Molecular recognition of organic acids and anions — Receptor models for carboxylates, amino acids, and nucleotides

Tuning the hydrogen-bonding strength in 2,6-bis(cycloalkylcarbonylamino)pyridine assemblies by variable flexibility. Association constants measured by hydrogen-bonded vs. non-hydrogen-bonded protons

“…Thus monitoring several nuclei is the method of choice to improve the reliability of obtained results. Triple hydrogen-bonded associates are met in many structures as in DNA [14,15], amides [16,17], artificial sensors [18][19][20][21][22], materials [23], non-covalent polymers [4,[24][25][26][27][28] and in recently observed associates of orotic acid [29,30]. Triple hydrogen-bonded assemblies carrying 2,6-diaminopyridine DAD-hydrogen bonding moiety were studied by some groups with the use of various methods [4,6,[31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] and also by us [48,49].…”

Biomimetic macrocyclic receptors for carboxylate anion recognition based on C -linked peptidocalix[4]arenes

“…T he selective complexation of carboxylate anions by natural and synthetic hosts is a topic of current interest in bioorganic and supramolecular chemistry (1)(2)(3)(4)(5), because these species are involved in several molecular recognition phenomena of biological interest. It is worth noting the special role that carboxylate recognition plays in determining the biological activity of the vancomycin family of antibiotics (6).…”

“…We have recently synthesized a series of upper rim N-linked (13)(14)(15) and C-linked (16) peptidocalix [4]arenes with the aim of obtaining novel chiral receptors for amino acids and small peptides (Scheme 1).…”

“…Interestingly, some of the upper rim bridged peptidocalix [4]arenes (e.g., I) behave as vancomycin mimics and show promising antibiotic activity toward Gram-positive bacterial strands as a consequence of their ability to bind the D-alanyl-D-alanine (D-ala-D-ala) terminal part of peptoglycans (13,17). Both the N-linked (e.g., II) and C-linked (e.g., III) cleft-like peptidocalix [4]arenes are very poor receptors in the recognition of ions and polar organic molecules, mainly because of their residual conformational flexibility, which, in the case of C-linked compounds, leads to extensive intramolecular H bonding (see III).…”

“…Both the N-linked (e.g., II) and C-linked (e.g., III) cleft-like peptidocalix [4]arenes are very poor receptors in the recognition of ions and polar organic molecules, mainly because of their residual conformational flexibility, which, in the case of C-linked compounds, leads to extensive intramolecular H bonding (see III). To reduce this conformational flexibility, we decided to cap the C-linked peptidocalix [4]arenes with suitable aromatic units and to explore the host properties of macrobicyclic receptors 4 and 6, in particular toward anionic guest species. The solid-state structure of receptor 6 was determined by x-ray crystallography, whereas two-dimensional NMR was used to clarify the solution structures of both 4 and 6.…”