N-Hydroxy Amides. X. Synthesis of a Nonapeptide with an Ala-(HO)Gly-Ala Sequence and Its Spectral and Iron(III) Holding Properties

A nonapeptide with an Ala–(HO)Gly–Ala sequence has been synthesized via condensation of appropriately protected tripeptide units. 1H NMR and CD spectral data indicate that the nonapeptide has a disordered structure in DMSO and water. The peptide forms a 1 : 3 complex of iron(III) with hydroxamate groups at neutral pH when mixed with an aqueous iron(III) solution. The complex shows λmax at 410 nm with an e of 2160 at pH 7. Alanine residues influence the hydroxamate groups to produce a chiral complex, the CD spectrum of which reveals bands at 355 nm (Δe+0.8) and 435 nm (Δe−1.8), showing a preference for the Δ-configuration around the iron.