Design, synthesis, and testing of an 6-O-linked series of benzimidazole based inhibitors of CDK5/p25

Alzheimer’s disease (AD) is a progressive neurodegenerative disease resulting in cognitive and behavioral impairment. The two classic pathological hallmarks of AD include extraneuronal deposition of amyloid ?? (A??) and intraneuronal formation of neurofibrillary tangles (NFTs). NFTs contain hyperphosphorylated tau. Tau is the major microtubule-associated protein in neurons and stabilizes microtubules (MTs). Cyclin dependent kinase 5 (CDK5), when activated by the regulatory binding protein p25, phosphorylates tau at a number of proline-directed serine/threonine residues, resulting in formation of phosphorylated tau as paired helical filaments (PHFs) then in subsequent deposition of PHFs as NFTs. Beginning with the structure of Roscovitine, a moderately selective CDK5 inhibitor, we sought to conduct structural modifications to increase inhibitory potency of CDK5 and increase selectivity over a similar enzyme, cyclin dependent kinase 2 (CDK2). The design, synthesis, and testing of a series of 1-isopropyl-4-aminobenzyl-6-ether-linked benzimidazoles is presented.     

Characterisation of the beta-tubulin gene of Cylicocyclus nassatus

mRNA and genomic DNA were isolated from adult Cylicocyclus nassatus, and the mRNA was reverse transcribed. The cDNA was PCR amplified using degenerate primers designed according to the alignment of the β-tubulin amino acid sequences of other species. To complete the coding sequence, the 3′ end was amplified with the 3′-RACE, and for amplification of the 5′ end the SL1-primer was used. The cDNA of the β-tubulin gene of C. nassatus spans 1429 bp and encodes a protein of 448 amino acids. Specific primers were developed from the cDNA sequence to amplify the genomic DNA sequence and to analyse the genomic organisation of the β-tubulin gene. The complete sequence of the genomic DNA of the β-tubulin gene of C. nassatus has a size of 2652 bp and is organised into nine exons and eight introns. The identities with the exons of the gru-1 β-tubulin gene of Haemonchus contortus range between 79% and 97%.     

Oxidative dealkylation of a hindered phenol catalyzed by copper (II) bis benzimidazole diamide complex

The oxidative dealkylation of 2,4,6-tri-tert-butylphenol (TTBP) has been investigated using molecular oxygen and [Cu(NO₃(GBHA)](NO₃) as catalyst, where GBHA is N,N′-bis((benzimidazol-2-yl)methyl)hexanediamide [(a) M. Gupta, P. Mathur, R.J. Butcher, Inorg. Chem. 40 (2001) 878; (b) M. Gupta, S.K. Das, P. Mathur, A.W. Cordes, Inorg. Chim. Acta 353 (2003) 197; (c) S. Tehlan, M.S. Hundal, P. Mathur, Inorg. Chem. 43 (2004) 6589; (d) F. Afreen, P. Mathur, A. Rheingold, Inorg. Chim. Acta 358 (2005) 1125.]. X-ray structural characterization of complex [Cu(NO₃)(GBHA)](NO₃) · CH₃OH confirms that the Cu (II) ion is in a distorted square pyramidal geometry (τ = 0.168). The TTBP oxidation reaction proceeds via tri-tert-butylphenoxyl radical producing two products 2,6-di-tert-butyl-1,4-benzoquinone (A) and 4,6-di-tert-butyl-1,2-benzoquinone (B). Both A and B have been well characterized by ¹H NMR, ¹³C NMR, UV-Vis and mass data.     

Design,molecular docking and synthesis of novel 5,6-dichloro-2-methyl-1H-benzimidazole derivatives as potential urease enzyme inhibitors

A novel series of 5,6-dichloro-2-methyl-1H-benzimidazole derivatives was synthesized and then screened for their urease inhibitory activity. All compounds showed more potent inhibitory activity in the range of IC₅₀ = 0.0294 ± 0.0015–0.1494 ± 0.0041 µM than thiourea (IC₅₀ = 0.5117 ± 0.0159 µM), as a reference inhibitor. Among all the tested compounds, the compound 15 (IC₅₀ = 0.0294 ± 0.0015 µM) having strong electron-withdrawing nitro group on the phenyl ring was recorded as the most potent inhibitor of urease. All compounds were docked at the active sites of the Jack bean urease enzyme to investigate the reason of the inhibitory activity and the possible binding interactions of enzyme-ligand complexes.     

Design and synthesis of 2-substituted benzoxazoles as novel PTP1B inhibitors

A series of benzoxazole compounds containing oxamic acid were synthesized and screened for the PTP1B inhibition. Compound 31d showed best biochemical potency (K_i) of 6.7 μM. Structure–activity relationship were explained with the help of molecular modeling approach.     

Benzimidazole-based antibacterial agents against Francisella tularensis

Francisella tularensis is a highly virulent pathogenic bacterium. In order to identify novel potential antibacterial agents against F. tularensis, libraries of trisubstituted benzimidazoles were screened against F. tularensis LVS strain. In a preliminary screening assay, remarkably, 23 of 2,5,6- and 2,5,7-trisubstituted benzimidazoles showed excellent activity exhibiting greater than 90% growth inhibition at 1 μg/mL. Among those hits, 21 compounds showed MIC₉₀ values in the range of 0.35–48.6 μg/mL after accurate MIC determination. In ex vivo efficacy assays, four of these compounds exhibited 2–3 log reduction in colony forming units (CFU) per mL at concentrations of 10 and 50 μg/mL.     

Inhibitory effects of benzimidazole containing new phenolic Mannich bases on human carbonic anhydrase isoforms hCA I and II

New phenolic mono and bis Mannich bases incorporating benzimidazole, such as 2-(aminomethyl)-4-(1H-benzimidazol-2-yl)phenol and 2,6-bis(aminomethyl)-4-(1H-benzimidazol-2-yl)phenol were synthesized starting from 4-(1H-benzimidazol-2-yl)phenol. Amines used for the synthesis included dimethylamine, pyrrolidine, piperidine, N-methylpiperazine and morpholine. The CA inhibitory properties of these compounds were tested on the human carbonic anhydrase (CA, EC 4.2.1.1) isoforms hCA I and hCA II. These new compounds, as many phenols show moderate CA inhibitory properties.     

Diversity of benzimidazole-resistance alleles in populations of small ruminant parasites

The resistance of gastro-intestinal nematodes of small ruminants (sheep and goat) to benzimidazole anthelmintic drugs seems to be linked primarily to a single mutation in the isotype 1 beta-tubulin gene. This study was carried out to investigate the origin and diversity of benzimidazole-resistance alleles in trichostrongylid nematodes. We sequenced a 550 bp fragment of the isotype 1 beta-tubulin gene from several benzimidazole-resistant Teladorsagia circumcincta populations isolated from dairy goat farms in the central and south-western France. We also sequenced the same beta-tubulin fragment from Trichostrongylus colubriformis and Haemonchus contortus populations in south-western France. We found eight benzimidazole-resistance alleles in all T. circumcincta populations studied, six in H. contortus populations, and only one in T. colubriformis populations. In most cases, only one benzimidazole-resistance allele was present in T. circumcincta and H. contortus populations, but two alleles were found in a fewer number of them. Some T. circumcincta populations shared the same benzimidazole-resistance allele whereas some others had a specific benzimidazole-resistance allele. Similar findings were obtained for H. contortus. As no parasites are introduced once the flock of dairy goat farms has been constituted, these data indicate for the three studied species that rare pre-existing benzimidazole-resistance alleles already present before the isolation of populations had been selected. On the other hand, the fact that some benzimidazole-resistance alleles were specific to one population of T. circumcincta or H. contortus, seems to be in agreement with the hypothesis of the selection of spontaneous mutations. Thus, the origin of benzimidazole-resistance alleles in trichostrongylid nematodes seems to involve primarily the selection of rare alleles and possibly of spontaneous mutations.     

Optimisation of a novel series of selective CNS penetrant CB(2) agonists

A series of benzimidazole CB₂ receptor agonists were prepared and their properties investigated. Optimisation of the three benzimidazole substituents led to the identification of compound 23, a potent CB₂ full agonist (EC₅₀ 2.7 nM) with excellent selectivity over the CB₁ receptor (>3000-fold). Compound 23 demonstrated good CNS penetration in rat. Further optimisation led to the identification of compound 34 with improved selectivity over hERG and excellent CNS penetration in rat.     

Synthesis and evaluation of 2-phenyl-1,4-butanediamine-based CCR5 antagonists for the treatment of HIV-1

We describe the synthesis and potency of a novel series of N-substituted 2-phenyl- and 2-methyl-2-phenyl-1,4-diaminobutane- based CCR5 antagonists. Compounds 7a and 12f were found to be potent in anti-HIV assays and bioavailable in the low-dose rat PK model.