or an esterified carboxyl having 1 to 4 carbon atoms; or b4) R???1 is an aryl group of general formula IV, which is unsubstituted or substituted, wherein: R???5 is hydrogen or one or more substituents selected from the group consisting of a halogen, a hydroxyl group, an alkyl having 1 to 4 carbon atoms, an alkoxyl having 1 to 4 carbon atoms, an acyloxyl having 1 to 4 carbon atoms or an esterified