Unprotected Galactosamine as a Dynamic Key for a Cyclochiral Lock.

The discrimination of d-galactosamine (), representative of the amino-sugar class of compounds, has been probed through nano-ESI-FT-ICR mass spectrometry by isolating the relevant [·H·] proton-bound complexes with the enantiomers of the cyclochiral resorcin[4]arene and allowing them to react toward three primary amines ( = EtNH, PrNH, and ()- and ()-BuNH). The system under investigation presents several features that help to unveil the behavior of unprotected in such a supramolecular architecture: (i) the hydrophobic derivatization of the convex side forces the polar guest to be coordinated by the cyclochiral concave region; (ii) protonated d-galactosamine exists as an anomeric mixture, dynamically interconverting throughout the experimental time-window; and (iii) different basicities of allow the experiment to subtly tune the reactivity of the [·H·] complexes. Three [·H·] aggregate-types were found to exist, differing in both their origin and reactivity.

Cyclochiral resorcin[4]arenes as effective enantioselectors in the gas phase.

The effect of cyclochirality of rccc-2,8,14,20-tetra-n-decyl-4,10,16,22-tetra-O-methylresorcin[4]arene (C) on the enantiodiscrimination of a number of chiral bidentate and tridentate aromatic and aliphatic biomolecules (G) has been investigated by nano-electrospray ionization (nano-ESI)-Fourier transform ion cyclotron resonance mass spectrometry. The experimental approach is based on the formation of diastereomeric proton-bound [C·H·G](+) complexes by nano-ESI of solutions containing an equimolar amount of quasi-enantiomers (C) together with the chiral guest (G) and the subsequent measurement of the rate of the G substitution by the attack of several achiral and chiral amines. In general, the heterochiral complexes react faster than the homochiral ones, except when G is an aminoalcoholic neurotransmitter whose complexes, beyond that, exhibit the highest enantioselectivity.