title: Toward hypericin-derived potential photodynamic therapy agents.
abstract: To optimize a hypericin derivative as a potential photodynamic therapy agent its light-induced singlet oxygen/superoxide radical formation capability should be enhanced and its long-wavelength absorption band should be bathochromically shifted to better match medicinal lasers. A heavy-atom-substituted derivative was realized by electrophilic iodination of hypericin to yield 2,5-diiodo-hypericin. Using photodestruction of bilirubin IX alpha this derivative was demonstrated to exhibit an enhanced light-induced singlet oxygen/superoxide radical formation capability as compared to hypericin. With respect to a bathochromically shifted derivative styryl residues were attached to the methyl groups of hypericin by de novo ring synthesis. Although the long-wavelength absorption band of this derivative displayed a bathochromic shift of nearly 40 nm it unfortunately immediately underwent an intramolecular [2 + 2] cycloaddition to yield the corresponding cyclobutane derivative in which the added conjugation system became interrupted.
authors.affiliation: Institute of Chemistry, Johannes Kepler University, Altenbergerstrasse 69, A 4040 Linz, Austria.
authors.forename: R A
authors.initials: RA
authors.lastname: Obermüller
authors.forename: K
authors.initials: K
authors.lastname: Hohenthanner
authors.forename: H
authors.initials: H
authors.lastname: Falk
mesh_terms: D000873:Anthracenes; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D010100:Oxygen / Q000737:chemistry; D010569:Perylene / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry*; D010777:Photochemistry; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000138:chemical synthesis / Q000737:chemistry*; D026082:Singlet Oxygen; D013481:Superoxides / Q000737:chemistry
chemical_list: D000873:Anthracenes; D017319:Photosensitizing Agents; D013481:Superoxides; D026082:Singlet Oxygen; D010569:Perylene; C004965:hypericin; D010100:Oxygen