Oxoanion Binding by Flexible Guanidiniocarbonyl Pyrrole−Ammonium Bis-Cations in Water

Abstract

The syntheses of several bis-cations 1-5 with a simple primary ammonium cation attached via flexible linkers of varying length to a guanidiniocarbonyl pyrrole oxo anion binding site are reported. In UV-binding studies in aqueous buffer solution these bis-cations showed efficient binding of various N-acetyl amino acid carboxylates. However, complex affinity is significantly depending on both the anion and the length of the linker in the bis-cation. With increasing linker length, complex stability first increases until an optimum is reached for bis-cation 3 with a C4-linker. Then the complex stability decreases again. The best binding substrate in this series is N-acetyl phenyl alanine, most likely due to additional cation-pi-interactions between the aromatic ring and the guanidiniocarbonyl pyrrole cation. The formation of the complex between bis-cation 3 and N-acetyl phenyl alanine carboxylate was investigated further by fluorescence titrations and NOE studies, as well as molecular mechanics calculations.

PEGylated sequence-controlled macromolecules using supramolecular binding to target the Taspase1/Importin α interaction

“…For the trivalent macromolecules, binding is in the µM range as was expected based on previous GCP ligands ( Figure 2). [29] Figure 2. SPR sensograms showing direct binding of trivalent GCP-ligands with and without PEG to immobilized Taspase1.…”

Self-association of an indole based guanidinium-carboxylate-zwitterion: formation of stable dimers in solution and the solid state

“…Nevertheless, zwitterion 2 is an efficient self-assembling molecule. This indole guanidinium cation might also be an interesting binding motif for the recognition of oxoanions by indole based receptors [27–29], similar to our guanidiniocarbonyl pyrrole cation [30–32]. …”

Conformationally preorganised hosts for anions using norbornane and fused [n]polynorbornane frameworks

“…In this context fused [n]polynorbornane frameworks again appear well suited as they can be readily synthesised to specific dimensions and can also be easily functionalised to include a variety of H-bond donors This article will focus on 'larger' scaffolds, nevertheless, researchers will be aware of anion hosts based on 'smaller' scaffolds such as pyrrole, 6 indole, 7 naphthalene, 8 naphthalimide, 9 and anthracene. 10 In addition, suitably functionalised metal templated architectures have also emerged as suitable for anion recognition and the subject has been recently reviewed.…”

“…Within this series (4)(5)(6) it was predicted that compounds 6a and 6b with endo/exo preorganisation would be more suited to tetrahedral anions such as dihydrogenphosphate and these anions would bind in the larger cleft of these hosts in a 1 : 1 host : guest (H : G) arrangement.…”