ent-Trachyloban-19-oic acid (1) was isolated from sunflower Helianthus annuus L. [1-4].
It exhibited weak cytotoxic activity against gastric carcinoma [5] and displayed in vivo antiinflammatory
activity [4].
In order to obtain new polyfunctionalized tetracyclic terpenoids, the transformation of
ent-trachyloban-19-oic acid (1) was carried out by studying a PhI(OAc)2/LiBr reaction [6].
As a result, a mixture of polyfunctionalized tetracyclic diterpenoids (2) and (3) was
obtained, which was purified by column chromatography. The major compound (2) (61%) was
identified as the functionalized at C-12 and C-16 ent-kaurenic derivative. The minor compound
(3) (11%) had an ent-atisanic structure and it was functionalized at C-13, C-15 and C-17 atoms.
The structure and stereochemistry of the newly synthesized compounds (2) and (3) were
established on the basis of their IR, NMR spectral and GS-MS data.

In conclusion, the oxidative conversion of ent-trachyloban-19-oic acid (1) under
treatment with IBDA/LiBr led basically to ent-kaurenic carbonic framework derivatives.
References:
1. Pyrek, J. St. Tetrahedron, 1970, 26, 5029-5032.
2. Ungur, N.; Grinco, M.; Kulciţki, V.; Barba, A.; Bîzîcci, T.; Vlad, P. F. Chem. J. Mold. 2008, 4 (2),
106-109.
3. Sanni, S. B.; Behm, H.; Garcia-Granda, S.; Beurskens, P.(T.; Moers, F. G. J. Crystallogr. Spectrosc.
Res., 1990, 20, 483-489.
4. Dıaz-Viciedo, R.; Hortelano, S.; Giron, N.; Masso, J. M.; Rodriguez, B.; Villar, A.; De las Heras,
B. Biochem. Biophys. Res. Commun., 2008, 369, 761–766.
5. Ngamrojnavanich, N.; Tonsiengsom, S.; Lertpratchya, P.; Roengsumran, S.; Puthong, S.; Petsom,
A. Arch. Pharm. Res., 2003, 26, 898-901.
6. Emmanuvel, L.; Ali Shaikh, T. M.; Sudalai, A. Org. Lett., 2005, 7 (22), 5071-5074.