Total synthesis of d-(+)-biotin

A total synthesis of d-(+)-biotin is described starting from d-(+)-glucosamine using acyliminium chemistry.     

Recent results from the TCV tokamak

During the first two years of operation, the TCV tokamak has produced a large variety of plasma shapes and magnetic configurations, with 1.0B _tor1.46T,I _p800kA,k2.05, –0.71. A new shape control algorithm, based on a finite element reconstruction of the plasma current in real time, has been implemented. Vertical growth rates up to 1000s^–1 have been stabilized using the external coil system. Ohmic H-modes with Troyon factors ( _tor aB/I _p) up to two and densities up to 2.25×10²⁰m^–3, corresponding to the Greenwald limit, have been obtained in diverted discharges. Limiter H-modes with line averaged electron densities up to 1.7×10²⁰m^–3 have been obtained in elongated D-shaped plasmas with 360 kAI _P600 kA.Presented at 17^th Symposium Plasma Physics and Technology, Prague, June 13–16, 1995.This work was partly supported by the Fonds National Suisse de la Recherche Scientifique.     

Pyrimidinethiol as a reagent for extraction separation of platinum metals and gold Determination of Pd(II), Os(VIII) and Ru(III)

The solvent extraction separation of Pt(IV), Pd(II), Os(VIII), Ru(III) and Au(III) from one another and also from Rh(III) and Ir(III) with 1-(2'-nitro-4'-tolyl)-4,4,6-trimethyl-(1H, 4H)-2-pyrimidinethiol has been investigated. Photometric procedures have been developed for the determination of Pd(II), Os(VIII) and Ru(III) with the same reagent. The reagent allows the enrichment of Pd(II) and Au(III) at the trace level from a large volume of aqueous medium even in the presence of base metals. The method can be used for the determination of platinum metals and gold in alloys.     

Eco‐friendly,ultrasound‐assisted,and facile synthesis of one‐pot multicomponent reaction of acridine‐1,8(2H,5H)‐diones in an aqueous solvent

A one‐pot, multistep synthesis of acridine‐1,8(2H,5H)‐diones ( 4a–m ) was achieved by three‐component reaction of dimedone ( 1 ) with an aromatic aldehyde ( 2a–m ) and an ammonium acetate ( 3 ) using water as a green solvent without any catalyst and a simple, easily handled, and ultrasonic technique as well as conventional method.     

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.     

Efficient and mild method for preparation of allylic amines from aziridine-2-alcohols using PPh3/I2/imidazole

Allylic amines are synthesized in good to excellent yields by treatment of aziridine-2-alcohols with PPh₃/I₂/imidazole in THF as solvent under mild conditions.     

Synthesis,Characterization, and Biological Screening of Some Novel Thiazolidin-4-One and α-Aminophosphonate Derivatives

Abstract

Synthesis of some new functionalized thiazolidin-4-ones and α-amino phosphonate derivatives has been reported. The imines were synthesized from the reaction of various substituted anilines with 1-phenyl-3-(pyridine-4-yl)-1H-pyrazole-4-carbaldehyde in ethanol at reflux condition. The corresponding thiazolidin-4-ones and α-aminophosphonates were prepared by reaction of imines with mercaptoacetic acid and triethyl phosphite, respectively. The structures of the newly synthesized compounds were confirmed by IR, ¹H NMR, and mass spectral data and were evaluated for their antimicrobial activities.

GRAPHICAL ABSTRACT      

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.