Intramolecular general base catalysis in the hydrolysis of a phosphate diester. Calculational guidance to a choice of mechanism.

Notwithstanding its half-life of 70 years at 25 °C, the spontaneous hydrolysis of the anion of di-2-pyridyl phosphate (DPP) is thousands of times faster (ca. 3000 at 100 °C, over 10000-fold at 25 °C) than expected for a diester with leaving groups of pK(a) 9.09.

Activating water: important effects of non-leaving groups on the hydrolysis of phosphate triesters.

The high rate of spontaneous hydrolysis of tris-2-pyridyl phosphate (TPP) is explained by the activating effects of the non-leaving ("spectator") groups on P-OAr cleavage, and not by intramolecular catalysis. Previous work on phosphate-transfer reactions has concentrated on the contributions to reactivity of the nucleophile and the leaving group, but our results make clear that the effects of the non-leaving groups on phosphorus can be equally significant. Rate measurements for three series of phosphate triesters showed that sensitivities to the non-leaving groups are substantial for spontaneous hydrolysis reactions, although significantly smaller for reactions with good nucleophiles.

Phosphorylimidazole derivatives: potentially biosignaling molecules.

The phosphorylation of imidazole by two activated phosphate diesters and a triester gives phosphorylimidazole derivatives that are stable enough in aqueous solution to be observed and identified by ESI-MS/MS and NMR. Half-lives ranging from hours to days (in the case of the monoethyl ester) show that it is possible to design molecules with variable half-lives with potential to be used for biological intervention experiments as possible inhibitors of biosignaling processes or as haptens for the generation of antibodies.

Activating water: efficient intramolecular general base catalysis of the hydrolysis of a phosphate triester.

We have identified the first highly efficient intramolecular general base catalysis (IGBC) of a hydrolysis reaction, in a system where two general bases are available to assist the attack of the same nucleophilic water molecule. The suggested mechanism, available uniquely to a phosphate triester model, is readily available in enzyme active sites, and the results suggest a possible solution to the long-unsolved question of how enzymes are able to activate a water molecule to be a highly effective nucleophile.