engleski

1'-Acetylferrocene Amino Acid Esters and Amides. A simple model for parallel beta-helical peptides

In this study we present a synthesis and conformational analysis of 1’-acetylferrocene amino acid derivatives of type Ac-Fn-CO-AA-Y (Fn = ferrocene-1, 1-diyl ; AA = Gly, Ala or Val ; Y = OMe or NHMe) as a model for parallel beta-helical peptides. Derivatives with only one amino acid instead of a dipeptide adopt a reduced number of total conformations and allow a more exact analysis of intramolecular hydrogen bonds (IHB) close to the ferrocene unit. Conformational analysis of these bioconjugates was performed by a combination of spectroscopic techniques (IR, NMR and CD) and corroborated by solution-phase DFT calculations. The investigation of ester conjugates 1-3 indicates the coexistence of non- bonded (in open forms) and hydrogen bonded NHa group forming a 7-membered ring (γ-turn). The amide derivatives 4-6 with an additional NHb hydrogen bond donor are mostly constituted of conformers with a 10-membered ring (-turn). This is usually accompanied by a 7-membered ring (γ- ring) containing NHa group or by a single IHB pattern. Additionally, the exchange of the amino acid side-chain does not significantly affect the conformational properties and IHB patterns of the studied conjugates 1-6.

ferrocene; bioconjugates; conformational analysis; hydrogen bonds; density functional theory (DFT)

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