Synthesis and bioactivity evaluation of pachymic acid derivatives as potential cytotoxic agents.

Pachymic acid, a well-known natural lanostane-type triterpenoid, exhibits various pharmacological properties. In this study, 18 derivatives of pachymic acid were synthesized by modifying their molecular structures and evaluated for their anticancer activity against two human cancer cell lines using the CCK-8 assay. Structure-activity relationship studies according to the in vitro cytotoxicity unexpectedly found one promising derivative A17 (namely tumulosic acid, also found in Poria cocos), which had stronger anti-proliferative activity than the positive drug cisplatin against HepG2 and HSC-2 cell lines with IC50 values of 7.36 ± 0.98 and 2.50 ± 0.15 µM, respectively. Further pharmacological analysis demonstrated that A17 induced HSC-2 cell cycle arrest at the S phase, cell apoptosis, and autophagy. Western blotting confirmed the regulatory effects of A17 on cell cycle arrest-, apoptosis-, and autophagy-related proteins expression. In addition, A17 regulated the AKT and AMPK pathways in HSC-2 cells. These results demonstrated that A17 possesses great potential as an anticancer agent.

Multiple receptor-ligand based pharmacophore modeling and molecular docking to screen the selective inhibitors of matrix metalloproteinase-9 from natural products.

Matrix metalloproteinase-9 (MMP-9) is an attractive target for cancer therapy. In this study, the pharmacophore model of MMP-9 inhibitors is built based on the experimental binding structures of multiple receptor-ligand complexes. It is found that the pharmacophore model consists of six chemical features, including two hydrogen bond acceptors, one hydrogen bond donor, one ring aromatic regions, and two hydrophobic (HY) features. Among them, the two HY features are especially important because they can enter the S1' pocket of MMP-9 which determines the selectivity of MMP-9 inhibitors. The reliability of pharmacophore model is validated based on the two different decoy sets and relevant experimental data. The virtual screening, combining pharmacophore model with molecular docking, is performed to identify the selective MMP-9 inhibitors from a database of natural products. The four novel MMP-9 inhibitors of natural products, NP-000686, NP-001752, NP-014331, and NP-015905, are found; one of them, NP-000686, is used to perform the experiment of in vitro bioassay inhibiting MMP-9, and the IC50 value was estimated to be only 13.4 µM, showing the strongly inhibitory activity of NP-000686 against MMP-9, which suggests that our screening results should be reliable. The binding modes of screened inhibitors with MMP-9 active sites were discussed. In addition, the ADMET properties and physicochemical properties of screened four compounds were assessed. The found MMP-9 inhibitors of natural products could serve as the lead compounds for designing the new MMP-9 inhibitors by carrying out structural modifications in the future.

A Novel Synthesis of the Efficient Anti-Coccidial Drug Halofuginone Hydrobromide.

Background: Halofuginone hydrobromide (1) is recognized as an effective drug against several species of Eimeria (E.) in poultry. In this paper, we describe a convenient and low cost preparation method for the compound, as well as primary validation of its activity. Methods: First, 7-bromo-6-chloroquinazolin-4(3H)-one (2) was prepared from m-chlorotoluene by a conventional process, and then chloroacetone was creatively introduced in two steps. Finally, halofuginone hydrobromide (1) was obtained from 7-bromo-6-chloro-3-(3-cholroacetonyl) quinazolin-4(3H)-one (4) by a four-step reaction sequence including condensation, cyclization, deprotection and isomerization. The structures of the relative intermediates and target compound were characterized by melting point, IR, MS and ¹H-NMR. Besides, the protective effect of compound 1-supplemented chicken diet at doses of 6, 3 and 1.5 mg per 1 kg were evaluated on chickens infected with E. tenella, by reduction in mortality, weight loss, fecal oocyst excretion and gut pathology, respectively. Results: Halofuginone hydrobromide (1) was prepared successfully by and improved and innovative method based on traditional research. Moreover, the synthesized halofuginone hydrobromide significantly exhibited an anti-coccidial property. Conclusions: The fruitful work described in this Communication has resulted in halofuginone hydrobromide, which has a good pharmaceutical development prospects, becoming more available for large-scale production.

Ru(II)-Catalyzed Direct C(sp(2))-H Activation/Selenylation of Arenes with Selenyl Chlorides.

A new ruthenium catalytic system was developed for the construction of a C(sp(2))-Se bond with the assistance of directing groups. This protocol features mild reaction conditions, wider substrate scope, and convenient late-stage selenylation of bioactive molecules.

Scaffold Hopping Approach to a New Series of Pyridine Derivatives as Potent Inhibitors of CDK2.

A scaffold hopping approach was exploited to guide the discovery of a series of pyridine derivatives as novel cyclin-dependent kinase (CDK2) inhibitors. These new compounds were designed, synthesized, and evaluated as CDK2 inhibitors. Most of the compounds showed potent inhibition against CDK2, and preliminary structure-activity relationship trends were revealed. A docking study on the most potent compound 6g implied the structural basis for potent CDK2 inhibition. All of the synthesized compounds were also evaluated for their cytotoxicity against the H522 and U87 cancer cell lines. The most potent and drug-like compound 6g was further tested against a normal cell line (L02), demonstrating that this compound is selectively toxic toward cancer cell lines. The results provide the foundation for further improving the potency of this series of compounds.

Synthesis and quantitative structure-activity relationship (QSAR) analysis of some novel oxadiazolo[3,4-d]pyrimidine nucleosides derivatives as antiviral agents.

We have synthesized a series of 4H,6H-[1,2,5]oxadiazolo[3,4-d]pyrimidine-5,7-dione 1-oxide nucleoside and their anti-vesicular stomatitis virus (VSV) activities in Wish cell were also investigated in vitro. It was found that most compounds showed obvious anti-VSV activities and compound 9 with ribofuranoside improved the anti-VSV activity by approximately 10 times and 18 times compared to didanosine (DDI) and acyclovir, respectively. A quantitative structure-activity relationship (QSAR) study of these compounds as well as previous reported oxadiazolo[3,4-d]pyrimidine nucleoside derivatives indicated that compounds with high activity should have small values of logP(o/w), vsurf_G and a large logS value. These findings and results provide a base for further investigations.

N-(1-Oxy-2-picolyl)oxalamic acids as a new type of O,O-ligands for the Cu-catalyzed N-arylation of azoles with aryl halides in water or organic solvent.

N-(1-Oxy-pyridin-2-ylmethyl)oxalamic acids (L3-L5) were identified as novel efficient ligands for copper-catalyzed C-N cross-coupling of azoles and aryl halides in water. The N-arylation of imidazoles, indoles and pyrazoles proceeded with moderate to excellent yields and complete selectivity over aromatic amines and phenols. Moreover, L5, which is also efficient in organic solvent with low catalyst loading, can be used to promote the N-arylation reactions with water-sensitive materials. The catalytic mechanism was proposed based on the results of several verification experiments which indicated that the ligands as new-type chelators may coordinate to Cu(I) with two oxygen atoms of N-oxide and amide in the coupling process.

Discovery and SAR study of c-Met kinase inhibitors bearing an 3-amino-benzo[d]isoxazole or 3-aminoindazole scaffold.

A series of 3-amino-benzo[d]isoxazole-/3-aminoindazole-based compounds were designed, synthesized and pharmacologically evaluated as tyrosine kinase c-Met inhibitors. The SAR study was conducted leading to identification of nine compounds (8d, 8e, 12, 28a-d, 28h and 28i) with IC50s less than 10nM against c-Met. Compound 28a stood out as the most potent c-Met inhibitor displaying potent inhibitory effects both at enzymatic (IC50=1.8 nM) and cellular (IC50=0.18 µM on EBC-1 cells) levels. In addition, 28a had a relatively good selectivity compared to a panel of our in-house 14 RTKs.

An Effective Synthesis Method for Tilorone Dihydrochloride with Obvious IFN-α Inducing Activity.

Tilorone dihydrochloride (1) has great potential for inducing interferon against pathogenic infection. In this paper, we describe a convenient preparation method for 2,7-dihydroxyfluoren-9-one (2), which is a usual pharmaceutical intermediate for preparing tilorone dihydrochloride (1). In the novel method, methyl esterification of 4,4'-dihydroxy-[1,1'-biphenyl]-2-carboxylic acid (4) was carried out under milder conditions with higher yield and played an important role in the preparation of compound 2. The structures of the relative intermediates and target compound were characterized by melting point, IR, MS, and ¹H-NMR. Furthermore, the synthesized tilorone dihydrochloride exhibited an obvious effect on induction of interferon-α (IFN-α) in mice within 12 h, and the peak level was observed until 24 h. This fruitful work has resulted in tilorone dihydrochloride becoming available in large-scale and wide application in clinics, which has a good pharmaceutical development prospects.

Unexpected N-glycosidation reaction of glycals with 1-amino-anthracene: structure revision and application to the synthesis of new analogues of marmycin A.

An unexpected N-glycosidation reaction of anthracen-1-amine with glycals was identified, and its use in the synthesis of C1' N-linked analogues of natural product marmycin A was explored. The structures of all these products were determined by 1D and 2D NMR, CD spectra, and X-ray crystal analysis. These products were then subjected to Friedel-Crafts acylation, Dess-Martin oxidation and nucleophilic addition leading to novel natural product analogues bearing a quaternary carbon center.

Multidimensional virtual screening approaches combined with drug repurposing to identify potential covalent inhibitors of SARS-CoV-2 3CL protease.

The outbreak of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has caused an unprecedented global pandemic, and new cases are still on the rise due to the absence of effective medicines. However, developing new drugs within a short time is extremely difficult. Repurposing the existing drugs provides a fast and effective strategy to identify promising inhibitors. Here we focus on the screening of drugs database for discovering potential covalent inhibitors that target 3-chymotrypsin-like protease (3CLpro), an essential enzyme mediating viral replication and transcription. Firstly, we constructed a receptor-ligand pharmacophore model and verified it through decoy set. The importance of pharmacophore features was evaluated by combining molecular dynamics simulation with interaction analyses. Then, covalent docking was used to perform further screening. According to docking score and Prime/Molecular Mechanics Generalized Born Surface Area (MM-GBSA) score, total ten compounds obtained good scores and successfully established covalent bonds with the catalytic Cys145 residue. They also formed favorable interactions with key residues in active sites and closely integrated with 3CLpro with binding modes similar to known 3CLpro inhibitor. Finally, the top four hits DB08732, DB04653, DB01871 and DB07299 were further subjected to 100 ns molecular dynamics (MD) simulation and MM-GBSA binding free energy calculations. The results suggest that the four candidates show good binding affinities for 3CLpro, which warrants further evaluation for their in-vitro/in-vivo activities. Overall, our research methods provide a valuable reference for discovering promising inhibitors against SARS-CoV-2 and help to fight against the epidemic.Communicated by Ramaswamy H. Sarma.

Multisubstituted quinoxalines and pyrido[2,3-d]pyrimidines: synthesis and SAR study as tyrosine kinase c-Met inhibitors.

Two series of new analogues were designed by replacing the quinoline scaffold of our earlier lead 2 (zgw-atinib) with quinoxaline and pyrido[2,3-d]pyrimidine frameworks. Moderate c-Met inhibitory activity was observed in the quinoxaline series. Among the pyrido[2,3-d]pyrimidine series, compounds 13a-c possessing an O-linkage were inactive, whilst the N-linked analogues 15a-c retained c-Met inhibitory potency. Highest activity was observed in the 3-nitrobenzyl analog 15b that showed an IC(50) value of 6.5 nM. Further structural modifications based on this compound were undergoing.

Ultrasound-promoted greener synthesis of novel trifurcate 3-substituted-chroman-2,4-dione derivatives and their drug-likeness evaluation.

An efficient and convenient approach for one-pot synthesis of 3-substituted chroman-2,4-diones via a three-component reaction of aromatic aldehydes, 4-hydroxy-coumarins and diverse pyrazolone derivatives was described. The combinatorial synthesis for this methodology was achieved by applying ultrasound irradiation in the absence of activator while making use of water as green solvent. Additionally, novel chroman-2,4-dione derivatives attached to an edaravone moiety represent an exploitable source of brand new anticancer agents. In comparison with conventional methods, experimental simplicity, good functional group tolerance, excellent yields, short routine, and atom efficiency are prominent features of this sonocatalyzed procedure.

Synthesis and cytotoxicity evaluation of 13-n-alkyl berberine and palmatine analogues as anticancer agents.

By introducing long carbon-chain alkyl groups at the C-13 position of berberine and palmatine, 13-n-hexyl/13-n-octyl berberine and palmatine chloride analogues 4a-d were synthesized and examined by MTT assays for cytotoxic activity in seven human cancer cell lines (7701QGY, SMMC7721, HepG2, CEM, CEM/VCR, KIII, Lewis), yielding IC50 values of 0.02 ± 0.01-13.58 ± 2.84 µM. 13-n-Octyl palmatine (compound 4d) gave the most potent inhibitor activity, with an IC50 of 0.02 ± 0.01 µM for SMMC7721. In all cases, the 13-n-alkyl berberine and palmatine analogues 4a-d were more cytotoxic than berberine and palmatine. In addition, compounds 4a-d also exhibited more potent cytotoxicity than berberine and palmatine in mice with S180 sarcoma xenografted in vivo. The primary screening results indicated that the 13-n-hexyl/13-n-octyl berberine and palmatine analogues might be valuable source for new potent anticancer drug candidates.

Pharmacological profiles and therapeutic applications of pachymic acid (Review).

Poria cocos is a saprophytic fungus that grows in diverse species of Pinus. Its sclerotium, called fu-ling or hoelen, has been used in various traditional Chinese medicines and health foods for thousands of years, and in several modern proprietary traditional Chinese medicinal products. It has extensive clinical indications, including sedative, diuretic, and tonic effects. Pachymic acid (PA) is the main lanostane-type triterpenoid in Poria cocos. Evidence suggests that PA has various biological properties such as cytotoxic, anti-inflammatory, antihyperglycemic, antiviral, antibacterial, sedative-hypnotic, and anti-ischemia/reperfusion activities. Although considerable advancements have been made, some fundamental and intricate issues remain unclear, such as the underlying mechanisms of PA. The present study aimed to summarize the biological properties and therapeutic potential of PA. The biosynthetic, pharmacokinetic, and metabolic pathways of PA, and its underlying mechanisms were also comprehensively summarized.

InBr3-catalyzed glycosidation of glycals with arylamines: an alternative approach to access 4-aminocyclopent-2-enones.

To turn side products into major products, a novel strategy to access biologically active 4-aminocyclopent-2-enones was developed. These compounds were originally identified as side products but became major products when 3,5-dimethylpyran-3,4-diol 7a was used as the substrate and 30% InBr(3) as the catalyst. Aryl- or heteroarylamines as well as variously substituted glycals can be used in this reaction, and the corresponding 4-aminocyclopent-2-enones were obtained in moderate to good yields. These compounds can be further used to prepare 4-aminocarbocyclic nucleosides.

Lewis acid catalyzed cyclization of glycals/2-deoxy-D-ribose with arylamines: additional findings on product structure and reaction diastereoselectivity.

The cyclization reactions of arylamines with 2-deoxy-D-ribose or glycals were reinvestigated in the current report. In the montmorillonite KSF- or InCl(3)-initiated reactions of 2-deoxy-D-ribose with arylamines, a pair of diastereomeric tetrahydro-2H-pyran-fused tetrahydroquinolines was obtained in a nearly 1:1 ratio where the structure of one diastereomer was incorrectly assigned in the literature. Meanwhile, the diastereoselectivity in InBr(3)-catalyzed cyclization of glycals with arylamines was also incorrectly reported previously. It was found that high diastereomeric selectivity was achieved only when a C5-substituted glycal was used; otherwise, a pair of diastereomers was obtained in moderate yield with 1:1 diastereomeric ratio. Furthermore, tetrahydrofuran-fused tetrahydroquinolines 5b and 5b' were also prepared successfully by using TBDPS-protected ribose as the glycal precursor and montmorillonite KSF as the activator.

Facile synthesis of indole- or benzofuran-fused benzo[a]carbazole-1,4-diones using a tandem two-step reaction sequence.

An efficient three-step approach was developed to assemble indole- or benzofuran-fused benzocarbazole-1,4-diones in 42-53% overall yield. This approach includes AgOAc-promoted oxidative cyclization of 2,6-di-bromocyclohexene-1,4-dione with indol-3-ylpropanoid acid, condensation of the resulting bromocarbazole intermediates with phenols or anilines, followed by Pd(OAc)-catalyzed cyclization. Such convenient synthetic protocol and the novelty of the corresponding products will largely assist our drug design and development program.

A novel 7-azaisoindigo derivative-induced cancer cell apoptosis and mitochondrial dysfunction mediated by oxidative stress.

This research focused on a novel 7-azaisoindigo derivative [namely N(1)-(n-butyl)-7-azaisoindigo, 7-AI-b], and investigated its molecular antitumor mechanism by exploring the means of cell death and the effects on mitochondrial function. 7-AI-b inhibited cancer cell proliferation in a dose- and time-dependent way. The morphological and nuclei changes in H(2) B-GFP-labeled HeLa cells were observed using a live cell system. The results suggested that cell death induced by 7-AI-b is closely related to apoptosis. 7-AI-b induced release of cytochrome C from mitochondria to cytosol and activation of caspase-3, showing that the apoptosis is mediated by the mitochondrial pathway. Furthermore, our data indicated that 7-AI-b triggers apoptosis through reactive oxygen species (ROS): cellular ROS levels were increased after 3 h exposure of 7-AI-b, which was reversed by the ROS scavenger N-acetyl-L-cysteine. As a consequence, 7-AI-b-mediated cell death, mitochondrial transmembrane potential collapse and ATP level were partly blocked by N-acetyl-L-cysteine. Further study showed that 7-AI-b could induce mitochondrial dysfunction: collapse of the mitochondrial transmembrane potential and reduction of intracellular ATP level. In summary, the novel synthesized 7-AI-b was demonstrated to be effective in killing cancer cells via an ROS-promoted and mitochondria- and caspase-dependent apoptotic pathway.

Mechanistic Exploration of Methionine 274 Acting as a "Switch" of the Selective Pocket Involved in HDAC8 Inhibition: An in Silico Study.

The overexpression of histone deacetylase 8 (HDAC8) causes several diseases, and the selective inhibition of HDAC8 has been touted as a promising therapeutic strategy due to its fewer side effects. However, the mechanism of HDAC8 selective inhibition remains unclear. In this study, flexible docking and in silico mutation were used to explore the structural change of methionine (M274) during HDAC8 binding to inhibitors, along with the reason for this change. Meanwhile, steered and conventional molecular dynamics simulations were employed to explore the stability of the structural change. The findings suggest that M274 acts as a "switch" to control the exposure of the HDAC8-selective pocket. The structure of M274 changes from flipped-out to flipped-in only when L-shaped inhibitors bind to HDAC8. This structural change forms a groove that allows these inhibitors to enter the selective pocket. In other HDACs, a leucine residue replaces M274 in situ, and the same structural change is not observed. The findings reveal the mechanism of selective HDAC8 inhibition and provide guidance for the development of novel selective inhibitors.