Several analogues of thuriferic acid and derivatives, with the 3,4-methylenedioxyphenyl ring replaced by naphthalene, furan, thiophene and carbazole ring systems, have been prepared. The synthetic strategy is based on a conjugate addition-alkylation methodology followed by cationic cyclization in order to obtain the isopodophyllone analogues, which are transformed in the thuriferic acids. Their cytotoxic activities against several tumour cells lines are also described.