Abstract
A combined strategy utilizing experimental (infrared, nuclear magnetic resonance, circular dichroism, X-ray) and computational (time-dependent density functional theory) techniques is illustrated on tripeptides to investigate their chiroptical properties. Eight stereoisomers of monosubstituted ferrocene, Boc-Pro-Pro-Ala-NHFc, have been prepared and conformationally characterized in depth to reach some guidelines for a future design of ferrocene-based chromophores. The origin of the sign change in circular dichroism spectra near the absorption maximum of a ferrocene chromophore (about 470 nm) is strongly correlated with the sign of the dihedral angle describing deviation of the directly attached amide plane from planarity of the cyclopentadienyl ring. These findings may provide some guidelines for the design of new chiroptical ferrocene-based probes for the assignment of the screw-sense preference of short peptides.
Highlights
Peptidomimetics are a class of foldamers designed to mimic the structure and function of natural peptides and proteins.[1]
Derivatives 1−4 were synthesized using stepwise 1-hydroxybenzotriazole (HOBt)/1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC)-mediated coupling technique starting from Boc-protected aminoferrocene.[27]
To investigate whether the ferrocene chromophore is capable of sensing folded structures in covalently attached tripeptide sequences, we first had to determine the prevailing conformations of 1a−4a in solution
Summary
Peptidomimetics are a class of foldamers designed to mimic the structure and function of natural peptides and proteins.[1]. Even a short helical peptide consisting of four amino acids (achiral Aib, α-aminoisobutyric acid) can be exploited for transduction of information through the membrane.[6]
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