The ent-kaur-16-en-19-oic acid (1) was isolated from different vegetal sources, especially from sunflower (Helianthus sp). [1]. We have described isolation of acid (1) from the integral sunflower (Helianthus annuus L.) dry wastes [2-3]. The scientific interest for tetracyclic diterpenic ent-kaur-16-en-19-oic acid (1) and its derivatives can be explained by their broad spectrum of biological activities [4-6]. We report in the current communication a series of chemical transformations leading to additional functionalization at exo-methylenic double bond of (1). The synthesized diterpenic compounds (2) – (5) have been identified on comparison of their spectroscopic data (IR, 1H- and 13C-NMR) with those given in the literature. The structure and stereochemistry of the new compound (6) was established on the basis of the spectral data. Preliminary investigation of the biological activity profile of diterpenic acids (3), (4) and (6) showed a selective inhibition of HELA BxPc-3, RD tumor cells.