Breaking the C3-symmetry of chiral tripodal oxazolines: enantio-discrimination of chiral organoammonium ions

J Org Chem. 2005 Sep 2;70(18):7227-31. doi: 10.1021/jo050872p.

Abstract

[structure: see text] A phenylglycinol-derived tripodal oxazoline with C1-symmetry (C1-PhBTO) was synthesized, and its enantioselective recognition behavior toward alpha-chiral primary organoammonium ions was studied. The C1-PhBTO receptor showed higher selectivity with an opposite sense of enantio-discrimination compared to other C1-symmetric analogues examined but lower selectivity with the same sense of enantioselection compared to its C3-symmetric analogue. Binding studies indicated that the C1-symmetric receptors, particularly C1-PhBTO, interact with the guests in a 2:1 host-guest complex mode in stark contrast to its C3-symmetric analogues.