Polymorphs of sodium 4-[(4-chloro-2-hydroxybenzoyl) amino] butanoate

1. Form II of sodium 4-[(4-chloro-2-hydroxybenzoyl)-amino]-butanoate.

2. A crystalline hydrate of sodium 4-[(4-chloro-2-hydroxybenzoyl)-amino]butanoate exhibiting an X-ray powder diffraction pattern substantially as shown in FIG. 2 .

3. A hydrate of sodium 4-[(4-chloro-2-hydroxybenzoyl)amino]butanoate exhibiting an X-ray powder diffraction pattern having peaks in degrees 2Θ±0.2° 2Θ at 10.2, 18.3, 19.5, 19.8, 21.8, 23.5, 26.3, 27.8, 29.4, and 31.8.

4. The crystalline polymorph of claim 3 , wherein the hydrate has a melting point onset as determined by differential scanning calorimetry at about 214.24° C.

5. A crystalline polymorph of an isopropanol solvate of sodium 4-[(4-chloro-2-hydroxybenzoyl)amino]butanoate exhibiting an X-ray powder diffraction pattern substantially as shown in FIG. 3 .

6. A crystalline polymorph of an isopropanol solvate of sodium 4-[(4-chloro-2-hydroxybenzoyl)amino]butanoate exhibiting an X-ray powder diffraction pattern having peaks in degrees 2Θ±0.2° 2Θ at 5.5, 10.8, 11.9, 16.3, 17.3, 21.7, 24.7, 25.0, 26.1, and 26.4.

7. The crystalline polymorph of claim 6 , wherein the crystalline polymorph has a melting point onset as determined by differential scanning calorimetry at about 223.08° C.

8. A method of preparing Form II of sodium 4-[(4-chloro-2-hydroxybenzoyl)amino]butanoate comprising the steps of:

(a) dissolving 4-[(4-chloro-2-hydroxybenzoyl)-amino]butanoic acid in water to form an aqueous solution;

(b) adding a sodium source to the aqueous solution to Form II of sodium 4-[(4-chloro-2-hydroxybenzoyl)amino]butanoate.

9. A method of preparing Form II of sodium 4-[(4-chloro-2-hydroxybenzoyl)amino]butanoate comprising the step of exposing Form III, Form V, or amorphous sodium 4-[(4-chloro-2-hydroxybenzoyl)amino]butanoate or a mixture thereof to an effective amount of moisture for a sufficient time to Form II of sodium 4-[(4-chloro-2-hydroxybenzoyl)amino]butanoate.

10. A method of preparing Form II of sodium 4-[(4-chloro-2-hydroxybenzoyl)amino]butanoate comprising the step of drying Form IV of sodium 4-[(4-chloro-2-hydroxybenzoyl)amino]butanoate in an environment having less than about 55% relative humidity.

11. A method of preparing Form III of sodium 4-[(4-chloro-2-hydroxybenzoyl)amino]butanoate comprising the sequential steps of:

(a) dissolving 4-[(4-chloro-2-hydroxybenzoyl)-amino]butanoic acid in isopropanol to form a solution;

(b) heating the solution to above room temperature;

(c) adding a sodium source to the solution;

(d) heating the solution to reflux; and

(e) cooling the solution to yield Form III of sodium 4-[(4-chloro-2-hydroxybenzoyl)amino]butanoate.