Yeong Keng Yoon

Substituted spiro [2.3'] oxindolespiro [3.2″]-5,6-dimethoxy-indane-1″-one-pyrrolidine analogue as inhibitors of acetylcholinesterase.

Series of pyrolidine analogues were synthesized and examined as acetylcholinesterase (AChE) inhibitors. Among the compounds, compounds 4k and 6k were the most potent inhibitors of the series. Compound 4k, showed potent inhibitory activity against acetyl cholinesterase enzyme with IC(50) 0.10 μmol/L. Pyrolidine analogues might be potential acetyl cholinesterase agents for AD.

Synthesis, characterization, and molecular docking analysis of novel benzimidazole derivatives as cholinesterase inhibitors

Two series of novel acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors containing benzimidazole core structure were synthesized by a four-step reaction pathway starting from 4-fluoro-3-nitrobenzoic acid as the basic compound. The structure of the novel benzimidazoles was characterized and confirmed by the elemental and mass spectral analyses as well as (1)H NMR spectroscopic data. Of the 34 novel synthesized compounds, three benzimidazoles revealed AChE inhibition with IC50<10 μM. The highest inhibitory activity (IC50=5.12 μM for AChE and IC50=8.63 μM for BChE) corresponds to the compound 5IIc (ethyl 1-(3-(1H-imidazol-1-yl)propyl)-2-(4-nitrophenyl)-1H-benzo[d]imidazole-5-carboxylate). The relationship between lipophilicity and the chemical structures as well as their limited structure-activity relationship was discussed.

Synthesis and evaluation of novel benzimidazole derivatives as sirtuin inhibitors with antitumor activities.

A total of 15 novel benzimidazole derivatives were designed, synthesized and evaluated for their SIRT1 and SIRT2 inhibitory activity. All compounds showed better inhibition on SIRT2 as compared to SIRT1. Among these, compound 5j displayed the best inhibitory activity for SIRT1 (IC50=58.43μM) as well as for SIRT2 (IC50=45.12μM). Cell cytotoxicity assays also showed that compound 5j possesses good antitumor activity against two different cancer cell lines derived from breast cancer (MCF-7 and MDA-MB-468). A simple structure-activity-relationship (SAR) study of the newly synthesized benzimidazole derivatives was also discussed.

Synthesis and evaluation of antimycobacterial activity of new benzimidazole aminoesters

A total of 51 novel benzimidazoles were synthesized by a 4-step reaction starting from basic compound 4-fluoro-3-nitrobenzoic acid under relatively mild reaction conditions. The structure of the novel benzimidazoles was confirmed by mass spectra as well as (1)H NMR spectroscopic data. Out of the 51 novel synthesized compounds, 42 of them were screened for their antimycobacterial activity against Mycobacterium tuberculosis H37Rv strain using BacTiter-Glo™ Microbial Cell Viability (BTG) method. Results of activity screened using Alamar Blue method was also provided for comparison purposes. Two of the novel benzimidazoles synthesized showed moderately good activity with IC50 of less than 15 μM. Compound 5g, ethyl 2-(4-(trifluoromethyl)phenyl)-1-(2-morpholinoethyl)-1H-benzo[d]imidazole-5-carboxylate, was found to be the most active with IC50 of 11.52 μM.

Structural Modifications of Benzimidazoles via Multi-Step Synthesis and Their Impact on Sirtuin-Inhibitory Activity

Benzimidazole derivatives have been shown to possess sirtuin‐inhibitory activity. In the continuous search for potent sirtuin inhibitors, systematic changes on the terminal benzene ring were performed on previously identified benzimidazole‐based sirtuin inhibitors, to further investigate their structure–activity relationships. It was demonstrated that the sirtuin activities of these novel compounds followed the trend where meta‐substituted compounds possessed markedly weaker potency than ortho‐ and para‐substituted compounds, with the exception of halogenated substituents. Molecular docking studies were carried out to rationalize these observations. Apart from this, the methods used to synthesize the interesting compounds are also discussed.

Synthesis and discovery of novel hexacyclic cage compounds as inhibitors of acetylcholinesterase.

Hexacyclic derivatives share vital pharmacological properties, considered useful in Alzheimers disease. The aim of this study was synthesis and its evaluation for acetyl cholinesterase inhibitory activity of novel hexacyclic analogues. Compound 4f, showed potent inhibitory activity against acetyl cholinesterase enzyme with IC(50) 0.72 μmol/L.

Antituberculosis: Synthesis and Antimycobacterial Activity of Novel Benzimidazole Derivatives

A total of seven novel benzimidazoles were synthesized by a 4-step reaction starting from 4-fluoro-3-nitrobenzoic acid under relatively mild reaction conditions. The synthesized compounds were screened for their antimycobacterial activity against M. tuberculosis H37Rv (MTB-H37Rv) and INH-resistant M. tuberculosis (INHR-MTB) strains using agar dilution method. Three of them displayed good activity with MIC of less than 0.2 μM. Compound ethyl 1-(2-(4-(4-(ethoxycarbonyl)-2-aminophenyl)piperazin-1-yl)ethyl)-2-(4-(5-(4-fluorophenyl)pyridin-3-ylphenyl-1H-benzo[d]imidazole-5-carboxylate (5g) was found to be the most active with MIC of 0.112 μM against MTB-H37Rv and 6.12 μM against INHR-MTB, respectively.

Ethyl 1-[3-(1H-imidazol-1-yl)prop­yl]-2-(4-chloro­phen­yl)-1H-benzo[d]imidazole-5-carboxyl­ate dihydrate

In the title compound, C22H21ClN4O2·2H2O, the almost-planar benzimidazole ring system [maximum deviation 0.014 (1) Å] is inclined at angles of 36.32 (5) and 74.75 (7)° with respect to the phenyl and imidazole rings, respectively. In the crystal structure, the water molecules are linked to the organic molecules to form a three-dimensional network via O—H⋯N and O—H⋯O hydrogen bonds. The packing is further consolidated by a pair of bifurcated C—H⋯O bonds, generating R 1 2(6) loops. C—H⋯π interactions are also observed.

Sirtuin Inhibitors: An Overview from Medicinal Chemistry Perspective.

The role of sirtuins in age-related diseases is an area of rapidly expanding investigation. Sirtuins are NAD+ -dependent class III histone deacetylases (HDACs) that share extensive homologies with the yeast HDAC Sir2. Class I and class II HDACs inhibitors have been identified as potential anticancer agents and are in clinical studies, but much less is known about class III HDAC inhibitors. However, inhibitors of sirtuins are currently being targeted as potential therapeutic agents for disease such as cancer, neurodegenerative disease and other disorders as sirtuins are discovered to regulate numerous downstream enzymes. Given the link between sirtuins and cancer, understanding the functionality of these enzymes may ultimately have significant impact in cancer prevention or cancer treatment. This review gives an updated overview regarding the regulation of sirtuin enzymes, their implications in cancer, various sirtuin inhibitor scaffolds and their insights in drug design.

Discovery of a potent and highly fluorescent sirtuin inhibitor

In search for potent sirtuin inhibitors, a series of diversified 1,2-disubstituted benzimidazole analogues were synthesized using a one-pot method. The most potent compound in the series (BZD9L1) was discovered to show high autofluorescence which can be utilized to predict its localization in cells. More importantly, BZD9L1 displayed strong antiproliferative effects against a panel of cancer cells tested. Molecular docking studies also help to explain the observed structure–activity relationship.