The first one-pot oxidative 1,2-acetoxysulfenylation and 1,2-disulfenylation of Baylis-Hillman alcohols in an ionic liquid

The first example of tandem oxidation and 1,2-acetoxysulfenylation/1,2-disulfenylation of Baylis-Hillman (BH) alcohols to afford 1,2-acetoxysulfides/1,2-dithioethers is reported. The reaction involves oxidation of BH alcohols with IBX in [bmim]Br to give β-ketomethylene compounds in situ followed by CuI-imidazole-catalyzed 1,2-acetoxysulfenylation with an organodisulfide and acetic acid under air to afford vicinal acetoxysulfides in excellent yields with complete regioselectivity. In the absence of the Cu(I) catalyst, 1,2-disulfenylation takes place to give vicinal dithioethers in 81-90% yields.     

IBX/LiBr-promoted one-pot oxidative anti-Markownikov bromohydroxylation/bromoalkoxylation of Baylis-Hillman olefins

The first example of one-pot oxidative anti-Markownikov bromohydroxylation and bromoalkoxylation of Baylis-Hillman (BH) adducts (olefins) is reported. The reaction is performed at rt using LiBr as the bromine source and 2-iodoxybenzoic acid (IBX) as the oxidant. The process involves oxidation of BH adducts with IBX to give β-ketomethylene compounds in situ, which undergo highly regioselective vicinal functionalization with LiBr/H₂O or LiBr/ROH in the same vessel to afford α-bromo-β-hydroxy or α-bromo-β-alkoxy compounds, respectively, in excellent yields. The α-bromo-β-hydroxy compounds are readily transformed into epoxides in aq NaOH.     

The first ionic liquid-promoted one-pot diastereoselective synthesis of 2,5-diamino-/2-amino-5-mercapto-1,3-thiazin-4-ones using masked amino/mercapto acids

The first expeditious synthesis of 2,5-diamino-/2-amino-5-mercapto-1,3-thiazin-4-ones from masked and activated amino/mercapto acids, viz. 2-phenyl-1,3-oxazol-5-one or 2-methyl-2-phenyl-1,3-oxathiolan-5-one, aromatic aldehydes and thioureas using the ionic liquid [Bmim]Br as an environmentally benign reaction promoter is reported. The synthesis is highly diastereoselective and involves tandem Knoevenagel, Michael and ring transformation reactions in a one-pot procedure. The sequential reaction pathway is supported by the isolation of arylidene derivatives and their Michael adducts with thiourea, and quantitative conversion of the latter into the final products under the same reaction conditions.     

Characterization of two epimers, 4alpha and 4beta, of a novel podophyllotoxin-4-O-(D)-6-acetylglucopyranoside from Podophyllum hexandrum by LC-ESI-MS-MS

High-performance liquid chromatography (HPLC) with diode array detection interfaced to electrospray ionization (ESI) mass spectrometry (MS) is applied to identify the two epimers of a novel and minor constituent, podophyllotoxin-4-O-(D)-6-acetylglucopyraniside from high-altitude Podophyllum hexandrum for the first time. This is done by matching the structural information from the tandem MS data with the reported lignan markers. The results show that LC-MS-MS is the method of choice for fast detection and detailed chemical analysis of mixtures in the crude extracts of Podophyllum. The method can be employed in the absence of reference standards for the markers and is particularly useful in view of the scarcity of these rare chemical standards.     

Reversal of Magnetisation in Ising Ferromagnet by the Field Having Gradient

We have studied the reversal of magnetisation in Ising ferromagnet by the field having gradient along a particular direction. We employed the Monte Carlo simulation with Metropolis single spin flip algorithm. The average lifetime of the metastable state was observed to increase with the magnitude of the gradient of applied field. In the high gradient regime, the system was observed to show two distinct region of up and down spins. The interface or the domain wall was observed to move as one increases the gradient. The displacement of the mean position of the interface was observed to increase with the gradient as hyperbolic tangent function. The roughness of the interface was observed to decay exponentially as the gradient increases. The number of spin flip per site was observed to show a discontinuity in the vicinity of the domain wall. The amount of the discontinuity was found to diverge with the system size as a power law fashion with an exponent 5/3.     

Overview of nano-drugs characteristics for clinical application: the journey from the entry to the exit point

The ever-increasing number of diseases worldwide requires comprehensive, efficient, and cost-effective modes of treatments. Among various strategies, nanomaterials fulfill most of these criteria. The unique physicochemical properties of nanoparticles have made them a premier choice as a drug or a drug delivery system for the purpose of treatment, and as bio-detectors for disease prognosis. However, the main challenge is the proper consideration of the physical properties of these nanomaterials, while developing them as potential tools for therapeutics and/or diagnostics. In this review, we focus mainly on the characteristics of nanoparticles to develop an effective and sensitive system for clinical purposes. This review will present an overview of the important properties of nanoparticles, through their journey from its route of administration until disposal from the human body after accomplishing targeted functionality. We have chosen cancer as our model disease to explain the potentiality of nano-systems for therapeutics and diagnostics in relation to several organs (intestine, lung, brain, etc.). Furthermore, we have discussed their biodegradability and accumulation probability which can cause unfavorable side effects in healthy human subjects.     

Simultaneous quantification of five marker compounds of Betula utilis stem bark using a validated high-performance thin-layer chromatography method

A sensitive, selective and robust densitometric high-performance thin-layer chromatographic method was developed and validated for five marker compounds, namely betulin, lupeol, oleanolic acid, 3-acetyloleanolic acid and β-sitosterol, known for their various therapeutic activities. The marker compounds have been isolated from the stem bark of Betula utilis, well characterized by the spectral analysis, and their simultaneous quantitative determination carried out by high-performance thin-layer chromatography (HPTLC) method. The resolution of marker compounds was carried out on silica-gel 60 plates, using n-hexane:ethyl acetate (8:2 v/v) as the mobile phase. The HPTLC densitometry was performed at 500-nm wavelength after the post chromatographic derivatization with ceric ammonium sulfate reagent. The optimized method provided good linear relation (r>0.9960) for all the investigated analytes. The method is simple, and reproducible, which may be applied for quantitative analysis of the above-mentioned marker compounds.     

Infrared absorption and Raman spectroscopy studies of InSbBi layers grown by liquid phase epitaxy

We report on the results of optical absorption and Raman spectroscopy measurements on InSbBi layers grown by liquid phase technique. A maximum Bi content of 0.4 at.%, as measured by energy dispersive X-ray (EDX) technique, is used in the experiments. Optical absorption measurements made on the samples indicate a room temperature energy band gap reduction up to about 6 meV with respect to undoped InSb layers grown by the same technique. Bi content calculated from this band gap reduction agrees with that obtained from EDX. A weak peak obtained at 152 cm^?1 in the Raman spectrum of the material is identified with the longitudinal optical phonon mode of InBi. Further a mode at 140 cm^?1 is observed due to isolated Bi atoms at the interstitial sites.     

Influence of Tb doping on the luminescence characteristics of ZnO nanoparticles

Structural and optical properties of the Tb-doped ZnO nanoparticles with average diameter ≈4 nm have been systematically investigated. Our X-ray diffraction studies show a contraction of the ZnO lattice with the increase of the Tb mole-fraction x for x ≤ 0.02 and an expansion beyond x ≈ 0.02. The photoluminescence spectra are found to be comprised of a near band edge ultra violet luminescence (UVL) and a broad green luminescence (GL) band. Under the atmospheric condition, the intensity of the GL band is found to increase with the Tb mole-fraction over the entire doping range. On the other hand, under the vacuum condition, it has been observed that the GL intensity decreases with the increase of x up to x ≈ 0.02 but further increase of x leads to a gradual revival of the GL emission. Our study suggests that for x ≤ 0.02, GL results due to the physisorption of certain groups on the surface of the nanoparticles (GL-groups). It is also found that in this Tb mole-fraction regime, Tb incorporates mostly on the surface of the nanoparticles and affects the UVL to GL intensity ratio by influencing the attachment of the GL-groups. However, for x > 0.02, GL originates not only from the GL-groups but also from certain point defects, which are likely to be generated due to the incorporation of Tb in the core of the nanoparticles. A simple rate equation model is introduced to get a quantitative understanding about the variation of the density of the centers responsible for the GL emission as a function of x under the atmospheric and the vacuum conditions.     

Landauer formula for phonon heat conduction: relation between energy transmittance and transmission coefficient

A Fibonacci chain is composed of oscillators with two different masses and its total (even) number of oscillators N is associated with Fibonacci numbers. The momentum autocorrelation function of a specific oscillator in the chain is shown to be combination of 1?+?(N/2) cosines, their frequencies and amplitudes are calculated numerically for N????40. The momentum autocorrelation functions are illustrated for Fibonacci chains with N up to 176.