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A hemicryptophane cage bearing amine and amide functions in its three linkers was synthesized in five steps. The X-ray molecular structure of the cage shows a triple-stranded helical arrangement of the linkers stabilized by intramolecular hydrogen bonds between amide and amine groups. The chirality of the cyclotriveratrylene unit controls the propeller arrangement of the three aromatic rings in the opposite part of the cage. 1 H NMR studies suggest that this structure is retained in solution.

A new chiral hemicryptophane cage combining an electron-rich cyclotriveratrylene (CTV) unit and polar amine functions has been synthesized. The resolution of the racemic mixture has been performed by chiral HPLC, and the assignment of the absolute configuration of the two enantiomers has been achieved using ECD spectroscopy. In contrast with other hemicryptophane receptors, the two enantiomeric hosts display both remarkable enantioselectivities in the recognition of carbohydrates and good binding constants. Moreover, by switching the chirality of the CTV unit from M to P, a strong preference shift from glucose to mannose derivatives is observed.

The recognition properties of heteroditopic hemicryptophane hosts towards anions, cations, and neutral pairs, combining both cation-π and anion-π interaction sites, were investigated to probe the complexity of interfering weak intermolecular interactions. It is suggested from NMR experiments, and supported by CASSCF/CASPT2 calculations, that the binding constants of anions can be modulated by a factor of up to 100 by varying the fluorination sites on the electron-poor aromatic rings. Interestingly, this subtle chemical modification can also reverse the sign of cooperativity in ion-pair recognition. Wavefunction calculations highlight how short- and long-range interactions interfere in this recognition process, suggesting that a disruption of anion-π interactions can occur in the presence of a co-bound cation. Such molecules can be viewed as prototypes for examining complex processes controlled by the competition of weak interactions., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Four new enantiomerically and diastereomerically pure hemicryptophane hosts (M-SSS-2/P-SSS-2 and M-RRR-2/P-RRR-2 pairs) were designed for the recognition of sugar derivatives. Their absolute configuration was determined from the circular dichroism spectra and DFT calculations. The host molecules were then used for the stereoselective recognition of glucopyranosides. Binding constants were obtained from (1)H NMR titration experiments showing an increase of affinity for this class of receptors, associated with an improved diastereo- and enantio-differentiation.

Efficient alkane C-H bond oxidation was achieved using a newly designed Cu(II)-hemicryptophane complex. Protection of the copper site in the inner cavity of the host leads to enhanced yields and allows discriminating cyclohexane from cyclooctane or adamantane in competitive experiments.

Three copper(II)@hemicryptophane complexes with various cavity sizes and shapes, Cu(II)@1, Cu(II)@2 and Cu(II)@3, were synthesized and characterized by near-IR/vis and EPR spectroscopies. The spectroscopic data are consistent with the presence of a trigonal-bipyramidal geometry of the N(4)Cu·H(2)O core, in accord with the energy-minimized structures obtained from DFT calculations. Cyclic voltammetry studies in CH(2)Cl(2) showed irreversible redox processes, whereas electrolysis coulometry indicated that Cu(II)/Cu(I) complexes could be interconverted. Electrochemistry data of the complexes stress the crucial role of the cage structure of the hemicryptophane in the thermodynamics of the electron transfer.

Designing synthetic receptors that bind biologically relevant guests in an aqueous solution remains a considerable challenge. We now report a new synthetic receptor for nicotine, selected from a dynamic combinatorial library, that binds this guest in water at neutral pH through a combination of hydrophobic and π-π interactions.

Hemicryptophane 3 was found to be an efficient and selective primary alkylammonium receptor. Binding constants are 1000-fold higher than those previously reported for hemicryptophane hosts. Efficient complexation of dopamine emphasizes the use of this host for neurotransmitter complexation. Density functional theory calculations were performed and highlight host-guest complementarities.

Brothers and enemies: Anion-π and cation-π interactions act in a synergistic way when gathered in the molecular cavity of a hemicryptophane host, affording an efficient contribution (-170 kJ mol(-1)) in zwitterion recognition. NMR titration experiments and calculations reveal the positioning of the guest in the cavity of the heteroditopic receptor. This study emphasizes the importance of anion-π bonds in host-guest chemistry., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Hemicryptophanes are host molecules with many applications as supramolecular catalysts or in ion selective recognition. A very convenient and efficient modular approach for the synthesis of hemicryptophane-tren (tren, tris(2-aminoethyl)-amine) derivatives has been developed. For instance, hemicryptophane 1 was synthesized at the gram scale in four steps from vanillyl alcohol compared to the previous seven-step procedure. The size, shape, and functionalities of the molecular cavity were also easily modified., (© 2011 American Chemical Society)

Inherently chiral hemicryptophanes were used to complex β- and α-glucoside derivatives with high diastereo- and enantio-selectivity. In most cases, the exclusive recognition by the M-hemicryptophane enantiomers was observed., (© The Royal Society of Chemistry 2011)

The heteroditopic hemicryptophane 1, which bears a tripodal anion binding site and a cation recognition site in the molecular cavity, proved to be an efficient ion-pair receptor. The hemicryptophane host binds anions selectively depending on shape and hydrogen-bond-accepting ability. It forms an inclusion complex with the Me(4)N(+) ion, which can simultaneously bind anionic species to provide anion@[1⋅Me(4)N(+)] complexes. The increased affinity of [1⋅Me(4)N(+)] for anionic species is attributed to a strong cooperative effect that arises from the properly positioned binding sites in the hemicryptophane cavity, thus allowing the formation of the contact ion pair. Density functional theory calculations were performed to analyze the Coulomb interactions of the ion pairs, which compete with the ion-dipole ones, that originate in the ion-hemicryptophane contacts., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The racemic hemicryptophane molecular cage 2 was resolved by semipreparative HPLC on Whelk-O1 column. The absolute configuration of each isolated enantiomer was established from the analysis of their circular dichroism spectra and assigned as P-(+)-2 and M-(-)-2., (© 2010 Wiley-Liss, Inc.)

The first hemicryptophanes derived from tris(N-alkyl-carbamoylmethyl)amine and tris(2-aminoethyl)amine (tren) have been synthesized following a single synthetic pathway that allows the subsequent formation of the two heteroditopic hosts 3 and 4. X-ray crystal structures show a well-defined cavity encapsulating a solvent guest for both compounds emphasizing their complexation properties.