Undescribed polyketides from endophytes associated with the critically endangered conifer Abies beshanzuensis.

Four undescribed polyketides, beshanzones A (1) and B (2) as well as beshanhexanols A (3) and B (4), along with three known ones (5-7) were isolated from the rice fermentation of two endophytic fungi associated with the critically endangered Chinese endemic conifer Abies beshanzuensis. γ-Butyrolactone derivatives 1, 2, and 5 were isolated from Phomopsis sp. BSZ-AZ-2, an interesting strain that drawn our attention this time. The cyclohexanol derivatives 3, 4, 6, and 7 were obtained during a follow-up investigation on Penicillium commune BSZ-P-4-1. The chemical structures including absolute configurations of compounds 1-4 were determined by spectroscopic methods, Mo2(OAc)4 induced electronic circular dichroism (IECD), GIAO NMR calculations and DP4+ probability analyses. In particular, compound 2 contains a novel 5/5 bicyclic ring system, which might be biogenetically derived from the known compound 5 through hydrolysis followed by an Aldol reaction. All isolates were evaluated for their antimicrobial activities against a small panel of bacterial and fungal pathogens. Compounds 6 and 7 showed moderate inhibitory activities against Candida albicans, with MIC values of 16 and 32 µg/mL, respectively.

"One pot" synthesis of quinazolinone-[2,3]-fused polycyclic scaffolds in a three-step reaction sequence.

Diverse quinazolinone-[2,3]-fused polycyclic skeletons occupy a prominent position in drug discovery. Even with currently available methods there still remain unmet needs for flexible access to such structures. Herein, we have explored a mild "one pot" procedure for the construction of various quinazolinone-[2,3]-fused polycycles. The procedure involves Pd-catalyzed carbonylation of N-(2-iodophenyl)acetamides, release of the masked terminal amine, and two sequential and spontaneous cyclizations. This generally applicable approach features easy assembly of precursors from readily available starting materials, mild reaction conditions, non-cumbersome operation, and polycyclic diversity.

Construction of indolizine scaffolds from α,ω-alkynoic acids and α,ω-vinylamines via sequential-relay catalysis in "one pot".

A simple and efficient method has been developed for the synthesis of a diverse range of aryl-fused indolizin-3-ones through sequential Au(I)-catalyzed hydrocarboxylation, aminolysis, and cyclization, followed by ruthenium-catalyzed ring-closing metathesis. Moderate to good yields were observed with satisfactory substrate scope and functional group tolerance. The developed protocol represents a practical strategy for the construction of bioactive aryl-fused indolizin-3-ones.

Terricoxanthones A-E, unprecedented dihydropyran-containing dimeric xanthones from the endophytic fungus Neurospora terricola HDF-Br-2 associated with the vulnerable conifer Pseudotsuga gaussenii.

An investigation on the secondary metabolites from a rice culture broth of the endophytic fungus Neurospora terricola HDF-Br-2 derived from the vulnerable conifer Pseudotsuga gaussenii led to the isolation and characterization of 34 structurally diverse polyketides (1-34). Seven of them are previously undescribed, including five unprecedented dihydropyran-containing (terricoxanthones A-E, 1-5, resp.) and one rare tetrahydrofuran-containing (terricoxanthone F, 6) dimeric xanthones. The structures were elucidated by spectroscopic methods and single-crystal X-ray diffraction analyses. Terricoxanthones each were obtained as a racemic mixture. Their plausible biosynthetic relationships were briefly proposed. Compounds 6, aspergillusone A (8), and alatinone (27) displayed considerable inhibition against Candida albicans with MIC values of 8-16 µg/mL. 4-Hydroxyvertixanthone (12) and 27 exhibited significant inhibitory activities against Staphylococcus aureus, with MIC values of 4-8 µg/mL. Furthermore, compounds 8 and 27 could disrupt biofilm of S. aureus and C. albicans at 128 µg/mL. The findings not only extend the skeletons of xanthone dimers and contribute to the diversity of metabolites of endophytes associated with the endangered Chinese conifer P. gaussenii, but could further reveal the important role of protecting plant species diversity in support of chemical diversity and potential sources of new therapeutics.

Synthesis, biological evaluation, and molecular modeling of ORM-10921 and its analogs as α2C -adrenoceptor antagonists.

The α2C -adrenoceptor (α2C -AR) is regarded as one of the potential targets for antipsychotics. A few of structurally diverse α2C -AR antagonists have been reported, among which ORM-10921, containing one rigid tetracyclic framework with two neighboring chiral centers, has exhibited remarkable antipsychotic-like effects and pro-cognitive properties in different animal models. Yet the binding mode of ORM-10921 remains elusive. In this study, all of its four stereoisomers and a set of its analogs were synthesized and in vitro evaluated for their α2C -AR antagonist activities. The molecular docking study and hydration site analysis gave a rational explanation for the biological results, which might provide helpful insights into the binding mode and future optimization.

Identification and immunological evaluation of novel TLR2 agonists through structural optimization of Diprovocim.

As an important family member of Toll-like receptors (TLRs), TLR2 can recognize various pathogen-associated molecular patterns (PAMPs) such as bacteria and viral components. Accumulating evidence demonstrates that TLR2 agonists play a critical role in cancer immunotherapy and infectious diseases. Diprovocim is the most potent small molecule TLR2 agonist known, showing remarkably immune adjuvant activity in mice. However, the further clinical research and development of Diprovocim was hampered because of its structural complexity as well as high molecular weight. Here, we designed and synthesized 21 structurally simplified derivatives of Diprovocim, performed their TLR2 agonistic activities by HEK-Blue hTLR2 SEAP assay, and evaluated the toxicity in two human normal cell lines. Compounds B3-B4 and B9-B12 with excellent TLR2 agonistic activity were found through the structure-activity relationship study. Among them, diastereomer B10 and B12 substituted (S)-2-phenylcyclopropylamide side chain of Diprovocim with simple (R)- and (S)-n-butyl groups exhibited comparable TLR2 agonistic activities with EC50 values of 35 nM and 39 nM, respectively. ELISA and western blot experiments on THP-1 cells showed that B10 and B12 displayed remarkable immunostimulatory activity in the release of various inflammatory cytokines through activating MyD88-dependent NF-κB and MAPK signaling pathways. Importantly, B10 and B12 have less structural complexity and better safety compared to Diprovocim, and the chiral center of right pyrrolidine ring has negligible influence on TLR2 activition. Our study provides simplified Diprovocim derivatives with high agonistic activity, providing a clue to further optimize Diprovocim.

Synthesis of the analogs of plocabulin and their preliminary structure-activity relationship study.

Plocabulin, a marine natural polyketide isolated from the sponge Lithoplocamia lithistoides, is a novel and potent microtubule-destabilizing agent. Guided by the reported binding mode, several new analogs of plocabulin have been designed through removing the right aliphatic chain and further modifying on the carbamate group and the enamide unit. The preliminary results indicate that the right aliphatic chain in plocabulin is allowed to remove with a little loss of activity, the carbamate group plays a role in the activity, and particularly, the enamide unit has an important effect on the activity. This new finding will aid the design of novel potent tubulin-binding agents based on plocabulin.

Unexpected Enhancement of HDACs Inhibition by MeS Substitution at C-2 Position of Fluoro Largazole.

Given our previous finding that fluorination at the C18 position of largazole showed reasonably good tolerance towards inhibitory activity and selectivity of histone deacetylases (HDACs), further modification on the valine residue in the fluoro-largazole's macrocyclic moiety with S-Me l-Cysteine or Glycine residue was performed. While the Glycine-modified fluoro analog showed poor activity, the S-Me l-Cysteine-modified analog emerged to be a very potent HDAC inhibitor. Unlike all previously reported C2-modified compounds in the largazole family (including our recent fluoro-largazole analogs) where replacement of the Val residue has failed to provide any potency improvement, the S-Me l-Cysteine-modified analog displayed significantly enhanced (five-nine-fold) inhibition of all the tested HDACs while maintaining the selectivity of HDAC1 over HDAC6, as compared to largazole thiol. A molecular modeling study provided rational explanation and structural evidence for the enhanced inhibitory activity. This new finding will aid the design of novel potent HDAC inhibitors.

A fluorine scan on the Zn2+-binding thiolate side chain of HDAC inhibitor largazole: Synthesis, biological evaluation, and molecular modeling.

Based on the unique role of a common unit in a family of sulfur-containing natural histone deacetylases (HDACs) inhibitors, we have chosen largazole as an example of these inhibitors and adopted a "fluorine scan" strategy towards modification of this common unit. Thus a set of fluoro largazole analogues has been designed, synthesized and evaluated in enzymatic as well as cellular assays. The preliminary results indicate that introduction of fluorine at the various position of the unit has an important impact on the activity and selectivity of HDACs. Unlike other modifications which often led to significant reduction or complete loss of activity as reported in the literature, most of these fluoro thiols have displayed comparable or enhanced activity and selectivity in enzymatic assays. Two of the sulfhydryl esters have also exhibited excellent inhibitory activity in cellular assays with a few selected cell lines. The C19-fluorinated analogue has been further studied by immunoblot analysis, confirming that it is a potent selective class I HDAC inhibitor and supporting that the potent cellular antiproliferative activity is due to HDAC inhibition. The molecular docking study reveals that introducing fluorine at the C19 position does not change the original interactions, but might have made a subtle change in binding conformation, resulting in an obvious improvement in activity.

Synthesis and Preliminary Biological Evaluation of Two Fluoroolefin Analogs of Largazole Inspired by the Structural Similarity of the Side Chain Unit in Psammaplin A.

Largazole, isolated from a marine Cyanobacterium of the genus Symploca, is a potent and selective Class I HDAC (histone deacetylation enzymes) inhibitor. This natural 16-membered macrocyclic depsipeptide features an interesting side chain unit, namely 3-hydroxy-7-mercaptohept-4-enoic acid, which occurs in many other natural sulfur-containing HDAC inhibitors. Notably, one similar fragment, where the amide moiety replaces the trans alkene moiety, appears in Psammaplin A, another marine natural product with potent HDAC inhibitory activities. Inspired by such a structural similarity, we hypothesized the fluoroolefin moiety would mimic both the alkene moiety in Largazole and the amide moiety in Psammaplin A, and thus designed and synthesized two novel fluoro olefin analogs of Largazole. The preliminary biological assays showed that the fluoro analogs possessed comparable Class I HDAC inhibitory effects, indicating that this kind of modification on the side chain of Largazole was tolerable.

Discovery, synthesis, biological evaluation and molecular docking study of (R)-5-methylmellein and its analogs as selective monoamine oxidase A inhibitors.

(R)-5-Methylmellein (5-MM), the major ingredient in the fermented mycelia of the medicinal fungus Xylaria nigripes (called Wuling Shen in Chinese)¸ was found to be a selective inhibitor against monoamine oxidase A (MAO-A) and might play an important role in the clinical usage of this edible fungus as an anti-depressive traditional Chinese medicine (TCM). Based on the discovery and hypothesis, a variety of (R)-5-MM analogs were synthesized and evaluated in vitro against two monoamine oxidase isoforms (MAO-A and MAO-B). Most synthetic analogs showed selective inhibition of MAO-A with IC50 values ranging from 0.06 to 29 µM, and compound 13aR is the most potent analog with high selectivity (IC50, MAO-A: 0.06 µM; MAO-B: >50 µM). Interestingly, the enzyme kinetics study of 13aR indicated that this ligand seemed to bind in the MAO-A active site according to so-called "tight-binding inhibition" mode. The molecular docking study of 13aR was thereafter performed in order to rationalize the obtained biological results.

Cs2CO3-promoted defluorination and functionalization of α-CF3 carbonyl compounds in the presence of N-, O-, and/or S-nucleophiles.

A simple, efficient, and mild method for defluorination and functionalization of 3,3,3-trifluoro carbonyl compounds has been developed. In the present method, Cs2CO3 can easily convert α-trifluoromethyl esters, amides, and ketones into ß,ß-S-, O- and/or N-substituted α,ß-unsaturated carbonyl compounds in the presence of N-, O-, and S-nucleophiles with moderate to excellent yields, and furthermore, this transformation with α-trifluoromethyl ester and a series of 2-aminophenols can result in benzooxazoles in good yields.

The flavonoid TL-2-8 induces cell death and immature mitophagy in breast cancer cells via abrogating the function of the AHA1/Hsp90 complex.

The flavonoid quercetin exhibits significant anticancer activities with few side effects. In the current study, we characterized TL-2-8, a quercetin derivative, as a novel anticancer agent in vitro and in vivo. Cell proliferation and viability were assessed using Cell Counting Kit-8 and CellTiter-Blue assay, respectively. Cell death was examined using PI staining or a TUNEL assay. Mitophagy was determined by measuring autophagic flux and by confocal imaging. Protein expression was examined by Western blotting. We found that TL-2-8 selectively inhibited the proliferation and decreased the viability of various cancer cells (the anti-proliferation IC50 values in MDA-MB-231, MDA-MB-468 and MCF-7 breast cancer cells at 72 h were 8.28, 8.56, and 9.58 µmol/L, respectively), and it displayed only slight cytotoxicity against normal MCF-10A and HEK-293 cells. In MDA-MB-231 and MDA-MB-468 breast cancer cells, TL-2-8 treatment induced the degradation of multiple Hsp90 client proteins without inducing Hsp70. TL-2-8 (3, 6, 12 µmol/L) dose-dependently inhibited the expression of AHA1, an activator of Hsp90 ATPase, and decreased Hsp90-AHA1 complex formation, leading to decreased Hsp90 chaperone function and reduced polo-like kinase 1 (PLK1) signaling. Consequently, impaired mitophagy was induced via the downregulation of lysosomal-associated membrane protein 2 (LAMP2). The in vivo anticancer effects of TL-2-8 were evaluated in an MDA-MB-231 breast cancer xenograft model, which was treated with TL-2-8 (25, 50, 100 mg·kg-1·d-1, po). Administration of TL-2-8 resulted in tumor growth inhibition rates of 37.9%, 58.9% and 70.9%, respectively, whereas quercetin treatment (100 mg·kg-1·d-1, po) produced only a lower tumor growth inhibition rate (49.5%). Furthermore, TL-2-8 treatment significantly extended the lifespan of mice bearing MDA-MB-231 breast cancer cell xenografts. Our results demonstrate that TL-2-8 induces significant cell death and immature mitophagy in breast cancer cells in vitro and in vivo via AHA1 abrogation.

Synthesis of ∆3-2-hydroxybakuchiol analogues and their growth inhibitory activity against rat UMR106 cells.

A series of ∆3-2-hydroxybakuchiol analogues have been synthesized and tested for their growth inhibitory activity against rat UMR106 cells by using the MTT method. Some of them exhibit enhanced activities compared with the natural product, and the preliminary SAR profile shows that the chain tail on the natural product could be subtly modified to enhance the activity and the aromatic moiety or the terminal olefin on the main chain can also be modified without any evident loss of activity. The stereo-configuration of the quaternary chiral center has an important influence on the activity.

Discovery and synthesis of novel luteolin derivatives as DAT agonists.

Luteolin, 5,7-dihydroxy-2-(3,4-dihydroxyphenyl)-4H-chromen-4-one, has been proposed and proved to be a novel dopamine transporter (DAT) activator. In order to develop this potential of luteolin, a series of novel luteolin derivatives were designed, synthesized, and evaluated for their DAT agonistic activities, utilizing constructed Chinese hamster ovary (CHO) cell lines stably expressing rat DAT. Biological screening results demonstrated that luteolin derivatives 1d, 1e, and 4c carry great DAT agonistic potency (EC(50)=0.046, 0.869, and 1.375µM, respectively) compared with luteolin 8 (EC(50)=1.45±0.29µM). Luteolin derivative 1d, notably, exhibited a 32-fold-higher DAT agonistic potency than luteolin. These luteolin derivatives represent a novel DAT agonist class, from which lead compounds useful for exploration of additional novel DAT agonists could be drawn.

First stereospecific synthesis of (E)- or (Z)-alpha-fluoroenones via a kinetically controlled Negishi coupling reaction.

A highly stereospecific synthesis of (E)- or (Z)-alpha-fluoro-alpha,beta-unsaturated ketones 4, via a kinetically controlled Negishi palladium-catalyzed coupling reaction, was developed, providing an easy and general access to valuable fluorinated intermediates (pharmaceutical, peptide mimic, and so on). The synthesis involved a reaction between E/Z gem-bromofluoroolefins 2 and alkoxyvinylzinc species 6 under controlled reaction temperature. At 10 degrees C, (Z)-4 (70 to 99% yields) was obtained along with unreacted (Z)-2 (66 to 99% yields). At THF reflux, the recovered olefin was transformed into (E)-4 (up to 98% yield).

A novel diastereoselective synthesis of (Z)-fluoroalkenes via a Nozaki-Hiyama-Kishi-type reaction.

A highly diastereoselective and straightforward synthesis for (Z)-2-fluoroallylic alcohols via a Nozaki-Hiyama-Kishi-type reaction with the corresponding bromofluoroolefins was developed, providing an easy access to highly interesting fluorinated synthons.

A facile and mild method for the synthesis of terminal bromofluoroolefins via diethylzinc-promoted Wittig reaction.

[reaction: see text] Synthesis of 1-bromo-1-fluoroolefins was achieved in good yields via a Wittig reaction promoted by diethylzinc, even with nonactivated aldehydes and ketones as starting materials.