Optimization of the binding properties of a synthetic anion receptor using rational and combinatorial strategies

Abstract

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Amino acid containing anion receptors

“…In chloroform, investigation of anion affinity of 12a is complicated by the fact that the peptide adopts a non-symmetrical conformation stabilized by an intramolecular hydrogen bond. 78 Since affinity of neutral receptors that rely on hydrogen bonding for anion coordination generally decrease with increasing polarity of the solvent 79 it was particularly surprising when we detected strong interactions of 12a with anions such as sulfate and halides in highly competitive protic solvent mixtures such as 80% D 2 O-CD 3 OD. 77 The reason for this unusual behavior turned out to be the special structure of the complexes formed.…”

“…85 Comparison of the binding equilibria on the basis of the association constants determined for 12a and 13a showed that anion complexation of the bis(cyclopeptide) is significantly more efficient than that of the monotopic analog. 78 A systematic evaluation of the influence of linker structure on anion affinity has also been performed. For this, the sulfate and halide affinities of bis(cyclopeptides) 13b-c (Chart 7), whose linkers become progressively more rigid, were compared to that of 13a.…”

“…2) and of the sulfate complex of 14b suggest that this energy term most probably comes from hydrophobic interactions between the non-polar surfaces of the proline rings in the two cyclopeptide moieties. Further arguments supporting this assumption are (i) complex formation of the monomeric cyclopeptide 12a in aqueous solution is highly cooperative with a large stability constant associated with the formation of the 2 : 1 complexes from relatively instable 1 : 1 complexes, 84 (ii) the monomeric cyclopeptide 12a forms 1 : 1 anion complexes in DMSO where hydrophobic interactions do not take place, 78 and (iii) the hydroxyproline containing cyclopeptide 12b forms 1 : 1 complexes even in aqueous solution because hydrophobic interactions between the more polar subunits of this peptide are significantly impaired. 84 We thus concluded that reinforcement of molecular recognition through intrareceptor interactions such as the hydrophobic interactions between the proline rings in our anion binding bis(cyclopeptides) should be an attractive general strategy to boost host-guest affinities.…”

Sensitive water-soluble fluorescent chemosensor for chloride based on a bisquinolinium pyridine-dicarboxamide compound

“…Artificial biomimetic receptors containing amide and urea groups as anion recognition sites constitute one of the largest sub-groups in this field (Asthana et al, 2013;Chang et al, 2015;Ge et al, 2014;Kubik et al, 2005;Lin et al, 2015;Pinter et al, 2013;Warwick et al, 2013;White and Beer, 2013;White et al, 2014, Warwick et al, 2013. Chloride recognition with these systems is mostly achieved by hydrogen bonding interactions, which in many cases are not strong enough to overcome the high energy of hydration (ΔG = -340 kJ/mol) besides the fact that water molecules efficiently compete for the binding sites (Butler and Parker, 2013;Kubik, 2010).…”

Dynamic Combinatorial Libraries Based on Hydrogen‐Bonded Molecular Boxes

“…In recent years, examples of the combination of noncovalent interactions and dynamic covalent bonds have also appeared 3b–g. DCC has received increasing attention because new catalysts, receptors, and sensors have been identified by using this approach 2f–j…”