Synthesis and SOD-Like Activity of Monosaccharide Derived Thiosemicarbazones

Abstract

The synthesis of new O-β-D-glucopyranosyl- and O-β-D-galactopyranosyl-2-hydroxyacetaldehyde thiosemicarbazones (5a,b) is reported. Oxidation of allyl glycoside 1 with KMnO₄ followed by NaIO₄ cleavage of the resulting diol 2 afforded aldehyde 3, which was then condensed with thiosemicarbazide and deprotected to give the target compounds (5a,b). Compounds 5a,b showed hydrolytic stability in neutral solution with half-life periods greater than 70 h. The SOD-mimetic activity was determined for the Cu(II) and Mn(II) complexes of 5a,b (IC₅₀ = 0.2–0.8 mM). This activity is higher by two orders of magnitude than copper (II) bisthiosemicarbazones. The ESR and UV-Vis data of Cu(II)-5a suggest a tetrahedral distortion of the coordination sphere around the central copper atom which could be the reason for their high SOD-mimetic activity.