Hydrogenobinamide and Nibinamide – Metal-Free Ligand and Ni(II)-Analogue of the Vitamin B12 Precursor Cobinamide

Kieninger C, Deery E, Lawrence AD, Warren MJ, Krautler . (2023)

Journal of Porphyrins and Phthalocyanines

The replacement of cobalt in vitamin B1?2 derivatives by other transition metals is a formal path to non-natural corrins. Here, we describe nibinamide (Nibi), the novel Ni(II)-analogue of the natural B1?2-derivative cobinamide (Cbi), and its synthesis from the metal-free ligand of Cbi, hydrogenobinamide (Hbi), both isolated as tetrafluoroborate salts. Aqueous solutions of the metal-free corrin Hbi are strongly fluorescent, whereas its Ni(II)-complex Nibi is non-luminescent. The solution structures of Hbi and of Nibi were characterized by hetero-nuclear NMR-spectroscopy. The Ni(II)-corrin Nibi was deduced to be roughly iso-structural to cob(I)inamide (Cbi??) and to house a diamagnetic d⁸-metal-ioniso-electronic to Co?? in Cbi??. The chemically robust Nibi is, thus, a structural mimic of enzyme-activated and reduced biosynthetic precursors of vitamin B1?2 and a B1?2-antimetabolite potentially functioning as a specific inhibitor of B1?2-biosynthesis.

Journal of Porphyrins and Phthalocyanines

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