On the research avenue opened by the rigidified double‐spanned resorcin[4]arene 1, we have synthesized both enantiomers of the two chiral basket resorcin[4]arenes 3 and 4, each containing two 1,2‐diaminocyclohexane and 1,2‐diphenylethylenediamine bridges, respectively. In the new compounds, the aromatic rims assume the expected flattened cone arrangement, whereas two different conformations, tentatively designated as “open wings” and “folded wings”, were attributed to the bridge substituents according to molecular modeling studies. In MSn (ESI) experiments, the proton‐bonded diastereomeric [4·H·A]+ complexes with amino acidic guests (A) exhibited a pronounced selectivity towards the enantiomers of tyrosine methyl ester (tyrOMe) and amphetamine (amph), whereas the chirality of tryptophan (trp) was ineffective. Moreover, a kinetic study on the base‐induced displacement of the guest revealed that the L‐tyrOMe (and L‐amph) enantiomer is faster displaced from the heterochiral [4·H·L‐tyrOMe]+ (or [ent‐4·H·l‐amph]+) complex than from the homochiral [ent‐4·H·L‐tyrOMe]+ (or [4·H·l‐amph]+) one. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The stereoselectivity of the reaction between (R)-(-)-2-butylamine and the diastereomeric proton-bound complexes of (+)-catharanthine (C) or (-)-vindoline (V) with some chiral amido[4]resorcinarenes has been investigated in the gas phase by ESI-FT-ICR-MS. The reaction stereoselectivity (0.56 < k(homo)/k(hetero) < 16.9) is found to depend critically on the functional groups present in the chiral pendants of the hosts. Rationalisation of the kinetic results is based on careful computational and spectroscopic studies of the most stable conformations of (+)-catharanthine and its protonated form in the isolated state and in water, as well as in a representative host structure. The emerging picture points to the relevant diastereomeric proton-bound complexes as quasi-degenerate, thus suggesting that their stereoselectivity in the guest exchange reaction is mostly due to kinetic factors. The results of this study may represent a starting point for a deeper comprehension of the intrinsic factors that endow these molecules, and their dimeric forms, with their biochemical properties.

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Bis(diamido)-bridged basket resorcin[4]arene (all-S)-1 and its (all-R)-1 enantiomer proved able to interact with 2'-deoxycytidine (2) and pyrimidine nucleoside analogs in dimethyl sulfoxide (DMSO) solution. In such a solvent, the resorcinarene hosts adopt a preferential 1,3-alternate-like conformation, with a larger cavity delimited by two syn 3,5-dimethoxyphenyl moieties, and two external pockets, each delimited by the other 3,5-dimethoxyphenyl group and its diamido arm (the wing). Complexation phenomena were investigated by nuclear magnetic resonance (NMR) methods, including (1)H NMR DOSY and 1D ROESY experiments, and molecular modeling. Heteroassociation constants of [(all-S)-1·2] and [(all-R)-1·2] diastereoisomeric complexes were obtained from diffusion data by single point measurements, and from nonlinear fitting of 1H NMR chemical shifts. Selective proton relaxation rate measurements allowed us to significantly discriminate the two complexes by identifying two different interaction sites of the guest in the resorcin[4]arene host, depending on its configuration.

The gas-phase encounters between 2-aminobutane and proton-bound chiral resorcin[4]arene/nucleoside complexes behave in the gas phase as supramolecular "chiroselective logic gates" by releasing the nucleoside depending on the resorcin[4]arene and the 2-aminobutane configurations.