Synthesis and cytotoxicity of racemic isodeoxypodophyllotoxin analogues with isoprene-derived side chains.

A series of isodeoxypodophyllotoxin (5) analogues, 26-38, with various isoprene-derived side chains at the E-ring were designed and synthesized. For comparison, compound 39, with a benzyloxy group on the E-ring, and six D-ring opened analogues, 40-45, were also prepared. All the synthetic compounds were evaluated for their cytotoxic activities in vitro against seven cultured human tumor cell lines. Compounds 27, 43, and 44 were more cytotoxic than etoposide on BEL-7404, A549, and HL-60 cell lines, respectively. However, none of the synthetic isodeoxypodophyllotoxins were more cytotoxic than podophyllotoxin (1).