Synthesis of organometallic amines and their coupling to the C-terminus of amino acids and peptides

Abstract

Abstract This work describes the use of organometallic amines for the labelling of the C-terminus of amino acids and peptides. N-substituted ferrocene-methylamines 2 could be readily prepared and coupled to a variety of amino acids in good yield. The novel ferrocene amino acid derivatives 4 exist in two conformations in solution, which differ in the orientation of the tertiary amide bond and interconvert slowly in solution. For the glycine derivative 4a the activation energy was determined to be 70.3 kJ mol−1 by 1H-NMR spectroscopy. All new compounds were completely characterised spectroscopically including 15N-NMR by indirect detection 2D 1H-15N-NMR. The potential difference of ca. +50 mV between ferrocene derivatives 2 and the ferrocenyl amino acids 4 in cyclic voltammetry was used to monitor the peptide coupling reaction in situ. Also described are attempts towards the synthesis of organometallic amine derivatives of benzene chromium tricarbonyl and η-cyclopentadienyl molybdenum dicarbonyl. The solid state structures of CpMo(CO)2C2H4N(CO)2C6H4 14 and CpFeC5H4CH2NHCH2-p-CH3C6H4 2a (Cp: η-cyclopentadienyl) were determined by single-crystal X-ray diffraction.