Hitoyol A and B, Two Norsesquiterpenoids from the Basidiomycete Coprinopsis cinerea

Norditerpenoids biosynthesized by variediene synthase-associated P450 machinery along with modifications by the host cell Aspergillus oryzae

The chemical diversity of terpenoids is typically established by terpene synthase-catalyzed cyclization and diversified by post-tailoring modifications. Fungal bifunctional terpene synthase (BFTS) associated P450 enzymes have shown significant catalytic potentials through the development of various new terpenoids with different biological activities. This study discovered the BFTS and its related gene cluster from the plant endophytic fungus Didymosphaeria variabile 17020. Heterologous expression of the BFTS in Saccharomyces cerevisiae resulted in the characterization of a major product diterpene variediene (1), along with two new minor products neovariediene and neoflexibilene. Further heterologous expression of the BFTS and one cytochrome P450 enzyme VndE (CYP6138B1) in Aspergillus oryzae NSAR1 led to the identification of seven norditerpenoids (19 carbons) with a structurally unique 5/5 bicyclic ring system. Interestingly, in vivo experiments suggested that the cyclized terpene variediene (1) was modified by VndE along with the endogenous enzymes from the host cell A. oryzae through serial chemical conversions, followed by multi-site hydroxylation via A. oryzae endogenous enzymes. Our work revealed that the two-enzymes biosynthetic system and host cell machinery could produce structurally unique terpenoids.

Enyne diketones as substrate in asymmetric Nazarov cyclization for construction of chiral allene cyclopentenones

The Nazarov cyclization is one of the most powerful tools for the stereoselective synthesis of various cyclopentenone scaffolds. Therefore, developing the new classes substrate of Nazarov reaction is an important endeavor in synthetic chemistry. Herein, we report enyne diketones, enables diastereo- and enantioselective construction of chiral allene cyclopentenones in moderate to good yields with good enantioselectivities (up to 97% ee). Importantly, it is a typical example for asymmetric synthesis of cyclopentanones with allene moiety using Nazarov cyclisation. Mechanistic studies indicate that this metal-organo relay catalysis protocol involves a rhodium-catalyzed tandem oxonium ylide formation/[2,3]-sigmatropic rearrangement/reverse benzylic acid rearrangement, followed by organo-catalyzed asymmetric Nazarov cyclization/alkyne-to-allene isomerization to give the final chiral allene cyclopentenones.

Oxygenated Cyclopentenones via the Pauson-Khand Reaction of Silyl Enol Ether Substrates

We report here the application of silyl enol ether moieties as efficient alkene coupling partners within cobalt-mediated intramolecular Pauson–Khand reactions. This cyclization strategy delivers synthetically valuable oxygenated cyclopentenone products in yields of ≤93% from both ketone- and aldehyde-derived silyl enol ethers, incorporates both terminal and internal alkyne partners, and delivers a variety of decorated systems, including more complex tricyclic structures. Facile removal of the silyl protecting group reveals oxygenated sites for potential further elaboration.

Sesquiterpenoids Specially Produced by Fungi: Structures, Biological Activities, Chemical and Biosynthesis (2015-2020)

Fungi are widely distributed in the terrestrial environment, freshwater, and marine habitat. Only approximately 100,000 of these have been classified although there are about 5.1 million characteristic fungi all over the world. These eukaryotic microbes produce specialized metabolites and participate in a variety of ecological functions, such as quorum detection, chemical defense, allelopathy, and maintenance of symbiosis. Fungi therefore remain an important resource for the screening and discovery of biologically active natural products. Sesquiterpenoids are arguably the richest natural products from plants and micro-organisms. The rearrangement of the 15 high-ductility carbons gave rise to a large number of different skeletons. At the same time, abundant structural variations lead to a diversification of biological activity. This review examines the isolation, structural determination, bioactivities, and synthesis of sesquiterpenoids that were specially produced by fungi over the past five years (2015-2020).

Fungi: outstanding source of novel chemical scaffolds

A large number of remarkable studies on the secondary metabolites of fungi have been conducted in recent years. This review gives an overview of one hundred and sixty-seven molecules with novel skeletons and their bioactivities that have been reported in seventy-nine articles published from 2013 to 2017. Our statistical data showed that endophytic fungi and marine-derived fungi are the major sources of novel bioactive secondary metabolites.

Productivity and bioactivity of enokipodins A-D of Flammulina rossica and Flammulina velutipes

Enokipodins are antimicrobial sesquiterpenes produced by Flammulina velutipes in a mycelial culture medium. To date, enokipodin production has not been reported in other members of the genus Flammulina. Hence, in this study, the production of enokipodins A, B, C, and D by F. velutipes and F. rossica was investigated. Some strains of F. rossica were confirmed to produce at least one of the four enokipodins in the culture medium. However, some strains of F. velutipes did not produce any of the enokipodins. In an antibacterial assay using liquid medium, enokipodin B showed the strongest growth inhibitory activity against Bacillus subtilis among the four types of enokipodins. Enokipodin B inhibited the spore germination of some plant pathogenic fungi. Enokipodins B and D exerted moderate anti-proliferative activity against some cancer cell lines, and enokipodins A and C inhibited the proliferation of the malarial parasite, Plasmodium falciparum.

Genomic Mushroom Hunting Decrypts Coprinoferrin, A Siderophore Secondary Metabolite Vital to Fungal Cell Development

LaeA is a positive global regulator of secondary metabolism in Ascomycetes, but its role in Basidiomycetes, including medicinal mushrooms, remains uncharacterized. Here, knockout of laeA in the model mushroom Coprinopsis cinerea unexpectedly upregulated the biosynthesis of a novel siderophore, coprinoferrin. Furthermore, knockout of the nonribosomal peptide synthetase-encoding cpf1 responsible for coprinoferrin biosynthesis resulted in growth defect and loss of fruiting body formation, indicating the complex role that this natural product plays in fungal cell development.

Palladium-catalyzed cascade carboesterification of norbornene with alkynes

An efficient and convenient palladium-catalyzed cascade carboesterification of norbornenes (NBE) with alkynes has been accomplished to afford functionalized α-methylene γ-lactone and tetrahydrofuran derivatives in good to excellent yields. This new strategy exhibits excellent atom- and step-economy, good functional group tolerance and broad substrate scope. In particular, NBE-palladium species was proposed to be the key intermediate in the catalytic cycle to suppress the β-H elimination process. Notably, the developed protocol provides a straightforward and practical tool for the construction of diverse oxygen-containing heterocycle frameworks, illustrating a promising application in synthetic and pharmaceutical chemistry.

Biological and chemical diversity go hand in hand: Basidiomycota as source of new pharmaceuticals and agrochemicals

The Basidiomycota constitutes the second largest higher taxonomic group of the Fungi after the Ascomycota and comprises over 30.000 species. Mycelial cultures of Basidiomycota have already been studied since the 1950s for production of antibiotics and other beneficial secondary metabolites. Despite the fact that unique and selective compounds like pleuromutilin were obtained early on, it took several decades more until they were subjected to a systematic screening for antimicrobial and anticancer activities. These efforts led to the discovery of the strobilurins and several hundreds of further compounds that mainly constitute terpenoids. In parallel the traditional medicinal mushrooms of Asia were also studied intensively for metabolite production, aimed at finding new therapeutic agents for treatment of various diseases including metabolic disorders and the central nervous system. While the evaluation of this organism group has in general been more tedious as compared to the Ascomycota, the chances to discover new metabolites and to develop them further to candidates for drugs, agrochemicals and other products for the Life Science industry have substantially increased over the past decade. This is owing to the revolutionary developments in -OMICS techniques, bioinformatics, analytical chemistry and biotechnological process technology, which are steadily being developed further. On the other hand, the new developments in polythetic fungal taxonomy now also allow a more concise selection of previously untapped organisms. The current review is dedicated to summarize the state of the art and to give an outlook to further developments.

Biosynthesis of lagopodins in mushroom involves a complex network of oxidation reactions

Targeted gene knockout in Coprinopsis cinerea, yeast in vivo bioconversion and in vitro assays elucidated the lagopodin biosynthetic pathway, including a complexity-generating network of oxidation steps.

Survey of natural products reported by Asian research groups in 2017

The new natural products reported in 2017 in peer-reviewed articles in journals with good reputations were reviewed and analyzed. The advances made by Asian research groups in the field of natural products chemistry in 2017 were summarized. Compounds with unique structural features and/or promising bioactivities originating from Asian natural sources were discussed based on their structural classification.

Hot off the Press

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as caesalpinflavin A from Caesalpinia enneaphylla.