Intramolecular Photoreaction of Synthetic Oligopeptide-Linked Anthraquinone Molecules

Article abstract of DOI:10.1021/jo00049a019

Photoreaction of (N-acetylglycyl)oligopeptide-linked anthraquinone molecules was investigated.In an acetonitrile solution, the photoexcited anthraquinone moiety abstracted intramolecularly the hydrogen atom of the methylene site of glycine residue.The biradical formed was followed by the formation of C-O bonding via radical recombination to produce ring-closure products in high yields (23-58percent).A variety of oligopeptide spacers between acetylglycine and anthraquinone moieties were systematically changed, and their photoreactivities were investigated.The isolated ring-closure products showed a site-selectivity in the photoreaction; one of the carbonyl groups of anthraquinone moiety coupled with the methylene group predominantly (the selectivity was 88/12-100/0).The efficiency of the photocyclization was dependent upon the size and the sequence of the oligopeptide spacer.These results showed that the oligopeptide spacer might control the distance and the orientation among the reaction sites, glycine methylene, and anthraquinone carbonyl groups.