A novel, broad-spectrum antitumor compound containing the 1-hydroxycyclohexa-2,5-dien-4-one group: the disclosure of a new antitumor pharmacophore in protoapigenone 1.

The synthesis of a new compound 9 containing the 4-hydroxy-2,5-cyclohexadien-1-one system, a key elements toward elucidation of the protoapigenone 1 antitumor pharmacophore, was described. The compound showed potent in vitro antitumor potency with low micromolar IC(50)'s against breast, ovarian, prostate, liver, pancreas, and blood cancer cell lines tested and could inhibit tumor growth in vivo but no significant impairment of hematopoiesis or immune function was observed. The minimum structural pharmacophore of 1 has now been refined.