Oxazolidinone‐containing pseudopeptides: Supramolecular materials, fibers, crystals, and gels

Abstract

The formation of fibers through self-assembly is of particular interest, as fibrous proteins (such as collagen, keratin, actin, and so on) are involved in intra- and extracellular functions. To understand aggregation phenomena, oligopeptides may be designed and prepared either to mimic or to interfere with these processes. In this article, we will demonstrate that the introduction of the 4-methyl-5-carboxy-oxazolidin-2-one (Oxd) moiety inside a peptide chain favors the formation of fiber-like materials organized either in β-sheets or in supramolecular helices, provided that it is combined with other factors, like π-stacking interactions and intermolecular NH•••OC bonds. The presence of the Oxd moiety is essential for the material formation: when Oxd is replaced with Pro, only liquids or amorphous solids are obtained. Remarkably, some of these molecules are low-molecular-weight gelators, as they induce the formation of both organogel and hydrogels that have been used for several applications.

Fluorine Effect in the Gelation Ability of Low Molecular Weight Gelators

“…We compared the gelation ability of Boc-D-F 2 -Phe-OH (Boc = tert -butoxycarbonyl) with that of dipeptides where it was coupled with L-Oxd or D-Oxd (Oxd = 4-methyl-5-carboxy-oxazolidin-2-one) and we found out that Boc-D-F 2 Phe-L-Oxd-OH has the best performance among them. We used the Oxd moiety because we could demonstrate that its introduction in a peptide sequence strongly enhances the tendency of the molecule to self-assemble to form supramolecular materials [ 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ].…”

Supramolecular Hydrogels with Properties Tunable by Calcium Ions: A Bio-Inspired Chemical System

“…Recently, we investigated the formation of SAFiN hydrogels and organogels, using LMWGs containing either protected amino acids or the pseudoproline (4 R ,5 S )-4-methyl-5-carboxyl-oxazolidin-2-one (D-Oxd), and we could demonstrate that they have an essential role in the design of efficient gelators. , We also tested the gelation ability of an L-DOPA derivative, which forms strong supramolecular hydrogels and organogels. , For our continuous effort to find some new gelators able to form stable hydrogels useful for different applications, now we show the results obtained using Boc-L-DOPA­(OBn) 2 -OH ( A ) as the hydrogelator (Figure ). This compound displays two additional benzyl esters in the chemical structure that should improve its gelation efficiency through additional π–π stacking interactions.…”

The Diverse World of Foldamers: Endless Possibilities of Self-Assembly

“…Additionally, oligomers built using exclusively non-standard α-amino acids, or a mixture of proteinogenic and non-proteinogenic α-residues, have been almost completely excluded from this review, albeit their interesting studies sometimes included the use of peculiar experimental techniques. For instance, this exclusion applies to α-peptides containing mainly α-aminoisobutyric acid (Aib), for which only a few illustrative examples have been reported here, [ 34 ] and chiral α-dialkyl α-amino acids (e.g., synthetic derivatives of naturally-occurring peptaibiotics and peptaibols [ 35 , 36 , 37 ]), whose self-assembly has been thoroughly studied [ 38 , 39 , 40 ], especially in the presence of phospholipid membranes [ 41 ], as shown in Figure 3 d, and to low-molecular-weight gelators (LMWGs) based on short α-peptide derivatives [ 42 , 43 , 44 ] or pseudopeptides [ 45 , 46 ], which do not fulfill the foldamer definition adopted here. In addition, oligomers made only of different pseudoproline units (L-pyroglutamic acid, L- p Glu, trans -4-carboxybenzyl-5-methyloxazolidin- 2-one, L- or D-Oxd, and (4 R )-(2-oxo-1,3-oxazolidin-4-yl)-acetic acid, D-Oxac), as shown in Figure 3 e, which are sometimes included in the field of foldamers, have been excluded here [ 47 ].…”