Reactions of Co(III)-coordinated Ornithine: Towards Inhibitors of the Polyamine Biosynthetic Pathway

Abstract

Treatment of the complex Δ,Λ-[Co(en)2(S-ornithineH-κ2N,O)](CF3SO3)3 with SOCl2 in DMF gives a mixture of the expected imino complex [Co(en)2(2-iminoornithineH-κ2N,O)]3+ and the amidine complex [Co(en)2(5-{[(1E)-(dimethylamino)methylene]amino}-2-iminopentanoate-κ2N,O)]3+, which is proposed to result from the reaction of the Vilsmeier reagent [ClCH=N(CH3)2]+ with the terminal amine of coordinated ornithine. Treatment of the imino complex with nitromethane in alkaline solution gives the complex [Co(en)2(2-nitromethylornithineH-κ2N,O)]3+, which contains the potential suicide inhibitor 2-nitromethylornithine. X-ray crystal structures of Δ-[Co(en)2(S-ornithineH-κ2N,O)]Br3 and Δ,Λ-[Co(en)2(5-{[(1E)-(dimethylamino)methylene]amino}-2-iminopentanoate-κ2N,O)](ClO4)3 are reported.