Bousangine A, a novel C-17-nor aspidosperma-type monoterpenoid indole alkaloid from Bousigonia angustifolia.

Two new monoterpenoid indole alkaloids, bousangines A (1) and B (2), were isolated from the twigs and leaves of Bousigonia angustifolia. Their structures including absolute configurations were elucidated by a combination of MS, NMR, ECD calculation, and single-crystal X-ray diffraction analysis. Bousangine A (1) possessed a rearrangement pentacyclic skeleton derived from aspidosperma-type alkaloids with C-17 degradation. Their antiproliferative activity against several human cancer cell lines were evaluated.