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The recognition of either homomeric or heteromeric pairs of pentoses in an aromatic oligoamide double helical foldamer capsule was evidenced by circular dichroism (CD), NMR spectroscopy, and X‐ray crystallography. The cavity of the host was predicted to be large enough to accommodate simultaneously two xylose molecules and to form a 1:2 complex (one container, two saccharides). Solution and solid‐state data revealed the selective recognition of the α‐4C1‐d‐xylopyranose tautomer, which is bound at two identical sites in the foldamer cavity. A step further was achieved by sequestering a heteromeric pair of pentoses, that is, one molecule of α‐4C1‐d‐xylopyranose and one molecule of β‐1C4‐d‐arabinopyranose despite the symmetrical nature of the host and despite the similarity of the guests. Subtle induced‐fit and allosteric effects are responsible for the outstanding selectivities observed., Two monosacharides fit in an aromatic double helical foldamer container. Binding is shown to be selective in terms of the sugar anomer, pyranose/furanose tautomer, and helix handedness, and leads to well defined homomeric or heteromeric complexes. One heteromeric complex selectively forms out of 42 different possibilities.

A new double helical aromatic oligoamide capsule able to bind to citric acid in polar and protic solvents was prepared. Aromatic amino acids in the sequence encode both structural (strand curvature and double helix formation) and functional features (recognition pattern) of the assembled capsule.

International audience; Aromatic oligoamide sequences able to fold into single helical capsules were functionalized with two types of side chains to make them be soluble in various solvents such as chloroform, methanol or water and their propensity to recognize tartaric acid was evaluated. Binding affinities to tartaric acid and binding thermodynamics in the different media were investigated by variable temperature 1 H NMR and ITC experiments, the two methods giving consistent results. We show that tartaric acid binding mainly rests on enthalpically favourable polar interactions that were found to be sufficiently strong to be effective in presence of a polar aprotic solvent (DMSO) and even in pure methanol. Binding in water was very low. The stronger binding interactions were found to be more susceptible to the effect of competitive solvents and to be compensated by unfavourable entropic effects. Thus, the best host in less polar medium eventually was found to be the worst host in protic solvents. An interesting case of entropically driven binding was evidenced in methanol.

The ab initio design of synthetic molecular receptors for a specific biomolecular guest remains an elusive objective, particularly for targets such as monosaccharides, which have very close structural analogues. Here we report a powerful approach to produce receptors with very high selectivity for specific monosaccharides and, as a demonstration, we develop a foldamer that selectively encapsulates fructose. The approach uses an iterative design process that exploits the modular structure of folded synthetic oligomer sequences in conjunction with molecular modelling and structural characterization to inform subsequent refinements. Starting from a first-principles design taking size, shape and hydrogen-bonding ability into account and using the high predictability of aromatic oligoamide foldamer conformations and their propensity to crystallize, a sequence that binds to β-D-fructopyranose in organic solvents with atomic-scale complementarity was obtained in just a few iterative modifications. This scheme, which mimics the adaptable construction of biopolymers from a limited number of monomer units, provides a general protocol for the development of selective receptors.