Supramolecular Structures Generated by a p‐tert‐Butylphenyl‐amide Derivative of Cholic Acid: From Vesicles to Molecular Tubes

Abstract

The formation of supramolecular structures initiated by a p‐tert‐butylphenyl‐amide derivative of cholic acid is investigated. The initial spherical vesicles, with a rather low effective bending constant, collapse into necklaces that self‐transform into tubules of small diameter. Finally, molecular tubes are generated (see figure). During the process, the geometrical constraints of fixed surface area and fixed enclosed volume are obeyed.

Bile acid alkylamide derivatives as low molecular weight organogelators: Systematic gelation studies and qualitative structural analysis of the systems

“…Examples of reported structures in solution-, sol-, gel-, or solid-state include various types of micelles [32,33], ribbon-or rod-like fibers [34][35][36][37][38], twisted ribbons [39], vesicles or spherical aggregates [29,40], lamellae [41], and tubules or nanotubes [42][43][44]. In general, physical gels of bile acids consist of one dimensional (1D) structures, such as various kinds of fibers of twisted, flat, or cylindrical form [22][23][24][26][27][28]31,[34][35][36][37][38].…”

“…Aggregation, and in a wider sense, self-assembling potential of natural-and modified-bile salts, as well as neutral bile acid derivatives, lead to a diverse library of structures at the nano-and micro-scale in water and organic solvents [32][33][34][35][36][37][38][39][40][41][42][43][44]. Examples of reported structures in solution-, sol-, gel-, or solid-state include various types of micelles [32,33], ribbon-or rod-like fibers [34][35][36][37][38], twisted ribbons [39], vesicles or spherical aggregates [29,40], lamellae [41], and tubules or nanotubes [42][43][44].…”

A tryptophan-substituted cholic acid: Expanding the family of labelled biomolecules

“…For example, the functionalization of both the side chain and the tetracyclic system is observed to lead to efficient gelators in organic solvents as well as in aqueous solutions [22], and the possibility to enhance their efficiency by using catanionic mixtures of the derivatives was demonstrated [23], whereas the BAs functionalized in their rigid backbone, selfassemble into lamellae or tubules [24][25][26][27][28][29][30]. In particular, the selective substitution of one of the steroid hydroxyl groups by an adamantly group gives derivatives that self-organize in lamellar arrays [24], whereas the introduction of an aromatic residue gives compounds able to self-associate into tubular structures [26][27][28][29][30][31][32][33][34] showing sometimes unique features such as extremely narrow cross sections [27,28], thermo- [33,34] or pH-responsive aggregations [32] and catanionic controlled Page 3 of 25 A c c e p t e d M a n u s c r i p t 4 compositions [31]. Tubular structures are also formed by BA molecules substituted with monosaccharide residues through an unusual mechanism involving scrolls as intermediates [25], whereas vesicles are given by some Gemini derivatives [35].…”

Crystal Structure of a Head-to-Head Bis(cholic)-Urea Dimer

“…2 The amphipathic character of these compounds, due to the hydrophilic/hydrophobic bifacial structure, results in the fact that bile acids are among the most important biological surfactants. The hydroxyl groups and the side chain (supporting a carboxylic group) have made them very attractive building blocks for forming supramolecular structures, [3][4] novel antibiotics, 5 new surfactants, [6][7][8] organogelators, 9 etc. Bile acids derivatives are especially useful as scaffolds for anion receptors, mainly when helpful substituents are incorporated into their structure.…”