Breaking the C-3-symmetry of chiral tripodal oxazolines: Enantio-discrimination of chiral organoammonium ions

Abstract

A phenylglycinol-derived tripodal oxazoline with C-1-symmetry (C-1-PhBTO) was synthesized, and its enantioselective recognition behavior toward alpha-chiral primary organoammonium ions was studied. The C-1-PhBTO receptor showed higher selectivity with an opposite sense of enantio-discrimination compared to other C-1-symmetric analogues examined but lower selectivity with the same sense of enantioselection compared to its C-3-symmetric analogue. Binding studies indicated that the Cl-symmetric receptors, particularly C-1-PhBTO, interact with the guests in a 2:1 host-guest complex mode in stark contrast to its C3-symmetric analogues.