Asymmetric Synthesis of Griffipavixanthone Employing a Chiral Phosphoric Acid-Catalyzed Cycloaddition

Regio- and Diastereoselective Radical Dimerization Reactions for the Construction of Benzo[f]isoindole Dimers

This study presents a novel approach for synthesizing benzo[f]isoindole dimers, which involves cascade cyclization and oxidative radical dimerization. Our method allows for the formation of up to five carbon-carbon bonds in a single reaction, exhibiting remarkable diastereoselectivity and regioselectivity. The mechanism and regioselectivity were investigated through a combination of experiments and calculations.

Novel compounds discovery approach based on UPLC-QTOF-MS/MS chemical profile reveals birch bark extract anti-inflammatory, -oxidative, and -proliferative effects

ETHNOPHARMACOLOGICAL RELEVANCE

Betula pendula subsp. Mandshurica (Regel) Ashburner & McAll. Cortex (birch bark) is a globally traditional medicine for treating multiple inflammatory diseases. Its records are included in the Compendium of Materia Medica and other ancient medical literatures. However, uncovering its chemical profile and exploring novel biologically active compounds from birch bark remains a significant challenge.

AIM OF THE STUDY

To uncover the anti-inflammatory, -oxidative, and -proliferative mechanisms and potentially effective compounds of birch bark extract by combing chemical profiling, isolation, identification, together with in vivo, in vitro, and silico evaluation.

MATERIALS AND METHODS

Ultra-performance liquid chromatography coupled to quadrupole time-of-flight tandem mass spectrometry (UPLC-QTOF-MS/MS) was used to obtain the chemical profile of birch bark extract. The new compounds were obtained via column chromatography and analyzed using X-ray diffraction and electronic circular dichroism for absolute configuration confirmation. The zebrafish caudal fin inflammation-induced model, qPCR, and Western blot analysis were used to explore the effects and underlying mechanisms of birch bark extract. In vitro cytotoxicity assays and kinases screening conducted to gain preliminary insight into the anti-proliferative effects of birch bark extract and its isolated compounds. In addition, in-silico molecular docking was performed to investigate the putative mechanism.

RESULTS

UPLC-QTOF-MS/MS chemical profiles revealed 105 compounds in birch bark extract, with 80 of these were first reported in B. pendula subsp. Mandshurica cortex. We selected five compounds speculated as novel and isolated three ones (one triterpenoid derivative and two lupine series triterpenoids) for further analysis. Birch bark extract exerted antioxidative and anti-inflammatory effects on zebrafish, as shown by the downregulated reactive oxygen species levels and COX-2α, IL-1β, and TNF-α expression, which occurred through NF-ĸB signaling pathway activation. The in vitro anti-proliferative effects of birch bark extract and compound 44 were also unveiled. Moreover, the putative anti-tumor mechanism of compound 44 was revealed using kinase screening and in-silico molecular docking.

CONCLUSIONS

This study provided a predictable chemical profile and demonstrated the pharmacological effects of birch bark extract, elucidated the mechanism of this traditional Chinese medicine and suggested it as a novel anti-cancer candidate.

Recent advances in the synthesis of natural products containing the phloroglucinol motif

Covering: June 2009 to 2021Natural products containing a phloroglucinol motif include simple and oligomeric phloroglucinols, polycyclic polyprenylated acylphloroglucinols, phloroglucinol-terpenes, xanthones, flavonoids, and coumarins. These compounds represent a major class of secondary metabolites which exhibit a wide range of biological activities such as antimicrobial, anti-inflammatory, antioxidant and hypoglycaemic properties. A number of these compounds have been authorized for therapeutic use or are currently being studied in clinical trials. Their structural diversity and utility in both traditional and conventional medicine have made them popular synthetic targets over the years. In this review, we compile and summarise the recent synthetic approaches to the natural products bearing a phloroglucinol motif. Focus has been given on ingenious strategies to functionalize the phloroglucinol moiety at multiple positions. The isolation and bioactivities of the compounds are also provided.

Asymmetric Total Synthesis of Antibiotic Elansolid A

Elansolid A is a structurally complex polyketide macrolactone natural product that exhibits promising antibacterial properties. Its challenging asymmetric total synthesis was achieved by a convergent strategy, in which the tetrahydroindane core of the molecule and an eastern vinyl iodide moiety were combined as the main fragments. The central tetrahydroindane motif was constructed with high stereoselectivity by a bioinspired intramolecular Diels-Alder cycloaddition, generating four stereogenic centers in a single step. The stereocontrol of this key step could be achieved by virtue of a 1,3-allylic strain generated by the temporary introduction of a steric-directing iodine substituent on the substrate. The formation of the macrolactone motif that completes the synthesis was achieved via two different retrosynthetic disconnections, namely, a Suzuki-Miyaura cross-coupling or an alternative Mukaiyama esterification reaction.

Recent applications of asymmetric organocatalytic annulation reactions in natural product synthesis

The past two decades have witnessed remarkable growth of asymmetric organocatalysis, which is now a firmly established synthetic tool, serving as a powerful platform for the production of chiral molecules. Ring structures are ubiquitous in organic compounds, and, in the context of natural product synthesis, strategic construction of ring motifs is often crucial, fundamentally impacting the eventual fate of the whole synthetic plan. In this review, we provide a comprehensive and updated summary of asymmetric organocatalytic annulation reactions; in particular, the application of these annulation strategies in natural product synthesis will be highlighted.

Recent advances in total syntheses of complex dimeric natural products

Dimeric natural products are a collection of molecules with diverse molecular architectures and significant bio-activities. In this tutorial review, total synthesis of complex dimeric natural products accomplished in recent years are summarized and various dimerization strategies are discussed. By highlighting the selected representative examples, this review aims to demonstrate the recent tactics of dimerization which is an important process integrated into the whole synthetic sequences of dimeric natural products, provide insights on structural and chemical properties of monomers and dimers of related natural products, and promote further technological advances in organic synthesis and biological studies of complex dimeric natural products.

Anti-Tumor Xanthones from Garcinia nujiangensis Suppress Proliferation, and Induce Apoptosis via PARP, PI3K/AKT/mTOR, and MAPK/ERK Signaling Pathways in Human Ovarian Cancers Cells

BACKGROUND

Ovarian cancer (OC) is a serious public health concern in the world. It is important to develop novel drugs to inhibit OC.

PURPOSE

This study investigated the isolation, elucidation, efficiency, molecular docking, and pharmaceutical mechanisms of xanthones isolated from Garcinia nujiangensis.

METHODS

Xanthones were isolated, and purified by different chromatography, including silica gel, reversed-phase silica gel (ODS-C18), and semipreparative HPLC, then identified by analysis of their spectral data. Three xanthones were estimated for their efficiency on the human OC cells HEY and ES-2. 2 was found to be the most potent cytotoxic xanthones of those tested. Further, its mechanisms of action were explored by molecular docking, cell apoptosis, and Western blotting analysis.

RESULTS

Bioassay-guided fractionation of the fruits of Garcinia nujiangensis led to the separation of a new xanthone named nujiangexanthone G (1) and two known xanthones. Among these, isojacareubin (2) exhibited the most potent cytotoxic compound against the HEY and ES-2 cell lines. The analysis of Western blot suggested that 2 inhibited OC via regulating the PARP, PI3K/AKT/mTOR, and ERK/MAPK signal pathways in the HEY cell lines.

CONCLUSION

In conclusion, isojacareubin (2) might be a potential drug for the treatment of OC.

Cross-dehydrogenative coupling enables enantioselective access to CF3-substituted all-carbon quaternary stereocenters

A cross-dehydrogenative coupling strategy for enantioselective access to acyclic CF₃-substituted all-carbon quaternary stereocenters has been established. By using catalytic DDQ with MnO₂ as an inexpensive terminal oxidant, asymmetric cross coupling of racemic δ-CF₃-substituted phenols with indoles proceeded smoothly, providing CF₃-bearing all-carbon quaternary stereocenters with excellent chemo- and enantioselectivities. The generality of the strategy is further demonstrated by efficient construction of all-carbon quaternary stereocenters bearing other polyfluoroalkyl and perfluoroalkyl groups such as CF₂Cl, C₂F₅, and C₃F₇.

A cross-dehydrogenative coupling (CDC) strategy for enantioselective access to acyclic CF₃-substituted all-carbon quaternary stereocenters has been established.