As part of a program aiming to obtain a covalent labeling of serotoninergic receptors we have studied the oxidative coupling of serotonin derivatives with amino compounds. The oxidation of bufotenine (2) by MnO2 and human ceruloplasmin followed by the Michael type addition with dansylcadaverine and dansyllysine gave a fluorescent adduct identified as fused oxazole structure 4.