The synthesis of 15N-labeled coprobiliverdin III, a bile pigment with four conjugated pyrrole nuclei and four carboxylic acid side chains, is described. Coprobiliverdin is structurally characterized by chemical and various spectroscopic methods (e.g. chromic acid degradation, UV-vis-, IR-, mass spectroscopy). The results of 15N NMR studies reveal the potential value of this compound as a probe for structural interactions in biliproteins and as a reference for the future investigation of natural bile pigments deriving from coproheme