Main Chain Ferrocenyl Amides from 1‐Aminoferrocene‐1′‐carboxylic Acid

The non‐natural amino acid 1‐aminoferrocene‐1′‐carboxylic acid is synthesised from ferrocene in eight steps. The folding and association phenomena of amido‐substituted ferrocenes in the crystal as well as in solution are studied by X‐ray crystallography, IR and NMR spectroscopy and DFT calculations. The amino acid is selectively protected at the amino group with the use of the fluorenyl‐9‐methoxycarbonyl (Fmoc) group. An amide‐linked ferrocene dimer is prepared using the HOBt/DCC protocol for amide formation. In the crystal the dimer forms a hydrogen‐bonded sheet structure, while in solution dynamic intramolecular hydrogen bonds are observed by VT 1H NMR and IR spectroscopy. The dynamic flipping process has been rationalised by DFT calculations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)