Psoralen-Deoxyribonucleic Acid Photoreaction. Characterization of the Monoaddition Products from 8-Methoxypsoralen and 4,5', 8-Trimethylpsoralent

ABSTRACT: The isolation and structural characterization are described of the major monoaddition products formed in the photoreaction of two naturally occurring psoralens, 8-methoxypsoralen and 4,5',8-trimethylpsoralen, with high molecular weight, double-stranded DNA. Hydrolysis of the psoralenmodified DNA and subsequent chromatography resulted in the isolation of four modified nucleosides from each psoralen. Structural characterization was accomplished by mass spectrometry and 'H N M R analysis. The major products, accounting for 44-52% of the covalently bound psoralen, are two diastereomeric thymidine adducts formed by cycloaddition between the 5,6 double bond of the pyrimidine and the 4',5' (furan) double bond of the psoralen. A minor product, less than 2% of the covalently bound psoralen, is a furan-side E o r a l e n s or furocoumarins are a class of compounds found in a wide variety of plants and'fungi and have been used since ancient times as dermal photosensitizing agents for the treatment of various skin pigmentation disorder