Synthesis of novel diterpenoid analogs with in-vivo antitumor activity

A lead compound 7 has antitumor effect, which was discovered by screening our small synthetic natural product-like compound (NPL) library. Based on the lead compound, a series of novel tricyclic diterpene analogs were synthesized and investigated for their activity against the growth of various tumor cell lines using the sulforhodamine B (SRB) assay. To our delight, most aromatic amide compounds exhibited more potent antitumor activity than the lead compound. The most active compound 19 (QW30) showed an average IC₅₀ 0.33 μM, which was 15-fold more potent than the lead compound. Most of the compounds with potent antitumor activity displayed less toxic on normal human fibroblasts (HAF) in comparison with the tumor cell lines. Especially 19, its selectivity indexes (SI) between HAF and cancer cell lines was 17.3 times better than the positive control compound podophyllotoxin. The apoptosis, colony formation and transwell migration assays of 7 and 19 were performed on T47D cell line. The in-vivo antitumor effect of 19 was also observed in T47D tumor-bearing mice without obvious toxicity.