.

2. A process for producing the crystal according to claim 1 , wherein a salt of 5-aminolevulinic acid, phosphoric acid, and a basic nitrogen-containing compound are dissolved in a first solvent and then a second solvent having a lower solubility for 5-aminolevulinic acid phosphate as compared with the first solvent is added thereto to precipitate the crystal,

wherein the salt of 5-aminolevulinic acid is hydrochloride, hydrobromide, sulfonate, sulfate, or nitrate, and

the amount of the basic nitrogen-containing compound is 0.1 to 5 molar equivalents to that of the salt of 5-aminolevulinic acid.

3. The process according to claim 2 , wherein the basic nitrogen-containing compound is a pyridine represented by the following formula (1):

wherein R 1 represents a hydrogen atom, a hydrocarbon group having 1 to 40 carbon atoms which may have a substituent, or an amino group which may have a substituent,

or an amine represented by the following formula (2):

NH m R 2 3-m   (2)

wherein m represents an integer of 0 to 3 and R 2 represents a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms which may have a substituent.

4. The process according to claim 2 , wherein the second solvent having a lower solubility for 5-aminolevulinic acid phosphate as compared with the first solvent is at least one selected from methanol, ethanol, n-propanol, isopropanol, acetone, γ-butyrolactone, 1,4-dioxane, methoxyethanol, tetraethylene glycol dimethyl ether, and triethylene glycol dimethyl ether.