Synthesis and evaluation of novel monosubstituted sulfonylurea derivatives as antituberculosis agents

Inhibitors of acetohydroxyacid synthase as promising agents against non-tuberculous mycobacterial diseases

Acetohydroxyacid synthase (AHAS), exclusively present in microorganisms and plants, is a promising target for several herbicides due to its catalytic role in the branched-chain amino acid biosynthetic pathway. Previous studies have shown that K13787, a pyrazolopyrimidine sulfonamide AHAS inhibitor, was moderately effective against pulmonary infection caused by M. tuberculosis and nontuberculous mycobacteria (NTM). In this study, we synthesized various structural derivatives of K13787 based on the molecular docking studies and assessed their MICs against mycobacteria species. Among the synthetic compounds screened, K13787, along with KNT2077 and KNT2099, exhibited inhibitory efficacy against M. avium and M. abscessus, including CLR-resistant NTM species. Notably, these compounds displayed a synergistic effect (FIC ≤ 0.5) when combined with CLR against M. avium and M. abscessus. Our findings suggest that these newly identified AHAS-targeted compounds hold promise as lead candidates for novel antimycobacterial agents against NTM infections. Considering the structure-activity relationship, K13787, KNT2077, and KTN2099 emerge as potential treatments for NTM species.

Novel Sulfonylurea Derivatives as Potential Antimicrobial Agents: Chemical Synthesis, Biological Evaluation, and Computational Study

Methicillin-resistant Staphylococcus aureus (MRSA) is a worldwide health threat and has already tormented humanity during its long history, creating an urgent need for the development of new classes of antibacterial agents. In this study, twenty-one novel sulfonylurea derivatives containing phenyl-5-vinyl and pyrimidinyl-4-aryl moieties were designed and synthesized, among which, nine compounds exhibited inhibitory potencies against Gram-positive bacterial strains: MRSA (Chaoyang clinical isolates), S. aureus ATCC6538, vancomycin-resistant Enterococci-309 (VRE-309), and Bacillus subtilis ATCC 6633. Especially, 9i and 9q demonstrated inhibitory activities against the four bacterial strains with minimum inhibitory concentrations (MICs) of 0.78-1.56 μg/mL, and quite a few of other MRSA clinical strains with MICs of 0.78 μg/mL, superior to those of the positive controls vancomycin (MIC of 1 μg/mL) and methicillin (MIC of >200 μg/mL). This is the very first time that sulfonylurea derivatives have been identified as promising inhibitors against different MRSA clinical isolates. In addition, all the MIC values of the synthesized compounds against Candida albicans were greater than 100 μg/mL. Since the reported anti-Candida activities of sulfonylureas were due to acetohydroxyacid synthase (AHAS) inhibition, the molecular target against MRSA for the target sulfonylureas was thought to be a different mode of action. Density functional theory (DFT) calculations were finally performed to understand the structure-activity relationships, based on which, significant differences were observed between their HOMO maps for compounds with strong antibacterial activities and weak anti-MRSA effects. The present results hence provide valuable guidance for the discovery of novel agents to treat bacterial infections, especially against MRSA.

Chemical preparation, degradation analysis, computational docking and biological activities of novel sulfonylureas with 2,5-disubstituted groups

Based on the previous finding that a substitution at 5-position of the benzene ring is favorable to enhance the degradation rates of sulfonylurea herbicides, a total of 16 novel 2,5-disubsituted sulfonylurea compounds were chemically synthesized and fully characterized by means of ¹H NMR, ¹³C NMR, HRMS and X-ray diffraction. By using HPLC analysis, the degradation behavior of M03, a compound belonging to this family, was studied and confirmed that chlorsulfuron itself is not a degraded product of the 2,5-disubstituted sulfonylureas. Inhibition constants against plant acetohydroxyacid synthase (AHAS) were determined for selected compounds, among which SU3 showed seven times stronger activity against the mutant W574L enzyme than chlorsulfuron. Molecular docking suggested that the substituted group at 5-position of benzene ring is likely to interact with the surrounding residues Met200 and Asp376 of AtAHAS. From the greenhouse herbicidal assay and crop safety test, SU5 and SU6 are considered as herbicide candidates to control dicotyledon weeds in corn, while SU3 is likely to be a promising candidate to control dicotyledon weed species and barnyard grass in wheat. The present research has therefore provided some new insights to understand the structure-activity relationships of herbicidal sulfonylureas with di-substitutions at benzene ring.

Synthesis, Herbicidal Activity, Crop Safety and Soil Degradation of Pyrimidine- and Triazine-Substituted Chlorsulfuron Derivatives

Chlrosulfuron, a classical sulfonylurea herbicide that exhibits good safety for wheat but causes a certain degree of damage to subsequent corn in a wheat-corn rotation mode, has been suspended field application in China since 2014. Our previous study found that diethylamino-substituted chlorsulfuron derivatives accelerated the degradation rate in soil. In order to obtain sulfonylurea herbicides with good crop safety for both wheat and corn, while maintaining high herbicidal activities, a series of pyrimidine- and triazine-based diethylamino-substituted chlorsulfuron derivatives (W102-W111) were systematically evaluated. The structures of the synthesized compounds were confirmed with 1H NMR, 13C NMR, and HRMS. The preliminary biological assay results indicate that the 4,6-disubstituted pyrimidine and triazine derivatives could maintain high herbicidal activity. It was found that the synthesized compounds could accelerate degradation rates, both in acidic and alkaline soil. Especially, in alkaline soil, the degradation rate of the target compounds accelerated more than 22-fold compared to chlorsulfuron. Moreover, most chlorsulfuron analogs exhibited good crop safety for both wheat and corn at high dosages. This study provided a reference for the further design of new sulfonylurea herbicides with high herbicidal activity, fast degradation rates, and high crop safety.

Discovery of ortho-Alkoxy Substituted Novel Sulfonylurea Compounds That Display Strong Herbicidal Activity against Monocotyledon Grasses

In the present study, we have designed and synthesized a series of 42 novel sulfonylurea compounds with ortho-alkoxy substitutions at the phenyl ring and evaluated their herbicidal activities. Some target compounds showed excellent herbicidal activity against monocotyledon weed species. When applied at 7.5 g ha^-1, 6-11 exhibited more potent herbicidal activity against barnyard grass (Echinochloa crus-galli) and crab grass (Digitaria sanguinalis) than commercial acetohydroxyacid synthase (AHAS; EC 2.2.1.6) inhibitors triasulfuron, penoxsulam, and nicosulfuron at both pre-emergence and postemergence conditions. 6-11 was safe for peanut for postemergence application at this ultralow dosage, suggesting that it could be considered a potential herbicide candidate for peanut fields. Although 6-11 and triasulfuron share similar chemical structures and have close K_i values for plant AHAS, a significant difference has been observed between their LUMO maps from DFT calculations, which might be a possible factor that leads to their different behaviors toward monocotyledon weed species.

Synthesis and evaluation of α-glucosidase inhibitory activity of sulfonylurea derivatives

Two series of sulfonylureas derivatives including 24 compounds (4, 7, 5a–5o, 8a–8h), among them 17 new derivatives, have been synthesized and evaluated for their α-glucosidase inhibitory activity. Compounds 5c, 5h and 8e showed significant in vitro α-glucosidase inhibition with IC50 values of 5.58, 79.85 and 213.36 µm, respectively, comparing with the standard compounds acarbose (IC50 = 268.29 µm) and glipizide (IC50 = 300.47 µm). The preliminary structure-activity relationships (SARs) of the synthesized compounds were also investigated.

Synthesis, herbicidal activity study and molecular docking of novel pyrimidine thiourea

According to the pharmacophore binding strategy and principle of bioelectronic isobaric, used the sulfonylurea bridge as the parent structure, a series of novel thiourea compounds containing aromatic-substituted pyrimidines were designed and synthesized. The preliminary herbicidal activity tests showed that some compounds had good herbicidal activity against Digitaria adscendens, Amaranthus retroflexus, especially for compound 4d and 4f. The results showed that compound 4d had an inhibition rate of 81.5% on the root growth of Brassica napus L. at the concentration of 100 mg L^-1, and compound 4f had an inhibition rate of 81% on the root growth of Digitaria adscendens at the concentration of 100 mg L^-1. Compounds 4d and 4f had higher comparative activity on Echinochloa crus-galli than the commercial herbicide bensulfuron-methyl. The preliminary structure-activity relationship (SAR) was also summarized. We also tested the in vivo AHAS enzyme activity inhibition experiment of 14 compounds at 100 mg L^-1, and the results showed that they all have inhibitory activity on the enzyme, with the highest inhibition rate reaching 44.4% (compound 4d). Based on the results of molecular docking to yeast acetohydroxyacid synthase (AHAS), the possible herbicidal activity mechanism of these compounds was evaluated.

Research on the controllable degradation of N-methylamido and dialkylamino substituted at the 5th position of the benzene ring in chlorsulfuron in acidic soil

Owing to the lengthy residual problems associated with chlorsulfuron, metsulfuron-methyl, and ethametsulfuron, which prevents them from being used in the "annual multi-crop planting system", the application of these sulfonylurea herbicides (SU) has regrettably been terminated in China since 2014. In this field, we were the first to discover that the 5th position of the benzene ring in chlorsulfuron is a key point for influencing its degradation rate and the amino moiety at this position showed faster degradation rates and maintained their original potent bioactivity. In this study, we further elaborated on N-methylamido and dialkylamino substituents at the same position in chlorsulfuron to obtain 18 novel structures as M and N series. Their half-life degradation (DT50) values were faster, to varying degrees, than chlorsulfuron in acidic soil. It was found that most of the titled structures also retained their potent herbicidal activity and the crop safety of the M series towards corn greatly increased. Based on these data, a comprehensive graph describing the structure/degradation relationship was established first. Relating to the new molecules, their herbicidal activity (A), degradation rates (D), and crop safety (S) relationship were correlated and we used this approach to predict and explore the most preferable molecule, which coincided to the corresponding experimental data. The new concept of controllable degradation will provide us with more insight when searching for new ecological bioactive molecules in the future.

Development of Benzenesulfonamide Derivatives as Potent Glutathione Transferase Omega-1 Inhibitors

Glutathione transferase omega-1 (GSTO1-1) is an enzyme whose function supports the activation of interleukin (IL)-1β and IL-18 that are implicated in a variety of inflammatory disease states for which small-molecule inhibitors are sought. The potent reactivity of the active-site cysteine has resulted in reported inhibitors that act by covalent labeling. In this study, structure-activity relationship (SAR) elaboration of the reported GSTO1-1 inhibitor C1-27 was undertaken. Compounds were evaluated for inhibitory activity toward purified recombinant GSTO1-1 and for indicators of target engagement in cell-based assays. As covalent inhibitors, the kinact/KI values of selected compounds were determined, as well as in vivo pharmacokinetics analysis. Cocrystal structures of key novel compounds in complex with GSTO1-1 were also solved. This study represents the first application of a biochemical assay for GSTO1-1 to determine kinact/KI values for tested inhibitors and the most extensive set of cell-based data for a GSTO1-1 inhibitor SAR series reported to date. Our research culminated in the discovery of 25, which we propose as the preferred biochemical tool to interrogate cellular responses to GSTO1-1 inhibition.

A Qualified Success: Discovery of a New Series of ATAD2 Bromodomain Inhibitors with a Novel Binding Mode Using High-Throughput Screening and Hit Qualification

The bromodomain of ATAD2 has proved to be one of the least-tractable proteins within this target class. Here, we describe the discovery of a new class of inhibitors by high-throughput screening and show how the difficulties encountered in establishing a screening triage capable of finding progressible hits were overcome by data-driven optimization. Despite the prevalence of nonspecific hits and an exceptionally low progressible hit rate (0.001%), our optimized hit qualification strategy employing orthogonal biophysical methods enabled us to identify a single active series. The compounds have a novel ATAD2 binding mode with noncanonical features including the displacement of all conserved water molecules within the active site and a halogen-bonding interaction. In addition to reporting this new series and preliminary structure-activity relationship, we demonstrate the value of diversity screening to complement the knowledge-based approach used in our previous ATAD2 work. We also exemplify tactics that can increase the chance of success when seeking new chemical starting points for novel and less-tractable targets.

Chemical preparation, biological evaluation and 3D-QSAR of ethoxysulfuron derivatives as novel antifungal agents targeting acetohydroxyacid synthase

Accetohydroxyacid synthase (AHAS) is the first enzyme involved in the biosynthetic pathway of branched-chain amino acids. Earlier gene mutation of Candida albicans in a mouse model suggested that this enzyme is a promising target of antifungals. Recent studies have demonstrated that some commercial AHAS-inhibiting sulfonylurea herbicides exerted desirable antifungal activity. In this study, we have designed and synthesized 68 novel ethoxysulfulron (ES) derivatives and evaluated their inhibition constants (K_i) against C. albicans AHAS and cell based minimum inhibitory concentration (MIC) values. The target compounds 5-1, 5-10, 5-22, 5-31 and 5-37 displayed stronger AHAS inhibitions than ES did. Compound 5-1 had the best K_i of 6.7 nM against fungal AHAS and MIC values of 2.5 mg/L against Candida albicans and Candica parapsilosis after 72 h. A suitable nematode model was established here and the antifungal activity of 5-1 was further evaluated in vivo. A possible binding mode was simulated via molecular docking and a comparative field analysis (CoMFA) model was constructed to understand the structure-activity relationship. The current study has indicated that some ES derivatives should be considered as promising hits to develop antifungal drugs with novel biological target.

Synthesis and insecticidal activity of novel pyrimidine derivatives containing urea pharmacophore against Aedes aegypti

BACKGROUND

Aedes aegypti is a major mosquito vector for the transmission of serious diseases, especially dengue and yellow fever. More than 1 billion people in developing countries are at risk. The widespread and continual use of pesticides can lead to resistant mosquitoes. In order to maintain mosquito control gains, it is critical to develop and evaluate novel bioactive molecules that differ in mode of action from currently used products.

RESULTS

A series of novel pyrimidine derivatives were designed and synthesized. Their structures were elucidated by proton nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry. The biological activities of these compounds were tested against Ae. aegypti. Many of them exhibited insecticidal activity against adult and larval mosquitoes. Compound 4d displayed relatively good activity to reach 70% mortality at 2 µg mL^-1 . Furthermore, density functional theory calculations were established to study the structure-activity relationship of these novel compounds.

CONCLUSION

A practical synthetic route for pyrimidine derivatives is presented. This study suggests that these pyrimidine derivatives exhibit some activity against the yellow fever mosquito and, with further structure modification, could be novel lead compounds for the development of insecticides against mosquitoes. © 2016 Society of Chemical Industry.

Design, synthesis and SAR study of novel sulfonylureas containing an alkenyl moiety

A series of sulfonylurea compounds was designed and synthesized via introducing an alkenyl moiety into the aryl-5 position and most title compounds exhibited enhanced antifungal activities and limited herbicidal activities compared with chlorsulfuron. Then, a CoMSIA calculation for antifungal activities was carried out to establish a 3D-QSAR model in which a cross-validated q(2) of 0.585 and a correlation coefficient r(2) of 0.989 were obtained. The derived model revealed that hydrophobic and electrostatic fields were the two most important factors for antifungal activity. Structure optimization was performed according to the CoMSIA model and compound 9z was found to be as potent as chlorothalonil in vitro against C. cornigerum, the pathogen of the wheat sharp eyespot disease. In order to study the fungicidal mechanism, 9z was successfully docked into yeast AHAS using a flexible molecular docking method and the resulting binding pattern was similar to that of chlorimuron-ethyl, indicating that the antifungal activity of compounds 9 was probably due to the inhibition of fungal AHAS.

Syntheses, biological activities and SAR studies of novel carboxamide compounds containing piperazine and arylsulfonyl moieties

A series of novel carboxamide compounds 19a-19j, 20a-20j and 22a-22d containing piperazine and arylsulfonyl moieties have been synthesized. The bioassay results showed that some compounds exhibited favorable herbicidal activities against dicotyledonous plants and many of them possessed excellent antifungal activities. Among 24 novel compounds, some showed superiority over the commercial fungicides Chlorothalonil, Dimethomorph, Thiophanate-methyl, Iprodione, and Zhongshengmycin at 500 mg/L concentration. Some compounds also exhibited high KARI inhibitory activity at 100 μg/mL concentration and could be used as new KARI lead inhibitors for further studies. Moreover, SAR of these new compounds were comprehensively investigated using different computational methods in which 3D-QSAR model obtained provided useful information for further structural optimization for the discovery of new fungicides. The results of this research will contribute to explore comprehensive biological activities of piperazine-containing compounds in different areas of chemistry.

Research on controllable degradation of sulfonylurea herbicides

Through studying structure, bioassay and soil degradation tri-factor relationship, potential controllable degradation of SU was firstly explored and summarized.

Synthesis and oral hypoglycemic effect of novel thiazine containing trisubstituted benzenesulfonylurea derivatives

A new series of 3-(4-substituted phenyl)-1-(4-(4,6-dimethyl-6H-1,3-thiazin-2-yl)phenylsulfonyl)-1-substituted urea (5a-o) was synthesized by an effectual route via sulfonylcarbamates and explores the novel site for substitution in sulfonylurea as well as the way of thiazine can be prepared. The molecules were established by elemental analysis and spectroscopic viz. IR, (1)H NMR, (13)C NMR and MS techniques. All the fifteen derivatives were shown very prominent oral hypoglycemic effect at the dose of 40 mg/kg body weight (p.o.) in respect of standard drug glibenclamide and control. The hypoglycemic effect was studied using oral glucose tolerance test in normal and NIDDM in STZ-rat model. The compounds 5a, 5d, 5f, 5i, 5k and 5n were dominant out of fifteen derivatives for blood glucose lowering activity (more than 80%) when comparing with NIDDM control. These derivatives were either containing simply phenyl ring (5a, 5f and 5k) on to the second amine of sulfonylurea (R' = H) or nitro group at the para position in compound 5d, 5i and 5n (R' = NO2 ) to produce significant oral hypoglycemic effect. Other structural activity relationship is also observed regarding the heteroaromatic and substituted aromatic group at R and R' position respectively.

Synthesis of Novel 1-(4-Substituted pyridine-3-sulfonyl)-3-phenylureas with Potential Anticancer Activity

A series of novel 4-substituted-N-(phenylcarbamoyl)-3-pyridinesulfonamides 11–27 have been synthesized by the reaction of 4-substituted pyridine-3-sulfonamides 2–10 with the appropriate aryl isocyanates in presence of potassium carbonate. The in vitro anticancer activity of compounds 11, 12, 14–21 and 24–26 was evaluated at the U.S. National Cancer Institute and in light of the results, some structure-activity relationships were discussed. The most prominent compound, N-[(4-chlorophenyl)carbamoyl]-4-[4-(3,4-dichlorophenyl)piperazin-1-yl]pyridine-3-sulfonamide (21) has exhibited a good activity profile and selectivity toward the subpanels of leukemia, colon cancer and melanoma, with average GI₅₀ values ranging from 13.6 to 14.9 µM.

Development of ssDNA aptamers as potent inhibitors of Mycobacterium tuberculosis acetohydroxyacid synthase

Acetohydroxyacid synthase (AHAS) from Mycobacterium tuberculosis (Mtb) is a promising potential drug target for an emerging class of new anti-tuberculosis agents. In this study, we identify short (30-mer) single-stranded DNA aptamers as a novel class of potent inhibitors of Mtb-AHAS through an in vitro DNA-SELEX method. Among all tested aptamers, two candidate aptamers (Mtb-Apt1 and Mtb-Apt6) demonstrated the greatest inhibitory potential against Mtb-AHAS activity with IC50 values in the low nanomolar range (28.94±0.002 and 22.35±0.001 nM respectively). Interestingly, inhibition kinetics analysis of these aptamers showed different modes of enzyme inhibition (competitive and mixed type of inhibition respectively). Secondary structure-guided mutational modification analysis of Mtb-Apt1 and Mtb-Apt6 identified the minimal region responsible for their inhibitory action and consequently led to 17-mer and 20-mer shortened aptamers that retained equivalent or greater inhibitory potential. Notably, a modeling and docking exercise investigated the binding site of these two potent inhibitory aptamers on the target protein and showed possible involvement of some key catalytic dimer interface residues of AHAS in the DNA-protein interactions that lead to its potent inhibition. Importantly, these two short candidate aptamers, Mtb-Apt1 (17-mer) and Mtb-Apt6 (20-mer), also demonstrated significant growth inhibition against multidrug-resistant (MDR-TB) and extensively drug-resistant (XDR-TB) strains of tuberculosis with very low MIC of 5.36 μg/ml and 6.24 μg/ml, respectively and no significant cytotoxicity against mammalian cell line. This is the first report of functional inhibitory aptamers against Mtb-AHAS and provides the basis for development of these aptamers as novel and strong anti-tuberculosis agents.

Role of a highly conserved proline-126 in ThDP binding of Mycobacterium tuberculosis acetohydroxyacid synthase

Acetohydroxyacid synthase (AHAS) of Mycobacterium tuberculosis is a promising target for the development of anti-tuberculosis agents. With the absence of an available bacterial AHAS crystal structure, that of M. tuberculosis, site-directed mutagenesis has been a useful tool for determining its structural and functional features. In this study, a highly conserved proline residue (P126 of M. tuberculosis AHAS) was selected, and the possible role was evaluated by site-directed mutagenesis. P126 was replaced by valine, threonine, alanine, and glutamate to yield P126V, P126T, P126A, and P126E, respectively. All variants were expressed in their soluble forms in Escherichia coli and purified to near homogeneity. The molecular mass (SDS-PAGE) of the purified variants was ∼68 kDa, which is similar to that of wild-type AHAS. The P126V, P126T, and P126A variants exhibited significantly lower activity than wild-type AHAS, whereas P126E was inactive under the tested assay conditions. Furthermore, the P126V and P126T variants showed a significantly decreased preference toward pyruvate and ThDP as substrate and cofactor respectively, whereas the P126A showed similar kinetics to that of wild-type AHAS. Like in AHAS from yeast Saccharomyces cerevisiae (PDB ID: 1N0H), residue P126 is located in the ThDP binding pocket of M. tuberculosis AHAS homology model. Collectively, these results suggest that the conserved P126 plays a significant role in the ThDP binding of M. tuberculosis AHAS.