Iron(III)-Catalyzed Synthesis of 2-Alkyl Homoallyl Sulfonyl Amides: Antiproliferative Study and Reactivity Scope of Aza-Prins Cyclization.

A direct, catalytic, and complementary method to obtain 2-substituted homoallyl sulfonyl amides is described, starting from sulfonyl amides, aldehydes, and allyltrimethylsilane using iron(III) chloride as a sustainable catalyst. The scope of the process and the reactivity in aza-Prins cyclization is evaluated and supported by density functional theory (DFT) studies. Finally, an evaluation of the antiproliferative activity for this family of sulfonyl amides is also included.

Antitrichomonal activity and docking analysis of thiazole derivatives as TvMP50 protease inhibitors.

Trichomoniasis, caused by the protozoan Trichomonas vaginalis, is the most prevalent non-viral sexually transmitted infection that affects over 170 million people worldwide. The only type of drug recommended for the therapeutic control of trichomoniasis is the 5-nitroimidazoles, although there have been reports of some undesirable side effects and clinical resistance. Hence, the need for the search for new tricomonicidal agents is necessary. In a previous work, we demonstrated that two 2-amino-4-aryl thiazole derivatives (ATZ-1 and ATZ-2) possess a portent antigiardial effect. In the current paper, we investigated the in vitro antitrichomonal activity of these thiazole compounds. Both ATZ-1 and ATZ-2 reduced the viability and growth of parasites in a dose-dependent manner, with an IC50 value of 0.15 µg/mL and 0.18 µg/mL, respectively. Furthermore, both thiazole compounds were able to decrease the proteolytic activity in T. vaginalis trophozoites compared with untreated parasites. Interestingly, a full proteolytic inhibition profile was observed in the 50-kDa region which was associated with the decreased expression of the gene that codes for the trichomonad protease TvMP50. The docking simulations predicted strong interactions of the thiazole compounds in the TvMP50 protease's active site, suggesting a possible role as protease inhibitors. Our results demonstrate the potential of 2-amino-4-aryl thiazole derivatives as trichomonicidal compounds and could be, mechanistically, involved in the inhibition of key trichomonad proteases.

Anti-inflammatory effects of Chrysophyllum cainito fruit extract in lipopolysaccharide-stimulated mouse peritoneal macrophages.

The present paper sought to investigate the in vitro and in vivo anti-inflammatory effects of the methanolic extract (ME), hexane-ethyl acetate fraction E (FE) found in Chrysophyllum cainito fruits (CCF), as well the lupeol acetate (LA) obtained from FE on lipopolysaccharide (LPS)-stimulated mouse peritoneal macrophages. The macrophages were treated with ME, FE or LA at various concentrations and the viability of cells was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide method. Production of pro-inflammatory (IL-1ß, IL-6, and TNF-α) and anti-inflammatory (IL-10) cytokines, as well as the nitric oxide (NO) and hydrogen peroxide (H2O2) levels was determined using macrophages treated with ME, FE or LA at various concentrations and stimulated with LPS as an in vitro model. Afterwards, we evaluated the anti-inflammatory effects in vivo using the TPA-induced ear edema and carrageenan-induced paw edema tests in mice and production of inflammatory mediators was estimated in serum samples. The results showed that the ME, FE and LA from fruits, FE and LA were able to trigger an inhibition in NO and H2O2 levels, as well as IL-1ß, IL-6, and TNF-α released by macrophages in a concentration-dependent manner. LA from C. cainito fruits was found to significantly attenuate carrageenan-induced paw edema and TPA-induced ear edema. Therefore, the results suggest ME, FE and LA isolated from C. cainito fruits have anti-inflammatory effects on macrophages without affecting cell viability.

Diversifying Complexity by Domino Benzannulation of Polycyclic Natural Products.

Herein we describe a salicylaldehyde-annulation reaction as a plug and play toolkit to diversify the complexity of naturally occurring ketones. The protocol entails the transformation of the polycyclic natural ketone into its propargyl vinyl ether derivative (two synthetic steps) and its microwave-assisted imidazole-catalyzed domino rearrangement to generate the salicylaldehyde ring. This annexed unit allows further synthetic transformations: e.g., the installation of a pharmacophore module to generate natural product-pharmacophore hybrids endowed with unknown biological (pharmaceutical) annotations.

Enantiodivergent Synthesis of (+)- and (-)-Pyrrolidine†197B: Synthesis of trans-2,5-Disubstituted Pyrrolidines by Intramolecular Hydroamination.

A highly efficient, diastereoselective, iron(III)-catalyzed intramolecular hydroamination/cyclization reaction involving α-substituted amino alkenes is described. Thus, enantiopure trans-2,5-disubstituted pyrrolidines and trans-5-substituted proline derivatives were synthesized by means of a combination of enantiopure starting materials, easily available from l-α-amino acids, with sustainable metal catalysts such as iron(III) salts. The scope of this methodology is highlighted in an enantiodivergent approach to the synthesis of both (+)- and (-)-pyrrolidine 197B alkaloids from l-glutamic acid. In addition, a computational study was carried out to gain insight into the complete diastereoselectivity of the transformation.

4-Methyl-N-(4-methyl-phenyl-sulfon-yl)-N-[4-(4-methyl-phen-yl)-1,3-thia-zol-2-yl]benzene-sulfonamide.

There are two independent mol-ecules in the asymmetric unit of the title compound, C24H22N2O4S3. In each, the sulfonamide N atoms reveal nearly a trigonal-planar geometry with two S atoms of the O=S=O groups and one C atom of the thia-zole ring; the angles around the N atoms are between 117.00 (13) and 123.86 (9)°. The methyl-phenyl-sulfonyl groups are in anti conformations, forming dihedral angles of 78.00 (7)/72.53 (5) and 77.09 (6)/71.50 (7)° with the trigonal S-N-S planes in the two mol-ecules. The thia-zole groups are rotated around the C-N bonds and are almost perpendicular to the S-N-S plane [dihedral angles of 78.00 (7)/72.53 (5) and 77.09 (6)/71.50 (7)°]. In the crystal, pairs of C-H⋯O inter-actions, with the O atoms of the sulfonamide groups as acceptors, link each of the independent mol-ecules into inversion dimers.

Bis(2-amino-4-phenyl-1,3-thia-zol-3-ium) tetra-chlorido-palladate(II).

The title compound, (C9H9N2S)2[PdCl4], consists of two monoprotonated 2-amino-4-phenyl-1,3-thia-zole molecules and one tetra-chlorido-palladate anion. The organic molecules exhibit a dihedral angle between the main rings planes of 31.82 (9)°. In the anion, the Pd(II) atom is located on a crystallographic centre of symmetry with a square-planar geometry. In the crystal, the anions and cations are connected through bifurcated N-H⋯Cl hydrogen bonds, and these inter-actions lead to hydrogen-bonded tapes of cations and anions along [100].

Molecular orbital and topological electron density study of n → π* interactions: amides and thioamides cases.

The n → π* interactions were studied in amides and thioamides systems models, through the analysis of the electron density topology along with the Natural Bonding Orbital (NBO) approach. The effect of the dispersion terms was assessed using different DFT functionals. The NBO, independent gradient model (IGM), and the analysis of the reduced density gradient outcomes show that dispersion forces play a significant role in the strength of n → π* interactions. The IGM results indicate that δg height values for n → π* interactions do not extend beyond 0.025. All the methods used in this work predict that n → π* interaction between pairs of thioamides is stronger than those between amides. However, the electron density topology-based methods were not able to replicate the trends in the relative force of this interaction found in the experimental and NBO results.

Lupeol acetate isolated from Chrysophyllum cainito L. fruit as a template for the synthesis of N-alkyl-arylsulfonamide derivatives and their synergistic effects with metronidazole against Trichomonas vaginalis.

Pentacyclic triterpenes are found in a great variety of natural products and constitute an organic template for the development of new derivative compounds with therapeutic applications. In the present work, lupeol acetate isolated from Chrysophyllum cainito L. fruit was used as a template for the synthesis of novel N-alkyl-arylsulfonamide derivatives, and their synergistic effects with metronidazole against strains of Trichomonas vaginalis were tested. A library of 18 derivatives was synthesized. Ten compounds exhibited an IC50 < 100 µM against a metronidazole-sensitive strain of T. vaginalis. Only seven of these compounds (12, 15, 18-22) also showed activity against metronidazole-resistant strains. The compounds 20 (N-cyclohexyl-p-chlorobenzenesulfonamidolupeol acetate) and 22 (N-cyclohexyl-p-nitrobenzenesulfonamidolupeol acetate) exhibited a similar IC50 against both susceptible and resistant T. vaginalis strains and enhanced the efficacy of metronidazole in a partial and total synergistic way, respectively. These data provided evidence of the trichomonicidal effect of N-alkyl-arylsulfonamide derivatives of lupeol acetate, representing highly promising novel antiparasitic agents.

Iron(III)-promoted aza-Prins-cyclization: direct synthesis of six-membered azacycles.

[reaction: see text] A new iron(III) halide-promoted aza-Prins cyclization between gamma,delta-unsaturated tosylamines and aldehydes provides six-membered azacycles in good to excellent yields. The process is based on the consecutive generation of gamma-unsaturated-iminium ion and further nucleophilic attack by the unsaturated carbon-carbon bond. Homoallyl tosylamine leads to trans-2-alkyl-4-halo-1-tosylpiperidine as the major isomer. In addition, the alkyne aza-Prins cyclization between homopropargyl tosylamine and aldehydes gives 2-alkyl-4-halo-1-tosyl-1,2,5,6-tetrahydropyridines as the only cyclic products.

Antiproliferative evaluation of N-sulfonyl-2-alkyl-six membered azacycles. A QSAR study.

A series of functionalized N-sulfonyl-piperidines and N-sulfonyl-tetrahydropyridines were evaluated for their antiproliferative activity against the representative panel of human solid tumor cells A2780 (ovarian), SW1573 (non-small cell lung) and WiDr (colon). The SAR study showed for WiDr cells a correlation between the biological activity and the length of the N-sulfonyl group, the nature of the substituents and the type of alkyl side chain. Further QSAR studies indicate that the size and nature of the N-sulfonyl group, the atomic polarizability (MP) and the partition coefficient are the most important descriptors for the activity. The major contribution is the size (F05C-S) of the N-sulfonyl group.

Iron(III)-catalyzed consecutive aza-Cope-Mannich cyclization: synthesis of trans-3,5-dialkyl pyrrolidines and 3,5-dialkyl-2,5-dihydro-1H-pyrroles.

An efficient alkene aza-Cope-Mannich cyclization between 2-hydroxy homoallyl tosylamine and aldehydes in the presence of iron(III) salts to obtain 3-alkyl-1-tosyl pyrrolidines in good yields is described. The process is based on the consecutive generation of a γ-unsaturated iminium ion, 2-azonia-[3,3]-sigmatropic rearrangement, and further intramolecular Mannich reaction. Iron(III) salts are also shown to be excellent catalysts for the new aza-Cope-Mannich cyclization using 2-hydroxy homopropargyl tosylamine.

A new catalytic Prins cyclization leading to oxa- and azacycles.

A new Prins cyclization process that builds up one carbon-carbon bond, one heteroatom-carbon bond, and one halogen-carbon bond, (in an oxa- and azacycle) relies on an iron catalyst system formed from Fe(acac)3 and trimethylsilyl halide. The method displays a broad substrate scope and is economical, environmentally friendly, and experimentally simple. This catalytic method permits the construction of chloro, bromo and iodo heterocycles, by the suitable combination of iron(III) source, the corresponding trimethylsilyl halide and the solvent, in high yields.

beta'-Hydroxy-alpha,beta-unsaturated ketones: A new pharmacophore for the design of anticancer drugs. Part 2.

Novel antiproliferative beta'-acyloxy-alpha,beta-unsaturated ketones were obtained by means of an iron(III)-catalyzed multicomponent domino process (ABB' 3CR). The most active derivatives displayed GI(50) values in the range of 0.5-3.9 muM against a panel of representative human solid tumor cell lines: A2780, SW1573, HBL-100, T-47D and WiDr. Analysis of cells following 24 h exposure to these drugs showed cell cycle arrest in the S and G(2)/M phase, in a dose-dependent manner. Our data indicate that the beta'-acyloxy-alpha,beta-unsaturated ketones cause permanent damage to the cells and induce apoptosis.

Antiproliferative activity of 2-alkyl-4-halopiperidines and 2-alkyl-4-halo-1,2,5,6-tetrahydropyridines in solid tumor cell lines.

A series of trans-2-alkyl-4-halopiperidines and 2-alkyl-4-halo-1,2,5,6-tetrahydropyridines were prepared by means of an iron(III) catalyzed process. The in vitro antiproliferative activities were examined in the human solid tumor cell lines A2780 (ovarian cancer), SW1573 (non-small cell lung cancer), and WiDr (colon cancer). The results on the biological activity revealed that, in general, the 2-alkyl-4-halo-1,2,5,6-tetrahydropyridine analogs are more potent than the trans-2-alkyl-4-halopiperidine derivatives. A remarkable selectivity of the aza compound 5f for the resistant cell line WiDr was observed. Cell cycle studies revealed a G(2)/M phase arrest for 5f.