A series of heterocyclic coupling agents having tuned hydrophobic chains, has been prepared by reaction of diamino or hydroxy-aminopyridines and p-aminosalicylic acid.The acetylation of amino group and hydroxyl in oxazole derivatives showed a selectivity depending on wether acetic anhydride or acetyl chloride was used.Correlations between structure and spectroscopic data, including related compounds previously described, are reported.