Antitumor activity of phaeosphaeride A modified with nitrogen heterocyclic groups

New C(6)-derivatives of natural phaeosphaeride A (PPA) modified with pharmacophoric nitrogen heterocyclic groups have been synthesized. The reaction of 1,2,4-triazole with PPA mesylate produced both the product of the expected substitution of the methanesulfonate group and the PPA derivative with two 1,2,4-triazole groups: at the C(6) atom and the exocyclic C=C bond. The synthesized compounds, with the exception of those containing two 1,2,4-triazole groups, are superior in cytotoxic activity to the original phaeosphaeride and the positive control, etoposide.