Design,Synthesis and Biological Evaluation of Imidazo[1,2‐a]pyridine Derivatives as Novel DPP‐4 Inhibitors

A new series of DPP‐4 inhibitors with imidazo[1,2‐a]pyridine scaffold were designed by exploiting scaffold hopping strategy and docking study. Based on docking binding model, structural modifications of 2‐benzene ring and pyridine moieties of compound 5a led to the identification of compound 5d with 2, 4‐dichlorophenyl group at the 2‐position as a potent (IC₅₀ = 0.13 μm ), selective (DPP‐8/DPP‐4 = 215 and DPP‐9/DPP‐4 = 192) and in vivo efficacious DPP‐4 inhibitor. Further, molecular docking revealed that compound 5d could retain key binding features of DPP‐4 with the pyridine moiety of imidazo[1,2‐a]pyridine ring providing an additional π?π interaction with Phe357 of DPP‐4. Compound 5d might be a promising lead for further development of novel DPP‐4 inhibitor treating T2DM.     

Synthesis and mycobacterial evaluation of 5‐substituted‐6‐acetyl‐2‐amino‐7‐methyl‐5,8‐dihydropyrido‐[2,3‐d]pyrimidin‐4(3H)‐one derivatives

5‐Substituted‐6‐acetyl‐2‐amino‐7‐methyl‐5,8‐dihydropyrido[2,3‐d]pyrimidin‐4(3H)‐one derivatives were synthesized and evaluated against Mycobacterium tuberculosis H37Rv, Mycobacterium aurum, Escherichia coli, and Staphylococcus aureus as well as a human monocyte‐derived macrophage (THP‐1), and murine macrophage (RAW 264.7) cell lines to assess their antibacterial and cytotoxic potential, respectively. The compounds showed activity in the range of 1.95–125 µg/ml against M. tuberculosis but showed no activity against M. aurum, E. coli, and S. aureus, indicating selectivity towards slow‐growing mycobacterial pathogens. The compounds exhibited very low to no cytotoxicity up to 500 µg/ml concentration against eukaryotic cell lines. The most potent molecule, 2l , showed a minimum inhibitory concentration of 1.95 µg/ml against M. tuberculosis H37Rv and a selectivity index of >250 against both the eukaryotic cell lines. Furthermore, 2l showed moderate inhibition of whole‐cell mycobacterial drug‐efflux pumps when compared to verapamil, a known potent inhibitor of efflux pumps. Thus, derivative 2l was identified as an antituberculosis hit molecule, which could be used to yield more potent lead molecules.     

6‐Substituted Indolo[1,2‐c]quinazolines as New Antimicrobial Agents

A series of 2‐o‐arylidineaminophenylindoles and their cyclic derivatives (indolo[1,2‐c]quinazolines) were synthesized. The reactions occurred under relatively mild conditions and afforded the desired product in good yields. Molecular structures of the synthesized compounds were confirmed by IR, ¹H‐NMR, ¹³C‐NMR, MS spectra, and elemental analyses. Furthermore, all the final products were screened for in‐vitro antibacterial activity against three Gram‐positive and three Gram‐negative bacteria and also tested for their inhibitory action against three strains of fungi. Compound IIc showed potent activity against all the bacterial (except S. typhimurium) and fungal strains. Especially, compounds IIi and IIj which have isoquinolyl and pyridyl substituents displayed potent antibacterial as well as antifungal activities compared to those of the respective standard drugs Ampicillin and Ketoconazole.     

Synthesis and Anticonvulsant Activity of 5‐Phenyl‐[1,2,4]‐triazolo[4,3‐a]quinolines

A series of novel 5‐phenyl‐[1,2,4]‐triazolo[4,3‐a]quinoline derivatives was synthesized by the cyclization of 2‐chloro‐4‐phenyl‐1,2‐dihydronaphthalene with formohydrazide. The starting material 2‐chloro‐4‐phenyl‐1,2‐dihydronaphthalene was synthesized from ethyl‐3‐oxo‐3‐phenylpropanoate and substituted aniline. Their anticonvulsant activities were evaluated by the maximal electroshock (MES) test and their neurotoxicity was evaluated by the rotarod neurotoxicity test (Tox). The maximal electroshock test showed that 7‐hexyloxy‐5‐phenyl‐[1,2,4]‐triazolo[4,3‐a]quinoline 4f was found to be the most potent compound with an ED₅₀ value of 6.5 mg/kg and a protective index (PI = ED₅₀ / TD₅₀) value of 35.1, which was much higher than the PI of the reference drug phenytoin.     

Synthesis and In‐Vitro Anti‐Hepatitis‐B Virus Activity of 6H‐[1]Benzothiopyrano[4,3‐b] quinolin‐10‐ols

A series of 9‐methoxy‐6H‐[1]benzothiopyrano[4,3‐b]quinolin‐10‐ols with a Mannich side chain were synthesized and evaluated for their anti‐Hepatitis B virus (HBV) activity in HepG2.2.15 cells. Some compounds showed significant anti‐HBV activity with IC₅₀ values less than 41 μM. Among them, compound 9b was the most effective anti‐HBV agent (IC₅₀ = 1.7 μM, SI = 60.3).     

New insights into the mechanism of action of pyrazolo[1,2‐a]benzo[1,2,3,4]tetrazin‐3‐one derivatives endowed with anticancer potential

Due to the scarce biological profile, the pyrazolo[1,2‐a]benzo[1,2,3,4]tetrazine‐3‐one scaffold (PBT) has been recently explored as promising core for potential anticancer candidates. Several suitably decorated derivatives (PBTs) exhibited antiproliferative activity in the low‐micromolar range associated with apoptosis induction and cell cycle arrest on S phase. Herein, we selected the most active derivatives and submitted them to further biological explorations to deepen the mechanism of action. At first, a DNA targeting is approached by means of flow Linear Dichroism experiments so as to evaluate how small planar molecules might interact with DNA, including the interference with the catalytic cycle of topoisomerase II and the influence on the cleavable complex stabilization (poisoning effect). In support of the experimental data, in silico studies have been achieved to better understand the chemical space of the interactions. Interestingly some meaningful structural features, useful for further developments, were found. The 8,9‐di‐Cl substituted derivative revealed as the most effective in the intercalative process, as well as on the inhibition of catalytic activity of topoisomerase II. Predicted ADME studies confirm that PBTs are promising as potential drug candidates.     

Synthesis and Anticonvulsant Activity of 6‐Alkoxy‐[1,2,4]Triazolo[3,4‐a]Phthalazines

A new series of 6‐alkoxy‐[1,2,4]triazolo[3,4‐a]phthalazines ( 3a – 3v ) were synthesized and their anticonvulsant activity and neurotoxicity were evaluated by the maximal electroshock test and the rotarod test respectively. Significant anticonvulsant activity was displayed by a number of compounds. The most promising compounds 6‐(4‐chlorobenzyloxy)‐[1,2,4]triazolo[3,4‐a]phthalazine ( 3f) and 6‐heptyloxy‐[1,2,4]triazolo[3,4‐a]phthalazine ( 3s) showed a median effective dose of 7.1 and 11.0 mg/kg, and had protective index value of 5.2 and 8.0 respectively. The two compounds were further found to have potent activity against seizures induced by pentylenetetrazole, isoniazid, thiosemicarbazide, 3‐mercaptopropionic acid but not seizures induced by strychnine, indicating that the two compounds might function by enhancing gamma‐aminobutyric acid neurotransmission.     

Anti‐anxiety and sedative profile evaluation of imidazo[1,2‐a]pyridine derivatives

Three imidazo[1,2‐a]pyridine‐3‐nitrosated (L‐1, L‐2, L‐3) and a 3‐formyl imidazo[1,2‐a]pyridine thiosemicarbazone (L‐4) were synthesized and evaluated for their effects in the elevated plus maze, burying behavior test, rotarod performance, the horizontal wire test, and locomotor activity. L‐2 and L‐3 increased the percent time spent in the open arms of the plus maze at doses of 1 and 2 mg/kg without modifying the number of total entries. In addition, L‐2 and L‐3 (1 mg/kg) increased the number of open arm entries indicating anxiolytic‐like activity at this dose. In the burying behavioral test, L‐1 (2–8 mg/kg), L‐2 (8 mg/kg), and L‐3 (4 and 8 mg/kg), induced a clear reduction in cumulative burying behavior, without modifying burying behavior latency, thus reducing experimental anxiety. In the rotarod test, L‐1 and L‐2 impaired rotarod performance only at the highest evaluated dose (64 mg/kg) at which reduction of motor activity was observed and thereby no conclusions about myorelaxant effects can be proposed. All compounds showed a clear sedative effect and corresponding ED₅₀ values were obtained. Results indicate that compounds L‐1, L‐2, and L‐3 show a sedative and an anxiolytic profile. Drug Dev Res 71:371–381, 2010. © 2010 Wiley‐Liss, Inc.     

Synthesis and Biological Evaluation of [1,2,4]Triazolo[3,4‐a]phthalazine and Tetrazolo[5,1‐a]phthalazine Derivatives Bearing Substituted Benzylpiperazine Moieties as Positive Inotropic Agents

Two series of [1,2,4]triazolo[3,4‐a]phthalazine and tetrazolo[5,1‐a]phthalazine derivatives bearing substituted benzylpiperazine moieties have been synthesized and evaluated for their positive inotropic activity by measuring left atrium stroke volume on isolated rabbit heart preparations. The majority of the derivatives exhibited better in vitro activity than the existing drug, milrinone, and 6‐((4‐(4‐methoxyphenyl)piperazin‐1‐yl)methyl)tetrazolo[5,1‐a]phthalazine. 8 m in particular was identified as the most potent with an increased stroke volume of 12.02 ± 0.20% (milrinone: 2.46 ± 0.07%) at a concentration of 3 × 10^–5 m . The chronotropic effects of the compounds that exhibited good potency were also evaluated.     

Design,synthesis, and negative inotropic evaluation of 4‐phenyl‐1H‐1,2,4‐triazol‐5(4H)‐one derivatives containing triazole or piperazine moieties

In this study, four novel series of 4‐phenyl‐1H ‐1,2,4‐triazol‐5(4H )‐one derivatives containing triazole or piperazine moieties were designed, synthesized, and evaluated for negative inotropic activity by measuring the left atrium stroke volume in isolated rabbit heart preparations. Almost all of the compounds showed an ability to moderate the cardiac workload by decreasing the heart rate and contractility. Among them, 7h was found to be the most potent with a change in stroke volume of ?48.22 ± 0.36% at a concentration of 3 × 10^?5 mol/L (metoprolol: ?9.74 ± 0.14%). The cytotoxicity of these compounds was evaluated using the human cervical cancer cell line HeLa, the liver cancer cell line Hep3B, and the human normal hepatic cell line LO 2. A preliminary study of the mechanism of action for the compound 7h on the regulation of atrial dynamics with ATP ‐sensitive K⁺ channel and L‐type Ca²⁺ channel blockers glibenclamide and nifedipine was performed in the isolated perfused beating rabbit atria.     

Discovery of Novel 2‐(piperidin‐4‐yl)‐1H‐benzo[d]imidazole Derivatives as Potential Anti‐Inflammatory Agents

A novel 2‐(piperidin‐4‐yl)‐1H‐benzo[d]imidazole derivative 5 with good anti‐inflammatory activity was identified from our in‐house library. Based on hit compound 5 , two series of 2‐(piperidin‐4‐yl)‐1H‐benzo[d]imidazole derivative 6a – g and 7a – h were designed and synthesized as novel anti‐inflammatory agents. Most of synthesized compounds exhibited good inhibitory activity on NO and TNF‐α production in LPS‐stimulated RAW 264.7 macrophages, in which the compound 6e showed most potent inhibitory activity on NO (IC₅₀ = 0.86 μm ) and TNF‐α (IC₅₀ = 1.87 μm ) production. Further evaluation revealed that compound 6e displayed more potent in vivo anti‐inflammatory activity than ibuprofen did on xylene‐induced ear oedema in mice. Additionally, Western blot analysis revealed that compound 6e could restore phosphorylation level of IκBα and protein expression of p65 NF‐κB in LPS‐stimulated RAW 264.7 macrophages.     

Synthesis of [1,2‐3H]ethylamine hydrochloride and [3H]‐labeled apadenoson for a human ADME study

Tritium‐labeled [1,2‐³H]ethylamine hydrochloride was prepared through a multiple‐step sequence in high radioactive specificity. The labeled amine was isolated in high purity following cartridge filtration and used subsequently in the synthesis of [N‐ethyl‐1,2‐³H]apadenoson, an adenosine A_2a receptor agonist. The overall yield for this transformation was 56% and the radiochemical purity of the final product was greater than 99%. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and Positive Inotropic Evaluation of 2‐(4‐(4‐Substituted benzyloxy)‐3‐methoxybenzyl)‐1,4‐diazepan‐1‐yl)‐N‐(4,5‐dihydro‐1‐methyl[1,2,4]triazolo[4,3‐a]quinolin‐7‐yl)‐acetamides

In an attempt to search for more potent positive inotropic agents, a series of 2‐(4‐(4‐substituted benzyloxy)‐3‐methoxybenzyl)‐1,4‐diazepan‐1‐yl)‐N‐(4,5‐dihydro‐1‐methyl[1,2,4]triazolo[4,3‐a]quinolin‐7‐yl)acetamides was synthesized and their positive inotropic activities were evaluated by measuring left atrium stroke volume on isolated rabbit‐heart preparations. Several compounds showed favorable activity compared with the standard drug Milrinone among which 2‐(4‐(4‐(2‐chlorobenzyloxy)‐3‐methoxybenzyl)‐1,4‐diazepan‐1‐yl)‐N‐(4,5‐dihydro‐1‐methyl‐[1,2,4]triazolo[4,3‐a]quinolin‐7‐yl)acetamide 6e was found to have the most desirable potency with the 6.79 ± 0.18% increased stroke volume (Milrinone: 1.67 ± 0.64%) at a concentration of 1×10^–5 M in our in‐vitro study. The chronotropic effects of those compounds having inotropic effects were also evaluated in this work.     

Synthesis of C‐14 and C‐13, H‐2‐labeled IKK inhibitor: [14C] and [13C4,D3]‐N‐(6‐chloro‐7‐methoxy‐9H‐pyrido[3,4‐b]indol‐8‐yl)‐2‐methyl‐3‐pyridinecarboxamide

[¹⁴C]‐N‐(6‐Chloro‐7‐methoxy‐9H‐pyrido [3,4‐b]indol‐8‐yl)‐2‐methyl‐3‐pyridinecarboxamide (5B ), an IKK inhibitor, was synthesized from [¹⁴C]‐barium carbonate in two steps in an overall radiochemical yield of 41%. The intermediate, [carboxyl‐¹⁴C]‐2‐methylnicotinic acid, was prepared by the lithiation and carbonation of 3‐bromo‐2‐methylpyridine. [¹³C₄,D₃]‐N‐(6‐chloro‐7‐methoxy‐9H‐pyrido [3,4‐b]indol‐8‐yl)‐2‐methyl‐3‐pyridinecarboxamide (5C ) was synthesized from [1,2,3,4‐¹³C₄]‐ethyl acetoacetate and [D₄]‐methanol in six steps in an overall yield of 2%. [¹³C₄]‐2‐methylnicotic acid, was prepared by condensation of [¹³C₄]‐ethyl 3‐aminocrotonate and acrolein, followed by hydrolysis with lithium hydroxide. Copyright © 2006 John Wiley & Sons, Ltd.     

Design and synthesis of 1,2,4‐triazolo[1,5‐a]pyrimidine derivatives as PDE 4B inhibitors endowed with bronchodilator activity

A series of 1,2,4‐triazolo[1,5‐a]pyrimidine derivatives was designed, synthesized, and screened for their phosphodiesterase (PDE 4B) inhibitory activity and bronchodilation ability. Compound 7e showed 41.80% PDE 4B inhibition at 10 µM. Eight compounds were screened for their bronchodilator activity, where compounds 7f and 7e elicited promising bronchodilator activity with EC₅₀ values of 18.6 and 57.1 µM, respectively, compared to theophylline (EC₅₀ = 425 µM). Molecular docking at the PDE 4B active site revealed a binding mode and docking scores comparable to those of a reference ligand, consistent with their PDE 4B inhibition activity.     

Synthesis and Positive Inotropic Evaluation of (E)‐2‐(4‐Cinnamylpiperazin‐1‐yl)‐N‐(1‐substituted‐4,5‐dihydro‐[1,2,4]triazolo[4,3‐a]quinolin‐7‐yl)acetamides

A series of (E)‐2‐(4‐cinnamylpiperazin‐1‐yl)‐N‐(1‐substituted‐4,5‐dihydro‐[1,2,4]triazolo[4,3‐a]quinolin‐7‐yl)acetamides were synthesized and evaluated for their positive inotropic activity by measuring the left atrium stroke volume on isolated rabbit heart preparations. This class of compounds presented favorable in vitro activity compared with the standard drug, milrinone, among which N‐(1‐(3‐chlorophenyl)‐4,5‐dihydro‐[1,2,4]triazolo[4,3‐a]quinolin‐7‐yl)‐2‐(4‐cinnamylpiperazin‐1‐yl)acetamide 5e was found to be the most potent with 16.58 ± 0.11% increased stroke volume (milrinone: 2.46 ± 0.07%) at a concentration of 3 × 10^?5 M. The chronotropic effects of the compounds having inotropic effects were also evaluated.     

Synthesis of 4‐thia[5‐13C]lysine

This report describes the synthesis of 4‐thia[5‐¹³C]lysine, an isotopomer of 4‐thialysine that is an analog of lysine. It was synthesized from 2‐amino[1‐¹³C]ethanol hydrochloride (1) in two steps. In the first step, 1 was converted to 2‐bromo[2‐¹³C]ethylamine hydrobromide (2). The reaction of cysteine with 2 in basic condition followed by acidification afforded 4‐thia[5‐¹³C]lysine hydrochloride (3).