Importance of Hydrogen-Bonding Sites in the Chiral Recognition Mechanism Between Racemic D3 Terbium(III) Complexes and Amino Acids

The perturbation of the racemic equilibrium Of luminescent D-3 termbium(III) complexes with chelidamic acid (CDA), a hydroxylated derivative of 2,6-pyridine-dicarboxylic acid (DPA), by added chiral biomolecules such as L-amino acids has been studied using circularly polarized luminescence and C-13 NMR spectroscopy. It is shown in this work that the chiral-induced equilibrium shift of [Tb(CDA)(3)](6-) by L-amino acids (i.e. L-proline or L-arginine) was largely influenced by the hydrogen-bonding networks formed between the ligand interface of racemic [Tb(CDA)(3)](6-) and these added chiral agents. The capping of potential hydrogen-bonding sites by acetylation in 1 proline led to a similar to 100-fold drop in the induced optical activity of the [Tb(CDA)(3)](6-):N-acetyl-L-proline system. This result suggested that the hydrogen-bonding networks serve as the basis for further noncovalent discriminatory interactions between racemic [Tb(CDA)(3)](6-) and added L-amino acids. Chirality 21:497-506, 2009. (C) 2008 Wilev-Uss, Inc.