Oxidative and cardiovascular studies on natural and synthetic catecholamines

The cyclic voltammometric behavior of epinephrine, norepinephrine, dopamine, epinine, alpha-methyldopamine, beta-methyldopamine, beta-methylepinine, and beta-methoxyepinine has been examined in order to evaluate substituent effects on cyclization rates of the electrochemically generated quinones. We observed that alpha and beta substituents caused a modest enhancement of cyclization rates while an N-methyl group dramatically increased cyclization rates. No correlation was observed between calculated amine pKa values, suggesting that differences in cyclization rates between the primary and secondary amine series were due to inherent nucleophilicity, a measure of which would be gas-phase proton affinities. The acute pressor effects of the newly synthesized catecholamines were compared with the native amines.