RNA Hydrolysis by Heterocyclic Amidines and Guanidines: Parameters Affecting Reactivity

2-Aminobenzimidazole 10, although a weak catalyst in the monomeric state, is successful building block for effective artificial ribonucleases. In an effort to identify new blocks with improved catalytic potential, RNA cleavage by variety of heterocyclic amidines and guanidines has been studied. addition pKa values steric effects, energy difference between tautomeric forms seems be another important parameter catalysis. This information available from quantum chemical calculations on higher levels, but semiempirical methods are sufficient get first estimate. According this assumption, imidazoimidazol 18, characterized isoenergetic forms, superior 2-aminoimidazol 6, best candidate among simple compounds. By far largest effects seen 2-aminoperimidine 24, which rapidly cleaves even micromolar concentration range. The impressive reactivity, however, related tendency compound 24 form polycationic aggregates actual catalysts.