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

Ascorbic acid and its oxidation products have been implicated in non-enzyma tic 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 F-19 NMR spectrosc opy. Crystals of compound 6 from nitromethane belonged to the space group P 2(1) with a = 5.547(2), b = 6.769(3), c = 9.302(2) Angstrom, beta = 91.80(3 )degrees and Z = 2. Atomic coordinates, bond lengths and angles, hydrogen c oordinates, anisotropic and isotropic displacement parameters were similar if not identical with those of native ascorbic acid. Similarly, UV properti es and oxidation kinetics by CuCl2 at different pH values were essentially identical with ascorbic acid. Using 750 MHz F-19 NMR spectroscopy, five to six new fluorinated products were detected after overnight oxidation of 6 w ith Cu2+, suggesting that 6 may be a powerful and sensitive tool for assess ment of its catabolism in vivo. (C) 2000 Elsevier Science Ltd. All rights r eserved.