Acuminolide (1), a cytotoxic labdane diterpene with a new type of carb
on skeleton, was isolated from the stem bark of Neouvaria acuminatissi
ma, together with its congeners 17-O-acetylacuminolide (2) and an inac
tive derivative, spiroacuminolide (3). Their structures were determine
d on the basis of spectroscopic and chemical methods, as well as X-ray
crystallography. Isolation, structure elucidation and bioassay result
s are described.