Helical Chirality Induction in Zinc Bilindiones by Amino Acid Esters and Amines
摘要:
Complexation of alpha-amino acid esters, beta-amino ethers, and amines with a series of zinc 1,19-bilindione derivatives was studied, particularly focusing on the helical chirality induction in the bilindione framework triggered by the binding of chiral guests. Comparative studies of binding and helical chirality induction indicated that binding and chiral induction were markedly affected by polar substituents present in both zinc bilindiones and guests. 2-Hydroxyethyl groups at the 2,18-positions of zinc bilindione largely assisted the binding of amines and amino acid esters but not the chiral induction. 19O-Alkylation of the zinc bilindiones had inhibitory effects on the binding but enhanced efficiency of helical chirality induction. The enantiomeric excess of 19O-alkyl zinc bilindione complexed with L-Trp-OMe in CD2Cl2 was 73% at 223 K. A COOR group and an aromatic group in the guest promoted helical chirality induction of 19O-alkylated zinc bilindiones. The patterns of H-1 NMR complexation-induced shifts of zinc bilindiones and guests and a molecular modeling study of the complexes showed that electrostatic repulsion between the COOR group of amino acid esters and the lactam ring of zinc bilindiones, and stacking of the side chain groups of amino acid esters on the C ring of zinc bilindione made a significant contribution to efficient helical chirality induction.
Helical Chirality Induction in Zinc Bilindiones by Amino Acid Esters and Amines
摘要:
Complexation of alpha-amino acid esters, beta-amino ethers, and amines with a series of zinc 1,19-bilindione derivatives was studied, particularly focusing on the helical chirality induction in the bilindione framework triggered by the binding of chiral guests. Comparative studies of binding and helical chirality induction indicated that binding and chiral induction were markedly affected by polar substituents present in both zinc bilindiones and guests. 2-Hydroxyethyl groups at the 2,18-positions of zinc bilindione largely assisted the binding of amines and amino acid esters but not the chiral induction. 19O-Alkylation of the zinc bilindiones had inhibitory effects on the binding but enhanced efficiency of helical chirality induction. The enantiomeric excess of 19O-alkyl zinc bilindione complexed with L-Trp-OMe in CD2Cl2 was 73% at 223 K. A COOR group and an aromatic group in the guest promoted helical chirality induction of 19O-alkylated zinc bilindiones. The patterns of H-1 NMR complexation-induced shifts of zinc bilindiones and guests and a molecular modeling study of the complexes showed that electrostatic repulsion between the COOR group of amino acid esters and the lactam ring of zinc bilindiones, and stacking of the side chain groups of amino acid esters on the C ring of zinc bilindione made a significant contribution to efficient helical chirality induction.
Complexation of alpha-amino acid esters, beta-amino ethers, and amines with a series of zinc 1,19-bilindione derivatives was studied, particularly focusing on the helical chirality induction in the bilindione framework triggered by the binding of chiral guests. Comparative studies of binding and helical chirality induction indicated that binding and chiral induction were markedly affected by polar substituents present in both zinc bilindiones and guests. 2-Hydroxyethyl groups at the 2,18-positions of zinc bilindione largely assisted the binding of amines and amino acid esters but not the chiral induction. 19O-Alkylation of the zinc bilindiones had inhibitory effects on the binding but enhanced efficiency of helical chirality induction. The enantiomeric excess of 19O-alkyl zinc bilindione complexed with L-Trp-OMe in CD2Cl2 was 73% at 223 K. A COOR group and an aromatic group in the guest promoted helical chirality induction of 19O-alkylated zinc bilindiones. The patterns of H-1 NMR complexation-induced shifts of zinc bilindiones and guests and a molecular modeling study of the complexes showed that electrostatic repulsion between the COOR group of amino acid esters and the lactam ring of zinc bilindiones, and stacking of the side chain groups of amino acid esters on the C ring of zinc bilindione made a significant contribution to efficient helical chirality induction.