Hemoprotein Models Based on a Covalent Helix–Heme–Helix Sandwich: 1. Design, Synthesis, and Characterization

In this paper we describe the design, synthesis, and spectroscopic characterization of a covalent helix–heme–helix sandwich named FeIII mimochrome I. It contains deuterohemin bound through both propionyl groups to two identical N‐and C‐terminal protected nonapeptides as α‐helical scaffolds. Each peptide moiety bears a His residue in the central position, which acts as axial ligand to the metal ion. The newly developed synthetic strategy is based on a combination of solution and solid‐phase methodologies. It represents a powerful method for obtaining a large variety of analogues containing two symmetric or unsymmetric peptide chains covalently bound to the deuteroporphyrin ring. UV/Visible spectroscopic characterization in buffered 2,2,2‐trifluoroethanol/water solution proves low‐spin bis(his‐tidine) iron(III) coordination; circular dichroism (CD) measurements show an α‐helical conformation for the peptide moieties. Thus, all the data are in agreement with the designed hypothetical model regarding both the iron(III) coordination and the peptide chain structural organization.