Foldamers Based on Oxazolidin‐2‐ones

Abstract

Foldamers are artificial molecules capable of organization into well defined secondary structures such as helixes, β sheets and turns. The essential requirement for an oligomer to qualify for inclusion in the foldamer family is to possess a well defined, repetitive secondary structure, imparted by conformational restrictions imposed by the monomeric unit. These compounds may be composed of subunits of any kind, but most of them contain unusual amino acids and/or aromatic units. We describe the synthesis, the conformation analysis and the physical properties (in the solid state) of pseudopeptide foldamers containing imido‐type functions, obtained by coupling the nitrogen of a 4‐carboxy oxazolidin‐2‐one unit with the carboxylic acid moiety of the next unit, which may be another 4‐carboxy oxazolidin‐2‐one or an amino acid. Such an imido‐type function is characterized by a nitrogen atom connected both to an endocyclic and to an exocyclic carbonyl group, and tends always to adopt the trans conformation. As a consequence of this remarkable property, which causes local constraint, these imido‐type oligomers are forced to fold in ordered conformations. In combination with interactions of other kinds (H bond, apolar interactions, etc.), these lead to the formation of supramolecular materials. The synthetic approach is highly tuneable with endless variations, so materials with required properties may be prepared “on demand”, simply by changing the design and the synthesis.

Chiral Gold Nanoparticles Decorated with Pseudopeptides

“…Notably, the amide group N4-HN4 of l-Ala1 is not engaged in intramolecular hydrogen bonds in the solid state, and the resulting picture matches remarkably well the results of IR and 1 H NMR investigations in solution. [11] We could demonstrate that a stable 3 10 helix is formed when n Ն 5. The backbone conformational parameters gathered in Table S4 show that the torsion angles (φ and ψ) at the l-Ala1 residue are similar to those of poly-l-proline II helix, as in related foldamers.…”

“…[9] The design strategy for the synthesis of a peptide-based capping ligand must address some key requirements. [11] Figure 1. Moreover, peptides need to have a strong affinity for gold and must be able to self-assemble into a dense layer that excludes water, while a hydrophilic terminus is required to achieve solubility and stability in water.…”

A peptidic hydrogel that may behave as a “Trojan Horse”

“…We have recently described the synthesis and the application of a small library of stereoisomeric compounds made of azelaic acid (a long chain dicarboxylic acid) coupled with different pseudopeptides, all containing the L-Phe-D-Oxd (Oxd = 4-carboxy-5-methyloxazolidin-2-one) moiety [19–21]. This skeleton is the minimal framework of a class of foldamers, having the ability to self-organize.…”

Asymmetric synthesis of γ-chloro-α,β-diamino- and β,γ-aziridino-α-aminoacylpyrrolidines and -piperidines via stereoselective Mannich-type additions of N-(diphenylmethylene)glycinamides across α-chloro-N-sulfinylimines

“…The trans -stereochemistry of imidazolidine 12b was ensured by the vicinal coupling constant 3 J H4-H5 = 7.43 Hz and the 1 H NMR chemical shift of H4 (3.85 ppm), which were in the same range as for closely related trans -imidazolidines and trans -oxazolidines [43–45]. The trans -imidazolidine 12b is a potential building block for foldamers, as the corresponding trans -oxazolidin-2-ones are already applied as such [46]. trans -Imidazolidine 12b could also be used as a precursor of the corresponding N α ,N β -deprotected α,β-diaminocarboxylamide, by hydrolysis under acidic conditions, in analogy with deprotection reactions of imidazolidines, imidazolines and oxazolines in the literature [16,47–48].…”