Ali Hachem

A new stereoselective synthesis of chiral tetrahydrothiopyrans and their corresponding sulfoxides

Abstract A new stereoselective synthesis of chiral tetrahydrothiopyrans has been achieved based upon the intramolecular trapping of pentadienyl cations complexed to Fe(CO) 3 by sulfur nucleophiles. Oxidation of these heterocycles with Oxone ® is compatible with the organometallic moiety and leads in good diastereoselectivity to the corresponding sulfoxides.

A general synthesis of arylindoles and (1-arylvinyl)carbazoles via a one-pot reaction from N-tosylhydrazones and 2-nitro-haloarenes and their potential application to colon cancer

A convergent and effective synthesis of 3-aryl-indoles, 2,3-diaryl indoles, and (1-arylvinyl)carbazoles from a one-pot sequence involving the coupling of N-tosylhydrazones with ortho-nitro-haloarenes followed by a cyclization has been developed. Compound 5i exhibits excellent antiproliferative activity in the low nM range against colon cancer cell lines.

Synthesis of novel aromatic analogues of 12-HETE

New mono- and diaromatic analogues of the arachidonic acid metabolite 12-HETE have been prepared using versatile strategies. The easily accessible monoacetal of isophtalaldehyde 3 was developed as a key intermediate for these syntheses.

Poly(vinylidene fluoride) Containing Phosphonic Acid as Anticorrosion Coating for Steel

Vinylidene fluoride (VDF)-based copolymers bearing pendant phosphonic acid function for potential application as anticorrosion coatings were synthesized via free radical copolymerization of VDF with a new phosphorus containing 2-trifluoromethacrylate monomer, (dimethoxyphosphoryl)methyl 2-(trifluoromethyl)acrylate (MAF-DMP). MAF-DMP was prepared from 2-trifluoromethacrylic acid in 60% overall yield. Radical copolymerizations of VDF with MAF-DMP initiated by tert-amyl peroxy-2-ethylhexanoate at varying ([VDF]0/[MAF-DMP]0) feed ratios led to several poly(VDF-co-MAF-DMP) copolymers having different molar percentages of VDF (79-96%) and number-average molecular weights (Mns) up to ca. 10 000 g mol-1 in fair yields (47-53%). Determination of the composition and microstructure of all the synthesized copolymers was done by 1H and 19F NMR spectroscopies. The monomer reactivity ratios of this new VDF/MAF-DMP pair were also determined (rVDF = 0.76 ± 0.34 and rMAF-DMP = 0 at 74 °C). The resulting poly(VDF-co-MAF-DMP) copolymers exhibited high melting temperature (162-171 °C, with respect to the VDF content), and the degree of crystallinity reached up to 51%. Finally, the pendant dimethyl phosphonate ester groups of the synthesized poly(VDF-co-MAF-DMP) copolymer were quantitatively hydrolyzed, giving rise to novel phosphonic acid-functionalized PVDF (PVDF-PA). In comparison to hydrophobic poly(VDF-co-MAF-DMP) copolymers (the water contact angle, WCA, was 98°), the hydrophilic character of the PVDF-PA was found to be surprisingly rather pronounced, exhibiting low WCA (15°). Finally, steel plates coated with PVDF-PA displayed satisfactory anticorrosion properties under simulated seawater environment.

Biological and anti-inflammatory evaluation of two thiazole compounds in RAW cell line: potential cyclooxygenase-2 specific inhibitors.

The anti-inflammatory effect of two new thiazoles derivatives CX-32 (N-[4-(4-hydroxy-3-methoxyphenyl)-1,3-thiazol-2-yl]acetamide) and CX-35 (4-(2-amino-1,3-thiazol-4-yl)-2-methoxyphenol), was investigated in LPS-stimulated RAW 264.7 cell line. Synthesis, structure analysis and purity of these compounds were evaluated by high performance liquid chromatography, H1 NMR, and C13 NMR. Assessment of CX-32 and CX-35 inhibitory effect on cyclooxygenase-2 (COX-2) activity was achieved by incubating LPS-activated RAW cells with 25 μM, 50 μM or 100 μM of CX-32 or CX-35 respectively. Levels of secreted PGE2 were evaluated by enzyme immunoassay (EIA) and levels of COX-2 protein were measured by western blot. Finally, cell viability experiments were undertaken to assess the toxicity of each compound. Treatment of LPS-activated RAW cells with 25 μM, 50 μM, or 100 μM of CX-35 or CX-32 respectively, prevented the production of prostaglandins, but was without effect on COX-2 protein levels. Moreover, CX-35 and CX-32 reduced PGE2 production to levels comparable to those obtained in LPS-activated RAW cells incubated with the selective COX-2 inhibitor NS 398. Furthermore, both CX-32 and CX-35 showed no toxic effects, since viability of non-treated Hela cells was similar to Hela cells incubated with either CX-35 or CX-32. Our data demonstrated that CX-32 and CX-35 significantly blocked prostaglandin production induced during inflammatory cellular stress, possibly acting through specific COX-2 inhibition; confirmation of this hypothesis requires further investigation.

Thiazole derivatives as inhibitors of cyclooxygenases in vitro and in vivo

Cyclooxygenases (COXs) are important membrane-bound heme containing enzymes important in platelet activation and inflammation. COX-1 is constitutively expressed in most cells whereas COX-2 is an inducible isoform highly expressed in inflammatory conditions. Studies have been carried out to evaluate thiazole derivatives as anti-inflammatory molecules. In this study, we investigated the in vitro and in vivo effects of two novel thiazole derivatives compound 1 (N-[4-(4-hydroxy-3-methoxyphenyl)-1,3-thiazol-2-yl] acetamide) and compound 2 (4-(2-amino-1,3-thiazol-4-yl)-2-methoxyphenol) on prostaglandin E2 (PGE2) production and COX activity in inflammatory settings. Our results reveal a potent inhibition of both compound 1 (IC50 9.01±0.01µM) and 2 (IC50 11.65±6.20µM) (Mean±S.E.M.) on COX-2-dependent PGE2 production. We also determined whether COX-1 activity was inhibited. Using cells stably over-expressing COX-1 and human blood platelets, we showed that compound 1 is a specific inhibitor of COX-1 with IC50 (5.56×10(-8)±2.26×10(-8)µM), whereas compound 2 did not affect COX-1. Both compounds exhibit anti-inflammatory effect in the dorsal air pouch model of inflammation as shows by inhibition of PGE2 secretion. Modeling analysis of docking in the catalytic site of COX-1 or COX-2 further confirmed the difference in the effect of these two compounds. In conclusion, this study contributes to the design of new anti-inflammatory agents and to the understanding of cyclooxygenase inhibition by thiazole.

Csp2–Csp2 and Csp2–N Bond Formation in a One-Pot Reaction between N-Tosylhydrazones and Bromonitrobenzenes: An Unexpected Cyclization to Substituted Indole Derivatives

A novel, sequential, palladium-catalyzed, cross-coupling reaction using N-tosylhydrazone and bromonitrobenzene derivatives followed by reductive cyclization has been developed. This transformation providing an efficient route to unexpected N-arylindole derivatives involves, in a one-pot reaction, the formation of one Csp2-Csp2 bond and two Csp2-N bonds together with the cleavage of one Csp2-heteroatom bond. Evaluation of the biological activity led to the identification of compound 5a, which displays potent activity at nanomolar concentrations against human colon carcinoma cell line.

Conformational Effects through Hydrogen Bonding in a Constrained γ-Peptide Template: From Intraresidue Seven-Membered Rings to a Gel-Forming Sheet Structure

A series of three short oligomers (di-, tri-, and tetramers) of cis-2-(aminomethyl)cyclobutane carboxylic acid, a γ-amino acid featuring a cyclobutane ring constraint, were prepared, and their conformational behavior was examined spectroscopically and by molecular modeling. In dilute solutions, these peptides showed a number of low-energy conformers, including ribbonlike structures pleated around a rarely observed series of intramolecular seven-membered hydrogen bonds. In more concentrated solutions, these interactions defer to an organized supramolecular assembly, leading to thermoreversible organogel formation notably for the tripeptide, which produced fibrillar xerogels. In the solid state, the dipeptide adopted a fully extended conformation featuring a one-dimensional network of intermolecularly H-bonded molecules stacked in an antiparallel sheet alignment. This work provides unique insight into the interplay between inter- and intramolecular H-bonded conformer topologies for the same peptide template.

Synthesis of enones, pyrazolines and pyrrolines with gem-difluoroalkyl side chains

Summary Starting from easily accessible gem-difluoropropargylic derivatives, a DBU-mediated isomerisation affords enones in fair yields with a gem-difluoroalkyl chain. These derivatives were used to prepare pyrazolines and pyrrolines with the desired gem-difluoroalkyl side chain by cyclocondensations in good yields and with excellent stereoselectivity. A one-pot process was also successfully developed for these sequential reactions. By carrying out various types of Pd-catalyzed coupling reactions for compounds with a p-bromophenyl substituent a route to focused chemical libraries was demonstrated.

Synthesis and antiaggregant properties of Stabilized analogues of polyunsaturated fatty acid metabolites

New aromatic and heteroaromatic analogues of polyunsaturated fatty acid metabolites have been prepared using short and versatile strategies. Preliminary studies of their activity as inhibitors of platelet aggregation are reported.