Spectroscopic,structural, electrochemical,and cytotoxicity studies on dithiocarbamato-chelated ruthenium organometallics incorporating imine-phenol function

The heterogeneous phase reaction of [Ru(η²-RL)(PPh₃)₂(CO)Cl] (1) with the sodium salts of dimethyl dithiocarbamate (^MeDTC), diethyl dithiocarbamate (^EtDTC), and pyrrolidine dithiocarbamate (^PyrDTC) ligands led to the isolation of bright-yellow crystalline solids of type [Ru(η¹-RL)(PPh₃)₂(CO)(^R′DTC)] (2(R)(^R′DTC)) where η²-RL is C₆H₂O-2-CHNHC₆H₄R(p)-3-Me-5, η¹-RL is C₆H₂OH-2-CHNC₆H₄R(p)-3-Me-5, R is Me, OMe, Cl, and R^′ = Me, Et, Pyr. The binding of dithiocarbamate ligand is accompanied by the dissociation of Ru-O and Ru-Cl bonds along with concomitant prototropic shift from iminium–phenolato to imine–phenol motif. The reaction also involves a sterically controlled change in rotational conformation in going to the products. The X-ray crystal structure of [Ru(η¹-ClL)(PPh₃)₂(CO)(^EtDTC)] (2(Cl)(^EtDTC)) has been described here. An account of different spectral (UV–Vis, IR, NMR) and electrochemical data of the complexes are also asserted. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) analyses were performed to scrutinize the electronic structure and the absorption spectra of the complexes. One of the dithiocarbamato complexes has also been found to have in vitro antiproliferative properties against MDA-MB-231 breast cancer cell line which was determined by MTT assay. Cell death occurs mainly through apoptosis and flow cytometric analysis indicates that the complex induces cell cycle arrest in the sub G0/G1 phase.     

Isatin N-protected ketimines with nitromethane catalyzed by chiral binol linked monomeric macrocyclic Cu(II)–salen complex

Chiral Cu-1B generated in situ was used as an efficient catalyst for the synthesis of β-nitroamines in high yield (88%) with excellent enantioselectivity (ee up to 99%) at RT in absence of co-catalyst via asymmetric aza-Henry reaction of various isatin derived N-Boc ketimines with nitromethane. This catalytic system did not work well with other nitroalkanes under the above optimized reaction conditions. To examine this catalytic behaviour, quantum chemical DFT calculations were performed with the nucleophiles (CH₂NO₂^? and CH₃CHNO₂^?) for the conversion of 1a to 2a using macrocyclic Cu-1B complex. The DFT calculated results have shown that the reaction with CH₂NO₂^? is more favourable than the corresponding CH₃CHNO₂^?. The calculated activation barriers suggest that the reaction with CH₂NO₂^? is ～8.0?kcal/mol energetically favoured than CH₃CHNO₂^?. This catalytic protocol was further used to obtain chiral β-diamines (a building block for pharmaceuticals) at gram scale. In order to elucidate the reaction mechanism of asymmetric aza Henry reaction kinetic experiments were performed with different concentrations of the catalyst Cu-1B, nitromethane and 1g as the representative substrate. The reaction of isatin N-Boc ketimine was first order with respect to the concentration of the catalyst and the nitromethane but did not depend on the initial concentration of the substrate. A possible mechanism for the aza Henry reaction was proposed.     

Zero-sum risk-sensitive stochastic games on a countable state space

Infinite horizon discounted-cost and ergodic-cost risk-sensitive zero-sum stochastic games for controlled Markov chains with countably many states are analyzed. Upper and lower values for these games are established. The existence of value and saddle-point equilibria in the class of Markov strategies is proved for the discounted-cost game. The existence of value and saddle-point equilibria in the class of stationary strategies is proved under the uniform ergodicity condition for the ergodic-cost game. The value of the ergodic-cost game happens to be the product of the inverse of the risk-sensitivity factor and the logarithm of the common Perron–Frobenius eigenvalue of the associated controlled nonlinear kernels.     

Quantization dimension function and Gibbs measure associated with Moran set

In this paper we consider the Gibbs measure on the one-sided shift dynamical system and determine the quantization dimension function for the image measure supported on a Moran set. A relationship between the quantization dimension function and the temperature function of the thermodynamic formalism arising in multifractal analysis is also established.     

Wave packet dynamics in monolayer MoS<Subscript>2</Subscript> with and without a magnetic field

We study the dynamics of electrons in monolayer molybdenum disulfide (MoS₂), in the absence as well aspresence of a transverse magnetic field. Considering the initial electronic wave functionto be a minimum uncertainty Gaussian wave packet, we calculate the time dependentexpectation value of position and velocity operators analytically. In the absence of themagnetic field, the time dependent average values of position and velocity show dampedoscillations dependent on the width of the wave packet. In the presence of a transversemagnetic field, the wave packet amplitude shows oscillatory behaviour over shorttimescales associated with classical cyclotron orbit, followed by the phenomena ofspontaneous collapse and revival over larger timescales. We relate the timescales of theseeffects based on general arguments. Our results may also be useful, for the interpretationof experiments with trapped ions, as in [R. Gerritsma, G. Kirchmair, F. Zahringer, E.Solano, R. Blatt, C.F. Roos, Nature 463, 68 (2010)], which performs aproof-of-principle quantum simulation of the one-dimensional Dirac equation.     

Leidenfrost Phenomenon-assisted Thermal Desorption (LPTD) and Its Application to Open Ion Sources at Atmospheric Pressure Mass Spectrometry

This work describes the development and application of a new thermal desorption technique that makes use of the Leidenfrost phenomenon in open ion sources at atmospheric pressure for direct mass spectrometric detection of ultratrace levels of illicit, therapeutic, and stimulant drugs, toxicants, and peptides (molecular weight above 1 kDa) in their unaltered state from complex real world samples without or with minor sample pretreatment. A low temperature dielectric barrier discharge ion source was used throughout the experiments and the analytical figures of merit of this technique were investigated. Further, this desorption technique coupled with other ionization sources such as electrospray ionization (ESI) and dc corona discharge atmospheric pressure chemical ionization (APCI) in open atmosphere was also investigated. The use of the high-resolution ‘Exactive Orbitrap’ mass spectrometer provided unambiguous identification of trace levels of the targeted compounds from complex mixtures and background noise; the limits of detection for various small organic molecules and peptides treated with this technique were at the level of parts per trillion and 10^–9?M, respectively. The high sensitivity of the present technique is attributed to the spontaneous enrichment of analyte molecules during the slow evaporation of the solvent, as well as to the sequential desorption of molecules from complex mixtures based on their volatilities. This newly developed desorption technique is simple and fast, while molecular ions are observed as the major ions.      

Synthetic Studies on Ophiobolins1. Synthesis of 1β (H) -3,7α,11β-Trimethyl-CIS-Bicyclo [6.3.0] Undecan-4-One

In our synthetic studies towards ophiobolin F (1), we report here a stereospecific synthesis of 1β(H)-3,7α,llβ-trimethyl-cis bicyclo [6.3.0]undecan-4-one (2) with defined stereochemistry at each of the four contiguous asymmetric centres and particularly with A/B cis ring juncture as present in (1). It may be mentioned here that no synthetic studies towards developing the characteristic ring systems present in ophiobolins have been reported so far.     

Development of sheath‐flow probe electrospray ionization (SF‐PESI)

Probe electrospray ionization (PESI) uses a sharp solid needle as electrospray emitter. This method was found to be applicable to the analysis of real‐world samples with high concentrations of salts and detergents without sample pretreatment. Since PESI is only applicable to wet samples but not to dry samples, sheath‐flow PESI (SF‐PESI) has been developed. The metal needle was inserted into the fine plastic capillary with a protrusion of 0.1–0.2 mm from the capillary terminus. The solvent was supplied continuously through the capillary. At the lowest position of the probe, solvent flowing out from the capillary makes the sample wet and extracts the analytes from the surface. The extracted analytes were electrosprayed at the highest position of the needle. SF‐PESI was successfully applied to samples such as narcotics, tablets, bill, fruits, potatoes, etc. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthetic studies toward potent cytostatic macrolide rhizopodin: stereoselective synthesis of the C16-C28 fragment

A stereoselective synthesis of the C16-C28 fragment of cytostatic C₂-symmetric macrolide rhizopodin is described. Enantioselective addition of a chiral thiazolidinethione derived titanium enolate to acetal, Evans’ aldol reaction, Horner-Wadsworth-Emmons reaction, and Mukaiyama aldol reaction were applied as key steps.     

Total synthesis of (+)-mupirocin H from D-glucose

Enantioselective total synthesis of mupirocin H is accomplished starting from D-glucose featuring strategic application of D-glucose derived chirality, diastereoselective Still-Barrish hydroboration, and further elaboration of carbon chain to furnish a phenyltetrazolyl sulfone intermediate, which on coupling with (2S,3S)-2-methyl-3-(triisopropylsilyloxy)butanal under Julia-Kocienski olefination conditions gave an advanced E-olefinic intermediate selectively. The E-olefin was transformed to the 4-hydroxynitrile, a prefinal substrate, which on acid-catalyzed oxidative lactonization furnished the target molecule mupirocin H in 19 steps from known compound 6 (longest linear sequence) with an overall yield of 4.96%.