Complete spectroscopic structural characterization of novobiocin,isonovobiocin, decarbamylnovobiocin, 2″-(o-Carbamyl)novobiocin,and novobiocin-2″,3″-carbonate

The rigorous structural characterization of novobiocin, is reported using mass spectrometric, infrared and nmr spectroscopic analysis. Complete nmr assignments are reported. Previous reports in the literature had left some quaternary carbon resonances unassigned. Isonovobiocin and decarbamylnovobiocin, although known in the literature for a number of years, have never been completely characterized. Mass spectrometric fragmentation pathways and complete ¹H and ¹³C nmr assignments are reported for these congeners for the first time. The mass spectral fragmentation pathway and nmr assignments are also reported for 2″-(O-carbamyl)novobiocin although the nmr assignments at lower field were reported previously. The structural characterization of novobiocin-2″,3″-carbonate observed in the Test Assay procedure used for Novobiocin is reported for the first time.     

Two-photon absorption in “double molecules”

The two-photon excited fluorescence excitation spectrum is reported for naphthalene and 2,2-binaphthyl, and for fluorene and difluorenyl. These results are compared with the previously reported results for benzene and biphenyl. The exciton approximation predicts that the two-photon spectra of such single and double molecules should resemble each other quite closely, even in cases where the one-photon spectra are quite different. However, this behaviour is not observed in the reported compounds.     

The International Measurement Evaluation Programme,IMEP-8: carbon and oxygen isotope ratios in CO<Subscript>2</Subscript>

In IMEP-8, two samples of high purity CO(2)(g), with different carbon and oxygen isotope ratios were distributed to 27 participants, originating from 14 countries and from various isotopic measurement domains (geochemistry, atmospheric and food chemistry), but particularly set up for food laboratories. In total 19 laboratories reported results. The outcome of this comparison exercise shows that the laboratories reported carbon and oxygen isotope results in good agreement with the reference values across the domains. The reported results for delta(13)C(VPDB) (carbon) for both materials are within 1 per thousand. However, for the reported results of delta(18)O(VPDB) (oxygen) for both materials the overall spread of the reported results is about 11 per thousand. Within this spread two distinct groups of participants can be identified, where the results within each group vary about 2 per thousand. The latter seems to be caused by calculation errors by participants of the reporting delta(18)O(VPDB) values. As requested, participants also reported the isotope amount ratio for carbon and oxygen in the CO(2) samples. For carbon, all reported results for both materials agree with the isotope ratio value, which can be traced back to the value reported by Craig. For oxygen, all results are in good agreement and deviate by a maximum of 0.5% from the reference values measured at IRMM. Work carried out indicates the carbon isotope ratio, for both samples IMEP-8A and IMEP-8B, differ from those reported by Craig by as much as 1.2%. In the case of oxygen, this deviation is far smaller. Both data sets, i.e. the one realised by Craig and the one realised at IRMM, demonstrate traceability to SI. It is clear that both values significantly disagree.     

On the structure of thromboxane A2

The reactions of the 2-alkoxyoxetane 5 with sodium azide and methanol yield the α-azidoether 7 and the dimethyl acetal 8, respectively, paralleling reactions reported for TXA₂. The hydrolysis of 5 reported by Bruice to involve general acid catalysis proceeds at a rate similar to that reported for TXA₂. All these cleavage reactions are most likely to proceed by the same mechanism. These findings support structure 1 for TXA₂.     

Evaluation and characterization of a commercial zeeman-modulated tungsten-strip electrothermal atomic absorption spectrometer

The operating parameters and the quantitative of an AAZ-2 Zeeman-modulated tungsten-strip atomic absorption spectrometer are reported. The figures of merit for Ag, Au, Cd, Co, Cu, Fe, Mn, Ni, Pb, Tl, and Zn are reported. Detection limits obtained with the AAZ-2 were comparable to those obtained with other metal atomizers reported in the literature. A maximum heating rate of 12 K ms^?1 was measured for the tungsten-strip atomizer.     

Controlled Synthesis of 2‐Acetyl‐6‐carbethoxypyridine and 2,6‐Diacetylpyridine from 2,6‐Dimethylpyridine

The controlled syntheses of mono‐ and bis‐acetylpyridine from the same starting material (2,6‐dimethylpyridine) are reported, including the asymmetrical compound 2‐acetyl‐6‐carbethoxypyridine, which has not before been reported. The influences of the amount of catalyst EtONa and the reaction conditions to the final products are also explored. A modification of the reported preparation for the 2,6‐dipicolinic acid, 2,6‐dicarbethoxypyridine and 2,6‐diacetylpyridine with higher purity and improved yields is provided here, and the physical and spectral properties of these products are identical to those reported in the literature.     

Sugar composition of the moss Rhodobryum ontariense (Kindb.) Kindb

Although the second biggest terrestrial group of plants, bryophytes remain poorly known chemically compared to the angiosperms. In this article, the sugars of the moss Rhodobryum ontariense, an unstudied representative of the medicinally known genus, are reported. The chemical analysis revealed the usual plant sugar sucrose, and a new sugar, fructooligosaccharide 1-kestose, which is reported first not only for the genus Rhodobryum, but also for mosses. The trisaccharides have been scantily reported in bryophytes hitherto. This gives more significance to this study for further investigation of its role in the moss species. The health-promoting effect of 1-kestose is also briefly discussed.     

The isomers of HF-HCN formed in helium nanodroplets: Infrared spectroscopy and ab initio calculations

Binary complexes containing hydrogen cyanide and hydrogen fluoride are formed in helium nanodroplets, and studied using high-resolution infrared laser spectroscopy. Rotationally resolved spectra are reported for the H-F and C-H stretches of the linear HCN-HF complex, a system that has been thoroughly studied in the gas phase. We report the high-resolution spectra of the higher energy, bent HF-HCN isomer, which is also formed in helium. Stark spectra are reported for both isomers, providing dipole moments of these complexes. The experimental results are compared with ab initio calculations, also reported here. Spectra are reported for several ternary complexes, including (HCN)2-HF, HCN-(HF)2, HF-(HCN)2, and HF-HCN-HF.     

The mass spectra of some selenoureas and selenothiocarbamic esters

The mass spectra of five selenoureas and two selenothiocarbamic esters are reported and discussed. Fragmentation modes are compared with those reported for the ureas, thioureas, carbamates and thiocarbamates.     

The interlaboratory comparison "IMEP-19 trace elements in rice"—a new approach for measurement performance evaluation

The aim of IMEP is to present objectively the quality of chemical measurements. Participants in IMEP compare their reported measurement results with independent external certified reference values with demonstrated traceability and uncertainty, as evaluated according to international guidelines. IMEP-19 focused on measurements of trace elements in rice aiming to support the Commission Regulation (EC) No. 466/2001 on maximum levels for certain contaminants in foodstuff. Measurement results for the elements Cd, Cu, Pb and Zn were reported by 267 field laboratories involved in food analysis from 43 countries. Performance criteria for the evaluation of the reported measurement results in IMEP-19 are suggested. The chosen performance indicators not only take into account the deviation of the reported measurement value from the certified reference value, but also set criteria for maximum and minimum acceptable uncertainty. The IMEP-19 participants' performance is reviewed by means of using new simple graphical tools, called "Naji plots".     

Isolierung und Aminosäuresequenz von Substanz P aus Pferdedarm

The isolation and amino acid sequence of substance P from horse intestine is reported. The sequence, H-Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH₂ is identical with the sequence reported for substance P isolated from bovine hypothalami.     

Carbon-13 nuclear magnetic resonance studies on dichloropyridoquinolines

Carbon-13 NMR chemical shifts are reported for six angular and one linear dichloropyridoquinolines in CDCl₃. The chemical shift assignments have been made using model compounds, fully coupled spectra, selective proton decoupling and results from lanthanide shift studies. Chlorine substituent effects are compared to those reported for chloroquinolines. The effect of the heteroaromatic nitrogen atoms on ¹³C? ¹H coupling constants in these polycyclic systems are compared to those reported for pyridine systems.     

Model studies for the synthesis of the antibiotic lactonamycin and the discovery of new reactions and mechanisms for the construction of substituted heterocycles

A new and highly efficient route for the construction of a model for the synthesis of lactonamycin 1 is reported. The chemistry has been utilised for the synthesis of heterocyclic rings, and new reactions for the synthesis of dienes and alkynes are reported.     

Vapor–liquid equilibria and excess volumes of the binary systems ethanol + ethyl lactate, isopropanol + isopropyl lactate and n-butanol + n-butyl lactate at 101.325 kPa

Isobaric vapor–liquid equilibrium data have been experimentally determined at 101.3 kPa for the binary systems ethanol + ethyl lactate, isopropanol + isopropyl lactate and n-butanol + n-butyl lactate. No azeotrope was found in any of the systems. All the experimental data reported were thermodynamically consistent according to the point-to-point method of Fredenslund. The activity coefficients were correlated with the NRTL and UNIQUAC liquid-phase equations and the corresponding binary interaction parameters are reported. The densities and derived excess volumes for the three mixtures are also reported at 298.15 K.     

SOME PHOTOPHYSICAL PROPERTIES OF 3-CARBETHOXYPSORALEN, 8-METHOXYPSORALEN and 5-METHOXYPSORALEN TRIPLET STATES

Abstract Triplet absorption spectra, extinction coefficients (ɛ_T), decay rates ( K ₁), oxygen quenching rates (k_q) and intersystem crossing yields (φ_T) for 3-carbethoxypsoralen (3-CPs). 8-methoxypsoralcn (8-MOP) and 5-methoxypsoralen (5-MOP) in methanol are reported. For 8-MOP and 3-CPs corresponding values are also reported with water as the solvent. Some photophysical data are also reported for 5-MOP in water, but ɛ_T and φ_T were not obtained.
The phosphorescence spectra for these furocoumarin derivatives in ethanol at 77 K are reported together with the corresponding lowest triplet energy and lifetime. The values of the various photophysical properties obtained are compared with values reported by previous workers.     

CCC-N-heterocyclic carbene pincer complexes: Synthesis, characterization and hydroamination activity of a hafnium complex

Our methodology for the stoichiometric preparation of CCC-NHC pincer complexes of Zr has been extended to Hf. The CCC^Bu-NHC pincer Hf complex has been characterized by X-ray crystal structure analysis. Catalytic activity in the intramolecular hydroamination/cyclization of unactivated alkenes is reported and compared to the recently reported Zr analog. An improved, scaled-up CuO-catalyzed aryl amination of 1,3-dibromobenzene and an improved salt formation methodology for preparation of bis(butyl-imidazolium)benzene are reported also.     

Miniature toroidal radio frequency ion trap mass analyzer

A miniature ion trap mass analyzer is reported. The described analyzer is a 1/5-scale version of a previously reported toroidal radio frequency (rf) ion trap mass analyzer. The toroidal ion trap operates with maximum rf trapping voltages about 1 kVp-p or less; however despite the reduced dimensions, it retains roughly the same ion trapping capacity as conventional 3D quadrupole ion traps. The curved geometry provides for a compact mass analyzer. Unit-mass resolved mass spectra for n-butylbenzene, xenon, and naphthalene are reported and preliminary sensitivity data are shown for naphthalene. The expected linear mass scale with rf amplitude scan is obtained when scanned using a conventional mass-selective instability scan mode combined with resonance ejection.     

Room-temperature fluorescence spectrometry of some pharmaceutical compounds

Room-temperature fluorescence of 66 pharmaceutical drugs are presented using a mixture of ethanol/water as solvent. The analytical figures of merit for the fluorescent species are reported with limits of detection ranging between 1 and 30 ng/ml for most of them and with average blank standard deviation of 7.6%. The spectral band half-widths are also reported.     

Solubility of Ketoconazole in Polyethylene Glycol 200 + Water Mixtures at 298.2–318.2 K

The solubility of ketoconazole in binary mixtures of polyethylene glycol 200 (PEG 200) + water is reported at temperatures ranging from 298.2 to 318.2 K. The Jouyban–Acree model and its combined version including the van’t Hoff equation were used for correlating the reported data; the obtained mean relative deviations are 9.5 and 9.9 %, respectively. Also, two previously trained versions of the Jouyban–Acree model were used for predicting the reported data points in which the prediction errors were 34.6 and 31.0 %.     

Chemistry of the phenoxathiins II. Synthesis of 1-azaphenoxathiin

The synthesis of 1-azaphenoxathiin, the parent ring system of a recently reported class of novel CNS agents is described. The ¹³C-nmr spectrum and its assignment are also reported as a model for structure confirmation studies.