The degradation of DNA by hydrazine: identification of 3-ureidopyrazole as a product of the hydrazinolysis of deoxycytidylic acid residues.

The reaction of hydrazine with the cytosine residues of DNA yields 3-ureidopyrazole, in approximately 50% yield, in addition to the expected 3-aminopyrazole. This product has been identified by ultraviolet, infrared, nuclear magnetic resonance and mass spectroscopy. A product of the reaction of hydrazine hydrate with cytosine, formulated by others as NN'-di-(3-pyrazolyl) hydrazine, has been identified as 3-ureidopyrazole.