Biomimetic Total Synthesis of (+)-Chabranol

Biomimetic Synthesis of Biologically Active Natural Products: An Updated Review

BACKGROUND

Natural products have optical activities with unusual structural characteristics or specific stereoselectivity, mostly including spiro-ring systems or quaternary carbon atoms. Expensive and time-consuming methods for natural product purification, especially natural products with bioactive properties, have encouraged chemists to synthesize those compounds in laboratories. Due to their significant role in drug discovery and chemical biology, natural products have become a major area of synthetic organic chemistry. Most medicinal ingredients available today are healing agents derived from natural resources, such as plants, herbs, and other natural products.

METHODS

Materials were compiled using the three databases of ScienceDirect, PubMed, and Google Scholar. For this study, only English-language publications have been evaluated based on their titles, abstracts, and full texts.

RESULTS

Developing bioactive compounds and drugs from natural products has remained challenging despite recent advances. A major challenge is not whether a target can be synthesized but how to do so efficiently and practically. Nature has the ability to create molecules in a delicate but effective manner. A convenient method is to imitate the biogenesis of natural products from microbes, plants, or animals for synthesizing natural products. Inspired by the mechanisms occurring in the nature, synthetic strategies facilitate laboratory synthesis of natural compounds with complicated structures.

CONCLUSION

In this review, we have elaborated on the recent syntheses of natural products conducted since 2008 and provided an updated outline of this area of research (Covering 2008-2022) using bioinspired methods, including Diels-Alder dimerization, photocycloaddition, cyclization, and oxidative and radical reactions, which will provide an easy access to precursors for biomimetic reactions. This study presents a unified method for synthesizing bioactive skeletal products.

Structure-Based Molecular Networking for the Discovery of Anti-HBV Compounds from Saussurea lappa (Decne.) C.B Clarke

It is a crucial to find target compounds in natural product research. This study presents a concept of structure-guided isolation to find candidate active molecules from herbs. We establish a process of anti-viral sesquiterpene networking. An analysis of the networking suggested that new anti-HBV sesquiterpene may be attributable to eudesmane-, guaiane-, cadinane-, germacane- and bisabolane-type sesquiterpenes. In order to evaluate the efficiency of the structure-based molecular networking, ethanol extract of Saussurea lappa (Decne.) C.B Clarke was investigated, which led to the isolation of two guaiane-type (1 and 14), ten eudesmane-type (2–5 and 8–13), two chain (6 and 7) and one germacrane-type (15) sesquiterpenes, including seven new ones, lappaterpenes A–G (1–7), which are reported on herein. The absolute configurations of the new compounds were established by coupling constants, calculated ECD and ROESY correlations, as well as comparisons of optical rotation values with those of known compounds. The absolute configuration of compound 2 was further confirmed by X-ray diffraction. Compounds 1–15 were evaluated for their potency against hepatitis B virus. Compounds 4, 6, 7 and 9 showed effect on HBsAg with inhibition ratios of more than 40% at 30 μM concentrations. Compounds 14 and 15 inhibited HBsAg secretion with the values of IC₅₀ 0.73 ± 0.18 and 1.43 ± 0.54 μM, respectively. Structure-based molecular networking inspired the discovery of target compounds.

Eighteen structurally diversified sesquiterpenes isolated from Pogostemon cablin and their inhibitory effects on nitric oxide production

Five new sesquiterpenes, namely, guaianes A-E (1-5), including one novel carbon skeleton guaiane-type sesquiterpene derivatives (1), together with thirteen known compounds (6-18), were isolated from the aerial parts of Pogostemon cablin (Blanco.) Benth. Their chemical structures were mainly established through the relative spectroscopic data, while the absolute configurations of compounds 1-5 were elucidated on the base of single-crystal X-ray diffraction analysis and electronic circular dichroism (ECD) calculations. All compounds were tested for their inhibiting effects on NO production in LPS-stimulated BV2 microglia cells as well as the cell viabilities. The results showed that compounds 2-16 and 18 possessed moderately anti-inflammatory activities at a concentration of 50 μM.

Total synthesis of conosilane A via a site-selective C–H functionalization strategy

The strategy developed for the first total synthesis of highly oxygenated natural product conosilane A involving double manipulation of allylic C(sp³)–H functionalization renders the power of C–H functionalization in organic syntheses.

Bioinspired total synthesis of (−)-gymnothelignan L

The first asymmetric total synthesis of gymnothelignan L has been accomplished in 14 steps with 11.2% overall yield. The synthetic approach features an anti Evans aldol reaction, a diastereoselective methylation, a Suzuki–Miyaura coupling and a bioinspired desymmetric transannular Friedel–Crafts reaction.

Bismuth(iii) triflate-catalysed tandem cyclisations towards complex polycyclic ethers

A series of complex polycyclic ethers have been synthesised under very mild conditions using a low catalyst loading of bismuth(iii) triflate.

Antitumour effect of sesquiterpene (+)-chabranol on four human cancer cell lines by inducing apoptosis and autophagy

OBJECTIVE

To investigate the effects and mechanisms of sesquiterpene (+)-chabranol on proliferation of a panel of four human tumour cell lines (BGC-823, SGC-7901, SSMC-7721 and HepG2).

METHODS

Cell viability was assessed using a standard methyltetrazolium assay; cell-cycle analysis of BGC-823 cells was performed by flow cytometry. Transmission electron microscopy (TEM) was used to examine the ultrastructure of BGC-823 cells exposed to (+)-chabranol. Apoptosis was investigated by evaluating DNA laddering, using gel electrophoresis.

RESULTS

(+)-Chabranol had a marked time- and concentration-dependent inhibitory effect on BGC-823 cell proliferation. The effect was less marked in SGC-7901, SSMC-7721 and HepG2 cells. Exposure of BGC-823 cells to (+)-chabranol arrested the cell cycle at G(1). Evidence of apoptosis and autophagy was observed by TEM; DNA laddering in BGC-823 cells supported the presence of apoptosis.

CONCLUSIONS

This study suggested that (+)-chabranol has antitumour activity against BGC-823 cells, and may exert its action by inhibition of proliferation and induction of apoptosis and autophagy. With further development, (+)-chabranol may represent a potential novel treatment for poorly differentiated gastric cancer.

Marine natural products

Covering: 2010. Previous review: Nat. Prod. Rep., 2011, 28, 196. This review covers the literature published in 2010 for marine natural products, with 895 citations (590 for the period January to December 2010) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1003 for 2010), together with the relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.