Metallo-carbonyl conjugates of biotin and biocytin

Coupling of biotin with CpFe(CO)2(η1-N(1)-4-aminosulfonamido) (1a) and CpFe(CO)(P(OMe)3) (η1-N(1)-4-aminosulfonamide) (1b) afforded corresponding metallo-carbonyl biotin amides 2a–b. Reaction of Nε-biotinyl-l-lysine (biocytin) with CpFe(CO)2(η1-N-3-isothiocyanatophtalimidato) (4a), CpFe(CO)2(η1-N-4-isothiocyanatophtalimidato) (4b), CpFe(CO)2(η1-N(1)-4-isothiocyanatosulfonamido) (5, this compound was prepared from 1a and thiophosgene and its structure confirmed by spectral data and by the X-ray diffraction method) gave bioconjugates 6a–c. The HABA-avidin test revealed high affinities of all synthesised bioconjugates to avidin.