Synthesis and Antitumor Biological Evaluation of the Derivatives of Natural Enmein and Nodosin

The aim of this study was to determine the antitumor activity of diterpenoid compounds. A series of modified diterpenoid derivatives (3-26) were obtained from the natural products enmein (1) and nodosin (2), using simple synthetic methods. The structures of the synthesized compounds were established through H-1 NMR, C-13 NMR and HRMS. The compounds were screened using a CCK8 assay for their antiproliferative activities against K562 and HepG2 human cancer cells. Most of the target compounds showed improved antiproliferative activity against K562 and HepG2 human cancer cells compared with natural enmein (1) and nodosin (2). 6-Propynyloxy-enmein (13), 6- propynyloxy-nodosin (25) and 6-cyclopropylmethoxy-nodosin (26) exhibited strong inhibitory activity against K562 cells with IC50 values of 3.58 +/- 0.16, 1.89 +/- 0.18, and 4.86 +/- 0.30 mu g/mL, respectively.