Discrimination of the Chirality of α-Amino Acids in Zn^II Complexes of DPA-Appended Binaphthyl Imine

Binaphthol aldehydes with appended dipicolylamine moieties, (R)-1, and (R)-2, were synthesized. The reaction of (R)-1 with an amino acid together with the Zn^II ion produces a monomeric complex that discriminates the chirality of the bound amino acid by ¹H NMR spectroscopy. The same reaction of (R)-2, which is different from (R)-1 by only one nitrogen atom, generates a dimeric complex that is highly enantiospecific for the l-form of amino acids such as Phe and Trp.