[Coalpha/Cobeta-isomerism of corrinoids. Partial synthesis and Escherichia coli activity of further isomer pairs of the (Co-methyl)-corrinoids (author's transl)].

In 2-methyladenyl-(Cobeta-methyl)-cobamide and in adenyl-(cobeta-methyl)-cobamide the nucleotide base is coordinated to the cobalt atom in neutral and weak acidic aqueous solutions (in the corresponding adenosylcorrinoids the nucleotide base is not coordinated). 2-Methylthioadenyl-(Cobeta-methyl)-cobamide resembles, with regard to the coordination of the nucleotide base, the benzimidazole-corrinoids. The partial synthesis via cobalt (I) corrinoids results in a variable proportion: (Coalpha-methyl) isomer/(Cobeta-methyl) isomer, e. g. 7/93 (cobalamin) and 50/50 (p-cresylcobamide). This proportion is generally low, if in the corresponding cyanocorrinoid the nucleotide base is firmly coordinated; it is high, if the coordination in the corresponding cyanocorrinoid is weak or absent. These results are compatible with the assumption that in the cobalt (I) corrinoids the nucleotide base is to a certain extent coordinated. In Escherichia coli 113-3 the examined (Coalpha-methyl)-corrinoids show a weaker bioactivity than the corresponding (Cobeta-methyl)-corrinoids.