Enolate-mediated 1,3-dipolar cycloaddition reaction of β-functionalized ketones with nitrile oxides: direct access to 3,4,5-trisubstituted isoxazoles

Enolate-mediated [3 + 2] organocatalytic 1,3-dipolar cycloaddition reactions of β-functionalized ketones with nitrile oxides have been developed. This strategy could generate 3,4,5-trisubstituted isoxazole in high yields and regioselectivities.

Enhancement of premature stop codon readthrough in the CFTR gene by Ataluren (PTC124) derivatives

Premature stop codons are the result of nonsense mutations occurring within the coding sequence of a gene. These mutations lead to the synthesis of a truncated protein and are responsible for several genetic diseases. A potential pharmacological approach to treat these diseases is to promote the translational readthrough of premature stop codons by small molecules aiming to restore the full-length protein. The compound PTC124 (Ataluren) was reported to promote the readthrough of the premature UGA stop codon, although its activity was questioned. The potential interaction of PTC124 with mutated mRNA was recently suggested by molecular dynamics (MD) studies highlighting the importance of H-bonding and stacking π-π interactions. To improve the readthrough activity we changed the fluorine number and position in the PTC124 fluoroaryl moiety. The readthrough ability of these PTC124 derivatives was tested in human cells harboring reporter plasmids with premature stop codons in H2BGFP and FLuc genes as well as in cystic fibrosis (CF) IB3.1 cells with a nonsense mutation. Maintaining low toxicity, three of these molecules showed higher efficacy than PTC124 in the readthrough of the UGA premature stop codon and in recovering the expression of the CFTR protein in IB3.1 cells from cystic fibrosis patient. Molecular dynamics simulations performed with mutated CFTR mRNA fragments and active or inactive derivatives are in agreement with the suggested interaction of PTC124 with mRNA.

Synthesis of Some Benzimidazole Derivatives Bearing 1,3,4-Oxadiazole Moiety as Anticancer Agents

In an effort to establish new benzimidazole related structural leads with improved anticancer activity, several new benzimidazole derivatives (5a-i) with 1,3,4-oxadiazole scaffold incorporated were synthesized and studied for their anticancer activity. The anticancer screening against MDA-MB-231 breast cancer cell lines showed that compound (5c) exhibited moderate cytotoxicity.

Bifunctional reactivity of amidoximes observed upon nucleophilic addition to metal-activated nitriles

Treatment of the aromatic nitrile complexes trans-[PtCl2(RC6H4CN)2] (R = p-CF3 NC1, H NC2, o-Cl NC3) with the aryl amidoximes p-R'C6H4C(NH2)=NOH (R' = Me AO1, H AO2, Br AO3, CF3 AO4, NO2 AO5) in all combinations, followed by addition of 1 equiv of AgOTf and then 5 equiv of Et3N, leads to the chelates [PtCl{HN=C(RC6H4)ON=C(C6H4R'-p)NC(RC6H4)═NH}] (1-15; 15 examples; yields 71-88% after column chromatography) derived from the platinum(II)-mediated coupling between metal-activated nitriles and amidoximes. The mechanism of this reaction was studied experimentally by trapping and identification of the reaction intermediates, and it was also investigated theoretically at the DFT level of theory. The combined experimental and theoretical results indicate that the coupling with the nitrile ligands involves both the HON and monodeprotonated NH2 groups of the amidoximes, whereas in the absence of the base, the NH2 functionality is inactive toward the coupling. The observed reaction represents the first example of bifunctional nucleophilic behavior of amidoximes. The complexes 1-16 were characterized by elemental analyses (C, H, N), high-resolution ESI(+)-MS, FTIR, and (1)H NMR techniques, whereas unstable 17 was characterized by HRESI(+)-MS and FTIR. In addition, 8·C4H8O2, 12, and 16·CHCl3 were studied by single-crystal X-ray diffraction.

Synthesis and evaluation of benzosuberone embedded with 1,3,4-oxadiazole, 1,3,4-thiadiazole and 1,2,4-triazole moieties as new potential anti proliferative agents

As an aspect of our ongoing research in search of new anti proliferative agents, a series of novel analogs of benzosuberone embedded with 1,3,4-oxadiazole, 1,3,4-thiadiazole and 1,2,4-triazole moieties were synthesized in excellent yields (82-93%). All the newly synthesized compounds were characterized by (1)H NMR, (13)C NMR, ESI/LC-MS, HRMS and evaluated for their in vitro anti proliferative activity against four human cancer cell lines (cervical, breast, pancreatic and alveolar). Among the synthesized compounds, 4b, 6a, 7d and 7l showed potent anti proliferative activity with GI50 values range of 0.079-0.957μM against four human cancer cell lines. However, it was revealed that the compound 7d have shown very close GI50 value 0.079μM as compared with positive control of colchicine against cervical cancer cell line.

Mechanistic insights into the ANRORC-like rearrangement between methylhydrazine and 1,2,4-oxadiazole derivatives

The first in-depth theoretical study devoted to elucidate the mechanism of the ANRORC reaction between 1,2,4-oxadiazole derivatives and methylhydrazine is described.

A facile approach to synthesize 3,5-disubstituted-1,2,4-oxadiazoles via copper-catalyzed-cascade annulation of amidines and methylarenes

A tandem Cu-catalyzed oxidation–amination–cyclization reaction for synthesizing various 3,5-disubstituted-1,2,4-oxadiazoles from easily available amidines and methylarenes or methylhetarenes is reported.

Efficient assembly of mono- and bis(1,2,4-oxadiazol-3-yl)furoxan scaffolds via tandem reactions of furoxanylamidoximes

Tandem protocols for the synthesis of new types of hybrid molecules – (1,2,4-oxadiazol-3-yl)furoxans based on the furoxanylamidoximes heterocyclization have been developed.

Diaminoglyoxime as a versatile reagent in the synthesis of bis(1,2,4-oxadiazoles), 1,2,4-oxadiazolyl-quinazolines and 1,2,4-oxadiazolyl-benzothiazinones

The synthesis of bis(1,2,4-oxadiazoles), 1,2,4-oxadiazolyl-quinazolines, and 1,2,4-oxadiazolyl-benzothiazinones has been investigated by the reaction of diaminoglyoxime with various ketones and methyl 2-aminobenzoate, 2-amino-5-chlorophenyl)(phenyl)methanone, and 2-mercapto benzoic acid in acetic acid either a catalyst or solvent at 100 °C.

Bis-aryloxadiazoles as effective activators of the aryl hydrocarbon receptor

Bis-aryloxadiazoles are common scaffolds in medicinal chemistry due to their wide range of biological activities. Previously, we identified a 1,2,4-bis-aryloxadiazole that blocks mammary branching morphogenesis through activation of the aryl hydrocarbon receptor (AHR). In addition to defects in mammary differentiation, AHR stimulation induces toxicity in many other tissues. We performed a structure activity relationship (SAR) study of 1,2,4-bis-aryloxadiazole to determine which moieties of the molecule are critical for AHR activation. We validated our results with a functional biological assay, using desmosome formation during mammary morphogenesis to indicate AHR activity. These findings will aid the design of oxadiazole derivative therapeutics with reduced off-target toxicity profiles.

Toward a rationale for the PTC124 (Ataluren) promoted readthrough of premature stop codons: a computational approach and GFP-reporter cell-based assay

The presence in the mRNA of premature stop codons (PTCs) results in protein truncation responsible for several inherited (genetic) diseases. A well-known example of these diseases is cystic fibrosis (CF), where approximately 10% (worldwide) of patients have nonsense mutations in the CF transmembrane regulator (CFTR) gene. PTC124 (3-(5-(2-fluorophenyl)-1,2,4-oxadiazol-3-yl)-benzoic acid), also known as Ataluren, is a small molecule that has been suggested to allow PTC readthrough even though its target has yet to be identified. In the lack of a general consensus about its mechanism of action, we experimentally tested the ability of PTC124 to promote the readthrough of premature termination codons by using a new reporter. The reporter vector was based on a plasmid harboring the H2B histone coding sequence fused in frame with the green fluorescent protein (GFP) cDNA, and a TGA stop codon was introduced in the H2B-GFP gene by site-directed mutagenesis. Additionally, an unprecedented computational study on the putative supramolecular interaction between PTC124 and an 11-codon (33-nucleotides) sequence corresponding to a CFTR mRNA fragment containing a central UGA nonsense mutation showed a specific interaction between PTC124 and the UGA codon. Altogether, the H2B-GFP-opal based assay and the molecular dynamics (MD) simulation support the hypothesis that PTC124 is able to promote the specific readthrough of internal TGA premature stop codons.

A metal-free tandem approach to prepare structurally diverse N-heterocycles: synthesis of 1,2,4-oxadiazoles and pyrimidinones

N-heterocycles, namely 1,2,4-oxadiazoles and 2,6 disubstituted pyrimidin-4-ones, have been synthesised in one pot via carboxamidation of amidines with aryl carboxylic acids and aryl propargylic acids under metal-free conditions.

Hsp60 chaperonopathies and chaperonotherapy: targets and agents

INTRODUCTION

Hsp60 (Cpn60) assembles into a tetradecamer that interacts with the co-chaperonin Hsp10 (Cpn10) to assist client polypeptides to fold, but it also has other roles, including participation in pathogenic mechanisms.

AREA COVERED

Hsp60 chaperonopathies are pathological conditions, inherited or acquired, in which the chaperone plays a determinant etiologic-pathogenic role. These diseases justify selection of Hsp60 as a target for developing agents that interfere with its pathogenic effects. We provide information on how to proceed.

EXPERT OPINION

The information available encourages the development of ways to improve Hsp60 activity (positive chaperonotherapy) when deficient or to block it (negative chaperonotherapy) when pathogenic. Many questions are still unanswered and obstacles are obvious. More information is needed to establish when and why autologous Hsp60 becomes a pathogenic autoantigen, or induces cytokine formation and inflammation, or favors carcinogenesis. Clarification of these points will take considerable time. However, analysis of the Hsp60 molecule and a search for active compounds aimed at structural sites that will affect its functioning should continue without interruption. No doubt that some of these compounds will offer therapeutic hopes and will also be instrumental for dissecting structure-function relationships at the biochemical and biological (using animal models and cultured cells) levels.

Oxadiazoles as privileged motifs for promising anticancer leads: recent advances and future prospects

Taking into account the rising trend of the incidence of cancers of various organs, effective therapies are urgently needed to control human malignancies. The rapid emergence of hundreds of new agents that modulate an ever-growing list of cancer-specific molecular targets offers tremendous hope for cancer patients. However, almost all of the chemotherapy drugs currently on the market cause serious side effects. Based on these facts, the design of new chemical entities as anticancer agents requires the simulation of a suitable bioactive pharmacophore. The pharmacophore not only should have the required potency but must also be safer on normal cell lines than on tumor cells. In this perspective, oxadiazole scaffolds with well-defined anticancer activity profile have fueled intense academic and industrial research in recent years. This paper is intended to highlight the recent advances along with current developments as well as future outlooks for the design of novel and efficacious anticancer agents based on oxadiazole motifs.