Michael acceptor in gambogic acid--Its role and application for potent antitumor agents.

Gambogic acid (GA), a natural product with unique structure, was reported to have broad antiproliferation activities against cancer cell lines. As a reactive Michael acceptor, the 10-position of GA is susceptible to nucleophiles, thus limiting its clinical application as an anticancer agent. Moreover, the 6-OH forms an intramolecular hydrogen bond with 8-CO, which can make the 9, 10 double bond more reactive to nucleophiles. In this essay, two strategies (A and B) were applied to solve the above-mentioned problems. Strategy A was to increase the steric hindrance of C-10 to reduce the activity of GA towards nucleophiles. Strategy B was to replace the hydroxyl of C-6 with other substituents based on the assumption that the intra-molecular hydrogen bond could increase the electrophilicity of C-10. Results showed the electrophilicity of C-10 disappeared as well as the antiproliferation activity against cancer cell lines by introducing a methyl group at C-10. Strategy B showed that the electrophilicity of C-10 was reduced dramatically while maintained the activity by replacement of the hydroxyl of C-6 with neutral or basic groups.

Scaffold hopping of sampangine: discovery of potent antifungal lead compound against Aspergillus fumigatus and Cryptococcus neoformans.

Discovery of novel antifungal agents against Aspergillus fumigatus and Cryptococcus neoformans remains a significant challenge in current antifungal therapy. Herein the antifungal natural product sampangine was used as the lead compound for novel antifungal drug discovery. A series of D-ring scaffold hopping derivatives were designed and synthesized to improve antifungal activity and water solubility. Among them, the thiophene derivative S2 showed broad-spectrum antifungal activity, particularly for Aspergillus fumigatus and Cryptococcus neoformans. Moreover, compound S2 also revealed better water solubility than sampangine, which represents a promising antifungal lead compound for further structural optimization.

Discovery of a Novel Selective Dual Peroxisome Proliferator-Activated Receptor α/δ Agonist for the Treatment of Primary Biliary Cirrhosis.

A novel peroxisome proliferator-activated receptor (PPAR) α/δ dual agonist 5c was developed with an EC50 of 8 nM for PPARα, 5 nM for PPARδ, and >300-fold selectivity against PPARγ (EC50 = 2939 nM), respectively. Further ADME and pharmacokinetic studies indicated 5c possessed distinguished in vitro and in vivo profiles. The excellent in vivo efficacy of compound 5c was demonstrated by the rat primary biliary cirrhosis (PBC) model.

Discovery of simplified sampangine derivatives as novel fungal biofilm inhibitors.

Lack of novel antifungal agents and severe drug resistance have led to high incidence and associated mortality of invasive fungal infections. To tackle the challenges, novel antifungal agents with new chemotype, fungicidal activity and anti-resistant potency are highly desirable. On the basis of our previously identified simplified analogue of antifungal natural product sampangine, systemic structure-activity relationships were clarified and two novel derivatives showed promising features as novel antifungal lead compounds. Compounds 22b and 22c showed good fungicidal activity against both fluconazole-sensitive and fluconazole-resistant Candida albicans strains. Moreover, they were proven to be potent inhibitors of Candida albicans biofilm formation and yeast-to-hypha morphological transition by down-regulating biofilm-associated genes. In a rat vaginal Candida albicans infection model, compounds 22b and 22c showed excellent therapeutic effects with low toxicity. The results highlighted the potential of sampangine derivatives to overcome fluconazole-related and biofilm-related drug resistance.

Discovery of 3,3'-Spiro[Azetidine]-2-oxo-indoline Derivatives as Fusion Inhibitors for Treatment of RSV Infection.

A new series of 3,3'-spirocyclic-2-oxo-indoline derivatives was synthesized and evaluated against respiratory syncytial virus (RSV) in a cell-based assay and animal model. Extensive structure-activity relationship study led to a lead compound 14h, which exhibited excellent in vitro potency with an EC50 value of 0.8 nM and demonstrated 71% oral bioavailability in mice. In a mouse challenge model of RVS infection, 14h demonstrated superior efficacy with a 3.9log RSV virus load reduction in the lung following an oral dose of 50 mg/kg.

Correction to "The Discovery of 3,3'-Spiro[azetidine]-2-oxo-indoline Derivatives as Fusion Inhibitors for Treatment of RSV Infection".

[This corrects the article DOI: 10.1021/acsmedchemlett.7b00418.].

The discovery of novel antifungal scaffolds by structural simplification of the natural product sampangine.

Natural products are important sources of therapeutic drugs. However, it is a challenge to simplify the structure of natural products without decreasing the biological activity. Here we provide the first example of the successful simplification of an antifungal natural product. Starting from sampangine, two novel simplified scaffolds with excellent antifungal activity were discovered.

Design, synthesis and antifungal activity of novel triazole derivatives containing substituted 1,2,3-triazole-piperdine side chains.

Due to increasing incidence of invasive fungal infections and severe drug resistance to triazole antifungal agents, a series of novel antifungal triazoles with substituted triazole-piperidine side chains were designed and synthesized. Most of the target compounds showed good inhibitory activity against a variety of clinically important fungal pathogens. In particular, compounds 8t and 8v were highly active against Candida albicans and Cryptococcus neoformans with MIC values in the range of 0.125 µg/mL to 0.0125 µg/mL. They represent promising leads for the development of new generation of triazole antifungal agents. Molecular docking studies revealed that the target compounds interacted with CACYP51 mainly through hydrophobic and Van der Waals interactions.

Discovery of highly potent triazole antifungal derivatives by heterocycle-benzene bioisosteric replacement.

On the basis of our previously discovered triazole antifungal lead compounds, heterocycle-benzene bioisosteric replacement was used to improve their pharmacokinetic profile. The designed new triazole derivatives have good antifungal activity toward a wide range of pathogenic fungi. Their binding mode with the target enzyme was clarified by molecular docking. The MIC value of the highly potent compound 8f against Candida albicans, Candida tropicalis, and Cryptococcus neoformans is 0.016 µg/mL, 0.004 µg/mL, and 0.016 µg/mL, respectively. Moreover, preliminary pharmacokinetic studies revealed that it showed improved oral absorption as compared to the lead compound iodiconazole and deserved for further evaluations.