An unexpected and easy way of freezing the configuration of a triaryl phosphane oxide

Configurationally stable triaryl phosphane oxides are important for reactions with transfer of chiral information. Apart from introducing bulky substituents to suppress fast inversion of helicity at room temperature, the use of a second chiral element which induces chirality in the triaryl phosphane oxide, so that it adopts only one configuration, is suitable. With regard to chirality transfer, C(2)-symmetric imidazole cyclopeptides were tested for obtaining a configurationally stable phosphane oxide. Density functional calculations showed almost equal energies of the three possible triaryl phosphane oxides (MMM)-1, (PPP)-1, and (MP)-1. Surprisingly, after synthesis only the MMM conformer is present in solution, and its configurational stability was proved by variable-temperature and 2D NMR experiments as well as CD measurements. In view of the results of the DFT calculations, formation of stable (MMM)-1 cannot be explained thermodynamically but by kinetic reaction control. This concept of freezing the conformation of a triaryl phosphane oxide can in future be used to easily prepare configurationally stable stereoisomeric propellerlike compounds.     

Molecular cartography in acute Chlamydia pneumoniae infections—a non-targeted metabolomics approach

Infections with Chlamydia pneumoniae cause several respiratory diseases, such as community-acquired pneumonia, bronchitis or sinusitis. Here, we present an integrated non-targeted metabolomics analysis applying ultra-high-resolution mass spectrometry and ultra-performance liquid chromatography mass spectrometry to determine metabolite alterations in C. pneumoniae-infected HEp-2 cells. Most important permutations are elaborated using uni- and multivariate statistical analysis, logD retention time regression and mass defect-based network analysis. Classes of metabolites showing high variations upon infection are lipids, carbohydrates and amino acids. Moreover, we observed several non-annotated compounds as predominantly abundant after infection, which are promising biomarker candidates for drug-target and diagnostic research.     

Discotic liquid crystals: from tailor-made synthesis to plastic electronics

Most associate liquid crystals with their everyday use in laptop computers, mobile phones, digital cameras, and other electronic devices. However, in contrast to their rodlike (calamitic) counterparts, first described in 1907 by Vorl?nder, disklike (discotic, columnar) liquid crystals, which were discovered in 1977 by Chandrasekhar et al., offer further applications as a result of their orientation in the columnar mesophase, making them ideal candidates for molecular wires in various optical and electronic devices such as photocopiers, laser printers, photovoltaic cells, light-emitting diodes, field-effect transistors, and holographic data storage. Beginning with an overview of the various mesophases and characterization methods, this Review will focus on the major classes of columnar mesogens rather than presenting a library of columnar liquid crystals. Emphasis will be given to efficient synthetic procedures, and relevant mesomorphic and physical properties. Finally, some applications and perspectives in materials science and molecular electronics will be discussed.     

New stannide ScAgSn: determination of the superstructure via two-dimensional 45Sc solid state NMR

The new stannide ScAgSn was synthesized by induction melting of the elements in a sealed tantalum tube and subsequent annealing. ScAgSn crystallizes with a pronounced subcell structure: ZrNiAl type, P2m, a = 708.2(2) pm, c = 433.9(1) pm, wR2 = 0.1264, 321 F2 values, and 14 variables. The Guinier powder pattern reveals weak superstructure reflections pointing to a TiFeSi-type structural arrangement: I2cm, a = 708.1(1) pm, b = 1225.2(2) pm, c = 869.9(1) pm, wR2 = 0.0787, 5556 F2 values, and 49 variables. So far the growth of high-quality single crystals failed. Determination of the superstructure was partly based on merohedral triplet X-ray data augmented by 119Sn M?ssbauer spectroscopy and 119Sn and 45Sc solid-state NMR data. In particular, the observation of three crystallographically inequivalent sites in 45Sc NMR triple quantum magic-angle spinning (TQ-MAS) NMR spectra provided unambiguous proof of the superstructure proposed. The ScAgSn structure consists of a three-dimensional [AgSn] network (with Ag-Sn distances between 273 and 280 pm) in which the scandium atoms are located in distorted hexagonal channels, each having five tin and two silver nearest neighbors. Both crystallographically independent tin sites have a tricapped trigonal prismatic coordination, that is, [Sn1Sc6Ag3] and [Sn2Ag6Sc3] environments, which are well distinguished in the 119Sn NMR and M?ssbauer spectra because of their different site symmetries.     

A General Strategy for Targeting Drugs to Bone

Targeting drugs to their desired site of action can increase their safety and efficacy. Bisphosphonates are prototypical examples of drugs targeted to bone. However, bisphosphonate bone affinity is often considered too strong and cannot be significantly modulated without losing activity on the enzymatic target, farnesyl pyrophosphate synthase (FPPS). Furthermore, bisphosphonate bone affinity comes at the expense of very low and variable oral bioavailability. FPPS inhibitors were developed with a monophosphonate as a bone‐affinity tag that confers moderate affinity to bone, which can furthermore be tuned to the desired level, and the relationship between structure and bone affinity was evaluated by using an NMR‐based bone‐binding assay. The concept of targeting drugs to bone with moderate affinity, while retaining oral bioavailability, has broad application to a variety of other bone‐targeted drugs.     

Unterscheidung des ?chten Colonial-Rums vom un?chten sogen. Fa?on-Rum

Ohne Zusammenfassung     

Zur Erkennung und Bestimmung des S?uregehaltes in fetten Oelen

Ohne Zusammenfassung     

Ueber binäre Formen,welche Polaren einer Form sind

Ohne Zusammenfassung     

Determining the enantioselectivity of chiral catalysts by mass spectrometric screening of their racemic forms

The enantioselectivity of a chiral catalyst can be determined from its racemic form by mass spectrometric screening of a nonequal mixture of two mass-labeled quasienantiomeric substrates. The presented method opens up new possibilities for evaluating catalyst structures that are not readily available in enantiomerically pure form.