4-(1'-d-ribitylamino)-5-amino-2,6-dihydroxypyrimidine, the Second Product of the Riboflavin Synthetase Reaction.

In this reaction, an additional compound (X) should be formed in amounts equal to that of riboflavin. It has been shown (2) that all of the atoms of the pyrimidine portion, nitrogen atom 8, and the ribityl moiety of 6,7-dimethyl8.ribityllumazine are retained in the unknown compound. Furthermore, during isolation by column chromatography, the unknown compound was cleaved into ribitylamine and a compound ret.aining all of the atoms of the pyrimidine ring of the substrate. It was shown that the latter is either alloxan or closely related chemically to alloxan. Thus, the evidence suggested that Compound X is chemically unstable and is probably a derivative of 6-ribitylaminouracil. In this report, the isolation of the second product of the riboflavin synthetase reaction and its characterization as 4-(I’-Dribitylamino)-5-amino-2,6-dihydroxypyrimidine (6.ribitylamino5-aminouracil)’ is described.