Kinetics of deamination of cytosine nucleosides with etherified sugar hydroxyls.

The kinetics of deamination of derivatives of the therapeutically important 1-beta-D-arabinofuranosylcytosine with etherified (methylated) sugar hydroxyls has provided additional direct evidence for involvement of the 2'-hydroxyl in intramolecular catalysed deamination. In the case of 1-beta-D-lyxofuranosylcytosine, the kinetics of deamination of its 2'-O-methyl and 3'-O-methyl derivatives pointed to similar involvement of the "up" 2'-OH in intramolecular catalysed deamination. Participation by the 3'-OH, which is also in the "up" position, was excluded. A qualitative correlation was shown to exist between the electron density distributions on C(4) and C(6) of the cytosine rings in cytosine, 1-methylcytosine and cytidine, and their relative susceptibilities to deamination.