Interligand interactions controlling the mu-N7,N9-metal bonding of adenine (AdeH) to the N-benzyliminodiacetato(2-) copper(II) chelate and promoting the N9 versus N3 tautomeric proton transfer: molecular and crystal structure of [Cu2(NBzIDA)(2)(H2O)(2)(mu-N7,N9-Ade(N3)H)].(3)H2O

The reaction in water of the N-benzyliminodiacetate-copper(II) chelate ([Cu(NBzIDA)]) and the adenine:thymine base pair complex (AdeH:ThyH) with a Cu/NBzIDA/AdeH/ThyH molar ratio of 2:2:1:1 yields [Cu(2)(NBzIDA)(2)(H(2)O)(2)(mu-N7,N9-Ade(N3)H)].3H(2)O and free ThyH. The compound has been studied by thermal, spectral, and X-ray diffraction methods. In the asymmetric dinuclear complex units both Cu(II) atoms exhibit a square pyramidal coordination, where the four closest donors are supplied by NBzIDA in a mer-tridentate conformation and the N7 or N9 donors of AdeH, which is protonated at N3. The mu-N7,N9 bridge represents a new coordination mode for nonsubstituted AdeH, except for some adeninate(1-)-[methylmercury(II)] derivatives studied earlier. The dinuclear complex is stabilized by the Cu-N7 and Cu-N9 bonds and N6-H(exocyclic)...O(carboxyl) and N3-H(heterocyclic)...O(carboxyl) interligand interactions, respectively. The structure of the new compound differs from that of the mononuclear compound [Cu(NBzIDA)(Ade(N9)H)(H(2)O)].H(2)O, in which the unusual Cu-N3(AdeH) bond is stabilized by a N9-H...O(carboxyl) interligand interaction and where alternating benzyl-AdeH intermolecular pi,pi-stacking interactions produce infinite stacked chains. The possibility for ThyH to be involved in the molecular recognition between [Cu(NBzIDA)] and the AdeH:ThyH base pair is proposed.     

High-Performance Thin-Layer Chromatographic Determination of Itopride Hydrochloride in its Pharmaceutical Preparation and in the Bulk Drug

JPC – Journal of Planar Chromatography – Modern TLC - A normal-phase high-performance thin-layer chromatographic (HPTLC) method has been established for quantitative estimation of...     

Preconcentration of trace metals on Amberlite XAD-4 resin coated with dithiocarbamates and determination by inductively coupled plasma-atomic emission spectrometry in saline matrices

Preconcentration of Cd(II), Cu(II), Mn(II), Ni(II), Pb(II) and Zn(II) in saline matrices on Amberlite XAD-4 resins coated with ammonium pyrrolidine dithiocarbamate (APDC) and piperidine dithiocarbamate (pipDTC) and subsequent determination by inductively coupled plasma atomic emission spectrometry were studied. Parameters such as effect of pH, effect of HNO(3) concentration on elution of metals from resin were studied. The results show that Amberlite XAD-4 coated with APDC was more efficient in the recovery of metal ions compared with Amberlite XAD-4 coated with pipDTC, in the concentration range of 0.1-200 mug l(-1), for 1 g of Amberlite XAD-4 coated resin. The detection limits for Cd(II), Cu(II), Mn(II), Ni(II), Pb(II), Zn(II) are 0.1, 0.4, 0.3, 0.4, 0.6, 0.5 mug l(-1), respectively, for resin coated with APDC and 0.7, 1.0, 0.8, 0.9, 1.7 and 1.2 mug l(-1) for resin coated with pipDTC. The effect of diverse ions on the determination of aforesaid metals was studied. The method was applied for the determination of trace metal ions in artificial sea water and natural water samples. The results were compared with extraction AAS method.     

A Highly stereospecific and efficient synthesis of homopentafluoro- phenylalanine

A short and efficient synthesis of homopentafluorophenylalanine (6) from oxazolidine aldehyde 1 in 57% overall yield and in > 98% ee is described. The enantiomeric excess of the product was determined by 19F NMR analysis of the coupling product derived from 5 and L-Ser(O-t-Bu)-OCH3, by comparison to a dipeptide obtained from racemic 5.     

Design of oxygen reduction bimetallic catalysts: ab-initio-derived thermodynamic guidelines

The Gibbs free energies of key elementary steps for the electrocatalytic oxygen reduction reaction (ORR) are calculated with B3LYP type of density functional theory: O2 + M + H+ + e- (0 eV) --> HOO-M (deltaG1), HOO-M + M --> HO-M + O-M (deltaG2), O2 + 2M + H+ + e- (0 eV) --> O-M + HO-M (deltaG3), and HO-M + O-M + 3H+ + 3e- (0 eV) --> 2H2O + 2M (deltaG4), where H+ is modeled as H3(+)O(H2O)3 and M stands for the adsorption site of a metal catalyst modeled by a single metal atom as well as by an M3 cluster. Taking Pt as a reference, deltaG4 is plotted against deltaG1 for 17 metals from groups V to XII. It is found that no single metal has both deltaG1 and deltaG4 more negative than Pt, although some of them have either more negative deltaG1 or more negative deltaG4. This enables us to explain thermodynamically why no other single metal catalyzes the ORR as effectively as Pt does. Moreover, a thermodynamic analysis reveals that the signs of delta deltaG (the difference between deltaG of other metals and deltaG of Pt) strongly correlate with the valence electronic structure of metals, i.e., delta deltaG1 < 0 and delta deltaG4 > 0 for metals M with vacant valence d orbitals, whereas delta deltaG1 > 0 and delta deltaG4 < 0 for metals M' with fully occupied valence d orbitals. Thus, a simple thermodynamic rule for the design of bimetallic catalysts for the ORR is proposed: couple a metal M (delta deltaG1 < 0) with a second metal M' (delta deltaG4 < 0) to form an alloy catalyst MM'3. The rationale behind this selection is based on M being more efficient for the rate-determining step, i.e., for the formation of the adsorbed species M-OOH, while M' can enhance the reductions of O and OH in the last three electron-transfer steps.     

Efficient oxidizing methods for the synthesis of oxandrolone intermediates

Mild, efficient and eco-friendly oxidation of 17alpha-methylandrostan-3beta-17beta-diol (1) has been studied with three different reagents viz. pentavalent iodine reagent 2-iodoxy benzoic acid (IBX) in DMSO at 65 degrees C, sodium hypochlorite and H2O2/Na2WO4 under phase transfer conditions to give 17beta-hydroxy-17alpha-methylandrostan-3-one (mestanolone 2), a drug intermediate as oxidized product. The H2O2/Na2WO4/PTC gave mestanolone in high yield and purity whereas sodium hypochlorite/PTC system yielded some chlorinated material along with the mestanolone. However, 1 with 2.5 equivalent of IBX gave 17beta-hydroxy-17alpha-methyl-Delta1-androsten-3-one (3) under the similar reaction conditions in good yield and single step reaction.     

Production of ethanol from cellulosic biomass by Clostridium thermocellum SS19 in submerged fermentation

Carotenogenesis of the lactose-negative yeast Rhodotorula rubra GED5 was studied by cocultivation with Kluyveromyces lactis MP11 in whey ultrafiltrate (WU) (35, 50, and 70 g of lactose/L). Maximum yields of cell mass (24.3 g/L) and carotenoids (10.2 mg/L of culture fluid or 0.421 μ g/g of dry cells) were obtained by growing the microbial association in WU (50 g of lactose/L) in a fermentor with an airflow rate of 0.8 L/(L·min), agitation of 220 rpm, and temperature of 30°C. The identified carotenoid pigments—β-carotene, torulene, and torularhodin—reached maximum concentrations (133, 26.9, and 222.3 μg/g of dry cells, respectively) on d 5 for torulene and d 6 for β-carotene and torularhodin.     

Acyclic Schiff base salts derived from 1,3‐diaminopropane and 1,3‐diamino‐2‐hydroxypropane

Two salts of acyclic Schiff base cationic ligands, namely N,N′‐bis(2‐nitrobenzyl)propane‐1,3‐diammonium dichloride monohydrate, C₁₇H₂₂N₄O₄²⁺·2Cl⁻·H₂O, (I), and 2‐hydroxy‐N,N′‐bis(2‐nitrobenzyl)propane‐1,3‐diammonium dichloride, C₁₇H₂₂N₄O₅²⁺·2Cl⁻, (II), were synthesized as precursors in order to obtain new acyclic and macrocyclic multidentate ligands and complexes. The cation conformations in compounds (I) and (II) are different in the solid state, although the cations are closely related chemically. Similarly, the hydrogen‐bonding networks involving ammonium cations, hydroxyl groups and chloride anions are also different. In the cation of compound (II), the hydroxyl group is disordered over two sets of sites, with occupancies of 0.785 (8) and 0.215 (8).     

Physical noise model of a uniformly doped nanoscale FinFET photodetector

The noise mechanisms of a uniformly doped nanoscale FinFET photodetector including quantum mechanical effects is investigated theoretically. A numerical model has been developed for computation of different noise components in nanoscale FinFET. The drain current channel thermal noise under illuminated conditions is calculated. The noise parameters of the nanoscale FinFET equivalent circuit are strongly influenced by the incident optical signal and the quantum mechanical effects are found to play a major role in determining the overall noise performance of the device. It also reveals that the operating frequency can be adjusted suitably to make the noise behavior independent of the incident optical power. Other noise components such as Shot noise, thermal noise and diffusion noise have been calculated for the two port FinFET photodetector. Signal-to-noise ratio (SNR), Bit error rate (BER) and noise equivalent power (NEP) has also been calculated.     

Development and validation of LC‐MS/MS method for the estimation of β‐hydroxy‐β‐methylbutyrate in rat plasma and its application to pharmacokinetic studies

A simple, sensitive and specific high‐performance liquid chromatography mass spectrometry (LC‐MS/MS) method was developed and validated for the quantification of β‐hydroxy‐β‐methyl butyrate (HMB) in small volumes of rat plasma using warfarin as an internal standard (IS). The API‐4000 LC‐MS/MS was operated under the multiple reaction‐monitoring mode using the electrospray ionization technique. A simple liquid–liquid extraction process was used to extract HMB and IS from rat plasma. The total run time was 3 min and the elution of HMB and IS occurred at 1.48 and 1.75 min respectively; this was achieved with a mobile phase consisting of 0.1% formic acid in a water–acetonitrile mixture (15:85, v/v) at a flow rate of 1.0 mL/min on a Agilent Eclipse XDB C₈ (150 × 4.6, 5 µm) column. The developed method was validated in rat plasma with a lower limit of quantitation of 30.0 ng/mL for HMB. A linear response function was established for the range of concentrations 30–4600 ng/mL (r > 0.998) for HMB. The intra‐ and inter‐day precision values for HMB were acceptable as per Food and Drug Administration guidelines. HMB was stable in the battery of stability studies, viz. bench‐top, autosampler freeze–thaw cycles and long‐term stability for 30 days in plasma. The developed assay method was applied to a bioavailability study in rats. Copyright © 2012 John Wiley & Sons, Ltd.