Radical promoted Wagner-Meerwein-type rearrangement of epoxides in camphoric systems using a Ti(III) radical source

[Chemical reaction: see text] A radical based Wagner-Meerwein-type rearrangement has been observed in camphoric systems. The radical was generated from the epoxide using Cp2TiCl as the radical source. The radical initiator Cp2TiCl was prepared in situ from commercially available Cp2TiCl2 and Zn dust in THF under argon.     

A General Approach to Intermolecular Olefin Hydroacylation through Light-Induced HAT Initiation: An Efficient Synthesis of Long-Chain Aliphatic Ketones and Functionalized Fatty Acids

Herein, an operationally simple, environmentally benign and effective method for intermolecular radical hydroacylation of unactivated substrates by employing photo-induced hydrogen atom transfer (HAT) initiation is described. The use of commercially available and inexpensive photoinitiators (Ph₂CO and NHPI) makes the process attractive. The olefin hydroacylation protocol applies to a wide array of substrates bearing numerous functional groups and many complex structural units. The reaction proves to be scalable (up to 5 g). Different functionalized fatty acids, petrochemicals and naturally occurring alkanes can be synthesized with this protocol. A radical chain mechanism is implicated in the process.     

Use of allylzinc halide as a source of halide: Differential addition of nucleophiles to Ts-aziridines and aldehydes under similar reaction conditions

We have observed that the allylic zinc halide under identical reaction conditions acts in different modes for different electrophiles. For Ts-aziridines the halide part of the allylic halide has been introduced as a nucleophile and for the carbonyl compounds the simple allylation reaction occurs. To the best of our knowledge this is the first report where the allylic zinc halide is the source of halide acting as nucleophile. The main advantages of the present procedure are easy to handle, no need of inert atmosphere, mild reaction conditions, and applicability to a wide variety of substrates for aziridines and carbonyl compounds.     

Structural Transformation of Bovine Serum Albumin Induced by Dimethyl Sulfoxide and Probed by Fluorescence Correlation Spectroscopy and Additional Methods

Determining the structure of a protein and its transformation under different conditions is key to understanding its activity. The structural stability and activity of proteins in aqueous–organic solvent mixtures, which is an intriguing topic of research in biochemistry, is dependent on the nature of the protein and the properties of the medium. Herein, the effect of a commonly used cosolvent, dimethyl sulfoxide (DMSO), on the structure and conformational dynamics of bovine serum albumin (BSA) protein is studied by fluorescence correlation spectroscopy (FCS) measurements on fluorescein isothiocyanate (FITC)‐labeled BSA. The FCS study reveals a change of the hydrodynamic radius of BSA from 3.7 nm in the native state to 7.0 nm in the presence of 40 % DMSO, which suggests complete unfolding of the protein under these conditions. Fluorescence self‐quenching of FITC has been exploited to understand the conformational dynamics of BSA. The time constant of the conformational dynamics of BSA is found to change from 35 μs in its native state to 50 μs as the protein unfolds with increasing DMSO concentration. The FCS results are corroborated by the near‐UV circular dichroism spectra of the protein, which suggest a loss of its tertiary structure with increasing concentration of DMSO. The intrinsic fluorescence of BSA and the fluorescence response of 1‐anilinonaphthalene‐8‐sulfonic acid, used as a probe molecule, provide information that is consistent with the FCS measurements, except that aggregation of BSA is observed in the presence of 40 % DMSO in the ensemble measurements.     

Kinetics of Pu(IV) sorption by smectite-rich natural clay

Kinetics of sorption of Pu(IV) by smectite-rich clay has been studied at varying metal ion concentrations. Different concentrations were achieved using different isotopes of Pu, namely, ²³⁹Pu, ²³⁸Pu and ²³⁷Pu. ²³⁷Pu was produced by alpha induced reaction on ²³⁵U, followed by radiochemical separation of Pu from irradiated U₃O₈ target. The concentrations used are above and below the solubility of Pu(IV) under neutral pH conditions, thereby, indicating the mechanism of sorption reactions of Pu(IV) in typical laboratory experiments and field level observations. Kinetics of Pu(IV) at 10^?13 M concentration was found to be fast whereas at higher metal concentration the rate is governed by a slow step, indicating the role of formation of Pu(IV) polymeric species at the sorbent surface.     

Chalepin and Chalepensin: Occurrence,Biosynthesis and Therapeutic Potential

Dihydrofuranocoumarin, chalepin (1) and furanocoumarin, chalepensin (2) are 3-prenylated bioactive coumarins, first isolated from the well-known medicinal plant Ruta chalepensis L. (Fam: Rutaceae) but also distributed in various species of the genera Boenminghausenia, Clausena and Ruta. The distribution of these compounds appears to be restricted to the plants of the family Rutaceae. To date, there have been a considerable number of bioactivity studies performed on coumarins 1 and 2, which include their anticancer, antidiabetic, antifertility, antimicrobial, antiplatelet aggregation, antiprotozoal, antiviral and calcium antagonistic properties. This review article presents a critical appraisal of publications on bioactivity of these 3-prenylated coumarins in the light of their feasibility as novel therapeutic agents and investigate their natural distribution in the plant kingdom, as well as a plausible biosynthetic route.     

Quality Related Safety Evaluation of a South African Traditional Formulation (PHELA®) as Novel Anti-Biofilm Candidate

A South African traditional formulation, PHELA^®, is consumed by the traditional people for severe chest problems with coughing, diarrhea, oral ulcers etc. The present study focused on establishing the anti-infective properties of a safe and standardized poly-herbal formulation through a series of criteria and specifications.     

Effect of Controlled Deposition of ZnS Shell on the Photostability of CdTe Quantum Dots as Studied by Conventional Fluorescence and FCS Techniques

The effect of one and two monolayers of ZnS shells on the photostability of CdTe quantum dots (QDs) in aqueous and nonaqueous media has been studied by monitoring the fluorescence behavior of the QDs under ensemble and single‐molecule conditions. ZnS capping of the CdTe QDs leads to significant enhancement of the fluorescence brightness of these QDs. Considerable enhancement of the photostability of the shell‐protected QDs, including the suppression of photoactivation, is also observed. Fluorescence correlation spectroscopy measurements reveal an increase in the number of particles undergoing reversible fluorescent on–off transitions in the volume under observation with increasing excitation power; this effect is found to be more pronounced in the case of core‐only QDs than for core–shell QDs.     

Reducing methane formation in methanol to olefins reaction on metal impregnated SAPO-34 molecular sieve

SAPO-34 silicoaluminophosphate molecular sieve produces large amounts of methane at elevated temperatures in the methanol to olefins (MTO) process. This significantly reduces the lower olefins selectivity a key factor in determining the commercial viability of this catalyst. Impregnation of the SAPO-34 molecular sieve with metal ions such as K, Cs, Pt, Ag and Ce was found to reduce the amount of methane significantly at higher temperatures thereby increasing the lower olefins selectivity. This observed effect is less apparent at lower temperatures where the amount of methane formed is generally low. This revised version was published online in June 2006 with corrections to the Cover Date.