Accelerated hydrolysis of α-halo and α-cyano pyridinium relative to uracil derivatives: a model for ODCase-catalyzed hydrolysis of 6-cyanoUMP.

α-Halo and α-cyano pyridiniums were found to undergo facile hydrolysis, in contrast to the sluggish reactions of corresponding uracils. The greatly enhanced rates found with pyridinium compounds have indicated a possible source of the rate acceleration seen in the hydrolysis of 6-cyanouridine 5'-monophosphate catalyzed by orotidine 5'-monophosphate decarboxylase.