20-esterification of 5-spiro CPT and their anticancer activity in vitro.

20-ester of 5-spirocycle campthothecin derivatives were successfully constructed and synthesised by Steglich esterification in a moderate yield. These derivatives showed a better solubility. Compared to parent compound, most of these 20-ester-5-spirocycle campthothecin derivatives (besides 3g ) showed a better inhibition activity against HepG2 cell line.