Application of metal free aromatization to total synthesis of perlolyrin,flazin, eudistomin U and harmane

Application of our recently reported metal free reaction conditions to the total synthesis of the four different and selective biologically interesting β-carboline natural products is reported. Using this simple methodology, flazin, perlolyrine, eudistomin U and harmane containing heteroaryl and alkyl substituents at C1 position were synthesized in good yields.

     

Synthesis,characterization, biological screening and molecular docking studies of 2-aminonicotinaldehyde (ANA) and its metal complexes

The biological and optical importance of the o-aminoaldehyde family of ligands inspired us to evaluate the coordination properties and biological activities of 2-aminonicotinaldehyde (ANA). Here, we report the synthesis, characterization, biological screening and molecular docking studies of ANA and its metal complexes of Ni(II), Pd(II), Co(II) and Cu(II) using various analytical and spectroscopic techniques. The single crystal X-ray diffraction studies of ANA explain the solid-state assembly and an interesting supramolecular herring bone stacking pattern by classical N–H···O/N intra/inter molecular and non-classical C–H···O/N intermolecular H-bonding. ANA and its metal complexes were screened for in vitro anticancer, antimicrobial and anti-oxidant activities. Anticancer activity was tested against HeLa, MCF-7 and HEK293 human cancer cell lines. The [Ni(ANA)₂Cl₂] complex showed good activity against HeLa and MCF-7, the [Pd(ANA)₂Cl₂] and [Cu(ANA)₂Cl₂] complexes against HeLa, and the [Co(ANA)₂Cl₂] complex against MCF-7. In antimicrobial screening, the [Co(ANA)₂Cl₂] and [Cu(ANA)₂Cl₂] complexes were proved to be potent antibacterial and antifungal agents. The anti-oxidant activity of these complexes was investigated through DPPH radical assay, and it was found that all the complexes have good radical scavenging capability. Molecular docking studies were also carried for all the metal complexes against EGFR as a target protein by using Autodock, and the results strongly correlated with the anticancer activity.     

Green chemical multicomponent approach for the synthesis of C3-pyranopyrazole-substituted coumarins

An efficient and rapid method was developed for the synthesis of C3-pyranopyrazole-substituted coumarins from one-pot five-component reaction of β-keto ester, hydrazine, O-hydroxy aromatic aldehydes, 6-methyl, 4-hydroxy pyranone and aromatic aldehyde in the presence of tri-ethylamine in solvent-free conditions. The microwave-assisted method reported herein offers advantageous shorter reaction times, higher yields and cleaner reaction compared with conventional heating methods.     

Zn-proline catalyzed selective synthesis of 1,2-disubstituted benzimidazoles in water

Zn-proline (5 mol%) performs as a novel water-soluble and recyclable Lewis acid catalyst for the selective synthesis of 1,2-disubstituted benzimidazoles from wide range of substituted o-phenylenediamines and aldehydes in moderate to excellent isolated yields (42-92%) using water as solvent at ambient temperature.     

Chemical Degradation of Mercury Alkyls Mediated by Copper Selenide Nanosheets

Methylation and demethylation of mercury compounds are two important competing processes that control the net production of highly toxic mercury alkyls, methylmercury (MeHg⁺) and dimethylmercury (Me₂Hg), in environment. Although the microbial and the photochemical methylation and demethylation processes are well studied in recent years but the chemical methylation and demethylation processes have not been studied well. Herein, we report for the first time that the CuSe nanosheet has remarkable ability to activate the highly inert Hg?C bonds of various MeHg⁺ and Me₂Hg compounds at room temperature (21 °C). It facilitates the conversion of MeHg⁺ into Me₂Hg in the absence of any proton donors. Whereas, in the presence of any proton source, it has unique ability to degrade MeHg⁺ into CH₄ and inorganic mercury (Hg²⁺). Detailed studies revealed that the relatively fast Hg?C bond cleavage was observed in case of MeHgSPh or MeHgI in comparison to MeHgCl, indicating that the Hg?C bond in MeHgCl is relatively inert in nature. On the other hand, the Hg?C bond in Me₂Hg is considered to be exceedingly inert and, thus, difficult to cleave at room temperature. However, CuSe nanosheets showed unique ability to degrade Me₂Hg into CH₄ and Hg²⁺, via the formation of MeHg⁺, under acidic conditions at room temperature. DFT calculations revealed that the Hg?C bond activation occurs through adsorption on the surface of (100)‐faceted CuSe nanosheets.     

Light scattering by coated Gaussian and aggregate particles

Light scattering by nonspherical and inhomogeneous small particles is studied by varying particle shapes, sizes, and compositions. We introduce an efficient tool for deforming particle shape and composition by adding a coating on an initial particle. This concave-hull transformation is applied to wavelength-scale Gaussian and aggregate particles, and the differences in the optical properties of the coated particles are compared to those of the uncoated geometries. The light-scattering computations are performed using the discrete-dipole approximation method which allows for internal inhomogeneity and irregular particle shapes. The results are analyzed concentrating on the intensity of the scattered light, the degree of linear polarization for unpolarized incident light, and the depolarization ratio. Polarization results yield the most significant differences and, moreover, coated aggregates are observed to produce net positive polarization, whereas it is negative for the Gaussian particles, also resembling the polarization of a spherical particle. As for the depolarization ratio, an intriguing double-lobe feature is observed near the backscattering direction for both particle geometries regardless of size, shape, and composition. The double-lobe maxima and minima generally coincide with those of the intensity and polarization.     

Synchronous Luminescence Spectroscopic Characterization of Urine of Normal Subjects and Cancer Patients

Urine is one of the diagnostically potential bio fluids, as it contains many metabolites and some of them are native fluorophores. These fluorophores distribution and the physiochemical properties may vary during any metabolic change or at different pathologic conditions. Since urine is a multicomponent fluid, synchronous luminescence technique, a powerful tool has been adopted to analyse multicomponents in single spectrum and to resolve emission spectrum without much of photobleaching of fluorophores. In this study, urine samples of both normal subjects and cancer patients were characterised using synchronous luminescence spectroscopy with a Stokes shift of 20 nm. Different ratio parameters were calculated from the intensity values of the synchronous luminescence spectra and they were used as input variables for a multiple linear discriminant analysis across normal and cancer groups. The stepwise linear discriminant analysis classifies 90.3 % of the original grouped cases and 88.6 % of the cross-validated grouped cases correctly.     

Microwave backscattering by nonspherical ice particles at 5.6 GHz using second-order perturbation series

Scattering of microwaves by an ensemble of nonspherical ice particles is studied using a scattering model based on a second-order perturbation series at 5.6 GHz (C-band). Particle shapes are defined using a Gaussian random sphere geometry. Particle inhomogeneity is taken into account using three different effective-medium approximations: Maxwell–Garnett, Bruggeman, and Coherent Potential mixing rules. By systematically varying particle size, liquid water content, Gaussian shape parameters, and internal structure, it is found that liquid water content is the most important factor for the co-polarized backscattering; the shape is relatively unimportant. For depolarized backscattering, the shape is of fundamental importance, although the other factors are significant too. Surprisingly, the type of nonsphericity is found to be important for depolarization even for scatterers that are in the Rayleigh region: elongated targets depolarize clearly stronger than more irregular shapes. This finding seems not to be strongly size dependent, at least for size parameters from 0.0059 to 0.47, and indicates that the accurate modeling of shape is important for polarization quantities even in the Rayleigh region.