title: The first 5,6-dihydroxyindole tetramer by oxidation of 5,5',6,6'-tetrahydroxy- 2,4'-biindolyl and an unexpected issue of positional reactivity en route to eumelanin-related polymers.
abstract: [structure: see text]. The first tetramer of the eumelanin precursor 5,6-dihydroxyindole has been obtained, as the acetyl derivative, by peroxidase/H2O2-induced oxidative coupling of 5,5',6,6'-tetrahydroxy-2,4'-biindolyl (2) in the presence of Zn2+ ions. The tetramer, 5,5',5'',5''',6,6',6'',6'''-octaacetoxy-2,4':2',3'':2'',4'''-tetraindolyl (acetylated 7), incorporates an unprecedented 2,3'-biindolyl substructure suggestive of a different positional reactivity of the 5,6-dihydroxyindole system when framed into a dimeric scaffold.
authors.affiliation: Department of Organic Chemistry and Biochemistry, University of Naples Federico II, Via Cinthia, I-80126 Naples, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Panzella
authors.forename: Alessandro
authors.initials: A
authors.lastname: Pezzella
authors.forename: Alessandra
authors.initials: A
authors.lastname: Napolitano
authors.forename: Marco
authors.initials: M
authors.lastname: d'Ischia
mesh_terms: D007211:Indoles / Q000138:chemical synthesis* / Q000737:chemistry*; D008543:Melanins / Q000737:chemistry*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: C519475:5,5',6,6'-tetrahydroxy-2,4'-biindolyl; D007211:Indoles; D008543:Melanins; D011108:Polymers; C041877:eumelanin; C033871:5,6-dihydroxyindole