5-(2-carboxy-2-aminoethyl)-2-hydroxy-1,4-benzoquinone5-(2-carboxy-2-aminoethyl)-4-hydroxy-1,2-benzoquinone2,4,5-trihydroxyphenylalanine quinoneTopa quinone6-hydroxydopa quinonetopa quinoneL-topaquinone(S)-alpha-amino-4-hydroxy-3,6-dioxo-1,4-cyclohexadiene-1-propanoic acid6-hydroxydopa quinonetopaquinone