Regio- and diastereoselective synthesis of anticancer spirooxindoles derived from tryptophan and histidine via three-component 1,3-dipolar cycloadditions in an ionic liquid

A small library of novel hybrid spiroheterocycles containing spirooxindole, pyrrolidine and indole/imidazole moieties were synthesized with complete regio- and diastereoselectively in good to excellent yields from a three-component process starting from a series of variously substituted (E)-(2-nitrovinyl)benzenes, indoline-2,3-dione derivatives and l-tryptophan or l-histidine in an ionic liquid. The key step of this transformation is a 1,3-dipolar cycloaddition reaction involving a rare class of in situ-generated azomethine ylides derived from aromatic amino acids. The compounds thus synthesized were evaluated for their anticancer activity and were shown to inhibit the proliferation of FaDu cells, a human epithelial cell line isolated from a squamous cell carcinoma of the hypopharynx, via apoptotic cell death.     

Further studies on the application of vinylogous amides and β-halovinylaldehydes to the regiospecific synthesis of unsymmetrical,polyfunctionalized 2,3,4- and 1,2,3,4- substituted pyrroles

Highly functionalized pyrroles with appropriate regiochemical functionality represent an important class of marine natural products and potential drug candidates. We describe herein a detailed study of the reaction of α-aminoacid esters with vinylogous amides and also β-halovinylaldehydes for the regiospecific synthesis of 2,3,4-trisubstituted and 1,2,3,4-tetrasubstituted pyrroles. Since the vinylogous amides and β-halovinylaldehydes are readily available precursors, rapid access to a wide variety of unsymmetrically substituted pyrroles is accomplished via this methodology.     

NH4I-catalyzed chalcogen(S/Se)-functionalization of 5-membered N-heteroaryls under metal-free conditions

Herein, we described the NH₄I-catalyzed CH bond chalcogenation of N-heteroaryls in the presence of a minimum amount of DMSO/H₂O/acetic acid as additives (2.5/2.5/1?M equiv., respectively), under metal-free conditions. Under optimized conditions, a wide variety of sulfenyl/selenyl imidazo[1,2-α]pyridines were prepared in very good yields. Moreover, the present approach was also highly efficient for the chalcogenation of different 5-membered N-heteroaryls, e.g., indole, imidazothiazole, indazole and imidazopyrimidine derivatives.     

Enhancement of antibacterial efficiency at silver electrodeposited on coconut shell activated carbon by modulating pulse frequency

The natural antibacterial activity of silver represents an alternative to deal with the ever increasing pathogenic breakouts related with contaminated water resources. In this study, silver was deposited on the surface of activated carbon (AC) particles via pulsed electrodeposition (PED) employing an electrochemical reactor operating at fixed and fluidized bed regimes. Silver-coated activated carbon (Ag/AC) particles were prepared at different current pulse frequency values. Antimicrobial properties of the produced material were tested against two well-known foodborne pathogens, i.e., Escherichia coli O157:H7 and Salmonella typhimurium. The results demonstrate a strong influence of the applied current pulse frequency on both the bactericidal efficiency and the specific surface of silver deposited on the activated carbon. Antibacterial results demonstrate up to eight orders of magnitude decrease in the CFU cm^?3 (colony-forming units per cm³) against both microorganisms in just 20 min contact time. Additional chronoamperometry transient data were fitted to the Scharifker-Hills nucleation model for the electrodeposition of silver at a rotating disk electrode, revealing an instantaneous nucleation growth processes. The Ag/AC particles were characterized by field emission scanning electron microscopy (FE-SEM), specific surface area (S_BET), Raman spectroscopy, energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD), demonstrating the existence of crystalline phase formation of a preferential (200) plane growth with silver and silver oxide being present.

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Local well-posedness for higher order nonlinear dispersive systems

We study nonlinear dispersive systems of the form

On The Homotopy Type of

We consider the homotopy type of classifying spaces , where is a finite -group, and we study the question whether or not the mod cohomology of , as an algebra over the Steenrod algebra together with the associated Bockstein spectral sequence, determine the homotopy type of . This article is devoted to producing some families of finite 2-groups where cohomological information determines the homotopy type of .

     

Synthesis and crystal structure of [{V3(μ-Cl)4(μ 3-Cl) (μ 3-OH)(thf)2(teeda)}2]·2(thf) (teeda = N,N,N′N′-tetraethylethane-1,2-diamine)

The title complex was prepared from the reaction of [V₂(-Cl)₃(thf)₃]₂[Zn₂Cl₆] with N,N,NN-tetraethylethane-1,2-diamine (teeda) in refluxing thf and its crystal structure exhibits two triangulo-[V₃(-Cl)₃(-Cl)( ₃-OH)(thf)₂(teeda)]⁺ cations bridged by two chlorides. The molecular structure (monoclinic, space group P2 ₁/n, Z = 2, a = 11.8005(7) Å, b = 18.7492(14) Å, c= 15.6253(9) Å, = 103.600(4) shows each vanadium site in a distorted octahedral geometry. V1 and V2 have two thf molecules bounded in cis configuration, and V3 completes the hexa-coordination with the diamine teeda. Main bond distances are 2.5149(12) Å for V(1)--Cl(1), 2.062(3) Å for V(1)- ₃-O(3), 2.5554(12) Å for V(1)- ₃-Cl(4), 2.140(3) Å for V(1)–O(1)(thf), 2.243(4) Å for V(3)–N(1)(teeda), and 3.0437(9) for V(1)···V(2).     

Molecular structure of 4-(3,5-dimethylpyrazol-1-yl)benzoic acid trifluoroacetate

The crystal and molecular structure of the title compound has been determined by X-ray analysis. 4-(3,5-Dimethylpyrazol-l-yl)benzoic acid trifluoroacetate crystallizes in the 12/a space group witha=20.6584(13),b=9.9068(3),c=14.9467(6) , =106.195(4),V=2937.6(2) ų, Dc=1.494 g/cm³ andZ=8. The ions pack in chains parallel to thea axis through O–HO and N–HO hydrogen bond interactions. Solid-state¹³C CPMASNMR spectroscopy has been used to compare the structure of the trifluoracetate with that of the neutral molecule [4-(3,5-dimethylpyrazol-l-yl)benzoic acid].     

(Imidazole)(3,3′-trimethylenedinitrilo bis (2-butanone oximate)) copper(II) perchlorate: Synthesis and crystal structure of a five-coordinate copper-protein model complex

The synthesis and crystal structure of the novel pentacoordinated complex [Cu(DOHPN)(IMI-DAZOLE)] (ClO4), (DOHPN=(3,3′-trimethylenedinitrilo bis 2-butanone oxime) are reported. The X-ray crystal structure (space groupP2₁/n, a=11.349(2) Å,b=14.241(3) Å,c= 12.635(3) Å; α=90°, β=100.21 (3)°, γ=90°) shows that the copper(II) ion occupies a distorted square-pyramidal geometry with the imidazole ligand occupying the axial position. The copper(II)-(N)imidazole distance is 2.125(3) Å and the copper(II)-tetraaza plane distance is 0.385/Å. The tetraaza ligand DOHPN adopts a “butterfly-like” geometry with a dihedral angle of 149.69°. The title complex is the first structurally characterized compound of the series [Cu(DOHPN)(axial ligand)]ⁿ⁺ where the axial ligand is a neutral N-heterocycle with known biological relevance. A comparison of the structural parameters with those observed when the axial ligand is H₂O or NCS^? (N-bonded) gives the following series with increasing metal-ligand interaction: H₂O>IMIDAZOLE>NCS^? (N-bonded).     

Toward the synthesis of cobyric acid. Enantioselective syntheses of completely differentiated ring D synthons

Alkyne acids 11 were prepared in an enantioselective fashion from allylic ester derivatives 18 or 20 by Ireland-Claisen rearrangement, followed by Si-assisted elimination of HBr. The title compounds are attractive ring D synthons for an ongoing synthesis of cobyric acid.