Arisandilactone A, a New Triterpenoid from the Fruits of Schisandra arisanensis

Potential natural product 3,4-seco-schitriterpenoids from Kadsura japonica L. as anti-neuroinflammatory agents

In the present study, the undescribed schitriterpenoids, kadsujanonols A-I (1-9), and eleven reported compounds (10-20) were isolated from K. japonica L. vines. Their structures of 3,4-seco-schitriterpenoids were elucidated mainly by spectroscopic analyses including 1H-, 13C-, and 2D-NMR, IR, HRESIMS spectra. The spatial configurations were determined by the single-crystal X-ray diffraction analysis of kadsujapnonol A (1), 15, 17, and 18, CD data and computational analysis. Furthermore, all isolates were evaluated for the anti-neuroinflammatory activity on LPS-stimulated NO production in BV2 microglial cells and compounds 2, 4, 5, 7, 9, 11, 13-16, and 18 exposed better or comparable suppression abilities than PDTC. Among them, kadlongilactone B (14) showed the best significant inhibiting ability (IC50 = 0.87 μg/mL) and the effect is through the attenuation of the inflammatory transcription factor p65NF-κB. Preliminary structure-activity relationship revealed that δ-lactone at the side chain and 7-member lactone at C-3/C-4, and 3,4:9,10 ring opening are important.

The Journey of Schinortriterpenoid Total Syntheses

Plants in the Schisandraceae family are important components of the traditional Chinese herbal medicines and are often used to treat various illnesses. Therefore, these Schisandraceae plants are valuable sources for the discovery of new chemical entities for novel therapeutic development. Considerable progress has been made in the identification of bioactive and structurally novel triterpenoids from the Schisandraceae family in the past two decades. In particular, Sun and co-workers have successfully isolated over 100 nortriterpenoids from the Schisandraceae family. Some of these nortriterpenoids have strong inhibitory activities toward hepatitis, tumors, and HIV-1. However, the natural scarcity of these nortriterpenoids in the Schisandraceae plants has hampered their isolation and further biomedical development, and their biosynthesis has not been fully elucidated. It is therefore important and urgent to develop efficient and streamlined total syntheses of these medicinally important nortriterpenoids. Such syntheses will provide sufficient materials for detailed biological studies as well as new synthetic analogues and probe molecules to improve their biological functions and elucidate their mode of actions. However, because of their structural novelty and complexity, the total syntheses of these nortriterpenoid natural products present a significant challenge for synthetic chemists, despite the progress made in organic synthesis, particularly total synthesis, in the 20th century and since the beginning of the 21st century. New synthetic methodologies and strategies therefore need to be invented and developed to facilitate the total syntheses of these nortriterpenoid natural products. With this in mind, our group has spent the last 15 years, ever since the isolation of micrandilactone A (1) by Sun and co-workers in 2003 ( Sun et al. Org. Lett. 2003 , 5 , 1023 - 1026 ), working on synthetic studies with a view to developing methods and strategies for the total syntheses of schinortriterpenoids. Enabling methods such as a thiourea/Pd-catalyzed alkocycarbonylative annulation and a thiourea/Co-catalyzed Pauson-Khand reaction have been developed under these circumstances to form the key ring systems and stereocenters of these complex target molecules. These methodological advances have led us to the first total syntheses of schindilactone A (2), lancifodilactone G acetate (6a), 19-dehydroxyarisandilactone A (9), and propindilactone G (10) with diverse structural features via a branching-oriented strategy. The chemistry developed during our total synthesis campaign has not only helped us to deal with various challenges encountered in the syntheses of the four target molecules, but has also opened up new avenues for synthesizing other naturally occurring schinortriterpenoids and their derivatives, which will likely result in molecules with improved biological functions and tool compounds to enable elucidation of their mechanism of actions or potential cellular targets. This Account highlights the chemistry evolution of our schinortriterpenoid syntheses.

Palladium(0)-catalyzed [2 + 2 + 1] cyclization of 1,6-enynes with vinyl bromides: a highly diastereoselective synthesis of tetrahydro-1H-cyclopenta[c]furans bearing two quaternary carbon centers

A new cascade process has been accomplished for the synthesis of tetrahydro-1H-cyclopenta[c]furans through palladium-catalyzed [2 + 2 + 1] cyclization of 1,6-enynes with vinyl bromides. Notably, the key feature of this transformation is the use of vinyl bromides as the C1 building block. Various functionalized tetrahydro-1H-cyclopenta[c]furans bearing two quaternary carbon centers could be obtained in good yields with excellent diastereoselectivities.

Biomimetically inspired asymmetric total synthesis of (+)-19-dehydroxyl arisandilactone A

Complex natural products are a proven and rich source of disease-modulating drugs and of efficient tools for the study of chemical biology and drug discovery. The architectures of complex natural products are generally considered to represent significant barriers to efficient chemical synthesis. Here we describe a concise and efficient asymmetric synthesis of 19-dehydroxyl arisandilactone A—which belongs to a family of architecturally unique, highly oxygenated nortriterpenoids isolated from the medicinal plant Schisandra arisanensis. This synthesis takes place by means of a homo-Michael reaction, a tandem retro-Michael/Michael reaction, and Cu-catalysed intramolecular cyclopropanation as key steps. The proposed mechanisms for the homo-Michael and tandem retro-Michael/Michael reactions are supported by density functional theory (DFT) calculation. The developed chemistry may find application for the synthesis of its other family members of Schisandraceae nortriterpenoids.

Arisandilactone A is a natural product with a complex oxa-bridged tricyclic carbon core, making it a challenging target in total synthesis. Here the authors report an asymmetric total synthesis of its 19-dehydroxy derivative, with homo-Michael and tandem retro-Michael/Michael reactions as key steps.

Triterpenoids from the Schisandraceae family: an update

Plants from the Schisandraceae family produce architecturally interesting triterpenoids, including lanostanes, cycloartanes, and schinortriterpenoids. This review focuses on their structures, classifications, biogenetic pathways, syntheses, and bioactivities (from February 2008 to May 2014).

Kadcotriones A-C: tricyclic triterpenoids from Kadsura coccinea

Three new triterpenoids, kadcotriones A-C (1-3), together with the biogenetically related lanostane-type triterpenoid (4), were isolated from Kadsura coccinea. Compound 1 features a 12,14β-dimethyl 6/6/6-fused tricyclic skeleton, while 2 and 3 are characterized by a 6/6/5-ring system. Their structures were determined by NMR and electronic circular dichroism spectroscopic methods. Compounds 2 and 4 exhibited anti-HIV-1 activities with EC50 values of 30.29 and 54.81 μM, respectively.

Lancolides, antiplatelet aggregation nortriterpenoids with tricyclo[6.3.0.0(2,11)]undecane-bridged system from Schisandra lancifolia

A new class of highly oxygenated Schisandra nortriterpenoids, lancolides A-D (1-4), from Schisandra lancifolia, represents the first example of natural products that possess a tricyclo[6.3.0.0(2,11)]undecane-bridged system. Their structures were elucidated by NMR spectra, X-ray diffraction, and quantum chemical calculations. Lancolides A (1) and D (4) had specific antiplatelet aggregation induced by platelet-activating factor (PAF).

Triterpenoids

This review covers the isolation and structure determination of triterpenoids, including squalene derivatives, protostanes, lanostanes, holostanes, cycloartanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, quassinoids, lupanes, oleananes, friedelanes, ursanes, hopanes, serratanes and saponins; 305 references are cited.

Schilancitrilactones A-C: three unique nortriterpenoids from Schisandra lancifolia

Three unique nortriterpenoids, schilancitrilactones A-C (1-3), were isolated from the stems of Schisandra lancifolia . Compound 1 possesses a 5/5/7/5/5/5-fused hexacyclic ring system with a C(29) backbone, while 2 and 3 feature a C(27) skeleton with a 5/7/5/5/5-fused pentacyclic ring system. Their absolute stereochemistries were established by CD and single-crystal X-ray diffraction experiments. Compound 3 showed anti-HIV-1 activity with an EC(50) value of 27.54 μg/mL, and 1 exhibited antifeedant activity at 15.73 μg/cm(2).