Formation of the dimethylbenzimidazole ligand of coenzyme B(12) under physiological conditions by a facile oxidative cascade.

Dimethylbezimidazole, the axial ligand of vitamin B(12), is synthesized from riboflavin by a two-electron oxidation, a retro-aldol condensation, and a second two-electron oxidation. This oxidative cascade readily takes place nonenzymatically under physiological conditions. [reaction: see text]