5-(2-carboxy-2-aminoethyl)-2-hydroxy-1,4-benzoquinone2,4,5-trihydroxyphenylalanine quinone6-hydroxydopa quinone5-(2-carboxy-2-aminoethyl)-4-hydroxy-1,2-benzoquinoneTopa quinonetopaquinoneL-topaquinone6-hydroxydopa quinonetopa quinone(S)-alpha-amino-4-hydroxy-3,6-dioxo-1,4-cyclohexadiene-1-propanoic acid