Abstract
A facile synthesis of a highly preorganized tripodal enterobactine-type ligand 1a-H3 consisting of a chiral C3-symmetric macrocyclic peptide and three tridentate 2-amido-8-hydroxyquinoline coordinating units is presented. Complex formation with various metal ions (Al3+, Ga3+, Fe3+, La3+ and Eu3+) was investigated by spectrophotometric methods. Only in the case of La3+ and Eu3+ were well defined 1 : 1 complexes formed. On the basis of CD spectroscopy and DFT calculations the configuration at the metal centre of the La3+ complex was determined to show Λ helicity. The coordination compounds [(1a)Ln] presented should be prototypes for further lanthanide(III) complexes with an enterobactine analogue binding situation.
Highlights
The availability of metal ions for biological systems is essential for growth and function
The probably most prominent example of this class is enterobactin (Figure 1) [6,7,8]. It has inspired the synthesis of a wide series of non-natural compounds which are used for metal ion binding and medical purposes [9,10,11,12,13,14,15,16,17,18,19,20,21,22]
We present the synthesis of a novel tripodal ligand, which mimics some features of enterobactin, but in contrast is specific for the binding of high coordinated lanthanide(III) ions
Summary
The availability of metal ions for biological systems is essential for growth and function. A facile synthesis of a highly preorganized tripodal enterobactine-type ligand 1a-H3 consisting of a chiral C3-symmetric macrocyclic peptide and three tridentate 2-amido-8-hydroxyquinoline coordinating units is presented. On the basis of CD spectroscopy and DFT calculations the configuration at the metal centre of the La3+ complex was determined to show Λ helicity.
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