Discovery of 4'-(1,4-dihydro-indeno[1,2-c]pyrazol-3-yl)-benzonitriles and 4'-(1,4-dihydro-indeno[1,2-c]pyrazol-3-yl)-pyridine-2'-carbonitriles as potent checkpoint kinase 1 (Chk1) inhibitors

An extensive structure-activity relationship study of the 3-position of a series of tricyclic pyrazole-based Chk1 inhibitors is described. As a result, 4'-(1,4-dihydro-indeno[1,2-c]pyrazol-3-yl)-benzonitriles (4) and 4'-(1,4-dihydro-indeno[1,2-c]pyrazol-3-yl)-pyridine-2'-carbonitriles (29) emerged as new lead series. Compared with the original lead compound 2, these new leads fully retain the biological activity in both enzymatic inhibition and cell-based assays. More importantly, the new leads 4 and 29 exhibit favorable physicochemical properties such as lower molecular weight, lower Clog P, and the absence of a hydroxyl group. Furthermore, structure-activity relationship studies were performed at the 6- and 7-positions of 4, which led to the identification of ideal Chk1 inhibitors 49, 50, 51, and 55. These compounds not only potently inhibit Chk1 in an enzymatic assay but also significantly potentiate the cytotoxicity of DNA-damaging agents in cell-based assays while they show little single agent activity. A cell cycle analysis by FACS confirmed that these Chk1 inhibitors efficiently abrogate the G2/M and S checkpoints induced by DNA-damaging agent. The current work paved the way to the identification of several potent Chk1 inhibitors with good pharmacokinetics that are suitable for in vivo study with oral dosing.     

Synthesis,biological evaluation and docking analysis of 3-methyl-1-phenylchromeno[4,3-c]pyrazol-4(1H)-ones as potential cyclooxygenase-2 (COX-2) inhibitors

As a part of our continued efforts to discover new COX inhibitors, a series of 3-methyl-1-phenylchromeno[4,3-c]pyrazol-4(1H)-ones were synthesized and evaluated for in vitro COX inhibitory potential. Within this series, seven compounds (3a–d, 3h, 3k and 3q) were identified as potential and selective COX-2 inhibitors (COX-2 IC₅₀’s in 1.79–4.35 μM range; COX-2 selectivity index (SI) = 6.8–16.7 range). Compound 3b emerged as most potent (COX-2 IC₅₀ = 1.79 μM; COX-1 IC₅₀ >30 μM) and selective COX-2 inhibitor (SI >16.7). Further, compound 3b displayed superior anti-inflammatory activity (59.86% inhibition of edema at 5 h) in comparison to celecoxib (51.44% inhibition of edema at 5 h) in carrageenan-induced rat paw edema assay. Structure–activity relationship studies suggested that N-phenyl ring substituted with p-CF₃ substituent (3b, 3k and 3q) leads to more selective inhibition of COX-2. To corroborate obtained experimental biological data, molecular docking study was carried out which revealed that compound 3b showed stronger binding interaction with COX-2 as compared to COX-1.     

Synthesis and bioactivity studies on new 4-(3-(4-Substitutedphenyl)-3a,4-dihydro-3H-indeno[1,2-c]pyrazol-2-yl) benzenesulfonamides

A series of new 4-(3-(4-substitutedphenyl)-3a,4-dihydro-3H-indeno[1,2-c]pyrazol-2-yl) benzenesulfonamides (7–12) was synthesized starting from 2-(4-substitutedbenzylidene)-2,3-dihydro-1H-inden-1-one (1–6) and 4-hydrazinobenzenesulfonamide. The substituted benzaldehydes from which the key intermediate was prepared by introducing 2- or 4-substituents such as fluorine, hydroxy, methoxy, or the 3,4,5-trimethoxy moieties. The compounds were tested for their cytotoxicity, tumor-specificity and potential as carbonic anhydrase (CA, EC 4.2.1.1) inhibitors. The 3,4,5-trimethoxy and the 4-hydroxy derivatives showed interesting cytotoxic activities, which may be crucial for further anti-tumor activity studies, whereas some of these sulfonamides strongly inhibited both human (h) cytosolic isoforms hCA I and II.     

Synthesis and biological evaluation of 1-(2,4,5-trisubstituted phenyl)-3-(5-cyanopyrazin-2-yl)ureas as potent Chk1 kinase inhibitors

Based on the X-ray crystallography of our lead compound 1-(5-chloro-2,4-dimethoxyphenyl)-3-(5-cyanopyrazin-2-yl)urea in the checkpoint kinase 1 (Chk1) enzyme, we modified R4, and to a lesser extent, R2, and R5 of the phenyl ring, and made a variety of N-aryl-N'-pyrazinylurea Chk1 inhibitors. Enzymatic activity less than 20 nM was observed in 15 of 41 compounds. Compound 8i provided the best overall results in the cellular assays as it abrogated doxorubicin-induced cell cycle arrest (IC50=1.7 microM) and enhanced doxorubicin cytotoxicity (IC50=0.44 microM) while displaying no single agent activity.     

Synthesis and biological evaluation of 4-[3-biphenyl-2-yl-1-hydroxy-1-(3-methyl-3H-imidazol-4-yl)-prop-2-ynyl]-1-yl-benzonitrile as novel farnesyltransferase inhibitor

Farnesyltransferase inhibitors (FTIs) have emerged as a novel class of anti-cancer agents. Analogues of the potent FTI, 4-[3-biphenyl-1-hydroxy-1-(3-methyl-3H-imidazol-4-yl)-prop-2-ynyl]-1-yl-benzonitrile, were synthesized and tested in vitro for their inhibitory activities. The synthesis and detailed biological data of this series of analogues are presented.     

Design and biological evaluation of imidazo[1,2-a]pyridines as novel and potent ASK1 inhibitors

Imidazo[1,2-a]pyridine derivatives were designed, synthesized, and evaluated as inhibitors of the apoptosis signal-regulating kinase 1 (ASK1). These were based on a benzothiazole derivative that was discovered from high-throughput screening of our compound library. As a result, we identified potent, selective, and orally bioavailable ASK1 inhibitors for wide range of therapeutic targets.     

Synthesis and biological evaluation of benzo[4,5]imidazo[1,2-c]pyrimidine and benzo[4,5]imidazo[1,2-a]pyrazine derivatives as anaplastic lymphoma kinase inhibitors

Chromosomal translocations involving anaplastic lymphoma kinase (ALK) are the driving mutations for a range of cancers and ALK is thus considered an attractive therapeutic target. We synthesized a series of functionalized benzo[4,5]imidazo[1,2-c]pyrimidines and benzo[4,5]imidazo[1,2-a]pyrazines by an aza-Graebe–Ullman reaction, followed by palladium-catalyzed cross-coupling reactions. A sequential regioselective cross-coupling route is reported for the synthesis of unsymmetrically disubstituted benzo[4,5]imidazo[1,2-a]pyrazines. The inhibition of ALK was evaluated and compound 19 in particular showed good activity against both the wild type and crizotinib-resistant L1196M mutant in vitro and in ALK-transfected BaF3 cells.     

Synthesis and biological evaluation of thieno[3,2-c]pyrazol-3-amine derivatives as potent glycogen synthase kinase 3β inhibitors for Alzheimer’s disease

Glycogen synthase kinase 3β (GSK-3β) catalyses the hyperphosphorylation of tau protein in the Alzheimer’s disease (AD) pathology. A series of novel thieno[3,2-c]pyrazol-3-amine derivatives were designed and synthesised and evaluated as potential GSK-3β inhibitors by structure-guided drug rational design approach. The thieno[3,2-c]pyrazol-3-amine derivative 16b was identified as a potent GSK-3β inhibitor with an IC₅₀ of 3.1 nM in vitro and showed accepted kinase selectivity. In cell levels, 16b showed no toxicity on the viability of SH-SY5Y cells at the concentration up to 50 μM and targeted GSK-3β with the increased phosphorylated GSK-3β at Ser9. Western blot analysis indicated that 16b decreased the phosphorylated tau at Ser396 in a dose-dependent way. Moreover, 16b effectively increased expressions of β-catenin as well as the GAP43, N-myc, and MAP-2, and promoted the differentiated neuronal neurite outgrowth. Therefore, the thieno[3,2-c]pyrazol-3-amine derivative 16b could serve as a promising GSK-3β inhibitor for the treatment of AD.     

Synthesis and biological activity of ferrocenyl indeno[1,2-c]isoquinolines as topoisomerase II inhibitors

Three series of indeno[1,2-c]isoquinolines bearing a ferrocenyl entity were synthesized and evaluated for DNA interaction, topoisomerase I and II inhibition, and cytotoxicity against breast human cancer cell lines. In the first and second series, the ferrocenyl scaffold was inserted as a linker between the two nitrogen atoms. In the last series, it was introduced at the end of the carbon chain. The present study showed that the ferrocenyl entity enhanced the topoisomerase II inhibition. Most compounds showed a potent growth inhibitory effect on MDA-MB-231 cell line with the IC₅₀ in μM range.     

Synthesis and biological evaluation of 6,7-disubstituted 4-aminopyrido[2,3-d]pyrimidines as adenosine kinase inhibitors

The synthesis and structure-activity relationship of a series of 6,7-disubstituted 4-aminopyrido[2,3-d]pyrimidines as novel non-nucleoside adenosine kinase inhibitors is described. A variety of substituents, primarily aryl, at the C6 and C7 positions of the pyridopyrimidine core were found to yield analogues that are potent inhibitors of adenosine kinase. In contrast to the 5,7-disubstituted and 5,6,7-trisubstituted pyridopyrimidine series, these analogues exhibited only modest potency to inhibit AK in intact cells.     

Synthesis and biological evaluation of 5-substituted 1,4-dihydroindeno[1,2-c]pyrazoles as multitargeted receptor tyrosine kinase inhibitors

We report the synthesis and biological evaluation of 5-substituted 1,4-dihydroindeno[1,2-c]pyrazoles as multitargeted kinase inhibitors. Initial efforts focused on the development of selective KDR inhibitors, while later strategies involved the improvement of potency toward multiple kinase targets. Thus, several compounds were identified as potent KDR, Flt1, Flt3, and c-Kit inhibitors.     

3-[Benzimidazo- and 3-[benzothiadiazoleimidazo-(1,2-c)quinazolin-5-yl]-2H-chromene-2-ones as potent antimicrobial agents

A series of 3-[benzimidazo(1,2-c)quinazolin-5-yl]-2H-chromene-2-one (6a-6f) and 3-[benzothiadiazole- imidazo(1,2-c)quinazolin-5-yl]-2H-chromene-2-one derivatives (7a-7f) that incorporate a variety of substituents at the 6- and/or 8-positions of the coumarin moieties have been synthesized utilizing cellulose sulfuric acid as an efficient catalyst under both conventional heating and microwave irradiation procedures. These analogs were evaluated for their antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, Streptococcus pyogenes (Gram-positive bacteria), Escherichia Coli, Klebsiella pneumonia, Salmonella typhimurium (Gram-negative bacteria), and Aspergillus niger, Candida albicans, and Aspergillus flavus (Fungi). Two analogs, 6c (a 6,8-dichloro analog, MIC([SA]) = 2.5 μg/mL; MIC([ST]) = 2.5 μg/mL) and 7d (a 6,8-dibromo analog, MIC([ST]) = 2.5 μg/mL) were identified as potent antibacterial agents, and two analogs, 6b (a 6-bromo analog, MIC([AF]) = 10 μg/mL) and 6d (a 6,8-dibromo analog, MIC([AF]) = 15 μg/mL; MIC([CA]) = 15μg/mL), were identified as potent antifungal agents. Based on the MIC data, analogs 6b, 6c, 6d, and 7d were identified as the most potent antimicrobial agents in the series.     

Synthesis and biological evaluation of novel 6, 7-dimethoxy-3-(4-pyridyl)-2,3,3a,4-tetrahydroindeno[1,2-c]pyrazol-2-yl-4-substituted phenylmethanone/ethanone derivatives

A series of 6,7-dimethoxy-3-(4-pyridyl)-2,3,3a,4-tetrahydroindeno[1,2-c]pyrazol-2-yl-4-substituted phenylmethanone/ethanone derivatives were synthesized and in vitro activity against mycobacterium tuberculosis (MTB) and INHR-MTB were carried out. Among the synthesized compounds, compound (4h) 6,7-dimethoxy-3-(4-pyridyl)-2,3,3a,4-tetrahydroindeno[1,2-c]pyrazol-2-yl-4-pyridyl methanone was found to be the most active agent against MTB and INHR-MTB with a minimum inhibitory concentration of 0.22 μM.     

Synthesis and biological evaluation of novel 6, 7-dimethoxy-3-(4-pyridyl)-2,3,3a,4-tetrahydroindeno[1,2-c]pyrazol-2-yl-4-substituted phenylmethanone/ethanone derivatives

A series of 6,7-dimethoxy-3-(4-pyridyl)-2,3,3a,4-tetrahydroindeno[1,2-c]pyrazol-2-yl-4-substituted phenylmethanone/ethanone derivatives were synthesized and in vitro activity against mycobacterium tuberculosis (MTB) and INHR-MTB were carried out. Among the synthesized compounds, compound (4h) 6,7-dimethoxy-3-(4-pyridyl)-2,3,3a,4-tetrahydroindeno[1,2-c]pyrazol-2-yl-4-pyridyl methanone was found to be the most active agent against MTB and INHR-MTB with a minimum inhibitory concentration of 0.22 μM.     

Novel,potent and selective cyclin D1/CDK4 inhibitors: indolo[6,7-a]pyrrolo[3,4-c]carbazoles

The synthesis and CDK inhibitory properties of a series of indolo[6,7-a]pyrrolo[3,4-c]carbazoles is reported. In addition to their potent CDK activity, the compounds display antiproliferative activity against two human cancer cell lines. These inhibitors also effect strong G1 arrest in these cell lines and inhibit Rb phosphorylation at Ser780 consistent with inhibition of cyclin D1/CDK4.     

2-Phenyl-5,6-dihydro-2H-thieno[3,2-c]pyrazol-3-ol derivatives as new inhibitors of bacterial cell wall biosynthesis

Twenty-five 2-phenyl-5,6-dihydro-2H-thieno[3,2-c]pyrazol-3-ol derivatives were synthesized for evaluation as new inhibitors of bacterial cell wall biosynthesis. Many of them demonstrated good inhibitory activity against Staphylococcus aureus MurB, MurC and MurD enzymes in vitro and antimicrobial activity against gram-positive bacteria including MRSA, VRE and PRSP. However, when they were tested in the presence of 4% bovine serum albumin, the MIC values increased to greater than 128 microg/mL against PRSP. None of the compounds demonstrated activity against gram-negative bacteria at MIC <32 microg/mL.     

1,3-Dioxo-4-methyl-2,3-dihydro-1H-pyrrolo[3,4-c]quinolines as potent caspase-3 inhibitors

Synthesis, biological evaluation and structure-activity relationships for a series of novel nonpeptide small molecule inhibitors of caspase-3 are described. Among the studied compounds, 8-sulfamide derivatives of 1,3-dioxo-4-methyl-2,3-dihydro-1H-pyrrolo[3,4-c]quinolines have been identified as potent inhibitors of caspases-3. The most active compound within this series (8f) inhibited caspase-3 with IC(50)=4 nM.     

Synthesis and biological evaluation of 3-aryl-4-indolyl-maleimides as potent mutant isocitrate dehydrogenase-1 inhibitors

A series of 3-aryl-4-indolylmaleimide IDH1/R132H inhibitors with a novel structure was obtained by high-throughput screening and structure-based optimization. Most compounds such as 7a, 7d, 7h, 7i, 7k and 7o showed high inhibitory effects on IDH1/R132H and were highly selective against IDH1/WT, IDH2/WT, GDH, GK, and FBP. Evaluation of the biological activities and function at cellular level showed that compounds 7h, 7i and 7k could effectively suppress the production of 2-hydroxyglutaric acid in U87MG cells expressing IDH1/R132H. Additionally, 7h could reversed the differentiation block of the myeloid leukemic cell line, TF-1, caused by the overexpression of IDH1/R132H. We also explore the structure-activity relationship based on the experimental data, with an attempt to pave the way for future studies.     

Synthesis and biological evaluation of 2-(3'-(1H-tetrazol-5-yl) bicyclo[1.1.1]pent-1-yl)glycine (S-TBPG), a novel mGlu1 receptor antagonist

The design and synthesis of 2-(3'-(1H-tetrazol-5-yl)bicyclo[1.1.1]pent-1-yl)glycine (S-TBPG), a novel mGluR1 antagonist is reported. S-TBPG is characterized by the bioisosteric replacement of the distal carboxy group of 2-(3'-carboxybicyclo [1.1.1]pent-1-yl)glycine (S-CBPG) by a tetrazolyl moiety. Despite a moderate reduction in potency, S-TBPG is a selective mGluR1 antagonist (69 microM), with no activity at other mGluR subtypes. The interesting biological profile of S-TBPG, coupled with its peculiar chemical structure, is discussed in terms of the structure activity relationship (SAR) of mGluR1 antagonists.     

Synthesis and biological evaluation of the metabolites of 2-(1-{3-[(6-chloronaphthalen-2-yl)sulfonyl]propanoyl}piperidin-4-yl)-5-methyl-1,2-dihydro-3H-imidazo[1,5-c]imidazol-3-one

We have recently discovered imidazo[1,5-c]imidazol-3-one derivative 1 as a potent, selective, and orally bioavailable factor Xa (FXa) inhibitor. In this study, we have synthesized metabolites of 1 and evaluated their biological activities. As a result, we identified the active metabolites S-5 and 6 with a potent FXa inhibitory activity comparable to 1 and a favorable pharmacokinetic profile in monkeys.