Psoralen thymidine monoadduct

The total synthesis of psoralen-thymidine monoadducts is of considerable importance in studies of nucleoside damage arising from radiation, chemical carcinogens and chemotherapeutic agents. Within helical DNA, psoralens (155) photoreact with thymidine to form a cis-syn [2+2]adduct. Outside the DNA helix, achievement of the required cis-syn addition has been very difficult and is complicated by the ease of psoralen photodimerisation. Efficient routes to a psoralen-thymidine adduct have used benzofuran derivative (156) which provides a tethered arrangement to ensure the correct cyclobutane stereochemistry. Irradiation in acetonitrile containing acetone, followed by methanol/silica gel... 

FIGURE 142.4 Molecular structure of mono- and diadducts between psoralen and thymidine. 1 furan side monoadduct involving the 4, 5 double bond of psoralen and the 5,6 double bond of thymidine 2 Pyrone side monoadduct involving the 3,4 double bond of psoralen and the 5,6 double bond of thymidine 3 diadduct involving... 

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