A study of the analytical behaviour of selected synthetic and naturally occurring coumarins using liquid chromatography, ion trap mass spectrometry, gas chromatography and polarography and the construction of an appropriate database for coumarin characterisation

The aim of this paper is to provide analytical chemical information on a range of naturally occurring and synthetic coumarins. This analytical chemical information on liquid chromatography-electrospray ionisation-mass spectrometry (HPLC-ESI-MS), ion trap mass spectrometry (ESI-MSⁿ), gas chromatography-flame ionisation detection (GLC-FID) and polarographic behaviour is then incorporated into a database which is of use in identifying unknown coumarins isolated from natural sources. This paper is also concerned with understanding the effect of functional groups in coumarins on their analytical chemical behaviour using the above techniques.     

Comparison of FM dye lasers in standing-wave and ring configuration

We have compared the operation of a frequency-modulated dye laser (FML) in a standing-wave and ring configuration. As expected, for a given frequency detuning (difference between the drive frequency for the phase modulator and the cavity mode spacing) the enhanced modulation index is twice as large for the standing-wave configuration as for the ring configuration. In addition, we have demonstrated that application of small amounts of phase modulation in the ring configuration leads to improved mode stability. The fine structure of the rf beats for both FM lasers, have been studied and the results suggest that spatial hole burning complicates the detailed structure.     

A heterocyclic analog of leucine-enkephalin

A series of di-, tri-, tetra- and pentapeptide analogs of leucine-enkephalin have been prepared in which the initial tyrosinylglycine fragment has been replaced by the 5,6-dihydro-5,5-dimethyl-2-oxo-3-phenyl-1(2H)-pyrazineacetic acid moiety.     

The influence of alpha1-acid glycoprotein on collagenase-3 activity in early rheumatoid arthritis

The concentration and glycosylation of alpha(1)-acid glycoprotein (AGP) alter significantly during inflammation. A definitive physiological role for AGP remains elusive and is the subject of extensive investigation. This study investigated the influence of AGP on the activity of collagenase-3, an important mediator of cartilage destruction in rheumatoid arthritis. AGP was isolated from normal and rheumatoid plasma. Fucosylation was determined by high pH anion-exchange chromatography; sialylation was assessed following enzymatic digest. Rheumatoid AGP displayed elevated fucosylation and sialylation compared with normal. The influence of each sample on collagenase-3 activity was measured fluorometrically. AGP influenced collagenase-3 catalysis and collagen binding, with catalytic activity correlating with fucosylation. Rheumatoid AGP exhibited less efficient inhibition than normal plasma AGP. It is hypothesized that AGP within rheumatoid synovial fluid may be inadequate to prevent excessive cartilage destruction and hence may exacerbate the disease process.     

Polyethers derived from bisphenols and highly fluorinated aromatics

A series of fluorinated aromatic polyethers was synthesized via aromatic nucleophilic substitution of highly fluorinated aromatics (1,2,4,5-tetrafluorobenzene, hexafluorobenzene, and decafluorobiphenyl) with bisphenol AF or bisphenol A. Polymerization with 1,2,4,5-tetrafluorobenzene was not observed, and polymerization of hexafluorobenzene with bisphenol proceeded only if the potassium carbonate–bisphenol ratio was carefully controlled. The polymer condensed from decafluorobiphenyl and bisphenol AF was prepared in 77% yield with an inherent viscosity of 1.01 dL/g. The polymer prepared from the condensation of decafluorobiphenyl with bisphenol A was obtained in 48% yield with an inherent viscosity of 0.28 dL/g. These polymers were very soluble in common organic solvents, formed clear, colorless films, and were thermally stable (> 450°C by TGA). The fully fluorinated polymer exhibited low water uptake (0.3%) and dielectric constant (2.17). © 1992 John Wiley & Sons, Inc.     

A ring expansion-annulation strategy for the synthesis of substituted azulenes. Preparation and Suzuki coupling reactions of 1-azulenyl triflates

[structure: see text]. A new strategy for the synthesis of substituted azulenes is reported, based on the reaction of beta'-bromo-alpha-diazo ketones with rhodium carboxylates. The key transformation involves intramolecular addition of a rhodium carbenoid to an arene pi-bond, electrocyclic ring opening, beta-elimination, tautomerization, and trapping to produce 1-hydroxyazulene derivatives. The synthetic utility of the method is enhanced by the ability of the triflate derivatives to participate in Suzuki coupling reactions, as illustrated in a synthesis of the antiulcer drug egualen sodium (KT1-32).