USING GUANIDINIUM GROUPS FOR THE RECOGNITION OF RNA AND AS CATALYSTS FOR THE HYDROLYSIS OF RNA

The guanidinium functional group is commonly used in nature to recogni ze and bind anions through ion pairing and hydrogen bonding. Specific hydrogen-bonding patterns can be found in crystal structures of simple guanidinium salts. Analysis of these simple salts reveals a variety o f features which are found in natural systems. These features have bee n applied to a series of artificial phosphodiesterases for RNA. These receptors incorporate guanidinium groups positioned to mimic the hydro gen-bonding patterns found in simple guanidinium salts and natural enz ymes. This paper outlines general guanidinium hydrogen-bonding pattern s. Next, the complexation of phosphodiesters with a series of artifici al receptors are analyzed in terms of counterions, solvent mixtures, a nd cavity flexibility. In addition, strategies to enhance catalysis th rough a pK(a) analysis of phosphoranes are addressed. Next, we describ e how our findings were incorporated into second generation receptors/ catalysts. Finally, our future work is discussed. (C) 1997 Elsevier Sc ience Ltd.