“…In addition to the interaction of H 3 L wa with Ag + , Wipf et al also observed weak interactions between westiellamide and other metal ions such as Na + , Cu + , Fe 2+ , Fe 3+ , Hg 2+ , Au 2+ , and Zn 2+ . 32 Investigations of the interaction of Cu II with H 3 L wa and a series of synthetic analogues H 3 L 1−3 (Figure 1) revealed that after addition of base all cyclic pseudo hexapeptides readily form stable mono-and dinuclear Cu II complexes. 22 In the absence of base, Cu II forms a 2:1 (H 3 L 2 /Cu II ) complex in which Cu II is coordinated to the outside of the macrocycle through the carbonyl oxygen atoms of the peptide bonds, 22 in a similar manner to the central Ag + ion in the unusual [Ag 4 -(H 3 L wa ) 2 ] complex reported by Wipf et al 32 Previous investigations of the Cu II coordination chemistry of the cyclic pseudo hexapeptides H 3 L 1−3 and models for the natural cyclic pseudo peptide westiellamide H 3 L wa revealed interesting differences in their geometric and electronic structures.…”