Theoretical Studies on the Photocycloaddition Reaction of Psoralen with Thymidine

摘要

The theoretical studies on the photocycloaddition reaction of 5,7-dimethoxycoumarin and 4`,5`-dihydropsoralen with thymidine were carried out as a model for photosensitizing reaction of psoralen with DNA. The results are in reasonable agreement with experimental observations. The photoadducts between dimethoxycoumarin and thymidine were predicted to be C4-cycloadducts through the cycloaddition of 3,4-pyrone double bond of dimethoxycoumarin to 5,6 double bond of thymidine. The major photoadduct of 4`,5`-dihydropsoralen with thymidine has the anti head-to-head stereochemistry.