Synthesis of novel spin-labeled podophyllotoxin derivatives as potential antineoplastic agents: Part XXV

A series of novel spin-labeled 4β-[(4-substituted)-1,2,3-triazol-1-yl]podophyllotoxin derivatives (17a-h) were firstly designed and synthesized with significant regioselectivity by employing Cu(I) catalyzed click approach, and evaluated for cytotoxicity against four human tumor cell lines (A-549, DU145, KB, and KBvin). Among them, compound 17h displayed the highest cytotoxic activity against the tumor cell lines tested. Significantly, compound 17h showed superior cytotoxic activity compared with etoposide (IC₅₀ 6.30 to>10 μM), a clinically available anticancer drug. Significant activity toward the drug resistant KBvin cell line revealed promising future for compound 17h as a new generation of epipodophyllotoxin-derived antitumor clinical trial candidate.