Crystals of phenylalanine derivatives and production methods thereof

1. A crystal of the compound of formula (I):

which is a γ-type crystal, an ε-type crystal, a η-type crystal or a θ-type crystal,

said γ-type crystal exhibiting peaks at the diffraction angles (2θ) of at least 7.2°, 8.1°, 15.1°, and 23.3°;

said ε-type crystal exhibiting peaks at the diffraction angles (2θ) of at least 8.3°, 11.1°, 12.8°, 16.1° and 24.5°;

said η-type crystal exhibiting peaks at the diffraction angles (2θ) of at least 9.7°, 12.2°, 18.5°, and 20.4°; and

said θ-type crystal exhibiting peaks at diffraction angles (2θ) of at least 5.7°, 11.5°, and 13.9° or of at least 11.5°, 13.9°, 18.5°, 20.0° and 21.0° in the powder X-ray diffraction pattern.

2. A crystal according to claim 1 , which is

a γ-type crystal exhibiting peaks at the diffraction angles (2θ) of at least 7.2°, 8.1°, 10.3°, 10.9°, 14.5°, 15.1°, 15.4°, 17.3°, 18.3°, 19.4° and 23.3°;

an ε-type crystal exhibiting peaks at the diffraction angles (2θ) of at least 5.4°, 6.9°, 8.3°, 10.8°, 11.1°, 12.8°, 16.1°, 17.7°, 21.6°, 23.4°, 24.5° and 25.1°;

a η-type crystal exhibiting peaks at the diffraction angles (2θ) of at least 9.7°, 12.2°, 12.8°, 14.9°, 15.6°, 16.9°, 18.5°, and 20.4°; or

a θ-type crystal exhibiting peaks at diffraction angles (2θ) of at least 5.7°, 10.3°, 11.5°, 13.9°, 16.5°, 18.5°, 20.0° and 21.0° in the powder X-ray diffraction pattern.

3. A crystal according to claim 1 , which is a γ-type crystal.

4. A crystal according to claim 1 , which is a ε-type crystal.

5. A crystal according to claim 1 , which is a η-type crystal.

6. A crystal according to claim 1 , which is a θ-type crystal.

7. A method for producing a crystal according to claim 1 , which comprises crystallizing said crystal by one of crystallization with at least one solvent, crystallization by suspension, crystallization by neutralization, or crystallization by concentration.

8. The method according to claim 7 , wherein said crystal is a γ-type crystal and which method comprises dissolving said crystal in dimethylformamide to form a mixture; and thereafter cooling said mixture to a temperature of from 0 to 30° C.

9. The method according to claim 8 , wherein said cooling is carried out at a temperature of from 4 to 25° C.

10. The method according to claim 7 , wherein said crystal is a γ-type crystal and which method comprises dissolving said crystal in dimethylformamide to form a mixture; and thereafter, adding water to said mixture.

11. The method according to claim 10 , wherein a volume ratio of said dimethylformamide to said water is from 50:1 to 1000:1.

12. The method according to claim 7 , wherein said crystal is a ε-type crystal and which method comprises dissolving said crystal in a first solvent to form a mixture; and thereafter, adding a second solvent to said mixture, wherein a combination of said first solvent and said second solvent is one of dichloromethane/ethanol and dimethylsulfoxide/diethylether.

13. The method according to claim 7 , wherein said crystal is a θ-type crystal and which method comprises suspending the compound of the formula (I) in a solvent which is a mixture of a first solvent and a second solvent; and stirring the mixture 40° C. or higher to obtain said crystal, wherein said first solvent is acetonitrile and said second solvent is one of dimethylformamide and water.

14. The method according to claim 13 , wherein a volume ratio of said first solvent to said second solvent is from 50:50 to 95:5.

15. The method according to claim 13 , further comprising filtering said crystal at a temperature of 40° C. or higher.

16. The method according to claim 13 , wherein said first solvent is acetonitrile and said second solvent is water and a volume ratio between acetonitrile and water is from 90:10 to 80:20.

17. The method according to claim 13 , wherein said stirring is carried out a temperature of from 40° C. to the boiling point of said solvent.