One-pot three steps cascade synthesis of novel isoandrographolide analogues and their cytotoxic activity

An efficient one-pot synthesis of novel andrographolide analogues is reported from a naturally occurring and abundant andrographolide isolated from aerial parts of Andrographis paniculata. Reactions in the one-pot proceed through a cascade epoxide ring opening by aniline derivatives/intramolecular ring closing and oxa-conjugate addition-elimination reactions. This methodology produces a new series of 17-amino-8-epi-isoandrographolide analogues in fair to excellent yields with high stereoselectivity using an economic and environmental procedure without base or catalyst at room temperature. Twenty-five analogues were obtained and cytotoxicity of all new analogues were evaluated against six cancer cell lines to search for a new lead compound based on andrographolide structure.