Synthesis, Structure, and Cytotoxic Activities of a Novel Lactam of the Diterpenoid Isosteviol

A novel compound lactam of 15β-hydroxymethylisosteviol ethyl ester 3 has been synthesized and structurally characterized by IR, NMR, and HR-MS. Its X-ray crystallographic analysis revealed that the nitrogen is attached to C-13 instead of C-15. The reaction mechanism was discussed, and the title compound was further evaluated against HCT-116, HGC-27, and JEKO-1 cells by the MTT assay. The results demonstrated that compound 3 exhibited better cytotoxic activities than its corresponding precursor isosteviol.