Regio- and Enantioselective Macrocyclization from Dynamic Imine Formation: Chemo- and Enantioselective Fluorescent Recognition of Lysine

The dynamic covalent chemistry of imines is utilized to conduct a regioselective as well as enantioselective synthesis of an unsymmetric (C₁) chiral macrocycle from the reaction of an unsymmetric (C₁) chiral dialdehyde, (S)-4, that contains a salicylaldehyde unit and a benzaldehyde unit, with lysine, an unsymmetric (C₁) chiral diamine. The enantioselectivity is further enhanced in the presence of Zn²⁺. Compound (S)-4 in combination with Zn²⁺ is found to be a highly chemoselective as well as enantioselective fluorescent probe for lysine. It can be used to detect specific enantiomers of this amino acid.