A General Method Based on the Use of N-Bromosuccinimide for Removal of the Thiophenyl Group at the Anomeric Position to Generate A Reducing Sugar with the Original Protecting Groups Still Present

Abstract

Efficient conversion of a range of different phenyl thioglycosides into their hemiacetals has been achieved by treatment with N-bromosuccinimide in aqueous acetone. The method is mild and general since it does not interfere with the presence of other protecting groups like acetate, benzyl, benzylidene acetal, tert-butyldiphenylsilyl groups, and the O-glycosidic bond (e.g. di-, tetra-, and pentasaccharide thioglycosides).     

Review on multi-scale models of solid-electrolyte interphase formation

Electrolyte reduction products form the solid-electrolyte interphase (SEI) on negative electrodes of lithium-ion batteries. Even though this process practically stabilizes the electrode–electrolyte interface, it results in continued capacity-fade limiting lifetime and safety of lithium-ion batteries. Recent atomistic and continuum theories give new insights into the growth of structures and the transport of ions in the SEI. The diffusion of neutral radicals has emerged as a prominent candidate for the long-term growth mechanism, because it predicts the observed potential dependence of SEI growth.     

Fluorine as a pi donor. Carbon 1s photoelectron spectroscopy and proton affinities of fluorobenzenes

The carbon 1s ionization energies for all of the carbon atoms in 10 fluorine-substituted benzene molecules have been measured by high-resolution photoelectron spectroscopy. A total of 30 ionization energies can be accurately described by an additivity model with four parameters that describe the effect of a fluorine that is ipso, ortho, meta, or para to the site of ionization. A similar additivity relationship describes the enthalpies of protonation. The additivity parameters reflect the role of fluorine as an electron-withdrawing group and as a pi-electron donating group. The ionization energies and proton affinities correlate linearly, but there are four different correlations depending on whether there are 0, 1, 2, or 3 fluorines ortho or para to the site of ionization or protonation. That there are four correlation lines can be understood in terms of the ability of the hydrogens at the site of protonation to act as a pi-electron acceptor. A comparison of the ionization energies and proton affinities, together with the results of electronic structure calculations, gives insight into the effects of fluorine as an electron-withdrawing group and as a pi donor, both in the neutral molecule and in response to an added positive charge.     

l‐Tryptophan formic acid solvate at 183 K

In the title compound, C₁₁H₁₂N₂O₂·CH₂O₂, at 183 K. l ‐­tryptophan appears in the zwitterionic form, while the formic acid molecule is neutral. The formic acid molecule is the donor in a strong O—H?O hydrogen bond to the carboxyl­ate group of the tryptophan mol­ecule, with a short O?O contact of 2.487 (2) Å.     

Uncertainty budget for final assay of a pharmaceutical product based on RP–HPLC

Compliance with specified limits for the content of active substance in a pharmaceutical drug requires knowledge of the uncertainty of the final assay. The uncertainty of measurement is based on the ISO recommendation as expressed in the Guide to the Expression of Uncertainty in Measurement (GUM). The reported example illustrates the estimation of uncertainty for the final determination of a protein concentration by HPLC using UV detection, using the approach described by EURACHEM/CITAC. The combined standard uncertainty for a protein concentration of 2400 µmol/L was estimated to be 14 µmol/L.. All known and potential uncertainty components are presented in Ishikawa diagrams and were carefully evaluated using Type A or Type B estimates. Special efforts were made to avoid duplication or omission of significant contributions to the combined uncertainty. Hence, before accepting the uncertainty budget, the estimated combined standard uncertainty was verified using the variation observed in a number of quality control samples.     

A practical solution approach for the cyclic inventory routing problem

Vendor managed inventory (VMI) is an example of effective cooperation and partnering practices between up- and downstream stages in a supply chain. In VMI, the supplier takes the responsibility for replenishing his customers’ inventories based on their consumption data, with the aim of optimizing the over all distribution and inventory costs throughout the supply chain. This paper discusses the challenging optimization problem that arises in this context, known as the inventory routing problem (IRP). The objective of this IRP problem is to determine a distribution plan that minimizes average distribution and inventory costs without causing any stock-out at the customers. Deterministic constant customer demand rates are assumed and therefore, a long-term cyclical approach is adopted, integrating fleet sizing, vehicle routing, and inventory management. Further, realistic side-constraints such as limited storage capacities, driving time restrictions and constant replenishment intervals are taken into account. A heuristic solution approach is proposed, analyzed and evaluated against a comparable state-of-the-art heuristic.     

Quantum diffusion of light interstitials in metals

A quantum theory of diffusion of self-trapped light interstitials in metals is presented. The theory encompasses both coherent and incoherent tunneling, but the approximation used neglects the dependence of the interstitial transfer matrix element on the vibrational state of the crystal. The coherent tunneling contribution is estimated by fitting the incoherent diffusion rate to experimental data for hydrogen and muon diffusion. It is predicted that coherent diffusion should be dominant below ～ 80 K for H in Nb and below ～ 190 K for μ⁺ in Cu. Experimental verifications of these predictions would require high purity strain free samples and low concentrations of the diffusing species.     

A self-generating third-order electrode: Part II. Analytical applications of the silver—silver sulphide electrode

Analytical applications of the silver—silver sulphide electrode are illustrated by potentiometric determinations of Cd(II) and Pb(II) ions. The stability of the electrode potential in the presence of oxidizing agents is demonstrated by various titrations with silver(I) solutions. The influence of pH on the electrode potential in pure acidic solutions is noted. The electrode used was prepared by electrolytic deposition of silver sulphide on a silver rod; after 2 years, it remained reliable, and was unaffected by light under normal laboratory conditions.