Synthesis of some benzimidazole- and benzothiazole-derived ligand systems and their precursory diacids

Procedures are described for the preparation of various bidentate and linear tetradentate benzimidazoles and benzothiazoles incorporating units such as pyridyl and thioether, and for the preparation of certain thioether dicarboxylic acids precursory to them. Condensations of ortho-functinal anilines with carboxylic acids were carried out in polyphosphoric acid or refluxing HCl solution. Syntheses are reported for: [HO₂C(CH₂)2S(CH₂)₂]₂X (X = O, S), 1,9-bis(benzimidazol-2-yl)-2,5,8-trithianonane, 1,11-bis(N-methylbenzimidazol-2-yl)-3,6,9-trithiaundecane, 1,11-bis(2-benzimidazol-2-yl)-6-oxo-3,9-dithiaundecane, 2-(2-pyridyl)benzothiazole, 2,6-bis(benzothiazol-2-yl)pyridine, 2-(2-pyridyl)-N-methylbenzimidazole, 2-(2-pyridylmethyl)benzimidazole and 2-(N-methyl-2-piperidyl)benzimidazole. The compounds were characterized, where appropriate, by their mass, uv and ¹H-nmr spectra.     

Development and Validation of a Liquid Chromatographic Method for Determination of Efavirenz in Human Plasma

A simple, rapid, and sensitive high-performance liquid chromatographic method for estimation of efavirenz in human plasma has been developed and validated. Chromatography was performed with C₁₈ analytical column and 50:50 acetonitrile–phosphate buffer (pH 3.5) as mobile phase. Compounds were monitored by UV detection at 247 nm. The retention time for efavirenz was 6.45 min and that for the internal standard, nelfinavir, was 2.042 min. Response was a linear over the concentration range of 0.1 μg–10 μg mL⁻¹ in human plasma. The method was simple, specific, precise and accurate and was useful for bioequivalence and pharmacokinetic studies of efavirenz.     

Total synthesis of d-(+)-biotin

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

Ab initio structure determination of new compound Ba3(BO3)(PO4)

The crystal structure of new compound Ba₃BPO₇ was determined by ab initio method from high-resolution conventional X-ray powder diffraction data. The Rietveld refinement converged to R_p=5.92%, R_wp=8.87%, R_exp=5.00% with the following details: Hexagonal, space group P6₃mc, a=5.4898 (1) Å, c=14.7551(1) Å, Z=2. The basic unit of the structure is the [BaO₁₀]-[BO₃]-[PO₄] polar polyhedra-chain composed of Ba1-B-P-O cluster. These chains, running along c-axis, stack in a HCP mode to build the whole structure with triangular prism channels. The channels are parallel to c-axis too, in which Ba2 and Ba3 are located.     

Radiochemical separation of bismuth activities using Dalzin,and its application to geological problems

A radiochemical method has been devised for the separation of bismuth activities of the natural series,viz.²¹⁴Bi,²¹⁰Bi and²¹²Bi, and applied to the indirect estimation of their corresponding precursors,²²²Rn,²¹⁰Pb and²¹²Pb, in a wide variety of geological materials. The method consists of the solvent extraction of bismuth in radiochemically pure form from the sample solution atpH 2 with diallyldithiocarbamido-hydrazine (Dalzin) in chloroform, and back extraction with 2M acid. The advantages of this method over the dithizone extraction system are discussed.     

Hydroboration and diimide reduction of caryophyllene and isocaryophyllene

The monohydroboration of caryophyllene with dicyclohexylborane followed by oxidation brought about the participation of the (E)-trisubstituted double bond in preference to the exocyclic double bond during hydroboration to the corresponding unsaturated alcohol. This alcohol gave the corresponding ketone by oxidation. Isocaryophyllene under similar conditions provided the unsaturated alcohol as the major product, wherein the participation of the exocyclic double bond took place during hydroboration. Our attempts to achieve cyclic hydroboration with caryophyllene or isocaryophyllene using thexylborane resulted in the formation of the corresponding unsaturated alcohol. We achieved partial regioselective reduction of caryophyllene and isocaryphyllene with diimide to produce the corresponding dihydroderivative.     

A force field study of diacetylene molecule by kinetic constant method

The potential constants of diacetylene molecule has been evaluated using kinetic constants. The other molecular constants such as the generalised vibrational mean amplitudes, shrinkage constants, Coriolis coupling constants and centrifugal distortion constants are also calculated using the vibrational frequencies and the results discussed.     

Complexometric titration of total iron with o-mercaptobenzoic acid as indicator

The soluble deep blue complex of iron(II) with o-mercaptobenzoic acid in aqueous pyridine medium (pH 6.4-7.4) can be titrated with EDTA at room temperature with a sharp colour change from blue to light yellow. o-Mercaptobenzoic acid forms a 2:1 complex with iron(II), maximum absorption at 600 nm. Its stability constant was found to be log K = 7.7. With iron(III), a transient blue colour is first formed which soon becomes colourless and then on the addition of excess of reagent, the deep blue complex is formed on reduction of the iron(III). Iron can be titrated in the presence of copper, if the latter is masked with sodium thiosulphate. Cobalt and nickel interfere. Common anions such as chloride, tartrate, phosphate, oxalate, citrate and acetate have no interference.     

Catalytic amination of 2-substituted pyridines with hydrazine derivatives

[reaction in text] Protected pyridylhydrazine derivatives were prepared in a one-step palladium-catalyzed amination reaction using chelating phosphine ligands. 2-Pyridyl chlorides, bromides, and triflates were effective electrophiles in these reactions. Di-tert-butyl hydrazodiformate was an excellent hydrazine substrate, and the resulting products were deprotected under mild conditions. Catalytic amination provides a direct route to protected bifunctional hydrazinopyridine linkers that are suitable for metal-bioconjugate syntheses.     

Fluorimetric determination of boron with resacetophenone as a reagent

Summary A method has been developed for the fluorimetric determination of boric acid, which gives a blue fluorescence with resacetophenone in sulphuric acid or phosphoric acid medium. The method has the advantage that the reaction does not require much time, because the fluorescence intensity reaches its maximum immediately after mixing the reagents and does not also decrease with time. The intensity of fluorescence can be measured with a fluorimeter and the amount of boric acid determined from a calibration curve.