Modelling amphetamine/receptor interactions: A gas-phase study of complexes formed between amphetamine and some chiral amido[4]resorcinarenes

Diastereomeric protonbound complexes formed between (R)- and (S)-amphetamine and some chiral amido[4]resorcinarene receptors display significant enantioselectivities when reacting with the enantiomers of 2-aminobutane in the gas phase. The origins of the measured enantioselectivities are discussed in the light of molecular mechanics calculations and molecular dynamics simulations and are ascribed to a combination of structural and dynamic factors, including the lengths and the isomeric structures of the host asymmetric pendants and the frequencies and amplitudes of their motion, as well as those of the protonbonded amphetamine guests. The emerging picture may represent a starting point for deeper comprehension of the factors determining the different affinities of (R)- and (S)-amphetamine towards various chiral receptors, their selective binding to the monoamine transporters, and their sensitivity to specific inorganic ions.