engleski

Central-to-Helical-to-Axial Chirality Transfer in Chiroptical Sensing with Ferrocene Chromophore

The effect of attaching the achiral, cyclic 1- aminocyclohexanecarboxylic acid (Ac6c) directly to the aminoferrocene unit (Ac6c−NH−Fc) appears to be a promising route for the development of a new chiroptical sensor based on a ferrocene chromophore. Three new compounds (Boc−AA−Ac6c−NH−Fc ; AA = L-Ala, L-Val, L-Phe) were synthesized, spectroscopically characterized (IR, NMR, CD), and conformationally analyzed (DFT). The chiral information was transferred from the L- amino acid to the ferrocene chromophore by the predominant formation of P-helical struc-tures with ten-membered hydrogen-bonded rings (β-turns). The perturbation of the ferrocene chromophore and the appearance of the negative CD signal near 470 nm originates from a relative orientation of the directly linked amide and cyclopentadienyl planes, described by the dihedral angle χ. The sterically demanding Ac6c amino acid makes trans-like configurations more favorable and thus restricts the dihedral angle χ, which then leads to the appearance of the negative peak near 470 nm in the CD curve.

circular dichroism (CD) ; Density functional theory (DFT) ; Conformational analysis ; Ferrocene peptides ; Chirality

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