engleski

Bis- and Trisamides Derived From 1′ -Aminoferrocene-1-carboxylic Acid and α -Amino Acids: Synthesis and Conformational Analysis

Ferrocene derivatives with one or two chiral arms based on  -amino acids (Gly, Ala, Val) attached to the cyclopentadienyl rings were prepared by solution-phase peptide synthesis from N-acetyl- and N-Boc-protected 1’ -aminoferrocene-1-carboxylic acids (Fca). The conformational preferences in the solid state of selected examples were elucidated by X-ray crystallography. The chiroptical properties of the chiral di- and tripeptides were investigated by CD spectroscopy in solution. The conformational preferences were studied by NMR and IR spectroscopy, as well as by molecular modelling (DFT). For dipeptides a conformational library is observed in solution. Increasing the steric bulk of the amino acid side chain disfavours several energetically accessible conformers of dipeptides and specific conformers can be selected by changing the environment (type of solvent ; solid/solution). For the tripeptides a single conformer is highly stabilized by two intramolecular hydrogen bonds irrespective of the size of the protecting group, the size of the amino acid side chain and the medium.

rerrocene; amino acids; pptides; bioorganometallic chemistry; conformational analysis

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