Enantioselective Recognition of Carboxylates:A Receptor Derived from alpha-Aminoxy Acids Functions as a Chiral Shift Reagent for Carboxylic Acids

摘要

The carboxylate group is an anionic entity of prime importance in nature.Enzymes,antibodies,amino acids,and metabolic intermediates,as well as the other natural products,contain a range of carboxylate functionalities that account for the characteristic biochemical behavior.Enantioselective recognition of carboxylates has important implications in asymmetric synthesis and drug discovery.Although many enantioselective carboxylate receptors have shown their application in chiral resolution,few such receptors can be used as chiral shift reagents to determine enantiomeric purities of chiral carboxylic acids by ~1H NMR accurately because of either their structural complexity or their ~H chemical shift nonequivalences that are too small to realize baseline resolution.