Cyclopentadienyl iron dicarbonyl (eta 1-N-phthalimidato) complexes containing an isothiocyanate function: synthesis and application to protein side-chain selective labeling.

The two first transition metal carbonyl isothiocyanates were prepared in high yield within two steps from photolysis of CpFe(CO)2I and 3- or 4-aminophthalimide in the presence of diisopropylamine followed by reaction with thiophosgene/triethylamine. Their reaction with a model amino acid, i.e. beta-alanine, was performed and led to the expected thioureas. When reacted with bovine serum albumin in aqueous medium, conjugates bearing 6-10 iron-carbonyl fragments were obtained and characterized by Fourier transform infrared spectroscopy, thus demonstrating the usefulness of these reagents for the selective and covalent labeling of proteins.