Structure Confirmation and Evaluation of a Nonsteroidal Inhibitor of 17β-Hydroxysteroid Dehydrogenase Type 10

17 beta-Hydroxysteroid dehydrogenase type 10 (17 beta-HSD10) is a steroidogenesis enzyme known for its potential role in Alzheimer's disease. For comparison purposes between steroidal and nonsteroidal 17 beta-HSD10 inhibitors 1 and 2, respectively, we attempted the chemical synthesis of benzothiazole phosphonate derivative 2. Instead of a one-pot synthesis, we report a two-step synthesis with characterization of both imine intermediate 5 and final compound 2. Furthermore, complete assignation of H-1 and C-13 nuclear magnetic resonance (NMR) signals of 2 is provided, as we observed a divergence of NMR data with those published previously. Finally, biological assays showed that 1 and 2 inhibited the oxidation of estradiol (E2) into estrone (E1) by the 17 beta-HSD10 recombinant protein. However, in human embryonic kidney (HEK)-293 intact cells transfected with 17 beta-HSD10, only the steroidal inhibitor 1 induced a dose-dependent inhibition of E2 to E1 transformation.