A novel alkaloid, cassiarin F (1), which showed potent antiplasmodial activity against Plasmodium falciparum in vitro, was isolated from the flowers of Cassia siamea, and its structure was elucidated on the basis of 2D NMR analyses. A total synthesis of 1 was also achieved by employing the Suzuki coupling constructing biaryl unit, nucleophilic aromatic substitution, and Houben-Hoesch type ring construction as key steps.

Four new alkaloids, cassiarins G, H, J, and K (1-4) which showed moderate antiplasmodial activity against Plasmodium falciparum 3D7, were isolated from the leaves of Cassia siamea (Leguminosae) and the structures of 1-4 were elucidated by 1D-and 2D-NMR analysis and X-ray crystallographic analysis.

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