An effective, orthogonal deprotection strategy for differentially functionalized, linear and Y-shaped oligo phenylene ethynylenes

Several methodologies for the selective deprotection acetylenes have been reported previously. However, as is shown here, they are often not reliable or convenient. Here, an approach is reported that is efficient and general. Use of this approach to synthesize several two- and three-armed oligo(phenylene ethynylene) molecules with differentiated end groups is reported. In addition, preliminary characterization of the fluorescent properties of some of these molecules and their ability to form self-assembled monolayers (SAMs) is reported.     

Applications of new peptide protective groups 1-- a synthesis of bis-s-acetamidomethyl dihydrosomatostatin

A synthesis of $\text{bis}$-S-Acetamidomethyl dihydrosomatostatin is reported in which the C-terminal carboxyl function is protected by the Maq ester function and the N-terminal amine as well as two ε-amino groups of lysine residues are protected as Tcroc urethanes. Clean removal of these groups is reported.     

Highly regio- and stereocontrolled synthesis of β-substituted α-tributylstannyl enamides

The regio- and stereocontrolled synthesis of β-substituted α-stannyl enamides is reported starting from internal ynamides. The synthesis of new ynamides as well as bis-ynamides is also described. Finally first examples of successful cross-coupling to afford α/β-disubstituted enamides are also reported.     

Synthesis and spectral properties of some 1,2-dithienylethenes and 1-thieny1-4-phenylbutadienes

A total of seven thiophene derivatives not previously reported have been prepared via the Knoevenagel condensation of an activated methylthiophene and a heterocyclic or aromatic aldehyde. The principal peaks in the ultraviolet and visible absorption spectra as well as some nuclear magnetic resonance data are reported for these compounds.     

Use of uncertainty estimates as reported by participants in proficiency testing for the evaluation of their results: pros and cons

The aim of this paper is to study the measurement uncertainties reported in proficiency tests (PTs) using examples from PTs in the environmental sector and to compare the obtained measurement uncertainty estimates using different approaches. In addition, the paper focusses on the differences between the z-score and the zeta score. Since the year 2000, the Finnish Environment Institute has asked participants to report analytical methods as well as measurement uncertainties in connection with PT results. The measurement uncertainties of the assigned value have also been evaluated. On the basis of the results, the measurement uncertainties reported by the participants varied greatly. Participants often reported underestimated measurement uncertainties, but overestimated uncertainties were also reported. At the moment, it seems as if performance assessment should be based on the z-score because of a number of significant over- and underestimated measurement uncertainties. The zeta score should be used for information and educational purposes mainly.     

Synthesis of dihydronaphthalenes via aryne Diels-Alder reactions: scope and diastereoselectivity

Novel aryne Diels-Alder reactions with functionalized acyclic dienes are reported. These give useful cis-substituted dihydronaphthalene building blocks in good yield which are not easily accessible via other means, as demonstrated in the synthesis of sertraline. The first asymmetric aryne cycloaddition with an acyclic diene is also reported, giving excellent diastereoselectivities with Oppolzer's sultam as a chiral auxiliary.     

Optical Sol-Gel-Based Dissolved Oxygen Sensor: Progress Towards a Commercial Instrument

A dissolved oxygen sensor based on fluorescence quenching of the oxygen-sensitive ruthenium complex, [Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline]2+, which has been immobilized in a porous silica sol-gel-derived film, is reported. Ormosil sensing films were fabricated using modified silica precursors such as methyltriethoxysilane (MTEOS) and ethyltriethoxysilane (ETEOS) and were dip-coated onto planar glass substrates. Tailoring of the films for dissolved oxygen (DO) sensing is described whereby sensor response is optimized by maximizing film hydrophobicity by the use of the modified precursors. Sensor performance parameters such as limit of detection and sensor resolution are reported. Issues such as dye leaching and photobleaching are discussed. Progress towards a commercial instrument is reported.     

Some alkylphosphoric acid esters for use in coated-wire calcium ion-selective electrodes: Part II. Selectivities and use in potentiometric titrations

The interferences of a range of ions (including the hydrogen ion) on the potential responses of a series of coated-wire calcium-selective electrodes are reported. The extent of the interferences is discussed as a function of the composition of the PVC membranes. The use of these electrodes as end-point sensors in potentiometric titrations of calcium with EDTA is also reported.     

Theoretical calculation of the potential curves of the states of HF below 14 eV

Potential energy curves obtained through extensive ab initio configuration interaction calculations are reported for the states of HF below 14 eV as well as that for the ground state of HF⁺. Agreement with ultraviolet absorption data is obtained to within 0.2 eV. The disagreement between the reported UV absorption and electron scattering data is examined.     

Strongly fluorescent molecular exciplexes in the vapour phase

The first observation in the vapour phase of strongly fluorescent exciplexes between complex polyatomic molecules is reported. Systems studied were electronically excited 9-cyano anthracene as electron acceptors with triethyl and tributyl amine and dimethyl aniline as electron donors, at temperatures in the 185–231°C range. Fluorescence spectra, excitation spectra and preliminary decay time data are reported.     

Synthesis and revision of stereochemistry of rubescensin S

An effective two step transformation of oridonin to 15,16-seco-ent-kaurane skeleton is reported. We also achieved the conversion of one intermediate to natural product rubescensin S and revised its structure as a 13S configuration although 13R is reported in the literature.     

Synthesis and study of the antimalarial cardamom peroxide

A full account of our previously disclosed synthesis of the monoterpene dimer cardamom peroxide is reported. Inspired by hypotheses regarding the potential biosynthetic origins of this natural product, several unproductive routes are also reported. The chemical reactivity of this structurally unique metabolite in the presence of iron (II) sources is also reported as is its antimalarial activity against Plasmodium falciparum clinical isolates from several Cambodian provinces.     

Studies on the amide compounds ofMirabilis. Jalapa. L

Mirabilis himalaica(Edgew.)Heinerl Var. Chinensis Heimerl belonging to the genus Mirabilis are used in chinese medicine as a remedy for various diseases[1].Its chemical constituents,however, have not been reported so far. we have carried out a detailed chemical investigatigation of the seeds and have isolated two new amides along with three known compounds. The known compounds were identified by comparing their spectral data with those of authentic samples or with those reported in literature as daucosterol[2], bsitoserol[2], boeravinone E[3], in the present note, the structural elucidation of two new amides is reported.     

EPR-studies on the chelation of alkali metal cations by radical-anions—IV Radical-anions derived from 1,2,4,5-tetramesitoybenzene

1,2,4,5-Tetramesitoylbenzene was synthesized and reduced with alkali metals as well as electrolytically. EPR spectra of the resulting radical-ion pairs are reported and discussed. The electron-spin densities obtained from temperature coefficient and marked solvent dependency. These effects are compared with the ones observed in the corresponding radical-ion pairs of o-dimesitoylbenzene for which some new data are also reported.     

Arylations of allylic acetates with triarylbismuths as atom-efficient multi-coupling reagents under palladium catalysis

Arylation of allylic acetates employing triarylbismuths as multi-coupling reagents under palladium-catalyzed conditions was reported. Triarylbismuths as nucleophilic coupling partners were used in sub-stoichiometric amounts with respect to allylic acetates and thus served as atom-efficient multi-coupling reagents. A variety of allylic acetates were cross-coupled with triarylbismuths to furnish the corresponding functionalized 1,3-disubstituted propenes in good to excellent yields in short reaction times. The reported palladium protocol also yielded chemo-selective allylic arylations in high yields.     

Distribution of uranium at Mumbai Harbour Bay (MHB)

Mumbai Harbour Bay (MHB) is a recipient of low level treated effluents from BARC, Trombay. In addition, the Bay is also a recipient of domestic and industrial wastes from the city of Mumbai and adjoining areas. The average value of uranium concentration reported for Indian Bay water at Tarapur and Mumbai is ~3.0 ppb which is comparable with the reported value for Arabian sea. As such the global average is reported to be ~3.3 ppb by Oceanologists. The present study deals with the distribution of uranium in seawater of MHB. The uranium activity in MHB by alpha spectrometry was found to be between 1.0 and 4.4 ppb with an average concentration of 2.5 ppb which is comparable with the earlier reported average activity of 2.6 ppb in the MHB as well as those reported globally. To compare the results obtained by alpha spectrometry, uranium estimation was also carried out using Laser fluorimeter and the levels of uranium concentration have ranged between 0.8 and 4.9 ppb with an average concentration of 2.7 ppb.     

Influence of Catalyst on the Formation of 5(10)-Ene Ketals From Estra-4-en-3-ones

The effect of catalyst on formation of isomeric ketals from 19-nortestosterone and 19-nor-ethisterone is reported. Regioselectivity has been achieved with metal hydrides as catalyst, reported for the first time, to give 5(10)-ene ketals.

     

Base-free anaerobic Cu(II) catalysed aryl-nitrogen bond formations

The coupling of arylboronic acids with imidazole in the presence of binuclear bis-μ-hydroxy copper(II) complexes is reported. The reactions can be performed in air as well as under nitrogen atmosphere. Reactions are carried out at ambient temperature without the need for base. The presence of water is essential for the reaction to proceed. Ligand effects on the yield and selectivity are reported.     

PVT properties of PUREX/UREX solvent tri-n-butyl phosphate

Tri-n-butyl phosphate (TBP) is the workhorse of solvent extraction operations in nuclear fuel cycle as well as an important industrial chemical. Its PVT properties are not available in literature. In this study, PVT properties of TBP, estimated using group contribution method, are reported. Wagner constants were also reported in the range of 273.15?K to critical temperature.     

Synthetic studies of new CMP-sialic acid analogues applying a novel buffer-mediated rearrangement

Synthetic studies of analogues of cytidine monophosphate (CMP)-sialic acid as transition state mimics for sialylation are reported, applying selective monohydrolysis of a symmetric diester and a subsequent buffer-mediated regio- and stereospecific rearrangement we reported earlier.