Synthesis, In Silico Study, and In Vitro Antifungal Activity of New 5-(1,3-Diphenyl-1H-Pyrazol-4-yl)-4-Tosyl-4,5-Dihydrooxazoles.

The increase in multi-drug resistant Candida strains has caused a sharp rise in life-threatening fungal infections in immunosuppressed patients, including those with SARS-CoV-2. Novel antifungal drugs are needed to combat multi-drug-resistant yeasts. This study aimed to synthesize a new series of 2-oxazolines and evaluate the ligands in vitro for the inhibition of six Candida species and in silico for affinity to the CYP51 enzymes (obtained with molecular modeling and protein homology) of the same species. The 5-(1,3-diphenyl-1H-pyrazol-4-yl)-4-tosyl-4,5-dihydrooxazoles 6a-j were synthesized using the Van Leusen reaction between 1,3-diphenyl-4-formylpyrazoles 4a-j and TosMIC 5 in the presence of K2CO3 or KOH without heating, resulting in short reaction times, high compound purity, and high yields. The docking studies revealed good affinity for the active site of the CYP51 enzymes of the Candida species in the following order: 6a-j > 4a-j > fluconazole (the reference drug). The in vitro testing of the compounds against the Candida species showed lower MIC values for 6a-j than 4a-j, and for 4a-j than fluconazole, thus correlating well with the in silico findings. According to growth rescue assays, 6a-j and 4a-j (like fluconazole) inhibit ergosterol synthesis. The in silico toxicity assessment evidenced the safety of compounds 6a-j, which merit further research as possible antifungal drugs.

Design, Synthesis, and Acaricidal Activity of 2,5-Diphenyl-1,3-oxazoline Compounds.

By using a scaffold hopping/ring equivalent and intermediate derivatization strategies, a series of compounds of 2,5-diphenyl-1,3-oxazoline with substituent changes at the 5-phenyl position were prepared, and their acaricidal activity was studied. However, the synthesized 2,5-diphenyl-1,3-oxazolines showed lower activity against mite eggs and larvae compared to the 2,4-diphenyl-1,3-oxazolines with the same substituents. We speculate that there is a significant difference in the spatial extension direction of the substituents between the two skeletons of compounds, resulting in differences in their ability to bind to the potential target chitin synthase 1. This work is helpful in inferring the internal structure of chitin synthase binding pockets.

A continuous reaction network that produces RNA precursors.

Continuous reaction networks, which do not rely on purification or timely additions of reagents, serve as models for chemical evolution and have been demonstrated for compounds thought to have played important roles for the origins of life such as amino acids, hydroxy acids, and sugars. Step-by-step chemical protocols for ribonucleotide synthesis are known, but demonstrating their synthesis in the context of continuous reaction networks remains a major challenge. Herein, compounds proposed to be important for prebiotic RNA synthesis, including glycolaldehyde, cyanamide, 2-aminooxazole, and 2-aminoimidazole, are generated from a continuous reaction network, starting from an aqueous mixture of NaCl, NH4Cl, phosphate, and HCN as the only carbon source. No well-timed addition of any other reagents is required. The reaction network is driven by a combination of γ radiolysis and dry-down. γ Radiolysis results in a complex mixture of organics, including the glycolaldehyde-derived glyceronitrile and cyanamide. This mixture is then dried down, generating free glycolaldehyde that then reacts with cyanamide/NH3 to furnish a combination of 2-aminooxazole and 2-aminoimidazole. This continuous reaction network models how precursors for generating RNA and other classes of compounds may arise spontaneously from a complex mixture that originates from simple reagents.

Synthesis and evaluation of new potential anti-pseudo-allergic agents.

Pseudo-allergic reactions frequently occur following clinical drug use and sometimes even cause mortal danger. Mas-related G-protein-coupled receptor member X2 (MRGPRX2) is a novel receptor that mediates pseudo-allergy and is an important target in the treatment of allergies. However, to date, there are no synthetic small-molecule inhibitors that prevent anaphylactoid reactions through this pathway. Our preliminary research suggested that B10-S and mubritinib effectively inhibited LAD2 cells. Therefore, two novel derivatives were synthesized by integrating the active substructures of B10-S and mubritinib, according to the molecular docking results. The antiallergic inhibitory effects of the two compounds were preliminarily evaluated in vitro using ß-hexosaminidase release, histamine release, and intracellular Ca2+ mobilization assays, and their binding sites on MRGPRX2 were analyzed by molecular docking. Both substances inhibited ß-hexosaminidase and histamine release in LAD2 cells and decreased intracellular Ca2+ by inhibiting MRGPRX2 in MRGPRX2-HEK293 cells treated with C48/80 in a dose-dependent manner. The docking results suggested that the molecules could competitively bind to the active site on MRGPRX2 and Glu141, which were combined by C48/80. Our study indicated that the two compounds have potential anti-allergic properties, which may provide evidence that will facilitate the development of synthetic molecules with anti-pseudo-allergic activity for clinical use in the future.

Novel O-acylated (E)-3-aryl-6,7-dihydrobenzisoxazol-4(5H)-one oximes targeting HSP90-HER2 axis in breast cancer cells.

Novel O-acylated (E)-3-aryl-6,7-dihydrobenzisoxazol-4(5H)-one oximes were designed as potential HSP90 inhibitors. A series of the compounds was synthesized by oximation of (E)-3-aryl-6,7-dihydrobenzisoxazol-4(5H)-ones followed by O-acylation with acylamidobenzoic acids. The obtained compounds showed an antiproliferative effect on three breast cancer cell lines (MCF7, MDA-MB-231 and HCC1954). Compound 16s exhibited high antiproliferative potency against HCC1954 breast cancer cells with the IC50 value of 6 µM was selected for in-depth evaluation. Compound 16s did not inhibit the growth of normal epithelial cells. We have demonstrated that the compound 16s can induce apoptosis in cancer cells via inhibition of HSP90 "client" proteins including a key oncogenic receptor, HER2/neu. Described here compounds can be considered for further basic and preclinical investigation as a part of HSP90/HER2-targeted therapies.

Natural-product-inspired design and synthesis of two series of compounds active against Trypanosoma cruzi: Insights into structure-activity relationship, toxicity, and mechanism of action.

Chemical scaffolds of natural products have historically been sources of inspiration for the development of novel molecules of biological relevance, including hit and lead compounds. To identify new compounds active against Trypanosoma cruzi, we designed and synthesized 46 synthetic derivatives based on the structure of two classes of natural products: tetrahydrofuran lignans (Series 1) and oxazole alkaloids (Series 2). Compounds were screened in vitro using a cellular model of T. cruzi infection. In the first series of compounds, 11 derivatives of hit compound 5 (EC50 = 1.1 µM) were found to be active; the most potent (7, 8, and 13) had EC50 values of 5.1-34.2 µM. In the second series, 17 analogs were found active at 50 µM; the most potent compounds (47, 49, 59, and 63) showed EC50 values of 24.2-49.1 µM. Active compounds were assessed for selectivity, hemocompatibility, synergistic potential, effects on mitochondrial membrane potential, and inhibitory effect on trypanothione reductase. All active compounds showed low toxicity against uninfected THP-1 cells and human erythrocytes. The potency of compounds 5 and 8 increased steadily in combination with benznidazole, indicating a synergistic effect. Furthermore, compounds 8, 47, 49, 59, and 63 inhibited parasitic mitochondria in a dose-dependent manner. Although increased reactive oxygen species levels might lead to mitochondrial effects, the results indicate that the mechanism of action of the compounds is not dependent on trypanothione reductase inhibition. In silico calculation of chemical descriptors and principal component analysis showed that the active compounds share common chemical features with other trypanocidal molecules and are predicted to have a good ADMET profile. Overall, the results suggest that the compounds are important candidates to be further studied for their potential against T. cruzi.

11-Step and Scalable Total Synthesis of Hamigeran M Enabled by Five C-H Functionalizations.

We report the convergent total synthesis of (±)-hamigeran M, enabled by five C-H functionalization reactions and proceeding in 11 steps in 3.9% overall yield. The C-H functionalizations include a hydroxy-directed C-H borylation, one C-H metalation-1,2-addition, one C-H metalation-Negishi coupling, a late-stage oxazole-directed C-H borylation-oxidation, and one electrophilic bromination. Two of these five C-H functionalizations forged strategic C-C bonds in the seven-membered ring of hamigeran M. The oxazole-directed C-H borylation-oxidation was unprecedented and ensured a late-stage hydroxylation. Other key steps include a tandem Suzuki reaction-lactonization to join the cyclopentane building block with the aromatic moiety and a hydrogen-atom transfer reaction to reduce a challenging tetrasubstituted double bond.

Truncated Actin-Targeting Macrolide Derivative Blocks Cancer Cell Motility and Invasion of Extracellular Matrix.

Cancer metastasis is a complex process involving highly motile tumor cells that breach tissue barriers, enter the bloodstream and lymphatic system, and disseminate throughout the body as circulating tumor cells. The primary cellular mechanism contributing to these critical events is the reorganization of the actin cytoskeleton. Mycalolide B (MycB) is an actin-targeting marine macrolide that can suppress proliferation, migration, and invasion of breast and ovarian cancer cells at low nanomolar doses. Through structure-activity relationship studies focused on the actin-binding tail region (C24-C35) of MycB, we identified a potent truncated derivative that inhibits polymerization of G-actin and severs F-actin by binding to actin's barbed end cleft. Biological analyses of this miniature MycB derivative demonstrate that it causes a rapid collapse of the actin cytoskeleton in ovarian cancer cells and impairs cancer cell motility and invasion of the extracellular matrix (ECM) by inhibiting invadopodia-mediated ECM degradation. These studies provide essential proof-of-principle for developing actin-targeting therapeutic agents to block cancer metastasis and establish a synthetically tractable barbed end-binding pharmacophore that can be further improved by adding targeting groups for precision drug design.

Synthesis and structure-activity relationships of 5-phenyloxazole-2-carboxylic acid derivatives as novel inhibitors of tubulin polymerization.

A series of 5-phenyloxazole-2-carboxylic acid derivatives were synthesized, and their structure-activity relationships (SARs) were studied. N,5-diphenyloxazole-2-carboxamides 6, 7, and 9, which mimicked ABT751, showed improved cytotoxicity compared with ABT751. Compound 9 exhibited the highest antiproliferative activities against Hela A549, and HepG2 cancer cell lines, with IC50 values of 0.78, 1.08, and 1.27 µM, respectively. Furthermore, compound 9 showed selectivity for human cancer cells over normal cells, and this selectivity was greater than those of ABT751 and colchicine. Preliminary mechanism studies suggested that compound 9 inhibited tubulin polymerization and led to cell cycle arrest at G2/M phase. Molecular docking studies indicated that compound 9 bound to the colchicine binding site of tubulin. Our findings provided insights into useful SARs for further structural modification of inhibitors of tubulin polymerization.

Synthesis and evaluation of trypanocidal activity of derivatives of naturally occurring 2,5-diphenyloxazoles.

African trypanosomiasis is a zoonotic protozoan disease affecting the nervous system. Various natural products reportedly exhibit trypanocidal activity. Naturally occurring 2,5-diphenyloxazoles present in Oxytropis lanata, and their derivatives, were synthesized. The trypanocidal activities of the synthesized compounds were evaluated against Trypanosoma brucei brucei, T. b. gambiense, T. b. rhodesiense, T. congolense, and T. evansi. Natural product 1 exhibited trypanocidal activity against all the species/subspecies of trypanosomes, exhibiting half-maximal inhibitory concentrations (IC50) of 1.1-13.5 µM. Modification of the oxazole core improved the trypanocidal activity. The 1,3,4-oxadiazole (7) and 2,4-diphenyloxazole (9) analogs exhibited potency superior to that of 1. However, these compounds exhibited cytotoxicity in Madin-Darby bovine kidney cells. The O-methylated analog of 1 (12) was non-cytotoxic and exhibited selective trypanocidal activity against T. congolense (IC50 = 0.78 µM). Structure-activity relationship studies of the 2,5-diphenyloxazole analogs revealed aspects of the molecular structure critical for maintaining selective trypanocidal activity against T. congolense.

Streptochlorin analogues as potential antifungal agents: Design, synthesis, antifungal activity and molecular docking study.

Streptochlorin is a small molecule of indole alkaloid isolated from marine Streptomyces sp., it is a promising lead compound due to its potent bioactivity in preventing many phytopathogens in our previous study, but further structural modifications are required to improve its antifungal activity. Our work in this paper focused on the replacement of oxazole ring in streptochlorin with the imidazole ring, to discover novel analogues. Based on this design strategy, three series of streptochlorin analogues were efficiently synthesized through sequential Vilsmeier-Haack reaction, Van Leusen imidazole synthesis and halogenation reaction. Some of the analogues displayed excellent activity in the primary assays, and this is highlighted by compounds 4g and 4i, the growth inhibition against Alternaria Leaf Spot and Rhizoctorzia solani under 50 µg/mL are 97.5% and 90.3%, respectively, even more active than those of streptochlorin, pimprinine and Osthole. Molecular docking models indicated that streptochlorin binds with Thermus thermophiles Leucyl-tRNA Synthetase in a similar mode to AN2690, offering a perspective on the mode of action study for antifungal activities of streptochlorin derivatives. Further study is still ongoing with the aim of discovering synthetic analogues, with improved antifungal activity and clear mode of action.

Design, synthesis and biological evaluation of a novel spiro oxazolidinedione as potent p300/CBP HAT inhibitor for the treatment of ovarian cancer.

Histone acetylation is one of the most essential parts of epigenetic modification, mediating a variety of complex biological functions. In these procedure, p300/CBP could catalyze the acetylation of lysine 27 on histone 3 (H3K27ac), and had been reported to mediate tumorigenesis and development in a variety of tumors by enhancing chromatin transcription activity. Ovarian cancer, as an extremely malignant tumor, has also been observed to undergo abnormal acetylation of histones. However, whether the treatment of ovarian cancer could be achieved by inhibiting the acetylation activity of p300/CBP on H3K27 has not been well investigated. In this article, we modified the structure of p300/CBP HAT domain inhibitor A-485 and obtained a highly active small molecule known as 13f, which has an IC50 value of 0.49 nM for inhibiting the in vitro enzyme activity of p300, as well as the anti-proliferation IC50 value on ovarian cancer cell line OVCAR-3 was 153 nM. In addition, 13f had strong acetylase family selectivity, good metabolic stability and promising in vivo anti-tumor activity in OVCAR-3 xenograft model. The discovery of 13f revealed a more active chemical entity of the HATs domain of p300/CBP and provided a novel idea for the application of epigenetic inhibitors in the treatment of ovarian cancer.

Discovery of novel oxazole-based macrocycles as anti-coronaviral agents targeting SARS-CoV-2 main protease.

We have discovered a family of synthetic oxazole-based macrocycles to be active against SARS-CoV-2. The synthesis, pharmacological properties, and docking studies of the compounds are reported in this study. The structure of the new macrocycles was confirmed by NMR spectroscopy and mass spectrometry. Compounds 13, 14, and 15a-c were evaluated for their anti-SARS-CoV-2 activity on SARS-COV-2 (NRC-03-nhCoV) virus in Vero-E6 cells. Isopropyl triester 13 and triacid 14 demonstrated superior inhibitory activities against SARS-CoV-2 compared to carboxamides 15a-c. MTT cytotoxicity assays showed that the CC50 (50% cytotoxicity concentration) of 13, 14, and 15a-c ranged from 159.1 to 741.8 µM and their safety indices ranged from 2.50 to 39.1. Study of the viral inhibition via different mechanisms of action (viral adsorption, replication, or virucidal property) showed that 14 had mild virucidal (60%) and inhibitory effects on virus adsorption (66%) at 20 µM concentrations. Compound 13 displayed several inhibitory effects at three levels, but the potency of its action is primarily virucidal. The inhibitory activity of compounds 13, 14, and 15a-c against the enzyme SARS-CoV-2 Mpro was evaluated. Isopropyl triester 13 had a significant inhibition activity against SARS-CoV-2 Mpro with an IC50 of 2.58 µM. Large substituents on the macrocyclic template significantly reduced the inhibitory effects of the compounds. Study of the docking of the compounds in the SARS CoV-2-Mpro active site showed that the most potent macrocycles 13 and 14 exhibited the best fit and highest affinity for the active site binding pocket. Taken together, the present study shows that the new macrocyclic compounds constitute a new family of SARS CoV-2-Mpro inhibitors that are worth being further optimized and developed.

Discovery of 5-(or 6)-benzoxazoles and oxazolo[4,5-b]pyridines as novel candidate antitumor agents targeting hTopo IIα.

Discovery of novel anticancer drugs which have low toxicity and high activity is very significant area in anticancer drug research and development. One of the important targets for cancer treatment research is topoisomerase enzymes. In order to make a contribution to this field, we have designed and synthesized some 5(or 6)-nitro-2-(substitutedphenyl)benzoxazole (1a-1r) and 2-(substitutedphenyl)oxazolo[4,5-b]pyridine (2a-2i) derivatives as novel candidate antitumor agents targeting human DNA topoisomerase enzymes (hTopo I and hTopo IIα). Biological activity results were found very promising for the future due to two compounds, 5-nitro-2-(4-butylphenyl)benzoxazole (1i) and 2-(4-butylphenyl)oxazolo[4,5-b]pyridine (2i), that inhibited hTopo IIα with 2 µM IC50 value. These two compounds were also found to be more active than reference drug etoposide. However, 1i and 2i did not show any satisfactory cyctotoxic activity on the HeLa, WiDR, A549, and MCF7 cancer cell lines. Moreover, molecular docking and molecular dynamic simulations studies for the most active compounds were applied in order to understand the mechanism of inhibition activity of hTopo IIα. In addition, in silico ADME/Tox studies were performed to predict drug-likeness and pharmacokinetic properties of all the tested compounds.

Synthesis of 2-Oxazolines from Ring Opening Isomerization of 3-Amido-2-Phenyl Azetidines.

Chiral 2-oxazolines are valuable building blocks and famous ligands for asymmetric catalysis. The most common synthesis involves the reaction of an amino alcohol with a carboxylic acid. In this paper, an efficient synthesis of 2-oxazolines has been achieved via the stereospecific isomerization of 3-amido-2-phenyl azetidines. The reactions were studied in the presence of both Brønsted and Lewis acids, and Cu(OTf)2 was found to be the most effective.

Synthesis and Biological Evaluation of New N-Acyl-α-amino Ketones and 1,3-Oxazoles Derivatives.

In order to develop novel bioactive substances with potent activities, some new valine-derived compounds incorporating a 4-(phenylsulfonyl)phenyl fragment, namely, acyclic precursors from N-acyl-α-amino acids and N-acyl-α-amino ketones classes, and heterocycles from the large family of 1,3-oxazole-based compounds, were synthesized. The structures of the new compounds were established using elemental analysis and spectral (UV-Vis, FT-IR, MS, NMR) data, and their purity was checked by reversed-phase HPLC. The newly synthesized compounds were evaluated for their antimicrobial and antibiofilm activities, for toxicity on D. magna, and by in silico studies regarding their potential mechanism of action and toxicity. The 2-aza-3-isopropyl-1-[4-(phenylsulfonyl)phenyl]-1,4-butanedione 4b bearing a p-tolyl group in 4-position exhibited the best antibacterial activity against the planktonic growth of both Gram-positive and Gram-negative strains, while the N-acyl-α-amino acid 2 and 1,3-oxazol-5(4H)-one 3 inhibited the Enterococcus faecium biofilms. Despite not all newly synthesized compounds showing significant biological activity, the general scaffold allows several future optimizations for obtaining better novel antimicrobial agents by the introduction of various substituents on the phenyl moiety at position 5 of the 1,3-oxazole nucleus.

Sigma-1 Receptor Agonist TS-157 Improves Motor Functional Recovery by Promoting Neurite Outgrowth and pERK in Rats with Focal Cerebral Ischemia.

Sigma-1 (σ-1) receptor agonists are considered as potential treatment for stroke. TS-157 is an alkoxyisoxazole-based σ-1 receptor agonist previously discovered in our group. The present study describes TS-157 profile in a battery of tests for cerebral ischemia. Initial evaluation demonstrated the compound's safety profile and blood-brain barrier permeability, as well as its ability to induce neurite outgrowth in vitro. The neurite outgrowth was shown to be mediated via σ-1 receptor agonism and involves upregulation of ERK phosphorylation (pERK). In particular, TS-157 also significantly accelerated the recovery of motor function in rats with transient middle cerebral artery occlusion (tMCAO). Overall, the results herein support the notion that σ-1 receptor agonists are potential therapeutics for stroke and further animal efficacy studies are warranted.

Streamlined Symmetrical Total Synthesis of Disorazole B1 and Design, Synthesis, and Biological Investigation of Disorazole Analogues.

Taking advantage of the C2-symmetry of the antitumor naturally occurring disorazole B1 molecule, a symmetrical total synthesis was devised with a monomeric advanced intermediate as the key building block, whose three-step conversion to the natural product allowed for an expeditious entry to this family of compounds. Application of the developed synthetic strategies and methods provided a series of designed analogues of disorazole B1, whose biological evaluation led to the identification of a number of potent antitumor agents and the first structure-activity relationships (SARs) within this class of compounds. Specifically, the substitutions of the epoxide units and lactone moieties with cyclopropyl and lactam structural motifs, respectively, were found to be tolerable for biological activities and beneficial with regard to chemical stability.

Facile Fabrication of Bio- and Dual-Functional Poly(2-oxazoline) Bottle-Brush Brush Surfaces.

Poly(2-oxazoline)s (POx) bottle-brush brushes have excellent biocompatible and lubricious properties, which are promising for the functionalization of surfaces for biomedical devices. Herein, a facile synthesis of POx is reported which is based bottle-brush brushes (BBBs) on solid substrates. Initially, backbone brushes of poly(2-isopropenyl-2-oxazoline) (PIPOx) were fabricated via surface initiated Cu0 plate-mediated controlled radical polymerization (SI-Cu0 CRP). Poly(2-methyl-2-oxazoline) (PMeOx) side chains were subsequently grafted from the PIPOx backbone via living cationic ring opening polymerization (LCROP), which result in ≈100 % increase in brush thickness (from 58 to 110 nm). The resultant BBBs shows tunable thickness up to 300 nm and high grafting density (σ) with 0.42 chains nm-2 . The synthetic procedure of POx BBBs can be further simplified by using SI-Cu0 CRP with POx molecular brush as macromonomer (Mn =536 g mol-1 , PDI=1.10), which results in BBBs surface up to 60 nm with well-defined molecular structure. Both procedures are significantly superior to the state-of-art approaches for the synthesis of POx BBBs, which are promising to design bio-functional surfaces.

Synthesis of Acid-Labile Poly(Doxazolidine) as a Polyprodrug with an Ultra-High Drug Content for Self-Delivery of High-Performance Chemotherapeutics.

Drug self-delivery systems (DSDSs) have attracted intense attention due to their high drug content. However, their practical application still suffers from their premature drug leakage, slow drug release, and/or low antitumor efficacy of the released small molecular drugs. Here, acid-labile poly(Doxazolidine) (P(Doxaz)) is designed as a polyprodrug for the self-delivery of high antitumor chemotherapeutics (Doxazolidine (Doxaz)), with an ultrahigh Doxaz content of 92.45%. The P(Doxaz) nanoparticles could completely degrade into Doxaz within 10 h in the simulated tumor intracellular microenvironment, with a low drug leakage of 12.9% over 12 h in the normal physiological media. Owing to the ultrahigh drug content, fast acid-triggered degradation and drug release, and high antitumor efficacy of Doxaz, the proposed DSDS possesses an enhanced antiproliferation efficacy compared to the free DOX, demonstrating its potential in future tumor treatments.