Synthesis and hydrolysis studies of phosphonopyruvate

Abstract

Phosphonopyruvate (1) is prepared in 56% yield from triethyl phosphonopyruvate (3) and pK_a values of 1.63, 2.40 and 7.41 determined. The stability of phosphonopyruvate is monitored at 75 °C in aqueous buffers over the pH range 0.6 to 8.3. The only products detected are pyruvate and inorganic phosphate. The pH–rate profile shows that the C–P bond is hydrolysed fastest in the monoanion and dianion of phosphonopyruvate, with rate constants of 1.94 × 10^–4 s^–1 for the monoanion and 1.05 × 10^–4 s^–1 for the dianion. For the reaction at pH 4.75, where the dianion predominates, ΔH^‡ is 114.0 kJ mor^–1 and ΔS^‡ is 5.4 J mol^–1 K^–1, the deuterium isotope effect, k_H/k_D is 1.08 ± 0.04, and there is non-selective phosphorylation of methanol and H₂O in an equimolar solution of these solvents. These results are consistent with a mechanism of hydrolysis of both the monoanion and dianion that involves a very largely dissociative transition state with monomeric metaphosphate character.