Synthesis of new 4-methyl-3-piperidones via an iron-catalyzed intramolecular tandem isomerization–aldolisation process

A new versatile synthesis of 3-piperidones is described, starting from amino acids. It uses, as a key step, an iron carbonyl-mediated intramolecular tandem isomerization–aldolisation reaction. These new heterocycles appear as useful scaffolds for the total synthesis of various types of bioactive molecules.     

Stereoselective synthesis of an advanced seco ester intermediate as a precursor toward the synthesis of amphidinolides T1, T3, and T4

An efficient, convergent, and stereoselective synthesis of a very advanced intermediate toward the total synthesis of amphidinolides T1, T3, and T4 utilising Evan’s aldol and alkylation reactions, oxy-Michael, cross metathesis, stereoselective Grignard addition, and Yamaguchi esterification reactions as key steps is described.     

One-photon photodetachment of I- in glycerol: spectra and yield of solvated electrons in the temperature range 329<or=T<or=536 K

Solvated electrons in glycerol were generated via a resonant one-photon photodetachment of the charge-transfer-to-solvent (CTTS) band of I- in glycerol (Gl) after irradiation with a 248 nm excimer laser. Optical absorption spectra of solvated electrons (esolv-) in Gl were recorded as a function of temperature (381相似文献   

A new stability indicating reverse phase high performance liquid chromatography method for the determination of enantiomeric purity of a DPP‐4 inhibitor drug linagliptin

A simple, sensitive, and stability indicating isocratic reverse phase high performance liquid chromatography method has been developed, optimized and validated for the separation and quantification of S‐enantiomer in linagliptin (R‐enantiomer) drug substance. Enantiomeric separation was achieved on a Cellulose tris(4‐chloro‐3‐methylphenylcarbamate) stationary phase. Mobile phase consists of aqueous diammonium hydrogen phosphate buffer and acetonitrile in the ratio of 35:65 v/v. Isocratic elution was performed at a flow rate of 1.0 mL/min, the column oven temperature was set at 40°C and detection was at 226 nm. The resolution between R and S enantiomers is found to be more than 4.0. The impact of mobile phase composition, pH of buffer and temperature on the resolution has been studied. The detector response is found to be linear over the concentration range of 0.17–1.7 μg/mL. LOD and LOQ levels of S‐enantiomer are found to be 0.057 and 0.172 μg/mL respectively. The recovery of S‐enantiomer is 99.8% w/w. The proposed method is validated for specificity, precision, linearity, accuracy and robustness.     

Strontium Tetraborate Glasses Doped with Transition Metal Ions: EPR and Optical Absorption Study

Electron paramagnetic resonance (EPR) and optical studies have been carried out on Cu(II)-, VO(II)- and Cr(III)-doped strontium tetraborate glasses to understand the distortion and substitution of these ions. The EPR results of Cu(II) glass indicate that g _∥ > g _⊥, typical for the tetragonally elongated octahedral site of the Cu(II) impurity. The evaluated covalency parameter 0.788 suggests a moderate covalency for the bonding. By correlating EPR and optical results, the in-plane π-bonding β₁ ² is evaluated as 0.715. In the vanadium-doped glasses, the distortion must be a tetragonally elongated octahedron, similar to Cu(II). However, the EPR studies show that g _⊥ > g _∥ indicating the tetragonally compressed octahedral site for the ion. The site symmetry is C _4V. Supported by the optical absorption, evaluated parameters propose a moderate covalency. The EPR and optical results for Cr(III) glass indicate the distorted octahedral site symmetry in the host lattice. These results further suggest that the bonding between Cr(III) and the ligands is covalent. Authors' address: Renduchintala V. S. S. N. Ravikumar, Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar 522510, India     

A holographic,radial and lateral shear interferometer

A new holographic shear interferometer is described in which both the radial and the lateral shear can be simultaneously introduced by using an off-axis zone plate.     

Q,r Inventory Models with Time-Weighted Backorders

This paper attempts to show that the iterative methods that are used to solve a class of reorder point inventory models can be replaced by some non-iterative method. The method is described in general terms and two sufficient conditions are derived to check if the method applies to a model. As illustrations, two time-weighted backorder models are considered and they are solved for Normal and Gamma leadtime demand by the proposed method. It is observed that some of the computational advantages of the method also carry over to a class of multi-item models.     

Ultrafast formation of nonemissive species via intermolecular interaction in single crystals of conjugated molecules

We investigate the influence of interchain interactions on the photoluminescence processes in a sexithiophene single crystal by applying hydrostatic pressure. We perform transient photoluminescence spectroscopy in the time domain of 100 fs for pressures up to 60 kbar. The combined use of steady-state and time-resolved optical spectroscopies allows us to show that the pressure-induced quenching of the photoluminescence is caused by an ultrafast (approximately 100 fs) formation of intermolecular species.     

Thermal conductivity of superconducting lead-indium alloys near the upper critical field

The thermal conductivity of a series of lead/indium alloys was measured in the normal, superconducting and mixed states. The electronic part of the thermal conductivity near the upper critical field was compared with the theory of Caroli and Cyrot. There is good agreement in the dirty limit but large deviations are observed as the indium concentration is reduced.