Direct Observation of Radical Intermediates While Investigating the Redox Behavior of Thiamin Coenzyme Models

The redox behavior of “active aldehydes” 1 ^? derived from 3-benzylthiazolium salts and simple aldehydes in the presence of a base has been examined with low-temperature cyclic voltammetry and EPR spectroscopy. The highly negative oxidation potentials of 1 ^? and the spin distribution of the intermediate radicals 1 ^. indicate that the active aldehyde can act as an efficient electron mediator in thiamin-dependent enzymatic redox systems.