THE MECHANISM FOR THE CONVERSION OF URIC ACID INTO UROXANATE AND ALLANTOIN A NEW BASE-INDUCED 1,2-CARBOXYLATE SHIFT

Article abstract of DOI:10.1016/S0040-4020(01)90112-7

Alkaline permanganate oxidation of uric acid (1), particularly the late stages of the transformation into uroxanate (7) and allantoin (3), was studied by means of isotope-position labelling.A clear-cut degradation procedure developed for distinguishing among carbonyl and α-aminal carbon atoms in these products demonstrated conclusively that the carboxylic carbon of 7 and the 4-carbonyl carbon of 3 have their origin in C(5) of uric acid (1).None of the mechanisms that have been proposed for this reaction would have predicted this result.Isotope-labelling evidence, in combination with other data, revealed the sequence of events and identities of species involved in oxidative transformation of 1; the carbon-skeleton rearrangement of the first transient intermediate 4 must occur by a 1,2-carboxylate shift to give allanatoin-5-carboxylate (6) which either decarboxylates to allantoin (3) or else undergoes hydrolytic ring opening to uroxanate (7).