Synthesis of all diastereomeric methyl 2,5-anhydro-3-deoxy-hexonates: precursors to C-2-deoxynucleosides and THF-templated γ- and δ-amino acids

Efficient syntheses of all diastereomers of methyl 2,5-anhydro-3-deoxy-hexonate from mannono- or gulono-lactones provide precursors for C-nucleosides of 2-deoxyribose and for THF-templated γ- and δ-amino acids.     

Electrochemical behaviour of organotin compounds: Part IV. Phenyltin trichloride

The electrochemical behaviour of phenyltin trichloride has been studied using various electrochemical techniques including polarography, coulometry and cyclic voltammetry. Phenyltin trichloride has been found to show a single major polarographic wave corresponding to a three-electron reduction process to form phenyltin free radicals which rapidly polymerise. Slow hydrolysis of phenyltin trichloride to stannoic acid has been observed to be the major cause of the time-dependence of the limiting current. Analytical methods for the determination of PhSnCl₃ at formulation and trace levels and in the presence of di- and triphenyltin compounds have also been developed.     

Study of the major fragmentation pathways of cypermethrin and related synthetic insecticides using tandem mass spectrometry

Fragmentation pathways of the synthetic pyrethroid cypermethrin and four structurally related insecticides were investigated using a tandem quadrupole mass spectrometer incorporating a hexapole collision cell under positive-ion electron impact ionization conditions. Conventional mass spectrometry using the first quadrupole analyser only and tandem mass spectrometry on selected precursor ions and product ions, and also constant neutral loss scan experiments, were used. Mechanisms and fragmentation pathways are proposed to explain the inherent stability of ions associated with the benzylphenoxy portion of this class of insecticide.     

A specific gas chromatographic detector for carbonyl compounds, based on polarography

The evaluation of a specific gas Chromatographie detector for carbonyl compounds is described. This is based on the polarographic reduction of the Girard T hydrazone derivative which is formed when the carbonyl compound is absorbed in a buffered supporting electrolyte containing the carbonyl reagent. The detector was used to monitor the separation of a homologous series of alkanals.     

Determination of carbonyl compounds via polarography of their semicarbazone derivatives

The polarographic behaviour of a range of aldehyde and ketone semi-carbazones has been studied and a method for the determination of carbonyl compounds developed. The carbonyl compound is added to an acetate buffer containing 0.1 M semicarbazide hydrochloride and 50% ethanol and the polarographic reduction wave of the semicarbazone derivative measured. The similar values of the diffusion current constant I for all compounds studied indicate the applicability of this method to functional group analysis.     

Short and Sweet: D‐Glucose to L‐Glucose and L‐Glucuronic Acid

The scarcity and expense of access to L ‐sugars and other rare sugars have prevented the exploitation of their biological potential; for example D ‐psicose, only recently available, has been recognized as an important new food. Here we give the definitive and cheap synthesis of 99.4% pure L ‐glucose from D ‐glucose which requires purification of neither intermediates nor final product other than extraction into and removal of solvents; a simple crystallization will raise the purity to >99.8%.     

A semi-automated single-cell gradient-titration system, using ion-selective electrodes as end-point sensors

A novel system for semi-automated potentiometric analysis by gradient titration has been devised. In this technique both the reagent gradient generation and the titration are carried out in the sample container. The determination of chloride ion, with two ion-selective electrodes used simultaneously as an end-point sensor, is chosen to illustrate the technique.     

Observed effects of a changing step-edge density on thin-film growth dynamics

We grew SrTiO(3) on SrTiO(3)(001) by pulsed laser deposition, while observing x-ray diffraction at the (00(1/2)) position. The drop DeltaI in the x-ray intensity following a laser pulse contains information about plume-surface interactions. Kinematic theory predicts DeltaI/I = -4sigma(1 - sigma), so that DeltaI /I depends only on the amount of deposited material sigma. In contrast, we observed experimentally that |DeltaI /I| < 4sigma(1 - sigma) and that DeltaI /I depends on the phase of x-ray growth oscillations. The combined results suggest a fast smoothing mechanism that depends on surface step-edge density.     

Modification of Glycosylation as A Therapeutic Strategy

1. INTRODUCTION

Glycoconjugates play important roles in many cellular and physiological processes, including development, differentiation, cell to cell contact, formation of the intracellular matrix, recognition of microorganisms, macromolecules and small molecules and intracellular transport of proteins.^2,3