Synthesis and Biological Evaluation of 7‐Alkenyl Homocamptothecins as Potent Topoisomerase I Inhibitors

Abstract

Homocamptothecin (hCPT) is a camptothecin (CPT) derivative with a seven-membered β-hydroxylactone E ring, which shows higher lactone stability and improves topoisomerase I (Topo I) inhibition activity. In an attempt to improve the antitumor activity of homocamptothecins, a series of 7-alkenyl-homocamptothecin derivatives was designed and synthesized based on a semisynthetic route starting from CPT. Most of the synthesized compounds exhibit higher cytotoxic activities on the A-549 tumor cell line than topotecan (TPT). Some compounds such as 2a and 2o show a broad in vitro antitumor spectrum and exhibit superior Topo I-inhibition activity.