Peroxide- and transition metal-free electrochemical synthesis of α,ß-epoxy ketones.

A novel electrochemical method for the synthesis of α,ß-epoxy ketones is reported. With KI as the redox mediator, methyl ketones reacted with aldehydes under peroxide- and transition metal-free electrolytic conditions and afforded α,ß-epoxy ketones in one pot (36 examples, 52-90% yield). This safe and environmental-friendly method has a broad substrate scope and can readily provide a variety of α,ß-epoxy ketones in gram-scales for evaluation of their anti-cancer activities.

Total Synthesis-Enabled Systematic Structure-Activity Relationship Study for Development of a Bioactive Alkyne-Tagged Derivative of Neolaxiflorin L.

Neolaxiflorin L (NL) is a low-abundant Isodon 7,20-epoxy- ent-kuarenoid and was found to be a promising anticancer drug candidate in our previous study. In order to study its structure-activity relationship (SAR), a diversity-oriented synthetic route toward two libraries of (±)-NL analogs, including analogs containing different functionalities in the same 7,20-epoxy- ent-kuarene skeleton and analogs with skeletal changes, has been developed. The results of this total synthesis-enabled SAR successfully led to a bioactive alkyne-tagged NL derivative, which could be a useful probe for proteomics studies.

Systemic study on the biogenic pathways of yezo'otogirins: total synthesis and antitumor activities of (±)-yezo'otogirin C and its structural analogues.

A systematic study of the biomimetic pathways to yezo'otogirin C under aerobic and anaerobic conditions has been investigated, and both are found to be feasible pathways to the natural product depending on the physiological conditions. Because of the lower activation energy, the aerobic process would be more favorable when the in vivo oxygen level is high. In the course of this study, a highly efficient synthetic route to (±)-yezo'otogirin C has been established in four steps (31% overall yield) from a readily available compound without using any protecting groups. The natural product and its structural analogues exhibited antitumor activities against several human cancer cell lines and appeared to arrest cell cycles in different phases.

Isolation and identification of two new compounds from the seeds of Moringa oleifera and their antiviral and anti-inflammatory activities.

Eleven compounds were isolated from methanol extract taken from Moringa oleifera seeds, including two previously unknown and nine known compounds. These compounds were authenticated as a carbamate, three phenylglycosides, four phenol glycosides, two nucleosides, and one flavonoid. Their chemical structures were elucidated using 1 D/2D nuclear magnetic resonance and high resolution-MS. Antivirus activity analyses revealed that Moringa A, glucomoringin, and Vitexin possessed strong inhibitory effects against the H1N1 virus, having IC50 values in the range of IC50 = 0.26 ± 0.03, 0.98 ± 0.17, and 3.42 ± 0.37 µg/mL, respectively. Furthermore, these three compounds could decrease the levels of TNF-α, IL-6, and IL-1ß, which occur in hosts because of H1N1 infections.

Development of Broad-Spectrum Antiviral Agents-Inspiration from Immunomodulatory Natural Products.

Developing broad-spectrum antiviral drugs remains an important issue as viral infections continue to threaten public health. Host-directed therapy is a method that focuses on potential targets in host cells or the body, instead of viral proteins. Its antiviral effects are achieved by disturbing the life cycles of pathogens or modulating immunity. In this review, we focus on the development of broad-spectrum antiviral drugs that enhance the immune response. Some natural products present antiviral effects mediated by enhancing immunity, and their structures and mechanisms are summarized here. Natural products with immunomodulatory effects are also discussed, although their antiviral effects remain unknown. Given the power of immunity and the feasibility of host-directed therapy, we argue that both of these categories of natural products provide clues that may be beneficial for the discovery of broad-spectrum antiviral drugs.

Virucidal activity of Moringa A from Moringa oleifera seeds against Influenza A Viruses by regulating TFEB.

Influenza A viruses (IAVs) are highly contagious pathogens infecting human and numerous animals. The viruses cause millions of infection cases and thousands of deaths every year, making IAVs a continual threat to global health. Our study demonstrated the virucidal activity of Moringa A as a new compound from Moringa oleifera seeds against IAVs. It inhibits virus replication in host cells and protects infected cells from the cytopathic effect induced by IAVs. The EC50andEC90 values of Moringa A for IAVs were 1.27 and 5.30 µM, respectively, when RAW264.7 cells were infected at MOI of 1. The different treatment experiments revealed that Moringa A has a significant inhibitory effect on the IAVs both before and afterdrug addition. Moringa A was observed to decrease the inflammatory cytokines TNF-α, IL-6, IL-1ß, and IFN-ß in H1N1 infected RAW264.7 cells. Finally, Moringa A was found to inhibit the expression and nuclear transfer of the cellular protein transcription factor EB (TFEB) and weaken the autophagy in infected cells, which could be an important antiviral mechanism. Our study demonstrates Moringa A has potent antiviral activity against IVAs, which could be due to the autophagy inhibition property.

Synthesis of the Tricyclic Picrotoxane Motif by an Oxidative Cascade Cyclization.

An oxidative cascade cyclization of ß-keto esters has been developed for the construction of the tricyclic picrotoxane motif in a single step, and DFT calculations suggested a possible cationic cyclization mechanism. This cascade cyclization can be operated on a 20 g scale to obtain a 77% total yield of the tricyclic products, which in turn can be converted to versatile intermediates for further elaboration to picrotoxanes and their structurally related compounds.

In(OTf)3-Catalyzed Cascade Cyclization for Construction of Oxatricyclic Compounds.

A highly diastereoselective cascade cyclization reaction has been developed for establishing a series of oxatricyclic compounds using Chan's diene and simple keto alkynal substrates with only 1 mol % of In(OTf)3 as the catalyst in 82-92% yields. The potential utility of this synthetic strategy has been demonstrated in model studies for the construction the core structures of 1α,8α:4α,5α-diepoxy-4,5-dihydroosmitopsin and cortistatin A.

Scalable synthesis enabling multilevel bio-evaluations of natural products for discovery of lead compounds.

Challenges in the development of anti-cancer chemotherapeutics continue to exist, particularly with respect to adverse effects and development of resistance, underlining the need for novel drugs with good safety profiles. Natural products have proven to be a fertile ground for exploitation, and development of anti-cancer drugs from structurally complex natural products holds promise. Unfortunately, this approach is often hindered by low isolation yields and limited information from preliminary cell-based assays. Here we report a concise and scalable synthesis of a series of low-abundance Isodon diterpenoids (a large class of natural products with over 1000 members isolated from the herbs of genus Isodon, which are well-known folk medicines for the treatment of inflammation and cancer), including eriocalyxin B, neolaxiflorin L and xerophilusin I. These scalable syntheses enable multilevel bio-evaluation of the natural products, in which we identify neolaxiflorin L as a promising anti-cancer drug candidate.