Synthesis and Antioxidant Activity of New Norcantharidin Analogs.

New norcantharidin analogs were designed and obtained as compounds with biological activity. As a starting material, exo-7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid anhydride was used. Three groups of compounds: dicarboximides, triazoles and thiazolidines were obtained in multistep reactions. The 1 H- and 13 C-NMR spectra were used to confirm the structures of all obtained products and they were in agreement with the proposed structure of substances. All derivatives were screened for their antioxidant activity. The most promising group was dicarboximides (1-4, 6). Derivatives 2-4 displayed antioxidant activity with EC50 =7.75-10.89 μg/ml, which may be comparable to strong antioxidant Trolox (EC50 =6.13 μg/ml). Excellent activity with EC50 =10.75 μg/ml also presented norcantharidin analog with 1,2,4-triazole system (12).