Molecular recognition between ligands and nucleic acids: novel pyridine- and benzoxazole-containing agents related to Hoechst 33258 that exhibit altered DNA sequence specificity deduced from footprinting analysis and spectroscopic studies.

The syntheses of certain analogues of the DNA minor groove binding agent Hoechst 33258 designed to exhibit altered sequence recognition are described. The structural modifications include the following: substitution of pyridine for the benzene ring of the benzimidazole moiety, replacement of one benzimidazole unit by a benzoxazole in the two possible orientations with respect to the DNA receptor, and a synthesis of 2,2'-m-phenylene-bis[6-(4-methyl-1-piperazinyl)benzimidazole]. Sequence recognition of these agents on a HindIII/EcoRI fragment of pBR322 DNA was determined by MPE footprinting procedures. Some of the analogues exhibited altered DNA sequence preference compared with Hoechst 33258. In particular, a structure bearing a benzoxazole moiety with the oxygen oriented inward to the minor groove together with an inward-directed pyridine nitrogen appears to confer the property of recognition of a GC base pair within the binding sequence. The possible factors, structural, stereochemical, and electrostatic, contributing to the altered DNA sequence recognition properties are discussed.