An Improved Synthesis of L-Ascorbate 2-Polyphosphate

L-Ascorbate (0) reacted rapidly with sodium trimetaphosphate (STMP) at 20–25°C and constant pH 9.5–10.0 in the presence of calcium ion. Barium and strontium ions also catalyzed the phosphorylation reaction, but not magnesium ion. The optimum reaction mixture was initially 1.4 M L-ascorbate, 1.8 M STMP, 1.7 M calcium hydroxide, and 0.4 M calcium chloride. Over a 20-min reaction period, pH was maintained by adding approximately 0.1 g calcium hydroxide in a 20% aqueous slurry. The initial and final Ca/P ratios were -0.36 and 0.42, respectively. The reaction products were 98.8% 2-phosphorylated L-ascorbate, 1.2% unreacted 0, and a trace of 4,5-ene, probably formed through 5,6-phosphorylated L-ascorbate 2-polyphosphate. High-performance liquid chromatography with UV detection and preparative anion-exchange chromatography showed the presence of eight 2-phosphorylated derivatives of 0 and two of the 4,5-ene skeleton. Rapid 2-phosphorylation prevented accumulation of the 4, 5-elimination reaction, and three 5,6-cyclophosphoesters of 0 were found in the reaction products. A Ca/Na (3/1) salt of L-ascorbate 2-polyphosphate was isolated in 88% yield as a white, odorless powder containing 33% of L-ascorbate equivalents. Crystalline cyclohexylainmonium salts of L-ascorbate 2-mono, di, and triphosphates were prepared.