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Chiral Gas Chromatography (chiral + gas_chromatography)
Selected AbstractsA new strategy for the synthesis of cyclopeptides containing diaminoglutaric acidJOURNAL OF PEPTIDE SCIENCE, Issue 5 2001Tom Bayer Abstract A new synthesis of orthogonally protected diaminoglutaric acid containing peptides using the Ugi four component condensation is presented. To demonstrate that this method is useful to replace cystine by diaminoglutaric acid in biologically interesting peptides, we built up two cyclic somatostatin analogues deriving from Sandostatin and from TT-232. A photolytically cleavable amine derivative of the nitroveratryl type is used for the Ugi four component condensation. Because of a racemic build up of the new stereocentre of the diaminoglutaric acid, and racemization of the isonitrile component, four diastereomeric peptides resulted that were separated by HPLC. The stereochemistry of the cyclopeptides could be easily and unambiguously assigned by chiral gas chromatography and a reference sample of enantiomerically pure (2S,4S)-diaminoglutaric acid. Copyright © 2001 European Peptide Society and John Wiley & Sons, Ltd. [source] Computational analysis of 1-methoxybicyclo[3.2.0]hepta-3,6-dien-2-one and its enantiomeric separationJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 2 2003Karl Sohlberg Abstract A theoretical analysis of the primary photochemical products of irradiation of ,-tropolone methyl ether is presented. Through this analysis, the fact that only two of the four possible stereoisomers of the product are experimentally observed may be explained. We also present a computational scheme for identifying the enantiomers separated by chiral gas chromatography. Copyright © 2003 John Wiley & Sons, Ltd. [source] Determination of amino acid enantiomers in human urine and blood serum by gas chromatography,mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 3 2001Hans Brückner Amino acid (AA) enantiomers were determined as N(O) -pentafluoropropionyl-(2)-propyl esters by chiral gas chromatography,mass spectrometry (GC-MS) in 24,h samples of the urine of three healthy volunteers and in their blood sera. In urine the largest amounts were determined for D -Ser (64,199,µmol/day) and D -Ala (24,138,µmol/day). In blood sera, D -Ala (2.3,4.2,µmol/L) and D -Ser (1.0,2.9,µmol/L) were most abundant. Varying amounts of the D -enantiomers of Thr, Pro, Asx, Glx, Phe, Tyr, Orn and Lys were also found, albeit not in all urines and sera. Further, enantiomers were quantified in urine samples of two volunteers fasting for 115,h. Quantities of renally excreted D -AAs decreased in fasting, although amounts of D -Ser (69 and 77,µmol/L urine) as well as other D -AAs were still detectable. Time-dependent analyses of urine showed that D -AAs are continuously excreted. Copyright © 2001 John Wiley & Sons, Ltd. [source] Chiral Multidimensional Gas Chromatography (MDGC) and Chiral GC,Olfactometry with a Double-Cool-Strand Interface: Application to MalodorsCHEMISTRY & BIODIVERSITY, Issue 2 2006Frédéric Begnaud Abstract Volatile sulfur compounds such as 3-methyl-3-sulfanylhexan-1-ol (1) are largely responsible for axillary-sweat malodors. In this work, we describe the determination of the enantiomer ratio of the trace constituent 1 and the odor description of its antipodes (R)- and (S)- 1 by means of multidimensional gas chromatography (MDGC) in combination with chiral gas chromatography,olfactometry (GC-O). This technique allowed the on-line evaluation of the sensory character of both enantiomers via a sniffing port, and is based on a novel double-cool-strand interface (DCSI). First, the system's inertness was tested towards the labile compound 2-methylfuran-3-thiol (MFT; 2). Then, the DCSI was used in a new configuration to achieve olfactive characterization by means of chiral GC-O. In contrast to direct smelling after the chiral column, our technique allows, for the first time, to significantly delay the perception of the second-eluting enantiomer after the first one. This lowers the risk of sensory saturation, as the panelist can recover from the first stimulus, before evaluating the second one. To help programming the DCSI, a dedicated program was set up. The enantiomer ratio of the sweat malodor 1 was determined as (S)/(R) 3,:,1, and the dominating (S)-isomer was shown to largely impart its specific character to the overall odor of the sweat extract. [source] | ||||||||||