Formation of N-(1-ferrocenoylpyrrolidine-2-carbonyl)-N,N′-dicyclohexylurea: Dead-end in the preparation of ferrocene-modified peptides

This paper reports the synthesis, characterisation and electrochemical properties of Fc-Pro-DCU 3. The activation of Fc-Pro-OH with DCC in the absence of racemization reducing agent results in the formation of N-(1-ferrocenoylpyrrolidine-2-carbonyl)-N,N′-dicyclohexylurea, as result of O/N-acyl shift in the acylisourea intermediate. Compound 3 exhibits quasi-reversible one-electron oxidation of ferrocenoyl moiety at E1/2 = 0.62 V.