Stable monohydrate of df2755a and process for its preparation

A process for the preparation of crystalline monohydrate sodium (2S)-2-(4-{[4-(trifluoromethyl)-1,3-thiazol-2-yl] amino} phenyl) propanoate comprising:

• i) providing anhydrous sodium (2S)-2-(4-{[4-(trifluoromethyl)-1,3-thiazol-2-yl] amino} phenyl) propanoate;
• and
• ii) exposing it to an atmosphere having a Relative Humidity (R.H.) higher than 60% and lower than 80% by weight, at a temperature from 25° C. to 40° C. and at atmospheric pressure, thus providing crystalline monohydrate sodium (2S)-2-(4-{[4-(trifluoromethyl)-1,3-thiazol-2-yl] amino} phenyl) propanoate.

A process for the preparation of anhydrous sodium (2S)-2-(4-{[4-(trifluoromethyl)-1,3-thiazol-2-yl] amino} phenyl) propanoate comprising:

• providing a solution of (2S)-2-(4-{[4-(trifluoromethyl)-1,3-thiazol-2-yl] amino} phenyl) propanoic acid in a solvent selected among ethyl acetate, isobutyl acetate, propyl acetate and admixtures thereof, in which the concentration of the acid in the solution is from 0.08 to 0.12 kg/I,
• adding to the solution a sodium base in a molar ratio compared to the acid from 0.9:1 to 0.95:1, thus providing an admixture,
• adding to the admixture an anti-solvent selected among toluene, m-xylene, p-xylene and admixtures thereof, the anti-solvent being in a volumetric ratio compared to the solvent from 0.4:1 to 0.6:1, thus precipitating anhydrous sodium (2S)-2-(4-{[4-(trifluoromethyl)-1,3-thiazol-2-yl] amino} phenyl) propanoate.