Preparation and structure-activity relationships of novel asterriquinone derivatives

Asterriquinone (ARQ, 1a) is an antitumor metabolite of Aspergillus terreus IFO 6123. To gain insight into the structure-activity relationships of ARQ, a series of chemically modified derivatives (1-6), the ARQ analogues (be) and the 2,5-dihydroxy-p-benzoquinone analogues (f-h), were prepared, and cytotoxic activity against mouse leukemia P388 cells investigated. Results indicated that: 1) at least one hydroxy group or acetoxy group in the p-benzoquinone moiety is important to exhibit cytotoxicity; 2) in the p-benzoquinone moiety, a single methoxy group and/or one acetoxy group substitution showed more potent cytotoxicity than when two hydroxy groups are substituted (1); 3) the indole ring is important for the cytotoxicity of ARQ analogues; 4) the 1,1-dimethyl-2-propenyl group in the indole ring is not important for the cytotoxic activity of ARQ.