@article{FudickarMetzMaiLindeetal.2021,
  author    = {Fudickar, Werner and Metz, Melanie and Mai-Linde, Yasemin and Kr{\"u}ger, Tobias and Kelling, Alexandra and Sperlich, Eric and Linker, Torsten},
  title     = {Influence of functional groups on the ene reaction of singlet oxygen with 1,4-cyclohexadienes},
  series = {Photochemistry and photobiology : the official journal of the American Society for Photobiology},
  volume    = {97},
  journal   = {Photochemistry and photobiology : the official journal of the American Society for Photobiology},
  number    = {6},
  publisher = {Wiley},
  address   = {Malden, Mass.},
  issn      = {0031-8655},
  doi       = {10.1111/php.13422},
  pages     = {1289 -- 1297},
  year      = {2021},
  abstract  = {The photooxygenation of 1,4-cyclohexadienes has been studied with a special focus on regio- and stereoselectivities. In all examples, only the methyl-substituted double bond undergoes an ene reaction with singlet oxygen, to afford hydroperoxides in moderate to good yields. We explain the high regioselectivities by a "large-group effect" of the adjacent quaternary stereocenter. Nitriles decrease the reactivity of singlet oxygen, presumably by quenching, but can stabilize proposed per-epoxide intermediates by polar interactions resulting in different stereoselectivities. Spiro lactams and lactones show an interesting effect on regio- and stereoselectivities of the ene reactions. Thus, singlet oxygen attacks the double bond preferentially anti to the carbonyl group, affording only one regioisomeric hydroperoxide. If the reaction occurs from the opposite face, the other regioisomer is exclusively formed by severe electrostatic repulsion in a perepoxide intermediate. We explain this unusual behavior by the fixed geometry of spiro compounds and call it a "spiro effect" in singlet oxygen ene reactions.},
  language  = {en}
}
@article{FudickarRoderListeketal.2021,
  author    = {Fudickar, Werner and Roder, Phillip and Listek, Martin and Hanack, Katja and Linker, Torsten},
  title     = {Pyridinium alkynylanthracenes as sensitizers for photodynamic therapy},
  series = {Photochemistry and photobiology},
  volume    = {98},
  journal   = {Photochemistry and photobiology},
  number    = {1},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {0031-8655},
  doi       = {10.1111/php.13554},
  pages     = {193 -- 201},
  year      = {2021},
  abstract  = {Photodynamic therapy (PDT) is a mild but effective method to treat certain types of cancer upon irradiation with visible light. Here, three isomeric methylpyridinium alkynylanthracenes 1op were evaluated as sensitizers for PDT. Upon irradiation with blue or green light, all three compounds show the ability to initiate strand breaks of plasmid DNA. The mayor species responsible for cleavage is singlet oxygen (O-1(2)) as confirmed by scavenging reagents. Only isomers 1m and 1p can be incorporated into HeLa cells, whereas isomer 1o cannot permeate through the membrane. While isomer 1m targets the cell nucleus, isomer 1p assembles in the cellular cytoplasm and impacts the cellular integrity. This is in accordance with a moderate toxicity of 1p in the dark, whereas 1m exhibits no dark toxicity. Both isomers are suitable as PDT reagents, with a CC50 of 3 mu m and 75 nm, for 1p and 1m, respectively. Thus, derivative 1m, which can be easily synthesized, becomes an interesting candidate for cancer therapy.},
  language  = {en}
}