Intramolecular nitrone cycloaddition reaction on carbohydrate-based precursors: application in the synthesis of spironucleosides and spirobisnucleosides

A simple synthesis of chiral spironucleosides and spirobisnucleosides is described. Intramolecular 1,3-dipolar nitrone cycloaddition reaction of d-glucose-derived precursors having olefin at C-3 and nitrone at C-5, C-1, or C-2 (in nor-series) furnished bisisoxazolidinospirocycles 4-7, 11, and 12 in good yields. Reductive ring opening of the isoxazolidine moieties in 4-6 followed by construction of a nucleoside base upon the generated amino groups smoothly yielded spirobisnucleosides 17 and 18 and spironucleosides 20 and 21.     

Conductance studies in amide-water mixtures. II. Sodium salts inN,N-dimethylformamide-water mixtures at 35°C

Conductance data for sodium nitrite, chloride, and acetate in water andN,N-dimethylformamide (DMF)-water mixtures (74.82D42.48) for the concentration range 0.001–0.04N, as well as the densities, viscosities, and dielectric constants of the solvent mixtures at 35°C, are reported. The data have been analyzed by the Fuoss (1975) equation. The existence of a maximum in the viscosity at a 13 mole ratio of DMF and water is indicated. The Walden products for all the three salts pass through a maximum while the equivalent conductances show a minimum with increasing DMF content. The maxima in the Walden product are attributed to the dehydration of ions by the cosolvent (DMF).Part I:Indian J. Chem. 14A, 1015 (1976).Deceased.     

Thiourea to bicyclic scaffolds: highly regio- and stereoselective routes to dithiazolopyrimidines

Microwave-activated solvent-free Michael addition of 3-imino-1,4,2-dithiazoles to 4-arylidene-5(4H)-oxazolones furnished isolable adducts regio- and diastereoselectively, which underwent ring transformation to yield the target dithiazolopyrimidines. Alternatively, the similar conjugate addition of methanesulfinylmethylisothioureas to 4-arylidene-5(4H)-oxazolones diastereoselectively afforded Michael adducts, which underwent ring transformation followed by heterocyclization via deoxygenative demethylation with thionyl chloride to yield the same products dithiazolopyrimidines regio- and diastereoselectively.     

A rapid radioimmunoassay procedure for thyroxin

A sensitive thyroxin /T₄/ radioimmunoassay procedure with a short incubation time /10 min/ similar to a conventional stat test in clinical chemistry is described. The assay parameters such as concentration of antisera and¹²⁵I-T₄, and incubation temperature that affect the kinetics of antigen-antibody reaction have been studied. Within- and between-assay variations were less than 7% CV. Analysis of 45 serum samples by the proposed method and by a conventional assay gave similar results /Y=1.05X–0.187; r=0.990/.     

Nicotinamidoxime as an analytical reagent

Summary Uranium (VI) has been found to give a yellow colour with nicotinamidoxime in alkaline medium which is highly satisfactory for the spectrophotometric estimation of the metal. The optimumph for development of the colour is 10.9–11.5 in presence of a large excess of the reagent, at 10–40C. The colour intensity is measured at 400 m. Sensitivity is 0.045 g uranium per cm², with a visual identification limit of 5 g uranium per ml. Beer's law is obeyed in the range of 5–40 ppm of the metal with an optimum range of 8–40 ppm. The colour is stable for at least one hour. All the common anions are without effect, excepting however, phosphate, carbonate, and cyanide which are tolerated only in traces. Use of tartrate or EDTA helps to mask effectively all the interfering cations excepting copper, iron and vanadium.     

Densities,Ultrasonic Speeds,Viscosities and Refractive Indices of Binary Mixtures of Benzene with Benzyl Alcohol,Benzonitrile, Benzoyl Chloride and Chlorobenzene at 303.15 K

Densities,ρ, ultrasonic speeds, u, viscosities,η, and refractive indices, n, of pure benzene, benzyl alcohol (BA), benzonitrile (BN), benzoyl chloride (BC), chlorobenzene (CB) and their thirty six binary mixtures, with benzene as common component, were measured at 303.15 K over the entire mole fraction range. From these experimental data the values of deviations in ultrasonic speed, △u, isentropic compressibility, △k_s,excess acoustic impedance, Z^E, deviation in viscosity, Dh, and excess Gibbs free energy of activation of viscous flow, G^*E, and partial molar isentropic compressibility, Kφ,2⁰ of BA, BN, BC and CB in benzene were computed. The variation of these derived functions with composition of the mixtures suggested the increased cohesion (molecular order) in the solution and that interaction (A-B)＞(A-A) or (B-B).Moreover, theoretical prediction of ultrasonic speed, viscosity and refractive index of all the four binary mixtures was made on the basis of empirical and semi-empirical relations by using the experimental values of the pure components. Comparison of theoretical results with the experimental values was made in order to assess the suitability of these relations in reproducing the experimental values of u, η and n. Also, molecular radii of pure liquids and the average molecular radii of binary mixtures were evaluated using the corresponding refractive indices of pure liquids and binary mixtures. The average molecular radii of binary mixtures were found to be additive with respect to mole fraction of the pure component.     

Tast polarography of europium(III)-l-histidine complex

Study of europium(III)-l-histidine complex has been made in sodium perchlorate at μ=0.1 by tast polarography. The reduction process appears to be quasi irreversible. The apparent rate constants have been determined byGellings method¹. With the knowledge ofE ₁ ^2/r and use ofLingane's method, one complex Eu(Histd)²⁺ with the instability constant 6.77×10^?5 is reported.