Vitamin B12 model studies. Acrylate migration in the model carbon-skeleton rearrangement leading to α-methyleneglutaric acid
Abstract
Rearrangement of the model vitamin B12–methylitaconate adduct (IV) in D2O leads to the uptake of one deuterium in each of two of the products: methylitaconic acid (I) and α-methyleneglutaric acid (II). The third product, butadiene-2,3-dicarboxylic acid (V), contained no deuterium. The deuterium in the methylitaconic acid [2H]-(I) was incorporated in the methyl group. The deuterium in the α-methyleneglutaric acid [2H]-(II) was located at the γ-carbon. The latter result demonstrates that the migrating group in the rearrangement is the acrylate group, as it is in the corresponding coenzyme B12-dependent, enzyme-catalysed, carbon-skeleton rearrangement of methylitaconic acid (I) to α-methyleneglutaric acid (IV). The labelling result establishes a firm connection between the model and the enzyme-catalysed reactions.