PUB - Publikationen an der Universität Bielefeld

The gas-phase enantioselectivity of cone N-linked peptidoresorc[4]arenes (generally symbolized as M) toward the homologue dipeptides (generally symbolized as A) has been evaluated by measuring the kinetics of the A release from the diastereomeric [M center dot H center dot A](+) complexes induced by (R)-(-)-2-butylamine (B). In most cases investigated, the heterochiral [M center dot H center dot A](+) complexes, namely those wherein the configuration of the A guest is opposite to that or the host M pendants, react faster (up to 5 times) than the homochiral analogues, wherein guest A guest has the same Configuration of the host M pendants. The kinetic results, discussed in the light of previous MS and NMR evidence, indicate that both the efficiency and the enantioselectivity of the guest exchange reaction depend essentially on the Structure and the relative stability of the diastereomeric [M center dot H center dot A](+) complexes. These, in turn, depend oil the functional groups and the configuration of both the guest and the host pendants. The absence of any significant effects of the B configuration indicates that, in all systems investigated, the dipeptide guest A is predominantly located outside the host chiral cavity.