Isonucleosides with Exocyclic Methylene Groups

Synthesis of isonucleosides 13 , 14 , 16 , and 17 , bearing an exocyclic methylidene group at the sugar moiety, starting from a 3‐keto sugar is described. The keto compound was converted to the methylene‐sugar 10b (Scheme 1), which was coupled with nucleobases by means of the Mitsunobu reaction. The coupling reaction with adenine and 8‐azaadenine produced both the N⁹‐ and N³‐nucleosides (see 13 and 14 , resp.; Scheme 2). The structures of 13a and 14a were confirmed by single‐crystal X‐ray data. Synthesis of the pyrimidine compounds was also approached from the β‐amino sugar 20 that was prepared using a Gabriel‐synthesis methodology (Scheme 3).     

Conservatism of the z Confidence Interval Under Symmetric and Asymmetric Departures from Normality

The robustness of the z-interval under nonnormality is investigated by finding its infimum coverage probability over suitably chosen broad class of distributions. In the case of n = 1, the infimum coverage probabilities over the normal scale mixture and the symmetric unimodal families of distributions are obtained analytically. For general n, the infimum problem is theoretically reduced to a finite dimensional minimization which is then obtained numerically. The obtained minimum coverage probabilities are very close to the nominal probabilities. These exact minimum coverage probabilities are often notably sharper than the lower bounds given by the Camp-Meidell-Gauss inequality. The family of general unimodal distributions is considered next to investigate the possible effect of asymmetry. The obtained infimum coverage probabilities over this family are found to be the same as the ones over the symmetric unimodal class.     

Measurement of residual wedge angle with a reversal shear interferometer

A technique for determination of residual wedge angle of high optical quality transparent parallel plate using a reversal shear interferometer-based optical system has been discussed. In this technique the parallel plate to be tested is used to introduce angular tilt in the preset two-beam interference fringes of a reversal shear interferometer. The parallelism is calculated from the angular tilt of the fringes. The technique is more sensitive compared to techniques using Fizeau interferometer and is most suitable for highly parallel transparent plate with very low residual wedge angle.     

Selective and unusual fluoride ion complexation by a steroidal receptor using OH...F- and CH...F- interactions: a new motif for anion coordination?

[structure: see text] A novel cholaphane has been synthesized from a naturally occurring bile acid in just two steps. It has an ability to bind two fluoride ions selectively utilizing the glycolate motif in chloroform. This "inside-out" cyclodextrin analogue encapsulates fluoride through O-H...F(-) and C-H...F(-) interaction.     

Electron impact mass spectra of meliacins

The electron impact mass spectra of some new meliacins and their derivatives are discussed. The major fragmentation modes include the functional group losses, the different ring cleavages and the loss of the furan residue as neutral fragments. A mechanism for the loss of the furan moiety from the molecular ion is discussed in detail with the help of deuterium labelling, high resolution and metastable data.     

Charge transfer complex formation between TX-100/CCl4 reverse micelle and a series of π-electron acceptors: determination of cmc and aggregation number

Electron donor–acceptor interaction of the reverse micelle (RM) of TX-100 in CCl₄ medium with a number of π-acceptors has been established by analysing the charge transfer (CT) absorption bands in the light of Mulliken's theory. Aggregation number (n) and operational critical micellisation concentration of the RM and formation constants of the RM–p-chloranil and RM-o-chloranil complexes have been determined by UV-visible spectrophotometry. Values of n thus obtained (20–30) are close to that of TX-100/cyclohexane dry reverse micelles determined by other methods and also to a theoretically calculated value of n for AOT/CCl₄ dry RM.     

A comparative study on the effects of salt and filler on transport and structural properties of organic–inorganic hybrid electrolytes

Organic–inorganic hybrid electrolytes based on the reaction of tri-block copolymer poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) bis(2-aminopropyl ether), poly(ethylene glycol diglycidyl ether, and (3-glycidyloxypropyl)trimethoxysilane doped with LiClO₄ and SiO₂ nanoparticles were synthesized by a sol–gel process. The structural and dynamic properties of the materials thus obtained were systematically investigated by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, alternate current impedance, and ¹³C solid-state NMR measurements. A maximum ionic conductivity of 3.2?×?10^?5 S cm^?1 was obtained at 30 °C for the solid hybrid electrolyte with a [O]/[Li] ratio of 16 and 7 wt% of SiO₂ nanoparticles. A Vogel–Tamman–Fulcher-like temperature dependence of ionic conductivity was observed for the hybrid electrolytes, implying that the diffusion of charge carriers was assisted by the segmental motions of the polymer chains.     

Effect of Association of Curcumin with Chitosan in Presence of TX 100 on Its Degradation

The binding of curcumin with chitosan in the presence of nonionic surfactant, iso-octylphenoxy-polyethoxy-ethanol (Triton X-100) and its stability in such systems have been investigated by monitoring the changes in the absorption spectra at physiological pH (7.4). It was observed that curcumin binds to chitosan more than 10 times stronger in presence of TX 100 at the experimental condition. From spectrophotometric analysis of the kinetics of degradation of the dye, it was observed that the yield of suppression of degradation of curcumin by chitosan increases by 33.5% in the presence of TX 100 than alone. The interaction of the dye with chitosan has been found to be exothermic and driven by hydrophobic interactions, hydrogen bond formation, and electrostatic interactions.