Abstract
This study describes the syntheses of four singly- and two doubly-modified vitamin B12 derivatives for generating antimetabolites of Lactobacillus delbrueckii (L. delbrueckii). The two most potent antagonists, a Coβ-phenyl-cobalamin-c,8-lactam and a 10-bromo-Coβ-phenylcobalamin combine a c-lactam or 10-bromo modification at the "eastern" site of the corrin ring with an artificial organometallic phenyl group instead of a cyano ligand at the β-site of the cobalt center. These two doubly-modified B12 antagonists (10 nM) inhibit fully B12-dependent (0.1 nM) growth of L. delbrueckii. In contrast to potent 10-bromo-Coβ-phenylcobalamin, single modified 10-bromo-Coβ-cyanocobalamin lacking the artificial organometallic phenyl ligand does not show any inhibitory effect. These results suggest, that the organometallic β-phenyl ligand at the Co center ultimately steers the metabolic effect of the 10-bromo-analogue.