CONVERGENT FUNCTIONAL-GROUPS .13. HIGH-AFFINITY COMPLEXATION OF ADENOSINE DERIVATIVES WITHIN INDUCED BINDING POCKETS

Receptors based upon 3,6-diaminocarbazole have been synthesized that bind to adenosine derivatives with an interaction energy of approximately 8 kcal/mol in CDCl3 and over 3 kcal/mol in CD3OD. The purine nucleus is bound within a cavity by simultaneous Watson-Crick and Hoogsteen base-pairing, hydrogen bonding to N3, and stacking on both of its aromatic faces. Hydrogen bond interactions can be estimated at approximately 0.5-0.75 kcal/mol in methanol. The structure of the complex in solution has been deduced through binding assays of incremental derivatives, one- and two-dimensional NMR studies, and molecular modeling.