Phthalanilic acids as highly selective reagents for the amperometric determination of thorium(IV)

Th(IV) has been determined by amperometric titration at an applied emf of -1.0 V with ten phthalanilic acids. Of these, the 2,5-dichloro, 4-bromo, 3-nitro, 4-nitro and 1-naphthyl derivatives were found promising analytical reagents and most effective. Th(IV) in the range 11.6-1160 mg/10O ml can be determined with an error of +/- 0.3%. The possible interference of 46 ions was studied and only two. Pd(II) and Zr interfered; they could be masked by the addition of dimethylglyoxime or Nioxime, and pyrophosphate respectively.     

System of two servers in bi-series with a serial service channel and phase type service

Summary The paper studies the time independent solution of a queueing system wherein units demanding one, two or three service phases arrive at the three service channels. It is assumed that first two channels are bi-serial to each other and both are separately in series with a common server. Poisson arrivals and exponential service times are assumed at all the three service channels of the system. Mean queue length of the system for infinite number of input sources has been obtained. Also, mean queue length of the system for finite number of input sources has been found out. Some particular cases of importance are given in the end.

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Zusammenfassung Der Aufsatz behandelt die zeitunabhängige Lösung eines Warteschlangenproblems, dessen Elemente ein, zwei oder drei Bedienungsphasen erfordern. Das System besteht aus drei Stationen. Die ersten beiden sind bi-seriell zueinander und jede für sich in Reihe zur dritten Station angeordnet (vgl. Abb. 1). An allen Stationen werden poissonverteilte Ankünfte und exponentiell verteilte Bedienzeiten vorausgesetzt. Es wird die mittlere Warteschlangenlänge sowohl für offene als auch für geschlossene Systeme angegeben. Einige wichtige Spezialfälle bilden den Schlu\.

     

Carbonylation reactions of iodoarenes with PAMAM dendrimer-palladium catalysts immobilized on silica

Palladium complexes immobilized onto generation 0-3 PAMAM dendrimers supported on silica were used as catalysts for the carbonylation of iodobenzene in methanol to form methyl benzoate. High yields were obtained and the catalyst was recycled 4-5 times without significant loss of activity. The carbonylation reaction was found to be applicable to a variety of iodoarenes regardless of the nature of the substituent.     

Glycomimetics: a programmed approach toward neoglycopeptide libraries

A programmed synthesis of neoglycopeptides has been developed in which two, similar or different, glycoside moieties could be attached either (i) at the N-terminal of short peptides or (ii) one at the N-internal and the other(s) at the N-terminal site, in a highly flexible and controlled manner. A stepwise branching of N-terminal peptides has been achieved by glycoside aldehyde reductive amination followed by the glycoside carboxylic acid coupling (model 1). In another approach, after N-alkylation with glycoside aldehyde, the N-glycosylated derivative is subjected to peptide synthesis. This is then followed by the attachment of the second glycoside moiety at the N-terminal using either glycoside aldehyde or glycoside carboxylic acid derivative (model 2). Alternatively, the attachment of second and third glycoside derivatives could be achieved simultaneously, by reductive amination/carboxylic acid couplings (model 3). The methodologies presented here are highly versatile and combine diversity in both peptides/pseudopeptides and glycoside moieties.     

An In Silico investigation for acyclovir and its derivatives to fight the COVID-19: Molecular docking,DFT calculations,ADME and td-Molecular dynamics simulations

In the present work, we have designed three molecules, acyclovir (A), ganciclovir (G) and derivative of hydroxymethyl derivative of ganciclovir (CH₂OH of G, that is D) and investigated their biological potential against the Mpro of nCoV via in silico studies. Further, density functional theory (DFT) calculations of A, G and D were performed using Gaussian 16 on applying B3LYP under default condition to collect the information for the delocalization of electron density in their optimized geometry. Authors have also calculated various energies including free energy of A, G and D in Hartree per particle. It can be seen that D has the least free energy. As mentioned, the molecular docking of the A, G and D against the Mpro of nCoV was performed using iGemdock, an acceptable computational tool and the interaction has been studied in the form of physical data, that is, binding energy for A, G and D were calculated in kcal/mol. It can be seen the D showed effective binding, that is, maximum inhibition that A and G. For a better understanding for the inhibition of the Mpro of nCoV by A, G and D, temperature dependent molecular dynamics simulations were performed. Different trajectories like RMSD, RMSF, Rg and hydrogen bond were extracted and analyzed. The results of molecular docking of A, G and D corroborate with the td-MD simulations and hypothesized that D could be a promising candidate to inhibit the activity of Mpro of nCoV.     

Synthesis of Potential Bioactive Novel 7‐[2‐Hydroxy‐3‐(1,2,3‐triazol‐1‐yl)propyloxy]‐3‐alkyl‐4‐methylcoumarins

A series of 50 novel 7‐[2‐hydroxy‐3‐(1,2,3‐triazol‐1‐yl)propyloxy]‐3‐alkyl‐4‐methylcoumarins had been designed and synthesized in good to excellent yields via Cu(I)‐catalyzed 1,3‐dipolar cycloaddition reaction “click chemistry” of 7‐(3‐azido‐2‐hydroxypropyloxy)‐3‐alkyl‐4‐methylcoumarins with variety of acetylene derivatives. In turn, the precursor compound, that is, 7‐(3‐azido‐2‐hydroxypropyloxy)‐3‐alkyl‐4‐methylcoumarin, was synthesized by condensation of epichlorohydrin with 7‐hydroxy‐3‐alkyl‐4‐methylcoumarins followed by opening of the epoxide ring in the resulted 7‐epoxymethoxy‐3‐alkyl‐4‐methylcoumarins with sodium azide. All the synthesized compounds were unambiguously identified on the basis of their spectral data analyses (IR, ¹H‐NMR, ¹³C‐NMR spectra, and HRMS).     

Synthesis of biologically important novel fluorinated spiro heterocycles under microwaves catalyzed by montmorillonite KSF

The arylidienes of fluorinated spiro thiazolidines (5) containing α,β-unsaturated function have been used as component of Micheal addition with equimolar amount of 2-aminopyridine (6a) to give novel fluorinated spiro [indole-3,2′-pyrido[1,2-a]thiazolo[5,4-e]pyrimidines] (7) in a single step under microwaves in presence of montmorillonite KSF as solid support. The new improved synthetic method for fluorinated spiro [indole-3,2′-thiazolo[4,5-d]pyrimidines] (8) has also been developed involving the reaction of (5) with thiourea under monomode microwave reactor. Comparison with conventional synthesis and multimode microwave oven indicated the enhanced yield with faster reactions under monomode microwave reactor. Structure-activity relationships between the chemical structures and the antimycobacterial, antifungal activity of the evaluated compounds are also discussed.     

Biosensor for total cholesterol estimation using N-(2-aminoethyl)-3-aminopropyltrimethoxysilane self-assembled monolayer

Cholesterol oxidase (ChOx), cholesterol esterase (ChEt), and horseradish peroxidase (HRP) have been co-immobilized covalently on a self-assembled monolayer (SAM) of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTS) deposited on an indium–tin–oxide (ITO) glass surface. These enzyme-modified (ChOx-ChEt-HRP/AEAPTS/ITO) biosensing electrodes have been used to estimate cholesteryl oleate from 10 to 500 mg dL⁻¹. The sensitivity, K _m value, and shelf-life of these ChEt-ChOx-HRP/AEAPTS/ITO biosensing electrodes have been found to be 124 nA mg⁻¹ dL, 95.098 mg dL⁻¹ (1.46 mmol L⁻¹), and ten weeks, respectively. The ChEt-ChOx-HRP/AEAPTS/ITO bio-electrodes have been used to estimate total cholesterol in serum samples. Figure Covalent immobilization of enzymes onto AEAPTS/ITO surface using EDC/NHS chemistry Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.