Antiviral Profiling of C-18- or C-19-Functionalized Semisynthetic Abietane Diterpenoids.

Viral infections affect several million patients annually. Although hundreds of viruses are known to be pathogenic, only a few can be treated in the clinic with available antiviral drugs. Naturally based pharmacotherapy may be a proper alternative for treating viral diseases. Several natural and semisynthetic abietane-type diterpenoids have shown important antiviral activities. In this study, a biological evaluation of a number of either C-18- or C-19-functionalized known semisynthetic abietanes against Zika virus, Dengue virus, Herpes virus simplex type 1, and Chikungunya virus are reported. Semisynthetic abietane ferruginol and its analogue 18-(phthalimid-2-yl)ferruginol displayed broad-spectrum antiviral properties. The scale-up synthesis of this analogue has been optimized for further studies and development. This molecule displayed an EC50 between 5.0 and 10.0 µM against Colombian Zika virus strains and EC50 = 9.8 µM against Chikungunya virus. Knowing that this ferruginol analogue is also active against Dengue virus type 2 (EC50 = 1.4 µM, DENV-2), we can conclude that this compound is a promising broad-spectrum antiviral agent paving the way for the development of novel antivirals.

Synthesis and Biological Studies of (+)-Liquiditerpenoic Acid A (Abietopinoic Acid) and Representative Analogues: SAR Studies.

The first semisynthesis and biological profiling of the new abietane diterpenoid (+)-liquiditerpenoic acid A (abietopinoic acid) (7) along with several analogues are reported. The compounds were obtained from readily available methyl dehydroabietate (8), which was derived from (-)-abietic acid (1). Biological comparison was conducted according to the different functional groups, leading to some basic structure-activity relationships (SAR). In particular, the ferruginol and sugiol analogues 7 and 10-16 were characterized by the presence of an acetylated phenolic moiety, an oxidized C-7 as a carbonyl, and a different functional group at C-18 (methoxycarbonyl, carboxylic acid, and hydroxymethyl). The biological properties of these compounds were investigated against a panel of six representative human tumor solid cells (A549, HBL-100, HeLa, SW1573, T-47D, and WiDr), five leukemia cellular models (NALM-06, KOPN-8, SUP-B15, UoCB1, and BCR-ABL), and four Leishmania species ( L. infantum, L. donovani, L. amazonensis, and L. guyanensis). A molecular docking study pointed out some targets in these Leishmania species. In addition, the ability of the compounds to modulate GABAA receptors (α1ß2γ2s) is also reported. The combined findings indicate that these abietane diterpenoids offer a source of novel bioactive molecules with promising pharmacological properties from cheap chiral-pool building blocks.