6-Deoxy-6-fluoro-l-ascorbic acid: crystal structure and oxidative degradation

Ascorbic acid and its oxidation products have been implicated in non-enzymatic modification of proteins in aging and diseases of oxidative stress. We have studied the feasibility of using 6-deoxy-6-fluoroascorbic acid (6) for identification of ascorbic acid degradation products by 19F NMR spectroscopy. Crystals of compound 6 from nitromethane belonged to the space group P21 with a=5.547(2), b=6.769(3), c=9.302(2) Å, β=91.80(3)° and Z=2. Atomic coordinates, bond lengths and angles, hydrogen coordinates, anisotropic and isotropic displacement parameters were similar if not identical with those of native ascorbic acid. Similarly, UV properties and oxidation kinetics by CuCl2 at different pH values were essentially identical with ascorbic acid. Using 750 MHz 19F NMR spectroscopy, five to six new fluorinated products were detected after overnight oxidation of 6 with Cu2+, suggesting that 6 may be a powerful and sensitive tool for assessment of its catabolism in vivo.