Etoposide (VP-16) is a potent human DNA topoisomerase II poison, derived from 4'-demethylepipodophyllotoxin, widely used in cancer chemotherapy. Continuous efforts have driven to synthesize new related compounds, presenting decreased toxic side effects, metabolic inactivation, drug resistance, and increased water solubility. Identified structure-activity relationships have pointed out the importance of the 4beta-substitution and of the configuration of the D ring. Here we report the synthesis of two novel series of derivatives of 4'-demethylepipodophyllotoxin. The first bears a carbamate chain in the 4 position (13a-f), whereas, in the second series, in addition to this chain, the lactone ring has been modified by shifting the carbonyl from position 13 to position 11 (27a-f). Moreover, an analogue of TOP-53 having this lactone modification has also been prepared (32). From this study, structure-activity relationships were established. Compounds 13a and 27a displayed potent cytotoxic activity against the L1210 cell line (10 to 20-fold higher than VP-16) and proved to be strong topoisomerase II poisons more potent than VP-16. From preliminary in vivo investigation of both compounds against P388 leukemia and orthotopically grafted human A549 lung carcinoma, it appeared that 13a and 27a constitute promising leads for a new class of antitumor agents.