Sinoracutine, a novel skeletal alkaloid with cell-protective effects from Sinomenium acutum

Four new alkaloids from the roots of Dactylicapnos scandens

Four new alkaloids (1 - 4), together with five known ones (5 - 9), were isolated from the bulbs of Dactylicapnos scandens. The structures were determined by analysis of their spectroscopic data and quantum-chemical calculations. All the isolates were tested for their ability to modulate neuronal Ca2+ mobilization in primary cultured neocortical neurons. Compound 8 inhibited spontaneous Ca2+ oscillations at low micromolar concentrations.

New N-oxide alkaloids from the stems of Sinomenium acutum

Six new alkaloids (1-6) and six known alkaloids (7-12) were obtained from the stems of Sinomenium acutum. Among them, compounds 1-3 and 6 were four N-oxide alkaloids. The structures and absolute configurations of these new alkaloids were elucidated through comprehensive data of 1D and 2D NMR, HRESIMS and ECD spectra. All isolated compounds were evaluated in vitro for their inhibitory activities against nitric oxide (NO) production and inhibitory effects on AChE. Among them, the sinomenine N-oxide (9) was the most potent NO production inhibitor, with an IC₅₀ value of 23.04 μM.

Sinomenium acutum: A Comprehensive Review of its Botany, Phytochemistry, Pharmacology and Clinical Application

Sinomenium acutumis the dry stem of Sinomenium acutum (Thunb.) Rehd et Wils. (S. acutum) and Sinomenium acutum(Thunb.) Rehd. et Wils. var. cinereumRehd. et Wils and is mainly distributed in China and Japan. As a traditional Chinese medicine (TCM) for dispelling wind and dampness in China, it is widely distributed and has a long history of drug use. In recent years, with the increase of the incidence of rheumatoid disease, S. acutum has become the focus of research. This paper reviews the literature on the chemical constituents, pharmacological effects, clinical applications and pharmacokinetics and safety of S. acutum from the past 60 years. At present, more than 210 natural compounds have been isolated from S. acutum, including alkaloids, lignans, triterpenoid saponins, steroids, and other structures. Pharmacological activities of S. acutum were mainly reported on anti-inflammatory, analgesic, anti-allergic, immunosuppressive, anti-tumor, liver-protective, anti-oxidative, and other effects, and clinical applications were mainly recorded on rheumatoid arthritis, ankylosing spondylitis, and other diseases. The clinical use of SIN has fewer side effects and more safety; only a small number of gastrointestinal reactions occurred, and the symptoms disappeared after the drug stopped. The purpose of this paper is to lay a foundation and provide reference for the follow-up research and wide application of S. acutum.

Enantioselective Total Synthesis of Cepharatines via Bioinspired Ring Reconstruction

We describe enantioselective total syntheses of cepharatines A-D, members of the hasubanan alkaloid family, which feature an unusual tetracyclic skeleton including an azabicyclo[3.3.1]nonane motif. A key reaction is a regio-divergent oxidative phenolic coupling reaction that affords the tricyclic core structure of hasubanan with different substitution patterns on the A-ring, including the all-carbon quaternary stereogenic center at C13, in a single step. The characteristic tetracyclic azabicyclo[3.3.1]nonane motif was constructed by means of a bioinspired cascade reaction involving the retro-aza-Michael reaction/hemiaminal formation.

Unified divergent strategy towards the total synthesis of the three sub-classes of hasubanan alkaloids

Elegant asymmetric synthesis of hasubanan alkaloids have been developed over the past decades. However, a divergent approach leading to all three sub-classes of this family of natural products remains unknown. We report herein the realization of such an endeavor by accomplishing enantioselective total syntheses of four representative members. The synthesis is characterized by catalytic enantioselective construction of the tricyclic compounds from which three different intramolecular C-N bond forming processes leading to three topologically different hasubanan alkaloids are developed. An aza-Michael addition is used for the construction of the aza-[4.4.3]-propellane structure of (-)-cepharamine, whereas an oxidation/double deprotection/intramolecular hemiaminal forming sequence is developed to forge the bridged 6/6/6/6 tetracycle of (-)-cepharatines A and C and a domino bromination/double deprotection/cyclization sequence allows the build-up of the 6/6/5/5 fused tetracyclic structure of (−)-sinoracutine.

Several Hasubanan alkaloids have been synthesized in the past decades, however a divergent approach to access the 3 subclasses of such natural products has not been reported yet. Here, the authors show the enantioselective total syntheses of four representative members via a unified strategy leading to the three topologically different classes of alkaloids.

Evolution of Pauson-Khand Reaction: Strategic Applications in Total Syntheses of Architecturally Complex Natural Products (2016–2020)

Metal-mediated cyclizations are important transformations in a natural product total synthesis. The Pauson-Khand reaction, particularly powerful for establishing cyclopentenone-containing structures, is distinguished as one of the most attractive annulation processes routinely employed in synthesis campaigns. This review covers Co, Rh, and Pd catalyzed Pauson-Khand reaction and summarizes its strategic applications in total syntheses of structurally complex natural products in the last five years. Additionally, the hetero-Pauson-Khand reaction in the synthesis of heterocycles will also be discussed. Focusing on the panorama of organic synthesis, this review highlights the strategically developed Pauson-Khand reaction in fulfilling total synthetic tasks and its synthetic attractiveness is aimed to be illustrated.

Enantioselective Synthesis and Racemization of (-)-Sinoracutine

Sinoracutine is a recently isolated alkaloid with unusual stereochemical and biological properties. It features an unprecedented tetracyclic 6/6/5/5 skeleton that bears an N-methylpyrrolidine ring fused to a cyclopentenone. Interestingly, both enantiomers of sinoracutine have been independently isolated from the same plant, yet the molecule does not appear to occur as a racemate. Here, we present a short synthesis of (-)-sinoracutine that relies on a highly diastereoselective Pauson-Khand reaction and a Mandai-Claisen reaction to install the quaternary stereocenter. Our work establishes the absolute configuration of the levorotatory isomer and suggests that the optical purity of sinoracutine varies in nature due to its gradual racemization. Experimental evidence supports this proposal, and a plausible mechanism for the racemization is provided.

Sinomenium acutum: a review of chemistry, pharmacology, pharmacokinetics, and clinical use

CONTEXT

Sinomenium acutum (Thumb.) Rehd. et Wils. (Menispermaceae, SA) has been used as a traditional Chinese medicine in the treatment of various diseases for hundreds of years; it possesses favorable effects against autoimmune diseases, especially rheumatoid arthritis (RA). A great number of investigations have been done on SA in the last decade, but they are usually scattered across various publications.

OBJECTIVE

The purpose of this article is to summarize and review the published scientific information about the chemical constituents, pharmacological effects, pharmacokinetics, and clinic applications of this plant since 2000.

RESULTS

The information for 89 cases included in this review was compiled. The SA contains alkaloids, sterols, phospholipids, and some other components. A great deal of pharmacological and clinic research has been done on sinomenine, a main compound from SA, which mainly focuses on the immune system, cardiovascular system, and nervous system.

CONCLUSION

Previous studies strongly support its potential as an effective adaptogenic herbal remedy. There is no doubt that SA is being widely used now and will have extraordinary potential for the future.

Two new morphinane alkaloids from Sinomenium acutum

Two new morphinane alkaloids, 1-hydroxy-10-oxo-sinomenine (1) and 4,5-epoxy-14-hydroxy sinomenine N-oxide (2), have been isolated from the stems of Sinomenium acutum. Their structures were established by various spectral analyses, especially 2D NMR experiments. The structure of 2 was confirmed by single crystal X-ray diffraction. The absolute configurations of 1 and 2 were deduced by comparison of CD spectra with the known alkaloid sinomenine (3). Compound 1 was tested for DPPH inhibition and gave IC(50) of 27.9 μM. Compound 2 was tested for neuroprotective effect and showed significant activity against β-amyloid(25-35)-induced oxidative injury (*P < 0.05) at 10 μM in PC-12 cells.