Process for preparing aromatic carboxylic derivatives triiodinated

A process for preparing a compound of formula Formula ** ** process comprises reacting a compound of formula II ** ** Formula with an α-hydroxyacid of formula III ** ** Formula or a salt thereof, in presence of a base, wherein: R 'is hydrogen or an alkyl group C1-C6 linear or branched optionally substituted by one or more groups hidroxiprotegidos; R, the same at each occurrence, is selected from the group consisting of -OR1 alkoxy, -NH2 or -NHR1 amino oun chlorine atom; R1 is a linear C1-C6 or branched group optionally substituted by one or more hydroxy groups protected.