The electrochemical and peroxidase-catalyzed redox chemistry of 9-β-D-ribofuranosyluric acid

Abstract

The electrochemical oxidation of 9-β-D-ribofuranosyluric acid (I) at a pyrolytic graphite electrode proceeds via an initial 2 e reaction to give an unstable quinonoid intermediate. Nucleophilic attack by water on this intermediate leads to isomeric tertiary alcohol intermediates. The latter have been characterized by electrochemical reduction to a dihydro product which readily dehydrates to regenerate I. The tertiary alcohol intermediates can undergo a ring-opening reaction at pH≥6 to give a spectrally distinct and reversibly reducible pyrimidine derivatives(s) which slowly decompose to give alloxan or alloxanic acid and urea riboside. Alternatively, the tertiary alcohol can further hydrate to yield, ultimately, 5-hydroxyhydantoin-5-carboxamide-3-riboside or undergo a ring contraction reaction and hydrolysis leading to allantoin riboside. The peroxidase-catalyzed oxidation appears to follow essentially the same chemical pathway.