Cryptic piperazine derivatives activated by knocking out the global regulator LaeA in Aspergillus flavipes.

Genome sequencing on an intertidal zone-derived Aspergillus flavipes strain revealed its great potential to produce secondary metabolites. To activate the cryptic compounds of A. flavipes, the global regulator flLaeA was knocked out, leading to substantial up-regulation of the expression of two NRPS-like biosynthetic gene clusters in the ΔflLaeA mutant. With a scaled-up fermentation of the ΔflLaeA strain, five compounds, including two previously undescribed piperazine derivatives flavipamides A and B (1 and 2), along with three known compounds (3-5), were obtained by LC-MS guided isolation. The new compounds were elucidated by spectroscopic analysis and electronic circular dichroism (ECD) calculations, and the biosynthetic pathway was proposed on the bias of bioinformatic analysis and 13C isotope labeling evidence. This is the first report to access cryptic fungi secondary metabolites by inactivating global regulator LaeA and may provide a new approach to discovering new secondary metabolites by such genetic manipulation.

Synthesis of portimines reveals the basis of their anti-cancer activity.

Marine-derived cyclic imine toxins, portimine A and portimine B, have attracted attention because of their chemical structure and notable anti-cancer therapeutic potential1-4. However, access to large quantities of these toxins is currently not feasible, and the molecular mechanism underlying their potent activity remains unknown until now. To address this, a scalable and concise synthesis of portimines is presented, which benefits from the logic used in the two-phase terpenoid synthesis5,6 along with other tactics such as exploiting ring-chain tautomerization and skeletal reorganization to minimize protecting group chemistry through self-protection. Notably, this total synthesis enabled a structural reassignment of portimine B and an in-depth functional evaluation of portimine A, revealing that it induces apoptosis selectively in human cancer cell lines with high potency and is efficacious in vivo in tumour-clearance models. Finally, practical access to the portimines and their analogues simplified the development of photoaffinity analogues, which were used in chemical proteomic experiments to identify a primary target of portimine A as the 60S ribosomal export protein NMD3.

K2S2O8-Mediated Radical Cyclization of 1,6-Enyne for the Synthesis of Diiodonated γ-Lactams.

A novel and convenient K2S2O8-mediated diiodo cyclization of 1,6-enynes for the facile synthesis of functionalized γ-lactam derivatives has been developed. This reaction features mild and transition-metal-free conditions, which offer a green and efficient entry to synthetically important γ-lactam scaffolds. Mechanistic studies suggest that iodide radicals initiate the cascade cyclic transformation.

Silver(I)-Catalyzed Oxidative Cyclopropanation of 1,6-Enynes: Synthesis of 3-Aza-bicyclo[3.1.0]hexane Derivatives.

A simple Ag(I)-catalyzed oxidative cyclopropanation of heteroatom-tethered 1,6-enynes for the establishment of valuable functionalized 3-aza-bicyclo[3.1.0]hexane is presented, which allows the formation of multiple chemical bonds in one step under 20 mol % silver(I) catalysts and air conditions. This approach is highly atom economical, easy to perform, and free of external oxidants and features good to excellent yields and gram-scale synthesis. The preliminary study showed that an uncommon silver carbenoid intermediate might be involved in this process.

A Removable Acyl Group Promoted the Intramolecular Dehydro-Diels-Alder Reaction of Styrene-Ynes: Highly Chemoselective Synthesis of Aryldihydronaphthalene Derivatives.

A removable acyl group promoted the intramolecular didehydro-Diels-Alder reaction of styrene-ynes under mild reaction conditions is proposed. The reaction is free of metals and catalysts, is easy to perform, and exhibits good functional group tolerance, providing a highly chemoselective approach for obtaining the valuable aryldihydronaphthalene derivatives.

Methyl 6-O-cinnamoyl-α-d-glucopyranoside Ameliorates Acute Liver Injury by Inhibiting Oxidative Stress Through the Activation of Nrf2 Signaling Pathway.

Excessive stimulation of hepatotoxins and drugs often lead to acute liver injury, while treatment strategies for acute liver injury have been limited. Methyl 6-O-cinnamoyl-α-d-glucopyranoside (MCGP) is a structure modified compound from cinnamic acid, a key chemical found in plants with significant antioxidant, anti-inflammatory, and antidiabetic effects. In this study, we investigated the effects and underlying mechanisms of MCGP on acetaminophen (APAP)- or carbon tetrachloride (CCl4)-induced acute liver injury. As a result, MCGP inhibited cell death and apoptosis induced by APAP or CCl4, and suppressed the reactive oxygen species (ROS) generation stimulated by H2O2 in liver AML12 cells. In vivo, MCGP alleviated APAP/CCl4-induced hepatic necrosis and resumed abnormal aminotransferase activities and liver antioxidase activities. In addition, MCGP depressed APAP- or CCl4-induced oxidative stress through the suppression of CYP2E1 and activation of nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway. MCGP also enhanced the number of PCNA-positive hepatocytes, increased hepatic PCNA and Bcl-XL, and decreased BAX expression in APAP-/CCl4-intoxicated mice. Furthermore, MCGP activated the GSDMD-N/cleaved caspase 1 pathway. In summary, MCGP might act as a potential therapeutic drug against drug-induced and chemical-induced acute liver injuries, and its underlying mechanisms might engage on the pressing of oxidative stress, refraining of hepatocyte apoptosis, and facilitating of liver regeneration.

A mild tetradehydro-Diels-Alder reaction of aryldiyne compounds affords exclusively linear products.

The thermal tetradehydro-Diels-Alder (TDDA) reaction for the synthesis of polysubstituted aromatic compounds remains underestimated probably due to the harsh conditions and multiproduct results. Herein, a mild intramolecular TDDA reaction of aryldiyne compounds is presented with linear naphthalenes only, exhibiting good functional group tolerance. The reaction is easy to operate and amenable to multigram-scale synthesis. From the preliminary work, it was found that the mild conditions may be the key to the completely linear product in the reactions.

Unprecedented polycyclic polyprenylated acylphloroglucinols with anti-Alzheimer's activity from St. John's wort.

Hyperforones A-J (1-10), ten degraded and reconstructed polycyclic polyprenylated acylphloroglucinols (PPAPs) with six different types of unusual architectures, were isolated from Hypericum perforatum (St. John's wort). Compound 1 is characterized by an unprecedented 1,5-epoxyfuro[3',4':1,5]cyclopenta[1,2-c]oxecine ring system; compounds 2 and 3 represent the first PPAPs with a contracted B-ring leading to the unique 5/5 core skeletons; compound 4, a proposed biosynthetic precursor of 2, is defined by an oxonane-2,7-dione architecture; compound 5 features an unusual spiro[furo[3',4':1,5]cyclopenta[1,2-b]oxepine-3,2'-oxetane] ring system; compounds 6-8 possess a rare macrocyclic lactone ring in addition to the newly formed C-ring; and compounds 9 and 10 contain a newly formed six-membered C-ring, which constructed the unexpected 6/6 scaffold with the B-ring. Hypothetic biosynthetic pathways to generate these scaffolds starting from the classic [3.3.1]-type PPAPs helped to elucidate their origins and validate their structural assignments. Compounds 4 and 6 simultaneously displayed notable activation of PP2A (EC50: 258.8 and 199.0 nM, respectively) and inhibition of BACE1 in cells (IC50: 136.2 and 98.6 nM, respectively), and showed better activities than the positive controls SCR1693 (a PP2A activator, EC50: 413.9 nM) and LY2811376 (a BACE1 inhibitor, IC50: 260.2 nM). Furthermore, compound 6 showed better therapeutic effects with respect to the reduction of pathological and cognitive impairments in 3 × Tg AD mice than LY2811376. Compound 6 represents the first multitargeted natural product that could activate PP2A and simultaneously inhibit BACE1, which highlights compound 6 as a promising lead compound and a versatile scaffold in AD drug development.

Terpene-Shikimate conjugated meroterpenoids from the endophytic fungus Guignardia mangiferae.

Nine undescribed shikimate-conjugated meroterpenes, as well as nine known compounds, were isolated from solid cultures of the fungus Guignardia mangiferae, an endophyte obtained from the leaves of Dendrobium nobile. The structures of these undescribed compounds were characterized by analyses of their 1D and 2D NMR and HRESIMS data, and their absolute configurations were assigned by single-crystal X-ray crystallography, electronic circular dichroism (ECD) calculations, modified Mosher's method, and Mo2(OCOCH3)4-induced ECD experiments. Of these compounds, mangnardone A represents the first example of terpene-shikimate-conjugated meroterpenoid with a hydroxy group at C-5. In addition, the X-ray diffraction analysis of mangnardone I is the first example to confirm the structure of bicycloalternarene (BCA) meroterpenoid by single-crystal data. Nine undescribed meroterpenes inhibited nitric oxide (NO) production in LPS-induced RAW 264.7 cells with IC50 values in the range of 4.7-40.0 µM.

Synthesis of Succinimides via Intramolecular Alder-Ene Reaction of 1,6-Enynes.

A novel and convenient method has been developed for the facile synthesis of functionalized succinimide derivatives via intramolecular Alder-ene reaction of 1,6-enynes. This reaction features mild and metal-free reaction conditions, which offers a green and efficient entry to synthetically important succinimide scaffolds. Preliminary mechanistic studies suggest that a diradical intermediate might be involved in this transformation.

Piperazine-2,5-dione derivatives and an α-pyrone polyketide from Penicillium griseofulvum and their immunosuppression activity.

Four undescribed piperazine-2,5-dione derivatives designated janthinolides C-F, and an α-pyrone-containing polyketide namely trichopyrone C, were isolated from the extract of the fungus Penicillium griseofulvum along with four known products. Among them, janthinolide C represents the first naturally occured piperazine-2,5-dione analogue featuring a cleavaged piperazinedione ring with an oxime group, while the structure of janthinolide D possesses a rare N-methoxy group in natural products. Their structures and absolute stereochemistry were elucidated based on spectroscopic data, theoretical NMR and ECD calculations, Snatzke's method, and modified Mosher's method. All compounds were evaluated for in vitro immunosuppression activity in murine splenocytes stimulated by anti-CD3/anti-CD28 mAbs, of which janthinolides B and C showed potential inhibitory activity with IC50 values at 9.3 and 1.3 µM, respectively.

Practical access to fluorescent 2,3-naphthalimide derivatives via didehydro-Diels-Alder reaction.

A practical and efficient approach for the synthesis of fluorescent 2,3-naphthalimide derivatives has been developed from readily available starting materials via an intramolecular didehydro-Diels-Alder reaction, which proceeded well under room temperature, exhibiting a wide substrate scope and good functional group tolerance. The practicability of this methodology has been verified by one-step synthesis of the environmentally sensitive fluorophore 6-DMN on a gram scale with a shorter time, fewer steps and less waste disposal, and without the utilization of toxic transition metals. The present experimental and computational studies support the crucial role of the propiolimide moiety in the transformation.

Dimericchalasine A and Amichalasines D and E: Unexpected Cytochalasan Homodimer and Heterotrimers from Aspergillus micronesiensis PG-1.

The study of Aspergillus micronesiensis led to the isolation of three unprecedented cytochalasans (1-3). Dimericchalasine A (1) is the first cytochalasan homodimer fused by a C-20/C-20' single bond. Amichalasines D (2) and E (3) represent a new type of cytochalasan heterotrimer with a decacyclic 5/6/11/5/5/6/5/12/6/5 ring system. Their structures were determined by extensive spectroscopic data and single-crystal X-ray diffraction. The plausible biosynthetic pathways of 1-3 were proposed.

Mangiterpenes A-C and 2',3'-seco-manginoid C, four sesquiterpene/monoterpene-shikimate-conjugated spirocyclic meroterpenoids from Guignardia mangiferae.

Mangiterpenes A-C and 2',3'-seco-manginoid C, four undescribed sesquiterpene/monoterpene-shikimate-conjugated meroterpenoids with spiro ring systems, were isolated from Guignardia mangiferae. The structures and absolute configurations of these compounds were established by comprehensive spectroscopic analyses and electronic circular dichroism (ECD) calculations. Mangiterpenes A-C represent the first examples of sesquiterpene-shikimate-conjugated spirocyclic meroterpenoids, and 2',3'-seco-manginoid C features an unexpected 2',3'-seco-manginoids skeleton. Mangiterpene C strongly inhibited the production of NO inducted by LPS, with an IC50 value of 5.97 µM. It showed an anti-inflammatory effect by means of blocking in the NF-κB signaling pathway and decreasing the expression of inflammatory mediators.

Hyperforatins L-U: Prenylated acylphloroglucinols with a terminal double bond from Hypericum perforatum L. (St John's Wort).

Hyperforatins L-U, ten undescribed polycyclic polyprenylated acylphloroglucinols (PPAPs) bearing a terminal double bond, together with a known compound hypericumoxide J, were isolated from the aerial parts of Hypericum perforatum L. Their structures were elucidated by spectroscopic methods, including HRESIMS, IR, UV, and NMR (1H, 13C, DEPT, HSQC, HMBC, 1H-1H COSY, and NOESY experiments). Their absolute configurations were determined by comprehensive analyses of their experimental ECD spectra in conjunction with a modified Mosher's method. Evaluation of their neuroprotective activities highlighted hyperforatin L, which displayed mild activity at a concentration of 10 µM.

Amiaspochalasins A-H, Undescribed Aspochalasins with a C-21 Ester Carbonyl from Aspergillus micronesiensis.

Amiaspochalasins A-H (1-8), eight undescribed aspochalasins, and trichalasin D (9), a known analogue, were isolated from the solid culture of Aspergillus micronesiensis. Compounds 1-9 are aspochalasins with a C-21 ester carbonyl, and their structures were determined by spectroscopic data, X-ray crystallographic analyses, electronic circular dichroism calculations, and chemical methods. The CH3-25 in compound 1 is located at C-16 rather than C-14 in the previously reported aspochalasins, endowing 1 with an unexpected carbon skeleton. Compounds 2 and 3 are the first examples of aspochalasins with an unprecedented 5/6/6/8 tetracyclic ring system. Compounds 4 and 5 are diastereomers of aspochalasins I and J, respectively. Compounds 6 and 7 are the first aspochalasins featuring a long open-chain system, and their absolute configurations were discussed by comparing the NMR data of the hydrolysis and methyl esterification products of 4 and 5. Compound 8 is an isomeride of 9. The cytotoxic and antimicrobial effects of 1-9 were tested.

Phenolic C-Glycosides and Aglycones from Marine-Derived Aspergillus sp. and Their Anti-Inflammatory Activities.

A chemical investigation of the secondary metabolites of a marine-derived Aspergillus sp. led to the isolation and characterization of 13 phenolic compounds, including 10 new compounds (1-10). Seven new compounds (1-7) are unusual phenolic C-glycosides, while the other new compounds (8-10) are structurally related aglycones. The chemical structures of these new compounds were elucidated by 1D and 2D NMR and HRESIMS spectroscopic analyses. The absolute configurations of these new C-glycosides were determined by comparison of experimental electronic circular dichroism spectra with those of calculated ones. In addition, the anti-inflammatory activities of these compounds were evaluated, and compound 9 significantly inhibited nitric oxide production with an IC50 value of 6.0 ± 0.5 µM in lipopolysaccharide-induced RAW264.7 cells. Moreover, compound 9 also showed anti-inflammatory activity by inhibiting the NF-κB-activated pathway.

Anti-Inflammatory Activities of Leaf Oil from Cinnamomum subavenium In Vitro and In Vivo.

The study determined the chemical constituents and anti-inflammatory effects of leaf oil from Cinnamomum subavenium (CS-LO) that has been used in folk medicine to treat various symptoms including inflammation. The anti-inflammatory effects of the oil were evaluated by LPS-stimulated RAW264.7 cells and the Carr-induced hind mouse paw edema model, respectively. In vitro, nitric oxide (NO), prostaglandin E2 (PGE2), TNF-α, IL-6, and IL-1ß were significantly decreased by CS-LO, and the expression of nuclear factor-κB (NF-κB) protein was blocked as well. In in vivo, the malondialdehyde (MDA) and paw edema levels were decreased by CS-LO, and the same result came up on the NO and tumor necrosis factor (TNF-a) of serum at the 5th h after Carr injection. In addition, iNOS and COX-2 immunoreactive cells of the paw tissue were decreased significantly by CS-LO (200 mg/kg) in histological examination. The present findings indicated that CS-LO have anti-inflammatory properties, and the effects might be caused through inhibiting iNOS, COX-2, TNF-α, IL-1ß, and IL-6 expression via affecting NF-κB pathway, which will provide a power scientific basis for CS-LO to be used as the treatment of inflammatory diseases.

(±)-Peniorthoesters A and B, Two Pairs of Novel Spiro-Orthoester en-antiomers With an Unusual 1,4,6-Trioxaspi-ro[4.5]decane-7-One Unit From Penicillium minioluteum.

(±)-Peniorthoesters A and B (±1 and ±2), two pairs of unprecedented spiro-orthoester enantiomers with a 1,4,6-trioxaspiro[4. 5]decane-7-one unit, were obtained from Penicillium minioluteum. Their structures were determined by spectroscopic methods, X-ray diffraction analyses, and ECD calculations. (±)-Peniorthoesters A and B are the first examples of spiro-orthoester enantiomers, and they represent the first spiro-orthoesters originating from fungi. All compounds showed potential inhibitory activities comparable to dexamethasone against NO production with IC50 values ranging from 14.2 to 34.5 µM.