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Paper | Regular issue | Vol 38, No. 1, 1994, pp.81-94
Published online, 1st January, 1970
DOI: 10.3987/COM-93-6515
Antitumor Agents. VI. Synthesis and Antitumor Activity of Ring A-, Ring B-, and Ring C-Modified Derivatives of Camptothecin

Masamichi Sugimori, Akio Ejima, Satoru Ohsuki, Kensuke Matsumoto, Yasuyoshi Kawato, Megumi Yasuoka, Hiroaki Tagawa, and Hirofumi Terasawa*

*Exploratory Research Laboratories, Daiichi Pharmaceutical Co., Ltd., 16-13, Kitakasai 1-chome, Edogawa-ku, Tokyo 134, Japan


Eleven ring A-, ring B-, and ring C-modified analogues of the antitumor alklaoid camptothecin (1) were prepared and evaluated for cytotoxicity and antitumor activity against P388 mouse leukemia. Among the six ring A-modified analogues, hexacyclic compound (14) retained the same order of activity as 1. Most of the ring B- and ring C-modified analogues displayed greatly reduced activity, whereas compound (39), which has an alkylidene group at position 5, was found to be as active as 1. These results confirmed the necessity of the intact rings A, B, and C of 1 for antitumor activity. Further, the higher activity of 14 and 39 suggest that the "northern" part of the camptothecin molecule may be a suitable site for functionalization to obtain more potent analogues of 1.