Adduct of tyrosine and the oncogen 3-acetoxyxanthine

A major product of the reaction of L-tyrosine (I) with the activated oncogen 3-acetoxyxanthine (II) at neutral pH has been characterized as 8-xanthinyl-4'-O-tyrosine (III). A similar product is formed with tyrosylglycine. Another major product was the hydantoin of tyrosine. 8-Xanthinyl-4'-O-tyrosine is hydrolyzed in acid to yield tyrosine and uric acid but is stable in base. The synthesis of 8-phenoxyxanthine is also described. A metabolite identical with III in several chromatographic systems was found in the urine of two rats after administration of radioactive 3-hydroxyxanthine. This represented about 0.05% of the urinary radioactivity.