title: [Deamination and reductive deamination of (2-amino-5, 6-dimethylbenzimidazolyl)cobamide. Preparation of (2-hydroxy-5, 6-dimethylbenzimidazolyl)cobamide and (5, 6-dimethyl-[2(-14)C]-benzimidazolyl)cobamide].
abstract: (2-Amino-5, 6-dimethylbenzimidazolyl)-cobamide (III) is transformed to (2-hydroxy-5, 6-dimethylbenzimidazolyl) cobamide (IV) by nitrous acid. Exchange of the NH2-group by hydrogen with nitrous acid/hypophosphorous acid yields vitamin B12 (I). This reaction completes a cycle vitamin B12 (I)----[carboxy(2-cyanoamino-4,5-dimethylphenyl)amino]cobamide+ ++ (II)----(2-amino-5,6-dimethylbenzimidazolyl)cobamide (III)----vitamin B12 (I), which allows chemical 14C-labelling of vitamin B12. In this procedure cyanogen bromide, which is necessary for the first step, was labelled with [14C] cyanide. By the following reactions a vitamin B12 was formed in which C-2 of the 5, 6-dimethylbenzimidazole moiety is labelled.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D003038:Cobamides / Q000138:chemical synthesis* / Q000378:metabolism; D003641:Deamination; D010084:Oxidation-Reduction; D011424:Propionibacterium / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D014805:Vitamin B 12 / Q000096:biosynthesis
chemical_list: D003038:Cobamides; C017142:cobinamide; C041074:(2-hydroxy-5,6-dimethylbenzimidazolyl)cobamide; C041073:(2-amino-5,6-dimethylbenzimidazolyl)cobamide; D014805:Vitamin B 12
vernacular_title: Desaminierung und reduktive Desaminierung von (2-Amino-5, 6-dimethylbenzimidazolyl)cobamid. Darstellung von (2-Hydroxy-5 6-dimethylbenzimidazolyl)cobamid und (5, 6-Dimethyl-[2(-14)C] benzimidazolyl)cobamid.