2,4,6-Tris(4-iodophenoxy)-1,3,5-triazine as a new recyclable “iodoarene” for in situ generation of hypervalent iodine(III) reagent for α-tosyloxylation of enolizable ketones

The synthesis of 2,4,6-tris[(4-iodo)phenoxy)]-1,3,5-triazine 6, as a new recyclable nonpolymeric analogue of iodobenzene is achieved using the reaction of 2,4,6-trichloro-1,3,5-triazine with 4-iodophenol in the presence of KOH. The application of 6 as a recyclable ‘iodoarene’ is demonstrated for α-tosyloxylation of enolizable ketones via in situ generation of hypervalent iodine(III) species using PTSA and MCPBA as the terminal oxidant. The recyclability of the reagent 6 was possible owing to the facile recovery and reuse from the reaction mixture due to its near insolubility in methanol.     

Kinetics of the simultaneous oxidation of nickel(II) and sulfur(IV) by oxygen in alkaline medium in Ni(II)–sulfur(IV)–O2 system

In the Ni(II)–S(IV)–O₂ system in the region of pH > 8.4, both Ni(II) and S(IV) are simultaneously autoxidized, and when sulfur is consumed fully NiOOH precipitates. At pH > 8.4, ethanol has no effect on the rate, whereas ammonia strongly inhibits the reaction when pH > 7.0. The kinetics of the reaction, in both the presence and the absence of ethanol, is defined by the rate law where k is the rate constant, K_O is the equilibrium constant for the adsorption of O₂ on ? Ni(OH)₂ particle surface. In ammonia buffer, the factor F is defined by where K, K_OH, K₁, K₂, K₃, and K₄ are the stability constants of NiSO₃, NiOH⁺, Ni(NH₃)²⁺, Ni(NH₃), Ni(NH₃), and Ni(NH₃), respectively. In unbuffered medium, the factor F reduces to The values of k and K^sp were found to be (1.3 ± 0.08) × 10^?1 s^?1 and (4.2 ± 3.5) × 10^?16, respectively, at 30°C. A nonradical mechanism that assumes the adsorption of both SO₃^2? and O₂ on the ? Ni(OH)₂ particle surface has been proposed. At pH ≤ 8.2, Ni(II) displays no catalytic activity for sulfur(IV)‐autoxidation and it is also not oxidized to NiOOH. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 464–478, 2010     

High-Pressure Mössbauer Measurements on Nanocrystalline Perovskite (La,Sr)(Mn,Fe)O3

We report here the Mössbauer measurements on nanocrystalline perovskite structured manganite La_0.8Sr_0.2Mn_0.8Fe_0.19 ⁵⁷Fe_0.01O₃ as a function of pressure up to 10 GPa at room temperature. The nanocrystalline sample, prepared by sol–gel technique found to have crystallite sizes of ∼138 ± 10 Å. Zero-field electrical resistivity measurements with temperature support the nanocrystalline nature. At ambient pressure, Fe³⁺ as well as Fe⁴⁺ ions are distributed in two different environments – Fe³⁺ in low symmetric site surrounded by Mn³⁺ ions only while Fe⁴⁺ in high symmetric site with at least one Mn³⁺ ion. Pressure seems to affect the higher symmetric site. A sudden increase in isomer shift at 0.52 GPa indicates the first order phase transition representing the transformation of Fe⁴⁺ to Fe³⁺. Another transition at 3.7 GPa, represents the presence of Fe³⁺ in single kind of environment. Pressure dependence of electrical resistivity measurements verifies the transitions attributing the first order transition to the cross over of localized-electron to band magnetism.     

NO-NSAIDs. Part 3: nitric oxide-releasing prodrugs of non-steroidal anti-inflammatory drugs

In continuation of our efforts to discover novel nitric oxide-releasing non-steroidal anti-inflammatory drugs (NO-NSAIDs) as potentially "Safe NSAIDs," we report herein the design, synthesis and evaluation of 21 new NO-NSAIDs of commonly used NSAIDs such as aspirin, diclofenac, naproxen, flurbiprofen, ketoprofen, sulindac, ibuprofen and indomethacin. These prodrugs have NO-releasing disulfide linker attached to a parent NSAID via linkages such as an ester (compounds 9-16), a double ester (compounds 17-24), an imide (compounds 25-30) or an amide (compounds 31-33). Among these NO-NSAIDs, the ester-containing NO-aspirin (9), NO-diclofenac (10), NO-naproxen (11), and the imide-containing NO-aspirin (25), NO-flurbiprofen (27) and NO-ketoprofen (28) have shown promising oral absorption, anti-inflammatory activity and NO-releasing property, and also protected rats from NSAID-induced gastric damage. NO-aspirin compound 25, on further co-evaluation with aspirin at equimolar doses, exhibited comparable dose-dependent pharmacokinetics, inhibition of gastric mucosal prostaglandin E(2) (PGE(2)) synthesis and analgesic properties to those of aspirin, but retained its gastric-sparing properties even after doubling its oral dose. These promising NO-NSAIDs could therefore represent a new class of potentially "Safe NSAIDs" for the treatment of arthritic pain and inflammation.     

Modified dispersion properties of lower hybrid wave with exchange correlation potential in ultra-relativistic degenerate plasma

In this letter, the propagation characteristics of lower hybrid waves are investigated in electron–ion degenerate plasma with exchange effect considering non-relativistic, relativistic and ultra-relativistic regimes. The combined effect of Bohm force and exchange correlation potential are found to alter the dispersion properties of lower hybrid waves. The analytical and numerical results clearly show the influence of relativistic velocities of electrons, kinetic pressure of ions, Bohm force and exchange correlation potential on the frequency of the lower hybrid wave. The present work find its relevance for the dense astrophysical environments like white dwarfs and for laboratory fusion plasma experiments.     

Kinetics of the uninhibited and ethanol-inhibited CoO,Co<Subscript>2</Subscript>O<Subscript>3</Subscript> and Ni<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyzed autoxidation of sulfur(IV) in alkaline medium

For getting an insight into the mechanism of atmospheric autoxidation of sulfur(IV), the kinetics of this autoxidation reaction catalyzed by CoO, Co₂O₃ and Ni₂O₃ in buffered alkaline medium has been studied, and found to be defined by Eqs. I and II for catalysis by cobalt oxides and Ni₂O₃, respectively.

In silico screening of neurokinin receptor antagonists as a therapeutic strategy for neuroinflammation in Alzheimer’s disease

Neuroinflammation is one of the detrimental factors leading to neurodegeneration in Alzheimer’s disease (AD) and other neurodegenerative disorders. The activation of microglial neurokinin 1 receptor (NK1R) by substance P (SP) enhances neuroinflammation which is mediated through pro-inflammatory pathways involving NFkB, ERK1/2, and P38 and thus projects the scope and importance of NK1R inhibitors. Emphasizing the inhibitory role of N Acetyl l Tryptophan (l-NAT) on NK1R, this is the first in silico screening of l-NAT mediated NK1R antagonism. In addition, FDA- approved ligands were screened for their potential NK1R antagonism. The l-NAT was docked in XP (Extra Precision) mode while FDA-approved ligands were screened in HTVS (High Throughput Virtual Screening), SP (Standard Precision), and XP mode onto NK1R (PDB:6HLO). The l-NAT and top 3 compounds FDA-approved ligands were subjected to molecular dynamics (MD) studies of 100 ns simulation time. The XP docking of l-NAT, indacaterol, modafinil and alosetron showed good docking scores. Their 100 ns MD showed brief protein–ligand interactions with an acceptable root mean square deviation. The protein–ligand contacts depicted pi-pi stacking, pi-cation, hydrogen bonds, and water bridges with the amino acids necessary for NK1R inhibition. The variable colour band intensities on the protein–ligand contact map indicated their binding strength with amino acids. The molecular mechanics/generalized born surface area (MM-GBSA) scores suggested favourable binding free energy of the complexes. Thus, our study predicted the ability of l-NAT, indacaterol, modafinil, and alosetron as capable NK1R inhibitors that can aid to curb neuroinflammation in conditions of AD which could be further ascertained in subsequent studies.

Graphic Abstract

     

Routing vehicles to minimize fuel consumption

We consider a generalization of the capacitated vehicle routing problem known as the cumulative vehicle routing problem in the literature. Cumulative VRPs are known to be a simple model for fuel consumption in VRPs. We examine four variants of the problem, and give constant factor approximation algorithms. Our results are based on a well-known heuristic of partitioning the traveling salesman tours and the use of the averaging argument.     

New Concise and Efficient Synthesis of Rubrolides C and E via Intramolecular Wittig Reaction

A short total synthesis of rubrolides C and E has been achieved in four steps, using readily available 4‐methoxyacetophenone, 2‐bromoacetic acid, and the appropriate aromatic aldehyde, in 46 and 45% yield, respectively. Key reactions involved are α‐tosyloxylation of the aryl methyl ketone, intramolecular Wittig reaction, Knoevenagel condensation, and demethylation.     

Scattering of Love waves due to the presence of a rigid barrier of finite depth in the crustal layer of the earth

The problem of scattering of Love waves due to the presence of a rigid barrier of finite depth in the crusfal layer of the earth is studied in the present paper. The barrier is in the slightly dissipative surface layer and the surface of the layer is a free surface. The Wiener-Hopf technique is the method of solution. Evaluation of the integrals along appropriate contours in the complex plane yields the reflected, transmitted and the scattered waves. The scattered waves behave as a decaying cylindrical wave at distant points. Numrical computations for the amplitude of the scattered waves have been made versus the wave number. The amplitude falls off rapidly as the wave number increases very slowly.