Miolo G, Lucchini V, Rodighiero P, Dall'Acqua F, Caffieri S
Department of Pharmaceutical Sciences, University of Padua, Italy.
Photochem Photobiol. 1994 Mar;59(3):277-83. doi: 10.1111/j.1751-1097.1994.tb05034.x.
The isolation and characterization of photocycloadducts with pyrimidine bases from DNA samples irradiated (365 nm) in the presence of four 4',5'-substituted methylangelicins was performed. All these furocoumarins yielded mainly the cis-syn furan-side cycloadduct with thymine. For 4',5'-dimethyl-, 5,4',5'-trimethyl- and 6,4',5'-trimethylangelicin this adduct was accompanied by two pyrone-side adducts (cis-syn and cis-anti), whereas the 4,4',5'-trimethyl derivative gave the furan-side adduct with cytosine. The characterization of the regio- and stereochemistry of the adducts was accomplished by 1H NOE (nuclear Overhauser effect) and 1H-13C HMBC (heteronuclear multiple-bond connectivity) spectroscopies. The formation of different cycloadducts in DNA by the various derivatives highlights the role of the methyl groups in determining the regio- and stereochemistry of the cycloaddition.
