Synthesis and structure-activity relationships of andrographolide analogues as novel cytotoxic agents.

Abstract Andrographolide 1 , the cytotoxic agent of the plant Andrographis paniculata was subjected to semi-synthetic studies leading to the preparation of a number of potent and novel analogues. Of the analogues synthesized, while 8,17-epoxy andrographolide 6 retained the cytotoxic activity of 1 , ester derivatives of 6 exhibited considerable improvement in activity. Lower activity was observed when the epoxy moiety in the triacetate 9 , derived from 6 was modified. Synthesis and structure–activity relationships are discussed.