Search results for "Chiral column chromatography"
showing 10 items of 22 documents
Absolute optical chiral analysis using cavity-enhanced polarimetry
2021
Chiral analysis is central for scientific advancement in the fields of chemistry, biology, and medicine. It is also indispensable in the development and quality control of chiral compounds in the chemical and pharmaceutical industries. Current methods for chiral analysis, namely optical polarimetry, mass spectrometry and nuclear magnetic resonance, are either insensitive, have low time resolution, or require preparation steps, and so are unsuited for monitoring chiral dynamics within complex environments: the current need of both research and industry. Here we present the concept of absolute optical chiral analysis, as enabled by cavity-enhanced polarimetry, which allows for accurate unambi…
Enantiomer Separations Using Designed Imprinted Chiral Phases
2003
Total Synthesis of (±)-Oxalicumone C and Chiral Resolution and Elucidation of Its Absolute Configuration
2014
The racemic total synthesis, the chiral resolution, and the elucidation of the absolute configuration of the natural product oxalicumone C were investigated. The goal was achieved by a synthetic strategy beginning with the synthesis of a 5-hydroxy-7-methylchromone precursor. Further modification possibilities were achieved by introduction of a vinyl moiety into the chromone, which was based on a selective iodination step in the 3-position. Further transformations furnished the racemic natural product. To determinate the absolute configuration of naturally occurring oxalicumone C, both enantiomers were separated by chiral HPLC. Comparison of the calculated and experimental vibrational circul…
BONDED SILICA PHASES FOR THE SEPARATION OF BIOPOLYMERS BY MEANS OF COLUMN LIQUID CHROMATOGRAPHY
1988
Is multidimensional high performance liquid chromatography (HPLC) an alternative in protein analysis to 2D gel electrophoresis?
2000
The interactive modes of High Performance Liquid Chromatography (HPLC) of proteins provide a platform for the construction of a multidimensional HPLC system coupled to mass spectrometry. We present a system composed of both anion and cation exchanger columns, in the first dimension, and n-octadecyl bonded 1.5 μm nonporous silica columns in the second dimension. Both columns are operated under gradient conditions. A system suitability test with standard proteins showed that the total analysis can be performed within about 20 minutes. The fractions taken from the ion exchanger column are directly analyzed within one minute on the reversed phase column at a high flow rate. Two reversed phase c…
Phase-distribution chromatography (PDC) of polystyrene
1970
A chromatographic technique is described where the stationary phase is a layer of a very high molecular polystyrene fraction (M = 107) on glass beads (ballotines). The mobile phase is cyclohexane passing the column at a constant temperature below the theta-temperature. A polystyrene sample of sufficiently low molecular weight (M ≤ 106) injected as a small plug at the top of the column is fractionated because the distribution between the mobile and the stationary phase depends on the molecular weight. Since the large molecules preferentially remain in the stationary phase, the smaller molecules leave the column first. The fractionation effect is inverse to that found in GPC experiments. The …
Determination of usnic and perlatolic acids and identification of olivetoric acids in Northern reindeer lichen (Cladonia stellaris) extracts
2010
AbstractThe ecologically important lichen Cladonia stellaris forms thick carpets in boreal forest floors. In addition to affecting temperature and water conditions in the soil underneath, the secondary metabolites formed by the lichen layer are of ecological interest. In this paper, we investigated the distribution of lichen acids in C. stellaris collected at different latitudes in Finland and developed methods to quantify the two optical enantiomers of usnic acid separately. The lichen extracts were analysed by high-performance liquid chromatography (HPLC) with UV and mass spectrometric (MS) detection and by gas chromatography with flame ionization (GC-FID) and MS detection. Usnic acid and…
Strong circularly polarized luminescence of an octahedral chromium(iii) complex
2019
The chiral spin-flip luminophore [Cr(ddpd)2]3+ can be resolved into enantiopure material by chiral HPLC. The corresponding enantiomers show very high luminescence dissymmetry factors of up to ∣glum ∣≈ 0.093 in circularly polarized luminescence (CPL) measurements for the "ruby-like" phosphorescence transition 2E/2T1 → 4A2 in the near-IR region around λ ≈ 775 nm.
Novel σ1 antagonists designed for tumor therapy: Structure – activity relationships of aminoethyl substituted cyclohexanes
2021
Abstract Depending on the substitution pattern and stereochemistry, 1,3-dioxanes 1 with an aminoethyl moiety in 4-position represent potent σ1 receptor antagonists. In order to increase the stability, a cyclohexane ring first replaced the acetalic 1, 3-dioxane ring of 1. A large set of aminoethyl substituted cyclohexane derivatives was prepared in a six-step synthesis. All enantiomers and diastereomers were separated by chiral HPLC at the stage of the primary alcohol 7, and their absolute configuration was determined by CD spectroscopy. Neither the relative nor the absolute configuration had a large impact on the σ1 affinity. The highest σ1 affinity was found for cis-configured benzylamines…
Determination of the enantiomeric composition of amphetamine, methamphetamine and 3,4-methylendioxy-N-methylamphetamine (MDMA) in seized street drug …
2021
Amphetamine (speed), methamphetamine (crystal meth), and 3,4-methylenedioxy-N-methylamphetamine (MDMA, ecstasy) represent the most frequently abused amphetamine-type stimulants (ATS). Differences in pharmacological potency and metabolism have been shown for the enantiomers of all three stimulants. Legal consequences in cases of drug possession may also differ according to the German law depending on the enantiomeric composition of the seized drug. Therefore, enantioselective monitoring of seized specimens is crucial for legal and forensic casework. Various kinds of samples of amphetamine (n = 143), MDMA (n = 94), and methamphetamine (n = 528) that were seized in southern Germany in 2019 and…