Synthesis of tricarbonylated propargylamine and conversion to 2,5-disubstituted oxazole-4-carboxylates

The N,O-acetal derived from diethyl mesoxalate (DEMO) undergoes elimination of acetic acid upon treatment with a base, leading to the formation of N-acylimine in situ. Lithium acetylide readily attacks the imino group to afford N,1,1-tricarbonylated propargylamines. When the resulting propargylamine reacts with butyllithium, ring closure occurs between the ethynyl and carbamoyl groups, yielding 2,5-disubstituted oxazole-4-carboxylates. This cyclization also occurs when the propargylamine is heated with ammonium acetate, resulting in double activation.

Crystal-structure determination and Hirshfeld surface analysis of two new thio-phene derivatives: (E)-N-{2-[2-(benzo[b]thio-phen-2-yl)ethen-yl]-5-fluoro-phen-yl}benzene-sulfonamide and (E)-N-{2-[2-(benzo[b]thio-phen-2-yl)ethen-yl]-5-fluoro-phen-yl}-N-(but-2-yn-1-yl)benzene-sulfonamide

In the title compounds, C22H16FNO2S2 (I) and C26H20FNO2S2 (II), the benzo-thio-phene rings are essentially planar with maximum deviations of 0.009 (1) and 0.001 (1) Å for the carbon and sulfur atom in compounds I and II, respectively. In I, the thio-phene ring system is almost orthogonal to the phenyl ring attached to the sulfonyl group, with a dihedral angle of 77.7 (1)°. In compound I, the mol-ecular structure is stabilized by weak C-H⋯O intra-molecular inter-actions formed by the sulfone oxygen atoms, which generate two S(5) ring motifs. In the crystal of I, N-H⋯O hydrogen bonds link the mol-ecules into R 2 2(8) rings, which are connected into a C(10) chain via C-H⋯F hydrogen bonds. Inter-molecular C-H⋯π inter-actions are also observed. In compound II, the mol-ecules are linked via C-H⋯O and C-H⋯F hydrogen bonding, generating infinite C(11) and C(13) chains running parallel to [010].

The synthesis, crystal structure and Hirshfeld surface analysis of the thio-phene derivatives 5-(phenyl-sulfon-yl)-5,6-di-hydro-benzo[4,5]thieno[3,2-j]phenanthridine and (E)-N-{2-[2-(benzo[b]thiophen-2-yl)ethenyl]phen-yl}-N-(prop-2-yn-1-yl)benzene-sulfonamide

In both of the title compounds, C26H19NO2S2, (I), and C25H19NO2S2, (II), the benzo-thio-phene rings are essentially planar with maximum deviations of 0.026 (1) and -0.016 (1) Å for the carbon and sulfur atoms in compounds (I) and (II), respectively. In (I), the thio-phene ring system is almost orthogonal to the phenyl ring attached to the sulfonyl group, subtending a dihedral angle of 88.1 (1)°, and the di-hydro-pyridine ring adopts a screw-boat conformation. In both compounds, the mol-ecular structure is consolidated by weak C-H⋯O intra-molecular inter-actions formed by the sulfone oxygen atoms, which generate S(5) ring motifs. In the crystal of II, mol-ecules are linked via C-H⋯O hydrogen bonds, generating C(7) chains running along the [100] direction. No significant inter-molecular inter-actions are observed in I.

Synthesis, ADMET Properties, and In Vitro Antimicrobial and Antibiofilm Activity of 5-Nitro-2-thiophenecarbaldehyde N-((E)-(5-Nitrothienyl)methylidene)hydrazone (KTU-286) against Staphylococcus aureus with Defined Resistance Mechanisms

The emergence of drug-resistant Staphylococcus aureus is responsible for high morbidity and mortality worldwide. New therapeutic options are needed to fight the increasing antimicrobial resistance among S. aureus in the clinical setting. We, therefore, characterized the in silico absorption, distribution, metabolism, elimination, and toxicity (ADMET) and in vitro antimicrobial activity of 5-nitro-2-thiophenecarbaldehyde N-((E)-(5-nitrothienyl)methylidene)hydrazone (KTU-286) against drug-resistant S. aureus strains with genetically defined resistance mechanisms. The antimicrobial activity of KTU-286 was determined by CLSI recommendations. The ADMET properties were estimated by using in silico modeling. The activity on biofilm integrity was examined by crystal violet assay. KTU-286 demonstrated low estimated toxicity and low skin permeability. The highest antimicrobial activity was observed among pan-susceptible (Pan-S) S. aureus (minimal inhibitory concentration (MIC) 0.5–2.0 µg/mL, IC₅₀ = 0.460 µg/mL), followed by vancomycin resistant S. aureus (VRSA) (MIC 4.0 µg/mL, IC₅₀ = 1.697 µg/mL) and methicillin-resistant S. aureus (MRSA) (MIC 1.0–16.0 µg/mL, IC₅₀ = 2.282 µg/mL). KTU-286 resulted in significant (p < 0.05) loss of S. aureus biofilm integrity in vitro. Further studies are needed for a better understanding of safety, synergistic relationship, and therapeutic potency of KTU-286.

Heteroaromatic Polyamides with Improved Thermal and Mechanical Properties

We prepared high-performance aromatic copolyamides, containing bithiazole and thiazolo-thiazole groups in their main chain, from aromatic diamines and isophthaloyl chloride, to further improve the prominent thermal behavior and exceptional mechanical properties of commercial aramid fibers. The introduction of these groups leads to aramids with improved strength and moduli compared to commercial meta-oriented aromatic polyamides, together with an increase of their thermal performance. Moreover, their solubility, water uptake, and optical properties were evaluated in this work.

Design, diversity-oriented synthesis and biological evaluation of novel heterocycle derivatives as non-nucleoside HBV capsid protein inhibitors

The capsid assembly is a significant phase for the hepatitis B virus (HBV) lifespan and is an essential target for anti-HBV drug discovery and development. Herein, we used scaffold hopping, bioisosterism, and pharmacophore hybrid-based strategies to design and synthesize six series of various heterocycle derivatives (pyrazole, thiazole, pyrazine, pyrimidine, and pyridine) and screened for in vitro anti-HBV non-nucleoside activity. Drug candidate NZ-4 and AT-130 were used as lead compounds. Several compounds exhibited prominent anti-HBV activity compared to lead compound NZ-4 and positive drug Lamivudine, especially compound II-8b, showed the most prominent anti-HBV DNA replication activity (IC₅₀ = 2.2 ± 1.1 μM). Also compounds IV-8e and VII-5b showed the best in vitro anti-HBsAg secretion (IC₅₀ = 3.8 ± 0.7 μM, CC₅₀ > 100 μM) and anti-HBeAg secretion (IC₅₀ = 9.7 ± 2.8 μM, CC₅₀ > 100 μM) respectively. Besides, II-8b can interact HBV capsid protein with good affinity constants (K_D = 60.0 μM), which is equivalent to lead compound NZ-4 ((K_D = 50.6 μM). The preliminary structure-activity relationships (SARs) of the newly synthesized compounds were summarized, which may help researchers to discover more potent anti-HBV agents.

Synthesis of novel Schiff bases using 2-Amino-5-(3-fluoro-4-methoxyphenyl)thiophene-3-carbonitrile and 1,3-Disubstituted pyrazole-4-carboxaldehydes derivatives and their antimicrobial activity

2-Amino-5-(3-fluoro-4-methoxyphenyl)thiophene-3-carbonitrile have been synthesized from 1-(3-fluoro-4-methoxyphenyl)ethanone, malononitrile, a mild base and sulfur powder using Gewald synthesis technique and the intermediate was treated with 1,3-disubstituted pyrazole-4-carboxaldehyde to obtain the novel Schiff bases. 1,3-disubstituted pyrazole-4-carboxaldehyde derivatives have been synthesized by Vilsmeier-Haack reaction in the course of a multi-step reaction. The structure of novel compounds were established on the basis of their elemental analyses IR, ¹H NMR, ¹³C NMR, and mass spectral data and then screened for their in vitro antimicrobial activity. Among them 5a, 5c, 5f and 5h showed excellent activity when compared to other derivatives. Remaining derivatives showed moderate activity.

Anti-virus reagents targeting the capsid protein assembly

The capsid protein is a promising target for the development of therapeutic anti-virus agents.

Antimicrobial activity of thiophene derivatives derived from ethyl (E)-5-(3-(dimethylamino)acryloyl)-4-methyl-2-(phenylamino)thiophene-3-carboxylate

Background

The thiophene nucleus has been recognized as an important entity in the synthesis of heterocyclic compounds with promising pharmacological characteristics.

Results

A number of new heterocyclic compounds incorporating thiophene species have been prepared from the titled enaminone via the reaction with different nucleophiles and electrophiles. The structure elucidation of the designed compounds was derived from their spectral information. The results of antimicrobial activity of the prepared compounds revealed that derivatives 7b and 8 exhibited activity comparable to the standard drugs ampicillin and gentamicin for all tested bacteria species. Additionally, compound 3 displayed potent activity against Aspergillus fumigates, whereas compounds 5, 6, and 7a showed good activity against Syncephalastrum racemosum.

Conclusions

We have synthesized a number of new thiophene-containing compounds. The results of antimicrobial activity of the prepared compounds revealed that changing the substituents at position-2 of thiophene ring significantly affect their biological activity. The pyridine side chain derivatives in compounds 7a, 7b and 8 showed excellent antimicrobial activity.

Past, Current, and Future Developments of Therapeutic Agents for Treatment of Chronic Hepatitis B Virus Infection

For decades, treatment of hepatitis B virus (HBV) infection has been relying on interferon (IFN)-based therapies and nucleoside/nucleotide analogues (NAs) that selectively target the viral polymerase reverse transcriptase (RT) domain and thereby disrupt HBV viral DNA synthesis. We have summarized here the key steps in the HBV viral life cycle, which could potentially be targeted by novel anti-HBV therapeutics. A wide range of next-generation direct antiviral agents (DAAs) with distinct mechanisms of actions are discussed, including entry inhibitors, transcription inhibitors, nucleoside/nucleotide analogues, inhibitors of viral ribonuclease H (RNase H), modulators of viral capsid assembly, inhibitors of HBV surface antigen (HBsAg) secretion, RNA interference (RNAi) gene silencers, antisense oligonucleotides (ASOs), and natural products. Compounds that exert their antiviral activities mainly through host factors and immunomodulation, such as host targeting agents (HTAs), programmed cell death protein 1 (PD-1)/programmed death ligand 1 (PD-L1) inhibitors, and Toll-like receptor (TLR) agonists, are also discussed. In this Perspective, we hope to provide an overview, albeit by no means being comprehensive, for the recent development of novel therapeutic agents for the treatment of chronic HBV infection, which not only are able to sustainably suppress viral DNA but also aim to achieve functional cure warranted by HBsAg loss and ultimately lead to virus eradication and cure of hepatitis B.

Synthesis of 5,5'-Diarylimino Quinoidal 2,2'-Bithiazoles

A Pd(0)-catalyzed double C-N coupling of 5,5'-dibromo-2,2'-bithiazoles with (het)arylamines and subsequent in situ Ag₂O-mediated oxidation provides access to cross-conjugated quinoidal 5,5'-diarylimino-2,2'-bithiazoles in moderate to high yield. The highly colored quinoidal 2,2'-bithiazoles were studied by UV/vis spectroscopy, cyclic voltammetry and computational methods.

Design, synthesis and evaluation of pyrazole derivatives as non-nucleoside hepatitis B virus inhibitors

In continuation of our efforts toward the discovery of potent non-nucleoside hepatitis B virus (HBV) inhibitors with novel structures, we have employed bioisosterism and hybrid pharmacophore-based strategy to explore the chemically diverse space of bioactive compounds. In this article, the original thiazole platform was replaced with pyrazole scaffold to yield the optimal pharmacophore moieties in order to generate novel non-nucleoside HBV inhibitors with desirable potency. Some of the new compounds were able to inhibit HBV activity in the low micromolar range. In particular, compound 6a3 displayed the most potent activity against the secretion of HBsAg and HBeAg with IC50 of 24.33 μM and 2.22 μM, respectively. The preliminary structure-activity relationship (SAR) of this new series of compounds was investigated, which may help designing more potent molecules.

Synthesis and antiviral activity of some new bis-1,3-thiazole derivatives

Treatment of 3-phenyl-1,3-thiazolidin-4-one derivative 1 with phenylisothiocyanate in DMF, in the presence of potassium hydroxide, at room temperature gave the non-isolable potassium salt 2. The in-situ reaction of 2 with differently substituted N-aryl hydrazonoyl chlorides 3, 7a-d and 14a-d afforded the corresponding 2-(pyrazolyl)thiazolylimino-5-(thiadiazolylidene)thiazolidin-4-one derivatives 6, 10a-d and 17a-d, respectively. Reaction of 2 with further α-haloketones yielded the 4-(pyrazolyl)thiazolylimino-bis-thiazolidine derivatives 22, 25 and 26. Single crystal X-ray analysis was used in structure elucidation of the products. The in-vitro antiviral screening against four viruses (Poliovirus, Influenza A (H1N1) virus, Hepatitis B virus and Hepatitis C virus) for the obtained compounds was examined. Structure activity relationship (SAR) was also studied. The goal of the work was achieved in discovering a very active compound 10a as anti HCV agent (EC50 0.56 μM).

Non-nucleoside anti-HBV agents: advances in structural optimization and mechanism of action investigations

In this review, we focus on the recent advances in discovery, structural modifications and biological activities studies of several distinct classes of synthetic non-nucleoside small molecular compounds with new mechanisms.

Emergence of Chinese drug discovery research: impact of hit and lead identification

The identification of hits and the generation of viable leads is an early and yet crucial step in drug discovery. In the West, the main players of drug discovery are pharmaceutical and biotechnology companies, while in China, academic institutions remain central in the field of drug discovery. There has been a tremendous amount of investment from the public as well as private sectors to support infrastructure buildup and expertise consolidation relative to drug discovery and development in the past two decades. A large-scale compound library has been established in China, and a series of high-impact discoveries of lead compounds have been made by integrating information obtained from different technology-based strategies. Natural products are a major source in China's drug discovery efforts. Knowledge has been enhanced via disruptive breakthroughs such as the discovery of Boc5 as a nonpeptidic agonist of glucagon-like peptide 1 receptor (GLP-1R), one of the class B G protein-coupled receptors (GPCRs). Most of the original hit identification and lead generation were carried out by academic institutions, including universities and specialized research institutes. The Chinese pharmaceutical industry is gradually transforming itself from manufacturing low-end generics and active pharmaceutical ingredients to inventing new drugs.

Potent and orally efficacious bisthiazole-based histone deacetylase inhibitors

Inspired by the thiazole-thiazoline cap group in natural product largazole, a series of structurally simplified bisthiazole-based histone deacetylase inhibitors were prepared and evaluated. Compound 8f was evaluated in vivo in an experimental autoimmune encephalomyelitis (EAE) model and found to be orally efficacious in ameliorating clinical symptoms of EAE mice.

Isothiafludine, a novel non-nucleoside compound, inhibits hepatitis B virus replication through blocking pregenomic RNA encapsidation

AIM

To investigate the action of isothiafludine (NZ-4), a derivative of bis-heterocycle tandem pairs from the natural product leucamide A, on the replication cycle of hepatitis B virus (HBV) in vitro and in vivo.

METHODS

HBV replication cycle was monitored in HepG2.2.15 cells using qPCR, qRT-PCR, and Southern and Northern blotting. HBV protein expression and capsid assembly were detected using Western blotting and native agarose gel electrophoresis analysis. The interaction of pregenomic RNA (pgRNA) and the core protein was investigated by RNA immunoprecipitation. To evaluate the anti-HBV effect of NZ-4 in vivo, DHBV-infected ducks were orally administered NZ-4 (25, 50 or 100 mg·kg⁻¹·d⁻¹) for 15 d.

RESULTS

NZ-4 suppressed intracellular HBV replication in HepG2.2.15 cells with an IC₅₀ value of 1.33 μmol/L, whereas the compound inhibited the cell viability with an IC₅₀ value of 50.4 μmol/L. Furthermore, NZ-4 was active against the replication of various drug-resistant HBV mutants, including 3TC/ETV-dual-resistant and ADV-resistant HBV mutants. NZ-4 (5, 10, 20 μmol/L) concentration-dependently reduced the encapsidated HBV pgRNA, resulting in the assembly of replication-deficient capsids in HepG2.2.15 cells. Oral administration of NZ-4 dose-dependently inhibited DHBV DNA replication in the DHBV-infected ducks.

CONCLUSION

NZ-4 inhibits HBV replication by interfering with the interaction between pgRNA and HBcAg in the capsid assembly process, thus increasing the replication-deficient HBV capsids. Such mechanism of action might provide a new therapeutic strategy to combat HBV infection.

A review of non-nucleoside anti-hepatitis B virus agents

Hepatitis B Virus is the most common cause of chronic liver disease worldwide. Currently approved agents of chronic HBV infection treatment include interferon and nucleoside analogues. However, the side effects of interferon and the viral resistance of nucleoside analogues make the current treatment far from satisfactory. Therefore, new drugs with novel structures and mechanisms are needed. Recently, a number of non-nucleoside HBV inhibitors have been obtained from natural sources or prepared by synthesis/semi-synthesis. Some of them exhibited potent anti-HBV activity with novel mechanisms. These compounds provide useful information for the medicinal chemist to develop novel non-nucleoside compounds as anti-HBV agents.

Synthesis and Antiviral Activity of Conformational Analogues of Leucamide A

In order to study the effect of heterocyclic core conformational state of leucamide A on its anti-influenza virus A activity, five conformational analogues were prepared by replacing the Pro-Leu dipeptide in the molecule with various amino acids. The amino acids used were of 2 to 6 carbons. The results showed that these replacements not only changed the conformational relationship between the 4,2-bisheterocycle tandem pair and the third heterocycle, but also had dramatic effect on its activity against influenza virus A.

Design and synthesis of novel benzimidazole derivatives as inhibitors of hepatitis B virus

A series of novel benzimidazole derivatives were synthesized and evaluated for their anti-hepatitis B virus (HBV) activity and cytotoxicity in the HepG2.2.15 cell line. The preliminary SAR was discussed. Compound 12a, with IC50<0.41 microM and SI>81.2, was the most promising compound and selected as the benchmark compound for further optimization.