Preferential extraction of the (+)-TB isomer by butanol from the water solution containing racemic TB and DNA unambiguously proves that the (-) isomer selectively binds to calf-thymus DNA. The 7R,17R configuration was assigned to the (-)-TB enantiomer based on its circular dichroism spectrum (exciton mechanism). This configuration is consistent with enantioselective binding to right-handed B-DNA either through intercalation or by interaction in the groove.




This study shows that Tröger's Bases represent a new class of enantioselective DNA-binders that can be compared to the extensively studied metallocomplexes. The (-)-TB enantiomer binds to B-DNA. It would be now interesting to study the binding of the two isomers with Z-DNA and other DNA conformations and structures.

The potentiality of the series resides in the numerous variations that can be introduced. Various amino substituted aromatic subunits can be envisioned for the building of the Tröger's Base and different substituents can be introduced to give to the molecules the solubility, luminescent, photochemical, or cleavage properties required for the design of new DNA (or RNA) conformation probes.

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