Hydrogen Bond Patterning and Biological Activity of Ferrocene Conjugates with Homo- and Heterochiral Ala–Pro Dipeptides

The chirality of the protein backbone influences both self-assembly and biological activity. In ferrocene-containing peptides, the sequence and chirality of the constitutive amino acids as well as the structure of the ferrocene scaffold strongly influence the conformational properties, whereas the biological activity is more strongly influenced by lipophilicity. A joint spectroscopic and computational study has shown that a relatively simple structural modification, such as changing the order of two amino acids in the dipeptide sequence from Pro–Ala (III) to Ala–Pro (IV), also alters the hydrogen bonding patterns from a mostly ten-membered (β-turn) to a seven-membered ring (γ-turn), which affects the antiproliferative activity of the ferrocene peptidomimetics studied. A systematic approach presented in this study allowed us to highlight the relevant structural variations that could lead to increased biological activity in similar ferrocene-based bioconjugates.