The mechanism for the conversion of uric acid into allantoin and dehydro-allantoin : A new look at an old problem

Abstract

The reaction of uric acids 1 with iodine in alkaline solution yields, on acidification, new dehydro-allantoins 11, or normal oxidation products, allantoins 13, depending on whether an excess or a stoichiometric amount of oxidant was used. The structure and regiochemistry of dehydro-allantoins 11 was established by chemical, spectroscopic, and 14C-labelling methods. These experimental results, in combination with other data, generate a new mechanistic scheme for the uricolytic pathway to allantoin, ruling out the intervention of a symmetrical transition state prior to the decarboxylation step.