Synthesis, biological evaluation and molecular modeling studies of imidazo[1,2-a]pyridines derivatives as protein kinase inhibitors.

We report here the synthesis, the biological evaluation and the molecular modeling studies of new imidazo[1,2-a]pyridines derivatives designed as potent kinase inhibitors. This collection was obtained from 2-aminopyridines and 2-bromoacetophenone which afforded final compound in only one step. The bioactivity of this family of new compounds was tested using protein kinase and ATP competition assays. The structure-activity relationship (SAR) revealed that six compounds inhibit DYRK1A and CLK1 at a micromolar range. Docking studies provided possible explanations that correlate with the SAR data. The most active compound 4c inhibits CLK1 (IC50 of 0.7 µM) and DYRK1A (IC50 of 2.6 µM).

Rapid synthesis of 4-arylchromenes from ortho-substituted alkynols: A versatile access to restricted isocombretastatin A-4 analogues as antitumor agents.

Potent anticancer 4-arylchromene agents 6, as restricted isoCA-4 analogues, were prepared with excellent yields by a rapid and versatile synthetic pathway. First, in the presence of PTSA in EtOH, a variety of arylalkynols 9 were transformed into substituted 4-chromanones 10 in a one pot procedure which include regioselective arylalkynols hydration, alcohol etherification, MOM-cleavage, and cyclization. Further palladium coupling reactions, using aryl halides and N-tosylhydrazones 11 gave access to a small library of functionalized 4-arylchromenes 6 with good yields. From this series of 4-arylchromenes, we have identified compound 6s which inhibit tubulin assembly at a micromolar level and demonstrate a remarkable nanomolar level of cytotoxicity against four human cancer cell lines. Docking studies showed that isoCA-4 and its restricted chromene analogue 6s adopt a similar positioning in the colchicine binding-site of tubulin.

Overlapping binding sites drive allosteric agonism and positive cooperativity in type 4 metabotropic glutamate receptors.

Type 4 metabotropic glutamate (mGlu4) receptors are emerging targets for the treatment of various disorders. Accordingly, numerous mGlu4-positive allosteric modulators (PAMs) have been identified, some of which also display agonist activity. To identify the structural bases for their allosteric action, we explored the relationship between the binding pockets of mGlu4 PAMs with different chemical scaffolds and their functional properties. By use of innovative mGlu4 biosensors and second-messenger assays, we show that all PAMs enhance agonist action on the receptor through different degrees of allosteric agonism and positive cooperativity. For example, whereas VU0155041 and VU0415374 display equivalent efficacies [log(τ(B)) = 1.15 ± 0.38 and 1.25 ± 0.44, respectively], they increase the ability of L-AP4 to stabilize the active conformation of the receptor by 4 and 39 times, respectively. Modeling and docking studies identify 2 overlapping binding pockets as follows: a first site homologous to the pocket of natural agonists of class A GPCRs linked to allosteric agonism and a second one pointing toward a site topographically homologous to the Na(+) binding pocket of class A GPCRs, occupied by PAMs exhibiting the strongest cooperativity. These results reveal that intrinsic efficacy and cooperativity of mGlu4 PAMs are correlated with their binding mode, and vice versa, integrating structural and functional knowledge from different GPCR classes.

α- and ß-hydrazino acid-based pseudopeptides inhibit the chymotrypsin-like activity of the eukaryotic 20S proteasome.

We describe the synthesis of a library of new pseudopeptides and their inhibitory activity of the rabbit 20S proteasome chymotrypsin-like (ChT-L) activity. We replaced a natural α-amino acid by an α- or a ß-hydrazino acid and obtained inhibitors of proteasome up to a submicromolar range (0.7 µM for molecule 24b). Structural variations influenced the inhibition of the ChT-L activity. Models of inhibitor/20S proteasome complexes corroborated the inhibition efficacies obtained by kinetic studies.

Design, synthesis and anticancer properties of 5-arylbenzoxepins as conformationally restricted isocombretastatin A-4 analogs.

A series of novel benzoxepins 6 was designed and prepared as rigid-isoCA-4 analogs according to a convergent strategy using the coupling of N-tosylhydrazones with aryl iodides under palladium catalysis. The most potent compound 6b, having the greatest resemblance to CA-4 and isoCA-4 displayed antiproliferative activity at nanomolar concentrations against various cancer cell lines and inhibited tubulin assembly at a micromolar range. In addition, benzoxepin 6b led to the arrest of HCT116, K562, H1299 and MDA-MB231 cancer cell lines in the G2/M phase of the cell cycle, and strongly induced apoptosis at low concentrations. Docking studies demonstrated that benzoxepin 6b adopt an orientation similar to that of isoCA-4 at the colchicine binding site on ß-tubulin.

Carbonylhydrazide-based molecular tongs inhibit wild-type and mutated HIV-1 protease dimerization.

We have designed and synthesized new molecular tongs based on a rigid naphthalene scaffold and evaluated their antidimer activity on HIV-1 protease (PR). We inserted carbonylhydrazide and oligohydrazide (azatide) fragments into their peptidomimetic arms to reduce hydrophobicity and increase metabolic stability. These fragments are designed to disrupt the protein-protein interactions by reproducing the hydrogen bond pattern found in the antiparallel ß-sheet formed between the N- and C-ends of the two monomers in the native PR. Kinetic analyses and fluorescent probe binding studies showed that several molecular tongs can inhibit PR dimerization. The best nonpeptidic molecular tongs to date were obtained with an inhibition constant K(id) of 50 nM for PR and 80 nM for the multimutated protease ANAM-11. The PR inhibition was selective, the aspartic proteases renin and pepsin were not inhibited.

Conformationnally restricted naphthalene derivatives type isocombretastatin A-4 and isoerianin analogues: synthesis, cytotoxicity and antitubulin activity.

A novel series of dihydronaphtalene, tetrahydronaphtalene and naphtalene derivatives as restricted analogues of isoCA-4 were designed, synthesized and evaluated for their anticancer properties. High cell growth inhibition against four tumour cell lines was observed at a nanomolar level with dihydronaphtalenes 1d, e and 1h, tetrahydronaphtalene 2c and naphtalene 3c. Structure-activity relationships are also considered. These compounds exhibited a significant inhibitory activity toward tubulin polymerization (IC(50) = 2-3 µM), comparable to that of isoCA-4. The effect of the lead compounds 1e and 2c on the cancer cells tested was associated with cell cycle arrest in the G(2)/M phase. Docking studies reveal that these compounds showed a binding mode similar to those observed with their non-constraint isoCA-4 and isoerianin congeners.

Antiproliferative activity of trans-avicennol from Zanthoxylum chiloperone var. angustifolium against human cancer stem cells.

Zanthoxylum chiloperone var. angustifolium root bark was studied with the aim of finding novel molecules able to overcome cancer stem cell chemoresistance. Purification of a methanol-soluble extract resulted in the isolation of a known pyranocoumarin, trans-avicennol (1). Compound 1 demonstrated antiproliferative activity on glioma-initiating cells, whereas it was inactive on human neural stem cells. trans-Avicennol (1) activated the MAPK/ERK pathway and was also evaluated for its ability to inhibit the enzyme indoleamine-2,3-dioxygenase.

B-ring-modified isocombretastatin A-4 analogues endowed with interesting anticancer activities.

A novel class of isocombretastatin A-4 (isoCA-4) analogues with modifications at the 3'-position of the B-ring by replacement with C-linked substituents was studied. Exploration of the structure-activity relationships of theses analogues led to the identification of several compounds that exhibit excellent antiproliferative activities in the nanomolar concentration range against H1299, MDA-MB231, HCT116, and K562 cancer cell lines; they also inhibit tubulin polymerization with potency similar to that of isoCA-4. 1,1-Diarylethylenes 8 and 17, respectively with (E)-propen-3-ol and propyn-3-ol substituents at the 3'-position of the B-ring, proved to be the most active in this series. Both compounds led to the arrest of various cancer cell lines at the G(2) /M phase of the cell cycle and strongly induced apoptosis. Docking of compounds 8 and 17 in the colchicine binding site indicated that their C3' substituents guide the positioning of the B-ring in a manner different from that observed for isoCA-4.

Hexylacrylate-based mixed-mode monolith, a stationary phase for the nano-HPLC separation of structurally related enkephalins.

The potential of an in situ photopolymerized hexylacrylate-based monolithic stationary phase-bearing sulfonic acid groups was investigated by studying the chromatographic retention of small structurally related peptides (enkephalins) by nano-LC. Several retention mechanisms were highlighted. First, a reverse-phase chromatographic behavior toward neutral solutes due to hexylacrylate-moieties was demonstrated. Second, an evaluation of the influences of buffer pH suggested the involvement of a cation-exchange mechanism due to the presence of 2-acrylamido-2-methyl-1-propanesulfonic acid. This cation-exchange phenomenon was confirmed by the clear influence of Na(+) concentration in the mobile phase on peptide retention.