Kopsifolines A-F: a new structural class of monoterpenoid indole alkaloids from Kopsia

Six new indole alkaloids, named kopsifolines A-F (1-6), with an unprecedented hexacyclic carbon skeleton, constituting a new structural group of monoterpenoid indole alkaloids, were obtained from the leaf extract of a Malayan Kopsia species, and their structures were established by spectroscopic analysis.