Enantioselective recognition of carboxylates: a receptor derived from alpha-aminoxy acids functions as a chiral shift reagent for carboxylic acids.

Enantioselective recognition of carboxylates has important implications in asymmetric synthesis and drug discovery. We have prepared a novel C2-symmetric receptor 1 from alpha-aminoxy acids in a high overall yield. A series of chiral recognition studies indicate that receptor 1 not only can bind to carboxylate ions tightly but also has a good ability to recognize enantiomers of a broad variety of carboxylic acids in the 1H NMR spectra. Thus, the receptor 1 can be used as a chiral shift reagent for the determination of enantiomeric purities of chiral carboxylic acids by 1H NMR directly and rapidly.