Regioselective nucleophilic ring-opening reaction of chiral epoxyallyl alcohols: a ready access to the pyran core of macrolactin 3

Herein we report the synthetic strategy towards the pyran core of macrolactin 3 via Sharpless epoxidation, titanium(IV) mediated regioselective ring-opening reaction of epoxyallyl alcohol/epoxy alcohol and oxa-Michael addition as the key steps.     

An investigation on visible luminescence of Ho activated LBTAF glasses

Different concentrations of Ho³⁺-doped lead borate titanate aluminum fluoride (LBTAFHo) glasses with chemical composition of PbO-H₃BO₃-TiO₂-AlF₃-Ho₂O₃ were prepared by the melt quenching method. The spectral properties were investigated using the absorption, emission and decay measurements. The experimental oscillator strengths were calculated from the area under the absorption bands. Applying Judd-Ofelt theory, the intensity parameters (Ω_{λ=2, 4, 6}) were calculated, by the least square fit approach from which the radiative transition rates, luminescence branching ratios and radiative decay times were determined. The photoluminescence spectra revealed the quenching of luminescence intensity beyond 1.0 mol% of Ho³⁺ ion concentration. To investigate the luminescence potentiality of ⁵F₄→⁵I₈ emission level, the effective bandwidth and the stimulated emission cross-section were determined. The quenching in experimental decay time is attributed to the resonance energy transfer among the excited Ho³⁺ ions.     

Radiation chemistry of tris(acetylacetonato) cobalt(iii) in aqueous solutions

Abstract

On radiolysis tris(acetylacetonato) cobalt(III) in aqueous solutions is found to get reduced by reaction with (1) hydrated electrons, (2) H atoms, (3) OH radicals and (4) C₂H₂OH radicals. The bimolecular rate constants for the first three reactions, determined by competition kinetics are: 4 × 10¹⁰, 2.3 × 10⁹ and 4.7 × 10⁹ M^?1sec^?1 respectively. Absorption spectra of the irradiated solutions indicate the formation of bis(acetylacetonato) cobalt(II) from reaction (1), but not from (3). The total cobaltous yield in air-free solutions is given byG(Co⁺⁺) = 5.6 and 6.5 at pH 6.5 and 1 respectively. It appears that G_eaq- ∽ _H ⁺ G_oH ∽ 2.8 in neutral solutions. Considerations of material balance for the primary yields of radiolysis of water suggest the possibility that the so-called independent H-atoms in neutral solutions are probably excited water molecules or ion-pairs.     

Quantitative estimation of constituents in fly ash by lithium tetraborate fusion

Silica is removed from fly ash sample by hydroflourination for its effective determination gravimetrically and the remaining residue is subjected to lithium tetraborate (Li₂B₄O₇) fusion followed by dissolution in dilute nitric acid to obtain a clear solution in which elements including aluminum (Al), iron (Fe), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu) and zinc (Zn), have been determined by Flame Atomic Absorption Spectrometry (FAAS). Two fly ash samples analyzed by the proposed method have been received from the National Council of Cement and Building Materials (NCCBM), India (proposed CRM in future) and fly ash CRM 1633 (b) from NIST, USA. The validity of the method has been established by analyzing fly ash CRM 1633 (b) as reference standard. The standard deviation has been calculated for each measurement.     

A Short New Synthesis of Ethyl trans-Chrysanthemate

The discovery of synthetic pyrethroids with increased insecticidal activity and low mammalian toxicity led to abundance of new synthetic results in the chemistry of pyrethroids¹ . Many of these methods adopted on an industrial scale make use of sigmatropic rearrangement, radical addition and nucleophilic ring closer with carbanions. Herein we report a simple and stereospecific route for the synthesis of ethyl trans-chrysanthernate (1) by utilizing carbonyl stabilized sulphuranes. Although the use of Sulphurane was demonstrated at a much earlier stage for the synthesis of methyl trans-chrysanthe-mate², the present approach makes use of simple reagents and offers some operational advantages.     

Electroinitiated Polymerization of Acrylamide Using Tartaric Acid as Electrolyte

Abstract

Acrylamide has been polymerized electrochemically in aqueous medium in the presence of tartaric acid, and the effects of such reaction variables as monomer concentration, electrolyte concentration, and current on the rates of polymerization have been studied. The mechanisms of initiation and termination have been discussed in the light of the observed kinetic data. Initiation is believed to occur through the generation of radical ions during electrolysis, and electrolytic termination is found to be negligible during the polymerization process.     

Validated liquid chromatography–tandem mass spectrometry method for simultaneous quantitation of bendamustine and copanlisib in mouse plasma: Application to a pharmacokinetic study in mice

In this study, we report the development and validation of an LC–tandem mass spectrometry method for the simultaneous quantitation of bendamustine and copanlisib in mouse plasma as per the US FDA regulatory guidelines. The sample processing involves extraction of bendamustine and copanlisib along with internal standard (IS; warfarin) from 50 μL mouse plasma using a liquid–liquid extraction method. The chromatographic separation of bendamustine, copanlisib and the IS was achieved on an Atlantis dC₁₈ column using an isocratic mobile phase (5 mM ammonium acetate:methanol, 20:80 v/v). Bendamustine, copanlisib and the IS eluted at 0.88, 1.39 and 0.74 min, respectively, with a total run time of 2.5 min. The calibration curve ranged from 3.99–2996 and 4.33–3248 ng/mL for bendamustine and copanlisib, respectively. Inter- and intra-day precision and accuracy, stability in processed samples and upon storage, dilution integrity and incurred sample reanalysis were investigated for both the analytes. The intra- and inter-day precisions were in the ranges of 2.01%–5.05% and 2.74%–6.13% and 1.98%–7.64 and 8.62%–9.04% for bendamustine and copanlisib, respectively. Stability studies showed that both analytes were stable on bench top for 6 h, in auto-sampler for 24 and at −80°C for 30 days. The validated method was successfully applied to a pharmacokinetic study in mice.