Notes: 5,6-Dimethylbenzimidazole is a dimethylbenzimidazole that has been found in S. meliloti and is an intermediate in the biosynthesis of the corrin macrocycle vitamin B12 (Item No. 18425).{64933} It is formed from the flavin coenzyme riboflavin 5ʹ-monophosphate (Item No. 18167) by the oxidoreductase BluB in S. meliloti. 5,6-Dimethylbenzimidazole forms the axial region of vitamin B12 and chelates the central cobalt.