Hunterines A–C, Three Unusual Monoterpenoid Indole Alkaloids from Hunteria zeylanica

Three new monoterpenoid indole alkaloids (MIAs), hunterines A–C (1–3), were isolated from Hunteria zeylanica. Compound 1 possesses a unique skeleton with an unprecedented azabicyclo[4.3.1]­decane ring system. Compounds 2 and 3 are a pair of epimeric vobasinylindole alkaloid heterodimers. Their structures including absolute configurations were established by spectroscopic analyses, X-ray diffraction, computational calculation, and the modified Mosher’s method. Plausible biogenetic pathways of 1–3 were also proposed. Alkaloid 1 showed moderate cytotoxic activity against the HepG2 cell line.