FACILE OXIDATIVE DECARBOXYLATION OF 3,4-DIHYDROXYPHENYLACETIC ACID-CATALYZED BY COPPER AND MANGANESE IONS

Under physiological conditions, we observed the rapid, pH- and tempera ture-dependent, oxidative decarboxylation and hydration of 3,4-dihydro xyphenylacetic acid (DOPAC) to form 3,4-dihydroxybenzyl alcohol (DBAlc ). This product was oxidized and underwent tautomerization to form 3,4 -dihydroxybenzaldehyde (DBAld). This reaction did not occur in the pre sence of EDTA, was catalyzed by copper (Cu-I, Cu-II) and manganese (Mn -II) and was oxygen dependent. A variety of mono- and dihydroxyphenyl carboxylic acids were tested and the reaction producing DBAlc as an in termediate was observed to be unique to DOPAC. 3,4-Dihydroxymandelic a cid (DOMA) was rapidly oxidatively decarboxylated to form DBAld direct ly. The substrate and catalyst selectivity of this reaction suggest th at this may have physiological relevance in the neurotoxic consequence s of manganese and copper to the dopaminergic system in man.