Crystal Structure and Antioxidant Activity of 5,6-O-(4-chlorophenyl)-L-Ascorbic Acid Synthesized with Nanosolid Superacid

Abstract

The title compound 5,6-O-(4-chlorophenyl)-L-ascorbic acid (C13H11ClO6) was synthesized using nanosolid superacid SO2-4/SnO2 as a catalyst and its structure was characterized by IR, 1H NMR and single-crystal X-ray diffraction. 1H NMR data indicated the product is a mixture of two diastereomer compounds (a(7S) and b(7R)). And the crystal of one diastereomer compound a(7S) belongs to orthorhombic system, space group P212121 with a = 6.501(4), b = 7.803(5), c = 25.013(15) Å, V 1268.7(13) Å3, Z = 4, Dc 1.564g/cm3, μ(Mo-Kα) = 0.325 mm-1, F(000) = 616, R = 0.0255 and wR(I > 2σ (I)) = 0.0624. X-ray crystal structure data display that the hydrogen bonding interactions observed link the molecules to form a three-dimensional system. In addition, 5,6-O-(4-chlorophenyl)-L-ascorbic acid (CPAA) exhibited strong free-radical scavenging activities in vitro against 2,2-diphenyl-1-picrylhydrazyl and superoxide anion. Therefore, CPAA should be investigated further as a worthy antioxidant.