ORGANIC-PHOTOCHEMISTRY .98. TOWARD THE DEVELOPMENT OF PHOTO CISPLATINUM REAGENTS - REACTION OF CIS-DICHLOROBIS(1,10-PHENANTHROLINE)RHODIUM(III) WITH CALF THYMUS DNA, NUCLEOTIDES, AND NUCLEOSIDES

Photolysis of the title compound (cisDCBPR) with calf thymus DNA leads to the formation of covalent adducts. The reaction is not dependent on oxygen, proceeds with moderate (ca. 10(-3)) quantum efficiency, and occurs with modest enantioselectivity which is enhanced in low ionic strength media, where electrostatic and/or intercalatory association is evident. At least two covalent adducts involving deoxyguanosine as a ligand have been isolated from the enzymatic degradation of the metalated DNA, one of which is spectroscopically identical with an adduct prepared from the reaction of cisDCBPR with dG. Extensive spectral characterization of the second dG adduct implicates N1 as the point of attachment of Rh to the base. A stable adduct with dA has also been isolated from photolysis of the metal complex with the nucleoside, and a structure involving binding to N3 is tentatively assigned.