Heterocyclic ureas: inhibitors of acyl-CoA:cholesterol O-acyltransferase as hypocholesterolemic agents

Amide bioisosteric replacement in the design and synthesis of quorum sensing modulators

The prevention or control of bacterial infections requires continuous search for novel approaches among which bacterial quorum sensing inhibition is considered as a complementary antibacterial strategy. Quorum sensing, used by many different bacteria, functions through a cell-to-cell communication mechanism relying on chemical signals, referred to as autoinducers, such as N-acyl homoserine lactones (AHLs) which are the most common chemical signals in this system. Designing analogs of these autoinducers is one of the possible ways to interfere with quorum sensing. Since bioisosteres are powerful tools in medicinal chemistry, targeting analogs of AHLs or other signal molecules and mimics of known QS modulators built on amide bond bioisosteres is a relevant strategy in molecular design and synthetic routes. This review highlights the application of amide bond bioisosteric replacement in the design and synthesis of novel quorum sensing inhibitors.

Discovery of novel N-acylpyrazoles as potent and selective thrombin inhibitors

Direct oral anticoagulants (DOACs), which includes thrombin and factor Xa inhibitors, have emerged as the preferred therapeutics for thrombotic disorders, penetrating a market previously dominated by warfarin and heparin. This article describes the discovery and profiling of a novel series of N-acylpyrazoles, which act as selective, covalent, reversible, non-competitive inhibitors of thrombin. We describe in vitro stability issues associated with this chemotype and, importantly, demonstrate that N-acylpyrazoles successfully act in vivo as anticoagulants in basic thrombotic animal models. Crucially, this anticoagulant nature is unaccompanied by the higher bleeding risk profile that has become an undesirable characteristic of the DTIs and factor Xa inhibitors. We propose that the N-acylpyrazole chemotype shows intriguing promise as next-generation oral anticoagulants.

Design, synthesis, in vitro and in silico bioactivity profiles of new urea/thiourea derivatives of 2-pyridyl piperazine as potent antioxidant and antimicrobial agents: chemo-bio-computational approach

Synthesis of a series of new urea and thiourea derivatives of 2-pyridyl piperazine was accomplished by reacting various isocyanates and isothiocyanates in the presence of triethylamine (TEA) at 50 °C. All the title compounds were obtained in high yields and their structures were characterized by IR, ¹H, ¹³C NMR, Mass spectral, and Elemental analysis. The synthesized compounds were screened for in vitro and in silico antioxidant and antimicrobial activities. All the title compounds exhibited potent antioxidant and antimicrobial activities. Out of all, 2c and 2f against DPPH, H₂O₂ and Nitro oxide have exhibited significant activity and the levels of activity were higher than the reference compounds, ascorbic acid and BHT. Whereas 2a, 2c, 2f and 2j have shown prominent activity in terms of zone of inhibition against all the microbial strains tested than the standards such as levofloxacin and nystatin. In addition in silico studies also conveyed the same that is 2a, 2c, 2f and 2j have displayed the highest binding energies against peroxiredoxins and DNA gyrase protein than the standards akin to the rest of the compounds. In overall, 2c and 2f have exhibited most promising antioxidant and antimicrobial activity than the rest of the title compounds in vitro and in silico. Hence, 2c and 2f will stand as a lead and promising antioxidant and antimicrobial drug candidates in future.

Design, synthesis, characterization and in vitro, in vivo and in silico antimicrobial and antiinflammatory activities of a new series of sulphonamide and carbamate derivatives of a nebivolol intermediate

A series of new sulphonamide and carbamate derivatives of Nebivolol drug intermediate (5) were designed and synthesized by reacting various biopotent sulphonylchlorides and chloroformates. The synthesized compounds are structurally characterized by spectral (IR, ¹H & ¹³C NMR and mass) and screened for their in vitro antimicrobial activity against four bacterial and three fungal strains, in vitro and in vivo antiinflammatory activity against LPS-induced inflammation in RAW 264.7, in vitro COX-1 and COX-2 inhibition potentiality, antagonistic profiles of carrageenan induced paw edema and cotton pellet induced granuloma in rat. Further, the compounds were screened for their antimicrobial and antiinflammatory activity against DNA gyrase A, COX-1 and COX-2 by using molecular docking approach. The bioactivity and toxicity risks were analysed through Molecular Operating Environment. The results revealed that the compounds 8b, 8c, 8d, 8e, 8f, 8g and 9a exhibited the most promising antimicrobial activity against all the bacterial and fungal strains tested when compared with the standard drugs streptomycin and fluconazole. In view of in antiinflammatory activity, the compounds, 8b, 8c, 8d, 8e, 8f, 8g and 9a have shown potent antiinflammatory activity by inhibiting the LPS-induced inflammation in RAW 264.7 cell line, concentration dependent inhibition of COX-1 and COX-2, dose response dependent antagonism of carrageenan induced paw edema and granuloma tissue in rat. Molecular docking, ADMET and QSAR studies predicted that the recorded in silico profiles are in strong correlation with in vitro and in vivo antimicrobial and antiinflammatory results. In addition, the elevated toxicology risks of the title compounds are identified with in the potential limits of drug candidates. Hence, it is suggested that the synthesized derivatives will stand as the promising antimicrobial and anti-inflammatory drug candidates in future.

A series of new sulphonamide and carbamate derivatives of Nebivolol drug intermediate (5) were designed and synthesized by reacting various biopotent sulphonylchlorides and chloroformates.

Total Syntheses and Cytotoxic Evaluations of Cryptolactones A1, A2, B1, B2, and Their Derivatives

The cryptolactones A₁, A_2, B₁, and B₂ isolated from a Cryptomyzus sp. aphid were synthesized via the Mukaiyama aldol reaction and olefin metathesis. Their antipodes and derivatives were also synthesized by the same strategy to investigate structure-activity relationships. These compounds exhibited cytotoxic activity against human promyelocytic leukemia HL-60 cells with IC₅₀ values of 2.1-42 µM.

Tetrazole regioisomers in the development of nitro group-containing antitubercular agents

Tetrazole derivatives containing nitro substituents have been identified as promising antitubercular agents.

Isolation and total syntheses of cytotoxic cryptolactones A1, A2, B1, and B2: α,β-unsaturated δ-lactones from a Cryptomyzus sp. aphid

The cryptolactones A1, A2, B1, and B2, which are α,β-unsaturated δ-lactones, were isolated from a Cryptomyzus sp. aphid. The structures were established by 1-D and 2-D NMR spectra and CI-HRMS. Their absolute configurations were determined with the Kusumi-Mosher method, combined with asymmetric total syntheses. The syntheses were accomplished with the Mukaiyama aldol reaction and olefin metathesis, which utilized the second-generation Grubbs catalyst for the key steps. These compounds exhibited cytotoxic activity against human promyelocytic leukemia HL-60 cells with IC50 values of 0.97-5.3 μM.

Structure-activity relationships of 2-aminothiazoles effective against Mycobacterium tuberculosis

A series of 2-aminothiazoles was synthesized based on a HTS scaffold from a whole-cell screen against Mycobacterium tuberculosis (Mtb). The SAR shows the central thiazole moiety and the 2-pyridyl moiety at C-4 of the thiazole are intolerant to modification. However, the N-2 position of the aminothiazole exhibits high flexibility and we successfully improved the antitubercular activity of the initial hit by more than 128-fold through introduction of substituted benzoyl groups at this position. N-(3-Chlorobenzoyl)-4-(2-pyridinyl)-1,3-thiazol-2-amine (55) emerged as one of the most promising analogues with a MIC of 0.024μM or 0.008μg/mL in 7H9 media and therapeutic index of nearly ∼300. However, 55 is rapidly metabolized by human liver microsomes (t1/2=28min) with metabolism occurring at the invariant aminothiazole moiety and Mtb develops spontaneous low-level resistance with a frequency of ∼10(-5).

Inhibition of the production of the Pseudomonas aeruginosa virulence factor pyocyanin in wild-type cells by quorum sensing autoinducer-mimics

Pseudomonas aeruginosa is a notorious human pathogen associated with a range of life-threatening nosocomial infections. There is an increasing problem of antibiotic resistance in P. aeruginosa, highlighted by the emergence of multi-drug resistant strains. Thus the exploration of new strategies for the treatment of P. aeruginosa infections is clearly warranted. P. aeruginosa is known to produce a range of virulence factors that enhance its ability to damage the host tissue and cause disease. One of the most important virulence factors is pyocyanin. P. aeruginosa regulates pyocyanin production using an intercellular communication mechanism called quorum sensing, which is mediated by small signalling molecules termed autoinducers. One native autoinducer is N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL). Herein we report the synthesis of a collection of abiotic OdDHL-mimics. A number of novel compounds capable of competing with the endogenous OdDHL and consequently, inhibiting the production of pyocyanin in cultures of wild type P. aeruginosa were identified. We present evidence suggesting that compounds of this general structural type act as direct antagonists of quorum sensing in P. aeruginosa and as such may find value as molecular tools for the study and manipulation of this signalling pathway. A direct quantitative comparison of the pyocyanin suppressive activities of the most active OdDHL-mimics with some previously-reported inhibitors (based around different general structural frameworks) of quorum sensing from the literature, was also made.

Synthetic approaches and pharmacological activity of 1,3,4-oxadiazoles: a review of the literature from 2000-2012

This review provides readers with an overview of the main synthetic methodologies for 1,3,4-oxadiazole derivatives, and of their broad spectrum of pharmacological activities as reported over the past twelve years.

Novel Pseudomonas aeruginosa quorum-sensing inhibitors identified in an ultra-high-throughput screen

The opportunistic pathogen Pseudomonas aeruginosa has two complete acyl-homoserine lactone (acyl-HSL) signaling systems, LasR-LasI and RhlR-RhlI. LasI catalyzes the synthesis of N-3-oxododecanoyl homoserine lactone (3OC12-HSL), and LasR is a transcription factor that requires 3OC12-HSL as a ligand. RhlI catalyzes the synthesis of N-butanoyl homoserine lactone (C4), and RhlR is a transcription factor that responds to C4. LasR and RhlR control the transcription of hundreds of P. aeruginosa genes, many of which are critical virulence determinants, and LasR is required for RhlR function. We developed an ultra-high-throughput cell-based assay to screen a library of approximately 200,000 compounds for inhibitors of LasR-dependent gene expression. Although the library contained a large variety of chemical structures, the two best inhibitors resembled the acyl-homoserine lactone molecule that normally binds to LasR. One compound, a tetrazole with a 12-carbon alkyl tail designated PD12, had a 50% inhibitory concentration (IC50) of 30 nM. The second compound, V-06-018, had an IC50 of 10 microM and is a phenyl ring with a 12-carbon alkyl tail. A microarray analysis showed that both compounds were general inhibitors of quorum sensing, i.e., the expression levels of most LasR-dependent genes were affected. Both compounds also inhibited the production of two quorum-sensing-dependent virulence factors, elastase and pyocyanin. These compounds should be useful for studies of LasR-dependent gene regulation and might serve as scaffolds for the identification of new quorum-sensing modulators.

Synthesis and biological evaluation of sulfonamidooxazoles and β-keto sulfones: selective inhibitors of 11β-hydroxysteroid dehydrogenase type I

The design, synthesis, and biological evaluation of arylsulfonamidooxazoles as 11beta-HSD1 inhibitors and the serendipitous discovery of beta-keto sulfones as potent 11beta-HSD1 inhibitors are described here. These two classes of compounds are not active against 11beta-HSD2 and therefore may have significant therapeutic potential for metabolic syndrome, type 2 diabetes and related metabolic dysfunctions.

Structure-activity relationships of N-(3,5-dimethoxy-4-n-octyloxycinnamoyl)-N'-(3,4-dimethylphenyl)piperazine and analogues as inhibitors of acyl-CoA: cholesterol O-acyltransferase

A novel series of acyl-CoA: cholesterol O-acyltransferase (ACAT) inhibitors were synthesized from a lead compound, 1-(4-hydroxy-3-methoxyphenyl)-7-phenylhept-1-en-3-one (1, Yakuchinone B) through a modification of three regions (A, B, C) in the molecule. In this study, the compounds prepared were tested for in vitro inhibitory activity on microsomal ACAT from the liver of rats and for in vivo hypocholesterolemic activity in rats given a high cholesterol diet. N-(3,5-Dimethoxy-4-n-octyloxycinnamoyl)-N'-(3,4-dimethylphenyl)piperazine (45), which belongs to the amide compounds, has finally been discovered. Compound 45 inhibited rat hepatic ACAT in a more striking manner than CI-976, an amide compound ACAT inhibitor, and it exhibited a high level of hypocholesterolemic activity in vivo. Since 45 strongly inhibited both microsomal ACAT prepared from HepG2 (a cell line derived from human hepatocarcinoma) and Caco2 (a cell line derived from human colon adenocarcinoma), there is speculation that 45 might have the ability to inhibit ACAT in both the human intestine and liver independent of the difference in the distribution of ACAT isozymes. On the other hand, 45 did not induce adrenotoxicity in subacute toxicity studies in rats. These results suggest that it has promise for development as a new therapeutic agent for hypercholesterolemia and atherosclerosis.

Inhibitors of acyl-CoA:cholesterol O-acyltransferase (ACAT). Part 1: identification and structure-activity relationships of a novel series of substituted N-alkyl-N-biphenylylmethyl-N'-arylureas

A series of N-alkyl-N-biphenylylmethyl-N'-arylurea and related derivatives represented by 1 have been prepared and evaluated for their ability to inhibit acyl-CoA:cholesterol O-acyltransferase in vitro and to lower plasma cholesterol levels in cholesterol-fed rats in vivo. Linking of two phenyl groups via oxygen and introduction of fluorine at appropriate positions on the biphenyl moiety improved in vitro and in vivo activity. From this series of analogs, compound 40 (FR179254), which had potent in vitro potency (rabbit intestinal microsomes IC50 = 25 nM), showed excellent plasma cholesterol-lowering activity when administered via the diet (ED50 = 0.045 mg/kg). However, the hypocholesterolemic effect of this compound was moderate when dosed by oral gavage in PEG400 as a vehicle (ED50 = 5.3 mg/kg). Modification of the N'-aryl moiety led to the identification of compound 50 (FR182980) which was efficacious in both dosing models (ED50 = 0.034 mg/kg and 0.11 mg/kg, respectively).