A STABLE FORM OF VITAMIN-C - L-ASCORBATE 2-TRIPHOSPHATE - SYNTHESIS, ISOLATION, AND PROPERTIES

L-Ascorbate 2-triphosphate (AsTP) was synthesized by phosphorylating L-ascorbate (AsA) with sodium trimetaphosphate (STMP). The regioselectivity of the reaction was optimum (95% of 2-phosphory lation) when 1.62 M AsA was reacted with 1.3 equiv of STMP at pH 10.4-10.7 and 35 °C for 24 h or 55 °C for 5 h. The reaction yielded 4% unreacted AsA, 86% AsTP, 3% L-ascorbate 2-diphosphate (AsDP), 3% of a 4,5-elimination compound (ENE), and 1% L-ascorbate 2-monophosphate (AsMP). Those derivatives of AsA were isolated by anion-exchange chromatography and identified by UV and 1H, 13C, and 31P NMR spectroscopy. UV absorbance indicated that the L-ascorbyl moiety in AsTP was 1, 2, and 3 orders of magnitude more stable than AsA toward O2oxidation at 28-45 °C and pH 3, 6, and 8, respectively. AsMP, AsDP, and AsTP were readily hydrolyzed by acid phosphatase to give stoichiometric release of AsA. AsTP appeared to be equivalent to AsA as a source of vitamin C in guinea pigs. © 1990, American Chemical Society. All rights reserved.