Synthesis of isotopically labeled phosphoenolpyruvic acid

Phosphoenolypyruvic acid isotopically labeled at C1 and C2 as well as at the bridging oxygen of the phosphate was synthesized in eleven steps with an overall yield of 15-20%. The cornerstone of this synthesis was the use of 1,3-dithiane as an acyl anion equivalent. The anion derived from this compound was alkylated with isotopically labeled methyl iodide and carboxylated with isotopically labeled carbon dioxide. After protection of the carbonyl group as the benzyl ester, the carbonyl group was unmasked with N-bromosuccinimide. The oxygen of the carbonyl group was exchanged with 18O water and the benzyl group was removed via hydrogenolysis. The labeled pyruvic acid thus formed was converted to phosphoenolypyruvic acid with a modification of the Perkow reaction. This was accomplished in four steps with a 50% overall yield using dimethyl trimethylsilyl phosphite as the phosphorylating agent. The last four steps were accomplished without isolation of intermediates. The extent of isotopic enrichment was determined using 31P NMR