A series of N-meta-ferrocenyl benzoyl amino acid esters 3-10 have been prepared by coupling meta-ferrocenyl benzoic acid 2 to 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, b-alanine, 4-aminobutyric acid, 2-aminobutyric acid and 2-aminoisobutyric acid. The compounds were fully characterized by a range of NMR spectroscopic techniques and mass spectrometry (MALDI-MS, ESI-MS).The organometallic compound ferrocene is a promising candidate for incorporation in novel materials due to its stability, spectroscopic properties, electrochemical properties and ease of use. As a direct consequence of these factors, research in the area of ferrocenyl derivatives has seen a dramatic increase in attention over the past decade, primarily for the ultimate goals of achieving novel sensor compounds, peptide mimetic models and unnatural drugs [1][2][3][4][5][6][7][8][9][10]. The incorporation of a ferrocene group onto proteins has shown the mediation of electron transfer between electrodes and the protein redox site [3,5]. The synthesis and structural characterization of novel N-ferrocenoyl and N-ferrocenyl amino acid and peptide derivatives has been reported [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. The aim of this research is to incorporate three key moieties in the synthesis of unusual biological materials, namely (i) an electroactive core, (ii) a conjugated linker that can act as a chromophore and (iii) an amino acid derivative that can interact with other molecules via hydrogen bonding. In this communication, we report the synthesis and structural characterization of a series of novel Nmeta-ferrocenyl benzoyl amino acid ester derivatives. We recently reported the synthesis and structural characterization of a series of N-para-ferrocenyl benzoyl amino acid ester derivatives [28] and the N-ortho-ferrocenyl benzoyl amino acid derivatives will be reported in due course.The meta-ferrocenyl benzoic acid 2 was prepared using conventional diazonium salt chemistry. Treatment of ethyl-3-aminobenzoate with sodium nitrite in the presence of hydrochloric acid yielded the diazonium salt, which was then reacted with ferrocene in situ to yield the meta-substituted ferrocenyl ethyl benzoate 1. The ester group was cleanly cleaved by treatment with 10% sodium hydroxide to yield meta-ferrocenyl benzoic acid 2. The 1 H NMR spectrum showed signals for the aromatic ring protons at d 8.03 (s), d 7.8 (d), d 7.77 (d) and d 7.43 (t), integrating for one proton each, characteristic of a meta-disubstituted aromatic ring. The 1387-7003/$ -see front matter Ó (P.T.M. Kenny). www.elsevier.com/locate/inoche Inorganic Chemistry Communications 8 (2005) 429-432carboxylic acid proton was present at d 13.2. The ferrocenyl ortho and meta protons on the (g 5 -C 5 H 4 ) ring were observed at d 4.84 and d 4.39, respectively, and an intense singlet was present at d 4.03 for ...
