Abstract
Deuterium exchange for H–5 in 2′, 3′–O–isopropylideneuridine responds to both specific and general base catalysis in D2O solution buffered at neutral pD by N-methylimidazole. Cytidine and uridine do not exhibit this behaviour. However, methylcytosines incorporate deuterium at C-5 in solutions of hydroxylamine buffers in D2O both in the products of hydroxylamine reaction and into unchanged starting materials. Kinetic analysis of this phenomenon, monitored by proton n.m.r., provides a detailed analysis of the mechanism of reaction of hydroxylamine with cytosine derivatives.