The most uncommon tricyclic sesquiterpenes, kelsoene 1 and prespatane
2, were isolated from cultured cells of liverwort Ptychanthus striatus
, and the labelling pattern of kelsoene biosynthesized from exogenous
[2-C-13]mevalonate suggested that kelsoene is biosynthesized from germ
acradienyl cation via alloaromadendranyl cation.