A Real-Life Reproducibility Assessment for NMR Metabolomics.

Nuclear magnetic resonance (NMR) metabolomics is currently popular enough to attract both specialized and non-specialized NMR groups involving both analytical trained personnel and newcomers, including undergraduate students. Recent interlaboratory studies performed by established NMR metabolomics groups demonstrated high reproducibility of the state-of-the-art NMR equipment and SOPs. There is, however, no assessment of NMR reproducibility when mixing both analytical experts and newcomers. An interlaboratory assessment of NMR quantitation reproducibility was performed using two NMR instruments belonging to different laboratories and involving several operators with different backgrounds and metabolomics expertise for the purpose of assessing the limiting factors for data reproducibility in a multipurpose NMR environment. The variability induced by the operator, automatic pipettes, NMR tubes and NMR instruments was evaluated in order to assess the limiting factors for quantitation reproducibility. The results estimated the expected reproducibility data in a real-life multipurpose NMR laboratory to a maximum 4% variability, demonstrating that the current NMR equipment and SOPs may compensate some of the operator-induced variability.

Immobilized laccase on a new cryogel carrier and kinetics of two anthraquinone derivatives oxidation.

A coordinatively immobilized laccase was prepared using a new cryogel type carrier. The support has a wide-pore texture facilitating diffusion of different substrates to the enzyme reaction center. The biocatalyst proved to be efficient in decolorization of two anthraquinone derivatives, namely Acid Blue 62 and bromaminic acid. After 24 h over 80% of the two substrates have been oxidated. The kinetic data (K (m) and V (max)) for the oxidation of the two anthraquinone derivatives, with the free and immobilized enzyme, have been determined and compared. Other parameters, like k (cat) and the specificity constant have been calculated and analyzed. The influence of substrate properties (hydrophobicity, polarity, etc.) has been discussed.

The intramolecular asymmetric Pauson-Khand cyclization as a novel and general stereoselective route to benzindene prostacyclins: synthesis of UT-15 (treprostinil).

A general and novel solution to the synthesis of biologically important stable analogues of prostacyclin PGI(2), namely benzindene prostacyclins, has been achieved via the stereoselective intramolecular Pauson-Khand cyclization (PKC). This work illustrates for the first time the synthetic utility and reliability of the asymmetric PKC route for synthesis and subsequent manufacture of a complex drug substance on a multikilogram scale. The synthetic route surmounts issues of individual step stereoselectivity and scalability. The key step in the synthesis involves efficient stereoselection effected in the PKC of a benzoenyne under the agency of the benzylic OTBDMS group, which serves as a temporary stereodirecting group that is conveniently removed via benzylic hydrogenolysis concomitantly with the catalytic hydrogenation of the enone PKC product. Thus the benzylic chiral center dictates the subsequent stereochemistry of the stereogenic centers at three carbon atoms (C(3a), C(9a), and C(1)).

Contribution of chiral HPLC in tandem with polarimetric detection in the determination of absolute configuration by chemical interconversion method: Example in 1-(thi)oxothiazolinyl-3-(thi)oxothiazolinyl toluene atropisomer series.

We report the determination of the absolute configuration of eight stereoisomers in the series of chiral 1-(thi)oxothiazolinyl-3-(thi)oxothiazolinyl toluene atropisomers 1-3, from the known absolute configuration of one stereoisomer, determined by X-ray crystallography. The method uses the affiliation between signs of rotation of polarised light during chemical transformations which preserve the absolute configuration and also during rotation around a single pivot bond producing a compound of known configuration. The use of chiral HPLC in tandem with a chirality detector gives a decisive advantage since such correlation can be performed on a mixture of a very limited quantity of compounds, without tedious purification steps. The method shown as an example in this article, which uses chiral HPLC with chirality detection, may prove useful in many other cases where the determination of the absolute configuration is necessary and where a chemical interconversion method can be used on a microscale.