This paper deals with the conformational study in solution of leptocar
pin, a germacranolide with the heliangolide structure isolated from Le
ptocarpha rivularis D.C. The results obtained agree with the single cr
ystal X-ray diffraction studies, Leptocarpin and leptocarpin 50% inhib
ition of [S-35]-methionine affecting the (methyl-H-3)thymidine and (5,
6-H-3)uridine incorporation, when assayed in HeLa cells.