The antitumor agent, asterriquinone (ARQ) is a known metabolite isolated from the mycelium of Aspergillus terreus IFO 6123.Yamamoto et al. reported that ARQ analogs having a 2,5-dimethoxy-p-benzoquinone moiety and the 2,5-diamino-p-benzoquinone moiety did not show any cytotoxicity.As reported in our previous communication, a new metabolite, asterridinone, which has a furo[3,2-b]furan moiety instead of the p-benzoquinone moiety of ARQ, did not show cytotoxic activity towards P388 mouse leukemia cells, while isoasterriquinone and neoasterriquinone which have the tert- or iso-pentenyl groups at the different position of the indole ring, were active as was ARQ.These results indicate that the 2,5-dihydroxy-p-benzoquinone structure is more important for cytotoxic activity than the kind of prenyl groups and its position.In this study, to assess the contribution of the hydroxy group in the p-benzoquinone moiety to the cytotoxic activity of ARQ, we synthesized several ARQ derivatives, of which the one or two hydroxy group(s) were substituted with the acetyl, methoxy, and/or amino groups, and examined their cytotoxicity towards P388 cells.