engleski

Conformational analysis of heteroannularly substituted ferrocene oligoamides

The main conformer of symmetrical conjugates of ferrocene-1, 1’ -dicarboxylic acid with natural amino acids – Fn(CO-AA1-2-OMe)2 (type I, Fn = ferrocene-1, 1'-diyl, AA = L-alpha-amino acid) is supported by two hydrogen bonds between the podand peptide chains. In order to compare intramolecular hydrogen bond patterns of type I conjugates with related asymmetrically substituted derivatives type II (MeNHCO-Fn-CO-AA-OMe) and type III conjugates (MeNHCO-Fn-CO-AA-NHMe) were prepared in moderate to good yields in a few steps starting from 1’ -(methoxycarbonyl)ferrocene-1-carboxylic acid using the HOBt/EDC method (AA = Gly, Ala, Val). 1H NMR variation ratio analysis suggests that increasing the steric demand of the amino acid side chains favours conformations with hydrogen-bonded FnCONHMe groups. CD spectroscopy of chiral derivatives reveals that (P)-helical conformations predominate in solution. All the experimental findings are in accordance with DFT calculations.

Conformation analysis; Density functional calculations; Hydrogen bonds; Metallocenes; Molecular modelling

nije evidentirano