Partial Synthesis of CoαCoβ-Dicyano-176-Norcobinamide

Recent interest in norvitamin B₁₂-derivatives, homologues of complete vitamin B₁₂-derivatives, lacking the methyl group at carbon 176, stems from the identification of the corrinoid cofactor of the tetrachloroethene reductive dehalogenase of Sulfurospirillum multivorans as 176-nor-pseudovitamin B₁₂. Here we report the partial synthesis of the corrinoid Co_αCo_β-dicyano-176-norcobinamide by condensation of cobyric acid and 2-aminoethanol. In addition, the partial synthesis of crystalline Co_α-aquo-Co_β-cyanocobyric acid by acid catalyzed hydrolysis of vitamin B₁₂ is detailed, improving the method and the isolation procedure worked out earlier by Bernhauer et al. The solution structure of Co_αCo_β-dicyano-176-norcobinamide was studied by spectroscopy and was compared with that of the homologue Co_αCo_β-dicyanocobinamide. The title compound, Co_αCo_β-dicyano-176-norcobinamide, represents the dicyano-form of a potential biosynthetic precursor of the 176-nor-B₁₂-derivatives, such as 176-nor-pseudovitamin B₁₂.