Coa/Coß-Isom erie der Corrinoide. Partialsynthese und Escherichia coli -Aktivität weiterer Isomerenpaare der (Co-M ethyl)-corrinoide Coa/Co/Msomerism of Corrinoids. Partial Synthesis and Escherichia coli Activity of Further Isomer Pairs o f the (Co-methyl)-Corrinoids

Abstract

Vitamin B 12 , Methylcorrinoids, Coα/Coβ-isomerism, E. coli Activity In 2-methyladenyl-(Coβ-methyI) -cobamide and in adenyl-(Coβ-methyl)-cobamide the nucleotide base is coordinated to the cobalt atom in neutral and weak acidic aqueous solutions (in the cor­ responding adenosylcorrinoids the nucleotide base is not coordinated). 2-Methylthioadenyl-(Coβ-methyl)-cobamide resembles, with regard to the coordination of the nucleotide base, the benz-imidazole-corrinoids.

The partial synthesis via cobalt (I) corrinoids results in a variable proportion: (Coα-methyl) iso­ mer/(Coβ-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 (Coα-methyl)-corrinoids show a weaker bioactivity than the corresponding (Coβ-methyl) -corrinoids.