Synthesis and structural characterization of metallated bioconjugates: C-terminal labeling of amino acids with aminoferrocene

Aminoferrocene, H2N–Fc, has been substituted to the C-terminus of six amino acids using the HBTU/HOBt coupling protocol. The synthesized bioconjugates Boc-Aaa-NH-Fc, Aaa = Gly (1), Leu (2), Phe (3), Val (4), Cys(Acm) (5), Tyr(tBu) (6) (Acm = acetamidomethyl, tBu = tert-butyl), have been characterized by 1H NMR, 13C NMR, EI-MS, EI-HRMS, UV and CD spectroscopies. In addition, a VT NMR study on 4 and the X-ray structure of 1 are presented.