Caffieri S, Vedaldi D, Chilin A, Pozzan A
Department of Pharmaceutical Sciences, University of Padova, Padua, Italy.
J Photochem Photobiol B. 1994 Feb;22(2):151-5. doi: 10.1016/1011-1344(93)06965-6.
The formation of C4-cycloadducts by photoreaction of eight methyl derivatives of 8-azapsoralen with DNA was studied. The main reaction involves the furan ring of the compounds and the 5,6 double bond of thymine giving cis-syn adducts, although a minor amount of a cycloadduct with cytosine was also isolated for 4,4'-dimethylazapsoralen. The role of the nitrogen atom appears to depend on the electronic effect, leading to a decrease in the reactivity of the pyrone ring. As with psoralens, the methyl groups increase both the lipophilicity and, with the exception of the 5,4',5'-trimethyl derivative, the photoreactivity. However, methyl groups do not appear to influence the chemistry of the photoaddition.
