Semi-synthesis and biological activity of γ-lactones analogs of camptothecin

A series of E-ring γ-lactone camptothecin derivatives were synthesized by semi-synthesis via a three-step domino reaction. Their biological activity was evaluated on two types of human tumor cell lines A549 and HT-29 with sulforhodamine-B (SRB) method. The antitumor activity of these compounds was lower than SN-38, only compound 12c was found to be close to the activity of Topotecan. The structure–activity relationship (SAR) of these analogs was studied and discussed.