ENSTAR detector forη- mesic studies

We have initiated a search for a new type of nuclear matter, theη-mesic nucleus, using beams from the multi-GeV hadron facility, COSY at Juelich, Germany. A large acceptance scintillator detector, ENSTAR has been designed and built at BARC, Mumbai and fully assembled and tested at COSY. A test run for calibration and evaluation has been completed. In this contribution we present the design and technical details of the ENSTAR detector and how it will be used to detect protons and pions (the decay products ofη-mesic bound state). The detector is made of plastic scintillators arranged in three concentric cylindrical layers. The readout of the detectors is by means of optical fibres. The layers are used to generate ΔE –E spectra for particle identification and total energy information of stopped particles. The granularity of the detector allows for position (θ and ?ø determination making the event reconstruction kinematically complete     

Vanadium(III) complexes of salicylaldehyde thiosemicarbazones

Hexacoordinate complexes of vanadium(III) containing tridentate ONS chelating substituted salicylaldehyde thiosemicarbazones have been prepared and characterised by elemental analysis, i.r. and u.v.–vis. spectroscopy and cyclic voltammetry.     

Determination of total cationic and total anionic arsenic species in oyster tissue using microwave-assisted extraction followed by HPLC-ICP-MS

A microwave-assisted digestion procedure was developed in presence of concentrated nitric acid (2.0 ml) and 30% hydrogen peroxide (0.20 ml) using a closed pressurized microwave digestion system for the determination of total anionic and total cationic arsenic compounds reside in oyster tissue. At 450 W for 15 min digestion, 74% of anionic arsenic, and 31% of cationic arsenic (105% total arsenic) were retrieved. At 300 W microwave power, 68% of anionic and 30.5% of cationic arsenic (98.5% total arsenic), and 100 W, 63% of anionic and 31% of cationic arsenic (94% total arsenic) were extracted out. The methanol water mixture (9:1) was cull out, exclusively 31.6% of anionic and 29% of cationic arsenic compounds (60.6% total). The dimethylarsinoylriboside (phosphate-arsenosugar) was the predominant arsenic species, along with arsenobetaine (AB), dimethylarsinic acid (DMA), inorganic arsenic, methylarsonic acid (MA), arsenocholine (AC), trimethylarsineoxide (TMAO) and tetramethylarsonium ion (TMI). Some other arsenic compounds, those were not matched with the retention time of the available standards, were also detected. Arsenosugar was fragile and adequately transmuted to DMA (100%), AB and AC to TMAO (100%) when 450 W microwave power was applied for 15 min. The separation and quantification of arsenic compounds in the microwave digests and extracts, were carried out in anion (PRP-X100) and cation (LC-SCX) exchange columns using ICP-MS as arsenic specific detector. The procedure was also validated by determining the total cationic and total anionic arsenic compounds present in DORM 1.     

2‐Pyrazolines from 1,3 ‐ dipolar cycloaddition of diazomethane to arylsulfonylethenes

Novel 2‐pyrazolines were obtained by the cycloaddition of diazomethane to bis(arylsulfonylethenyl)‐sulfones ( 3 ) and 1‐arylsulfonyl‐2‐styrylsulfonylethenes (7). Dehydrogenation of 2‐pyrazolines with chloranil gave pyrazoles.     

Alstonia scholaris: Struktur des Indolalkaloides Narelin

Alstonia scholaris: The structure of the indole alkaloid nareline Besides the known akuammidine, picralinal, picrinine and pseudoakuammigine a new indole alkaloid called nareline (M=352) was isolated from Alstonia scholaris R. BR. , which belongs to the plant family of Apocynaceae. Its structure 2 was deduced by single crystal X-ray diffraction. 2 represents the absolute configuration. The spectroscopic data of 2 and its derivatives (Scheme 1) as well as their chemical behavior support this structure. In biogenetic sense nareline is related to the bases akuammiline ( 4 ) and picraline ( 5 ) (Scheme 2). In contrast to those the C-atom 5 is exocyclic and represents an aldehyde group which forms together with the oxygen atom of the N (4)-hydroxylamine group a cyclic half acetale. - By oxidation (CrO₃/CH₃COOH) of 2 the oxindol derivative 19 (oxonareline) is formed which contains a cyclic acetal as a partial structure element (Scheme 4).     

An interesting ring contraction of a class of bromohydrins and trans-dibromides

An efficient ring contraction of stereoisomeric 1,2-benzo-4-bromo-3-hydroxycyclohept-1-ene and their derivatives (1a-e) to (2a-c) is reported, and a probable mechanism for this ring contraction has been suggested.     

An efficient synthesis of (+)-prelactone B

An enantioselective synthesis of (+)-prelactone B 1 has been achieved on a multigram scale starting from a known bicyclic precursor 2. The key feature of the strategy is the generation of 3-stereogenic centres from a single bicyclic precursor, which has been utilized as a chiral building block for the synthesis of various natural products.     

A study of preferential solvation of N-alkyl pyridinium iodides in mixed solvents containing acetonitrile

The charge transfer (CT) band maximum of N-alkyl pyridinium iodide (NAPI) has been studied as a function of the composition of binary mixed dipolar aprotic solvents. The deviation from linearity of the energy maximum (E₁₂) and the mole fraction (of a component solvent) plot is explained as due to a preferential solvation by the more polar cosolvent in the binary mixture. The extent of preferential solvation has been observed to vary with the composition, the maximum being towards the less-polar end. The role of hydrogen bond donating ability of a solvent in preferential solvation is discussed.