Synthesis of Dopamines Labelled with 13C in the α‐ or β‐Side Chain Position and Their Application to Structural Studies on Melanins by Solid‐State NMR Spectroscopy

Solid‐state NMR spectroscopy was applied to the analysis of melanins prepared by peroxidase‐H2O2 oxidation of dopamines specifically 13C labelled in the α‐ or β‐side chain positions. A surprisingly diverse pattern of signals indicated the presence of uncyclized dopamine and noradrenaline‐derived units, in addition to indole and carbonyl carbon atoms. These structural features, coupled with the results obtained from elemental analysis of dopamine melanin samples prepared under different conditions, point to a pigment formation process more complex than previously believed. magnified image