Gas chromatographic/mass spectrometric determination of 3-methoxy-1,2-propanediol and cyclic diglycerols, by-products of technical glycerol, in wine: interlaboratory study

The aim of the present study was to provide the official wine control authorities with an internationally validated method for the determination of 3-methoxy-1,2-propanediol (3-MPD) and cyclic diglycerols (CycDs)-both of which are recognized as impurities of technical glycerol-in different types of wine. Because glycerol gives a sweet flavor to wine and contributes to its full-body taste, an economic incentive is to add glycerol to a wine to mask its poor quality. Furthermore, it is known that glycerol, depending on whether it is produced from triglycerides or petrochemicals, may contain considerable amounts of 3-MPD in the first case or CycDs in the second. However, because these compounds are not natural wine components, it is possible to detect glycerol added to wine illegally by determining the above-mentioned by-products. To this end, one of the published methods was adopted, modified, and tested in a collaborative study. The method is based on gas chromatographic/mass spectrometric analysis of diethyl ether extracts after salting out with potassium carbonate. The interlaboratory study for the determination of 3-MPD and CycDs in wine was performed in 11 laboratories in 4 countries. Wine samples were prepared and sent to participants as 5 blind duplicate test materials and 1 single test material. The concentrations covered ranges of 0.1-0.8 mg/L for 3-MPD and 0.5-1.5 mg/L for CycDs. The precision of the method was within the range predicted by the Horwitz equation. HORRAT values obtained for 3-MPD ranged from 0.8 to 1.7, and those obtained for CycDs ranged from 0.9 to 1.3. Average recoveries were 104 and 109%, respectively.     

A novel solid support for the synthesis of 3-aminoalkylated oligonucleotides

A novel improved controlled pore glass (CPG) support based on the 2-(hydroxymethyl)-6-nitrobenzoyl (HMNB) protecting group was developed for the synthesis of 3^′-aminoalkylated oligonucleotides. The release of oligonucleotides with free 3^′-amino groups from the support is complete within 2 h at 55 °C in concentrated ammonia.     

Diazoniapentaphenes. Synthesis from pyridine‐2‐carboxaldehyde and structural verifications

Reactions of pyridine‐2‐carboxaldehyde (9) with α,α′‐dibromo‐o‐ and p‐xylenes led to the corresponding bis‐pyridinium aldehydes 10 and 14. These aldehydes were quite reactive and the respective hydrates 11 and 15 were also formed. Cyclization of 10 or 11 with 48% HBr led to 12 while cyclization with PPA followed by conversion to the bis tribromide and loss of bromine led to 1. Cyclization of 14 or 15 with 48% HBr led to 3. Attempts to react α,α′‐dibromo‐m‐xylene with pyridine‐2‐carboxaldehyde (9) were not successful for the preparation of the bis‐pyridinium aldehyde 13. The bis‐pyridinium acetals 4, 5 and 6 were prepared and cyclized to afford 1, 2 and 3 , respectively, by the previously reported procedures. The structures of 1 and 2 were verified by ¹H‐NMR and ¹³C‐NMR spectroscopy while that of 3 was confirmed by X‐ray analysis.     

Chloride complexation by heptapeptides: influence of C- and N-terminal sidechains and counterion

The channel-forming diglycolylated heptapeptides containing the amino acid sequence Gly-Gly-Gly-Pro-Gly-Gly-Gly have been found to complex chloride in CDCl(3). The strength of the interaction depends on the terminal alkyl groups and on chloride's countercation.     

Prompt-gamma activation analysis using thek 0 approach

Applying thek ₀ standardization method to prompt-gamma activation analysis (PGAA) offers similar benefits as in instrumental neutron activation analysis. It has been demonstrated that under constant flux conditionsk ₀-factors obtained by normalizing to a titanium comparator, measured separately, yield consistent analytical sensitivity ratios. The ratio method has been generalized by using stoichiometric compounds for the determination ofk ₀-factors. Since chlorine forms compounds with essentially everyelement and it also serves as a detector efficiency standard,k ₀ values have been determined relative to chlorine as an internal standard for several analytically important elements in two reactor facilities: the thermal guided beam at the BRR in Budapest and the cold-neutron beams at the NBSR at NIST.     

Kinetic and mechanistic studies of the reaction of a range of bases and metal-hydroxo complexes with the phosphonate ester 2,4-dinitrophenyl ethyl methylphosphonate in aqueous solution

The base hydrolysis and spontaneous water hydrolysis of the phosphonate ester 2,4-dinitrophenyl ethyl methylphosphonate (DNPEMP) has been studied in detail and the activation parameters for these processes determined. The catalytic effect of a series of 19 oxygen and nitrogen bases and metal hydroxo complexes has been studied. The Brønsted plot of pK versus logkN has a slope (β) of 0.47, which is fairly typical for phosphate and phosphonate esters. alpha-Effect nucleophiles such as 2-iodosobenzoate, hypochlorite and the hydroperoxide ion (HO-2) exhibit enhanced reactivity, as does fluoride ion and the bifunctional metal complex [Cu(tmen) (OH2)(OH)]+ (tmen = N,N,N',N',-tetramethylethylenediamine). Reactions involving these species appear to take place by a nucleophilic pathway, while the other oxygen and nitrogen bases act as general base catalysts. The solvent deuterium isotope effect for Et3N catalysis, kH2O/kD2O=1.3, is consistent with general base catalysis. The mechanisms of these reactions are discussed in detail.     

Synthesis and human leukocyte elastase inhibitory activity of novel 2-spiro(2′,2′-diphenylcyclopropane) cephalosporin sulfones

A new series of 2-spiro(2,2-diphenylcyclopropane) cephalosporin sulfones was synthesizes as potent human leukocyte elastase inhibitors.SynPhar Laboratories Inc., #2 Taiho Alberta Centre, 4290-91A Street, Edmonton, Canada T6R 5V2. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1517–1523, November, 1998.     

Solid-state 109Ag CP/MAS NMR spectroscopy of some diammine silver(I) complexes

Solid-state cross-polarization magic-angle spinning (CP/MAS) NMR spectra were recorded for the compounds [Ag(NH3)2]2SO4, [Ag(NH3)2]2SeO4 and [Ag(NH3))]NO3, all of which contain the linear or nearly linear two-coordinate [Ag(NH3)2]+ ion. The 109Ag CP/MAS NMR spectra show centrebands and associated spinning sideband manifolds typical for systems with moderately large shielding anisotropy, and splittings due to indirect 1J(109Ag,14N) spin-spin coupling. Spinning sideband analysis was used to determine the 109Ag shielding anisotropy and asymmetry parameters Deltasigma and eta from these spectra, yielding anisotropies in the range 1500-1600 ppm and asymmetry parameters in the range 0-0.3. Spectra were also recorded for 15N and (for the selenate) 77Se. In all cases the number of resonances observed is as expected for the crystallographic asymmetric units. The crystal structure of the selenate is reported for the first time. One-bond (107, 109Ag,15N) coupling constants are found to have magnitudes in the range 60-65 Hz. Density functional calculations of the Ag shielding tensor for model systems yield results that are in good agreement with the experimentally determined shielding parameters, and suggest that in the solid compounds Deltasigma and eta are reduced and increased, respectively, from the values calculated for the free [Ag(NH3)2]+ ion (1920 ppm and 0, respectively), primarily as a result of cation-cation interactions, for which there is evidence from the presence of metal-over-metal stacks of [Ag(NH3)2]+ ions in the solid-state structures of these compounds.