Potential DNA bis‐intercalating agents. Bridged bis‐(6‐chloropurines) and related compounds

Two bis‐(6‐chloropurines) bridged by conformationally restricted tethers were synthesized as potential DNA bis‐intercalating agents. Reduction of 4,6‐dichloro‐5‐nitropyrimidine (1) afforded 5‐amino‐4,6‐dichloropyrimidine (2) which was then used as the starting material. Reaction of 2 with 4,4′‐diaminodiphenylmethane (3) and bis‐(4‐aminophenyl) ether (4) yielded bis‐[4‐(N‐5‐amino‐4‐chloro‐6‐pyrimidyl)aminophenyl]methane (5) and bis‐[4‐(N‐5‐amino‐4‐chloro‐6‐pyrimidyl)aminophenyl] ether (6), respectively. Acid‐catalyzed condensation of the above pyrimidines, 5 and 6, with triethyl orthoformate in N,N‐dimethylacetamide gave bis‐[4‐(6‐chloro‐9‐purinyl)phenyl]methane (7) and bis‐[4‐(6‐chloro‐9‐purinyl)phenyl] ether (8). The spectral data on the new compounds will be discussed.