Molecular Recognition with Convergent Functional Groups. 6. Synthetic and Structural Studies with a Model Receptor for Nucleic Acid Components

Experimental details are given for the synthesis and characterization of a new class of model receptors for adenine derivatives. The molecules feature an imide function and a suitably placed aromatic surface that permit simultaneous base pairing and aryl stacking interactions. The structures are built from the Kemp tricarboxylic acid 3 and suitable spacers with aromatic surfaces attached via ester or amide linkages. The general features of complexation with 9-ethyladenine in CDC1₃are established by NMR techniques involving chemical shift changes and NOE experiments. These establish that Watson-Crick, Hoogsteen, and bifurcated hydrogen bonds are present in the complexes. Aryl stacking interactions are controlled by the size of the aromatic surface and its pendant functionality. Model receptors bearing two imide functions act as molecular chelating agents for adenine and its derivatives. The highly organized hydrogen-bonding surfaces presented by these systems permit extraction of adenine derivatives from aqueous solution into CDC1₃.