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.