Process for the purification of 2-phenyl-2-methyl-propanoic acid derivatives

A purification process for obtaining a compound of formula (XIV) as a single para-isomer, a salt thereof, or an ester thereof,

• wherein W is a group chosen from
• and Z-(CH2)3-CO-, in which Z is a halogen atom, from a mixture of regioisomers of a compound of formula (XV)
• said process comprising:
• selectively preparing an ammonium salt of a compound of formula (XIV), by reacting the mixture of regioisomers of formula (XV) with an amine selected from the group consisting of cyclopropylamine, cyclohexylamine, and dicyclohexylamine;
• wherein the ratio of the meta-isomer to the para-isomer in the mixture of regioisomers of a compound of formula (XV) ranges from about 5/95 to about 50/50;
• separating by crystallization the ammonium salt of the compound of formula (XIV);
• recovering the ammonium salt;
• and optionally converting the ammonium salt into the free acid or into another salt thereof, or into an ester thereof.