MONOFUNCTIONAL 4′,5′‐PHOTOCYCLOADDUCT BETWEEN 4,5′‐DIMETHYLANGELICIN AND THYMINE

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Abstract
A new fluorescent compound has been isolated from the products of hydrolysis of DNA irradiated in the presence of 4,5′‐dimethylangelicin, a monofunctional photosensitizing furocoumarin. The marked similarity of the UV absorption and fluorescence spectra of this photoproduct to those of 4′,5′‐dihydro‐4,5′‐dimethylangelicin, as well as its behaviour on photodissociation (254 nm) yielding thymine and 4,5′‐dimethylangelicin in equimolecular amounts, are consistent with a cycloadduct between one molecule of 4,5′‐dimethylangelicin and one of thymine, and the C4‐cycloaddition occurs through 4′,5′–double bond of the furocoumarin and the 5,6‐double bond of the pyrimidine.