Synthesis and antiproliferative activity of podocarpane and totarane derivatives.

The synthesis of podocarpanes, including 12,19-dihydroxy-13-acetyl-8,11,13-podocarpatriene (23), isolated from Gaultheria yunnanensis and not previously synthesized, and totarane-type terpenoids, starting from the natural labdane trans-communic acid (15), is described. Their antiproliferative activities against MCF-7, T-84 and A-549 human tumoural cell lines are studied. An antiproliferative effect was induced by compounds 23, 27 and 28, with IC50 < 10 µM in two (27) or three cell lines (23 and 28). No correlation with log P values was observed. The totarane o-quinone 27, and especially the catechol 28, which is readily oxidisable to compound 27, were the most active compounds, highlighting the functional groups present in C11 and C12. Compound 28 showed limited toxicity in normal peripheral blood mononuclear cells (78.5% cell viability versus non-treated control cultures at 10 µM), and appeared to exert an antiproliferative effect in A-549 cells (IC50 0.6 µM) through a mechanism that involves the induction of apoptosis mediated by an increased Bax/Bcl-2 ratio. The results of the present study indicate that compound 28, at least, might be useful as an antitumoral agent. Further studies are required to elucidate the cellular and molecular elements involved in its effect, and the activity/toxicity in preclinical models.

Antiproliferative Activity of Natural Taiwaniaquinoids and Related Compounds.

The in vitro antiproliferative activities of some taiwaniaquinoids and related compounds with functionalized A, B, or C rings against human breast (MCF-7), colon (T-84), and lung (A-549) tumor cell lines were assayed. The most potent compounds, 16, 27, and 36, were more effective than the naturally occurring taiwaniaquinones A (4) and F (5) in all three cell lines. The structure-activity relationship study of these new taiwaniaquinoids highlighted the correlation between the bromo substituent and the antiproliferative activity, especially in MCF-7 cells. These findings indicate that some of the taiwaniaquinoids might be useful as cytostatic agents against breast, colon, and lung cancer cell lines.

Short Route to Cassane-Type Diterpenoids: Synthesis of the Supposed Structure of Benthaminin 1.

A short route toward aromatic cassane diterpenes from labdane terpenoids has been developed. In the key step, the aromatic ring with the oxygenated function at C-12 and the characteristic carbon group at C-14 of the target compounds is elaborated via a Diels-Alder/aromatization sequence of a furanosesquiterpene and methyl propiolate. On this basis, the synthesis of the proposed structure of benthaminin 1 from trans-communic acid has been achieved. The physical properties of the synthetic compound are somewhat different from those reported for the natural product.