Synthesis and structural characterization of N-para-ferrocenyl benzoyl amino acid ethyl esters and the X-ray crystal structures of the glycyl and (±)-2-aminobutyric acid derivative Fc-C6H4CONHCH(C2H5)CO2Et

A series of N-para-ferrocenyl benzoyl amino acid ethyl esters 1–8 have been prepared by coupling para-ferrocenyl benzoic acid with the amino acid esters using the conventional 1,3-dicyclohexylcarbodiimide (DCC), 1-hydroxybenzotriazole (HOBt) protocol. The amino acids employed in the synthesis were glycine, l-alanine, l-leucine, l-phenylalanine, β-alanine, 4-aminobutyric acid, (±)-2-aminobutyric acid and 2-aminoisobutyric acid. The compounds were fully characterized by a range of spectroscopic techniques such as NMR and mass spectrometry. In addition the X-ray crystal structures of the glycyl 1 and (±)-2-aminobutyrate 7 derivatives have been determined. Analysis of relevant fragments in crystal structures on the Cambridge Structural Database indicates a relative paucity of common fragments such as the α-aminobutyrate group in comparison to the glycyl moiety.