Synthesis of 3-(3,4-dihydroxyphenyl)-propionic acid derivatives by N-coupling of amines using laccase

Derivatization of the natural compound 3-(3,4-dihydroxyphenyl)-propionic acid (dihydrocaffeic acid) can be achieved by laccase-catalyzed N-coupling of aromatic and aliphatic amines. Incubation of 3-(3,4-dihydroxyphenyl)-propionic acid and 4-aminobenzoic acid with laccase in aqueous medium and in the presence of oxygen yielded 3-[6-(4-carboxyphenyl)amino-3,4-dihydroxyphenyl]-propionic acid as the main product (>80%). Reaction with hexylamine resulted in 3-(6-hexylamino-3,4-dihydroxyphenyl)-propionic acid as the only product (60%).