Characterization and Diagnostic Value of Amino Acid Side Chain Neutral Losses Following Electron-Transfer Dissociation

Using a large set of high mass accuracy and resolution ETD tandem mass spectra, we characterized ETD-induced neutral losses. From these data we deduced the chemical formula for 20 of these losses. Many of them have been previously observed in electron-capture dissociation (ECD) spectra, such as losses of the side chains of arginine, aspartic acid, glutamic acid, glutamine, asparagine, leucine, histidine, and carbamidomethylated cysteine residues. With this information, we examined the diagnostic value of these amino acid-specific losses. Among 1285 peptide–spectrum matches, 92.5% have agreement between neutral loss-derived peptide amino acid composition and the peptide sequences. Moreover, we show that peptides can be uniquely identified by using only the accurate precursor mass and amino acid composition based on neutral losses; the median number of sequence candidates from an accurate mass query is reduced from 21 to 8 by adding side chain loss information. Besides increasing confidence in peptide identification, our findings suggest the potential use of these diagnostic losses in ETD spectra to improve false discovery rate estimation and to enhance the performance of scoring functions in database search algorithms.     

HFO-1234yf as a CF3 Building Block: Synthesis of Trifluoromethyl Quinoline and Chromene Derivatives from Trifluoromethyl-ynones

Trifluoromethyl ynones derived from the refrigerant gas HFO-1234yf (2,3,3,3-tetrafluoropropene) react with nucleophiles via a Michael-type addition process and the allenolate intermediate formed reacts intramolecularly with a carbonyl group to form heterocyclic derivatives. Thus, reaction of 2-amino and 2-hydroxyl benzaldehyde or ketone substrates with trifluoromethyl ynone derivatives gives trifluoromethyl quinoline and chromene products by a one-pot tandem ring closing sequence, forming pharmaceutically relevant structures from an inexpensive starting material without the need for transition metals or column chromatography. The 2-trifluoromethylquinoline products also show unusual fluxional behaviour, which was explored through 2-D NMR and X-ray crystallographic studies.     

Kinetic resolution of racemic pyrrolidine-2,5-diones using chiral oxazaborolidine catalysts

Kinetic resolution of racemic C-3 substituted pyrrolidine-2,5-diones has been achieved for the first time using highly efficient oxazaborolidine catalysts derived from cis-1-amino-indan-2-ol.     

The effect of ethynyl substitution and cyclopenta fusion on the ultraviolet absorption spectra of polycyclic aromatic hydrocarbons

We have examined the UV spectra of six newly-synthesized ethynyl-PAH (1-ethynylnaphthalene, 5-ethynylacenaphthylene, 1-ethynylanthracene, 9-ethynylphenanthrene, 3-ethynylfluoranthene, and 1-ethynylpyrene) and five corresponding CP-PAH (acenaphthylene, aceanthrylene, acephenanthrylene, cyclopenta[cd]fluoranthene, and cyclopenta[cd]pyrene) and have found the following systematic behavior: ethynyl-substitution results in average bathochromic shifts of 5 nm for the lower-wavelength beta- and beta'-bands and of 18 nm for the higher-wavelength p-band, as well as an amplification of the p-band with respect to the beta-band; the addition of a peripheral cyclopenta ring results in average bathochromic shifts of 7 nm in the beta-band, 16 nm in the beta'-band, and 44 nm in the p-band, compared to the wavelengths in the corresponding unsubstituted PAH. The addition of a cyclopenta ring also decreases the resolution of vibrational fine structure in the cases where the fine structure is particularly intense in the spectrum of the unsubstituted PAH. The effects of ethynyl substitution on the UV spectra of PAH are sufficiently consistent that new ethynyl-PAH should be identifiable based on their UV spectra alone.     

Capillary electrophoresis for the analysis of small-molecule pharmaceuticals

This paper reviews the application of CE to the analysis of small-molecule pharmaceuticals. The areas of pharmaceutical analysis covered are enantiomer separation, the analysis of small molecules such as amino acids or drug counter-ions, pharmaceutical assay, determination of related substances and physicochemical measurements such as log P and pK(a) of compounds. The different electrophoretic modes available and their advantages for pharmaceutical analysis are described. Recent applications of CE for each subject area are tabulated with electrolyte details.     

High power (130 mW) 40 GHz 1.55 μm mode-locked distributed Bragg reflector lasers with integrated optical amplifiers

High output power 40 GHz 1.55 μm passively mode-locked surface-etched distributed Bragg reflector (DBR) lasers with monolithically integrated semiconductor optical amplifiers are reported. These are based on an optimized AlGaInAs/InP epitaxial structure with a three quantum well active layer and an optical trap layer. The device produces near transform limited Gaussian pulses with a pulse duration of 3.3 ps. An average output power during mode-locked operation of 130 mW was achieved with a corresponding peak power of >1 W.     

Novel polymers from atom transfer polymerisation mediated by copper(I) Schiff base complexes

The use of copper(I) Schiff base complex catalysed atom transfer polymerisation of methacrylates is described. The use of a range of functional and multi‐functional initiators enables the synthesis of a range of functional and star polymers to be prepared under undemanding synthetic conditions. End capping with silyl enol ethers allows for ω‐functional polymers. The combination of novel initiators, functional monomers and end capping allows an unprecedented array of macromolecular structures to be produced with limited need for protecting group chemistry.