Bis(guanidinium) Receptors as Ribonuclease Active‐Site Model Systems: Structural Changes and Solvent Effects

Various bis(guanidinium) compounds have been synthesized and their abilities to cleave the RNA model compound HPNPP have been tested in acetonitrile and in water. Depending on the spacer length, the substitution of the guanidinium groups, and the presence of an internal base, different rate constants for the transesterification of HPNPP are observed in these two media. The steroid derived bis(guanidinium) compound 12 was identified as a superior system.